Sequence homology to deoxyribonucleic acid to mouse mammary tumor virus genome in human breast tumors

Fifty-two hum an breast tumors were screened for the presence of DNA homology to m ouse mammary tumor virus (MMTV) using molecularly cloned MMTV proviral genomic DNA probes and dot-blot hybridization. Seven patients were found to contain an entire provirus (gag, pol, env, and LTR positive at high stringency). Fifty percent (5/10) of patients having a first degree relative with breast carcinoma were found to have DNA homol ogy to the gag-pol portion of the MMTV genome w hen hybridization and w ashing was perform ed at moderate (56C) stringency. Thirty-nine percent (7/18) of patients w ith any positive family history and 23 percent (8/34) of patients with a negative family history dem onstrated homology under these param eters. O f the patients positive for gag-pol at moderate stringency, fewer had taken exogenous hormones than the sample group (20 percent vs 52 percent), more w ere parous (93 percent vs 68 percent), estrogen receptor positive (69 percent vs 48 percent), and male (13 percent vs 4 percent). At higher stringency (62C) no correlation to family history, hormone use or sex was detected, bu t positivity was noted among estrogen and progesterone receptor positive patients (67 percent vs 48 percent). U nder lower strin gency wash conditions, m ismatched MMTV-related sequences are identi fied suggesting the existence of an endogenous gene with partial homology to MMTV. High stringency hybridization may identify a related retrovirus w ith significant homology to MMTV