Immunologic Assessment of Tumors from a Race-matched Military Cohort Identifies Mast Cell Depletion as a Marker of Prostate Cancer Progression

Elucidating the cellular immune components underlying aggressive prostate cancer, especially among African American (AA) men who are disproportionately affected by this disease compared with Caucasian American (CA) men, will support more inclusive precision medicine treatment strategies. We aimed to evaluate which immune-related genes and cell types are differentially expressed in AA tumors and how immunobiology impacts prostate cancer progression. We purified nucleic acid from tumor biopsies, obtained following radical prostatectomy, from 51 patients (AA = 26, CA = 25). Gene expression was measured using the NanoString platform from which we estimated immune cell abundances and assessed differences between groups based on clinicopathologic data. Product-limit estimates determined associations with biochemical recurrence (BCR)-free and metastasis-free survival. DVL2 and KLRC2 were significantly upregulated in CA tumors and were also associated with worse disease progression. No significant differences in immune cell abundances by race were observed. Highly significant reductions in abundances of mast cells versus tumor-infiltrating lymphocytes (TIL) were found in men with high-grade pathologies and in men who later developed metastases. Low ratios of mast cells versus TILs were associated with worse BCR-free survival and metastasis-free survival. Although estimated immune cell abundances were not different by race, we identified genes involved in metabolism and natural killer cell functions that were differentially expressed between AA and CA tumors. Among the entire cohort, depletion of mast cells within prostatectomy tumors was characteristic of advanced disease and susceptibility to disease progression.

Significance

Our findings demonstrate that there are immune-related genes and pathways that differ by race. Impaired intratumoral cellular immune composition, especially for TIL-normalized mast cells, may be vital in predicting and contributing to prostate cancer disease progression.

Abstract 3805: Immunologic transcript and cell type evaluation of prostate tumors from a military cohort of African American and Caucasian American patients

Background: Health and racial disparities in prostate cancer place African American (AA) men at greater risk of developing and having a poorer outcome from the disease, especially at a younger age compared to Caucasian American (CA) men. This incidence is also reflected among active-duty service members, and patient biospecimens obtained from an equal access healthcare setting at the Walter Reed National Military Medical Center provide a valuable resource for the evaluation of cancer health disparities. The objectives of this study are to identify immunobiological differences influencing prostate cancer disparities and to elucidate the immune cell profiles of patient tumors associated with advanced disease.

Methods: Patients provided written consent to both biospecimen and clinical database collection under IRB-approved protocols. Fresh frozen tumor biopsy tissues were collected ex vivo, following radical prostatectomy. Total tumor RNA was amplified by PCR-based multiplexed target enrichment, and barcode-tagged transcripts were quantified using NanoString technology. Raw and relative abundances of immune cells were determined using published deconvolution algorithms. Differential expression of immune-related genes and cell type contrasts were evaluated for correlation with clinico-pathologic features.

Results: Genes regulating metabolism and innate immune responses were differentially expressed between AA and CA prostate tumors (AA n=26, CA n=25). Comparing high vs. low expression of each of these top genes, two were associated with biochemical recurrence (BCR)-free survival. Most immune cell subtypes did not differ significantly between AA and CA, but mast cells appeared to be enriched within AA tumors. When cell types were stratified by clinical and pathologic variables, we identified consistent trends in immune cell content that changed with increasing diagnostic age, PSA group, Grade Group, Gleason Sum, and with disease progression as defined by future development of BCR and/or metastasis.

Conclusions: Attention should be directed toward observed immunobiological differences based on race and other clinico-pathologic factors at the time of radical prostatectomy. Patient-centered studies mindful of existing health disparities will aid in diagnostic and therapeutic strategies that are inclusive of an increasingly diverse US and US military population.

Disclaimer: The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views, opinions or policies of the USUHS, HJF, the DoD or the Departments of the Army, Navy, or Air Force. Mention of trade names, commercial products, or organizations does not imply endorsement by the U.S. Government.

IRB protocol: DBS.2019.032 (Ref Number 930187)

Citation Format: Cara C. Schafer, Jiji Jiang, Sally Elsamanoudi, Darryl Nousome, Denise Young, Yingjie Song, Isabell Sesterhenn, Gregory Chesnut, Shyh-Han Tan. Immunologic transcript and cell type evaluation of prostate tumors from a military cohort of African American and Caucasian American patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3805.

Myeloid-Derived Suppressor Cells Impair B Cell Responses in Lung Cancer through IL-7 and STAT5

Myeloid-derived suppressor cells (MDSCs) are known suppressors of antitumor immunity, affecting amino acid metabolism and T cell function in the tumor microenvironment. However, it is unknown whether MDSCs regulate B cell responses during tumor progression. Using a syngeneic mouse model of lung cancer, we show reduction in percentages and absolute numbers of B cell subsets including pro-, pre-, and mature B cells in the bone marrow (BM) of tumor-bearing mice. The kinetics of this impaired B cell response correlated with the progressive infiltration of MDSCs. We identified that IL-7 and downstream STAT5 signaling that play a critical role in B cell development and differentiation were also impaired during tumor progression. Global impairment of B cell function was indicated by reduced serum IgG levels. Importantly, we show that anti-Gr-1 Ab-mediated depletion of MDSCs not only rescued serum IgG and IL-7 levels but also reduced TGF-β1, a known regulator of stromal IL-7, suggesting MDSC-mediated regulation of B cell responses. Furthermore, blockade of IL-7 resulted in reduced phosphorylation of downstream STAT5 and B cell differentiation in tumor-bearing mice and administration of TGF-β-blocking Ab rescued these IL-7-dependent B cell responses. Adoptive transfer of BM-derived MDSCs from tumor-bearing mice into congenic recipients resulted in significant reductions of B cell subsets in the BM and in circulation. MDSCs also suppressed B cell proliferation in vitro in an arginase-dependent manner that required cell-to-cell contact. Our results indicate that tumor-infiltrating MDSCs may suppress humoral immune responses and promote tumor escape from immune surveillance.

Indoleamine 2,3-dioxygenase regulates anti-tumor immunity in lung cancer by metabolic reprogramming of immune cells in the tumor microenvironment

Indoleamine 2,3-dioxygenase (IDO) has been implicated in immune evasion by tumors. Upregulation of this tryptophan (Trp)-catabolizing enzyme, in tumor cells and myeloid-derived suppressor cells (MDSCs) within the tumor microenvironment (TME), leads to Trp depletion that impairs cytotoxic T cell responses and survival; however, exact mechanisms remain incompletely understood. We previously reported that a combination therapy of gemcitabine and a superoxide dismutase mimetic promotes anti-tumor immunity in a mouse model of lung cancer by inhibiting MDSCs, enhancing polyfunctional response of CD8⁺ memory T cells, and extending survival. Here, we show that combination therapy targets IDO signaling, specifically in MDSCs, tumor cells, and CD8⁺ T cells infiltrating the TME. Deficiency of IDO caused significant reduction in tumor burden, tumor-infiltrating MDSCs, GM-CSF, MDSC survival and infiltration of programmed death receptor-1 (PD-1)-expressing CD8⁺ T cells compared to controls. IDO^−/− MDSCs downregulated nutrient-sensing AMP-activated protein kinase (AMPK) activity, but IDO^−/− CD8⁺ T cells showed AMPK activation associated with enhanced effector function. Our studies provide proof-of-concept for the efficacy of this combination therapy in inhibiting IDO and T cell exhaustion in a syngeneic model of lung cancer and provide mechanistic insights for IDO-dependent metabolic reprogramming of MDSCs that reduces T cell exhaustion and regulates anti-tumor immunity.

ERK/MAPK regulates ERRγ expression, transcriptional activity and receptor-mediated tamoxifen resistance in ER+ breast cancer

Selective estrogen receptor modulators such as tamoxifen (TAM) significantly improve breast cancer-specific survival for women with estrogen receptor-positive (ER+) disease. However, resistance to TAM remains a major clinical problem. The resistant phenotype is usually not driven by loss or mutation of the estrogen receptor; instead, changes in multiple proliferative and/or survival pathways over-ride the inhibitory effects of TAM. Estrogen-related receptor γ (ERRγ) is an orphan member of the nuclear receptor superfamily that promotes TAM resistance in ER+ breast cancer cells. This study sought to clarify the mechanism(s) by which this orphan nuclear receptor is regulated, and hence affects TAM resistance. mRNA and protein expression/phosphorylation were monitored by RT-PCR and western blotting, respectively. Site-directed mutagenesis was used to disrupt consensus extracellular signal-regulated kinase (ERK) target sites. Cell proliferation and cell-cycle progression were measured by flow cytometric methods. ERRγ transcriptional activity was assessed by dual-luciferase promoter-reporter assays. We show that ERRγ protein levels are affected by the activation state of ERK/mitogen-activated protein kinase, and mutation of consensus ERK target sites impairs ERRγ-driven transcriptional activity and TAM resistance. These findings shed new light on the functional significance of ERRγ in ER+ breast cancer, and are the first to demonstrate a role for kinase regulation of this orphan nuclear receptor.

The dual targeting of immunosuppressive cells and oxidants promotes effector and memory T-cell functions against lung cancer

We have recently demonstrated that the combination of gemcitabine and a superoxide dismutase mimetic protects mice against lung cancer by suppressing the functions of myeloid-derived suppressor cells and by activating memory CD8⁺ T-cell responses. Persistent memory cells exhibited a glycolytic metabolism, which may have directly enhanced their effector functions. This combinatorial therapeutic regimen may reduce the propensity of some cancer patients to relapse.

Enhancement of antitumor immunity in lung cancer by targeting myeloid-derived suppressor cell pathways

Chemoresistance due to heterogeneity of the tumor microenvironment (TME) hampers the long-term efficacy of first-line therapies for lung cancer. Current combination therapies for lung cancer provide only modest improvement in survival, implicating necessity for novel approaches that suppress malignant growth and stimulate long-term antitumor immunity. Oxidative stress in the TME promotes immunosuppression by tumor-infiltrating myeloid-derived suppressor cells (MDSC), which inhibit host protective antitumor immunity. Using a murine model of lung cancer, we demonstrate that a combination treatment with gemcitabine and a superoxide dismutase mimetic targets immunosuppressive MDSC in the TME and enhances the quantity and quality of both effector and memory CD8(+) T-cell responses. At the effector cell function level, the unique combination therapy targeting MDSC and redox signaling greatly enhanced cytolytic CD8(+) T-cell response and further decreased regulatory T cell infiltration. For long-term antitumor effects, this therapy altered the metabolism of memory cells with self-renewing phenotype and provided a preferential advantage for survival of memory subsets with long-term efficacy and persistence. Adoptive transfer of memory cells from this combination therapy prolonged survival of tumor-bearing recipients. Furthermore, the adoptively transferred memory cells responded to tumor rechallenge exerting long-term persistence. This approach offers a new paradigm to inhibit immunosuppression by direct targeting of MDSC function, to generate effector and persistent memory cells for tumor eradication, and to prevent lung cancer relapse.

Abstract 3570: Phospho-dependent regulation of ERRγ expression, transcriptional activity, and Tamoxifen resistance in ER+ breast cancer

Selective estrogen receptor modulators (SERMs) such as Tamoxifen (TAM) can significantly improve breast cancer-specific survival for women with ER-positive (ER+) disease. However, resistance to TAM remains a major clinical problem. Estrogen-related receptor gamma (ERRγ) is an orphan nuclear receptor with broad, structural similarities to classical ER that is widely implicated in the transcriptional regulation of energy homeostasis. We previously reported that ERRγ is upregulated during the acquisition of TAM resistance in ER+ breast cancer cell lines, exogenous expression of ERRγ is sufficient to induce TAM resistance, and ERRγ mRNA is significantly increased in tumor samples from women with ER+ breast cancer who relapse following TAM treatment.

Because ERRγ has no known ligand, our recent studies have focused on understanding how the expression and activity of this orphan nuclear receptor is regulated, and how this contributes to the TAM resistant phenotype. We have found that TAM-resistant breast cancer cells in which endogenous ERRγ is upregulated show a concomitant hyper activation of p44/p42 ERK. Furthermore, ERK activity (but not that of JNK or p38 MAPK) directly enhances ERRγ protein stability via Serines 57, 81, and/or 219 of the receptor. Phospho-deficient ERRγ is impaired in its ability to induce TAM resistance, and this is associated with a significant reduction in transcriptional activity at the estrogen-related response element (ERRE) half-site, in particular.

This led us to hypothesize that ERRγ action at ERREs is most relevant to the development of TAM resistance. We examined a meta-list of validated, ERRE-containing ERR target genes in association with distant metastasis-free survival (DMFS) within 5 years of primary diagnosis in each of 3 publicly available clinical datasets comprised of ER+ breast cancer patients treated with TAM, and obtained a list of 37 differentially expressed targets. The proximal promoter regions of these 37 genes are enriched for binding sites for ELK1, a well-known ERK substrate. Sub-network analysis reveals enrichment of genes whose protein products regulate the mitochondrial unfolded protein response (UPRmito). We also performed differential dependency network (DDN) analysis in an independent dataset using the full meta-list of ERRγ target genes and also identified genes associated with UPRmito. These data suggest a potentially novel role for ERK-mediated regulation of ERRγ in mitochondrial protein folding in TAM-resistant breast cancer.

Citation Format: Rebecca B. Riggins, Mary M. Heckler, Hemang Thakor, Cara C. Schafer, Salendra Singh, Ye Tian, Yuriy Gusev, Subha Madhavan, Yue Wang. Phospho-dependent regulation of ERRγ expression, transcriptional activity, and Tamoxifen resistance in ER+ breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3570. doi:10.1158/1538-7445.AM2013-3570

Abstract LB-29: Erk-mediated phosphorylation of the orphan nuclear receptor ERRγ regulates receptor stability and contributes to Tamoxifen resistance in ER+ breast cancer

Estrogen receptor alpha-positive (ER+) breast tumors comprise ∼70% of annually diagnosed breast cancers in the United States. While pro-tumorigenic ER signaling can be blocked by endocrine therapies that either inhibit the receptor directly (Tamoxifen) or prevent synthesis of its ligand (aromatase inhibitors), de novo and acquired resistance to ER-targeted therapies is a major barrier to the successful treatment of ER+ breast cancer. One of the most common mechanisms of acquired or de novo endocrine resistance in ER+ breast cancer is increased reliance on alternative pro-proliferative and pro-survival pathways that circumvent ER. We have been studying the role of the orphan nuclear receptor estrogen-related receptor gamma (ERRγ) in Tamoxifen-resistant breast cancer, increased expression of which induces Tamoxifen-resistant proliferation in multiple ER+ breast cancer cell lines. We have also reported that i. endogenous ERRγ shows increased levels of serine phosphorylation in Tamoxifen-resistant breast cancer cells, ii. this coincides with increased activation of extracellular signal-regulated kinase 2 (ERK2), and iii. pharmacological inhibition of the MEK/ERK pathway reduces ERRγ phosphorylation and transcriptional activity. This lead us to hypothesize that ERK-mediated phosphorylation of the orphan nuclear receptor ERR contributes to Tamoxifen resistance in ER+ breast cancer.

One way in which ERK-mediated phosphorylation can regulate its substrates is through changes in target protein stability. Co-transfection of wild-type ERRγ with either a constitutively active MEK (MEK-DD) or wild-type ERK2 led to an increase in ERRγ expression. Conversely, treatment of cells with the MEK inhibitor U0126 reduced transfected ERRγ expression. These data are also supported by mRNA data publicly available through ONCOMINE showing that i. relative to MCF7, BT-474 cells (which contain amplified HER2 and very high levels of active ERK) express significantly increased levels of ERRγ, and ii. treatment of BT-474 cells with the MEK inhibitor PD0325901 reduces ERRγ expression. To confirm that ERK-mediated phosphorylation of ERRγ regulates receptor stability, we performed site-directed mutagenesis to change multiple Serine residues within ERK consensus sites to Alanine. These Ser-to-Ala ERRγ mutants are expressed at lower levels when compared to the wild-type receptor, and co-transfection with MEK-DD is unable to increase their expression. Altogether, these data strongly suggest that direct ERK-mediated phosphorylation of ERR positively stabilizes receptor expression. Ongoing studies are addressing the biochemical and biological consequences of ERK-mediated ERRγ phosphorylation in the context of Tamoxifen-resistant breast cancer; putative mechanisms include receptor dimerization, DNA binding, and co-factor recruitment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-29. doi:10.1158/1538-7445.AM2011-LB-29