GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE315nnn/GSE315928/primaryOK200TranscriptomicsHomo sapiensExpression profiling by high throughput sequencinghttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE315928GEOGSEfalseDifferential T cell clonal dynamics underlie outcomes to frontline chemoimmunotherapy in advanced gastric cancer [paired scRNA/TCR-seq]The addition of aPD1 to 5-FU/platinum in advanced gastric cancer (GC) yields variable responses. To understand cooperativity between chemotherapy and immunotherapy, we previously reported a phase II trial sequentially adding pembrolizumab to 5-FU/platinum. In this study, we use single-cell RNA- and TCR-sequencing to analyze 66,813 T cells from primary tumor biopsies pre-treatment, post-chemotherapy, and post-immunotherapy in 33 patients. We observed greater abundance, persistence, and recruitment of T cells with predicted tumor-reactivity in patients with prolonged progression-free survival (slow progressors). Increased B cell abundance and predicted B cell to T cell interactions supported T cell memory and co-stimulation, providing a mechanism for increased abundance and persistence of progenitor-exhausted and tumor-reactive T cells in slow progressors. T cell clones emerging in the tumor after immunotherapy were in the blood before treatment only in slow progressors. Our study thus highlights pre-treatment and early chemotherapy-induced T cell dynamics and B cell to T cell interactions that may drive durable response to chemoimmunotherapy in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 sapiens