The drug commonly used for Her2-positive breast cancers may actually turn ER-negative status into positive. It’s a two-step process, though, and the research was done on ER-negative, Her2-positive laboratory cells, not on human subjects. Still, it offers amazing potential and could ultimately provide much-needed therapy for hormone-negative breast cancer, including triple negative.
After being treated with trastuzumab (Herceptin), ER-negative cells actually turned into ER-positive cells, making them then react to anti-estrogen drugs like tamoxifen and aromatase inhibitors, according to research presented at the Endocrine Society meeting this month.
The research was done in vitro—in a lab, on existing cells, rather than in human subjects. Cells were ER-negative, Her2-postive and were treated with trastuzumab; after 72 hours they were treated with the hormones estradiol and androstenedione. After that they were given aromatase inhibitors and antiestrogens.
The tumors then reacted in much the way ER-positive tumors do to aromatase inhibitors and antiestrogens.
Read more about the study here.
SOURCE: Sabnis G, Brodie A “Trastuzumab sensitizes ER negative, HER-2 positive breast cancer cells (SKBr-3) to endocrine therapy” ENDO 2009; Abstract OR38-02.