CTLA4 and neoplasm: In cSCC, the CD103+CD39+CD8+TRM cells promote tumor metastasis and inhibit anti-tumor response by increasing IL-10 production and upregulating the expression of exhaustion markers like PD-1 and CTLA-4.205 A study revealed that the pre-existing TRM-like cells in lung tissues strengthened the recruitment and activation of host T cells within TME, and they also expressed high PD-1 and IFN-γ.641 In addition, the pre-existing CD8+TRM cells induced by cancer vaccines facilitate anti-tumor immunity in head and neck tumors.229