CD4 and neoplasm: For example, platinum-resistant OC that progresses within 6 months after platinum therapy exhibits a series of “cold tumor” features, namely, low infiltration of CD8 T-cell (Mariya et al., 2014) but increased activation of CD4 T-cell, increased infiltration of regulatory T-cell (Tregs) (Hao et al., 2018) and increased infiltration of PD-L1 cells (Hamanishi et al., 2015), known to promote peritoneal dissemination (Abiko et al., 2013), in which tumor cells are in an immunosuppressive microenvironment with enhanced proliferation and migration.