Characterisation of P53 isoforms and expression in colorectal cancer cell lines

Abstract

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality and the third most prevalent cancer type world-wide. CRC can be classified into four consensus molecular subgroups (CMS), CMS1-CMS4, based on differing characteristics. In CRC, as well as other cancers, disruption of tumour suppressor genes and proteins is crucial to tumour progression and cancer formation. The tumour suppressor TP53 has been noted to play a principal role in CRC since it encodes for the regulatory protein p53 whose pathway is dysregulated preventing activation of numerous cellular responses and DNA repair mechanisms in response to DNA-damaging and oncogenic stress signals. Recent literature reported an abundance of alternative splicing or promoter-governed expression of p53 isoforms detected in several cancer tissues, including that of CRC, suggesting their implication in carcinogenesis. Despite this, an understanding of the expression of p53 isoforms in the distinct CRC CMS-classifications and the complete characterisation of the expression isoforms still remains incomplete, making them a considerable challenge facing precision oncology. The study aims to characterise p53 isoforms and determine whether the pattern of expressed p53 isoforms differs among CRC cell lines and between different CRC-CMS subtypes. LoVo and DLD-1 CMS1 CRC cell lines together with HCT116 and SW480 as CMS4 CRC cell lines were cultured invitro. Western blotting was conducted on CMS1 and CMS4 cell lysates probed with p53- specific N-terminal binding (PAb1801 and DO-7), C-terminal binding (PAb421) and DBD-binding (PAb240) antibodies. Several bands potentially corresponding to p53 isoforms were identified in all cell lines, most notable in the HCT116. A greater number of bands were detected in CMS4 than CMS1 and a potential relationship between Δ133p53, Δ40p53, p53β and CMS4 was observed.