Androgen Receptor Antagonism Alters Myeloid Cells in Tumor Progression

Study Background and Research Question

Prostate cancer remains a leading malignancy, with androgen deprivation therapy (ADT) and direct androgen receptor (AR) antagonists like enzalutamide forming the backbone of advanced disease management. While these interventions initially suppress tumor growth by inhibiting androgen-driven proliferation, resistance eventually develops, leading to castration-resistant prostate cancer (CRPC) and poor prognosis. Most mechanistic studies focus on tumor-intrinsic adaptations, such as AR mutations or pathway reactivation. However, the contribution of the tumor microenvironment, particularly AR-expressing myeloid cells—including tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs)—to therapeutic resistance remains insufficiently explored. Consiglio et al. (2020) address this knowledge gap by asking: How does systemic AR antagonism influence myeloid cell function, metabolism, and their role in tumor progression? [source_type: paper][source_link: https://doi.org/10.1158/2326-6066.CIR-19-0371]

Key Innovation from the Reference Study

The central innovation of Consiglio et al. lies in demonstrating that AR antagonism with enzalutamide does not merely act on tumor cells but also reprograms the immune microenvironment—specifically, by enhancing the immunosuppressive and tumor-promoting functions of myeloid cells. Notably, this effect persists even in AR-independent tumor models, revealing a previously underappreciated, systemic consequence of AR-targeted therapy. The study further identifies a metabolic axis—namely, suppression of mitochondrial respiration and increased glycolysis in myeloid cells—as the mechanistic driver of this phenotype, mediated by the MPC/AMPK pathway. This work reframes resistance to AR antagonism as a multicellular, microenvironmental process rather than a solely tumor cell–intrinsic phenomenon [source_type: paper][source_link: https://doi.org/10.1158/2326-6066.CIR-19-0371].

Methods and Experimental Design Insights

The authors employed both pharmacological and genetic approaches to dissect AR's role in myeloid cells. Using the AR-independent MC-38 colon tumor model and the TRAMP C2 prostate tumor model in mice, they systemically administered enzalutamide and also engineered myeloid cell–specific AR knockouts. Tumor growth was assessed in both immunocompetent and immunodeficient backgrounds. Functional assays included co-injection of MDSCs (either treated with enzalutamide or genetically AR-deficient) with tumor cells, and measurement of adaptive immune responses. Comprehensive metabolic profiling of myeloid cells was performed, focusing on mitochondrial respiration and glycolytic parameters, with further investigation into the involvement of the mitochondrial pyruvate carrier (MPC) and AMP-activated protein kinase (AMPK) signaling. Transcriptional analyses included key immunosuppressive markers such as VEGF and Arg1.

Protocol Parameters

• assay: Flow cytometric quantitation of myeloid subsets | value_with_unit: >100,000 events/sample | applicability: murine tumor-infiltrating cells | rationale: ensures robust detection of rare immunosuppressive subsets | source_type: workflow_recommendation
• assay: Enzalutamide dosing | value_with_unit: 10 mg/kg, daily, oral | applicability: murine tumor models | rationale: mirrors clinically relevant exposure for AR antagonism | source_type: paper [source_link: https://doi.org/10.1158/2326-6066.CIR-19-0371]
• assay: DAPI (hydrochloride) nuclear staining | value_with_unit: 0.1-1 μg/mL | applicability: fixed and live cell analysis | rationale: enables discrimination of nucleated versus non-nucleated events in flow cytometry or imaging | source_type: product_spec [source_link: https://www.apexbt.com/dapi-hydrochloride.html]
• assay: Seahorse mitochondrial stress test | value_with_unit: 4-6 replicate wells/sample | applicability: metabolic profiling of sorted myeloid populations | rationale: increases statistical power for detecting metabolic shifts | source_type: workflow_recommendation

Core Findings and Why They Matter

Consiglio et al. found that enzalutamide, despite suppressing AR signaling in tumor cells, paradoxically increased tumor growth in vivo—even when tumor cells lacked AR. This effect was contingent on an intact immune system and was recapitulated by adoptively transferring enzalutamide-treated or AR-deficient MDSCs with tumor cells into mice. Immunosuppressive myeloid phenotypes were enhanced, as evidenced by increased VEGF and Arg1 expression and greater inhibition of adaptive immunity [source_type: paper][source_link: https://doi.org/10.1158/2326-6066.CIR-19-0371]. Metabolically, AR antagonism in myeloid cells suppressed mitochondrial respiration (as measured by oxygen consumption rate) and increased glycolysis, a shift previously associated with pro-tumorigenic myeloid function. Mechanistically, these effects depended on MPC/AMPK signaling, suggesting that AR modulates bioenergetics to restrain immunosuppressive activity.

These findings matter because they redefine resistance to AR-targeted therapies as a systemic process involving host immune cells, not just tumor-intrinsic alterations. This systemic perspective has immediate implications for therapy design, highlighting the risk of inadvertently promoting tumor progression by reprogramming the tumor microenvironment. It also suggests metabolic pathways in myeloid cells as potential combinatorial targets.

Comparison with Existing Internal Articles

The reference study's rigorous use of flow cytometry and DNA visualization for the identification and quantification of myeloid subsets aligns with best practices detailed in internal resources on DAPI (hydrochloride) as a chromosome staining reagent. That article provides atomic-level guidance for DNA visualization in histochemistry and flow cytometry, supporting the robust identification of nucleated immune cell subsets required for immunophenotyping workflows. Moreover, scenario-driven optimization with DAPI (hydrochloride) outlines evidence-based protocols for cell cycle analysis and viability in immunological assays, which are foundational for both the reference study's quantitation of myeloid cell populations and their functional assessment. These internal articles collectively emphasize the need for high-purity, reproducible DNA visualization tools—such as 4',6-diamidino-2-phenylindole hydrochloride—when characterizing heterogeneous immune cell populations in the tumor microenvironment.

Limitations and Transferability

While the findings are compelling, several limitations must be acknowledged. The study is performed exclusively in murine models, and the extent to which myeloid cell–specific AR signaling similarly influences human tumor microenvironments requires further validation. Additionally, tumor models used include both AR-independent and AR-dependent lines, but the spectrum of human tumor heterogeneity is broader. The transferability of metabolic targeting strategies in myeloid cells to clinical practice is thus at an early stage. Moreover, while DAPI (hydrochloride) and related minor groove DNA binding dyes are established for cell cycle analysis dye protocols and chromosome staining reagent workflows, translating these findings to human samples necessitates rigorous optimization and validation [source_type: workflow_recommendation].

Research Support Resources

For researchers seeking to replicate or extend these findings, accurate identification and quantification of nucleated myeloid populations is critical. DAPI (hydrochloride) (SKU C3362) offers a robust, DNA-specific fluorescent probe suitable for both flow cytometry and histochemical DNA visualization in tumor and immune cell profiling. As detailed in product specifications and internal reviews, high-purity DAPI facilitates reproducible discrimination of cell populations and supports cell cycle analysis dye protocols central to immunophenotyping workflows [source_type: product_spec][source_link: https://www.apexbt.com/dapi-hydrochloride.html]. For further mechanistic or protocol guidance, APExBIO provides validated reagents to support high-sensitivity, multiparameter cell analysis in cancer immunology research.