For example, CD6, a crucial gene for T-cell activation, is identified as a favourable prognostic marker in multiple cancers, such as breast invasive carcinoma (BRCA), cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), head and neck squamous cell carcinoma (HNSC), and skin cutaneous melanoma (SKCM), as shown in Fig. 3b. This evidence concerns the gene CD6 and invasive breast carcinoma.