After that, 20 samples were used in order to examine the expression of TRF1, TRF2, POT1, ATR, ATM, Chk1 and Chk2. From the results (Fig 3A), it can be seen that ATR and Chk1 are significantly more expressed in CRC tissues compared to their adjacent mucosa. This evidence concerns the gene CHEK1 and colorectal carcinoma.