Period 2 (PER-2) biologic profile in advanced colorectal cancer (ACC) patients (pts)

Circadian rhythms modulated by clock genes expression as the Period genes (PER-1, PER-2, PER-3) are involved in cancer growth. PER-2 loss in colorectal cancer cell lines and in animal models increases tumorigenesis by β-catenin and cyclin D activation (Wood P, Cancer Res 2008). PER-2 loss in ACC pts was linked to a worse prognosis (Iacobelli S, ASCO 2008). The aim of our study was to identify a PER-2 biological profile related to proliferative indexes and treatment activity. Moreover miRNA related to clock genes were studied as miR-219, target of CLOCK and B-MAL1, miR-206 which affect mammalian circadian clock, miR-132 acting at the SCN level. Methods: We retrospectively evaluated 59 ACC pts, treated with first line chronomodulated triplet combination (Irinotecan+Oxaliplatin+Folinic Acid+5-Fluorouracil) ± Cetuximab. Immunostaining for PER-2, EGFR, ERβ1, ERβ2, Cyclin D1, β-catenin, K-RAS and B-RAF mutations, miRNAs -206, -132, -192, -194, and -219 evaluated on FFPE tumor tissues and their expression levels by quantitative PCR were examined. Results: Clinical data: M/F 32/27; median age 57 y; liver involvment 53%; Cetuximab use: 38%; liver resection: 42%; response to first line chemotherapy: PR 61%, SD 25.4%, PD 10.2%; pts 2.4% not evaluable. Biological data: PER-2 negative (-) /positive (+) 44/56%; EGFR (+)/(-) 54/46%; KRAS wt/mut 75/25%; ERβ1 (-)/(+) 36/65%; ERβ2 (-)/(+) 39/61%; Cyclin D1 (-)/(+) 51/49%; β-catenin(-)/(+) 31/69%. PER-2(-) patients expressed more frequently EGFR (73%) (p>0.0001), ERβ1 (77%) (p=0.07), ERβ2 (88.5%) (p>0.0001), Cyclin D1 (69.2%) (p=0.06) and β-catenin (84.6%) (p=0.02). PER-2(-) was also associated to high miR-206, miR-192 and miR-219 expression. Explorative multiple correspondence analysis showed response to chemotherapy related to a profile including PER-2 (+), EGFR (-), ERβ1 (-), ERβ2 (-), β-catenin (-) and low expression of miR-206. Conclusions: Our data confirmed that: 1) PER-2 loss was associated to activation of cell proliferation confirming in vitro data; 2) PER-2 expression was linked to negative activation of cell proliferation, low miR-206 expression and response to chemotherapy.