Specifically, CDK2 expression was positively correlated with macrophages (all r > 0.03284, p < 0.002), dendritic cells (all r ≥ 0.13, p < 0.0003), CD4+ T cells (all r > 0.07, p < 0.002), CD8+ T cells (all r > 0.09, p < 0.004), neutrophils (all r > 0.21, p < 0.001), and B cells (all r > 0.11, p < 0.000) in lung adenocarcinomas, liver hepatocellular carcinoma, head and neck cancers, and breast invasive carcinoma (Supplementary Figure S2, Table 2). Here, CDK2 is linked to head and neck cancer.