Castration-resistant prostate cancer (CRPC) is a lethal stage of disease in which androgen receptor (AR) signaling is persistent despite androgen deprivation therapy (ADT). Most studies have focused on investigating cell-autonomous alterations in CRPC, while the contributions of the tumor microenvironment are less well understood. Here we sought to determine the role of tumor-associated macrophages in CRPC, based upon their role in cancer progression and therapeutic resistance. In a syngeneic model that reflected the mutational landscape of CRPC, macrophage depletion resulted in a reduced transcriptional signature for steroid and bile acid synthesis, indicating potential perturbation of cholesterol metabolism. As cholesterol is the precursor of the five major types of steroid hormones, we hypothesized that macrophages were regulating androgen biosynthesis within the prostate tumor microenvironment. Macrophage depletion reduced androgen levels within prostate tumors and restricted AR nuclear localization in vitro and in vivo. Macrophages were also cholesterol-rich and were able to transfer cholesterol to tumor cells in vitro. AR nuclear translocation was inhibited by activation of liver X receptor (LXR)-β, the master regulator of cholesterol homeostasis. Consistent with these data, macrophage depletion extended survival during ADT and the presence of macrophages correlated with therapeutic resistance in patient-derived explants. Taken together, these findings support the therapeutic targeting of macrophages in CRPC. Significance: These results suggest that macrophage-targeted therapies can be combined with androgen deprivation therapy to treat patients with prostate cancer by limiting cholesterol bioavailability and the production of intratumoral androgens. See related commentary by Al-Janabi and Lewis, p. 5399

Objective There is an urgent need for the discovery and/or development of novel antibiotics. We report an exploration of “slow”-growing bacteria, which can be difficult to isolate using rich media as they are usually outcompeted by “fast”-growing bacteria, as potential sources of novel antimicrobials. Results Pseudomonas sp. RIT 623 was isolated using pond water agar from a pond located on the campus of the Rochester Institute of Technology (RIT). The genome was sequenced and analyzed for potential secondary metabolite gene clusters. Bioinformatics analysis revealed 14 putative gene clusters predicted to encode pathways for the anabolism of secondary metabolites. Ethyl acetate extracts from spent growth medium of Pseudomonas sp. RIT 623 were tested against two Gram-negative ( E. coli ATCC 25922 and P. aeruginosa ATCC 27853) and two Gram-positive ( B. subtilis BGSC 168 and S. aureus ATCC 25923) type strains to assess antibiotic activity. The antibiotic assays demonstrated that extracts of Pseudomonas sp. RIT 623 were able to inhibit the growth of the four strains. The active compound was separated using diethyl ether in a multi-solvent extraction and reverse phase chromatography. The bioactive compound/s were subsequently eluted in two consecutive fractions corresponding to approximately 16–22% acetonitrile, indicative of polar compound/s.

Six endophytic bacteria were isolated from Saccharum sp (sugarcane) grown in the parish of Westmoreland on the island of Jamaica located in the West Indies. Whole genome sequence and annotation of the six bacteria show that three were from the genus Pseudomonas and the other three were from the genera Pantoea, Pseudocitrobacter, and Enterobacter. A scan of each genome using the antibiotics and secondary metabolite analysis shell (antiSMASH4.0) webserver showed evidence that the bacteria were able to produce a variety of secondary metabolites. In addition, we were able to show that one of the organisms, Enterobacter sp RIT418 produces N-acyl-homoserine lactones (AHLs), which is indicative of cell-cell communication via quorum sensing (QS).

Objective In order to isolate and identify bacteria that produce potentially novel bactericidal/bacteriostatic compounds, two ponds on the campus of the Rochester Institute of Technology (RIT) were targeted as part of a bioprospecting effort. Results One of the unique isolates, RIT 452 was identified as Exiguobacterium sp. and subjected to whole-genome sequencing. The genome was assembled and in silico analysis was performed to predict the secondary metabolite gene clusters, which suggested the potential of Exiguobacterium RIT452 for producing antibiotic compounds. Extracts of spent growth media of RIT452 were active in disc diffusion assays performed against four reference strains, two Gram-negative (E. coli ATCC 25922 and P. aeruginosa ATCC 27853) and two Gram-positive (B. subtilis BGSC 168 and S. aureus ATCC 25923). Differential extraction and liquid chromatography was used to fractionate the extracts. Efforts to identify and elucidate the structure of the active compound(s) are still ongoing.

Exiguobacterium sp. RIT 452 is of biotechnological importance given its potential for antibiotic production.