CCND1 and cancer: In the present study, among the genes simultaneously up-regulated or down-regulated in cancer and neurodegeneration, the CTG codon encoding leucine was the most preferred codon for APP, CCND1, and PTPA, while AGG was the most preferred codon for CCNE1. Nine, 16, 4, and 7 codons were overrepresented in APP, CCND1, CCNE1, and PTPA gene transcripts, respectively.