Anticancer Activity of Metformin, an Antidiabetic Drug, Against Ovarian Cancer Cells Involves Inhibition of Cysteine-Rich 61 (Cyr61)/Akt/Mammalian Target of Rapamycin (mTOR) Signaling Pathway
Authors: Bin Wang
Huixiao Chen
Fengli Zhang
Lixiao Yang
Jing Du
Journal: Medical Science Monitor (2018)
Discipline: CLINICAL MEDICINE
Keywords: Ovarian cancer; Cyr61; metformin; apoptosis; cell migration
Affiliations: Infertility Center, Qilu Hospital, Shandong University, Jinan, Shandong, China (mainland)., Department of Obstetrics and Gynecology, Liaocheng People's Hospital, Liaocheng, Shandong, China (mainland).

Abstract:  BACKGROUND Ovarian cancer is considered one of the lethal cancers responsible for high mortality and morbidity across the world. The prognosis and the survival rate of ovarian cancer is far from decent. Cysteine-rich 61 (Cyr61) also known as CCN1, is a member of CCN-family of growth factors, reported to be significantly overexpressed in several malignancies which include, but are not limited to, ovarian cancer. Recent studies have revealed that women with type 2 diabetes mellitus have an elevated risk of ovarian cancer. Hence, administration of an antidiabetic drug with anticancer effects such as metformin may act as an effective therapeutic regime against ovarian cancer. MATERIAL AND METHODS Cell viability and apoptosis were examined by MTT and Annexin V/PI double staining respectively. Cell migration was determined by Boyden Chamber assay. Transient knockdown of Cyr61 in ovarian cancer cells was achieved by transecting the cells with siRNA for Cyr61using Lipofectamine 2000. RESULTS Our results indicated that treatment of ovarian cancer cells with metformin caused significant downregulation of Cyr61 protein expression levels ultimately favoring apoptosis. Transient knockdown of Cyr61 resulted in the inhibition of cell proliferation and migration. This was also associated with the concomitant downregulation of pAkt and pmTOR confirming the role of Cyr61 as an upstream modulator of Akt signaling. Conversely the extracellular supplementation of recombinant Cyr61 attenuates the cytotoxic properties of metformin in ovarian cancer cells. CONCLUSIONS Taken together, we concluded that metformin exhibits anticancer effects and Cyr61 acts as a direct target for metformin in ovarian cancer cells. 

Retracted: Yes

PubPeer comments:
 *[below]* Figure 3A from [Zhang et al (2018)] .  Metformin inhibits invasiveness of ovarian cancer cells. (A) Invasion was determined by the Boyden Chamber assay. *[above]* Figure 7 from [Ding Chen (2018)] .  Effect of carvone on cell migration as determined by Boyden chamber assay . ![file] , 
 *[right]* Figure 4E from [Zhang et al (2018)] .  Effect of Cyr61 on oncogenic potential and PI3K Akt mTOR axis in ovarian cancer cells. .... (E) PI3K Akt mTOR axis in OVCAR-3 cells.. *[left]* Figure 8 from [Ding Chen (2018)] .  Effect of carvone at IC50 on the expression of P38MAPK. The results indicate that carbone at 20u2009u03bcM could inhibit the expression of p-P38. However, the expression of P38 remained more or less unchanged . ![file] , 
 *[right]* Figure 1B from [Zhang et al (2018)] .  Metformin induces apoptosis in ovarian cancer cells. ... (B) Apoptosis assay for OVCAR-3 cells treated with metformin as determined by Annexin V PI double staining. *[left]* Fig 4 from [Zeng et al (2019)] .  Annexin V PI staining showing apoptotic CH157-MN cell percentage at indicated concentrations of chrysophanol. ![file] For added comparison, [left] Fig 5B from [Bi et al (2018)] .  Effect of indicated doses of genistein on apoptosis (A) DAPI staining (B) Estimation of apoptotic Mia-PaCa2 cell populations a indicated doses by annexin V PI using flow cytometry . *[right]* Figure 6 from [Zhang et al (2018b)] .  Annexin V PI showing apoptotic cell populations. .. The Figure shows that safranal triggered apoptosis at IC50 (20u03bcu039c). ![] , 
 #1 Fig 3A again: ![] Another sighting! Figs 7 and 8 from [Ma et al (2019)] .  Effect of plumbagin on the migration of AGS gastric cancer cells as depicted by transwell assay ...  Effect of plumbagin on the invasion of AGS gastric cancer cells as depicted by transwell assay. The figure shows that 8 u03bcM dose of plumbagin led to significant inhibition of cell invasion. ![] , 
 Retracted [25 March 2021] .  An editorial decision has been made to retract this manuscript due to breach of publishing guidelines, following the identification of non-original and manipulated figures. ,