Resistance to androgen receptor (AR) blockade in castration-resistant prostate cancer (CRPC) is associated with sustained AR signaling, including through alternative splicing of AR (AR-SV). Inhibitors of transcriptional coactivators that regulate AR activity, including the paralog histone acetyltransferase proteins p300 and CBP, are attractive therapeutic targets for lethal prostate cancer. Herein, we validate targeting p300/CBP as a therapeutic strategy for lethal prostate cancer and describe CCS1477, a novel small-molecule inhibitor of the p300/CBP conserved bromodomain. We show that CCS1477 inhibits cell proliferation in prostate cancer cell lines and decreases AR- and C-MYC–regulated gene expression. In AR-SV–driven models, CCS1477 has antitumor activity, regulating AR and C-MYC signaling. Early clinical studies suggest that CCS1477 modulates KLK3 blood levels and regulates CRPC biopsy biomarker expression. Overall, CCS1477 shows promise for the treatment of patients with advanced prostate cancer. Significance: Treating CRPC remains challenging due to persistent AR signaling. Inhibiting transcriptional AR coactivators is an attractive therapeutic strategy. CCS1477, an inhibitor of p300/CBP, inhibits growth and AR activity in CRPC models, and can affect metastatic CRPC target expression in serial clinical biopsies. See related commentary by Rasool et al., p. 1011. This article is highlighted in the In This Issue feature, p. 995

Purpose: The clinical success of arsenic trioxide (As 2 O 3 ) in hematologic malignancies has not been replicated in solid tumors due to poor pharmacokinetics and dose-limiting toxicity. We have developed a novel nanoparticulate formulation of As 2 O 3 encapsulated in liposomal vesicles or "nanobins" [(NB(Ni, As)] to overcome these hurdles. We postulated that nanobin encapsulation of As 2 O 3 would improve its therapeutic index against clinically aggressive solid tumors, such as triple-negative breast carcinomas.Experimental Design: The cytotoxicity of NB(Ni,As), the empty nanobin, and free As 2 O 3 was evaluated against a panel of human breast cancer cell lines. The plasma pharmacokinetics of NB(Ni,As) and free As 2 O 3 were compared in rats to measure drug exposure. In addition, the antitumor activity of these agents was evaluated in an orthotopic model of human triple-negative breast cancer.Results: The NB(Ni,As) agent was much less cytotoxic in vitro than free As 2 O 3 against a panel of human breast cancer cell lines. In contrast, NB(Ni,As) dramatically potentiated the therapeutic efficacy of As 2 O 3 in vivo in an orthotopic model of triple-negative breast cancer. Reduced plasma clearance, enhanced tumor uptake, and induction of tumor cell apoptosis were observed for NB(Ni,As).Conclusions: Nanobin encapsulation of As 2 O 3 improves the pharmacokinetics and antitumor efficacy of this cytotoxic agent in vivo. Our findings demonstrate the therapeutic potential of this nanoscale agent and provide a foundation for future clinical studies in breast cancer and other solid tumors. Clin Cancer Res; 16(14); 3607-17. ©2010 AACR.Breast cancer is the second leading cause of cancer mortality for women in the United States (1). Although preventive agents and targeted therapies directed at the estrogen receptor, progesterone receptor, and human epidermal growth factor 2 receptor (HER2/neu) have resulted in improved clinical outcomes for many women with breast cancer, formidable challenges remain in treating tumors that do not express these molecular targets. These "triple-negative" breast carcinomas represent 15% of newly diagnosed breast cancer cases and often exhibit a basal epithelial or basal-like gene expression profile that is associated with poor survival (2-4). Consistent with its aggressive nature, triple-negative breast cancer is characterized by high rates of distant recurrence, particularly in the lung and brain, within the first five years after diagnosis despite adjuvant chemotherapy (5, 6). Hence, development of new therapeutic agents for these clinically intractable tumors is highly desirable.Arsenic trioxide (As 2 O 3 ) is a Food and Drug Administration-approved treatment for refractory acute promyelocytic leukemia (APL) and has shown preliminary activity in patients with relapsed/refractory multiple myeloma (7-10). Several mechanisms of action have been proposed for As 2 O 3 activity, including induction of apoptosis mediated by reactive oxygen species, promotion of cellular differentiation, and ...

While research has identified an important contribution for metals, such as iron, in microbial pathogenesis, the roles of other transition metals, such as copper, remain mostly unknown. Recent evidence points to a requirement for copper homeostasis in the virulence of Cryptococcus neoformans based on a role for a CUF1 copper regulatory factor in mouse models and in a human patient cohort. C. neoformans is an important fungal pathogen that results in an estimated 600,000 AIDS-related deaths yearly. In the present studies, we found that a C. neoformans mutant lacking the CUF1-dependent copper transporter, CTR4, grows normally in rich medium at 37°C but has reduced survival in macrophages and attenuated virulence in a mouse model. This reduced survival and virulence were traced to a growth defect under nutrient-restricted conditions. Expression studies using a full-length CTR4-fluorescent fusion reporter construct demonstrated robust expression in macrophages, brain, and lung, the latter shown by ex vivo fluorescent imaging. Inductively coupled mass spectroscopy (ICP-MS) was used to probe the copper quota of fungal cells grown in defined medium and recovered from brain, which suggested a role for a copper-protective function of CTR4 in combination with cell metallothioneins under copper-replete conditions. In summary, these data suggest a role for CTR4 in copper-related homeostasis and subsequently in fungal virulence.

Exploiting oxidative stress has recently emerged as a plausible strategy for treatment of human cancer, and antioxidant defenses are implicated in resistance to chemotherapy and radiotherapy. Targeted suppression of antioxidant defenses could thus broadly improve therapeutic outcomes. Here, we identify the AMPK-related kinase NUAK1 as a key component of the antioxidant stress response pathway and reveal a specific requirement for this role of NUAK1 in colorectal cancer. We show that NUAK1 is activated by oxidative stress and that this activation is required to facilitate nuclear import of the antioxidant master regulator NRF2: Activation of NUAK1 coordinates PP1β inhibition with AKT activation in order to suppress GSK3β-dependent inhibition of NRF2 nuclear import. Deletion of NUAK1 suppresses formation of colorectal tumors, whereas acute depletion of NUAK1 induces regression of preexisting autochthonous tumors. Importantly, elevated expression of NUAK1 in human colorectal cancer is associated with more aggressive disease and reduced overall survival. This work identifies NUAK1 as a key facilitator of the adaptive antioxidant response that is associated with aggressive disease and worse outcome in human colorectal cancer. Our data suggest that transient NUAK1 inhibition may provide a safe and effective means for treatment of human colorectal cancer via disruption of intrinsic antioxidant defenses. .

Evidence suggests that chronic low level cadmium exposure impairs the function of insulin-producing β cells and may be associated with type-2 diabetes mellitus. Herein, we describe the cadmium content in primary human islets and define the uptake kinetics and effects of environmentally relevant cadmium concentrations in cultured β cells. The average cadmium content in islets from 10 non-diabetic human subjects was 29 ± 7 nmol/g protein (range 7 to 72 nmol/g protein). Exposure of the β-cell line MIN6 to CdCl2 concentrations between 0.1 and 1.0 µmol/L resulted in a dose- and time-dependent uptake of cadmium over 72 h. This uptake resulted in an induction of metallthionein expression, likely enhancing cellular cadmium accumulation. Furthermore, cadmium accumulation resulted in an inhibition of glucose stimulated insulin secretion in MIN6 cells and primary mouse islets. Our results indicate that this impairment in β-cell function is not due to an increase in cell death or due to an increase in oxidative stress. We conclude that mouse β cells accumulate cadmium in a dose- and time-dependent manner over a prolonged time course at environmentally relevant concentrations. This uptake leads to a functional impairment of β-cell function without significant alterations in cell viability, expression of genes important for β-cell function or increase in oxidative stress.