Molecular characterizations of Nop16 in murine mammary tumors with varying levels of c-Myc.

NOP16, also known as HSPC111, has been identified as a MYC and estrogen regulated gene in in vitro studies, hence coexpression levels were strongly correlated. Importantly, high expression of NOP16 was associated with poor clinical outcome in breast cancer patients. However, coexpression of NOP16, MYC and estrogen receptor (ESR1) varied widely in tumors and cell lines suggesting that transcriptional regulation differed according to pathological environments.

Short-term prophylactic tamoxifen reduces the incidence of antiestrogen-resistant/estrogen receptor-positive/progesterone receptor-negative mammary tumors.

Although many estrogen receptor-positive (ER+) breast cancers are effectively treated with selective estrogen receptor modulators and down-regulators (SERM/SERD), some are highly resistant. Resistance is more likely if primary cancers are devoid of progesterone receptors (PR-) or have high levels of growth factor activity. In this study, a transgenic mouse line that expresses transforming growth factor-alpha (NRL-TGFalpha mice) and that develops ER+/PR- mammary tumors was used to assess the possible effects of (a) therapeutic delivery of the SERM, tamoxifen, or SERD, ICI I82,780 (ICI), on the growth of established tumors and (b) short-term prophylactic tamoxifen administration on the initial development of new mammary tumors.