T cell-based immunotherapies have exhibited promising outcomes in tumor control; however, their efficacy is limited in immune-excluded tumors. Cancer-associated fibroblasts (CAFs) play a pivotal role in shaping the tumor microenvironment and modulating immune infiltration. Despite the identification of distinct CAF subtypes using single-cell RNA-sequencing (scRNA-seq), their functional impact on hindering T-cell infiltration remains unclear, particularly in soft-tissue sarcomas (STS) characterized by low response rates to T cell-based therapies. In this study, we characterize the STS microenvironment using murine models (in female mice) with distinct immune composition by scRNA-seq, and identify a subset of CAFs we termed glycolytic cancer-associated fibroblasts (glyCAF). GlyCAF rely on GLUT1-dependent expression of CXCL16 to impede cytotoxic T-cell infiltration into the tumor parenchyma. Targeting glycolysis decreases T-cell restrictive glyCAF accumulation at the tumor margin, thereby enhancing T-cell infiltration and augmenting the efficacy of chemotherapy. These findings highlight avenues for combinatorial therapeutic interventions in sarcomas and possibly other solid tumors. Further investigations and clinical trials are needed to validate these potential strategies and translate them into clinical practice.

Bladder cancer is the 10th most commonly diagnosed cancer in the world, accounting for around 573,000 new cases and 213,000 deaths in 2020. The current standard treatment for locally advanced bladder cancer is neoadjuvant cisplatin (NAC)-based chemotherapy followed by cystectomy. The significant progress being made in the genomic and molecular understandings of bladder cancer has uncovered the genetic alterations and signaling pathways that drive bladder cancer progression. These developments have led to a dramatic increase in the evaluation of molecular agents targeting at these alterations. One example is Erdafitinib, a first-in-class FGFR inhibitor being approved as second-line treatment for locally advanced or metastatic urothelial carcinoma with FGFR mutations. Immunotherapy has also been approved as second-line treatment for advanced and metastatic bladder cancer. Preclinical studies suggest targeted therapy combined with immunotherapy has the potential to markedly improve patient outcome. Given the prevalence of FGFR alternations in bladder cancer, here we review recent preclinical and clinical studies on FGFR inhibitors and analyze possible drug resistance mechanisms to these agents. We also discuss FGFR inhibitors in combination with other therapies and its potential to improve outcome.

Despite the remarkable clinical responses achieved with immune checkpoint blockade therapy, the response rate is relatively low and only a subset of patients can benefit from the treatment. Aberrant RNA accumulation can mediate IFN signaling and stimulate an immune response, suggesting that targeting RNA decay machinery might sensitize tumor cells to immunotherapy. With this in mind, we identified an RNA exoribonuclease, XRN1, as a potential therapeutic target to suppress RNA decay and stimulate antitumor immunity. Silencing of XRN1 suppressed tumor growth in syngeneic immunocompetent mice and potentiated immunotherapy efficacy, while silencing of XRN1 alone did not affect tumor growth in immunodeficient mice. Mechanistically, XRN1 depletion activated IFN signaling and the viral defense pathway; both pathways play determinant roles in regulating immune evasion. Aberrant RNA-sensing signaling proteins (RIG-I/MAVS) mediated the expression of IFN genes, as depletion of each of them blunted the elevation of antiviral/IFN signaling in XRN1-silenced cells. Analysis of pan-cancer CRISPR-screening data indicated that IFN signaling triggered by XRN1 silencing is a common phenomenon, suggesting that the effect of XRN1 silencing may be extended to multiple types of cancers. Overall, XRN1 depletion triggers aberrant RNA-mediated IFN signaling, highlighting the importance of the aberrant RNA-sensing pathway in regulating immune responses. These findings provide the molecular rationale for developing XRN1 inhibitors and exploring their potential clinical application in combination with cancer immunotherapy. Significance: Targeting XRN1 activates an intracellular innate immune response mediated by RNA-sensing signaling and potentiates cancer immunotherapy efficacy, suggesting inhibition of RNA decay machinery as a novel strategy for cancer treatment.

KDM6A, an X chromosome-linked histone lysine demethylase, was reported to be frequently mutated in many tumor types including breast and bladder cancer. However, the functional role of KDM6A is not fully understood. Using MCF10A as a model of non-tumorigenic epithelial breast cells, we found that silencing KDM6A promoted cell migration and transformation demonstrated by the formation of tumor-like acini in three-dimensional culture. KDM6A loss reduced the sensitivity of MCF10A cells to therapeutic agents commonly used to treat patients with triple-negative breast cancer and also induced TGFβ extracellular secretion leading to suppressed expression of cytotoxic genes in normal human CD8+ T cells in vitro. Interestingly, when cells were treated with TGFβ, de novo synthesis of KDM6A protein was suppressed while TGFB1 transcription was enhanced, indicating a TGFβ/KDM6A-negative regulatory axis. Furthermore, both KDM6A deficiency and TGFβ treatment promoted disorganized acinar structures in three-dimensional culture, as well as transcriptional profiles associated with epithelial-to-mesenchymal transition and metastasis, suggesting KDM6A depletion and TGFβ drive tumor progression. Implications: Our study provides the preclinical rationale for evaluating KDM6A and TGFβ in breast tumor samples as predictors for response to chemo and immunotherapy, informing personalized therapy based on these findings.

Soft-tissue sarcomas (STS) are characterized by abundant extracellular matrix (ECM) deposition, yet the functional contribution of specific ECM components remains poorly understood. In this study, we identify periostin (POSTN), a matricellular protein, as a regulator of sarcoma progression and the tumor immune microenvironment. Analysis of human sarcoma datasets revealed that high POSTN expression correlates with poor prognosis and elevated expression of ECM-related and myeloid cell–associated genes. In murine genetic models of sarcoma, tumors expressing high levels of Postn displayed enhanced expression of ECM genes and monocyte-recruiting cytokines. Functional silencing of Postnin vivo reduced tumor growth without altering tumor cell proliferation or intrinsic signaling pathways, suggesting a noncell-autonomous mechanism. Instead, Postn-deficient tumors showed increased infiltration of CD4+ and CD8+ T cells and reduced proportions of immunosuppressive myeloid cells, including tumor-associated macrophages (TAM). Single-cell RNA sequencing revealed that Postn silencing reprograms the myeloid compartment, increasing IFN-responsive and proinflammatory subsets. Mechanistically, recombinant POSTN promoted monocyte migration and maturation into macrophages in vitro, supporting its role as a chemoattractant and differentiation cue. Therapeutic neutralization of POSTN partially recapitulated the immunologic remodeling but was insufficient to reduce tumor burden as monotherapy. Significance: Our findings position POSTN as a key stromal regulator in STS, linking tumor-derived ECM components to immune evasion via myeloid cell recruitment and education. These results open avenues for targeting POSTN as an adjuvant strategy to enhance the efficacy of immunotherapies and overcome the immune-excluded phenotype of sarcoma.

Supplementary Data from KDM6A Depletion in Breast Epithelial Cells Leads to Reduced Sensitivity to Anticancer Agents and Increased TGFβ Activity