Steroid Receptor Coactmvator-3 Promotes Bladder Cancer Through Up Regulation Of CXCR4

Objectives: To explore the expression of steroid receptor coactivator-3(SRC-3) in bladder cancer and its effect and mechanism on cell proliferation of bladder cancer。Material and Methods: We chose 28 paired bladder cancer tissues and normal bladder tissues. Quantitative real time polymerase chain reaction(q RT-PCR) was used to detect the expression of SCR-3 m RNA in these paired tissues. SRC-3 protein in bladder cancer tissues were tested by western blot. Then we constructed adenovirus vector(full name: tumor-specific replicationdefective adenovirus type 5) contained SRC-3(Ad5-SRC-3) and transfected EJ and T24 cells. q RT-PCR and western blot to verify whether SRC-3 m RNA and protein were overexpressed or interfered. Cell proliferation was detected by Brd U assay after stable overexpressed SRC-3 cell line was constructed or transfected with SRC-3 si RNA. In order to illustrate the mechanism behind these effect, we performed q RT-PCR and western blot to examine the expression of CXCR4 m RNA and protein after over-expressed SRC-3 and silence of SRC-3. Finally, CXCR4 si RNA oligos were transfected into EJ cells that stable overespressed SRC-3 and cell proliferation were tested by Brd U assay.Results: We found SRC-3 expression in 28 paired bladder cancer tissues and adjacent non-tumor liver tissues by way of real-time PCR( P<0.01). Cell proliferation was enhanced by SRC-3 overexpression as measured bybromodeoxyuridine(Brd U) analysis(P<0.05). Moreover, EJ cells were transfected with small interfering RNA(si RNA) targeting SRC-3. As a result, down- regulation of SRC-3 led to a marked decrease in cell proliferation in these cells(P<0.05). Overexpression of SRC-3 increased CXCR4 m RNA and protein levels(P<0.01). In agreement, SRC-3 depletion dramatically led to a reduction of CXCR4 expression(P<0.05), suggesting that SRC-3 is an upstream regulator of CXCR4. Next, to determine if induction of CXCR4 is required for the proliferative effect of SRC-3, we carried out experiments with CXCR4knockdown using si RNA oligos. As a result, the si RNA rescued cells from the effect of SRC-3 on cell proliferation in EJ cells.Conclusions: SRC-3 overexpressed in bladder cancer and promotes the cell proliferation by upregulating CXCR4.