Using microfluidic models to evaluate whether monocyte preconditioning plays a role in tumor-associated macrophage mediated resistance to hormone therapy in men with prostate cancer.

Abstract

228 Background: While men with metastatic castrate-resistant prostate cancer benefit greatly from 2nd generation androgen targeted therapies (ATTs), the utility of these therapies is inevitably limited by the development of resistance. Tumor associated macrophages (TAMs) are a myeloid immune cell population within the prostate tumor microenvironment (TME) that have been shown to play an integral role in development of ATT-resistance. However, the pathways that underlie TAM-mediated ATT resistance remain under investigation. In particular, many TAMs within the TME are derived from circulating monocytes and it is not yet clear whether the pathways driving TAM-mediated resistance are activated exclusively within the TME or if the activation of critical resistance pathways begins while the cells are circulating as monocytes. In this study, we utilized novel microscale technologies to investigate the transcriptome of monocytes and macrophages derived from patients progressing and responding to ATTs as well as the degree to which the macrophages promote ATT resistance in prostate tumor models. Methods: Primary monocytes were isolated from 22 men with prostate cancer who were either progressing or responding to 2ndgeneration ATTs. A portion of the monocytes from each patient were isolated for transcriptome analysis and the rest were differentiated into monocyte-derived macrophages (MDMs). MDMs were then cultured in monoculture or in co-culture with androgen-independent prostate tumor cells (22Rv1 and C42B). Each culture was then left untreated or treated with enzalutamide therapy. Following culture/treatment, each macrophage condition was isolated for transcriptome analysis and tumor cell populations from each condition were evaluated for treatment cytotoxicity. Results: Viability data from MDM-C42B co-culture demonstrated a 20% increase in tumor cell viability following enzalutamide treatment when C42B cells were cultured with primary MDMs from castrate-sensitive patients as compared to MDMs from castrate-resistant patients. Subsequent transcriptome analysis demonstrated key signatures in monocyte/macrophage populations that were associated ATT response. Conclusions: Leveraging a novel microfluidic culture platform known as Stacks, we were able to utilize primary, patient-derived cells to demonstrate that the role of TAMs in ATT resistance within the prostate TME is dependent, at least in part, on factors that are present prior to extravasation into the TME. Transcriptome analysis identified candidate pathways, which may be driving TAM-mediated differences in ATT response. These findings have the potential to lead to future use of circulating monocytes as a predictive biomarker as well as lead to the identification and targeting of ATT resistance pathways in patients.