Combined treatment using the anti-p53 drug, APR-246 and eribulin: Synergistic growth inhibition in p53-mutated breast cancer cells.

Abstract

e14098 Background: TP53 is the most frequently mutated gene in triple-negative breast cancer, being present in approximately 80% of cases. APR-246 is a novel anticancer drug that acts by reactivating the mutant p53 protein, thereby converting it to a form with wild-type properties. Previously, we showed that APR-246 had antiproliferative, anti-migratory and pro-apoptotic activities in a panel of 23 breast cancer cell lines, including triple-negative (TN) cell lines. The aim of this study was to investigate if combined treatment with APR-246 and different cytotoxic agents resulted in enhanced growth inhibition. Methods: Cell viability was determined using the MTT assay. Combination index (CI) values were calculated using Calcusyn software, based on the Chou-Talalay method. Apoptosis was detected using Annexin V-FITC Apoptosis Detection Kit followed by FACs analysis. Results: Highly synergistic cell growth inhibition was found when APR-246 was combined with eribulin (Eisai Ltd.) in 6 different p53-mutated cell lines (mean CI values range from 0.38 to 0.77). In contrast, enhanced growth inhibition was not found using this combination in the 3 p53-WT cell lines investigated (mean CI values ranged from 1.13 to 2.9). Overall, p53 mutated cell lines had a significantly lower CI values than p53 wild-type cells (p = 0.008). In all the 4 p53-mutated cell lines investigated, a significant increase in apoptosis was also seen when APR-246 was combined with eribulin. This enhanced apoptosis appeared to result from increased mRNA expression of the pro-apoptotic factors PUMA and NOXA by the drug combination compared to either compound alone. In contrast to our findings with eribulin, combined treatment with APR-246 plus docetaxel, doxorubicin, cisplatin or carboplatin was cell line-dependent. Thus, docetaxel plus APR-246 was synergistic in 1/6 cell lines, while doxorubicin, cisplatin or carboplatin plus APR-246 was synergistic in 3/6 cell lines. Conclusions: Clinical trials investigating the combination of APR-246 and eribulin should be considered in patients with a p53 mutation such as triple-negative breast cancer.