PARP inhibition sensitizes endometrial cancer cells to paclitaxel-induced apoptosis

Abstract

PARP inhibitors are used in the treatment of gynecological malignancies and it has been demonstrated in preclinical studies that PARP inhibition sensitizes cancer cells to cytotoxic agents. In the present study, PARP expression was detected in different endometrial cancer cell lines by western blot analysis, and PARP activity was measured using an enzymatic assay. In addition, the endometrial cancer cell lines were treated with paclitaxel or carboplatin in combination with the PARP inhibitor PJ34 prior to a cell viability assay and apoptotic nuclei measurement. PARP protein was detected in all four cell lines examined, although its activity varied between the cell lines. Treatment with PJ34 in combination with paclitaxel decreased endometrial cancer cell viability compared with treatment with paclitaxel alone. These results indicate that the inhibition of PARP with PJ34 sensitizes endometrial cancer cells to cytotoxic treatment with paclitaxel.

Keywords: apoptosis; endometrial cancer; paclitaxel; poly (ADP-ribose) polymerase inhibition; proliferation.

Figure 1.

Western blot analysis of PARP, PTEN and Akt expression. PTEN was detected in HEC1-A and KLE cells, furthermore weak bands were observed in AN3CA and RL95-2 cell lines. PARP and Akt were detected in all cell lines, and p-Akt was detected in cell lines without or little PTEN. Lanes: A, AN3CA; H, HEC-1A; K, KLE; and R, RL95-2. PARP, poly (ADP-ribose) polymerase; PTEN, phosphatase and tensin homolog; Akt, AKT serine/threonine kinase; p, phosphorylated.

Figure 2.

PARP activity assay. A significant decrease in PARP activity was detected following treatment with PJ34 in KLE and RL95-2 cells. *P<0.05 vs. untreated cells. PARP, poly (ADP-ribose) polymerase.

Figure 3.

Viability of endometrial cancer cells following treatment with paclitaxel and/or PJ34. The combination of 0.1 nM paclitaxel and 10 µM PJ34 decreased AN3CA and HEC-1A cell viability compared with the treatment with paclitaxel alone. PTX, paclitaxel.

Figure 4.

Detection of apoptotic nuclei. There was a significant increase in apoptotic nuclei in the endometrial cancer cell lines AN3-CA and HEC-1A following treatment with a combination of paclitaxel and PJ34. *P<0.05 vs. untreated cells; ^#P<0.05 vs. PTX treatment alone. PTX, paclitaxel.