Preliminary Study on GZMA- and GSDMB-Associated Pyroptosis and CD8+ T Cell-Mediated Immune Evasion in Skin Cutaneous Melanoma.

Background: Skin cutaneous melanoma (SKCM) is a life-threatening malignancy, and pyroptosis-mediated inflammatory response is associated with SKCM progression. We aimed to uncover the underlying pathogenesis of SKCM based on pyroptosis features.

Method: The single-cell and bulk RNA-seq data and clinical information of SKCM patients were downloaded from the TCGA and GEO databases, and the REACTOME_ PYROPTOSIS.v2024.1.Hs.gmt from the MSigDB database was used for Gene Set Enrichment Analysis (GSEA). Differentially expressed gene (DEG) analysis was performed utilizing the "limma" R package, and the "GSVA" R package was used for the analysis of pyroptosis pathway activation. In addition, scRNA-seq analysis and cell communication analysis were carried out by employing the "Seurat" R package and "CellChat" R package, respectively. Gene expression was measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR), while cell counting kit-8 (CCK-8), wound healing, and Transwell assays were carried out to assess cell proliferation, migration, and invasion, respectively.

Results: DEGs analysis detected no significant pyroptosis-related DEGs. Analysis of the expression of two representative pyroptosis genes (GZMA and GSDMB) revealed that GZMA was significantly upregulated in the SKCM tissues, but the expression of GSDMB was downregulated. The pyroptosis pathway was not activated in the tumor group. In addition, we observed that high expression of GZMA and GSDMB was closely associated with a favorable outcome in SKCM. The two genes were downregulated in SKCM cells, while the overexpression of GZMA significantly impaired the proliferation, migration, and invasion ability of SKCM cells. Nine main cell subpopulations were identified, and GZMA was specifically overexpressed in CD8+ T cells. Gene function analysis revealed that specific genes of CD8+ T cells were enriched in cell death-related and inflammation activation pathways. Cell communication demonstrated that CD8+ T cells interacted with melanocytes through the CD99-CD99 and HLA-C-KIR2DL3 ligand-receptor pairs.

Conclusion: Based on the pyroptosis features in SKCM, this study found that blocking GZMA proteins in CD8+ T cells within melanocytes may be the underlying pathogenesis for tumor immune escape in cancer.