Thyroid hormone enhances estrogen-mediated proliferation and cell cycle regulatory pathways in steroid receptor-positive breast Cancer

Here, we treated a nove ER-positive PDX (UCD12) supplemented with estrogen (E2) with or without thyroid hormone (TH) and/or tamoxifen (Tam). Each treatment cohort (E2 alone, E2 + TH, E2 + Tam, E2+ TH+Tam) tumor growth over time was monitored. Tumors treated with TH continued to grow more that E2 alone. Tamoxifen blocked E2-mediated tumor growth, however in the presence of TH this was not seen. This analysis identified thyroid hormone as a potential driver of tumor progression in the context of estrogen receptor positive PDX tumor model. E2 n= 6, E2+TH n= 6, E2+Tam n=6, E2+TH+Tam n=6