Large oncosomes (LO) are atypically large (1-10μm diameter) cancer-derived extracellular vesicles (EVs), originating from the shedding of membrane blebs and associated with advanced disease. We report that 25% of the proteins, identified by a quantitative proteomics analysis, are differentially represented in large and nano-sized EVs from prostate cancer cells. Proteins enriched in large EVs included enzymes involved in glucose, glutamine and amino acid metabolism, all metabolic processes relevant to cancer. Glutamine metabolism was altered in cancer cells exposed to large EVs, an effect that was not observed upon treatment with exosomes. Large EVs exhibited discrete buoyant densities in iodixanol (OptiPrepTM) gradients. Fluorescent microscopy of large EVs revealed an appearance consistent with LO morphology, indicating that these structures can be categorized as LO. Among the proteins enriched in LO, cytokeratin 18 (CK18) was one of the most abundant (within the top 5th percentile) and was used to develop an assay to detect LO in the circulation and tissues of mice and patients with prostate cancer. These observations indicate that LO represent a discrete EV type that may play a distinct role in tumor progression and that may be a source of cancer-specific markers.

The androgen receptor (AR) is the best studied drug target for the treatment of prostate cancer. While there are a number of drugs that target the AR, they all work through the same mechanism of action and are prone to the development of drug resistance. There is a large unmet need for novel AR inhibitors which work through alternative mechanism(s). Recent studies have identified a novel site on the AR called Binding Function 3 (BF3) that is involved into AR transcriptional activity. In order to identify inhibitors that target the BF3 site, we have conducted a large-scale in-silico screen followed by experimental evaluation. A number of compounds were identified that effectively inhibited the AR transcriptional activity with no obvious cytotoxicity. The mechanism of action of these compounds was validated by biochemical assays and x-ray crystallography. These findings lay a foundation for the development of alternative or supplementary therapies capable of combating prostate cancer even in its anti-androgen resistant forms.

The human androgen receptor (AR) is a proven therapeutic target in prostate cancer. All current antiandrogens, such as Bicalutamide, Flutamide, Nilutamide, and Enzalutamide, target the buried hydrophobic androgen binding pocket of this protein. However, effective resistance mechanisms against these therapeutics exist such as mutations occurring at the target site. To overcome these limitations, the surface pocket of the AR called binding function 3 (BF3) was characterized as an alternative target for small molecule therapeutics. A number of AR inhibitors directly targeting the BF3 were previously identified by us ( J. Med. Chem. 2011 . 54 , 8563 ). In the current study, based on the prior results, we have developed structure-activity relationships that allowed designing a series of 2-((2-phenoxyethyl)thio)-1H-benzimidazole and 2-((2-phenoxyethyl)thio)-1H-indole as lead BF3 inhibitors. Some of the developed BF3 ligands demonstrated significant antiandrogen potency against LNCaP and Enzalutamide-resistant prostate cancer cell lines.

More than one third of recently diagnosed prostate cancer patients utilize some form of CAM therapy, and the majority disclose their use to their physician(s). However, they tend to rely on anecdotal information for their CAM decision making. Dissemination of reliable CAM information is one key to helping men navigate this difficult arena.

There has been a resurgence of interest in the development of androgen receptor (AR) inhibitors with alternative modes of action to overcome the development of resistance to current therapies. We demonstrated previously that one promising strategy for combatting mutation-driven drug resistance is to target the Binding Function 3 (BF3) pocket of the receptor. Here we report the development of a potent BF3 inhibitor, 3-(2,3-dihydro-1H-indol-2-yl)-1H-indole, which demonstrates excellent antiandrogen potency and anti-PSA activity and abrogates the androgen-induced proliferation of androgen-sensitive (LNCaP) and enzalutamide-resistant (MR49F) PCa cell lines. Moreover, this compound effectively reduces the expression of AR-dependent genes in PCa cells and effectively inhibits tumor growth in vivo in both LNCaP and MR49F xenograft models. These findings provide evidence that targeting the AR BF3 pocket represents a viable therapeutic approach to treat patients with advanced and/or resistant prostate cancer.