CDK4 and cancer: In a further analysis, we determined the alteration frequencies of CCND1/CDK4/PLK1/CD44 gene signatures in multiple cancer types, and we then used a mutually exclusivity panel analysis, which is a sub-tool of the cBioportal software, and found the rest of the altered genes within the entire set that co-occurred with CCND1/CDK4/PLK1/CD44 signatures, at a threshold with p < 0.001 as significant (Figure 6B–E, and accompanying table).