PER2 and breast carcinoma: In their study, western blotting showed that the expression of PER1 and PER2 decreased in the rhythm group, whereas the expression of breast carcinoma amplified sequence 4 (BCAS4), tubulin beta-2B chain (TUBB2B), and Roof Plate-Specific Spondin-4 (RSPO4) increased in the breast cancer group.