Rab23 Inhibits The Growth And Proliferation Of Breast Cancer Cells Through Inhibitating Hedgehog Signaling Pathway

【Background】Breast cancer is one of the most fatal malignancies affecting women worldwide.Previous researches and the reports confirm that breast cancer is associated withabnormal activity of hedgehog (Hh) signaling pathway. Rab23 is a new negativeregulator of hedgehog which was found in 2001. Some researches indicate thatRab23 is downstream of Smo, and upstream of Gli proteins, and may block themessage of transfering to Gli in the Hh signaling pathway. In the present study, wefirst describe that Rab23 expresses in breast cancer cell lines, and inhibits breastcancer cells proliferation and DNA synthesis. Moreover, the results suggest that theinhibition of Rab23 to breast cancer cells has not relationship with breast cancer'scharacteristics of hormone-dependent. The studies further enrich pathogenesis ofbreast cancer and provide a new treatment to breast cancer. 【Aims】To identify whether Rab23 is expressed in breast cancer cells and to investigatethe effect and mechanism of Rab23 on growth and proliferation of breast cancercells thought Hh signaling pathway.【Methods】1. Immunofluorescence and RT-PCR methods were used to observe theexpression of Rab23 in three breast cancer cell lines and a normal breast cellline HBL-100 cell.2. Rab23 gene expression was regulated by transfection plasmid and RNAi.3. The effect of Rab23 on growth and proliferation of breast cancer cells wasmeasured by colony formation assay, and MTT assay.4. Incorporation efficiency of BrdU was used to detect the effect of Rab23 toefficiency of DNA synthesis in breast cancer cells.5. The flow cytometry assay was used to investigate the effect of Rab23 on thecell apoptosis of breast cancer cells.6. RT-PCR was used to observe the expression of Gli1 and Gli2 in three breastcancer cell lines when Hh was regulated by Rab23.【Results】1. As the results of RT-PCR showed, Rab23 mRNA was expressed in all ofbreast cancer cell lines and normal breast cell line. The expression of Rab23mRNA in MDA-MB-231 and Bcap-37 was higher than the others(P＜0.05),but there was no statistical difference observed between them(P＞0.05). Theexpression of Rab23 mRNA in HBL-100 was more than that in MCF-7.2. As the results of immunofluorescence showed, Rab23 protein was primarily expressed and localized in the cytoplasm surrounding the nucleus.3. As the results of colony formation showed, up-regulation of Rab23 mayreduce the number of colony formation of three cell lines and up-regulation ofGli1 increase the number of colony formation.4. As the results of BrdU labeling showed, up-regulation of Rab23 may inhibitthe efficiency of DNA synthesis in breast cancer cells, and down-regulation ofRab23 has the opposite effect on the efficiency of DNA synthesis.5. As the results of MTT showed, up-regulation of Rab23 may inhibit the growthof breast cancer cells, while down-regulation of Rab23 may promote the growthof breast cancer cells.6. As the results of flow cytometry assay showed, up-regulation of Rab23 caninduce the cell apoptosis of breast cancer cells.7. As the results of RT-PCR showed, up-regulation of Rab23 may reduce theexpression of Gli1 and Gli2 in three breast cancer cells.【Conclusions】1. Rab23 is expressed in the breast cancer cell lines and normal breast cell line.2. Rab23 inhibits breast cancer cells proliferation and DNA synthesis.3. Rab23 inhibits the activity of hedgehog signaling pathway, and it may be anew target to treat breast cancer.