Objective:To evaluate the effect of ribosomal protein L34 (RPL34) gene knockdown on the proliferation and apoptosis of human cutaneous squamous cell carcinoma (cSCC) cells.Methods:From January 2016 to January 2017, 14 paraffin-embedded skin samples of cSCC and 16 paraffin-embedded normal skin tissue samples were collected from Department of Dermatology and Venereology, the Affiliated Hospital of Inner Mongolia Medical University, and RPL34 expression in the skin tissues was analyzed by immunohistochemical study. A lentivirus vector containing short hairpin RNA targeting RPL34 gene was constructed and used to transfect a human cSCC cell line SCL-1 (shRNA group) , SCL-1 cells transfected with an empty lentivirus vector served as control group, and the knockdown efficiency was verified by real-time quantitative PCR (RT-PCR) and Western blot analysis. At 72 hours after the transfection, flow cytometry was performed to analyze the cell cycle and detect apoptosis of SCL-1 cells, and methyl thiazolyl tetrazolium (MTT) assay to evaluate the cellular proliferative activity of SCL-1 cells. Comparisons between 2 groups were performed by using t test or rank sum test. Results:Immunohistochemical study showed that the cytoplasmic expression score of RPL34 was significantly higher in the cSCC tissues (2.143±1.956) than in the normal control tissues (0.500±0.516, z=3.53, P< 0.05) . RT-PCR showed that the relative mRNA expression of RPL34 in the SCL-1 cells was significantly lower in the shRNA group (0.149±0.016) than in the control group (1±0.018, t=36.95, P< 0.05) ; Western blot analysis revealed that the relative protein expression of RPL34 in the SCL-1 cells was significantly lower in the shRNA group than in the control group. Compared with the control group, the shRNA group showed a significantly increased proportion of S-phase cells ( t=13.76, P< 0.05) , but a significantly decreased proportion of G1-phase cells ( t=36.62, P< 0.05) ; the apoptosis rate was significantly higher in the shRNA group (9.42%±0.16%) than in the control group (4.58%±0.41%, t=19.02, P< 0.05) . MTT assay showed that the cell viability was significantly decreased in the shRNA group (0.815±0.005) than in the control group (1.886±0.005, t=265.91, P< 0.05) after additional 120-hour culture. Conclusion:The RPL34 gene was overexpressed in the cSCC tissues, and knockdown of the RPL34 gene in SCL-1 cells could interfere with cell cycle, decrease their proliferative activity, and promote their apoptosis.

Arsenic is a kind of non-metallic substance with carcinogenic effect, which widely exists in the natural environment. Chronic arsenic exposure will cause a series of health damage involving multiple organs of the whole body. Because of its unclear pathogenesis, lack of specific drugs and early biomarkers, it has become the focus and hotspot of scientific and technological workers for a long time. Epigenetic modification not only correlates with arsenic exposure, but also participates in early arsenic-induced damage by regulating the expression of key molecules, which has become an important research direction of arsenic exposure mechanism. As one of the important modes of epigenetic modification, DNA methylation is expected to provide a new therapeutic target for endemic arsenism. However, how DNA methylation regulates the expression of key genes induced by arsenic and participates in the occurrence and development of arsenism and its relationship with the mechanism of arsenism need to be further studied. The research progress of DNA methylation in the pathogenesis of arsenism is reviewed.