Although POLA1 knockdown was also successfully performed in the colorectal cancer cell line RKO, we did not observe similar effects upon treatment with ATR or CHK1 inhibitors, respectively, in POLA1 depleted cells (data not shown), indicating that expectedly, the therapeutic targeting of POLA1 impaired or vice versa ATR impaired cells using the respective inhibitors will not unequivocally work in all cell lines. Here, CHEK1 is linked to colorectal cancer.