Abstract C36: Hypoxia or glutathione depletion increase apoptotic response to PRIMA-1 in p53-mutated and nonmutated human breast cancer cells.

Abstract

Abstract Background: Hypoxia, dysfunction of the p53 tumor suppressor gene product, and intracellular glutathione levels are important in modulating resistance of solid tumors to chemotherapy. PRIMA-1 (bis(hydroxymethyl-3-quinuclidinone) and its structural analog PRIMA-1met are used to reactivate mutant p53 and induce tumor cell apoptosis. However, PRIMA-1met as a single agent was reportedly ineffective in lowering clonogenic survival of (mut p53) DU145 prostate cancer cells, under hypoxia. Purpose: Here, we investigated whether the toxicity of PRIMA-1 (p53 reactivation and induction of massive apoptosis) is influenced by hypoxia in matched human breast cancer cells with unequal p53 genotype, and by agents that decrease glutathione levels in matched wt p53 human breast cancer cells with different Mn-SOD expression. Methodology: Cell survival was assessed by cytofluorometric and clonogenic analysis, estimating apoptosis-associated PARP cleavage by Western blot. Results: Mutant p53 breast cancer cells were susceptible to PRIMA-1 under normoxia and this response increased under hypoxia. Matched wt p53 breast carcinoma cells were resistant to comparable PRIMA-1 concentrations in normoxia but became sensitive to it under hypoxia. In contrast, hypoxia did not enhance cytotoxicity of nutlin-3a, known to increase wt p53 signaling by inhibit MDM2 binding to p53. Normoxic resistance to PRIMA-1 in wt p53 breast cancer cells was also antagonized by glutathione depletion or Mn-SOD over-expression. Conclusions: Hypoxia, a common feature of the microenvironment of solid tumors is believed to promote cancer progression and poor clinical outcome. This report is the first to show that hypoxia enhances PRIMA-1 toxicity against human breast cancer cells with mutated or non-mutated TP53 status. We propose that PRIMA-1 may help to counteract hypoxia-acquired resistance to cancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C36.