Studying the Impact of Tp53 Mutations on Colorectal Cancer Pathogenesis and Therapeutic Response in a Tunisian Population

Introduction: Colorectal cancer has been ranked as the second most deadly cancer and the third most diagnosed cancer for the year 2020.TP53 a pivotal tumor suppressor gene, is frequently mutated in colorectal cancer (CRC), influencing tumorigenesis and therapy response. This study investigates the mutational spectrum of TP53 in CRC, elucidates its effects on tumor progression, and examines its correlation with clinical outcomes and chemotherapy efficacy. The primary objective was to study the correlation between p53 expression by immunohistochemistry and TP53 mutational status in Tunisian colorectal cancer patients. The secondary objective was to characterize TP53 mutations in CRC and assess their impact on tumor development, clinical parameters, and response to 5- fluorouracil (5-FU)-based chemotherapy. Methods: A cohort of 59 CRC samples obtained from formalin-fixed paraffin-embedded (FFPE) tissue blocks were analyzed. DNA was extracted and polymerase chain reaction (PCR) targeting TP53 exons 5-8 followed by Sanger sequencing was performed to identify mutations. Immunohistochemistry was used to assess p53 protein expression and its association with mutation status. In silico tools, including SIFT, PolyPhen-2, Mutation Taster, PROVEAN, FATHMM, RNAfold, and Project Hope, were used to predict the functional consequences of identified mutations. The association between TP53 mutations and clinicopathological features such as tumor stage, grade, lymphovascular and perineural invasion, RAS mutation status, overall survival (OS), and progression-free survival (PFS) were analyzed. Results: TP53 mutations were identified in 42.37% of the analyzed CRC samples, encompassing 14 different mutation types. The mutations consisted of 10 missense mutations (71.4%) and 4 synonymous mutations (28.5%). A novel pathogenic variant (L252R, c.755T>G) was also discovered. Initially, a general analysis of TP53 mutations revealed a significant association with increased p53 protein expression (P=0.04); however, no direct correlation was found with clinicopathological parameters such as tumor stage or metastasis at this stage of analysis. In a more focused investigation, pathogenic TP53 mutations were specifically analyzed. This analysis demonstrated that pathogenic mutations were strongly associated with more aggressive clinical features, including advanced tumor stage (P=0.008), lymph node metastasis (P=0.015), poorer overall survival (OS) (P=0.047) and progression-free survival (PFS) (p=0.04) in patients treated with 5-FU-based chemotherapy. In silico predictions further confirmed that these pathogenic mutations significantly disrupted the stability and function of the p53 protein, highlighting their potential role in driving tumor aggressiveness and resistance to standard therapies. Conclusions: TP53 mutations, especially pathogenic variants, play a crucial role in the pathogenesis of colon cancer as they influence tumor aggressiveness and resistance to therapy. The identification of specific mutations and their functional consequences has improved our understanding of CRC biology and highlighted the potential of TP53 as a biomarker for personalized treatment strategies. Incorporating TP53 mutation analysis into clinical practice could significantly improve patient stratification and treatment outcomes.