Abstract 556: Oncogenic properties and response to HDAC inhibitor treatment of H1299 cells expressing GOF p53 mutants

Abstract

Abstract The tumor suppressor p53 protein is mutated in over 50% of cancers. The most frequent mutations in p53, termed “hotspot” mutations, occur in the DNA binding domain of the p53 protein. These mutations not only remove normal p53 function but also convey additional oncogenic properties greater than loss of tumor suppressor activities associated with loss of wild-type (WT) p53 activities. With newly acquired oncogenic properties, mutations in the DNA binding domain of p53 are classified as gain of function (GOF) mutations. GOF p53 mutants can be subdivided into conformational mutations (e.g. R175H, H193Y) involving residues necessary for maintenance of structure and contact mutations (e.g. R248Q, R273H) involving resides necessary for DNA interaction. Cancer cells bearing a GOF p53 mutation increase metastasis with application of histone deacetylase inhibitors (HDACi). This uncharacterized pro-oncogenic GOF p53 property is of clinical relevance as HDACi are FDA approved for hematological cancers but have failed in clinical trials for solid tumors. To explore this hypothesis, metastatic capacity and proliferation rates of common GOF p53 mutations were assessed with and without HDACi treatment and in the presence or absence of specific inhibitors of target GOF p53. The p53-null, H1299 non-small cell lung carcinoma line was transfected with GOF p53 mutants and WT p53 using a tetracycline inducible expression system. Inducible expression of stable subclones was varified by immunofluorescence and western blot. Proliferation rate was measured by incorporation of EdU and metastatic capacity was assessed by measuring MMP activity and migration assays with and without HDACi treatment. Specific GOF p53 mutations possess a subset of the oncogenic properties of the entire GOF p53 class. Data suggest that the GOF p53 mutants display differing rates of proliferation with the R175H mutation exhibiting the highest rate. Application of NSC319726 significantly decreases the proliferation rate and appears to successfully refold the R175H mutant to a WT conformation. The R248Q mutation exhibited morphological change suggestive of the epithelial to mesenchymal transition associated with increased metastatic capacity. Preliminary data suggest that HDACi affect among these cell lines in conjunction with NSC 319726 and SCH 529074 treatment. In conclusion, HDACi treatment may be contraindicated while treatment with HDACi may have great benefit in tumors which are WT or null for p53 protein expression. Citation Format: Brianna Flores, Elizabeth E. Hull. Oncogenic properties and response to HDAC inhibitor treatment of H1299 cells expressing GOF p53 mutants [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 556.