Abstract 2523: Strong synergistic effects with APR-246 and cisplatin in p53-mutant lung cancer cells
Authors: Mohell Nina , Fransson Åsa , Alfredsson Jessica , von Euler Mikael , Björklund Ulf , Abrahmsen Lars 
Published: August 2015

Abstract
Background: Platinum compounds have been used as first-line treatment for many solid tumors including non small cell (NSCLC) and small cell (SCLC) lung cancer. However, patients with lung cancer often develop resistance to platinum compounds and eventually die of chemotherapy refractory disease. Mutation in the tumor suppressor protein p53 is common in lung cancer, ranging from 33% in adenocarcinomas to 70% in SCLC (The p53 website, http://p53.free.fr), and is one of the main causes for resistance to chemotherapy. APR-246 (PRIMA-1MET) is the first compound in clinical development that reactivates mutant p53 by inducing its wild type conformation thus triggering apoptosis (Lambert et al. Cancer Cell 15, 2009). APR-246 has yielded promising results in a first-in-human clinical trial in patients with hematological malignancies and prostate cancer (Lehmann et al. J Clin Oncol 30, 2012), and a Phase Ib/II study in combination with platinum-based therapy in ovarian cancer is ongoing. Previously we have shown strong synergy with APR-246 and platinum compounds in p53-mutant drug-resistant ovarian cancer cells (AACR abstract # 3448, 2013). Moreover, APR-246 completely restored the sensitivity of cisplatin to resistant p53-mutant ovarian cancer cells (AACR abstract #1801, 2014). The aim of the current study was to investigate whether strong synergistic effect can also be observed in p53-mutant lung cancer cells. Methods: Cell viability was determined with FMCA or Cell Titer-Glo assay, p53 gene status by Sanger sequencing and single strand conformation analysis, and p53 protein expression by Western blotting. Combination Index (CI) was calculated according to Additive model. Results: We observed strong synergistic effect (CI&lt;0.5) with APR-246 and cisplatin in lung cancer cell lines carrying homozygous p53 hotspot mutations; NCI-H1770 (R248W), NCI-H1975 (R273H), NCI-H596 (G245C), PC-14 (R248W) and PC-14/CDDP (R248W). All these cell lines expressed a high level of p53. Synergistic (CI&lt;0.8) or strong synergistic effect was found in lung cancer cell lines NCI-H378 (Y163C) and NCI-2087 (V157F) with homozygous mutations that occur frequently but are not hotspot mutations. NCI-2087 cells with the smoking-related V157F mutation express a high level of p53, while NCI-H378 cells express lower level. Mixed antagonist/additive/synergistic effects were observed in the p53 null cell line HOP-62, which does not express p53. Conclusions: Treatment with APR-246 in combination with cisplatin resulted in strong synergistic effect in both NSCL and SCLC cancer cells. Strongest synergies were observed in lung cancer cells with p53 hotspot mutations expressing a high level of p53. Studies to investigate the molecular mechanisms underlying the synergistic effects are ongoing. Our results suggest that combination treatment with APR-246 and platinum drugs may allow an improved therapy of p53-mutant lung cancer.
Citation Format: Nina Mohell, Åsa Fransson, Jessica Alfredsson, Mikael von Euler, Ulf Björklund, Lars Abrahmsen. Strong synergistic effects with APR-246 and cisplatin in p53-mutant lung cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2523. doi:10.1158/1538-7445.AM2015-2523