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Aberrations of the fibroblast growth factor receptor (FGFR) family members are frequently observed in metastatic urothelial cancer (mUC), and blocking the FGF/FGFR signaling axis is used as a targeted therapeutic strategy for treating patients. Erdafitinib is a pan-FGFR inhibitor, which has recently been approved by the FDA for mUC with FGFR2/3 alterations. Although mUC patients show initial response to erdafitinib, acquired resistance rapidly develops. Here, we found that adipocyte precursors promoted resistance to erdafitinib in FGFR-dependent bladder and lung cancer in a paracrine manner. Moreover, neuregulin 1 (NRG1) secreted from adipocyte precursors was a mediator of erdafitinib resistance by activating human epidermal growth factor receptor 3 (ERBB3; also known as HER3) signaling, and knockdown of NRG1 in adipocyte precursors abrogated the conferred paracrine resistance. NRG1 expression was significantly downregulated in terminally differentiated adipocytes compared with their progenitors. Pharmacologic inhibition of the NRG1/HER3 axis using pertuzumab reversed erdafitinib resistance in tumor cells in vitro and prolonged survival of mice bearing bladder cancer xenografts in vivo. Remarkably, data from single-cell RNA sequencing revealed that NRG1 was enriched in platelet-derived growth factor receptor-A (PDGFRA) expressing inflammatory cancer-associated fibroblasts, which is also expressed on adipocyte precursors. Together, this work reveals a paracrine mechanism of anti-FGFR resistance in bladder cancer, and potentially other cancers, that is amenable to inhibition using available targeted therapies., Significance: Acquired resistance to FGFR inhibition can be rapidly promoted by paracrine activation of the NRG1/HER3 axis mediated by adipocyte precursors and can be overcome by the combination of pertuzumab and erdafitinib treatment. See related commentary by Kolonin and Anastassiou, p. 648., (©2024 The Authors; Published by the American Association for Cancer Research.)

The inflammatory microenvironment of solid tumors creates a protumorigenic milieu that resembles chronic inflammation akin to a subverted wound healing response. Here, we investigated the effect of converting the tumor microenvironment from a chronically inflamed state to one of acute microbial inflammation by injecting microbial bioparticles directly into tumors. Intratumoral microbial bioparticle injection led to rapid and dramatic changes in the tumor immune composition, the most striking of which was a substantial increase in the presence of activated neutrophils. In situ photoconversion and intravital microscopy indicated that tumor neutrophils transiently switched from sessile producers of VEGF to highly motile neutrophils that clustered to make neutrophil-rich domains in the tumor. The neutrophil clusters remodeled tumor tissue and repressed tumor growth. Single-cell transcriptional analysis of microbe-stimulated neutrophils showed a profound shift in gene expression towards heightened activation and antimicrobial effector function. Microbe-activated neutrophils also upregulated chemokines known to regulate neutrophil and CD8+ T-cell recruitment. Microbial therapy also boosted CD8+ T-cell function and enhanced the therapeutic benefit of checkpoint inhibitor therapy in tumor-bearing mice and provided protection in a model of tumor recurrence. These data indicate that one of the major effector mechanisms of microbial therapy is the conversion of tumor neutrophils from a wound healing to an acutely activated cytotoxic phenotype, highlighting a rationale for broader deployment of microbial therapy in the treatment of solid cancers., Significance: Intratumoral injection of microbial bioparticles stimulates neutrophil antitumor functions, suggesting pathways for optimizing efficacy of microbial therapies and paving the way for their broader utilization in the clinic., (©2023 The Authors; Published by the American Association for Cancer Research.)

Evolution of tumor cell phenotypes promotes heterogeneity and therapy resistance. Here we found that induction of CD73, the enzyme that generates immunosuppressive adenosine, is linked to melanoma phenotype switching. Activating MAPK mutations and growth factors drove CD73 expression, which marked both nascent and full activation of a mesenchymal-like melanoma cell state program. Proinflammatory cytokines like TNFα cooperated with MAPK signaling through the c-Jun/AP-1 transcription factor complex to activate CD73 transcription by binding to an intronic enhancer. In a mouse model of T-cell immunotherapy, CD73 was induced in relapse melanomas, which acquired a mesenchymal-like phenotype. We also detected CD73 upregulation in melanoma patients progressing under adoptive T-cell transfer or immune checkpoint blockade, arguing for an adaptive resistance mechanism. Our work substantiates CD73 as a target to combine with current immunotherapies, but its dynamic regulation suggests limited value of CD73 pretreatment expression as a biomarker to stratify melanoma patients. Cancer Res; 77(17); 4697-709. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Increasing evidence exists for the role of immunosuppressive adenosine in promoting tumor growth and spread in a number of cancer types, resulting in poor clinical outcomes. In this study, we assessed whether the CD73-adenosinergic pathway is active in melanoma patients and whether adenosine restricts the efficacy of clinically approved targeted therapies for commonly mutated BRAF V600E melanoma. In AJCC stage III melanoma patients, CD73 expression (the enzyme that generates adenosine) correlated significantly with patients presenting nodal metastatic melanoma, suggesting that targeting this pathway may be effective in advanced stage disease. In addition, dabrafenib and trametinib treatment of CD73 + BRAF V600E -mutant melanomas caused profound CD73 downregulation in tumor cells. Inhibition of BRAF and MEK in combination with the A2A adenosine receptor provided significant protection against tumor initiation and metastasis formation in mice. Our results suggest that targeting adenosine may enhance therapeutic responses for melanoma patients receiving targeted or immune-based therapies. Cancer Res; 77(17); 4684-96. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Elevated numbers of regulatory T cells (Treg) in patient tumors are known to inhibit efficient antitumor T-cell responses. To study the mechanisms controlling tumor rejection, we assessed different mouse models for Treg depletion. In Foxp3DTR knock-in mice, about 99% Treg depletion was achieved, resulting in complete rejection of transplanted HCmel12 melanomas in a CD8 + T-cell-dependent way. In contrast, about 90% Treg depletion obtained in BAC transgenic Foxp3.LuciDTR4 mice failed to induce complete rejection of HCmel12 melanomas, demonstrating that residual Tregs were able to control CD8 + T-cell responses against the tumor. Ninety-nine percent of Treg depletion provoked drastic changes in the tumor microenvironment, such as strong infiltration of CD8 + T cells and basophils. Intratumoral basophils enhanced CD8 + T-cell infiltration via production of chemokines CCL3 and CCL4; antibody-based blocking of these chemokines inhibited CD8 + T-cell infiltration. Therapeutic induction of basophilia by IL3/anti-IL3 antibody complexes, combined with transfer of CD8 + T cells, resulted in enhanced T-cell infiltration and tumor rejection. Our study identifies a critical role basophils play in tumor rejection and that this role can be exploited for therapeutic intervention. Cancer Res; 77(2); 291-302. ©2016 AACR., (©2016 American Association for Cancer Research.)

Human melanomas exhibit considerable genetic, pathologic, and microenvironmental heterogeneity. Genetically engineered mice have successfully been used to model the genomic aberrations contributing to melanoma pathogenesis, but their ability to recapitulate the phenotypic variability of human disease and the complex interactions with the immune system have not been addressed. Here, we report the unexpected finding that immune cell-poor pigmented and immune cell-rich amelanotic melanomas developed simultaneously in Cdk4R24C-mutant mice upon melanocyte-specific conditional activation of oncogenic BrafV600E and a single application of the carcinogen 7,12-dimethylbenz(a)anthracene. Interestingly, amelanotic melanomas showed morphologic and molecular features of malignant peripheral nerve sheath tumors (MPNST). A bioinformatic cross-species comparison using a gene expression signature of MPNST-like mouse melanomas identified a subset of human melanomas with a similar histomorphology. Furthermore, this subset of human melanomas was found to be highly associated with a mast cell gene signature, and accordingly, mouse MPNST-like melanomas were also extensively infiltrated by mast cells and expressed mast cell chemoattractants similar to human counterparts. A transplantable mouse MPNST-like melanoma cell line recapitulated mast cell recruitment in syngeneic mice, demonstrating that this cell state can directly reconstitute the histomorphologic and microenvironmental features of primary MPNST-like melanomas. Our study emphasizes the importance of reciprocal, phenotype-dependent melanoma-immune cell interactions and highlights a critical role for mast cells in a subset of melanomas. Moreover, our BrafV600E-Cdk4R24C model represents an attractive system for the development of therapeutic approaches that can target the heterogeneous tumor microenvironment characteristic of human melanomas., (©2015 American Association for Cancer Research.)

The development of therapeutic strategies which induce effective cellular antitumor immunity represents an important goal in cancer immunology. Here, we used the unique features of the genetically engineered Hgf-Cdk4(R24C) mouse model to identify a combination chemoimmunotherapy for melanoma. These mice develop primary cutaneous melanomas which grow progressively and metastasize in the absence of immunogenic foreign proteins such as oncogenes or antigens. Primary and metastatic tumors evade innate and adaptive immune defenses, although they naturally express melanocytic antigens which can be recognized by antigen-specific T cells. We found that primary melanomas continued to grow despite infiltration with adoptively transferred, in vivo-activated, tumor-specific CD8(+) T cells. To promote tumor immune defense, we developed a treatment protocol consisting of four complementary components: (a) chemotherapeutic preconditioning prior to (b) adoptive lymphocyte transfer and (c) viral vaccination followed by (d) adjuvant peritumoral injections of immunostimulatory nucleic acids. Lymphocyte ablation and innate antiviral immune stimulation cooperatively enhanced the expansion and the effector cell differentiation of adoptively transferred lymphocytes. The efficacy of the different treatment approaches converged in the tumor microenvironment and induced a strong cytotoxic inflammatory response enabling preferential recognition and destruction of melanoma cells. This combination chemoimmunotherapy caused complete regression of advanced primary melanomas in the skin and metastases in the lung with minimal autoimmune side effects. Our results in a clinically highly relevant experimental model provide a scientific rationale to evaluate similar strategies which unleash the power of innate and adaptive immune defense in future clinical trials.