Somatic mutations of BECN1, an autophagy-related gene, in human cancers

Evasion of programmed cell death (PCD) is one of the hallmarks of human cancers. It is well known that not only apoptosis, but also autophagy, acts as an action mechanism of PCD. BECN1 protein is a key regulator of autophagic PCD. The BECN1 gene that encodes BECN1 protein acts as a haploinsufficient tumor-suppressor gene. However, to date, data on BECN1 mutation in human cancer tissues are lacking. To explore the possibility that somatic mutation of the BECN1 gene might contribute to the development of human cancers, we analyzed the entire coding region and all splice sites of the human BECN1 gene for detection of somatic mutations in 180 gastric carcinomas, 94 breast carcinomas, 50 acute leukemias, 50 colorectal carcinomas, 50 hepatocellular carcinomas, and 124 non-small cell lung cancers by single-strand conformation polymorphism (SSCP) and DNA sequencing. Overall, we detected 11 somatic mutations of the BECN1 gene, including 3 missense mutations (N8K, P350R and R389C) in coding sequences and 8 mutations in introns. The mutations were observed in five gastric, three colorectal, one lung and one breast carcinoma (s). We expressed the three mutations (N8K, P350R and R389C) in HT1080 cells, and found that two (P350R and R389C) of them showed only slightly decreased cell death activities compared to the wild-type BECN1. This is the first report on BECN1 gene mutations in human cancer tissues, and the data suggest that point mutations are a rare event in common human cancers and probably do not play a major role in cancer pathogenesis.