The molecular mechanisms underlying the antineoplastic properties of metformin, a first-line drug for type 2 diabetes, remain elusive. Here we report that metformin induces genome-wide alterations in DNA methylation by modulating the activity of S-adenosylhomocysteine hydrolase (SAHH). Exposing cancer cells to metformin leads to hypermethylation of tumor-promoting pathway genes and concomitant inhibition of cell proliferation. Metformin acts by upregulating microRNA let-7 through AMPK activation, leading to degradation of H19 long noncoding RNA, which normally binds to and inactivates SAHH. H19 knockdown activates SAHH, enabling DNA methyltransferase 3B to methylate a subset of genes. This metformin-induced H19 repression and alteration of gene methylation are recapitulated in endometrial cancer tissue samples obtained from patients treated with antidiabetic doses of metformin. Our findings unveil a novel mechanism of action for the drug metformin with implications for the molecular basis of epigenetic dysregulation in cancer. This novel mechanism of action also may be occurring in normal cells.

Only a subset of cervical precursor lesions progress to cervical cancer and because of the lack of the predictive markers, it cannot be ascertained which lesions will progress or not. To estimate the risk of disease progression associated with human papillomavirus (HPV) genotypes, we followed 570 Japanese women with cytological LSIL (low-grade squamous intraepithelial lesion) and histological CIN (cervical intraepithelial neoplasia) grade 1-2 lesions (479 CIN 1; 91 CIN 2) at 3 to 4 month intervals for a mean follow-up period of 39.1 months. At entry, we detected HPV DNA in cervical samples by polymerase chain reaction-based methodology. Over the period of follow-up period, 46 lesions progressed to CIN 3 while 362 regressed to normal cytology. Women with multiple HPV infections were more likely to have persistent lesions (hazard ratio [HR] for regression, 0.65; 95% confidence interval [CI], 0.42-1.02; p 5 0.07); however, multiple infections did not increase the risk of progression (HR for progression, 1.04; 95% CI, 0.37-2.94; p 5 0.94). After adjusting for CIN grade and women's age, HRs for progression to CIN 3 (vs. women with low-risk types or negative for HPV DNA) varied markedly by HPV genotype: type 16 (11.1, 95% CI: 1.39-88.3); 18 (14.1, 0.65-306); 31 (24.7, 2.51-243); 33 (20.3, 1.78-231); 35 (13.7, 0.75-251); 52 (11.6, 1.45-93.3); 58 (8.85, 1.01-77.6); other high-risk types (4.04, 0.47-34.7). HPV 45 was not detected in our study subjects. The cumulative probability of CIN 3 within 5 years was 20.5% for HPV 16, 18, 31, 33, 35, 52 and 58; 6.0% for other high-risk types; 1.7% for low-risk types (p 5 0.0001). In conclusion, type-specific HPV testing for women with LSIL/CIN 1-2 lesions is useful for identifying populations at increased or decreased risk of disease progression.Cervical cancer remains the second most common cancer in women worldwide, with nearly 500,000 women developing the disease every year.1 The marked decline in incidence rates of cervical cancer in developed countries is attributed to the development of cytology screening programs that detect women with precursor lesions. However, cancer prevention eventually requires the eradication of such precursor lesions. Vaccination against human papillomavirus (HPV) types 16 and 18 prevents new infection; however, it has no therapeutic effect on women with abnormal Pap results. 2Most low-grade cervical lesions are known to regress spontaneously, whereas only a small fraction progress to cervical cancer.3-7 However, we cannot predict which lesions will regress or progress. Recommendations by the American Society for Colposcopy and Cervical Pathology (ASCCP) suggest that women with cervical intraepithelial neoplasia grade 2 (CIN 2) should be treated. 8 However, there is risk of overtreatment, as 40-60% of CIN 2 lesions spontaneously regress

BACKGROUND: Metformin, an antidiabetic drug, decreases the incidence of various cancers in diabetic patients. Metformininduced inhibition of cancer cell proliferation has been confirmed in vitro but not in humans. Because endometrial cancer is associated with insulin resistance, the authors investigated whether a diabetes-therapeutic metformin dose inhibits cancer cell growth in patients with endometrial cancer. METHODS: A dose of metaformin was administered (1500-2250 mg/day) to 31 patients with endometrial cancer preoperatively for 4 to 6 weeks. Cell proliferation was assessed in patient tissues using immunohistochemical and Western blot analyses and DNA synthesis was measured in serum using a thymidine uptake assay. All statistical tests were 2-sided. P values of < .05 were considered statistically significant. RESULTS: Preoperative metformin treatment decreased DNA synthesis in sera and significantly reduced the Ki-67 (mean proportional decrease, 44.2%; 95% confidence interval [95% CI], 35.4-53.0 [P <.001]) and topoisomerase IIa (mean proportional decrease, 36.4%; 95% CI, 26.7-46.0 [P <.001]) labeling indices. Levels of phospho-ribosomal protein S6 and phospho-extracellular signal-regulated kinase 1/2 (ERK1/2) were found to be significantly decreased and phospho-adenosine monophosphate-activated protein kinase and p27 levels were significantly increased. Preoperative metformin use caused significant decreases in circulating factors, including insulin, glucose, insulin-like growth factor 1, and leptin. DNA synthesis-stimulating activity in patient sera was significantly decreased during metformin administration. CONCLUSIONS: An antidiabetic dose of metformin inhibited endometrial cancer cell growth in vivo, an effect likely due to its effect on humoral factor(s). This translational study provides considerable rationale to initiate large clinical trials. Cancer 2014;120:2986-95. V C 2014 American Cancer Society.KEYWORDS: metformin, endometrial cancer, insulin resistance, growth inhibition, in vivo. INTRODUCTIONMetformin, an oral biguanide antihyperglycemic drug, is widely prescribed as first-line therapy against type 2 diabetes mellitus. Metformin suppresses hepatic gluconeogenesis and increases glucose uptake by peripheral tissues, thereby decreasing plasma glucose levels and eventually decreasing plasma insulin levels. 1 Widespread metformin use over the past decade has inspired several population studies that have identified additional benefits of metformin, including a metformin-induced decrease in cancer incidence and cancer-related mortality in patients with diabetes. 2,3 This applies to cancers of the breast, colon, lung, prostate, pancreas, ovary, and liver. In addition to cancer prevention, more recent studies have indicated that metformin also possesses antineoplastic properties, 4-9 such as improving response rates to neoadjuvant chemotherapy in patients with breast cancer. 10 These epidemiologic findings suggest that metformin is a promising drug for both cancer prevention and treatment and have fa...

Our recent studies of microRNA (miRNA) expression signatures indicated that microRNA-29a (miR-29a) was significantly downregulated in several types of human cancers, suggesting that miR-29a may be a putative tumor-suppressive miRNA in human cancers. The aim of this study was to investigate the functional significance of miR-29a in cervical squamous cell carcinoma (SCC) and to identify novel miR-29a-regulated cancer pathways and target genes involved in cervical SCC oncogenesis and metastasis. Restoration of miR-29a in cervical cancer cell lines (CaSKi, HeLa, ME180 and Yumoto) revealed that this miRNA significantly inhibited cancer cell migration and invasion. Gene expression data and in silico analysis demonstrated that heat-shock protein 47 (HSP47), a member of the serpin superfamily of serine proteinase inhibitors and a molecular chaperone involved in the maturation of collagen molecules, was a potential target of miR-29a regulation. Luciferase reporter assays showed that miR-29a directly regulated HSP47. Moreover, silencing of the HSP47 gene significantly inhibited cell migration and invasion in cancer cells and the expression of HSP47 was upregulated in cancer tissues and cervical intraepithelial neoplasia (CIN), as demonstrated by immunostaining. Downregulation of miR-29a was a frequent event in cervical SCC and miR-29a acted as a tumor suppressor by directly targeting HSP47. Recognition of tumor-suppressive miRNA-regulated molecular targets provides new insights into the potential mechanisms of cervical SCC oncogenesis and metastasis and suggests novel therapeutic strategies for treatment of this disease.

ObjectiveThe present study investigated long-term outcomes of medroxyprogesterone acetate (MPA) plus metformin therapy in terms of control of atypical endometrial hyperplasia (AEH) and endometrial cancer (EC), and post-treatment conception.MethodsWe retrospectively analyzed 63 patients (42 with EC; 21 with AEH) who underwent fertility-sparing management using MPA plus metformin. MPA (400 mg/day) and metformin (750–2,250 mg/day) were administered to achieve complete response (CR). Metformin was administered until conception, even after MPA discontinuation.ResultsOf the total patients, 48 (76%) had a body mass index (BMI) ≥25 kg/m2 and 43 (68%) showed insulin resistance. Sixty-one patients (97%) achieved CR within 18 months. CR rates at 6, 8–9, and 12 months were 60%, 84%, and 90%, respectively. During a median follow-up period of 57 months (range, 13–115 months), relapse occurred in 8 of 61 patients (13.1%) who had achieved CR. Relapse-free survival (RFS) in all patients at 5 years was 84.8%. Upon univariate analysis, patients with BMI ≥25 kg/m2 had significantly better prognoses than did those with BMI <25 kg/m2 (odds ratio=0.19; 95% confidence interval=0.05–0.66; p=0.009). Overall pregnancy and live birth rates per patient were 61% (19/31) and 45% (14/31), respectively.ConclusionsMPA plus metformin is efficacious in terms of RFS and post treatment conception. Moreover, metformin may be more efficacious for patients with BMI ≥25 kg/m2.