PER2 and breast cancer: In our study, we identified a range of Bmal1-Per2 phase differences across and within various tissue types, where non-cancerous and osteosarcoma tissues exhibited consistent phase differences around 2π/3 (an 8-h lag in a 24-h cycle), whereas breast cancer subtypes generally showed minimal phase differences (2π), though with considerable variability (Fig. 2E,F).