Who is the heater of desert-type gastric cancer that transforms a “cold” tumor into a “hot” tumor?

This study demonstrates for the first time that photodynamic therapy converts “cold” tumors to “hot” tumors in gastric cancer and improves the efficacy of immunotherapy. Flow cytometry, immunohistochemistry and transcriptome sequencing were used to identify changes in the immune environment before and after PDT. 122 patients with advanced gastric cancer before and after photodynamic therapy were collected and analyzed. 1) 21 (63.6%) of the 33 GC patients had turned from immune desert type to immune-infiltrating type after PDT.2) The numbers of CD3+ T, CD4+ T, CD8+ T cells, total macrophages, M1-macrophages and PD-L1+ cells had significantly increased after PDT, and PD-L1 expression and PD-1 checkpoint pathway were implicated.3) Statistics for group of immune-infiltrating GC (27 cases) and group of immune-deserted GC (6 cases) indicate that the former has a significantly higher ORR than the latter (77.8% vs 16.7%, P=0.01). PDT is the heater of desert-type gastric cancer that transforms a “cold”tumor into a “hot” tumor.