Tumor-derived Vimentin as a novel biomarker for distinct subtypes predicting adjuvant chemotherapy resistance and T-cell-inflamed phenotype in small cell lung cancer.

Despite recent progress in subtype classification for small cell lung carcinoma (SCLC), little is known about the biomarker for triple-negative (ASCL1, NEUROD1, and POU2F3 negative) tumors. The long-term survival, adjuvant chemotherapy (ACT) response, and immune milieu in different SCLC subtypes have also not been well established. Here, we retrospectively collected a large cohort of 192 primary SCLC tumors and reported that ASCL1-, NEUROD1- and POU2F3-dominant subtypes counted for 61.38%, 19.31%, and 6.21%, respectively. Subtype intra-tumoral heterogeneity and co-expression at the single-cell level existed substantially. The expression of tumor-derived Vimentin (VIM) was nearly restricted to triple-negative SCLC tumors (15/19, 78.9%) while YAP1 expression was distributed widely in other subtypes. The SCLC subtyping model was independently prognostic of OS and RFS ( <  0.001 and  = 0.043). In particular, patients with ASCL1-positive SCLC tumors can benefit more from ACT, and VIM-positive tumors did the opposite. Compared with other subtypes, the VIM-dominant SCLC subtype was associated with abundant but functionally impaired CD4 and CD8 T-cells, which highly expressed inhibitory checkpoints and potentially benefit from PD-L1 blockade therapy. Our study showed that tumor-derived SCLC-V subtype could independently predict ACT response. The distinct immune landscape between subtypes may help inform personalized immune therapeutic approaches.