The molecular regulation of growth and progression of hormone refractory breast and prostate cancers remains challenging. The Division of Cancer Biology, NCI organized a small "think tank" style workshop and invited scientists in relevant areas to assess the state of science on the biology of hormone refractory tumors and to identify potential research opportunities to enhance a better understanding of the molecular regulation of these tumors. The meeting, held on May 27-29, 2008 in Bethesda, MD, was co-chaired by Drs. Michael Geoffrey Rosenfeld and Michael Press. While expression of estrogen or progesterone receptors (ER/PR) is required for benefit from endocrine manipulations, many women with breast cancer will not respond to primary endocrine manipulations despite ER/PR expression, and others acquire resistance while on treatment. Understanding the mechanisms that lead to Hormone Refractory Breast Cancer (HRBC) and defining interventions that may modulate the resistance to endocrine therapy are currently lacking. In contrast to breast cancers, the vast majority of both early and advanced prostate carcinomas exhibit androgen-pathway activity at diagnosis and the vast majority respond to treatments designed to inhibit AR-signaling. However, after initial benefit, advanced prostate cancers regularly progress to a clinical state termed Castration Resistant Prostate Cancer (CRPC) that reflects a diverse array of molecular events maintaining AR signaling. The workshop focused on both common and unique features of hormone refractory breast and prostate cancer with an orientation toward defining major research questions, delineating opportunities and recommending strategies for overcoming barriers to progress in understanding these important clinical disease states.

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Although 5HT2A receptors mediate contractions of normal arteries to serotonin (5HT), in some cardiovascular diseases, other receptor subtypes contribute to the marked increase in serotonin contractions. We hypothesized that enhanced contractions of arteries from diabetics to 5HT are mediated by an increased contribution from multiple 5HT receptor subtypes. We compared responses to selective 5HT receptor agonists and expression of 5HT receptor isoforms (5HT1B, 5HT2A, and 5HT2B) in aorta from nondiabetic (ND) compared to type 2 diabetic mice (DB, BKS.Cg-Dock7 m+/+Leprdb/J). 5HT, 5HT2A (TCB2 and BRL54443), and 5HT2B (norfenfluramine and BW723C86) receptor agonists produced concentration-dependent contractions of ND arteries that were markedly increased in DB arteries. Neither ND nor DB arteries contracted to a 5HT1B receptor agonist. MDL11939, a 5HT2A receptor antagonist, and LY272015, a 5HT2B receptor antagonist, reduced contractions of arteries from DB to 5HT more than ND. Expression of 5HT1B, 5HT2A, and 5HT2B receptor subtypes was similar in ND and DB. Inhibition of rho kinase decreased contractions to 5HT and 5HT2A and 5HT2B receptor agonists in ND and DB. We conclude that in contrast to other cardiovascular diseases, enhanced contraction of arteries from diabetics to 5HT is not due to a change in expression of multiple 5HT receptor subtypes.

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