To validate our genomic findings showing that T cell infiltration was correlated with responses to ICB in only the second-line patients, we stained 39 patient samples (including the 35 used for mRNA analysis plus 4 additional patients whose RNA quality was not adequate) for INSM1 to mark SCLC tumor cells and CD8 for cytotoxic T cells on the same section (Supplementary Figure S7). Here, CD8A is linked to neoplasm.