Small cell lung cancer (SCLC) is an aggressive neuroendocrine subtype of lung cancer with high mortality. We used a systematic drug-repositioning bioinformatics approach querying a large compendium of gene expression profiles to identify candidate FDA-approved drugs to treat SCLC. We found that tricyclic antidepressants and related molecules potently induce apoptosis in both chemonaïve and chemoresistant SCLC cells in culture, in mouse and human SCLC tumors transplanted into immunocompromised mice, and in endogenous tumors from a mouse model for human SCLC. The candidate drugs activate stress pathways and induce cell death in SCLC cells, at least in part by disrupting autocrine survival signals involving neurotransmitters and their G protein-coupled receptors. The candidate drugs inhibit the growth of other neuroendocrine tumors, including pancreatic neuroendocrine tumors and Merkel cell carcinoma. These experiments identify novel targeted strategies that can be rapidly evaluated in patients with neuroendocrine tumors through the repurposing of approved drugs.

Purpose: As chemotherapy and molecular therapy improve the systemic survival of breast cancer patients, the incidence of brain metastases increases. Few therapeutic strategies exist for the treatment of brain metastases because the blood-brain barrier severely limits drug access. We report the pharmacokinetic, efficacy, and mechanism of action studies for the histone deactylase inhibitor vorinostat (suberoylanilide hydroxamic acid) in a preclinical model of brain metastasis of triple-negative breast cancer. Experimental Design: The 231-BR brain trophic subline of the MDA-MB-231 human breast cancer cell line was injected into immunocompromised mice for pharmacokinetic and metastasis studies. Pharmacodynamic studies compared histone acetylation, apoptosis, proliferation, and DNA damage in vitro and in vivo. Results: Following systemic administration, uptake of [ 14 C]vorinostat was significant into normal rodent brain and accumulation was up to 3-fold higher in a proportion of metastases formed by 231-BR cells. Vorinostat prevented the development of 231-BR micrometastases by 28% (P = 0.017) and large metastases by 62% (P < 0.0001) compared with vehicle-treated mice when treatment was initiated on day 3 post-injection. The inhibitory activity of vorinostat as a single agent was linked to a novel function in vivo: induction of DNA double-strand breaks associated with the down-regulation of the DNA repair gene Rad52. Conclusions:We report the first preclinical data for the prevention of brain metastasis of triple-negative breast cancer. Vorinostat is brain permeable and can prevent the formation of brain metastases by 62%. Its mechanism of action involves the induction of DNA double-strand breaks, suggesting rational combinations with DNA active drugs or radiation. (Clin Cancer Res 2009;15(19):6148-57) Significant advances have been made in the treatment of primary breast cancer; one of the unfortunate complications of this progress is an increase in the incidence of brain metastases (reviewed in refs. 1, 2). Combinations of cytotoxic and targeted therapies have afforded metastatic breast cancer patients' clinical responses or stable disease, but the poor penetration of these drugs into the brain and leptomeninges creates a "sanctuary site" for recurrence. With an increased number of metastatic breast cancer patients having stable disease or responding to treatment systemically when they develop brain metastases,