Mutation and expression analysis of human BUB1 and BUB1B in aneuploid breast cancer cell lines

Genetic instability is a hallmark feature of breast, colorectal and other t ypes of cancers. One type characterized by chromosomal instability is thoug ht to be important in the pathogenesis of many solid tumors displaying aneu ploidy. Two related protein kinases and homologues of the yeast checkpoint genes, hBUB1 and hBUB1B, have been implicated in the pathogenesis of colore ctal cancers. Mutations in hBUB1 have demonstrated a dominant negative effe ct by disrupting the mitotic checkpoint when transfected into euploid colon cancer cell lines. In Brca2 deficient murine cells, Bub1 mutants potentiat e growth and cellular transformation. This would suggest that aneuploidy in solid tumors including breast, could be the result of defects in mitotic c heckpoint genes and may be responsible for a chromosomal instability phenot ype contributing to tumor progression. We conducted mutational analysis of 19 aneuploid breast cancer cell lines. No mutations were found but we ident ified nine sequence variations including five previously unreported sequenc e variants in hBUB1B, two of which affect restrictions sites. None of these nucleotide changes predict significant changes in the predicted protein st ructure. Expression analysis by Northern blot of boast cell lines showed va riable expression of hBUB1 and hBUB1B genes. This suggest that while regula tion of expression of these genes may be important in cancer, the lack of p utative deleterious mutations in the coding sequence does not support a fre quent role for mutant hBUB1 and hBUB1B alleles in the pathogenesis of breas t cancer. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.