Cthrc1-Mediated Megakaryocyte/Platelet Infiltration in the Tumor Microenvironment Promotes Immunotherapy Resistance in Escc

Background Elevated platelet counts are a common hematological abnormality in advanced cancer patients, driven by aberrant megakaryocyte proliferation and activation. We hypothesized that immunotherapy-resistant esophageal squamous cell carcinoma (ESCC) patients exhibit similar platelet/megakaryocyte dysregulation, which may contribute to immune evasion and treatment resistance. Methods We analyzed blood and tumor samples from immunotherapy-sensitive (TRG0–1, n = 23) and -resistant (TRG2–3, n = 23) ESCC patients (Cohort 1). Transcriptomic profiling (Cohort 2: 4 pairs) and tissue microarray analysis (Cohort 3: n = 131) identified CTHRC1 as a key mediator of megakaryocyte infiltration. Functional assays included megakaryocyte-ESCC adhesion models, PBMC co-culture, mass cytometry (CyTOF), and CTHRC1-LNP-mRNA vaccine development. In vivo efficacy was tested in murine ESCC models with combined anti-PD1 and CTHRC1-LNP-mRNA vaccine therapy. Results Immunotherapy-resistant ESCC patients showed elevated platelet counts, reduced MPV, and increased circulating megakaryocytes, indicating megakaryocytes/platelet dysfunction. CTHRC1, upregulated in resistant tumors, promoted megakaryocyte-ESCC adhesion via the αIIbβ3/PI3K/Rap1 axis, shielding tumor cells from immune attack. This adhesion induced T-cell exhaustion (naïve CD8 + ↓,Tregs ↑). We developed a CTHRC1-LNP-mRNA vaccine (>95% encapsulation, 81 nm size), which, combined with anti-PD1, suppressed tumor growth, enhanced immune activation (IFN-γ, IL-2↑), and reduced megakaryocyte infiltration in murine models, without significant toxicity. Conclusion Our findings reveal a novel mechanism by which CTHRC1-mediated megakaryocyte infiltration into the tumor microenvironment promotes immunotherapy resistance in ESCC. By facilitating megakaryocyte-ESCC adhesion and inducing T-cell exhaustion, CTHRC1 creates an immunosuppressive niche that shields tumor cells from immune attack. The CTHRC1-LNP-mRNA vaccine effectively reverses this resistance by eliminating aberrant megakaryocyte infiltration and restoring anti-tumor immunity, offering a promising combinatorial strategy for overcoming immunotherapy resistance in ESCC.