Taken together, we demonstrated that the effect of CQ added to RSR inhibitors used as single agents for tumor treatment was not so clear—despite the induction of S phase and p-Chk1 level indicating the replication stress increase, the influence of the combination on cell proliferation resumption is uncertain as it was completely abrogated in MCF7 cells, with no significant effect in SKBR3 cells. The gene discussed is CHEK1; the disease is neoplasm.