CCND1 and cancer: As regards TCF7L2 variants, several studies have shown an association between some TCF7L2 variants with different types of cancer (24, 26, 29–32, 41), which is explained because the TCF4 protein, involved in the Wnt/β-catenin signaling pathway, acts as a transcription factor that induces expression of some oncogenes as CCND1 and MYC, involved in proliferation, apoptosis, invasion, and metastasis (9, 40).