Alkan, H. K. | bioRxiv Science

bioRxiv2026

S100A9-Dependent CXCR2hi Neutrophils Mediate Systemic Immune Suppression and Checkpoint Resistance in Metastatic TNBC

Most high-dimensional studies of tumor-immune interactions focus on metastatic models, limiting insight into how immune remodeling in primary tumors shapes metastatic competence. Here, integrating single-cell RNA sequencing, CyTOF, and functional studies across metastatic (4T1) and non-invasive (EMT6) triple-negative breast cancer (TNBC) murine models, we define tumor state-specific immune programs that distinguish metastatic competence. Tumors with metastatic capacity uniquely drive early bone marrow expansion of CXCR2 neutrophils, which infiltrate primary tumors acquiring a CXCL2-producing phenotype that promotes EMT-associated cancer stem cell (CSC) plasticity. This program depends on TGF-{beta}/CEBPD-mediated induction of S100A9. Elevated CXCL2, together with G-CSF, establishes a feed-forward circuit that drives systemic neutrophil mobilization and recruitment to distant organs, where neutrophil-derived S100A8/A9 (calprotectin) promotes MET-driven CSC outgrowth and metastatic colonization. Clinically, gene signatures associated with CXCR2 neutrophils predict poor survival in TNBC patients, whereas monocyte/macrophage (CX3CR1) and T cell activation signatures correlate with improved outcomes. S100A9 ablation disrupts this cascade and enhances immunotherapy responsiveness, defining a TGF-{beta}/S100A9/CXCR2 axis linking immune remodeling, CSC plasticity and metastasis. HighlightsO_LIMetastatic TNBC engages a TGF-{beta}/C/EBP{delta}/S100A9 axis that expands CXCR2 neutrophils C_LIO_LINon-invasive EMT6 tumors retain a CX3CR1 monocyte/macrophage and T-cell landscape C_LIO_LICXCR2+ neutrophils in pre-metastatic niches suppress T cell response while promoting tumor cell proliferation C_LIO_LIS100A9 loss redirects myelopoiesis and potentiates anti-PD-L1 in TNBC models C_LI In BriefAlkan et al. dissect how tumor state programs the myeloid compartment in TNBC. Metastatic 4T1 tumors uniquely engage a TGF-{beta}/C/EBP{delta}/S100A9 axis driving CXCR2 neutrophil expansion and CXCL2/G-CSF-dependent systemic mobilization, coupling immune remodeling to EMT/MET cancer-stem-cell plasticity, while S100A9 loss restores CX3CR1 myeloid identity and unlocks checkpoint-inhibitor responsiveness.

cancer biology↗

bioRxiv2025

Co-targeting KRAS and Exportin1 as an effective therapeutic strategy for KRASG12D mutant pancreatic ductal adenocarcinoma

BackgroundSeveral KRASG12D inhibitors (KRASG12Di) are under clinical evaluation for pancreatic ductal adenocarcinoma (PDAC). However, as seen with other first generation KRAS inhibitors, resistance may limit their long-term efficacy, necessitating combination strategies to enhance therapeutic outcomes. Exportin 1 (XPO1), a nuclear transport protein overexpressed in PDAC, represents a therapeutic vulnerability in KRAS-mutant cancers. Here, we demonstrate that the second-generation XPO1 inhibitor Eltanexor synergizes with MRTX1133 to enhance its efficacy in multiple PDAC models. MethodsWe generated KRASG12Di-resistant PDAC cells and assessed their response to Eltanexor. The antiproliferative effects of MRTX1133 and Eltanexor combinations were evaluated in 2D and 3D in vitro PDAC models. The in vivo efficacy of the combination was tested in KRASG12D-mutant human and murine PDAC xenograft and allograft models. ResultsEltanexor sensitized MRTX1133-resistant PDAC cells to growth inhibition. In both 2D and 3D culture models, the combination of Eltanexor and MRTX1133 significantly reduced cell viability. Mechanistically, the combination treatment suppressed key KRAS downstream signaling molecules, including p-ERK, mTOR, p-4EBP1, DUSP6, and cyclin D1. Kinome analysis further revealed reduced MAPK-related kinase activity. Combining subtherapeutic doses of Eltanexor and MRTX1133 resulted in significant tumor regression and prolonged survival in PDAC xenograft and immunocompetent orthotopic allograft models. Moreover, maintenance therapy with Eltanexor prevented tumor relapse, yielding a durable antitumor response. ConclusionThis study demonstrates that Eltanexor overcomes resistance to MRTX1133 and enhances its efficacy in PDAC. The combination regimen may provide a durable therapeutic response while reducing the required dose of KRASG12D inhibitors, potentially delaying resistance and improving patient outcomes. Statement of Translational RelevancePDAC remains one of the deadliest malignancies, with limited effective therapies and dismal survival rates. The emergence of KRASG12D-selective inhibitors, such as MRTX1133, marks a critical advance for nearly 40% of PDAC patients harboring this oncogenic driver. However, inevitable emergence of adaptive or acquired resistance to KRAS inhibitors remains a major barrier to achieving durable clinical benefit. This study uncovers XPO1 inhibition as a rational and synergistic strategy to augment the antitumor efficacy of MRTX1133. By enhancing KRASG12D inhibitor activity and potentially reducing the required therapeutic dose, this combination approach offers a novel means to delay or overcome resistance. These findings provide a strong preclinical rationale for clinical trials evaluating KRAS inhibitors in combination with XPO1 inhibitors and may significantly improve outcomes for a substantial subset of PDAC patients who currently lack effective targeted treatment options.

cancer biology↗