Characterisation of gain of function activity of non-hotspot p53 mutations identified from Indian squamous cell carcinoma patients using the CRISPR/Cas9 system.
Mutant p53 is proposed to exhibit oncogenic gain of transcription function (GOTF) by positively regulating expression of several oncogenes. However, work in this area is limited to a few ‘hot spot’ mutations restricted to adenocarcinomas where p53 mutation appears to be a late event unlike squamous cell carcinomas where it may be an early event. We performed transcriptome profiling of tongue and oesophageal squamous carcinoma samples stratified by p53 status and identified several novel transcriptional targets of mutant p53. More importantly, the p53 mutations and their oncogenic targets were distinct from the canonical ones described in the literature. The novel targets were characterized using several approaches such as ChIP, promoter-luciferase assays, data mining of published NGS data sets, etc. We are currently generating squamous cell lines harboring India-specific non-canonical p53 mutations using CRISP/Cas9 based genome engineering to comprehensively characterize GOTF exhibited by mutant p53.