Secretory Type II Phospholipase A₂ (PLA2G2A) expression status in colorectal carcinoma derived cell lines and in normal colonic mucosa

Abstract

There is good evidence now that the secretory type II phospholipase A₂ (Pla2g2a) gene represents the Mom1 locus, a genetic modifier of tumor resistance in the multiple intestinal neoplasia (Min) mouse. Previously we have mapped the human homolog PLA2G2A to 1p35-36.1 within a region that is the target of frequent deletions in sporadic colorectal tumors. Here we show 64% loss of heterozygosity (LOH) at the PLA2G2A locus in primary tumors. We studied PLA2G2A expression in both colorectal tumor cell lines and normal mucosa. Most of the lines lacked detectable PLA2G2A transcripts by Northern analysis. Large differences in expression were seen among normal mucosa of different patients with sporadic tumors. We analysed the coding region of PLA2G2A in eight colorectal cancer cell lines with hemizygous deletion at 1p35-36/PLA2G2A, in none we did detect a mutation. Biallelic expression of PLA2G2A was observed in a cell line heterozygous for an exon 3 polymorphism, rendering unlikely that imprinting is a pathway participating in the loss of PLA2G2A function. It remains uncertain if PLA2G2A, in particular its apparent lack of expression in tumor cells, might be a factor in human colorectal tumorigenesis.