HSD17B1 and breast carcinoma: More recently, studies using breast cancer cells where HSD17B1 was downregulated also show a significant reduction in proliferation and lowered E2 concentrations, and accompanied by increased DHT levels, likely as a result of the loss of E1 to E2 and DHT to 3α/3β-diol conversion by HSD17B1 [39, 46, 60].