Molecular characterization of TP53 mutations and copy number change in colorectal cancers.

Abstract

e15143 Background: TP53 mutations (mut) are prevalent in colorectal cancer (CRC) patients (pts) and can result in oncogenic gain of function effect as well as loss of tumor suppressor function depending on the mut. Methods: The Cancer Genome Atlas (TCGA) data of 220 CRC pts with tumors sequenced and gene copy numbers (CN) annotated was obtained. Pts with CMS subtype data also available were included (n = 167). Chi square test was used to compare frequency of TP53 mut and CN change among CMS subtypes. TP53 mRNA and protein levels were compared by TP53 mut and CN change using independent sample t test. Results: 86 (51.5%) pts were TP53 mutant, with 35.3% missense and 16.2% loss of function (LOF) mut. LOF mut included 14 non-sense and 13 frameshift mut, and occurred mostly in codons 213 and 306. Missense mut mostly affected codons 175, 248 and 273 in 10, 9 and 8 pts respectively. TP53 mut were most frequent in CMS2 and CMS4 subtypes (62.7 and 62.5% respectively). TP53 mut in CMS2 were mostly missense and CMS 4 pts mostly had LOF mut. TP53 CN loss was seen in 74.7% CMS 2, 68.8% CMS 4, 43.5% CMS 3 and 6.9% CMS1 pts. 84.9% pts with TP53 mut had CN loss vs 28.4% of wild type pts (p < 0.001). Frequency of TP53 CN loss did not vary significantly by type of TP53 mut. Pts with TP53 missense mut had higher p53 mRNA and protein levels than those with LOF mut. Pts with TP53 CN loss had lower mRNA levels but no change in protein levels than those with normal CN. Conclusions: The higher TP53 mRNA and protein levels with missense mut suggest possible gain of function. Research on interactions of TP53 change with wnt, myc, and TGF beta pathway genes may reveal synthetic lethal treatment combinations. [Table: see text]