Antitumor effects of metformin via indirect inhibition of protein phosphatase 2A in patients with endometrial cancer

[Megestrol acetate plus metformin for fertility-sparing treatment of atypical endometrial hyperplasia and early-stage endometrial adenocarcinoma: a prospective study]

OBJECTIVE

To evaluate the efficacy of medroxyprogesterone acetate (MA) plus metformin as the primary fertility-sparing treatment for atypical endometrial hyperplasia (AEH) and early-stage grade 1 endometrial adenocarcinoma (G1 EAC) and the recurrence rate after treatment.

METHODS

Sixty patients (aged 20-42 years) with AEH and/or grade 1 EAC limited to the endometrium were enrolled prospectively and randomized into two groups (n=30) to receive oral MA treatment at the daily dose of 160 mg (control) or MA plus oral metformin (850 mg, twice a day) for at least 6 months. The treatment could extend to 12 months until a complete response (CR) was achieved, and follow-up hysteroscopy and curettage were performed every 3 months. For all the patients who achieved CR, endometrial expressions of IGFBP-rP1, p-Akt and p-AMPK were detected immunohistochemically.

RESULTS

A total of 58 patients completed the treatment. After 9 months of treatment, 23 (76.7%) patients in the combined treatment group and 20 (71.4%) in the control group achieved CR; two patients in the control group achieved CR after converting to the combined treatment. The recurrence rate did not differ significantly between the control group and combined treatment group (30.0% vs 22.7%, P>0.05). Ten (35.7%) patients in the control group experienced significant weight gain of 5.7±6.1 kg, while none of the patients receiving the combined treatment exhibited significant body weight changes. Compared with the control group, the patients receiving the combined treatment showed enhanced endometrial expressions of IGFBP-rP1 and p-AMPK with lowered p-Akt expression.

CONCLUSION

Metformin combined with MA may provide an effective option for fertility-sparing treatment of AEH and grade 1 stage IA EAC, and the clinical benefits of metformin for controlling MA-induced weight gain and promoting endometrial expressions of IGFBP-rP1 and p-AMPK while inhibiting p-Akt expression warrants further study.

Development and evaluation of core-shell nanocarrier system for enhancing the cytotoxicity of doxorubicin/ metformin combination against breast cancer cell line

Breast cancer is the most invasive and life-threatening cancer in women. The treatment options are usually a combination of mastectomy, radiation therapy, hormonal therapy and chemotherapy. As a standard practice, doxorubicin (DOX) is one of the commonly used drugs for breast cancer treatment. However, DOX is known to have many harmful adverse effects including its cardiotoxicity. Hence, recent reports used metformin (MET), an anti-diabetic drug, as an adjuvant therapy to decrease the severity of DOX's adverse effects and to improve its ultimate therapeutic outcome. The current study is aimed at co-loading and enhancing the encapsulation efficiency of the hydrophilic DOX and MET in poly(lactic-co-glycolic acid) (PLGA) nanocapsules (NCs) with oil core for breast cancer treatment. The NCs were developed by single emulsification-solvent diffusion technique, and were optimized through using two types of oils, pluronics and PLGA (50:50) of different molecular weights followed by various physicochemical characterizations. The obtained DOX/MET-loaded NCs showed the size and polydispersity index (PDI) of 203.0 ± 3.4 nm and 0.081 ± 0.03, respectively with a surface charge of -2.15 ± 0.2 mV. The entrapment efficiency of DOX and MET were about 93.7% ± 2.9 and 70% ± 1.6, respectively. The developed PLGA core-shell NCs successfully sustained the DOX/MET release for more than 30 days. The in-vitro results showed a significant enhancement in DOX cytotoxic effect as well as a duplication in its apoptotic effect upon addition of MET for both free DOX/MET combination and DOX/MET-loaded PLGA NCs against MCF-7. Besides, flow cytometry demonstrated that the DOX/MET-loaded NCs possess their antitumor effect by preventing DNA replication and cell division. This study provides a promising facile, rapid and reproducible single emulsification-solvent diffusion technique for improving the encapsulation and release of hydrophilic drugs in nanocapsules for biomedical applications.

Cancer and diabetes: the interlinking metabolic pathways and repurposing actions of antidiabetic drugs

Cancers are regarded as one of the main causes of death and result in high health burden worldwide. The management of cancer include chemotherapy, surgery and radiotherapy. The chemotherapy, which involves the use of chemical agents with cytotoxic actions is utilised as a single treatment or combined treatment. However, these managements of cancer such as chemotherapy poses some setbacks such as cytotoxicity on normal cells and the problem of anticancer drug resistance. Therefore, the use of other therapeutic agents such as antidiabetic drugs is one of the alternative interventions used in addressing some of the limitations in the use of anticancer agents. Antidiabetic drugs such as sulfonylureas, biguanides and thiazolidinediones showed beneficial and repurposing actions in the management of cancer, thus, the activities of these drugs against cancer is attributed to some of the metabolic links between the two disorders and these includes hyperglycaemia, hyperinsulinemia, inflammation, and oxidative stress as well as obesity. Furthermore, some studies showed that the use of antidiabetic drugs could serve as risk factors for the development of cancerous cells particularly pancreatic cancer. However, the beneficial role of these chemical agents overweighs their detrimental actions in cancer management. Hence, the present review indicates the metabolic links between cancer and diabetes and the mechanistic actions of antidiabetic drugs in the management of cancers.

The Role of Hyperglycemia in Endometrial Cancer Pathogenesis

Endometrial cancer is one of the most common cancers in women worldwide and its incidence is increasing. Epidemiological evidence shows a strong association between endometrial cancer and obesity, and multiple mechanisms linking obesity and cancer progression have been described. However, it remains unclear which factors are the main drivers of endometrial cancer development. Hyperglycemia and type 2 diabetes mellitus are common co-morbidities of obesity, and there is evidence that hyperglycemia is a risk factor for endometrial cancer independent of obesity. This review aims to explore the association between hyperglycemia and endometrial cancer, and discuss the evidence supporting a role for increased glucose metabolism in endometrial cancer and how this phenotype may contribute to endometrial cancer growth and progression. Finally, the potential role of blood glucose lowering strategies, including drugs and bariatric surgery, for the treatment of this malignancy will be discussed.

New therapeutic approaches for the fertility-sparing treatment of endometrial cancer

This review seeks to describe new fertility-sparing endometrial cancer (EC) treatment strategies that take into consideration the medical and general health background of patients. We particularly focus on the application of metformin, which is a biguanide widely prescribed for treatment of type 2 diabetes mellitus. Fertility-sparing treatment using progestin is considered a standard treatment option for patients with atypical endometrial hyperplasia (AEH) and EC who desire to conceive. A previous meta-analysis of fertility-sparing treatments revealed a high remission rate; however, high rates of relapse persisted. Most young patients with AEH and EC who are subjected to fertility-sparing treatment have a background of obesity, insulin resistance and abnormal glucose tolerance complicated with polycystic ovary syndrome. Recently, metformin has been attracting more attention in the field of cancer research. Several in vitro and in vivo reports regarding the efficacy of metformin in EC management have accumulated. Thus far, the efficacy of combining metformin with progestin has been revealed in a single phase II study of medroxyprogesterone acetate in combination with metformin as a fertility-sparing treatment for patients with AEH or EC. In addition to improving the metabolic profile of patients with EC having metabolic disorders, metformin supplementation may improve the long-term oncological outcome of these patients. To date, many clinical trials employing progestin and metformin as a fertility-sparing treatment of AEH and EC are ongoing. In the near future, it is expected that the clinical advantage of metformin progestin combination therapy will be clarified.

Metformin rescues Parkin protein expression and mitophagy in high glucose-challenged human renal epithelial cells by inhibiting NF-κB via PP2A activation

Our preliminary research revealed that metformin, a classic anti-diabetic drug, could rescue Parkin protein expression and mitophagy in high glucose-challenged human renal epithelial cells in vitro, but the molecular mechanism remains to be explored. In the study, Human Renal Cortical Epithelial Cells (HRCEpiC) and Human Renal Proximal Tubular Epithelial Cells (HRPTEpic) were challenged with high glucose with or without metformin pre-treatment to monitor Parkin mRNA and protein expression level change. PRKN gene knockdown was performed by lentiviral-based shRNA delivery. Cell viability, apoptosis and mitophagy were monitored after treatment. Mitochondrial damage was evaluated by analyzing mitochondrial permeability transition pore opening, membrane potential change, mitochondrial superoxide accumulation and cytochrome C release. Protein levels of activating transcription factor 4 (ATF4), p53 phospho-Ser15, IκBα phosphor-Ser32, IKKα phosphor-Ser176/180 in whole cell lysate and nuclear entry of p50/p65 were assessed by western blot. Okadaic acid was used to inhibit protein phosphatase 2A (PP2A). The data suggested high glucose challenge significantly reduced PRKN gene expression, mitophagy, mitochondria integrity and cell viability in vitro, which was rescued by metformin co-treatment. The effects of metformin were crippled by PRKN gene knockdown. Metformin increased PRKN gene transcription while reducednuclear factor kappa B (NF-κB) activation but not that of p53 or ATF4. Inhibiting PP2A weakened NF-κB inhibition and PRKN induction by metformin in high glucose-challenged cells, reducing its mitochondrial protective and cytoprotective effect. So, we concluded thatmetformin protects human renal epithelial cells from high glucose-induced apoptosis by restoring Parkin protein expression and mitophagy via PP2A activation and NF-κB inhibition.

Anticancer activity of metformin: a systematic review of the literature

Background

The anticancer activity of metformin has been confirmed against several cancer types in vitro and in vivo. However, the underlying mechanisms of metformin in the treatment of cancer are not fully understood. This systematic review aims to discuss the possible anticancer mechanism of action of metformin.

Method

A search through different databases was conducted, including Medline and EMBASE.

Results

A total of 96 articles were identified of which 56 were removed for duplication and 24 were excluded after reviewing the title and abstract. A total of 12 research articles were included that describe different antiproliferative mechanisms that may contribute to the antineoplastic effects of metformin.

Conclusion

This analysis discussed the potential anticancer activity of metformin and highlighted the importance of AMPK as a potential target for anticancer therapy.

Metformin Inhibit Lung Cancer Cell Growth and Invasion in Vitro as Well as Tumor Formation in Vivo Partially by Activating PP2A

Background

The aim of this study was to investigate whether PP2A activation is involved in the anti-cancer activity of metformin.

Material/Methods

A549 and H1651 human lung cancer cells were constructed with stable α4 overexpression (O/E α4) or knockdown of PP2A catalytic subunit A/B(sh-PP2Ac). Influences of okadaic acid (OA) treatment, O/E α4 or sh-PP2Ac on metformin treated cells were investigated by cell viability, proliferation, apoptosis, and Transwell invasion assay in vitro. Protein expression levels of Bax, Bcl-2, Myc, and Akt as well as serine phosphorylation level of Bax, Myc, and Akt were examined by western blot. For in vivo assays, wild type (WT) or modified A549 cells were subcutaneously injected in nude mice, and metformin treatment on these xenografted tumors were assayed by tumor formation assay and western blot detecting cell proliferation marker PCNA (proliferating cell nuclear antigen) as well as protein expression level and serine phosphorylation level of Akt and Myc.

Results

Metformin treatment significantly reduced A549 or H1651 cell growth and invasive capacity in vitro as well as Ser184 phosphorylation of Bax, Ser62 phosphorylation of Myc, and Ser473 phosphorylation of Akt, all of which could be partially attenuated by OA treatment, O/E α4 or sh-PP2Ac. Metformin treatment also significantly reduced tumor formation in vivo as well as protein expression of PCNA, Akt, Myc, and serine phosphorylation of the latter 2, which can be partially blocked by O/E α4 or sh-PP2Ac.

Conclusions

Metformin reduced lung cancer cell growth and invasion in vitro as well as tumor formation in vivo partially by activating PP2A.

The benefits of adding metformin to tamoxifen to protect the endometrium-A randomized placebo-controlled trial

BACKGROUND

We investigated whether metformin prevents tamoxifen-induced endometrial changes and insulin resistance (IR) after a diagnosis of breast cancer.

METHODS

This was a single-centre, randomized, double-blind, placebo-controlled, parallel group trial. Postmenopausal women with hormone receptor-positive breast cancer taking tamoxifen were randomly allocated to metformin 850 mg or identical placebo, twice daily, for 52 weeks. Outcome measures included double endometrial thickness (ET) measured by transvaginal ultrasound, fasting insulin, glucose and IR estimated by the homeostasis model of assessment (HOMA-IR).

RESULTS

A total of 112 women were screened and 102 randomized. Results are presented as median (range). The 101 women who took at least one dose of medication were aged 56 (43-72) years, with 5(0.5-28) years postmenopause, and had taken tamoxifen for 28.9 (0-367.4) weeks. The baseline ET was 2.9 mm (1.4-21.9) for the placebo group (n = 52) and 2.5 mm (1.3-14.8) for the metformin group (n = 50). At 52 weeks, the median ET was statistically significantly lower for the metformin (n = 36) than for the placebo group (n = 45) (2.3 mm (1.4-7.8) vs 3.0 (1.2-11.3); P = 0.05). 13.3% allocated to placebo had an ET greater than 4 mm vs 5.7% for metformin (P = 0.26). There was no endometrial atypia or cancer. Compared with placebo, metformin resulted in significantly greater baseline-adjusted reductions in weight (P < 0.001), waist circumference (0.03) and HOMA-IR (P < 0.001).

CONCLUSIONS

Metformin appears to inhibit tamoxifen-induced endometrial changes and has favourable metabolic effects. Further research into the adjuvant use of metformin after breast cancer and to prevent EH and cancer is warranted.