Evaluation of Period 2 gene (PER-2) biologic profile in advanced colorectal cancer (ACC) patients treated with chronomodulated chemotherapy

Background: 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 patients (pts) was linked to a worse prognosis (Iacobelli S, ASCO 2008). The aim of this 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), and 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 was performed. 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 yrs; median liver involvement 53%; cetuximab used in 38% of pts; liver resection: 42%. Response to chemotherapy: PR 61%, SD 25.4%, PD 10.2%(2.4% not evaluable). Biological data: pts with PER-2 loss (-) expressed more frequently EGFR (73%) (p<0.0001); ERβ1 (77%)(p=0.07); ERβ2 (88.5%)(p<0.0001),Cyclin D1 (69%)(p=0.06) and β-catenin(84.6%)(P=0.02). PER-2(-) was also associated to was also associated to high miR-206 and miR-192 expression. Explorative multiple correspondence analysis showed that response to chemotherapy was observed in pts with a biological profile characterized by PER-2 expression (+), EGFR (-), ERβ1 (-), β-catenin (-) and low miR-206 expression. 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.