Data from Mouse Mammary Tumor Virus–like Sequences in Human Breast Cancer

<div>Abstract<p>Mouse mammary tumor virus (MMTV) sequences have been reported to be present in some human breast cancers, but it is unclear whether they have any causal role. In mice, MMTV promotes tumor formation indirectly by insertional mutagenesis of Wnt oncogenes that lead to their activation. In this study, we investigated the status of Wnt-1 in human breast cancers harboring MMTV-like sequences encoding viral envelope (<i>env</i>) genes. We confirmed the detection of <i>env</i> sequences in the nucleus of human breast cancer specimens that are similar in appearance to mouse mammary tumors expressing MMTV <i>env</i> sequences. MMTV <i>env</i> sequences in human breast cancers were also nearly indistinguishable from <i>env</i> sequences in mouse MMTV isolates. Further, Wnt-1 expression was higher in specimens of <i>env</i>-positive ductal carcinoma <i>in situ</i> and invasive ductal carcinoma, relative to <i>env</i>-negative specimens. Our findings extend the evidence that MMTV sequences found in naturally occurring mouse mammary tumors can be found in some human breast cancers, prompting further evaluation of causal roles in these settings. Cancer Res; 70(9); 3576–85. ©2010 AACR.</p></div>