PDGFB

Gene Summary

Gene:PDGFB; platelet derived growth factor subunit B
Aliases: SIS, SSV, IBGC5, PDGF2, c-sis, PDGF-2
Location:22q13.1
Summary:This gene encodes a member of the protein family comprised of both platelet-derived growth factors (PDGF) and vascular endothelial growth factors (VEGF). The encoded preproprotein is proteolytically processed to generate platelet-derived growth factor subunit B, which can homodimerize, or alternatively, heterodimerize with the related platelet-derived growth factor subunit A. These proteins bind and activate PDGF receptor tyrosine kinases, which play a role in a wide range of developmental processes. Mutations in this gene are associated with meningioma. Reciprocal translocations between chromosomes 22 and 17, at sites where this gene and that for collagen type 1, alpha 1 are located, are associated with dermatofibrosarcoma protuberans, a rare skin tumor. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Oct 2015]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:platelet-derived growth factor subunit B
Source:NCBIAccessed: 13 March, 2017

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 13 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 13 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: PDGFB (cancer-related)

Stubbs C, Bardoli AD, Afshar M, et al.
A Study of Angiogenesis Markers in Patients with Renal Cell Carcinoma Undergoing Therapy with Sunitinib.
Anticancer Res. 2017; 37(1):253-259 [PubMed] Related Publications
BACKGROUND: Sunitinib is a tyrosine kinase inhibitor (TKI) targeting tumour angiogenesis in patients with advanced renal cell carcinoma (RCC). Currently no universally agreed model exists correlating the expression of angiogenesis markers with the success of treatment.
PATIENTS AND METHODS: We retrospectively analysed archival tissue for 59 RCC patients treated with sunitinib. The expression of angiogenesis markers VEGF-A, VEGFR, PDGFββ, PDGFR, CCND1 and CA9 was assessed by immunohistochemistry (IHC) and correlated with overall survival (OS) and progression-free survival (PFS).
RESULTS: The median OS and median PFS of the whole group of patients was 24.6 months (17.3-34.2) and 19.5 months (11-27) respectively. VEGFA was positive in 29% of tumors, whereas VEGFR was expressed in only 12% of tumours. PDGFββ and its receptor were detected in a minority of cases. CCND1 and CA9 were positive in 44% and 60% of cases.
CONCLUSION: The OS and PFS achieved by our patients reflected previous observations seen with sunitinib, but no correlation was found between expression of angiogenesis markers and clinical outcome.

Cimpean AM, Cobec IM, Ceaușu RA, et al.
Platelet Derived Growth Factor BB: A "Must-have" Therapeutic Target "Redivivus" in Ovarian Cancer.
Cancer Genomics Proteomics. 2016 11-12; 13(6):511-517 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: We aimed to validate PDGF-BB protein expression by RNAscope, a sensitive method for PDGF-BB mRNA evaluation on paraffin embedded (FFPE) specimens of ovarian tumors.
MATERIALS AND METHODS: Seventy-five FFPE ovarian cancer biopsies were assessed by immunohistochemistry followed by PDGF-BB mRNA RNAscope validation.
RESULTS AND CONCLUSION: Dual PDGF-BB expression in tumor and stromal cells have been observed, being highly suggestive for PDGF-BB mediated stromal-tumor cells reciprocal interaction in ovarian cancer (p=0.008). It seems that the nuclear expression of the PDGF-BB represents a negative prognostic factor in ovarian tumors. Being a controversial issue in the literature, PDGF-BB nuclear expression detected by immunohistochemistry was validated by RNAscope in situ hybridization. More than 65% of cases had PDGF-BB mRNA amplification, confirming immunohistochemical results. We herein validated PDGF-BB as a potential therapeutic and prognostic tool of ovarian cancer aggressiveness.

Thway K, Noujaim J, Jones RL, Fisher C
Dermatofibrosarcoma protuberans: pathology, genetics, and potential therapeutic strategies.
Ann Diagn Pathol. 2016; 25:64-71 [PubMed] Related Publications
Dermatofibrosarcoma protuberans (DFSP), the most common dermal sarcoma, is a malignant fibroblastic tumor most frequently arising in middle-aged adults. It is typically a low-grade sarcoma that grows slowly but has a high rate of local recurrence with low metastatic potential. Dermatofibrosarcoma protuberans is characterized by a specific translocation t(17;22)(q22;q13) leading to the formation of COL1A1-PDGFB fusion transcripts. Histologically, DFSP has characteristic morphology, of storiform islands of bland spindle cells, and immunohistochemically, it shows diffuse expression of CD34. However, the morphology and immunoprofile can overlap with a variety of other soft tissue neoplasms. The preferred management of localized disease is wide surgical resection or Mohs micrographic surgery, whereas radiotherapy may be used for margin-positive disease where reexcision is not possible, or for inoperable disease. Dermatofibrosarcoma protuberans is generally regarded as refractory to conventional chemotherapy. Treatment options for systemic disease have been previously limited, but the PDGFβR, KIT, and ABL inhibitor imatinib is now an option for effective systemic therapy. Continued insight into the tumorigenic molecular changes generated by the fusion oncogene may lead to further specific targeted treatments. We review DFSP, discussing the morphologic spectrum and variants, immunohistochemistry, molecular genetic findings, potential targeted treatments, and the differential diagnosis.

Cimpean AM, Raica M
The Hidden Side of Disodium Cromolyn: from Mast Cell Stabilizer to an Angiogenic Factor and Antitumor Agent.
Arch Immunol Ther Exp (Warsz). 2016; 64(6):515-522 [PubMed] Related Publications
Scattered data suggested that disodium cromolyn, well known as a mast cell stabilizer shows some effects on tumor cells and tumor-associated newly formed vascular networks. Most of these studies used tumor cell lines assessed by in vitro studies. Nor disodium cromolyn effects on melanoma cell lines were studied yet, neither its influence on recruited tumor blood vessels or angiogenic growth factors expression. We designed here a study regarding disodium cromolyn effects on A375 melanoma tumor cells implanted on chick embryo chorioallantoic membrane (CAM) and on blood vessels recruited by the experimental melanoma in the absence of mast cells, knowing that within CAM, the existence of mast cells are not certified yet. We also assessed the role of disodium cromolyn on the expression of several angiogenic growth factors. Disodium cromoglycate differentially acts on tumor cells and blood vessels. Extensive necrotic areas of experimental melanoma together with an increased number of peritumor blood vessels were observed in treated specimens as compared with untreated tumors. Disodium cromolyn inhibited VEGF and PDGF-BB expression, and had no effects on EG VEGF expression between treated and non treated specimens in a mast cells free microenvironment. Our results sustain the direct antitumor effects of sodium cromolyn and suggest the involvement of several growth factors in the recruitment of tumor vessels by A375 melanoma tumor cells. The expression of growth factors is differentially influenced by sodium cromolyn treatment.

Eiro N, Fernandez-Gomez J, Sacristán R, et al.
Stromal factors involved in human prostate cancer development, progression and castration resistance.
J Cancer Res Clin Oncol. 2017; 143(2):351-359 [PubMed] Related Publications
PURPOSE: To detect new predictive markers from the prostate cancer tissue, to study the expression by cultured cancer-associated fibroblasts (CAFs) of stromal factors implicated in prostate carcinogenesis, and to compare their expressions in localized, metastatic, castration-sensitive (CSCP), castration-resistant prostate tumors (CRCP) as well as in fibroblasts from benign prostatic hyperplasia (BPH).
MATERIALS AND METHODS: The genomic expression of 20 stroma-derived factors, including the androgen receptor (AR), growth factors (FGF2, FGF7, FGF10, HGF, TGFβ, PDGFB), protein implicated in invasion (MMP-2, MMP-9 and MMP-11), inflammation (IL-6, IL-17, STAT-3 and NFκB), stroma/epithelium interaction (CDH11, FAP, CXCL12 and CXCL14) and chaperones (HPA1A and HSF1), was evaluated in cultured fibroblasts both from BHP and prostate carcinomas (PCa). After isolation and culture of fibroblasts by biopsy specimens, RNA was isolated and genomic studies performed.
RESULTS: Finally, 5 BPH and 37 PCa specimens were selected: clinically localized (19), metastatic (5), CSCP (7) and CRPC (6). Interleukin-17 receptor (IL-17RB) was highly expressed in CAFs compared with fibroblasts from BPH. However, metalloproteinase-2 and chemokine ligand 14 (CXCL14) were expressed at higher levels by fibroblasts from BPH. The fibroblastic growth factor-7 was highly expressed by CAFs from localized tumors, but metalloproteinase-11 in metastatic tumors. MMP-11, androgen receptor (AR) and heat-shock-70kda-protein-1A (HSPA1A) expressions were significantly higher in CAFs from CRPC.
CONCLUSIONS: These results demonstrate a CAFs heterogeneity among prostate carcinomas with regard to some molecular profile expressions that may be relevant in tumor development (IL-17RB), progression (MMP-11) and castration resistance (AR, MMP-11 and HSPA1A).

Lee J, Katzenmaier EM, Kopitz J, Gebert J
Reconstitution of TGFBR2 in HCT116 colorectal cancer cells causes increased LFNG expression and enhanced N-acetyl-d-glucosamine incorporation into Notch1.
Cell Signal. 2016; 28(8):1105-13 [PubMed] Related Publications
Transforming growth factor-β (TGF-β) signaling plays a key role in regulating normal cell growth and differentiation, and mutations affecting members of this pathway contribute to cancer development and metastasis. In DNA mismatch repair (MMR)-deficient colorectal cancers that exhibit the microsatellite instability (MSI) phenotype, biallelic frameshift mutations in the transforming growth factor β receptor type 2 (TGFBR2) gene occur at high frequency that lead to altered signal transduction and downstream target gene expression. Although recent evidence suggests that altered TGF-β signaling can modulate protein glycosylation patterns in MSI-high colorectal tumor cells, affected genes have not been identified. Here, we investigated in a more systematic approach, expression changes of TGFBR2-regulated genes, involved in glycosylation using a TGFBR2-reconstituted colorectal cancer cell line (HCT116-TGFBR2) and Glyco-Gene Chip analysis. Based on this oligonucleotide array of about 1000 human glycosylation-related genes, several candidates including HES1, PDGFB, JUNB and LFNG were found to be upregulated in a TGFBR2-dependent manner and subsequently validated by real-time RT-PCR analyses. Focusing on the glycosyltransferase LFNG and its target signaling protein Notch1, dual labeling with [3H]-N-acetyl-d-glucosamine ([3H]-GlcNAc) and [35S]-l-methionine revealed a significant increase in N-acetyl-d-glucosamine incorporation into immunoprecipitated Notch1 receptor upon TGFBR2 expression whereas the protein level remained unaffected. These data suggest that TGFBR2 signaling can affect Notch1 glycosylation via regulation of glycosyltransferase LFNG expression and provide a first mechanistic example for altered glycosylation in MSI colorectal tumor cells.

Cumpănas AA, Cimpean AM, Ferician O, et al.
The Involvement of PDGF-B/PDGFRβ Axis in the Resistance to Antiangiogenic and Antivascular Therapy in Renal Cancer.
Anticancer Res. 2016; 36(5):2291-5 [PubMed] Related Publications
BACKGROUND/AIM: Studies developed in the field of platelet-derived growth factors/platelet-derived growth factor receptors (PDGFs/PDGFRs) inhibition have focused on the therapeutic effects on tumor cells, neglecting their potential effects on tumor blood vessels. We herein propose a differential and critic assessment of platelet-derived growth factor B (PDGF-B) and platelet-derived growth factor receptor β (PDGFRβ) in renal cell carcinoma, correlated with the four main vascular patterns previously reported by our team.
MATERIALS AND METHODS: PDGF-B and PDGFRβ were evaluated on 50 archival paraffin embedded specimens related to vascular endothelial growth factor (VEGF), its inhibitory isoform VEGF165b and vascular patterns.
RESULTS AND CONCLUSION: Our results support the involvement of VEGF165b in the phosphorylation of PDGFRβ with an inhibitory effect on endothelial proliferation and migration. The simultaneous action of PDGF-B/PDGFRβ and VEGF165b on the same type of receptor may explain the resistance to antiangiogenic therapy, which depends on the degree of modulation of PDGFRβ phosphorylation.

Makino M, Sasaoka S, Nakanishi G, et al.
Congenital atrophic dermatofibrosarcoma protuberans detected by COL1A1-PDGFB rearrangement.
Diagn Pathol. 2016; 11:24 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Atrophic variant of dermatofibrosarcoma protuberans (DFSP) is a distinct form of DFSP.
CASE PRESENTATION: Here, we report the case of a 19-year-old woman with a small congenital atrophic plaque on the right precordium. The lesion remained atrophic for more than 10 years. Several years earlier, a portion of the plaque became tuberous and enlarged. Physical examination revealed a 25 × 30 mm erythematous atrophic plaque surrounded by three hard, smooth, and orange-colored nodules of varying sizes on the right precordium, along with visible subcutaneous adipose tissue and cutaneous veins. Biopsy of the nodule and atrophic plaque revealed dense proliferation of spindle-shaped tumor cells from the dermis to the subcutaneous adipose tissue, and positive immunostaining for CD34 and vimentin in addition to negative staining for factor XIIIa and α-smooth muscle actin. Reverse transcription polymerase chain reaction (RT-PCR) of the tumor tissue revealed the presence of a COL1A1-PDGFB fusion gene. Thus, congenital atrophic dermatofibrosarcoma protuberans was diagnosed. No metastasis to the lungs or regional lymph nodes was found on magnetic resonance imaging. Wide local excision and split-thickness skin grafting was performed and neither recurrence nor metastasis has been observed for 5 years and 8 months since the surgery.
CONCLUSION: This case indicates that a congenital atrophic lesion could represent a quiescent phase of DFSP. Awareness of this rare condition can aid with early diagnosis and thereby improve the prognosis of DFSP.

Okamoto S, Nitta M, Maruyama T, et al.
Bevacizumab changes vascular structure and modulates the expression of angiogenic factors in recurrent malignant gliomas.
Brain Tumor Pathol. 2016; 33(2):129-36 [PubMed] Related Publications
Bevacizumab (BV), a monoclonal antibody against vascular endothelial growth factor (VEGF), is currently used in the treatment of malignant glioma. To understand mechanisms of resistance to BV, we investigated morphological changes in tumor vessels and expression of angiogenic factors, such as VEGF, Flt-1, basic fibroblast growth factor (bFGF), and platelet-derived growth factor-BB (PDGF-BB), in four autopsied tumors after BV treatment. Three patients had glioblastomas; the fourth had a secondary glioblastoma that developed from a diffuse astrocytoma. BV was administered because of recurrence following the use of the Stupp regimen in these four patients. We compared the initial surgical specimen with that obtained after death following BV treatment. Immunohistochemical staining of the autopsied tumors showed that Flt-1 expression increased while VEGF expression was significantly reduced. Additionally, other angiogenic factors, particularly bFGF, were enhanced. Interestingly, the proliferation of endothelial cells was reduced, but remarkable proliferation of pericytes was observed. These results suggest that following BV treatment, glioblastomas can grow tumor vessels by expressing various angiogenic factors. These mechanisms might be important for rapid regrowth and blood brain barrier repair after BV treatment. Inhibition of multiple angiogenic factors will be required to control tumor vessels in glioblastoma.

Li L, Yu J, Duan Z, Dang HX
The effect of NFATc1 on vascular generation and the possible underlying mechanism in epithelial ovarian carcinoma.
Int J Oncol. 2016; 48(4):1457-66 [PubMed] Related Publications
We investigated the effect of nuclear factor of activated T cells c1 (NFATc1) on the growth and vascular generation of human ovarian carcinoma SKOV3 cell-transplanted tumors in nude mice and explored the possible underlying mechanism. NFATc1 siRNA was transfected into the SKOV3 cells, which were then subjected to immunofluorescence tests and real-time reverse transcription polymerase chain reaction (RT-PCR) to determine the transfection-induced inhibition rate. The tumor volumes in the nude mice in all groups were measured to determine the in vivo antitumor effect of NFATc1 siRNA. Immunohistochemical (IHC) methods were employed to detect NFATc1 expression in tumor tissue, combined with cytokeratin (CK) staining to label the epithelial origin of the tumor tissue. CD34 and podoplanin were used as markers for labeling microvessels and microlymphatic vessels, respectively. The densities of microvessels and microlymphatic vessels in each group were calculated and statistically analyzed. RT-PCR and western blotting were performed to detect the protein and mRNA expression levels of NFATc1, the ELR+ CXC chemokine interleukin (IL)-8, fibroblast growth factor-2 (FGF-2), and platelet-derived growth factor BB (PDGF BB) in xenografted tumor tissue in all groups. NFATc1 was highly expressed in tumor tissue in the control groups. The intervention group exhibited a tumor growth inhibition rate of 57.08% and presented a lower tumor weight and volume compared with the two control groups. In the control groups, the microvessel densities were 12.00 ± 1.65 and 11.47 ± 0.32, respectively, and the microlymphatic vessel densities were 10.03 ± 0.96 and 9.95 ± 1.12; these values were significantly higher than in the intervention group. RT-PCR and western blot shows that NFATc1 siRNA could markedly suppress the expression of IL-8, FGF-2 and PDGF BB at the mRNA and the protein level. In conclusion, it was shown that NFATc1 siRNA significantly suppresses the growth and vascular generation of SKOV3 human ovarian carcinoma cell-transplanted tumors subcutaneously xenografted into nude mice. The downregulation of the expression of IL-8, FGF-2 and PDGF BB may be one of the mechanisms underlying the above inhibitory effects.

Mertens F, Antonescu CR, Mitelman F
Gene fusions in soft tissue tumors: Recurrent and overlapping pathogenetic themes.
Genes Chromosomes Cancer. 2016; 55(4):291-310 [PubMed] Free Access to Full Article Related Publications
Gene fusions have been described in approximately one-third of soft tissue tumors (STT); of the 142 different fusions that have been reported, more than half are recurrent in the same histologic subtype. These gene fusions constitute pivotal driver mutations, and detailed studies of their cellular effects have provided important knowledge about pathogenetic mechanisms in STT. Furthermore, most fusions are strongly associated with a particular histotype, serving as ideal molecular diagnostic markers. In recent years, it has also become apparent that some chimeric proteins, directly or indirectly, constitute excellent treatment targets, making the detection of gene fusions in STT ever more important. Indeed, pharmacological treatment of STT displaying fusions that activate protein kinases, such as ALK and ROS1, or growth factors, such as PDGFB, is already in clinical use. However, the vast majority (52/78) of recurrent gene fusions create structurally altered and/or deregulated transcription factors, and a small but growing subset develops through rearranged chromatin regulators. The present review provides an overview of the spectrum of currently recognized gene fusions in STT, and, on the basis of the protein class involved, the mechanisms by which they exert their oncogenic effect are discussed.

Giachino C, Boulay JL, Ivanek R, et al.
A Tumor Suppressor Function for Notch Signaling in Forebrain Tumor Subtypes.
Cancer Cell. 2015; 28(6):730-42 [PubMed] Related Publications
In the brain, Notch signaling maintains normal neural stem cells, but also brain cancer stem cells, indicating an oncogenic role. Here, we identify an unexpected tumor suppressor function for Notch in forebrain tumor subtypes. Genetic inactivation of RBP-Jκ, a key Notch mediator, or Notch1 and Notch2 receptors accelerates PDGF-driven glioma growth in mice. Conversely, genetic activation of the Notch pathway reduces glioma growth and increases survival. In humans, high Notch activity strongly correlates with distinct glioma subtypes, increased patient survival, and lower tumor grade. Additionally, simultaneous inactivation of RBP-Jκ and p53 induces primitive neuroectodermal-like tumors in mice. Hence, Notch signaling cooperates with p53 to restrict cell proliferation and tumor growth in mouse models of human brain tumors.

Lindhurst MJ, Yourick MR, Yu Y, et al.
Repression of AKT signaling by ARQ 092 in cells and tissues from patients with Proteus syndrome.
Sci Rep. 2015; 5:17162 [PubMed] Free Access to Full Article Related Publications
A somatic activating mutation in AKT1, c.49G>A, pGlu17Lys, that results in elevated AKT signaling in mutation-positive cells, is responsible for the mosaic overgrowth condition, Proteus syndrome. ARQ 092 is an allosteric pan-AKT inhibitor under development for treatment in cancer. We tested the efficacy of this drug for suppressing AKT signaling in cells and tissues from patients with Proteus syndrome. ARQ 092 reduced phosphorylation of AKT and downstream targets of AKT in a concentration-dependent manner in as little as two hours. While AKT signaling was suppressed with ARQ 092 treatment, cells retained their ability to respond to growth factor stimulation by increasing pAKT levels proportionally to untreated cells. At concentrations sufficient to decrease AKT signaling, little reduction in cell viability was seen. These results indicate that ARQ 092 can suppress AKT signaling and warrants further development as a therapeutic option for patients with Proteus syndrome.

Wu Z, Liu J, Wang J, Zhang F
SOX18 knockdown suppresses the proliferation and metastasis, and induces the apoptosis of osteosarcoma cells.
Mol Med Rep. 2016; 13(1):497-504 [PubMed] Related Publications
Sex determining region Y‑box 18 (SOX18) has been found to be overexpressed in several types of tumor. However, the molecular mechanism underlying the biological function of SOX18 in osteosarcoma remains to be elucidated. The present study aimed to elucidate the roles of SOX18 in regulating the biological behavior of osteosarcoma cells. First, SOX18 mRNA expression was analyzed in osteosarcoma tissues using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). The results demonstrated that the expression of SOX18 was elevated in osteosarcoma tissue, compared with normal bone tissue. In addition, the knockdown of SOX18 in U2OS or MG63 osteosarcoma cells inhibited cell proliferation and significantly increased the population of cells in the S‑phase of the cell cycle, as measured by the CCK‑8 assay and flow cytometric analysis, respectively. Additionally, suppression of the expression of SOX18 in the osteosarcoma cells significantly induced cell apoptosis as evaluated by annexin V/propidium iodide staining and flow cytometric analysis. The downregulation of SOX18 was found to significantly inhibit cell adhesion and invasion. The mRNA and protein expression levels of transforming growth factor‑β, platelet‑derived growth factor (PDGF)‑A, PDGF‑B and RhoA were also reduced by SOX18 silencing, as assessed by RT‑qPCR and western blot analysis, respectively. These results indicated that SOX18 may function as an oncogene, and may provide a novel and promising therapeutic strategy for osteosarcoma.

Fernández-Guizán A, López-Soto A, Acebes-Huerta A, et al.
Pleiotropic Anti-Angiogenic and Anti-Oncogenic Activities of the Novel Mithralog Demycarosyl-3D-ß-D-Digitoxosyl-Mithramycin SK (EC-8042).
PLoS One. 2015; 10(11):e0140786 [PubMed] Free Access to Full Article Related Publications
Demycarosyl-3D-ß-D-digitoxosyl-mithramycin SK (DIG-MSK) is a recently isolated analogue of mithramycin A (MTA) that showed differences with MTA in the DNA binding strength and selectivity. These differences correlated with a better therapeutic index and less toxicity in animal studies. Herein, we show that DIG-MSK displays a potent anti-tumor activity against different types of cancer cell lines, ovarian tumor cells being particularly sensitive to this drug. Of relevance, DIG-MSK exerts low toxicity on fibroblasts and peripheral blood mononuclear cells, this toxicity being significantly lower than that of MTA. In correlation with its antitumor activity, DIG-MSK strongly inhibited Sp1-mediated transcription and endogenous Sp1 mRNA expression, which correlated with the inhibition of the expression of key Sp1-regulated genes involved in tumorigenesis, including VEGFA, BCL2L1 (Bcl-XL), hTERT, BRCA2, MYC and SRC in several ovarian cells. Significantly, DIG-MSK was a stronger inhibitor of VEGFA expression than MTA. Accordingly, DIG-MSK also exhibited potent anti-angiogenic activity on microvascular endothelial cells. Likewise, it significantly inhibited the gene expression of VEGFR1, VEGFR2, FGFR, PDGFB and PDGFRA and, additionally, it induced the expression of the anti-angiogenic factors angiostatin and tunstatin. These effects correlated with a pro-apoptotic effect on proliferating microvascular endothelial cells and the inhibition of the formation of endothelial capillary structures. Overall, the pleiotropic activity of DIG-MSK in inhibiting key oncogenic and angiogenic pathways, together with its low toxicity profile, highlight the therapeutic potential of this new drug.

Gomez-Casal R, Epperly MW, Wang H, et al.
Radioresistant human lung adenocarcinoma cells that survived multiple fractions of ionizing radiation are sensitive to HSP90 inhibition.
Oncotarget. 2015; 6(42):44306-22 [PubMed] Free Access to Full Article Related Publications
Despite the common usage of radiotherapy for the treatment of NSCLC, outcomes for these cancers when treated with ionizing radiation (IR) are still unsatisfactory. A better understanding of the mechanisms underlying resistance to IR is needed to design approaches to eliminate the radioresistant cells and prevent tumor recurrence and metastases. Using multiple fractions of IR we generated radioresistant cells from T2821 and T2851 human lung adenocarcinoma cells. The radioresistant phenotypes present in T2821/R and T2851/R cells include multiple changes in DNA repair genes and proteins expression, upregulation of EMT markers, alterations of cell cycle distribution, upregulation of PI3K/AKT signaling and elevated production of growth factors, cytokines, important for lung cancer progression, such as IL-6, PDGFB and SDF-1 (CXCL12). In addition to being radioresistant these cells were also found to be resistant to cisplatin.HSP90 is a molecular chaperone involved in stabilization and function of multiple client proteins implicated in NSCLC cell survival and radioresistance. We examined the effect of ganetespib, a novel HSP90 inhibitor, on T2821/R and T2851/R cell survival, migration and radioresistance. Our data indicates that ganetespib has cytotoxic activity against parental T2821 and T2851 cells and radioresistant T2821/R and T2851/R lung tumor cells. Ganetespib does not affect proliferation of normal human lung fibroblasts. Combining IR with ganetespib completely abrogates clonogenic survival of radioresistant cells.Our data show that HSP90 inhibition can potentiate the effect of radiotherapy and eliminate radioresistant and cisplatin -resistant residual cells, thus it may aid in reducing NSCLC tumor recurrence after fractionated radiotherapy.

Smith EH, Lan TT, Jo VY, et al.
Dermatofibrosarcoma Protuberans in a Patient With Cowden Syndrome: Revisiting the PTEN and PDGF Pathways.
Am J Dermatopathol. 2016; 38(4):e40-3 [PubMed] Related Publications
PTEN hamartoma tumor syndrome, of which Cowden syndrome (CS) is the most recognized variant, is characterized by multiple benign and malignant tumors of ectodermal, mesodermal, and endodermal origins, secondary to germline mutation in the phosphatase and tensin homolog (PTEN) gene. Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive malignant fibroblastic/myofibroblastic tumor of the skin, characterized by the t(17:22)(q22:q13) translocation resulting in fusion of the COL1A1 and PDGFB genes. An association between CS and DFSP has not been reported in the literature to date. The authors have encountered a male patient with CS and a history of DFSP that developed adjacent to a sclerotic fibroma on the parietal scalp, both excised at age 7. He presented at age 21 with an enlarging pink nodule at the same site on the parietal scalp. Excision revealed a dermal and subcutaneous storiform spindle cell proliferation with fat entrapment and positive staining for CD34, consistent with DFSP. Fluorescence in situ hybridization confirmed PDGFB gene rearrangement. PTEN expression in the patient's recurrent DFSP was nearly absent when compared with that of sporadic DFSP. To our knowledge, this is the first report of DFSP in a patient with CS. Although the association is likely to be coincidental, the authors revisited the PTEN and the PDGF pathways to speculate any possible interplay of the 2 conditions on a molecular level.

Peyre M, Salaud C, Clermont-Taranchon E, et al.
PDGF activation in PGDS-positive arachnoid cells induces meningioma formation in mice promoting tumor progression in combination with Nf2 and Cdkn2ab loss.
Oncotarget. 2015; 6(32):32713-22 [PubMed] Free Access to Full Article Related Publications
The role of PDGF-B and its receptor in meningeal tumorigenesis is not clear. We investigated the role of PDGF-B in mouse meningioma development by generating autocrine stimulation of the arachnoid through the platelet-derived growth factor receptor (PDGFR) using the RCAStv-a system. To specifically target arachnoid cells, the cells of origin of meningioma, we generated the PGDStv-a mouse (Prostaglandin D synthase). Forced expression of PDGF-B in arachnoid cells in vivo induced the formation of Grade I meningiomas in 27% of mice by 8 months of age. In vitro, PDGF-B overexpression in PGDS-positive arachnoid cells lead to increased proliferation.We found a correlation of PDGFR-B expression and NF2 inactivation in a cohort of human meningiomas, and we showed that, in mice, Nf2 loss and PDGF over-expression in arachnoid cells induced meningioma malignant transformation, with 40% of Grade II meningiomas. In these mice, additional loss of Cdkn2ab resulted in a higher incidence of malignant meningiomas with 60% of Grade II and 30% of Grade III meningiomas. These data suggest that chronic autocrine PDGF signaling can promote proliferation of arachnoid cells and is potentially sufficient to induce meningiomagenesis. Loss of Nf2 and Cdkn2ab have synergistic effects with PDGF-B overexpression promoting meningioma malignant transformation.

Iulia Irimie A, Braicu C, Zanoaga O, et al.
Inhibition of tumor necrosis factor alpha using RNA interference in oral squamous cell carcinoma.
J BUON. 2015 Jul-Aug; 20(4):1107-14 [PubMed] Related Publications
PURPOSE: Oral squamous cell carcinoma (OSCC) is a disease with increased prevalence and unfavorable prognosis calling for development of novel therapeutic strategies. Tumor necrosis factor-α (TNF-α) is a pro-inflammatory cytokine implicated in the development and progression of cancer. The present study was designed to assess the impact of TNF-α specific inhibition using small interference RNA (siRNA) in SSC-4 cells, a representative model for OSCC.
METHODS: The present study evaluated the effect of TNF-α inhibition using siRNA as inhibitory mechanism on SCC-4 cells. The study focused on the effect of TNF-α inhibition on apoptosis, autophagy and invasion in parallel with a panel of 20 genes involved in apoptosis and angiogenesis.
RESULTS: TNF-α inhibition was related with reduction of cell viability, activation of apoptosis and autophagy in parallel with the inhibition of migration in SCC-4 cells. Evaluating the impact on gene expression levels, inhibition of FASL-FADD, NFκB, SEMA 3C, TNF-α, TGFB1, VEGFA, along with activation of PDGFB and SEMA 3D was observed. Our study confirms the important role of TNF-α and sustains that it might be a therapeutic target in OSCC.
CONCLUSIONS: TNF-α is a key mediator of the immune system, with important role in OSCC tumorigenesis, and might be considered as a therapeutic target using siRNA technology, particularly for those risk cases having FASL/FADD overexpressed.

Wiszniewska J, Roy A, Masand RP
Myxoid Dermatofibrosarcoma Protuberans of the Vulva: Case Report of a Rare Variant in an Unusual Location, With Unusual Morphologic and Immunohistochemical Features.
Am J Dermatopathol. 2016; 38(3):226-30 [PubMed] Related Publications
Dermatofibrosarcoma protuberans (DFSP) is a low-to-intermediate grade infiltrative dermal neoplasm with a predilection for the trunk and extremities. DFSP in the vulvar region is extremely rare, with fewer than 50 cases reported to date in the literature. The histologic diagnosis of this neoplasm is facilitated by the characteristic storiform pattern of spindle cells with infiltration into the subcutaneous fat in a "honeycomb" pattern. However, morphologic variants including the very rare myxoid DFSP have been recognized that pose significant diagnostic difficulties, especially when they occur at unusual sites. The authors describe a case of myxoid DFSP of the vulva in a 44-year-old woman that was initially misdiagnosed as a neurofibroma. Subsequent excision led to significant challenges in diagnosis due to lack of typical morphology and unusual immunohistochemical staining pattern. Presence of peripheral adipose tissue trapping was noted focally that led to suspicion of DFSP. The diagnosis was confirmed by the detection of the characteristic COL1A1/PDGFB fusion transcript by reverse-transcription polymerase chain reaction. This case underscores the diagnostic challenge presented by variants of DFSP presenting in unusual locations and the value of molecular confirmation of the diagnosis.

Mishra K, Behari A, Kapoor VK, et al.
Platelet Derived Growth Factor-B and Human Epidermal Growth Factor Receptor-2 Polymorphisms in Gall Bladder Cancer.
Asian Pac J Cancer Prev. 2015; 16(14):5647-54 [PubMed] Related Publications
Gall bladder cancer (GBC) is a gastro-intestinal cancer with high prevalence among north Indian women. Platelet derived growth factor-B (PDGFB) and human epidermal growth factor receptor-2 (HER2) may play roles in the etiology of GBC through the inflammation-hyperplasia-dysplasia-carcinoma pathway. To study the association of PDGFB and HER2 polymorphisms with risk of GBC, 200 cases and 300 controls were considered. PDGFB +286A>G and +1135A>C polymorphisms were investigated with an amplification refractory mutation system and the HER2 Ile655Val polymorphism by restriction fragment length polymorphism. Significant risk associations for PDGFB +286 GG (OR=5.25) and PDGFB +1135 CC (OR=3.19) genotypes were observed for GBC. Gender wise stratification revealed susceptibility for recessive models of PDGFB +1135A>C (OR=3.00) and HER2 Ile655Val (OR=2.52) polymorphisms among female GBC cases. GBC cases with gall stones were predisposed to homozygous +286 GG and +1135 CC genotypes. Significant risk associations were found for ACIle (OR=1.48), GAVal (OR=1.70), GAIle (OR=2.00) haplotypes with GBC cases and GCIle haplotype with female GBC cases (OR=10.37, P=<0.0001). Pair-wise linkage disequilibrium revealed negative associations among variant alleles. On multi-dimensional reduction analysis, a three factor model revealed significant gene-gene interaction for PDGFB +286A>G, PDGFB +1135A>C and HER2 Ile165Val SNPs with GBC. Protein-protein interaction showed significant association of PDGFB and HER2 with the epidermal growth factor receptor signaling pathway.

Hong J, Tobin NP, Rundqvist H, et al.
Role of Tumor Pericytes in the Recruitment of Myeloid-Derived Suppressor Cells.
J Natl Cancer Inst. 2015; 107(10) [PubMed] Related Publications
BACKGROUND: Pericytes are members of the tumor stroma; however, little is known about their origin, function, or interaction with other tumor components. Emerging evidence suggest that pericytes may regulate leukocyte transmigration. Myeloid-derived suppressor cells (MDSC) are immature myeloid cells with powerful inhibitory effects on T-cell-mediated antitumor reactivity.
METHODS: We generated subcutaneous tumors in a genetic mouse model of pericyte deficiency (the pdgfb (ret/ret) mouse) and littermate control mice (n = 6-25). Gene expression profiles from 253 breast cancer patients (stage I-III) were evaluated for clinic-pathological parameters and survival using Cox proportional hazard ratios (HRs) and 95% confidence intervals (CIs) based on a two-sided Wald test.
RESULTS: We report that pericyte deficiency leads to increased transmigration of Gr1(+)/CD11b(+) cells in experimentally induced tumors. Pericyte deficiency produced defective tumor vasculature, resulting in a more hypoxic microenvironment promoting IL-6 upregulation in the malignant cells. Silencing IL-6 expression in tumor cells attenuated the observed differences in MDSC transmigration. Restoring the pericyte coverage in tumors abrogated the increased MDSC trafficking to pericyte-deficient tumors. MDSC accumulation in tumors led to increases in tumor growth and in circulating malignant cells. Finally, gene expression analysis from human breast cancer patients revealed increased expression of the human MDSC markers CD33 and S100A9 with concomitant decreased expression of pericyte genes and was associated with poor prognosis (HR = 1.88, 95% CI = 1.08 to 3.25, P = .03).
CONCLUSIONS: Our data uncovers a novel paracrine interaction between tumor pericytes and inflammatory cells and delineates the cellular events resulting in the recruitment of MDSC to tumors. Furthermore, we propose for the first time a role for tumor pericytes in modulating the expression of immune mediators in malignant cells by promoting a hypoxic microenvironment.

Hindi N, Casali PG, Morosi C, et al.
Imatinib in advanced chordoma: A retrospective case series analysis.
Eur J Cancer. 2015; 51(17):2609-14 [PubMed] Related Publications
INTRODUCTION: Imatinib showed activity in 50 chordoma patients treated within a Phase II study. In that study, 70% of patients remained with stable disease (SD), median progression free survival (PFS) was 9 months and median overall survival (OS) was 34 months. We now report on a retrospective series of PDGFB/PDGFRB positive advanced chordoma patients treated with imatinib as a single agent within a compassionate-use programme at Istituto Nazionale Tumori, Milan, Italy (INT) between August 2002 and November 2010, when the programme was closed.
METHODS: 48 patients were consecutively treated with imatinib 800 mg/d. All patients had inoperable and progressive disease before starting imatinib. Demographics, treatment duration, toxicity and response rate by Response Evaluation Criteria in Solid Tumors (RECIST) were retrospectively recorded.
RESULTS: The median duration of therapy was 7 months (1-46.5). No patient is on therapy at present. 46 patients were evaluable for response. No partial responses were detected. Best response was: stable disease 34 (74%), progressive disease 12 (26%). At a median follow-up of 24.5 months (0.5-117), median PFS was 9.9 months (95% confidence interval (CI) 6.7-13). Eight patients (16.5%) remained on therapy >18 months and 10 patients (21%) remained progression-free >18 months. Median OS was 30 months (95% CI 20-40), with 24 (50%) patients dead at the time of the present analysis.
CONCLUSIONS: We confirm the activity of imatinib in locally advanced and metastatic chordoma, in terms of >70% tumour growth arrest in previously progressive patients. Median duration of response lasted almost 10 months, with >20% of patients progression-free at 18+ months.

Xu WJ, Wang JS
Atrophic dermatofibrosarcoma protuberans with the fusion gene COL1A1-PDGFB detected by RT-PCR using only a single primer pair.
Int J Clin Exp Pathol. 2015; 8(6):7457-63 [PubMed] Free Access to Full Article Related Publications
Dermatofibrosarcoma protuberans (DFSPs) is an uncommon dermal tumor of intermediate to low-grade malignancy. A few patients have clinically persistent plaques that might be atrophic, and they are difficult to be diagnosed clinically. With the development of cytogenetic and molecular biology techniques, the detection of fusion transcripts of the collagen type 1a1 (COL1A1) and platelet-derived growth factor-BB (PDGFB) genes has been recognized as a reliable and valuable molecular tool for the diagnosis of DFSPs. We reported a 24-year-old woman who had a 2 years history of atrophic DFSPs, and detected the gene fusion between COL1A1 to PDGFB by one-step method of RT-PCR using only a single primer pair. The gene fusion detected by this rapid and efficient one-step method in our patient appears to be the first report of atrophic DFSPs, and we detected a novel COL1A1 breakpoint between exon 2 and exon 3.

Stacchiotti S, Pantaleo MA, Negri T, et al.
Efficacy and Biological Activity of Imatinib in Metastatic Dermatofibrosarcoma Protuberans (DFSP).
Clin Cancer Res. 2016; 22(4):837-46 [PubMed] Related Publications
PURPOSE: To report on imatinib mesylate (IM) in patients with metastatic dermatofibrosarcoma protuberans (DFSP)/fibrosarcomatous (FS)-DFSP and on the impact of the treatment on tumor biology.
EXPERIMENTAL DESIGN: Ten consecutive patients treated with IM from 2007 to 2015 for a metastatic relapse from DFSP/FS-DFSP were identified. FISH analysis for COL1A1-PDGFB was performed. Two IM-treated and 4 naïve FS-DFSP were transcriptionally profiled by RNAseq on HiScanSQ platform. Differential gene expression was analyzed with edgeR (Bioconductor), followed by hierarchical clustering and Principal Component Analysis.
RESULTS: All cases featured fibrosarcomatous in the metastasis and retained the COL1A1-PDGFB. Best RECIST response was: 8 partial response, 1 stable disease, and 1 progressive disease. Median progression-free survival was 11 months. Five patients received surgery after IM and all relapsed. IM was restored in 4 patients with a new response. After IM, the most upregulated genes included those encoding for immunoglobulins and those affecting functions and differentiation of endothelial cells. Pathway enrichment analysis revealed upregulation in genes involved in antigen processing and presentation, natural killer-mediated cytotoxicity, and drug and xenobiotics metabolism. Conversely, a significant down-regulation of kinase signaling pathways was detected.
CONCLUSIONS: All metastatic cases were fibrosarcomatous. Most patients responded to IM, but PFS was shorter than reported in published series which included both DFSP and FS-DFSP. All patients operated after IM had a relapse, suggesting that IM cannot eradicate metastatic cases and that the role of surgery is limited. Transcriptional profile of naïve and posttreatment samples pointed the contribution of immune infiltrates in sustaining the response to IM.

Wang G, Wei Z, Jia H, et al.
Knockdown of SOX18 inhibits the proliferation, migration and invasion of hepatocellular carcinoma cells.
Oncol Rep. 2015; 34(3):1121-8 [PubMed] Free Access to Full Article Related Publications
Hepatocellular carcinoma (HCC) is one of the most common malignancies in the world. Recent studies have demonstrated that SOX18 is highly expressed in various types of cancer. In the present study, we found that SOX18 mRNA was overexpressed in HCC compared with non-tumorous tissues. We aimed to explore the effects of SOX18 siRNA on the proliferation, invasion and migration of two HCC cell lines, MHCC97H and HepG2, which overexpress SOX18. We found that SOX18 siRNA significantly inhibited the proliferation and induced cell cycle arrest at the G0/G1 phase. Results of the Transwell assay showed that the migration and invasion of the HCC cells were markedly impaired in the SOX18-knockdown cells. Gene set enrichment analysis (GSEA) showed that KEGG focal adhesion and chemokine signaling pathways were correlated with SOX18 expression. Furthermore, the mRNA and protein levels of RhoA, PDGFB, IGF1R, CCL2, CCL3 and CCL5 were decreased in the SOX18-knockdown cells. Importantly, we demonstrated that upregulation of SOX18 was associated with a poor outcome in HCC patients. These results indicate that SOX18 may serve as a prognostic factor and a promising therapeutic strategy for HCC.

Chen Y, Wang Z, Dai X, et al.
Glioma initiating cells contribute to malignant transformation of host glial cells during tumor tissue remodeling via PDGF signaling.
Cancer Lett. 2015; 365(2):174-81 [PubMed] Related Publications
INTRODUCTION: Glioma initiating cells (GICs) play important roles in tumor initiation and progression. However, interactions between tumor cells and host cells of local tumor microenvironment are kept largely unknown. Besides GICs and their progeny cells, whether adjacent normal glial cells contribute to tumorigenesis during glioma tissue remodeling deserves further investigation.
METHODS: Red fluorescence protein (RFP) gene was stably transfected into human GIC cells lines SU3 and U87, then were transplanted intracerebrally into athymic nude mice with whole-body green fluorescence protein (GFP) expression. The interactions between GICs and host cells in vivo were observed during tissue remodeling processes initiated by hGICs. The biological characteristics of host glial cells with high proliferation capability cloned from the xenograft were further assayed.
RESULTS: In a SU3 initiated dual-fluorescence xenograft glioma model, part of host cells cloned from the intracerebral tumors were found acquiring the capability of unlimited proliferation. PCR and FISH results indicated that malignant transformed cells were derived from host cells; cell surface marker analysis showed these cells expressed murine oligodendrocyte specific marker CNP, and oligodendrocyte progenitor cells (OPCs) specific markers PDGFR-α and NG2. Chromosomal analysis showed these cells were super tetraploid. In vivo studies showed they behaved with high invasiveness activity and nearly 100% tumorigenic ratio. Compared with SU3 cells with higher PDGF-B expression, GICs derived from U87 cells with low level of PDGF-B expression failed to induce host cell transformation.
CONCLUSIONS: Primary high invasive GICs SU3 contribute to transformation of adjacent normal host glial cells in local tumor microenvironment possibly via PDGF/PDGFR signaling activation, which deserved further investigation.

Liu G, Chen Y, Qi F, et al.
Specific chemotherapeutic agents induce metastatic behaviour through stromal- and tumour-derived cytokine and angiogenic factor signalling.
J Pathol. 2015; 237(2):190-202 [PubMed] Related Publications
Recent studies reveal that chemotherapy can enhance metastasis due to host responses, such as augmented expression of adhesion molecules in endothelial cells and increased populations of myeloid cells. However, it is still unclear how tumour cells contribute to this process. Here, we observed that paclitaxel and carboplatin accelerated lung metastasis in tumour-bearing mice, while doxorubicin and fluorouracil did not. Mechanistically, paclitaxel and carboplatin induced similar changes in cytokine and angiogenic factors. Increased levels of CXCR2, CXCR4, S1P/S1PR1, PlGF and PDGF-BB were identified in the serum or primary tumour tissues of tumour-bearing mice treated by paclitaxel. The serum levels of CXCL1 and PDGF-BB and the tissue level of CXCR4 were also elevated by carboplatin. On the other hand, doxorubicin and fluorouracil did not induce such changes. The chemotherapy-induced cytokine and angiogenic factor changes were also confirmed in gene expression datasets from human patients following chemotherapy treatment. These chemotherapy-enhanced cytokines and angiogenic factors further induced angiogenesis, destabilized vascular integrity, recruited BMDCs to metastatic organs and mediated the proliferation, migration and epithelial-to-mesenchymal transition of tumour cells. Interestingly, inhibitors of these factors counteracted chemotherapy-enhanced metastasis in both tumour-bearing mice and normal mice injected intravenously with B16F10-GFP cells. In particular, blockade of the SDF-1α-CXCR4 or S1P-S1PR1 axes not only compromised chemotherapy-induced metastasis but also prolonged the median survival time by 33.9% and 40.3%, respectively. The current study delineates the mechanism of chemotherapy-induced metastasis and provides novel therapeutic strategies to counterbalance pro-metastatic effects of chemo-drugs via combination treatment with anti-cytokine/anti-angiogenic therapy.

Wang M, Liu Y, Zou J, et al.
Transcriptional co-activator TAZ sustains proliferation and tumorigenicity of neuroblastoma by targeting CTGF and PDGF-β.
Oncotarget. 2015; 6(11):9517-30 [PubMed] Free Access to Full Article Related Publications
Neuroblastoma is a common childhood malignant tumor originated from the neural crest-derived sympathetic nervous system. A crucial event in the pathogenesis of neuroblastoma is to promote proliferation of neuroblasts, which is closely related to poor survival. However, mechanisms for regulation of cell proliferation and tumorigenicity in neuroblastoma are not well understood. Here, we report that overexpression of TAZ in neuroblastoma BE(2)-C cells causes increases in cell proliferation, self renewal and colony formation, which was restored back to its original levels by knockdown of TAZ in TAZ-overexpression cells. Inhibition of endogenous TAZ attenuated cell proliferation, colony formation and tumor development in neuroblastoma SK-N-AS cell, which could be rescued by re-introduction of TAZ into TAZ-knockdown cells. In addition, we found that overexpressing TAZ-mediated induction of CTGF and PDGF-β expression, cell proliferation and colony formation were inhibited by knocking down CTGF and PDGF-β with siRNA in TAZ-overexpressing cell. Overall, our findings suggested that TAZ plays an essential role in regulating cell proliferation and tumorigenesis in neuroblastoma cells. Thus, TAZ seems to be a novel and promising target for the treatment of neuroblastoma.

Yamaguchi SI, Ueki A, Sugihara E, et al.
Synergistic antiproliferative effect of imatinib and adriamycin in platelet-derived growth factor receptor-expressing osteosarcoma cells.
Cancer Sci. 2015; 106(7):875-82 [PubMed] Free Access to Full Article Related Publications
Osteosarcoma (OS) is the most frequent primary solid malignant tumor of bone. Its prognosis remains poor in the substantial proportion of patients who do not respond to chemotherapy and novel therapeutic options are therefore needed. We previously established a mouse model that mimics the aggressive behavior of human OS. Enzyme-linked immunosorbent assay-based screening of such mouse tumor lysates identified platelet-derived growth factor-BB (PDGF-BB) as an abundant soluble factor, the gene for which was expressed dominantly in surrounding non-malignant cells of the tumor, whereas that for the cognate receptor (PDGF receptor β) was highly expressed in OS cells. Platelet-derived growth factor-BB induced activation of both MEK-ERK and phosphatidylinositol 3-kinase-protein kinase B signaling pathways and promoted survival in OS cells deprived of serum, and these effects were blocked by the PDGF receptor inhibitor imatinib. However, these actions of PDGF-BB and imatinib were mostly masked in the presence of serum. Whereas imatinib alone did not manifest an antitumor effect in mice harboring OS tumors, combined treatment with imatinib and adriamycin exerted a synergistic antiproliferative effect on OS cells in vivo. These results suggest that treatment of OS with imatinib is effective only when cell survival is dependent on PDGF signaling or when imatinib is combined with another therapeutic intervention that renders the tumor cells susceptible to imatinib action, such as by inducing cellular stress.

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