PER2 and cancer: Correlating to the oxygen tension-modulated alteration of clock-related transcripts, Per1, Per2 and Cry1 and those linked to protein chaperoning and immune function (e.g. Schlafen-3) (downregulated at 9% O2 compared to 20% O2 control: Table S3) we also observed a significant population of many cell cycle/cancer-related and immune-related canonical signaling pathways (Table S14), suggesting strong causative links between oxygen tension exposure in astrocytes and potential cancer/cell development/cell cycle regulatory issues [62].