Developmentally regulated GTP-binding protein 2 levels in prostate cancer cell lines impact docetaxel-induced apoptosis

Abstract

Purpose This study aimed to confirm the association between developmentally regulated GTP-binding protein 2 (DRG2) expression and docetaxel-induced apoptosis and to determine whether prostate cancer responses to docetaxel treatment differ with DRG2 expression. Materials and Methods PC3, DU145, and LNCaP prostate cancer cell lines were used. The MTT assay was used to determine cell viability. Western blotting analysis was performed using anti-DRG2 antibodies. Cells were transfected with 50 nmol DRG2 siRNA using an siRNA transfection reagent for DRG2 knockdown. The cell cycle was analyzed by using flow cytometry, and apoptosis was detected by using the Annexin V cell death assay. Results DRG2 expression differed in each prostate cancer cell line. Docetaxel reduced DRG2 expression in a dose-dependent manner. Upon DRG2 knockdown in prostate cancer cells, an increase in the sub-G1 phase was observed without a change in the G1 or G2/M phases. When 4 nM docetaxel was administered to DRG2 knockdown prostate cancer cell lines, an increase in the sub-G1 phase was observed without increasing the G2/M phase, which was similar to that in DU145 cells before DRG2 knockdown. In PC3 and DU145 cell lines, DRG2 knockdown increased docetaxel-induced Annexin V (+) apoptosis by 8.7 and 2.7 times, respectively. Conclusions In prostate cancer cells, DRG2 regulates G2/M arrest after docetaxel treatment. In prostate cancer cells with DRG2 knockdown, apoptosis increases without G2/M arrest in response to docetaxel treatment. These results show that inhibition of DRG2 expression can be useful to enhance docetaxel-induced apoptosis despite low-dose administration in castration-resistant prostate cancer.

DRG2 levels in prostate cancer cell lines predict response to PARP inhibitor

“…Cells that experienced DNA stress but escaped the G1 checkpoint undergo G2/M arrest [14]. In addition, arrest at the G2/M phase increases in cells with higher expression of DRG2 [7] Notably, DRG2 translocates to the nucleus in case of DNA damage. Therefore, DRG2 may mediate cell arrest under DNA stress conditions.…”

“…DRG2 plays an important role in G2/M arrest [7]. Therefore, it was expected that G2/M arrest would increase when DNA damage was induced in cells with high DRG2 expression.…”

“…These PARP inhibitors are effective in cells, which have undergone G2/M phase arrest [4]. Moreover, we previously con rmed that cells undergo G2/M arrest due to the expression of developmentally regulated GTP-binding protein 2 (DRG2), caused by docetaxel treatment [7]. As G2/M arrest was observed after docetaxel treatment in cells expressing DRG2, we hypothesized that treatment with a PARP inhibitor would be effective.…”