Ursolic acid sensitizes cisplatin-resistant HepG2/DDP cells to cisplatin via inhibiting Nrf2/ARE pathway.
BACKGROUND
Combinations of adjuvant sensitizers with anticancer drugs is a promising new strategy to reverse chemoresistance. Ursolic acid (UA) is one of the natural pentacyclic triterpene compounds known to have many pharmacological characteristics such as anti-inflammatory and anticancer properties. This study investigates whether UA can sensitize hepatocellular carcinoma cells to cisplatin.


METHODS
Cells were transfected with nuclear factor erythroid-2-related factor 2 (Nrf2) small interfering RNA and Nrf2 complementary DNA by using Lipofectin 2000. The cytotoxicity of cells was investigated by Cell Counting Kit 8 assay. Cell apoptosis, cell cycle, reactive oxygen species, and mitochondrial membrane potential were detected by flow cytometry fluorescence-activated cell sorting. The protein level of Nrf2, NAD(P)H quinone oxidoreductase 1 (NQO1), glutathioneS-transferase (GST), and heme oxygenase-1 (HO-1) was detected by Western blot analysis.


RESULTS
The results showed that the reverse index was 2.9- and 9.69-fold by UA of 1.125 μg/mL and 2.25 μg/mL, respectively, for cisplatin to HepG2/DDP cells. UA-cisplatin combination induced cell apoptosis and reactive oxygen species, blocked the cell cycle in G0/G1 phase, and reduced the mitochondrial membrane potential. Mechanistically, UA-cisplatin dramatically decreased the expression of Nrf2 and its downstream genes. The sensibilization of UA-cisplatin combination was diminished in Nrf2 small interfering RNA-transfected HepG2/DDP cells, as well as in Nrf2 complementary DNA-transfected HepG2/DDP cells.


CONCLUSIONS
The results confirmed the sensibilization of UA on HepG2/DDP cells to cisplatin, which was possibly mediated via the Nrf2/antioxidant response element pathway.
School of Life Sciences, Sun Yat-sen University; Center for Regenerative and Translational Medicine.
Shouhai
S
Wu
School of Life Sciences, Sun Yat-sen University.
Tianpeng
T
Zhang
Department of Pharmacy, The Second Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, People's Republic of China.
Jingsheng
J
Du
D000970:Antineoplastic Agents / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D061745:Antioxidant Response Elements / Q000235:genetics; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy*; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D056945:Hep G2 Cells; D006801:Humans; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D014315:Triterpenes / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D000097245:Ursolic Acid
D000970:Antineoplastic Agents; D000975:Antioxidants; D002945:Cisplatin; D051267:NF-E2-Related Factor 2; D034741:RNA, Small Interfering; D014315:Triterpenes; D000097245:Ursolic Acid
Nrf2/ARE; chemoresistance; cisplatin; liver cancer; ursolic acid