Context: The high resistance rate and high recurrence rate of progesterone only as a treatment for endometrial cancer (EC) limit its clinical application. Metformin (MET) may have antitumor ability. Combining MET and medroxyprogesterone acetate (MPA) may strengthen their inhibitory effects on proliferation of EC cells, but MET's mechanisms remain unclear.
Objective: The study intended to identify the specific molecular mechanism that MET combined with MPA uses against EC progression.
Design: The research team performed a controlled animal study.
Setting: The study took place at Xuzhou Medical University in Xuzhou, China.
Animals: The animals were16 female non-obese diabetic-severe combined immunodeficient (NOD-SCID) nude mice, about 12 to 16 g in weight.
Interventions: The research team divided randomly, the mice into four groups and induced EC in all groups, four in each group: (1) The control group which received received normal saline, (2) the MPA group, which received 100 mg/kg of MPA; (3) the MET group, which received metformin at the rate of 200 mg/kg, each gavage volume was 0.1ml; (4) the MET+MPA group, which received 100 mg/kg of MPA and 200 mg/kg of MET.
Outcome measures: The research team: (1) used a CCK-8 kit, an EdU assay, and a flow-cytometry assay to measure cancer-cell proliferation, count, and viability; determine the cell cycle; and measure apoptosis; (2) performed a Western blot analysis to determine the expression of the PR, CD133, pAkt, totalAkt, p-mTOR, and totalTOR antibodies; and (3) determined the size and volume of tumors in vivo and used immunohistochemical staining to determine expression of the Ki67 protein.
Results: The MET+MPA group had a significantly lower number of cancer cells than the MET or MDA groups (both P < .001). That group also had significantly more stagnated cancer cells in the G0/G1 phase and significantly fewer cancer cells in the S phase or G2/M phase control, MET, or MPA groups (all P < .01). The MET+MPA group's PCNA and Ki-67 protein expression was significantly lower than that of the MET and MPA group. The EDU assay yielded similar results. Additionally, the MET+MPA group had significantly higher PR expression than that of to MET or MPA group (both P < .001). The MET and MPA groups' expression of CD133, p-Akt, and p-mTOR were significantly lower than those of the control group, while the MET+MPA group's levels were significantly lower than those of the MET and MPA groups. In-vivo experiments revealed that the MET and MPA groups did show decreased tumor size and volume. The MET+MPA group had tumor weights that were significantly lower and tumor volumes were significantly smaller than those of the MET and MPA groups (all P < .001). Immunohistochemical analysis revealed that the MET+MPA group's levels of the Ki-67 antigen were significantly lower than those of the MET and MPA groups.
Conclusions: MET inhibited the proliferation of EC cells by increasing MPA-sensitivity, which was dependent on the inhibition of the CD133 expression and the Akt/mTOR pathway. In addition, if MET acts as an effective progestin sensitizer, it certainly offers promising therapeutic prospects for patients with early-stage EC or overgrown endometrium who have fertility requirements.