Salinomycin sensitizes cancer cells to the effects of doxorubicin and etoposide treatment by increasing DNA damage and reducing p21 protein.
OBJECTIVE
Salinomycin (Sal) has recently been shown to inhibit various cancer stem cells. Here, we investigated whether Sal could sensitize cancer cells to the effects of doxorubicin (DOX) or etoposide (ETO).


METHODS
Using the Comet assay, immunocytochemistry and Western blot analysis, we assessed the ability of Sal to increase DNA breakage. We performed a cell proliferation assay to determine cell viability, cellular detachment, increased pre-G1 region, Annexin V staining and TUNEL assay to measure the ability of Sal to increase apoptosis.


RESULTS
Sal increased DNA breakage and phosphorylated levels of p53 and H2AX. Sal also induced the formation of DNA foci with pH2AX and 53BP1. Furthermore, Sal increased the sensitivity of cancer cells to the apoptotic effects of DOX or ETO. We found that pH2AX, pBRCA1, p53BP1 and pChk1 levels were greatly increased after co-treatment of Sal with DOX or ETO. The level of anti-apoptotic p21 protein was increased by DOX or ETO but decreased by Sal, which increased proteasome activity.


CONCLUSIONS
This is the first study to report that Sal increases DNA damage, and this effect plays an important role in the increased apoptosis caused by Sal. Overall, we demonstrated that the ability of Sal to sensitize cancer cells to the effects of DOX or ETO is associated with an increase in DNA damage and a decrease in anti-apoptotic protein p21 levels. These results may contribute to the development of Sal-based chemotherapy for cancer patients receiving DOX or ETO treatment.
Research Institute, National Cancer Center, Ilsan-gu, Goyang-si, Gyeonggi-do, South Korea.
Ju-Hwa
JH
Kim
Minji
M
Chae
Won Ki
WK
Kim
You-Jin
YJ
Kim
Han Sung
HS
Kang
Hyung Sik
HS
Kim
Sungpil
S
Yoon
D017304:Annexin A5 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D020552:Comet Assay; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects*; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000494:pharmacology*; D005260:Female; D056945:Hep G2 Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011714:Pyrans / Q000494:pharmacology*; D012509:Sarcoma; D014594:Uterine Neoplasms; D000095662:Polyether Polyketides
D017304:Annexin A5; D000970:Antineoplastic Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004317:Doxorubicin; D005047:Etoposide; D046988:Proteasome Endopeptidase Complex; D011714:Pyrans; C493956:CDKN1A protein, human; C010327:salinomycin; D000095662:Polyether Polyketides