Checkpoint kinase‑1 inhibition and etoposide exhibit a strong synergistic anticancer effect on chronic myeloid leukemia cell line K562 by impairing homologous recombination DNA damage repair

by Selleckchem | Jul 25 2023

Leukemia, a malignant hematological disease, has poor therapeutic outcomes due to chemotherapeutic resistance. Increasing evidence has confirmed that the elevated capacity for DNA damage repair in cancer cells is a major mechanism of acquired chemotherapeutic resistance. Thus, combining chemotherapy with inhibitors of DNA damage repair pathways is potentially an ideal strategy for treating leukemia. Checkpoint kinase 1 (CHK1) is an important component of the DNA damage response (DDR) and is involved in the G2/M DNA damage checkpoint. In the present study, we demonstrated that shRNA‑mediated CHK1 silencing suppressed cell proliferation and enhanced the cytotoxic effects of etoposide (VP16) in the chronic myeloid leukemia (CML) cell line K562 through the results of CCK‑8, and comet assay. The results demonstrated that shRNA‑induced CHK1 silencing can override G2/M arrest and impair homologous recombination (HR) repair by reducing breast cancer susceptibility gene 1 (BRCA1) expression. Cells had no time, and thus limited ability, to repair the damage and were thus more sensitive to chemotherapy after CHK1 downregulation. Second, we tested the therapeutic effect of VP16 combined with CCT245737, an orally bioavailable CHK1 inhibitor, and observed strong synergistic anticancer effects in K562 cells. Moreover, we discovered that CCT245737 significantly prevented the G2/M arrest caused by acute exposure to VP16. Interestingly, CCT245737 inhibited both BRCA1 and Rad51, the most important component of the HR repair pathway. In conclusion, these results revealed that CHK1 is potentially an ideal therapeutic target for the treatment of CML and that CCT245737 should be considered a candidate drug.

Comments:

The information you provided describes a study investigating the potential therapeutic strategy for treating chronic myeloid leukemia (CML) by combining chemotherapy with inhibitors of DNA damage repair pathways, specifically targeting checkpoint kinase 1 (CHK1). Here's a breakdown of the key findings and conclusions of the study:

1. CHK1 silencing and etoposide (VP16) combination: The study used shRNA to silence CHK1 expression in the CML cell line K562. The results showed that CHK1 silencing suppressed cell proliferation and enhanced the cytotoxic effects of etoposide (VP16), a chemotherapeutic agent commonly used in leukemia treatment. This was demonstrated through the CCK-8 assay, which measures cell viability, and the comet assay, which assesses DNA damage.

2. Overriding G2/M arrest and impairing homologous recombination (HR) repair: CHK1 silencing was found to override the G2/M DNA damage checkpoint, a regulatory mechanism that allows cells to pause the cell cycle and repair DNA damage before proceeding to division. In addition, CHK1 downregulation reduced the expression of breast cancer susceptibility gene 1 (BRCA1), a protein involved in HR repair. As a result, the cells had limited time and ability to repair DNA damage, making them more sensitive to chemotherapy.

3. Therapeutic effect of VP16 combined with CHK1 inhibitor CCT245737: The study also examined the effects of combining VP16 with an orally bioavailable CHK1 inhibitor called CCT245737. The results showed strong synergistic anticancer effects in K562 cells when the two agents were used together. Notably, CCT245737 prevented the G2/M arrest caused by VP16 and inhibited both BRCA1 and Rad51, a key component of the HR repair pathway.

Based on these findings, the study suggests that CHK1 could be a promising therapeutic target for treating CML, and CCT245737, as a CHK1 inhibitor, should be considered as a potential candidate drug. The study provides evidence for the potential of combining chemotherapy with inhibitors of DNA damage repair pathways to overcome chemotherapeutic resistance in leukemia and highlights the importance of targeting CHK1 in this context.