Study Of Ubiquitin E3 Ligase DTL In Promoting The Proliferation Of Breast Cancer Cells

Breast cancer is a serious threat to women’s health in the worldwide with high death rate. Although the therapeutic effect of breast cancer continues to improve, there are still a considerable part of patients with relapse or drug resistance. In an attempt to identify novel molecular targets for breast cancer therapy, we focused on characterization of DTL (denticleless E3 ubiquitin protein ligase) based on the gene-expression profiles analysed in breast cancer cells.To explore the role of DTL in breast cancer cells, quantitative RT-PCR and western blot analyses firstly confirmed expression of DTL in the majority of breast cancer cells, finding that DTL is high expressed in breast cancer cells. The subcellular localization of DTL was observed by immunofluorescence and laser scanning confocal microscopy. Then cell proliferation was detected by MTT assay and Brdu, and it is found that DTL could significantly promote cell proliferation. We hypothesized that DTL might play the role by regulation of cell cycle. So we observed the changes of cell cycle by flow cytometry after transfection of siRNA-DTL in MCF-7 and MDA-MB-231 cells, and found a downregulation of G1 and upregulation of G2/M. To further validate these results, we detected the expression of mutiple cell cycle proteins, protein kinases and protein kinase inhibitors by Q-PCR, and found an upregulation of P21 in MCF-7 when transfection of siRNA-DTL, but not the same in MDA-MB-231. It shows that DTL effects on cell cycle may play the role by regulating the expression of P21, but its mechanism remains to be further studied. The mechanisms of DTL function might be different in different cells, which need to be furthervalidated.In conclusion, in this study we found that the DTL is high expressed in various types of breast cancer cells. Transfected with siRNA-DTL can inhibit proliferation of breast cancer cell and led to cell cycle arrest in G2/M phase. DTL might promote cell proliferation of MCF-7 by inhibiting the expression of P21. So DTL may be a potential therapeutic target for breast cancer.