HUMAN BREAST-CARCINOMA CELLS TRANSFECTED WITH THE GENE ENCODING A C-MYC PROMOTER-BINDING PROTEIN (MBP-1) INHIBITS TUMORS IN NUDE-MICE

We have identified previously a gene from a human cervical carcinoma c ell (HeLa) cDNA expression library that encodes a M(r) similar to 37,0 00 c-myc promoter-binding protein (MBP-1), which binds to the TATA box sequences of c-myc P2 promoter and exerts a negative regulatory funct ion by down-regulating c-myc expression. In normal human tissues, this cloned gene showed variable expression, In this study, we have demons trated that introduction of the MBP-1 gene into human breast carcinoma cells reduced their ability to invade through a basement membrane mat rix in vitro but did not alter their growth rate, Human breast carcino ma transfected with MBP-1 cells showed a loss of anchorage-independent growth and also suppressed tumor formation in athymic nude mice. Thes e results suggest the possible involvement of MBP-1 as a tumor suppres sor gene in human breast carcinoma cells.