Apart from cancer cells, this microenvironment consists of various non-cancerous cells, including cancer-associated fibroblasts (CAFs) [6], endothelial cells (ECs) [7], pericytes [8], adipocytes [9], neurons [10], myeloid-derived suppressor cells (MDSCs) [11], a variety of immune and inflammatory cells (i.e., macrophages, CD8+ T cells [12–15], CD4+ T cells [16–18], regulatory T cells (Tregs) [19, 20], B cells [21], neutrophils [22], dendritic cells (DCs) [23] and natural killer (NK) cells [24]), and structural components like the extracellular matrix (ECM) [25]. Here, CD4 is linked to cancer.