Clinical and biological relevance of single-nucleotide polymorphisms and acquired somatic mutations of the BCL6 first intron in follicular lymphoma.

Genetic modifications of the BCL6 gene in lymphoma include translocations, deletions, and somatic mutations (SM) of the 5' noncoding region. Three single-nucleotide polymorphisms (SNPs) of the major mutation cluster region (MMC) have been reported, including two substitutions (397G/C, 502G/A) and one deletion (520DeltaT). Clinical and biological relevance of these SNPs are unknown. Based on a case-control study, BCL6 SNPs frequencies were assessed in 97 t(14;18) follicular lymphomas (FL) and in 54 lymphomas with 3q27 rearrangement. Allele frequencies were similar in the FL and controls groups. The 397 G/C genotype was correlated to a higher-grade transformation risk (P=0.02). SM were observed in 39.1% of FL and were characterized by a clustering distribution (hot spots spanning position 420-435, 106-127, and 590-600). No correlation between genotypes or acquired mutational status and BCL6 expression was demonstrated. However, gel mobility-shift assays, using SNPs containing probes show results representative for protein/DNA complexes. This study demonstrates that the first BCL6 intron is a highly variable region as a consequence of both SNP and SM, which may contribute to biology and outcome of FL.