Gene Summary

Gene:TLR7; toll like receptor 7
Aliases: TLR7-like
Summary:The protein encoded by this gene is a member of the Toll-like receptor (TLR) family which plays a fundamental role in pathogen recognition and activation of innate immunity. TLRs are highly conserved from Drosophila to humans and share structural and functional similarities. They recognize pathogen-associated molecular patterns (PAMPs) that are expressed on infectious agents, and mediate the production of cytokines necessary for the development of effective immunity. The various TLRs exhibit different patterns of expression. This gene is predominantly expressed in lung, placenta, and spleen, and lies in close proximity to another family member, TLR8, on chromosome X. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:toll-like receptor 7
Source:NCBIAccessed: 29 August, 2019


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 (1994-2019)
Graph generated 29 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Latest Publications: TLR7 (cancer-related)

Meliț LE, Mărginean CO, Mărginean CD, Mărginean MO
The Relationship between Toll-like Receptors and
J Immunol Res. 2019; 2019:8197048 [PubMed] Free Access to Full Article Related Publications
Innate immunity represents the first barrier against bacterial invasion. Toll-like receptors (TLRs) belong to the large family of pattern recognition receptors (PRRs), and their activation leads to the induction of inflammatory cytokines, chemokines, antigen-presenting molecules, and costimulatory molecules. Recent studies have focused on identifying the association between TLRs and

Haeggblom L, Näsman A, Ramqvist T, et al.
TLR5 and TLR7 are differentially expressed in human papillomavirus-positive and negative base of tongue squamous cell carcinoma, and TLR7 may have an independent prognostic influence.
Acta Otolaryngol. 2019; 139(2):206-210 [PubMed] Related Publications
BACKGROUND: Human papillomavirus-positive (HPV
AIMS/OBJECTIVES: For validation, TLR5 and TLR7 were analyzed in a BOTSCC-cohort for correlation with HPV, survival, CD4
RESULTS: TLR5 expression was more frequently absent/weak than medium/strong in HPV
CONCLUSION AND SIGNIFICANCE: Absent/weak TLR5 and medium/strong TLR7 expression was validated as more frequent in HPV

Li W, Zhang L, Guo B, et al.
Exosomal FMR1-AS1 facilitates maintaining cancer stem-like cell dynamic equilibrium via TLR7/NFκB/c-Myc signaling in female esophageal carcinoma.
Mol Cancer. 2019; 18(1):22 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Though esophageal cancer is three to four times more common among males than females worldwide, this type of cancer still ranks in the top incidence among women, even more than the female specific cancer types. The occurrence is currently attributed to extrinsic factors, including tobacco use and alcohol consumption. However, limited attention has been given to gender-specific intrinsic genetic factors, especially in female.
METHODS: We re-annotated a large cohort of microarrays on 179 ESCC patients and identified female-specific differently expressed lncRNAs. The associations between FMR1-AS1 and the risk and prognosis of ESCC were examined in 206 diagnosed patients from eastern China and validated in 188 additional patients from southern China. The effects of FMR1-AS1 on the malignant phenotypes on female ESCC cells were detected in vitro and in vivo. ChIRP-MS, reporter gene assays and EMSA were conducted to identify the interaction and regulation among FMR1-AS1, TLR7 and NFκB.
RESULTS: We found FMR1-AS1 expression is exclusively altered and closely associated with the level of sXCI in female ESCC patients, and its overexpression may correlate to poor clinical outcome. ChIRP-MS data indicate that FMR1-AS1 could be packaged into exosomes and released into tumor microenvironment. Functional studies demonstrated that FMR1-AS1 could bind to endosomal toll-like receptor 7 (TLR7) and activate downstream TLR7-NFκB signaling, promoting the c-Myc expression, thus inducing ESCC cell proliferation, anti-apoptosis and invasion ability. Exosome incubation and co-xenograft assay indicate that FMR1-AS1 exosomes may secreted from ESCC CSCs, transferring stemness phenotypes to recipient non-CSCs in tumor microenvironment. Furthermore, we also found a correlation between the serum levels of FMR1-AS1 and the overall survival (OS) of the female ESCC patients.
CONCLUSIONS: Our results highlighted exosomal FMR1-AS1 in maintaining CSC dynamic interconversion state through the mechanism of activating TLR7-NFκB signaling, upregulating c-Myc level in recipient cells, which may be taken as an attractive target approach for advancing current precision cancer therapeutics in female patients.

Mosaad YM, Metwally SS, Farag RE, et al.
Association between Toll-Like Receptor 3 (TLR3) rs3775290, TLR7 rs179008, TLR9 rs352140 and Chronic HCV.
Immunol Invest. 2019; 48(3):321-332 [PubMed] Related Publications
BACKGROUND: Inconsistent results were reported on the association of TLRs polymorphisms with the risk of HCV infection and HCV-related diseases.
OBJECTIVE: to assess the relation between TLR3 rs3775290, TLR7 rs17900 and TLR9 rs352140 SNPs and chronic HCV in the Egyptian cohort and to study their relation to interferon response.
METHODS: TLR3 rs3775290, TLR7 rs179008 and TLR9 rs352140 gene polymorphisms were typed by RFLP for 100 patients with chronic HCV and 25 with HCC in addition to 100 healthy controls.
RESULTS: A significant higher frequency has been found for the CT genotype of TLR3 rs3775290 in chronic HCV infection (p < 0.001) and CC genotype and the combined genotype CC-AT-GA ♀ in controls (p < 0.001). Non-significant associations have been found for studied SNPs and HCC and response to interferon and also the viral load or the degree of fibrosis, however, the higher HCV viral load and the higher grade of fibrosis were associated with treatment failure (p < 0.001).
CONCLUSION: The heterozygous CT genotype of TLR3 rs3775290 may be a susceptibility risk factor for chronic HCV infection and the homozygous CC and the combined CC-AT-GA ♀ genotypes may be protective. The HCV viral load and the grades of liver fibrosis could be considered a risk factor for interferon treatment failure. It seems that the studied SNPs have no role in HCC development or failure of treatment. However, the small sample size is a limiting factor of the present study when interpreting the negative associations and that the current used cohort does not permit such conclusion.
ABBREVIATIONS: cHCV=chronic Hepatitis C virus, HCC=hepatocellular carcinoma, TLR=Toll like Receptor, RFLP=Restriction Fragment Length Polymorphism, SNP=Single Nucleotide Polymorphism, IFN-α= interferon alpha.

Halec G, Scott ME, Farhat S, et al.
Toll-like receptors: Important immune checkpoints in the regression of cervical intra-epithelial neoplasia 2.
Int J Cancer. 2018; 143(11):2884-2891 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Toll-like receptors (TLRs) are innate immune defenders thought to be critical for the clearance of human papillomavirus (HPV) infections hence preventing the development of HPV-associated high-grade cervical intra-epithelial neoplasia (CIN2 or 3), a potential cervical cancer precursor. However, the role of TLRs in the regression of established cervical lesions, such as CIN2, is hindered by a lack of prospective design studies. Using SYBR green real-time PCR assays, we have examined the gene expression of TLR2, TLR3, TLR7, TLR8 and TLR9, in cytobrush collected endocervical cells of 63 women diagnosed with CIN2 at study entry (baseline) and followed over a 3-year period. Wilcoxon rank-sum test was used to examine the association between TLR expression levels, measured at baseline, and CIN2 outcome (regression vs. persistence/progression) over time. HPV genotyping was performed using Roche Linear Array Assay detecting 37 HPV types. Women with CIN2 regression showed significantly higher baseline levels of TLR2 (p = 0.006) and TLR7 (p = 0.007), as well as a non-significant trend for a higher TLR8 expression (p = 0.053) compared to women with CIN2 persistence/progression. Six women with CIN2 regression, who presented with an HR-HPV DNA-negative CIN2 lesion at study entry, had significantly higher baseline levels of TLR2 (p = 0.005), TLR7 (p = 0.013) and TLR8 (p = 0.012), compared to women with CIN2 persistence/progression, suggesting their role in clearance of HPV prior to clearance of the lesion. Our results confirm a key role of TLRs in regression of CIN2 and support the potential use of TLR-agonists for treatment of these lesions.

Diakowska D, Nienartowicz M, Grabowski K, et al.
Toll-like receptors TLR-2, TLR-4, TLR-7, and TLR-9 in tumor tissue and serum of the patients with esophageal squamous cell carcinoma and gastro-esophageal junction cancer.
Adv Clin Exp Med. 2019; 28(4):515-522 [PubMed] Related Publications
BACKGROUND: Stimulation of toll-like receptors (TLRs) has been linked to the development of esophageal and gastric cancers.
OBJECTIVES: The aim of the study was to evaluate the clinical significance of tissue expression and serum concentration of TLR-2, TLR-4, TLR-7 and TLR-9 in patients with esophageal squamous cell carcinoma and gastro-esophageal junction adenocarcinoma.
MATERIAL AND METHODS: The study group consisted of 97 individuals: 32 with esophageal squamous cell carcinoma, 27 with gastro-esophageal junction cancer, and 38 ageand gender-matched controls. The mRNA expression and protein concentration of TLRs in tissues and sera were measured by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) tests.
RESULTS: In esophageal cancer patients, mRNA expressions of TLR-2, TLR-4 and TLR-7, and protein concentrations of all TLRs were significantly higher in tumor than in control tissue (p < 0.05). In esophageal cancer patients with lymph node metastasis, a tendency toward higher protein concentrations of tumor TLR-4 was observed. In gastro-esophageal junction adenocarcinoma subgroup, only the mRNA expression of TLR-7 and protein concentrations of TLR-4, TLR-7 and TLR-9 were significantly higher in tumors than in normal mucosa (p < 0.05). Protein concentration of TLR-9 was significantly higher in tumors of gastro-esophageal junction cancer with lymph node metastasis and depth of tumor invasion. Diagnostic potential of serum TLR-4 as a marker of gastro-esophageal junction cancer presence was reported.
CONCLUSIONS: We demonstrated differences in the expression patterns of TLRs between esophageal squamous cell carcinoma and adenocarcinoma of gastro-esophageal junction, and showed circulating TLR-4 to be a potential marker of gastro-esophageal junction cancer.

Kylmä AK, Jouhi L, Listyarifah D, et al.
Treponema denticola chymotrypsin-like protease as associated with HPV-negative oropharyngeal squamous cell carcinoma.
Br J Cancer. 2018; 119(1):89-95 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
BACKGROUND: An opportunistic oral pathogen, Treponema denticola (Td), has been linked to orodigestive carcinogenesis, but its role in oropharyngeal squamous cell carcinoma (OPSCC) has remained open. We evaluated the presence of Td chymotrypsin-like protease (Td-CTLP) in a series of 201 unselected consecutive OPSCC patients, and the relation of the Td-CTLP to human papillomavirus (HPV) status, to expression of toll-like receptors (TLR) 5, 7, and 9, and to clinical parameters and patient outcome.
METHODS: Clinicopathological data came from hospital registries. The expression of cell surface-bound Td-CTLP was evaluated by immunohistochemistry. Immunoexpression of TLRs 5, 7, and 9, and HPV status we studied earlier in this patient series.
RESULTS: We detected Td-CTLP in 81% of the OPSCC, and especially in HPV-negative tumours (48% of all OPSCCs). Among the HPV-positive tumours (52% of all OPSCCs), low Td-CTLP expression associated with low TLR 5 and high TLR 7 expression. Among those HPV-negative, higher TLR 5 and lower TLR 7 expression associated with high Td-CTLP expression. Strong Td-CTLP expression associated with poor disease-specific survival, but no similar association among HPV-positive and HPV-negative subgroups emerged.
CONCLUSIONS: Td-CTLP was highly expressed in OPSCC and was associated with the HPV status of tumour tissue.

Liu J, Qu X, Shao L, et al.
Pim-3 enhances melanoma cell migration and invasion by promoting STAT3 phosphorylation.
Cancer Biol Ther. 2018; 19(3):160-168 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Melanoma is the deadliest form of commonly encountered skin cancer, and has fast propagating and highly invasive characteristics. Pim-3, a highly expressed oncogene in melanoma, is a highly conserved serine/threonine kinase with various biological activities, such as proliferation-accelerating and anti-apoptosis effects on cancer progression. However, whether Pim-3 regulates melanoma metastasis has not been determined. Here, we constructed a Pim-3-silencing short hairpin RNA (sh-Pim-3), a TLR7-stimulating ssRNA and a dual-function vector containing a sh-Pim-3 and a ssRNA, and transfected them into the B16F10 melanoma cell line to investigate the effects of Pim-3 on migration and invasion in melanoma. We found that sh-Pim-3 inhibited B16F10 cell migration and invasion in vitro. In a tumor-bearing mouse model, sh-Pim-3 significantly downregulated pulmonary metastasis of B16F10 melanoma cell in vivo. Mechanistically, sh-Pim-3 inhibited metastasis by regulating the expression of genes related to epithelial-mesenchymal transition (EMT). Further study revealed that by promoting the phosphorylation of STAT3 (signal transducer and activator of transcription 3), Pim-3 induced the expression of Slug, Snail, and ZEB1, which enhanced EMT-related changes and induced melanoma migration and invasion. Our study suggests that Pim-3 is a potential effective target for melanoma therapy.

Klymenko T, Gu Q, Herbert I, et al.
RNA-Seq Analysis of Differentiated Keratinocytes Reveals a Massive Response to Late Events during Human Papillomavirus 16 Infection, Including Loss of Epithelial Barrier Function.
J Virol. 2017; 91(24) [PubMed] Article available free on PMC after 01/12/2019 Related Publications
The human papillomavirus (HPV) replication cycle is tightly linked to epithelial cell differentiation. To examine HPV-associated changes in the keratinocyte transcriptome, RNAs isolated from undifferentiated and differentiated cell populations of normal, spontaneously immortalized keratinocytes (NIKS) and NIKS stably transfected with HPV16 episomal genomes (NIKS16) were compared using next-generation sequencing (RNA-Seq). HPV16 infection altered expression of 2,862 cellular genes. Next, to elucidate the role of keratinocyte gene expression in late events during the viral life cycle, RNA-Seq was carried out on triplicate differentiated populations of NIKS (uninfected) and NIKS16 (infected). Of the top 966 genes altered (>log

Zhu J, Zhang T, Cao L, et al.
Toll like receptor7 polymorphisms in relation to disease susceptibility and progression in Chinese patients with chronic HBV infection.
Sci Rep. 2017; 7(1):12417 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Toll-like receptors (TLRs) play a key role in innate and adaptive immunity, protecting the host from viral pathogens. We studied the effect of TLR7 polymorphisms on disease susceptibility and progression of chronic hepatitis B (CHB) infection in Chinese adults. Blood samples were taken from 612 patients with confirmed CHB, hepatitis B virus (HBV)-related liver cirrhosis (LC) or hepatocellular carcinoma (HCC) and 293 controls. TLR7 polymorphisms (rs179010-C > T, rs2074109-T > C, and rs179009-A > G) were analyzed by PCR-based sequencing. A significantly higher frequency of TLR7 rs179010 C allele was found in male CHB patients than in controls (74.8% vs 59.5%, P = 0.002). The frequency of rs179009 G allele was markedly increased with disease progression when male patients with CHB, LC and HCC were compared (P = 0.012). The haplotype CTA was significantly associated with an increased susceptibility to CHB among male patients (P = 0.000). Frequency of the haplotype CTG was higher in male patients with HCC than CHB (P = 0.005). No such differences in these allele frequencies were found between female patients and controls. Our results indicated that TLR7 polymorphisms play an important role in disease susceptibility and the progression of CHB infections in Chinese adults, and may partly explain the high incidence of HBV related diseases in Chinese men.

Park GB, Kim D
TLR5/7-mediated PI3K activation triggers epithelial-mesenchymal transition of ovarian cancer cells through WAVE3-dependent mesothelin or OCT4/SOX2 expression.
Oncol Rep. 2017; 38(5):3167-3176 [PubMed] Related Publications
Toll-like receptor (TLR)-mediated signaling induces cell migration or invasion in several tumors and various stages of cancer. Interactions of mesothelin, a 40-kDa cell surface glycoprotein, with cancer antigen 125 (CA125) is associated with drug resistance, metastasis, and poor clinical outcome of ovarian cancer patients. In this study, we examined the role of TLR5 and TLR7 in the metastasis of ovarian cancer through the induction of mesothelin/CA125 expression and investigated its underlying mechanism. TLR5 agonist (flagellin) and TLR7 agonist (imiquimod) upregulated mesenchymal phenotypes and produced epithelial-mesenchymal transition (EMT)-related cytokines in the SKOV3 cells; however, TLR7 expressing CaOV3 cells had no response to the specific ligand, imiquimod, for enhancing its EMT processes. Stimulation of the SKOV3 cells with flagellin or imiquimod activated Wiskott-Aldrich syndrome protein verprolin-homologous 3 (WAVE3) and mesothelin/CA125, whereas it suppressed the expression of TAp63. Moreover, knockdown of TLR5 or TLR7 in SKOV3 cells profoundly impaired the TLR5- or TLR7-intiated downstream signaling pathway. Loss of WAVE3 in SKOV3 cells led to the inhibition of invasion, suppression of mesenchymal characteristics, prevention of OCT4/SOX2 secretion, and attenuation of mesothelin/CA125 expression after stimulation with flagellin or imiquimod. Although the disruption of mesothelin decreased the migratory activity of the TLR5/7-activated SKOV3 cells, knockdown of mesothelin failed to reduce the expression of mesenchymal markers, OCT4, and SOX2. In addition, targeting OCT4 or SOX2 with siRNA had no effect on the expression of mesothelin and the suppression of transcriptionally active p63 (TAp63) in the TLR5/7-stimulated SKOV3 cells. Our results suggest that TLR5/7-mediated WAVE3 activation not only controls the mesothelin-related EMT processes but also modulates OCT4/SOX2-mediated mesenchymal marker expression. Taken together, both TLR5 and TLR7 expression are critical for the TLR5/7-induced metastasis of ovarian cancer and the inhibition of WAVE3 might be a new therapeutic target to control ovarian cancer metastasis.

Lopez PA, Denny M, Hartmann AK, et al.
Transcutaneous immunization with a novel imiquimod nanoemulsion induces superior T cell responses and virus protection.
J Dermatol Sci. 2017; 87(3):252-259 [PubMed] Related Publications
BACKGROUND: Transcutaneous immunization (TCI) is a novel vaccination strategy utilizing the skin associated lymphatic tissue to induce immune responses. TCI using a cytotoxic T lymphocyte (CTL) epitope and the Toll-like receptor 7 (TLR7) agonist imiquimod mounts strong CTL responses by activation and maturation of skin-derived dendritic cells (DCs) and their migration to lymph nodes. However, TCI based on the commercial formulation Aldara only induces transient CTL responses that needs further improvement for the induction of durable therapeutic immune responses.
OBJECTIVE: Therefore we aimed to develop a novel imiquimod solid nanoemulsion (IMI-Sol) for TCI with superior vaccination properties suited to induce high quality T cell responses for enhanced protection against infections.
METHODS: TCI was performed by applying a MHC class I or II restricted epitope along with IMI-Sol or Aldara (each containing 5% Imiquimod) on the shaved dorsum of C57BL/6, IL-1R, Myd88, Tlr7 or Ccr7 deficient mice. T cell responses as well as DC migration upon TCI were subsequently analyzed by flow cytometry. To determine in vivo efficacy of TCI induced immune responses, CTL responses and frequency of peptide specific T cells were evaluated on day 8 or 35 post vaccination and protection in a lymphocytic choriomeningitis virus (LCMV) infection model was assessed.
RESULTS: TCI with the imiquimod formulation IMI-Sol displayed equal skin penetration of imiquimod compared to Aldara, but elicited superior CD8
CONCLUSION: Our data demonstrate that IMI-Sol TCI can overcome current limitations of previous imiquimod based TCI approaches opening new perspectives for transcutaneous vaccination strategies and allowing the use of this enhanced cutaneous drug-delivery system to be tailored for the improved prevention and treatment of infectious diseases and cancers.

Doorduijn EM, Sluijter M, Salvatori DC, et al.
Cancer Immunol Res. 2017; 5(8):642-653 [PubMed] Related Publications
One of the next challenges in cancer immunotherapy is the resistance of tumors to T-cell-based treatments through loss of MHC class I. Here, we show that under these circumstances, the Toll-like receptor (TLR)-7/8 ligand imiquimod, but not the TLR3 ligand poly I:C or TLR9 ligand CpG, mediated an effective antitumor response. The rejection of these immune-escaped cancers was mediated by NK cells and CD4

Li J, Rao H, Jin C, Liu J
Involvement of the Toll-Like Receptor/Nitric Oxide Signaling Pathway in the Pathogenesis of Cervical Cancer Caused by High-Risk Human Papillomavirus Infection.
Biomed Res Int. 2017; 2017:7830262 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Human papillomavirus (HPV) can activate Toll-like receptor (TLR)/nitric oxide (NO) signaling pathways; however, whether the TLR/NO pathway is involved in cervical cancer caused by high-risk HPV (HR-HPV) remains unclear. In this study, 43 HR-HPV-positive patients with cervical cancer (CC group), 39 HR-HPV-positive patients with a healthy cervix (HR-HPV group), and 33 HR-HPV-negative controls were recruited. NO concentration in cervical canal and expression of inducible NO synthase (iNOS) in cervical tissues were detected. Expressions of key TLR/NO pathway genes (TLR3/4/7/8, NF-

Li F, Li X, Zou GZ, et al.
Association between
World J Gastroenterol. 2017; 23(9):1602-1607 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
AIM: To explore whether copy number variations (CNVs) of toll-like receptor 7 (
METHODS: This study included 623 patients (495 males and 128 females) with chronic hepatitis B virus infection (CHB) and 300 patients (135 females and 165 males) with acute hepatitis B virus infection (AHB) as controls. All CHB patients were further categorized according to disease progression after HBV infection (CHB, liver cirrhosis, or hepatocellular carcinoma). Copy numbers of the
RESULTS: Among male patients, there were significant differences between the AHB group and CHB group in the distribution of

El Tawdy AM, Amin IM, Abdel Hay RM, et al.
Toll-like receptor (TLR)7 expression in mycosis fungoides and psoriasis: a case-control study.
Clin Exp Dermatol. 2017; 42(2):172-177 [PubMed] Related Publications
BACKGROUND: Toll-like receptors (TLRs) have been implicated in various dermatological diseases. TLR agonists have the capacity to potently activate the innate immune cells of patients with advanced, refractory, cutaneous T-cell lymphoma (CTCL).
AIM: To detect TLR7 gene expression in mycosis fungoides (MF) (a neoplastic skin condition) and to compare it with psoriasis (an inflammatory skin condition) in an attempt to clarify the pathogenic role played by TLR7 in both conditions.
METHODS: This case-control study enrolled 28 patients with MF: 30 patients with psoriasis, and 30 age- and sex-matched healthy controls (HCs). A 4-mm punch skin biopsy was obtained from lesional skin of patients and from normal skin of HCs for detection of TLR7 gene expression using real-time PCR.
RESULTS: Mean TLR7 level in patients with MF (0.4 ± 0.23) was significantly lower than in patients with psoriasis (1.49 ± 0.46) and in HCs (1.22 ± 0.44) (P < 0.001), and mean TLR7 level in patients with psoriasis was significantly higher than in HCs (P < 0.03). Based on MF staging, 21.4% of patients had stage Ia, 28.6% had stage Ib, 28.6% had stage IIa and 21.4% had stage IIb disease. Comparing the TLR7 levels in relation to MF staging revealed the lowest mean value was in stage IIb and highest mean value in stage Ia, and this was significant (P < 0.001).
CONCLUSION: Disturbed innate immunity might play a role in the pathogenesis of neoplastic and inflammatory skin conditions. TLR7 could be useful as a prognostic factor in MF.

Swerev TM, Wirth T, Ushmorov A
Activation of oncogenic pathways in classical Hodgkin lymphoma by decitabine: A rationale for combination with small molecular weight inhibitors.
Int J Oncol. 2017; 50(2):555-566 [PubMed] Related Publications
DNA methylation is an epigenetic control mechanism that contributes to the specific phenotype and to the oncogenic program of virtually all tumor entities. Although efficacy of demethylating agents in classical Hodgkin lymphoma (cHL) was not specifically tested, a case of regression of relapsed metastatic cHL was described as a fortunate side‑effect of the demethylating agent 5‑azacytidine in a patient with myelodysplastic syndrome. We investigated molecular mechanisms of decitabine (5‑Aza‑dC) antitumor activity in cHL using gene expression profiling followed by gene set enrichment analysis. We found that 5‑Aza‑dC inhibits growth of cHL cell lines at clinically relevant concentrations of 0.25‑2 µM. The antitumor effect of 5‑Aza‑dC was associated with induction of genes, which negatively regulate cell cycle progression (e.g. CDKN1A and GADD45A). Surprisingly, we also observed significant enrichment of pro‑survival pathways like MEK/ERK, JAK‑STAT and NF‑κB, as well as signatures comprising transcription‑activating genes. Among the upregulated pro‑survival genes were the anti‑apoptotic genes BCL2 and BCL2L1, as well as genes involved in transduction of growth and survival signals like STAT1, TLR7, CD40 and IL-6. We therefore analyzed whether interference with these pro‑survival pathways and genes would potentiate the antitumor effect of 5‑Aza‑dC. We could show that the BCL2/BCL2L1 inhibitor ABT263, the JAK‑STAT inhibitors fedratinib and SH‑4‑54, the AKT inhibitor KP372‑1, the NF‑κB inhibitor QNZ, as well as the bromodomain and extraterminal (BET) family proteins inhibitor JQ1 acted synergistically with 5‑Aza‑dC. We conclude that targeting of oncogenic pathways of cHL may improve efficacy of DNA-demethylating therapy in cHL.

Patchett AL, Darby JM, Tovar C, et al.
The Immunomodulatory Small Molecule Imiquimod Induces Apoptosis in Devil Facial Tumour Cell Lines.
PLoS One. 2016; 11(12):e0168068 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
The survival of the Tasmanian devil (Sarcophilus harrisii) is threatened by devil facial tumour disease (DFTD). This transmissible cancer is usually fatal, and no successful treatments have been developed. In human studies, the small immunomodulatory molecule imiquimod is a successful immunotherapy, activating anti-tumour immunity via stimulation of toll-like receptor-7 (TLR7) signaling pathways. In addition, imiquimod is a potent inducer of apoptosis in human tumour cell lines via TLR7 independent mechanisms. Here we investigate the potential of imiquimod as a DFTD therapy through analysis of treated DFTD cell lines and Tasmanian devil fibroblasts. WST-8 proliferation assays and annexin V apoptosis assays were performed to monitor apoptosis, and changes to the expression of pro- and anti-apoptotic genes were analysed using qRT-PCR. Our results show that DFTD cell lines, but not Tasmanian devil fibroblasts, are sensitive to imiquimod-induced apoptosis in a time and concentration dependent manner. Induction of apoptosis was accompanied by down-regulation of the anti-apoptotic BCL2 and BCLXL genes, and up-regulation of the pro-apoptotic BIM gene. Continuous imiquimod treatment was required for these effects to occur. These results demonstrate that imiquimod can deregulate DFTD cell growth and survival in direct and targeted manner. In vivo, this may increase DFTD vulnerability to imiquimod-induced TLR7-mediated immune responses. Our findings have improved the current knowledge of imiquimod action in tumour cells for application to both DFTD and human cancer therapy.

Mauldin IS, Wages NA, Stowman AM, et al.
Topical treatment of melanoma metastases with imiquimod, plus administration of a cancer vaccine, promotes immune signatures in the metastases.
Cancer Immunol Immunother. 2016; 65(10):1201-12 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
INTRODUCTION: Infiltration of cancers by T cells is associated with improved patient survival and response to immune therapies; however, optimal approaches to induce T cell infiltration of tumors are not known. This study was designed to assess whether topical treatment of melanoma metastases with the TLR7 agonist imiquimod plus administration of a multipeptide cancer vaccine will improve immune cell infiltration of melanoma metastases.
PATIENTS AND METHODS: Eligible patients were immunized with a vaccine comprised of 12 melanoma peptides and a tetanus toxoid-derived helper peptide, and imiquimod was applied topically to metastatic tumors daily. Adverse events were recorded, and effects on the tumor microenvironment were evaluated from sequential tumor biopsies. T cell responses were assessed by IFNγ ELIspot assay and T cell tetramer staining. Patient tumors were evaluated for immune cell infiltration, cytokine and chemokine production, and gene expression.
RESULTS AND CONCLUSIONS: Four eligible patients were enrolled, and administration of imiquimod and vaccination were well tolerated. Circulating T cell responses to the vaccine was detected by ex vivo ELIspot assay in 3 of 4 patients. Treatment of metastases with imiquimod induced immune cell infiltration and favorable gene signatures in the patients with circulating T cell responses. This study supports further study of topical imiquimod combined with vaccines or other immune therapies for the treatment of melanoma.

Chen J, Katz LH, Muñoz NM, et al.
Vitamin D Deficiency Promotes Liver Tumor Growth in Transforming Growth Factor-β/Smad3-Deficient Mice Through Wnt and Toll-like Receptor 7 Pathway Modulation.
Sci Rep. 2016; 6:30217 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Disruption of the TGF-β pathway is associated with liver fibrosis and suppression of liver tumorigenesis, conditions associated with low Vitamin D (VD) levels. However, potential contributions of VD to liver tumor progression in the context of TGF-β signaling remain unexplored. Our analyses of VD deprivation (VDD) in in vivo models of liver tumor formation revealed striking three-fold increases in tumor burden in Smad3(+/-) mice, with a three-fold increase in TLR7 expression compared to controls. ChIP and transcriptional assays confirm Smad3 binding at two TLR7 promoter SBE sites. Molecular interactions between TGF-β pathway and VDD were validated clinically, where an absence of VD supplementation was associated with low TGF-β pathway member expression levels and β-catenin activation in fibrotic/cirrhotic human liver tissues. Subsequent supplementing VD led to restoration of TGF-β member expression with lower β-catenin levels. Bioinformatics analysis provides positive supportive correlation between somatic mutations for VD-related genes and the TGF-β pathway. We conclude that VDD promotes tumor growth in the context of Smad3 disruption, potentially through regulation of TLR7 expression and β-catenin activation. VD could therefore be a strong candidate for liver cancer prevention in the context of aberrant Smad3 signaling.

Sánchez-Cuaxospa M, Contreras-Ramos A, Pérez-Figueroa E, et al.
Low expression of Toll-like receptors in peripheral blood mononuclear cells of pediatric patients with acute lymphoblastic leukemia.
Int J Oncol. 2016; 49(2):675-81 [PubMed] Related Publications
Cancer is the second most common cause of death among children aged 1-14 years. Leukemia accounts for one-third of all childhood cancers, 78% of which is acute lymphoblastic leukemia (ALL). The development of cancer has been associated with malignant cells that express low levels of immunogenic molecules, which facilitates their escape from the antineoplastic immune response. It is thought that it may be possible to rescue the antineoplastic immune response through the activation of recognition receptors, such as Toll-like receptors (TLRs), which activate the innate immune system. TLRs are type I membrane glycoproteins expressed mainly in immune system cells such as monocytes, neutrophils, macrophages, dendritic cells, T, B and natural killer cells. The aim of the present study was to evaluate the expression of TLR1, TLR3, TLR4, TLR7 and TLR9 in peripheral blood mononuclear cells (PBMCs) in patients with ALL and prior to any treatment. PBMCs were obtained from 50 pediatric patients diagnosed with ALL and from 20 children attending the ophthalmology and orthopedics services. The mean fluorescence intensity was obtained by analysis of immunofluorescence. We found lower expression levels of TLR1, TLR3, TLR4, TLR7 and TLR9 in PBMCs from patients with ALL compared with those from control patients. We also observed that the PBMCs from patients with Pre-B and B ALL had lower TLR4 expression than controls and patients with Pro-B, Pre-B, B and T ALL had lower TLR7 expression than controls. The present study is the first to demonstrate reduced expression of TLRs in PBMCs from pediatric patients with ALL. This finding is of great relevance and may partly explain the reduction in the antineoplastic immune response in patients with ALL.

Huang SW, Chang SH, Mu SW, et al.
Imiquimod activates p53-dependent apoptosis in a human basal cell carcinoma cell line.
J Dermatol Sci. 2016; 81(3):182-91 [PubMed] Related Publications
BACKGROUND: The tumor suppressor p53 controls DNA repair, cell cycle, apoptosis, autophagy and numerous other cellular processes. Imiquimod (IMQ), a synthetic toll-like receptor (TLR) 7 ligand for the treatment of superficial basal cell carcinoma (BCC), eliminates cancer cells by activating cell-mediated immunity and directly inducing apoptosis and autophagy in cancer cells.
OBJECTIVE: To evaluate the role of p53 in IMQ-induced cell death in skin cancer cells.
METHODS: The expression, phosphorylation and subcellular localization of p53 were detected by real-time PCR, luciferase reporter assay, cycloheximide chase analysis, immunoblotting and immunocytochemistry. Using BCC/KMC1 cell line as a model, the upstream signaling of p53 activation was dissected by over-expression of TLR7/8, the addition of ROS scavenger, ATM/ATR inhibitors and pan-caspase inhibitor. The role of p53 in IMQ-induced apoptosis and autophagy was assessed by genetically silencing p53 and evaluated by a DNA content assay, immunoblotting, LC3 puncta detection and acridine orange staining.
RESULTS: IMQ induced p53 mRNA expression and protein accumulation, increased Ser15 phosphorylation, promoted nuclear translocation and up-regulated its target genes in skin cancer cells in a TLR7/8-independent manner. In BCC/KMC1 cells, the induction of p53 by IMQ was achieved through increased ROS production to stimulate the ATM/ATR-Chk1/Chk2 axis but was not mediated by inducing DNA damage. The pharmacological inhibition of ATM/ATR significantly suppressed IMQ-induced p53 activation and apoptosis. Silencing of p53 significantly decreased the IMQ-induced caspase cascade activation and apoptosis but enhanced autophagy. Mutant p53 skin cancer cell lines were more resistant to IMQ-induced apoptosis than wildtype p53 skin cancer cell lines.
CONCLUSION: IMQ induced ROS production to stimulate ATM/ATR pathways and contributed to p53-dependent apoptosis in a skin basal cell carcinoma cell line BCC/KMC1.

Wang F, Jin R, Zou BB, et al.
Activation of Toll-like receptor 7 regulates the expression of IFN-λ1, p53, PTEN, VEGF, TIMP-1 and MMP-9 in pancreatic cancer cells.
Mol Med Rep. 2016; 13(2):1807-12 [PubMed] Related Publications
Toll-like receptors (TLRs) are critical in the induction of the immune response in tumor development. TLR7 has previously been demonstrated to be associated with the development of pancreatic cancer, and the release of cytokines and chemokines from other types of cancer cell; however, the specific expression induced by TLR7 agonists in pancreatic cancer cells remains to be elucidated. The present study aimed to investigate the effects of the TLR7 agonist, gardiquimod, on ERK1/2 signaling pathway, and on the expression of genes involved in the pathogenesis of cancer, including phosphatase and tensin homolog deleted on chromosome 10 (PTEN), p53, type Ⅲ interferon (IFN-λ1), vascular endothelial growth factor (VEGF), matrix metalloproteinase 9 (MMP-9) and tissue inhibitor of metalloproteinase 1 (TIMP-1). The results demonstrated that activation of TLR7 upregulated the expression levels of certain genes to varying degrees; the expression levels of IFN-λ1 and MMP-9 were increased by ~3 fold, whereas other genes (p53, PTEN, TIMP-1) were upregulated by ~2 fold, and VEGF was marginally upregulated after 10 min. Furthermore, gardiquimod increased the expression levels of phosphorylated-extracellular signal-regulated kinase (ERK)1/2. In addition, PD98059, a specific inhibitor of ERK phosphorylation, inhibited the ability of gardiquimod to activate ERK1/2; consequently weakening the effect of gardiquimod on gene regulation. These findings indicated that the effect of TLR7 agonists, including gardiquimod, on gene expression in BxPC-3 pancreatic cancer cells was partly associated with the mitogen-activated protein kinase-ERK1/2 signaling pathway.

Sampey GC, Saifuddin M, Schwab A, et al.
Exosomes from HIV-1-infected Cells Stimulate Production of Pro-inflammatory Cytokines through Trans-activating Response (TAR) RNA.
J Biol Chem. 2016; 291(3):1251-66 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
HIV-1 infection results in a chronic illness because long-term highly active antiretroviral therapy can lower viral titers to an undetectable level. However, discontinuation of therapy rapidly increases virus burden. Moreover, patients under highly active antiretroviral therapy frequently develop various metabolic disorders, neurocognitive abnormalities, and cardiovascular diseases. We have previously shown that exosomes containing trans-activating response (TAR) element RNA enhance susceptibility of undifferentiated naive cells to HIV-1 infection. This study indicates that exosomes from HIV-1-infected primary cells are highly abundant with TAR RNA as detected by RT-real time PCR. Interestingly, up to a million copies of TAR RNA/μl were also detected in the serum from HIV-1-infected humanized mice suggesting that TAR RNA may be stable in vivo. Incubation of exosomes from HIV-1-infected cells with primary macrophages resulted in a dramatic increase of proinflammatory cytokines, IL-6 and TNF-β, indicating that exosomes containing TAR RNA could play a direct role in control of cytokine gene expression. The intact TAR molecule was able to bind to PKR and TLR3 effectively, whereas the 5' and 3' stems (TAR microRNAs) bound best to TLR7 and -8 and none to PKR. Binding of TAR to PKR did not result in its phosphorylation, and therefore, TAR may be a dominant negative decoy molecule in cells. The TLR binding through either TAR RNA or TAR microRNA potentially can activate the NF-κB pathway and regulate cytokine expression. Collectively, these results imply that exosomes containing TAR RNA could directly affect the proinflammatory cytokine gene expression and may explain a possible mechanism of inflammation observed in HIV-1-infected patients under cART.

Akhter A, Street L, Ghosh S, et al.
Concomitant high expression of Toll-like receptor (TLR) and B-cell receptor (BCR) signalling molecules has clinical implications in mantle cell lymphoma.
Hematol Oncol. 2017; 35(1):79-86 [PubMed] Related Publications
Mantle cell lymphoma (MCL) is an aggressive disease with frequent relapse. Targeted therapies against B-cell receptor (BCR) molecules have demonstrated improved outcomes in relapsed cases. However, clinical responses are slow and selective, with failure to attain complete remission in a significant subset of patients. Complex interaction of BCR signal transduction with toll-like receptor (TLR) and other pathways in MCL remains unknown, thus averting progress in development of targeted therapies. We have performed detailed digital quantification of BCR/TLR signalling molecules and their effector pathways in a cohort (n = 81) of MCL patients and correlated these data with overall survival. Hierarchical clustering model based on BCR/TLR genes revealed two distinct (BCR

Fonte E, Agathangelidis A, Reverberi D, et al.
Toll-like receptor stimulation in splenic marginal zone lymphoma can modulate cell signaling, activation and proliferation.
Haematologica. 2015; 100(11):1460-8 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Recent studies on splenic marginal zone lymphoma identified distinct mutations in genes belonging to the B-cell receptor and Toll-like receptor signaling pathways, thus pointing to their potential implication in the biology of the disease. However, limited data is available regarding the exact role of TLRs. We aimed at characterizing the expression pattern of TLRs in splenic marginal zone lymphoma cells and their functional impact on the activation, proliferation and viability of malignant cells in vitro. Cells expressed significant levels of TLR1, TLR6, TLR7, TLR8, TLR9 and TLR10 mRNA; TLR2 and TLR4 showed a low, variable pattern of expression among patients whereas TLR3 and TLR5 mRNAs were undetectable; mRNA specific for TLR signaling molecules and adapters was also expressed. At the protein level, TLR1, TLR6, TLR7, TLR9 and TLR10 were detected. Stimulation of TLR1/2, TLR2/6 and TLR9 with their respective ligands triggered the activation of IRAK kinases, MAPK and NF-κB signaling pathways, and the induction of CD86 and CD25 activation molecules, although in a heterogeneous manner among different patient samples. TLR-induced activation and cell viability were also inhibited by a specific IRAK1/4 inhibitor, thus strongly supporting the specific role of TLR signaling in these processes. Furthermore, TLR2/6 and TLR9 stimulation also significantly increased cell proliferation. In conclusion, we demonstrate that splenic marginal zone lymphoma cells are equipped with functional TLR and signaling molecules and that the stimulation of TLR1/2, TLR2/6 and TLR9 may play a role in regulating disease pathobiology, likely promoting the expansion of the neoplastic clone.

Yu DS, Wu CL, Ping SY, et al.
Bacille Calmette-Guerin can induce cellular apoptosis of urothelial cancer directly through toll-like receptor 7 activation.
Kaohsiung J Med Sci. 2015; 31(8):391-7 [PubMed] Related Publications
Immunotherapy using bacille Calmette-Guerin (BCG) instillation is the mainstay treatment modality for superficial urothelial cancer (UC) through toll-like receptor (TLR) activation of cognitive immune response. We investigated the roles of TLR7 in the activation of apoptosis in UC cells after BCG treatment. The in vitro cytotoxicity effect of BCG on UC cells was measured by a modified 3-(4,5-dimethylthiazo-2-yl)-2,5-diphenyl tetrazolium assay. Expressions of TLR7 mRNA and protein in native UC cells prior to and after BCG treatment were analyzed using real-time quantitative polymerase chain reaction and western blot methods. Phagocytotic processes after BCG treatment in UC cells were observed microscopically using a specific immunostain, subsequent cellular apoptosis-related signals induced by TLR7 were analyzed by western blot. Low-grade UC cells, TSGH8301, showed significant cellular death (4.23-fold higher than the high-grade UC cells T24 and J82) when treated with BCG and the BCG cytotoxicity was displayed in a dose-time-dependent manner. TSGH8301 cells had the highest content of TLR7 mRNA, 7.2- and 4.5-fold higher than that of T24 and J82 cells, respectively. TLR7 protein expression was also significantly increased in TSGH8301 cells. Phagocytosis-related markers, including beclin 1, ATG2, and LC3, were increased when TSGH8301 cells were treated by BCG. Interleukin-1 receptor-associated kinases 2 and 4 were also increased markedly in TSGH8301 cells. On the contrary, cellular apoptosis of TSGH8301 cells decreased by 34% when TLR7 activation was suppressed by the TLR antagonist IRS661 after BCG treatment. Our findings suggest that well differentiated TCC cells have higher expression of TLR7 and BCG can drive cellular death of TCC cells directly via TLR7 activation and related apoptotic pathway.

Li Y, Shi Y, McCaw L, et al.
Microenvironmental interleukin-6 suppresses toll-like receptor signaling in human leukemia cells through miR-17/19A.
Blood. 2015; 126(6):766-78 [PubMed] Related Publications
The regulation of toll-like receptor (TLR) signaling in a tumor microenvironment is poorly understood despite its importance in cancer biology. To address this problem, TLR7-responses of chronic lymphocytic leukemia (CLL) cells were studied in the presence and absence of a human stromal cell-line derived from a leukemic spleen. CLL cells alone produced high levels of tumor necrosis factor (TNF)-α and proliferated in response to TLR7-agonists. A signal transducer and activator of transcription 3 -activating stromal factor, identified as interleukin (IL)-6, was found to upregulate microRNA (miR)-17 and miR-19a, target TLR7 and TNFA messenger RNA, and induce a state of tolerance to TLR7-agonists in CLL cells. Overexpression of the miR-17-92 cluster tolerized CLL cells directly and miR-17 and miR-19a antagomiRs restored TLR7-signaling. Inhibition of IL-6 signaling with antibodies or small-molecule Janus kinase inhibitors reversed tolerization and increased TLR7-stimulated CLL cell numbers in vitro and in NOD-SCIDγc (null) mice. These results suggest IL-6 can act as tumor suppressor in CLL by inhibiting TLR-signaling.

Lee J, Tian Y, Chan ST, et al.
TNF-α Induced by Hepatitis C Virus via TLR7 and TLR8 in Hepatocytes Supports Interferon Signaling via an Autocrine Mechanism.
PLoS Pathog. 2015; 11(5):e1004937 [PubMed] Article available free on PMC after 01/12/2019 Related Publications
Invasion by infectious pathogens can elicit a range of cytokine responses from host cells. These cytokines provide the initial host defense mechanism. In this report, we demonstrate that TNF-α, a pro-inflammatory cytokine, can be induced by hepatitis C virus (HCV) in its host cells in a biphasic manner. The initial induction of TNF-α by HCV was prompt and could be blocked by the antibody directed against the HCV E2 envelope protein and by chemicals that inhibit endocytosis, indicating the specificity of endocytic uptake of HCV in this induction. Further studies indicated that the induction of TNF-α was dependent on toll-like receptors 7 and 8 (TLR7/8) but not on other intracellular pattern recognition receptors. Consistently, siRNA-mediated gene silencing of the downstream effectors in the TLR7/8 signaling pathway including MyD88, IRAK1, TRAF6, TAK1 and p65 NF-κB suppressed the expression of TNF-α. The role of p65 NF-κB in the induction of TNF-α via transcriptional up-regulation was further confirmed by the chromatin immunoprecipitation assay. TNF-α induced by HCV could activate its own receptor TNFR1 on hepatocytes to suppress HCV replication. This suppressive effect of TNF-α on HCV was due to its role in supporting interferon signaling, as the suppression of its expression led to the loss of IFNAR2 and impaired interferon signaling and the induction of interferon-stimulated genes. In conclusion, our results indicate that hepatocytes can sense HCV infection via TLR7/8 to induce the expression of TNF-α, which inhibits HCV replication via an autocrine mechanism to support interferon signaling.

Jouhi L, Koljonen V, Böhling T, et al.
The expression of Toll-like receptors 2, 4, 5, 7 and 9 in Merkel cell carcinoma.
Anticancer Res. 2015; 35(4):1843-9 [PubMed] Related Publications
AIM: We sought to clarify whether the expression of toll-like receptors (TLR) in Merkel cell carcinoma (MCC) is linked to tumor and patient characteristics, especially the presence of Merkel cell polyoma virus (MCV).
MATERIALS AND METHODS: The study comprised of 128 patients with data on Merkel cell polyomavirus (MCV) status and clinical features were included in the study. Immunohistochemistry for TLR expression was performed on tissue microarray (TMA) slides.
RESULTS: TLR 2, 4, 5, 7 and 9 expression was noted in most of the tumor specimens. Decreased expression of TLR 9 correlated strongly with MCV positivity. Cytoplasmic TLR 2 expression correlated with small tumor size, while nuclear TLR 2 and TLR 5 expressions with larger tumors. Increased nuclear TLR 4 expression and decreased TLR 7 expression were associated with older age.
CONCLUSION: TLR 2, 4, 5, 7 and 9 appear to reflect certain clinicopathological variables and prognostic markers of MCC tumors.

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