Anti-tumor activity of olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, in cultured endometrial carcinoma cells

Abstract

BackgroundPTEN inactivation is the most frequent genetic aberration in endometrial cancer. One of the phosphatase-independent roles of PTEN is associated with homologous recombination (HR) in nucleus. Poly (ADP-ribose) polymerase (PARP) plays key roles in the repair of DNA single-strand breaks, and a PARP inhibitor induces synthetic lethality in cancer cells with HR deficiency. We examined the anti-tumor activity of olaparib, a PARP inhibitor, and its correlation between the sensitivity and status of PTEN in endometrial cancer cell lines.MethodsThe response to olaparib was evaluated using a clonogenic assay with SF50 values (concentration to inhibit cell survival to 50%) in 16 endometrial cancer cell lines. The effects of PTEN on the sensitivity to olaparib and ionizing radiation (IR) exposure were compared between parental HEC-6 (PTEN-null) and HEC-6 PTEN + (stably expressing wild-type PTEN) cells by clonogenic assay, foci formation of RAD51 and γH2AX, and induction of cleaved PARP. The effects of siRNA to PTEN were analyzed in cells with wild-type PTEN.ResultsThe SF50 values were 100 nM or less in four (25%: sensitive) cell lines; whereas, SF50 values were 1,000 nM or more in four (25%: resistant) cell lines. PTEN mutations were not associated with sensitivity to olaparib (Mutant [n = 12]: 746 ± 838 nM; Wild-type [n = 4]: 215 ± 85 nM, p = 0.26 by Student’s t test). RAD51 expression was observed broadly and was not associated with PTEN status in the 16 cell lines. The number of colonies in the clonogenic assay, the foci formation of RAD51 and γH2AX, and the induction of apoptosis were not affected by PTEN introduction in the HEC-6 PTEN + cells. The expression level of nuclear PTEN was not elevated within 24 h following IR in the HEC-6-PTEN + cells. In addition, knocking down PTEN by siRNA did not alter the sensitivity to olaparib in 2 cell lines with wild-type PTEN.ConclusionsOur results suggest that olaparib, a PARP inhibitor, is effective on certain endometrial cancer cell lines. Inactivation of PTEN might not affect the DNA repair function. Predictive biomarkers are warranted to utilize olaparib in endometrial cancer.

Putative tumor suppression function of SIRT6 in endometrial cancer

“…We utilized 16 endometrial cancer cell lines as previously described [29]. Ishikawa cells were generous gifts from Dr. Masato Nishida (National Hospital Organization Kasumigaura Medical Center, Ibaraki, Japan).…”

Current recommendations and recent progress in endometrial cancer

“…ARID1A deficiency impairs homologous recombination DNA repair, which is associated with PARP sensitivity . There are data suggesting sensitivity to PARP inhibition in endometrial cancer cell lines and mouse models . One ongoing, randomized, phase 2 study, NRG Oncology trial NRG‐GY012 (ClinicalTrials.gov identifier NCT03660826) compares single‐agent olaparib (a PARP inhibitor) with single‐agent cediranib (an oral tyrosine kinase inhibitor targeting VEGF receptor [VEGFR], platelet‐derived growth factor receptors [PDGFRs], and FGFR) and with the combination of both agents in women who have metastatic/recurrent endometrial cancer.…”

The role of poly(ADP-ribose) polymerase inhibitors in the treatment of endometrial cancer: a scoping review of the current literature

“…Of the studies selected for analysis, 4 were in vitro [14,[32][33][34], 2 were in vivo [35,36], 6 were reviews [3,7,[37][38][39][40], and 5 were clinical trials.…”

“…In a more recent paper, investigators from Japan, using endometrial cancer cell lines, evaluated the correlation between PTEN status and olaparib sensitivity [32]. Endometrial cancer cell lines, PTEN-null and wild-type PTEN, were exposed to olaparib at varying concentrations, for 2-3 weeks and the concentration to inhibit cell survival to 50% (SF50) was calculated.…”