This work found that BRAF/MEK inhibitors significantly upregulate TFAP2A, and identifies TFAP2A as a shared driver of both targeted therapy resistance and immunosuppression, offering a one-stone-two-bird strategy to overcome drug resistance and elicit antitumor immunity.
Abstract
Combination targeted therapy with BRAF/MEK inhibitors and immune therapy show promising therapeutic outcomes in melanoma; however, the development of drug resistance still represents a formidable challenge. Remaining unexplored is the possibility that BRAF/MEK inhibitors themselves inadvertently compromise the tumor immune microenvironment, limiting the efficacy of immunotherapy when it is used in combination with targeted inhibitors. Herein, we profiled the landscape of the BRAF regulatome identifying a novel transcription factor, TFAP2A, newly linking BRAF/MEK drug resistance to antitumor immunity. Specifically, we found that BRAF/MEK inhibitors significantly upregulate TFAP2A. Further, genetic disruption of TFAP2A overcomes BRAF/MEK-inhibitor resistance, promotes stromal enrichment, and enhances intratumoral infiltration of macrophages in an immune-compromised mouse model. In a syngeneic mouse model, TFAP2a knockout not only suppresses tumor growth but also induces potent anti-tumor tertiary lymphoid structures (TLSs). Single cell transcriptomics revealed that the absence of TFAP2A shapes the antitumor microenvironment with an influx of M1-like macrophages, CD8+ T cells and mature dendritic cells. By identifying TFAP2A as a shared driver of both targeted therapy resistance and immunosuppression, our work offers a one-stone-two-bird strategy to overcome drug resistance and elicit antitumor immunity.
This work establishes for the first time that BRAFi promotes myeloid-mediated induction of T cell activation, which is lost at resistance but can be rescued with the addition of CDDO- me, and provides the foundation for its potential use in combination therapies for melanoma.
Chen-Yu Wang, G. Torres, Helen C. Jarnagin et al.· Journal of Immunology· 0 citations
Therapeutic resistance remains a prevalent and intractable clinical challenge across a broad spectrum of human malignancies. Despite extensive investigations, the intricate molecular networks by which the tumor microenvironment (TME) mediates such resistance are not fully understood. In this study, we identified nucleotide-binding oligomerization domain-containing proteins 1 and 2 (NOD1/2) as pivotal regulators of adaptive resistance to diverse antitumor therapies, including immune checkpoint blockade (ICB), adoptive T-cell therapy, and cytotoxic chemotherapy. In murine tumor models, genetic ablation of NOD1/2 or receptor-interacting protein kinase 2 (RIPK2), as well as pharmacological inhibition of RIPK2, remodeled the TME by decreasing immunosuppressive macrophages and boosting CD8⁺ T cell infiltration and cytotoxicity. Mechanistically, NOD1/2 activation in macrophages upregulated programmed death-ligand 1 (PD-L1) expression via the RIPK2/NF-κB signaling axis, establishing an immunosuppressive TME that impaired CD8⁺ T cell-mediated antitumor immunity. Notably, in the clinically relevant setting of immunotherapy resistance, targeted suppression of NOD1/2 signaling in patient-derived peripheral blood mononuclear cells (PBMCs) restored and potentiated ICB responsiveness in patient-derived tumor organoids. Bioinformatic analyses further demonstrated that NOD1/2-associated gene signatures were significantly enriched in tumor-associated macrophages post-therapy. Our findings define NOD1/2 as a novel innate immune checkpoint that orchestrates therapy-induced adaptive resistance and highlight this pathway as a promising target to overcome treatment resistance in refractory cancers.
Xiduan Wei, Li Yang, Yuting Wang et al.· Signal Transduction and Targ...· 0 citations
Advanced BRAF-mutant cutaneous melanoma can be treated with targeted therapy when immune checkpoint inhibitors (ICIs) fail or are not a feasible option. Nevertheless, most patients do not achieve a durable response, highlighting the critical need for therapeutic partners that enhance the long-term efficacy of targeted therapy. Transcriptomic analysis of a BRAF-mutant melanoma model of acquired resistance identified P-selectin glycoprotein ligand-1 (PSGL-1) as a top-upregulated immune mediator upon resistance acquisition. PSGL-1 is a key regulator of CD8+ T cell exhaustion and differentiation, and its inhibition has been shown to enhance T cell function across multiple disease models. Based on these observations, we hypothesized that combined targeting of BRAF/MEK and PSGL-1 would improve anti-tumor responses. Here, we demonstrate that dual inhibition of BRAF/MEK and PSGL-1 elicits durable tumor control in a preclinical model of PD-1-refractory cutaneous melanoma. Single-cell RNA sequencing of the tumor microenvironment reveals robust reprogramming of intratumoral CD8+ T cells toward a less terminally differentiated, memory-like phenotype following combined BRAF/MEK and PSGL-1 targeting. Consistent with these findings, CD8+ T cells in the tumor-draining lymph nodes of PSGL-1-/- mice exhibit enhanced functionality and a less differentiated state of exhaustion when compared with wild-type mice. To extend these observations to a translationally relevant setting, we further show that antibody-mediated blockade of PSGL-1, in combination with BRAF/MEK inhibition, yields superior anti-tumor activity compared with either monotherapy. Collectively, these findings identify PSGL-1 as a promising therapeutic target to enhance the durability of targeted therapy and provide a strong rationale for future clinical evaluation.
O. E. El Naggar, Bn. Ha, ML Rakoto et al.· bioRxiv· 0 citations
Despite advancements in immunotherapy, more than half of melanoma patients will either not respond or will later relapse after treatment with immune checkpoint blockade (ICB). For later-stage patients, chemotherapy is an essential treatment modality, but tumor intrinsic cell survival mechanisms and an immunosuppressive tumor microenvironment often limit efficacy. We recently discovered that by upregulating the secretion of Pros1, tumor cells limit the response of macrophages to chemotherapy released tumor Damage Associated Molecular Patterns (DAMPs). By pharmacologically inhibiting Ptp1b, a signaling intermediary downstream of the Mer receptor, macrophage responsiveness to DAMPs can be restored. This is associated with increased macrophage M1 polarization and immune infiltration, as well as a 40-80% decrease in tumor volume in multiple preclinical models.
We hypothesize that because Ptp1b inhibition prevents tumor suppression of DAMP responsiveness, combining Ptp1b inhibition may improve the efficacy of multiple chemotherapies, particularly those that promote necrotic and immunogenic cell death. To test this, macrophages were co-cultured with murine melanoma cells (B16F10) and cisplatin, doxorubicin, or dacarbazine in the presence or absence of Ptp1b inhibitor via transwell assay, after determining the relative amounts of apoptosis/necrosis produced by each chemotherapy.
Preliminary results indicate that Ptp1b inhibition significantly increases macrophage pro-inflammatory gene expression by 7.5-fold in a setting of chemotherapy-induced tumor DAMP release. This indicates that inhibiting Ptp1b could synergistically improve chemotherapy effectiveness.
As Ptp1b inhibitors have a reasonable safety profile based on multiple clinical trials, combining Ptp1b inhibiting drugs with chemotherapy may be a novel way to restore the innate immune response during treatment while also improving patient outcomes.
NCI- RO1 CA262241(Ubil)
Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)
Oluwaseyi Omodiminiyi, Nestor Prieto-Dominguez, Eric Ubil· Journal of Immunology· 0 citations
Resistance to immunotherapy remains a major clinical challenge in TP53-mutant head and neck squamous cell carcinoma (HNSCC), a disease subset characterized by immune exclusion, high recurrence, and poor outcomes. Given the constitutive activation of PI3K/AKT/mTOR signaling in TP53-mutant HNSCC and its role in disease progression, we investigated whether the mTOR inhibition (mTORi) could overcome immune resistance and improve outcomes. We evaluated the effects of mTOR inhibitor everolimus in tumor microenvironment (TME) changes, including immune cell infiltration, immune checkpoint expression, and key pathways associated with immune suppression and angiogenesis, to define the mechanisms underlying TME remodeling. Everolimus significantly suppressed tumor growth in syngeneic HNSCC models. At the cellular level, everolimus significantly increased intratumoral CD8+ T cell and dendritic cell (DC) infiltration while reducing regulatory T cell (Treg) accumulation. Mechanistically, everolimus induced a cytokine/chemokine response, marked by increased TNF-α/CXCL10 expression, leading to enhanced immune infiltration. Everolimus also inhibited the HIF-1α/VEGFA pathway, a central driver of immune exclusion and myeloid-derived suppressor cell (MDSC) recruitment. Furthermore, everolimus treatment attenuated PD-1/PD-L1 signaling by reducing PD-1 and PD-L1 expression in T cells and tumor cells, thereby restoring T-cell cytotoxic competence. These findings demonstrate that mTORi with everolimus reverses multiple mechanisms of immune resistance and enhances anti-tumor T cell activity. Collectively, these results support mTORi as a rational therapeutic strategy for TP53-mutant HNSCC and for reprogramming the immune-resistant TME, particularly in patients who are likely to fail immunotherapy.
Priyatosh Nath, Alok R. Khandelwal, Chun Li et al.· Neoplasia· 0 citations
Small cell lung cancer (SCLC) is an aggressive malignancy with limited treatment options, and the integration of immune checkpoint inhibitors (ICIs) into treatment regimens has reshaped the therapeutic landscape. However, challenges such as rapid resistance and lack of effective predictive biomarkers remain. This review highlights the pivotal roles of biomarkers in SCLC, underscoring their contributions to treatment resistance across tumor-intrinsic mechanisms, immune landscape of the tumor microenvironment (TME) and systemic host factors. Tumor-intrinsic features, including molecular subtypes, genetic alterations such as TP53 and RB1 mutations, and tumor mutation burden (TMB), have shown varying associations with ICI efficacy. Notably, the SCLC-I (inflamed) molecular subtype appears more responsive to immunotherapy. Within the TME, programmed cell death ligand 1 expression, tumor-infiltrating lymphocytes (TILs), regulatory T cells, myeloid-derived suppressor cells, and tissue-associated cytokines and chemokines contribute to immune modulation. High CD8+ TILs are linked to better outcomes, while increased immunosuppressive populations often suppress anti-tumor response. Systemic factors, encompassing both tumor-derived (ctDNA, CTCs, tumor-derived EVs) and host-derived (circulating immune cell phenotypes, MHC expression, immune profile, baseline clinical characteristics) components, provide valuable insights into treatment response and prognosis. Further research is needed to validate biomarkers and investigate combination approaches to overcome resistance, offering hope for improved patient outcomes in SCLC.
Shuxing Wang, Xinrui Zhao, Yue-yue Zeng et al.· Critical reviews in oncology...· 0 citations
