CD4 and cancer: The crucial role of the tumor immune microenvironment (TIME) in cancer progression has been widely established, and the prognostic impact of the density of infiltrating tumor immune cells, such as CD4+/CD8+ T cells, natural killer (NK) cells, regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs), is a central concept in TIME study [12,13,14].