Can a Diabetes Drug Prevent Cancer Death?
By James Saftig
With its near-perfect safety record, low cost, and favorable side-effect profile, the anti-diabetic drug metformin is one of the few FDA-approved drugs Life Extension® recommends its members should take every day.
Between 1990 and 2011 alone,1 over 1,000 published studies have yielded confirmatory data on its numerous anti-aging properties, from weight loss and glucose control to cardiovascular disease and cancer defense.
As the medical establishment continues to ignore this mounting body of evidence, ongoing research powerfully validates our position.
In one of the largest studies of its kind, a team of scientists analyzed cancer risk among 8,000 diabetics treated with metformin.2 Over a 10-year period, they observed a 54% lower incidence of all cancers compared to the general population.
Metformin not only exerted a major protective effect against cancer development, but those who developed cancer exhibited a significantly higher survival rate, including those with malignant cancers of the lung, colon, and breast. Of equal significance was the finding that the earlier the metformin regimen was initiated, the greater the preventive benefit.
Given that diabetics are predisposed to a horrifically wide array of cancers—of the breast, colon, liver, pancreas, kidney, endometrium (uterine lining), among others3-5—these results have profound implications for all maturing individuals.
In this article, the most recent data supporting metformin’s anti-cancer mechanisms are detailed. You will learn of its specific mechanisms of action, which shed further light on the link between obesity, diabetes, and cancer initiation. You will also discover how metformin induces cancer cell death at their earliest stages of development via metabolic pathways that also promote weight loss and optimal glucose control.
Metformin Slashes Cancer Risk in Multiple Clinical Trials
The study cited in the introduction of this article (54% lower risk of cancer) was of such medical importance as to merit an accompanying editorial by noted cancer epidemiologist Bruce B. Duncan, MD, PhD.6 Duncan observed that this was the most compelling amongst a rapidly growing set of studies, all suggesting that metformin might induce profound effects in preventing a wide range of cancers while improving prognosis in people who do develop malignancies.6
Additional supportive studies validate these findings.6 In a cohort study of more than 12,000 patients, metformin users died of cancer 30% less often than those taking another category of drug called sulfonylureas (including DiaBeta® and Glucotrol®).6,7 Of equal and even greater significance, people taking insulin had a 90% greater death rate than the metformin users in that study.6
In a second study of different design, people taking metformin for diabetes control for more than 36 months had a 72% lower risk of developing cancer than those on other regimens.6,8 Similarly, in a third study, metformin users had a 62% lower risk of developing cancer, compared with those who had never used metformin.6,9 Of significance, that study also showed an increased risk of cancer in people who were taking insulin or oral antidiabetes drugs other than metformin.
There’s additional evidence that metformin not only prevents cancer from developing, but also helps to improve the prognosis in patients who do develop tumors. In one study of breast cancer patients on chemotherapy, 24% of those who were also taking metformin had a complete response rate, compared with just 8% for those not taking it.6,10 As a result of these "incidental" findings, scientists have initiated several clinical trials to examine the impact of metformin as formal additional treatment for breast and other cancers.6,11
Numerous recent studies further support a close association between metformin use and substantially reduced cancer incidence, along with improved survival.12-16
These observations raise the question, "Why should a diabetes drug protect against cancer?"6
The answer is both simple and surprising.
Diabesity and Cancer Initiation: How Metformin Works
Years of clinical analysis have confirmed the link between obesity and diabetes, conditions whose co-occurrence has given rise to the term diabesity.
Diabesity is a direct causative factor in the development of a wide range of cancers. Diabetics have as much as a 41% increased risk for virtually all cancer types compared to healthy people. Elevated blood sugar alone increases the risk of certain cancers, including those of the kidney, pancreas, and skin (melanoma).6,17,18
Obesity increases cancer risk for more than a dozen different cancers.6 A 59% increase in cancer risk has been documented for every 5-unit increase in body mass index (BMI) alone.6,19 Studies show that obesity is responsible for up to 20% of cancer deaths in women.20
The link between diabesity and cancer points to the underlying mechanisms of action by which metformin works as a cancer-preventing agent.
Metformin operates at the molecular level by activating adenosine monophosphate-activated protein kinase or AMPK, a molecule essential to life. AMPK or its molecular analogs are present in virtually all living organisms.6,21 It also happens to be intimately involved in cellular processes whose dysregulation play a central role in both diabesity and cancer initiation.
Diabetes and obesity result from various metabolic derangements. Cancer results from disordered regulation of cell growth. AMPK is critical to normal regulation of both metabolism and cell growth, as a result of millions of years of evolutionary development.6
As a fuel-sensor and metabolic master switch, AMPK recognizes and responds to changes in cellular energy levels, determining how fats and carbohydrates will be used in storing or utilizing energy.6 In metabolic terms, AMPK tells cells to conserve and generate new energy stores. In so doing, it lowers sugar output from the liver, increases glucose uptake from the blood, maintains insulin sensitivity, and ultimately lowers blood sugar.6,21
AMPK exerts similar effects in terms of regulating cell growth and replication, instructing cells to conserve energy, slowing and often shutting down aberrant cell growth entirely. In essence, when AMPK is activated, incipient cancer cells starve themselves to death for lack of adequate energy supplies.22
We can naturally activate AMPK in our bodies through several time-honored mechanisms. Calorie restriction lowers cellular energy stores and activates AMPK.23 Known to increase life span in virtually all species, calorie restriction has been shown to reduce cancer incidence and death in primate studies.24,25 And a recent study showed that gastric bypass surgery not only produced sustained weight loss, but also reduced cancer incidence by 42% in women patients (no effect was seen in men).6,26
Exercise is another strong natural activator of AMPK, and studies show that people with the highest levels of physical activity are protected against cancers of the lung and colon by as much as 30%.6,27,28
Exercise and weight loss are lifestyle changes that most of us need to make, while bariatric surgery and massive calorie restriction have more limited appeal and application as means of activating AMPK and lowering cancer risk.
Metformin, a natural product of the French lilac,29 is a safe, readily available, and inexpensive way to activate AMPK and starve cancer cells of their energy supplies.6,30,31 In doing so, metformin powerfully restores healthy regulation—both of metabolic factors and of those that regulate cell growth.
Let’s now examine how metformin halts incipient cancers by quelling abnormal cellular proliferation, one of the earliest steps in cancer development.
Metformin Combats Diabesity and Cancer
The anti-diabetic drug metformin was recently shown to slash risk of all cancers by 54% among 8,000 diabetics over a 10-year period.
Prognosis among those under study who developed cancer was also significantly improved, including cancers of the lung, colon, and breast.
Supportive epidemiological studies reveal that people taking metformin for glucose control have markedly reduced rates of cancer, despite the higher cancer risks imposed by diabetes and obesity.
Detailed molecular analyses are elucidating the mechanisms by which metformin prevents cancer.
Metformin works through a common mechanism to lower blood glucose and to reduce cancer risk, shedding new light on the intimate relationship between diabetes, obesity, and cancer.
Laboratory and clinical data now strongly suggest that metformin can prevent cancers of the colon, lung, and breast, even in non-diabetic individuals.
If you are concerned about lowering your cancer risk and improving your metabolic profile, ask your doctor about starting a metformin regimen at a dose of 250-500 mg twice a day.
Metformin’s Anti-Cancer Power Confirmed in Lab Studies
Healthy, normal people develop incipient cancer cells in their bodies daily; these cells are normally destroyed by a number of natural processes. When those processes break down, the cancer cells are free to proliferate and form a tumor. An ideal anti-cancer drug, then, would eliminate these altered, "precancerous" cells before they could replicate and become invasive and malignant.32
Even in their earliest stages, aggressive cancer cells are notoriously energy-hungry, burning calories at a frenetic rate as they grow out of control.33 For that reason, targeting cancer cell metabolism now stands at the forefront of cancer prevention research.34 With its potent ability to shut off the cellular energy pipeline by activating AMPK, metformin is showing its value in preventing or slowing a host of cancer types in laboratory studies.
The consequences of AMPK activation by metformin are numerous. Metformin, added to cultures of many different cancer cell types, blocks proliferation by "stalling" cells at one of several phases of the cell replication cycle, preventing them from reproducing.34-37 Metformin’s ability to starve cancer cells of energy also enhances the rate of cell death by the process known as apoptosis, one of the body’s natural means of cancer control.34,38
Perhaps the most detailed picture of metformin’s antiproliferative actions comes from a 2011 study in France.38 Researchers there added metformin to melanoma skin cancer cells in culture, and monitored the effects. At 24 hours, metformin had starved the cancer cells to the point that their replicative cell cycle was arrested. By 72 hours, the cells underwent autophagy, a mechanism whereby starving cells literally "eat themselves" in a desperate attempt to survive. And by 96 hours, the cancer cells began dying off en masse by apoptosis.
Several additional antiproliferative mechanisms have recently been demonstrated for metformin in addition to its effects on the AMPK energy-sensing pathway.35,39-42 That ability to act by multiple mechanisms is called pleiotropy. It is powerfully beneficial because it prevents development of resistance to any one pathway. Pleiotropy is seen much more commonly with natural products such as metformin than with mono-targeted pharmaceutical drugs.
The combined effect of all of metformin’s pleiotropic mechanisms is a marked reduction of tumor growth in lab animals implanted with human cancer cells.36,43 To date, metformin-induced antiproliferative effects have been demonstrated in cancers of the brain, lung, breast, ovary, prostate, and colon.35-38,44-47 And human studies are now showing important reductions in various tumor markers when metformin is provided to breast cancer patients prior to tumor surgery.48 Importantly, in breast cancer cells, metformin is most active against cancer strains that are resistant to standard chemotherapy drugs.46
Using metformin may increase the risk of lactic acidosis, a rare but potentially fatal buildup of lactic acid in the blood. Since congestive heart failure, kidney impairment, and liver problems increase the risk of lactic acidosis, individuals with these conditions are advised against using metformin. Individuals with type 1 diabetes should not take the drug. People who have recently suffered a heart attack or stroke and those who have recently undergone surgery or are severely dehydrated are more vulnerable to lactic acidosis.63-65 Consult with your doctor if any of these conditions applies to you or if you are pregnant, planning to become pregnant, or breastfeeding.
Lactic acidosis is a medical emergency. Its symptoms include muscle pain, difficulty breathing, sleepiness, feeling extremely weak or tired, and abdominal pain with nausea, vomiting, or diarrhea.63-65 If you believe you are suffering from lactic acidosis, seek medical attention immediately.
Metformin Prevents Cancers in Non-Diabetic Individuals
Perhaps the most exciting news to come out of the recent surge in interest in metformin is that the drug can prevent cancers from forming in animals and humans who are not diabetic. As a "mimicker" of a calorie-restricted state, that might be expected of metformin, given that calorie restriction is such a potent cancer-preventive strategy.33,49-51
Since 2008, a small explosion of studies has appeared demonstrating how effective metformin can be in this context, ultimately suggesting that it should be taken regularly by anyone who wants to reduce their risk of dying from cancer.
Research now demonstrates that metformin, provided orally to lab animals, prevents deadly colorectal cancers52 (the second leading cause of cancer deaths in the US, and an astonishingly preventable disease).53 Metformin suppresses intestinal polyp growth, a precursor of colorectal cancer, in mice predisposed to that disease.54 And, in a study of chemically induced colon cancer, metformin significantly reduced formation of so-called "aberrant crypt foci," which in humans represent an early stage in cancer development.55
Those studies led to the first human study of metformin as a cancer preventive agent in non-diabetic people. Researchers studied 26 non-diabetic people with aberrant crypt foci that had been found on routine colonoscopy.56 They randomly assigned them to receive metformin 250 mg per day, or no treatment, and then performed repeat colonoscopy one month later. The metformin group had a significant decrease in the number of aberrant crypt foci, from nearly 9 per patient down to about 5 per patient, while control patients had no change. This represent a 55% reduction in this cancer precursor in patients taking low-dose metformin.
Chemoprevention studies now also demonstrate similar effects in other cancers. Mice supplemented with oral metformin, exposed to a potent tobacco carcinogen, developed 53% fewer lung cancers than did control animals.57 And when metformin was administered by injection, that protection rate rose to 72%.
Breast cancer prevention would represent a huge forward stride in extending human life span and reducing suffering. There’s encouraging data here as well. Mice given metformin in their drinking water for 13 days prior to injection with a powerful breast carcinogen had significantly delayed onset of tumor development.58 Several other studies have demonstrated that metformin-supplemented mice experience a reduction in proliferation of cancer-prone breast cells and inhibition of tumor growth.31
There is now a tremendous body of literature showing that metformin prevents cancer cells from proliferating, and moreover it prevents clinically relevant human cancers from developing, even in non-diabetic, non-obese individuals.59 As a result, one might expect to see large clinical trials of metformin in healthy older adults as a cancer chemopreventive agent.
Sadly, even though calls for such studies are gathering strength, to date no trial has been designed, let alone implemented.60-62 Given metformin’s impressive safety record over nearly 50 years of clinical use,43 there is simply no reason for sensible people to wait for an "official" medical establishment recommendation. People who are concerned about their growing risk of cancer should simply speak to their physicians now, and present them with a synopsis of the data, so that they can begin potentially lifesaving use of metformin today.
The anti-diabetic drug metformin was recently shown to slash risk of all cancers by 54% among 8,000 diabetics over a 10-year period while significantly improving prognosis among those who developed cancer, including cancers of the lung, colon, and breast.
Diabetes and obesity are twin risks for cancer development. Metformin offers powerful protection against cancer in those populations. Aggressive scientific research is revealing that metformin’s action, activating the cellular energy sensor AMPK, is the key to both its metabolic benefits and its cancer chemopreventive capabilities.
Both human and animal studies definitively confirm that metformin lowers cancer risk dramatically while also preventing new cancer formation, in both diabetic and non-diabetic individuals. Metformin’s 50-year safety record, coupled with its low cost and favorable side effect profile, provide an ironclad rationale for most aging humans to consider taking metformin.
If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at 1-866-864-3027.
1. Andújar-Plata P, Pi-Sunyer X, Laferrère B. Metformin effects revisited. Diabetes Res Clin Pract. 2011 Oct 13.
2. Libby G, Donnelly LA, Donnan PT, Alessi DR, Morris AD, Evans JM. New users of metformin are at low risk of incident cancer: a cohort study among people with type 2 diabetes. Diabetes Care. 2009 Sep;32(9):1620-5.
3. Czyzyk A, Szczepanik Z. Diabetes mellitus and cancer. Eur J Intern Med. 2000 Oct;11(5):245-52.
4. Vigneri P, Frasca F, Sciacca L, Pandini G, Vigneri R. Diabetes and cancer. Endocr Relat Cancer. 2009 Dec;16(4):1103-23.
5. Martin-Castillo B, Vazquez-Martin A, Oliveras-Ferraros C, Menendez JA. Metformin and cancer: Doses, mechanisms and the dandelion and hormetic phenomena. Cell Cycle. 2010 Mar 21;9(6):1057-64.
6. Duncan BB, Schmidt MI. Metformin, cancer, alphabet soup, and the role of epidemiology in etiologic research. Diabetes Care. 2009 Sep;32(9):1748-50.
7. Bowker SL, Majumdar SR, Veugelers P, Johnson JA. Increased cancer-related mortality for patients with type 2 diabetes who use sulfonylureas or insulin. Diabetes Care. 2006 Feb;29(2):254-8.
8. Monami M, Lamanna C, Balzi D, Marchionni N, Mannucci E. Sulphonylureas and cancer: a case-control study. Acta Diabetol. 2009 Dec;46(4):279-84.
9. Li D, Yeung SC, Hassan MM, Konopleva M, Abbruzzese JL. Antidiabetic therapies affect risk of pancreatic cancer. Gastroenterology. 2009 Aug;137(2):482-8.
10. Jiralerspong S, Palla SL, Giordano SH, et al. Metformin and pathologic complete responses to neoadjuvant chemotherapy in diabetic patients with breast cancer. J Clin Oncol. 2009 Jul 10;27(20):3297-302.
11. Goodwin PJ, Ligibel JA, Stambolic V. Metformin in breast cancer: time for action. J Clin Oncol. 2009 Jul 10;27(20):3271-3.
12. Currie CJ, Poole CD, Gale EA. The influence of glucose-lowering therapies on cancer risk in type 2 diabetes. Diabetologia. 2009 Sep;52(9):1766-77.
13. Landman GW, Kleefstra N, van Hateren KJ, Groenier KH, Gans RO, Bilo HJ. Metformin associated with lower cancer mortality in type 2 diabetes: ZODIAC-16. Diabetes Care. 2010 Feb;33(2):322-6.
14. Chen TM, Lin CC, Huang PT, Wen CF. Metformin associated with lower mortality in diabetic patients with early stage hepatocellular carcinoma after radiofrequency ablation. J Gastroenterol Hepatol. 2011 May;26(5):858-65.
15. Lee MS, Hsu CC, Wahlqvist ML, Tsai HN, Chang YH, Huang YC. Type 2 diabetes increases and metformin reduces total, colorectal, liver and pancreatic cancer incidences in Taiwanese: a representative population prospective cohort study of 800,000 individuals. BMC Cancer. 2011;11:20.
16. Monami M, Colombi C, Balzi D, et al. Metformin and cancer occurrence in insulin-treated type 2 diabetic patients. Diabetes Care. 2011 Jan;34(1):129-31.
17. Becker S, Dossus L, Kaaks R. Obesity related hyperinsulinaemia and hyperglycaemia and cancer development. Arch Physiol Biochem. 2009 May;115(2):86-96.
18. Barone BB, Yeh HC, Snyder CF, et al. Long-term all-cause mortality in cancer patients with preexisting diabetes mellitus: a systematic review and meta-analysis. JAMA. 2008 Dec 17;300(23):2754-64.
19. Renehan AG, Tyson M, Egger M, Heller RF, Zwahlen M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. Lancet. 2008 Feb 16;371(9612):569-78.
20. Ibarra-Drendall C, Dietze EC, Seewaldt VL. Metabolic syndrome and breast cancer risk: is there a role for metformin? Curr Breast Cancer Rep. 2011 Sep;3(3):142-50.
21. Hardie DG. Role of AMP-activated protein kinase in the metabolic syndrome and in heart disease. FEBS Lett. 2008 Jan 9;582(1):81-9.
22. Jalving M, Gietema JA, Lefrandt JD, et al. Metformin: taking away the candy for cancer? Eur J Cancer. 2010 Sep;46(13):2369-80.
23. Canto C, Auwerx J. Calorie restriction: is AMPK a key sensor and effector? Physiology (Bethesda). 2011 Aug;26(4):214-24.
24. Omodei D, Fontana L. Calorie restriction and prevention of age-associated chronic disease. FEBS Lett. 2011 Jun 6;585(11):1537-42.
25. Thompson HJ, Zhu Z, Jiang W. Dietary energy restriction in breast cancer prevention. J Mammary Gland Biol Neoplasia. 2003 Jan;8(1):133-42.
26. Sjostrom L, Gummesson A, Sjostrom CD, et al. Effects of bariatric surgery on cancer incidence in obese patients in Sweden (Swedish Obese Subjects Study): a prospective, controlled intervention trial. Lancet Oncol. 2009 Jul;10(7):653-62.
27. Tardon A, Lee WJ, Delgado-Rodriguez M, et al. Leisure-time physical activity and lung cancer: a meta-analysis. Cancer Causes Control. 2005 May;16(4):389-97.
28. Samad AK, Taylor RS, Marshall T, Chapman MA. A meta-analysis of the association of physical activity with reduced risk of colorectal cancer. Colorectal Dis. 2005 May;7(3):204-13.
29. Graham GG, Punt J, Arora M, et al. Clinical pharmacokinetics of metformin. Clin Pharmacokinet. 2011 Feb 1;50(2):81-98.
30. Zhu Z, Jiang W, Thompson MD, McGinley JN, Thompson HJ. Metformin as an energy restriction mimetic agent for breast cancer prevention. J Carcinog. 2011;10:17.
31. Cazzaniga M, Bonanni B, Guerrieri-Gonzaga A, Decensi A. Is it time to test metformin in breast cancer clinical trials? Cancer Epidemiol Biomarkers Prev. 2009 Mar;18(3):701-5.
32. Vazquez-Martin A, Lopez-Bonetc E, Cufi S, et al. Repositioning chloroquine and metformin to eliminate cancer stem cell traits in pre-malignant lesions. Drug Resist Updat. 2011 Aug-Oct;14(4-5):212-23.
33. Brunet J, Vazquez-Martin A, Colomer R, Grana-Suarez B, Martin-Castillo B, Menendez JA. BRCA1 and acetyl-CoA carboxylase: the metabolic syndrome of breast cancer. Mol Carcinog. 2008 Feb;47(2):157-63.
34. Ben Sahra I, Laurent K, Giuliano S, et al. Targeting cancer cell metabolism: the combination of metformin and 2-deoxyglucose induces p53-dependent apoptosis in prostate cancer cells. Cancer Res. 2010 Mar 15;70(6):2465-75.
35. Isakovic A, Harhaji L, Stevanovic D, et al. Dual antiglioma action of metformin: cell cycle arrest and mitochondria-dependent apoptosis. Cell Mol Life Sci. 2007 May;64(10):1290-302.
36. Ben Sahra I, Laurent K, Loubat A, et al. The antidiabetic drug metformin exerts an antitumoral effect in vitro and in vivo through a decrease of cyclin D1 level. Oncogene. 2008 Jun 5;27(25):3576-86.
37. Rattan R, Giri S, Hartmann LC, Shridhar V. Metformin attenuates ovarian cancer cell growth in an AMP-kinase dispensable manner. J Cell Mol Med. 2011 Jan;15(1):166-78.
38. Tomic T, Botton T, Cerezo M, et al. Metformin inhibits melanoma development through autophagy and apoptosis mechanisms. Cell Death Dis. 2011;2:e199.
39. Xie Y, Wang YL, Yu L, et al. Metformin promotes progesterone receptor expression via inhibition of mammalian target of rapamycin (mTOR) in endometrial cancer cells. J Steroid Biochem Mol Biol. 2011 Sep;126(3-5):113-20.
40. Ben Sahra I, Regazzetti C, Robert G, et al. Metformin, independent of AMPK, induces mTOR inhibition and cell-cycle arrest through REDD1. Cancer Res. 2011 Jul 1;71(13):4366-72.
41. Micic D, Cvijovic G, Trajkovic V, Duntas LH, Polovina S. Metformin: its emerging role in oncology. Hormones (Athens). 2011 Jan-Mar;10(1):5-15.
42. Beck E, Scheen AJ. Anti-cancer activity of metformin: new perspectives for an old drug. Rev Med Suisse. 2010 Sep 1;6(260):1601-7.
43. Grzybowska M, Bober J, Olszewska M. Metformin - mechanisms of action and use for the treatment of type 2 diabetes mellitus. Postepy Hig Med Dosw (Online). 2011 May 6;65:277-85.
44. Gotlieb WH, Saumet J, Beauchamp MC, et al. In vitro metformin anti-neoplastic activity in epithelial ovarian cancer. Gynecol Oncol. 2008 Aug;110(2):246-50.
45. Zakikhani M, Dowling RJ, Sonenberg N, Pollak MN. The effects of adiponectin and metformin on prostate and colon neoplasia involve activation of AMP-activated protein kinase. Cancer Prev Res (Phila). 2008 Oct;1(5):369-75.
46. Liu B, Fan Z, Edgerton SM, Yang X, Lind SE, Thor AD. Potent anti-proliferative effects of metformin on trastuzumab-resistant breast cancer cells via inhibition of erbB2/IGF-1 receptor interactions. Cell Cycle. 2011 Sep 1;10(17):2959-66.
47. Antonoff MB, D’Cunha J. Teaching an old drug new tricks: metformin as a targeted therapy for lung cancer. Semin Thorac Cardiovasc Surg. 2010 Autumn;22(3):195-6.
48. Hadad S, Iwamoto T, Jordan L, et al. Evidence for biological effects of metformin in operable breast cancer: a pre-operative, window-of-opportunity, randomized trial. Breast Cancer Res Treat. 2011 Aug;128(3):783-94.
49. Longo VD, Fontana L. Calorie restriction and cancer prevention: metabolic and molecular mechanisms. Trends Pharmacol Sci. 2010 Feb;31(2):89-98.
50. Hursting SD, Smith SM, Lashinger LM, Harvey AE, Perkins SN. Calories and carcinogenesis: lessons learned from 30 years of calorie restriction research. Carcinogenesis. 2010 Jan;31(1):83-9.
51. Hursting SD, Lavigne JA, Berrigan D, Perkins SN, Barrett JC. Calorie restriction, aging, and cancer prevention: mechanisms of action and applicability to humans. Annu Rev Med. 2003;54:131-52.
52. Algire C, Amrein L, Zakikhani M, Panasci L, Pollak M. Metformin blocks the stimulative effect of a high-energy diet on colon carcinoma growth in vivo and is associated with reduced expression of fatty acid synthase. Endocr Relat Cancer. 2010 Jun 1;17(2):351-60.
53. No authors listed. Advances in reducing colorectal cancer risk. Colorectal cancer is the third most common cancer in women and the second leading cause of cancer death. These statistics belie how preventable this disease really is. Harv Womens Health Watch. 2003 May;10(9):1-2.
54. Tomimoto A, Endo H, Sugiyama M, et al. Metformin suppresses intestinal polyp growth in ApcMin/+ mice. Cancer Sci. 2008 Nov;99(11):2136-41.
55. Hosono K, Endo H, Takahashi H, et al. Metformin suppresses azoxymethane-induced colorectal aberrant crypt foci by activating AMP-activated protein kinase. Mol Carcinog. 2010 Jul;49(7):662-71.
56. Hosono K, Endo H, Takahashi H, et al. Metformin suppresses colorectal aberrant crypt foci in a short-term clinical trial. Cancer Prev Res (Phila). 2010 Sep;3(9):1077-83.
57. Memmott RM, Mercado JR, Maier CR, Kawabata S, Fox SD, Dennis PA. Metformin prevents tobacco carcinogen--induced lung tumorigenesis. Cancer Prev Res (Phila). 2010 Sep;3(9):1066-76.
58. Bojkova B, Orendas P, Garajova M, et al. Metformin in chemically-induced mammary carcinogenesis in rats. Neoplasma. 2009;56(3):269-74.
59. Li D. Metformin as an antitumor agent in cancer prevention and treatment. J Diabetes. 2011 Feb 21.
60. Pollak M. Metformin and other biguanides in oncology: advancing the research agenda. Cancer Prev Res (Phila). 2010 Sep;3(9):1060-5.
61. Aljada A, Mousa SA. Metformin and neoplasia: Implications and indications. Pharmacol Ther. 2011 Sep 6.
62. Cuzick J, DeCensi A, Arun B, et al. Preventive therapy for breast cancer: a consensus statement. Lancet Oncol. 2011 May;12(5):496-503.
63. Available at: http://www.medsafe.govt.nz/profs/PUarticles/5.htm#Biguanide. Accessed November 11, 2011.
64. Misbin RI. The phantom of lactic acidosis due to metformin in patients with diabetes. Diabetes Care. 2004 Jul;27(7):1791-3.
65. Available at: http://www.rxlist.com/glucophage-drug.htm. Accessed November 11, 2011.
66. Available at: http://www.cancer.org/Cancer/ColonandRectum Cancer/DetailedGuide/colorectal-cancer-key-statistics. Accessed November 29, 2011.
67. Available at: http://www.cancer.gov/cancertopics/wyntk/colon-and-rectal. Accessed November 29, 2011.
68. Zhang ZJ, Zheng ZJ, Kan H, Song Y, Cui W, Zhao G, Kip KE. Reduced risk of colorectal cancer with metformin therapy in patients with type 2 diabetes: a meta-analysis. Diabetes Care. 2011 Oct;34(10):2323-8.
69. Larsson SC, Orsini N, Wolk A. Diabetes mellitus and risk of colorectal cancer: a meta-analysis. J Natl Cancer Inst. 2005 Nov 16;97(22):1679-87.