Colorectal cancer, also known as colon cancer is the most devastating malignancy worldwide. Previous studies have reported that Nit2, a member of the nitrilase superfamily, is a potential tumor suppressor, although its function remains elusive in colon cancer. In the present study, we employed an RNA interference lentivirus system to silence endogenous NIT2 expression in the colon cancer cell line, HCT116. The knockdown efficiency was determined by RT-qPCR and western blot analysis. The depletion of NIT2 markedly inhibited colon cancer cell proliferation and colony formation and induced cell cycle arrest in the G0/G1 phase, as shown by MTT assay, colony formation assay and flow cytometric analysis, respectively. Further investigation with an intracellular signaling array demonstrated that the depletion of NIT2 triggered the apoptosis of colon cancer cells through the caspase-3 and poly(ADP-ribose) polymerase (PARP) pathways. Our findings suggest that NIT2 may be an oncogene in human colon cancer and may thus serve as a promising therapeutic target for the treatment of colon cancer.

The mammalian nitrilase (Nit) protein is a member of the nitrilase superfamily whose function remains to be characterized. We now show that the nitrilase family member 2 gene (NIT2) is ubiquitously expressed in multiple tissues and encodes protein mainly distributed in the cytosol. Ectopic expression of Nit2 in HeLa cells was found to inhibit cell growth through G(2) arrest rather than by apoptosis. Consistent with this, proteomic and RT-PCR analyses showed that Nit2 up-regulated the protein and mRNA levels of 14-3-3sigma, an inhibitor of both G(2)/M progression and protein kinase B (Akt)-activated cell growth, and down-regulated 14-3-3beta, a potential oncogenic protein. Genotype analysis in four types of primary tumor tissues showed 12.5-38.5% allelic imbalance surrounding the NIT2 locus. The results demonstrated that NIT2 plays an important role in cell growth inhibition and links to human malignancies, suggesting that Nit2 may be a potential tumor suppressor candidate.