p53 Gene mutations, p53 protein accumulation and compartmentalization in colorectal adenocarcinoma

p53 accumulation may occur in the nucleus and/or cytoplasm of neoplastic cells. Cytoplasmic accumulation has been reported to be an unfavorable, but not established, prognostic indicator in colorectal cancer. Different types of p53 intracellular compartmentalization could depend either on p53 gene mutations or on the interaction with p53 protein ligands. The purposes of our study were (1) to assess whether the different patterns of p53 accumulation are selectively associated with p53 mutations and (2) to evaluate the clinical significance of p53 mutations in colorectal carcinomas. We evaluated p53 gene mutations in exons 5 through 8, by polymerase chain reaction and single-strand conformation polymorphism analysis; p53 accumulation and intracellular compartmentalization were detected immunocytochemically with the antibodies PAb1801 and CM1. p53 mutations were found in 74 of 126 carcinomas (59%). Nuclear p53(PAb1801) accumulation was associated with p53 gene mutations (P <0.001) whereas cytoplasmic p53(CM1) accumulation was more likely to occur with the wild-type p53 gene (P = 0.048). Overall, 112 carcinomas (89%) displayed p53 gene mutations and/or p53 accumulation of any type. p53 mutations were not correlated with important clinicopathological parameters and were not related to patient survival. Our data suggest that mechanisms other than mutations may also play a role in inhibiting p53 tumor- suppressing functions in colorectal carcinomas. Cytoplasmic p53(CM1) accumulation frequently does not depend on p53 mutations.