PER1 and gastric cancer: Herein, to test the hypothesis that the polymorphisms of CNFL genes may affect the prognosis and clinical outcome of GC, we assessed the effects of thirteen functional SNPs in PER1, PER2, PER3, CRY1 and CRY2 on survival time of 1030 Chinese GC patients (704 in the training set, 326 in the independent validation set) who received radical resection treatment.