PER2 and cancer: The PER1, PER2, and PER3 genes regulate cell growth, proliferation, and apoptosis [15,16], CRY1 and CRY2 regulate the transcription G1/S and G2/M cell cycle checkpoints [17], while BMAL1 and NPAS2 inhibit the proliferation and invasion of cancer cells by suppressing the c-Myc transcription factor [18].