Aims: 

Circadian system is involved in control of cell proliferation and apoptosis. Mice with Per1 and Per2 deletion showed a marked increase in tumour development and reduced apoptosis. The aim of our study was to measure expression of human Per2 in patients who underwent surgery for colorectal carcinoma.

Methods: 

Our study included 24 patients of both sexes with progressing colon cancer. All patients were exposed to a standard hospital practice and exposed to light from 6:00 until 21:00 daily. The protocol was explained to each patient and informal consent was obtained. Tissue samples were taken at the time of surgery. They were collected from the tumour as well as from the proximal (at least 10 cm) and distal (at least 2 cm from the tumour) parts of the surgery. Surgery was performed during morning hours. Samples were put into liquid N₂ and kept at -80°C until RNA extraction. Expression of Per2 mRNA was performed by real time PCR. Ribosomal S17 gene was used as a reference gene.

Results: 

Expression of Per2 was substantially lower in tumours classified as G1 in comparison with G2. Moreover, there was a significant negative correlation between Per2 expression and tumour staging Expression of Per2 did not correlate with localization of the tumour in the proximal, transversal or distal colon.

Conclusion: 

Data demonstrated significant hPer2 deregulation in tumour tissue in comparison with ectomised tissue without malignancy in patients with colorectal carcinoma and suggest one way how the circadian system can influence tumourigenesis.

Supported by grant APVV-20-022704.