Finally, 18 common critical proteins, i.e. AKT1, BCL2L1, CCND1, CDH1, CDKN2A, CTNNB1, EGF, EGFR, ERBB2, HRAS, IL6, JUN, KRAS, NOTCH1, SNAI1, STAT3, TNF, and TP53, remained as the core proteins of the three types of cancers. Here, STAT3 is linked to cancer.