The antidiabetic drug metformin acts on the bone microenvironment to promote myeloma cell adhesion to preosteoblasts and increase myeloma tumour burden in vivo

Repurposing Metformin in hematologic tumor: State of art

Metformin is an ancient drug for the treatment of type 2 diabetes, and many studies now suggested that metformin can be used as an adjuvant drug in the treatment of many types of tumors. The mechanism of action of metformin for tumor treatment mainly involves: 1. activation of AMPK signaling pathway 2. inhibition of DNA damage repair in tumor cells 3. downregulation of IGF-1 expression 4. inhibition of chemoresistance and enhancement of chemotherapy sensitivity in tumor cells 5. enhancement of antitumor immunity 6. inhibition of oxidative phosphorylation (OXPHOS). Metformin also plays an important role in the treatment of hematologic tumors, especially in leukemia, lymphoma, and multiple myeloma (MM). The combination of metformin and chemotherapy enhances the efficacy of chemotherapy, and metformin reduces the progression of monoclonal gammopathy of undetermined significance (MGUS) to MM. The purpose of this review is to summarize the anticancer mechanism of metformin and the role and mechanism of action of metformin in hematologic tumors. We mainly summarize the studies related to metformin in hematologic tumors, including cellular experiments and animal experiments, as well as controlled clinical studies and clinical trials. In addition, we also focus on the possible side effects of metformin. Although a large number of preclinical and clinical studies have been performed and the role of metformin in preventing the progression of MGUS to MM has been demonstrated, metformin has not been approved for the treatment of hematologic tumors, which is related to the adverse effects of its high-dose application. Low-dose metformin reduces adverse effects and has been shown to alter the tumor microenvironment and enhance antitumor immune response, which is one of the main directions for future research.

Action Mechanism of Metformin and Its Application in Hematological Malignancy Treatments: A Review

Hematologic malignancies (HMs) mainly include acute and chronic leukemia, lymphoma, myeloma and other heterogeneous tumors that seriously threaten human life and health. The common effective treatments are radiotherapy, chemotherapy and hematopoietic stem cell transplantation (HSCT), which have limited options and are prone to tumor recurrence and (or) drug resistance. Metformin is the first-line drug for the treatment of type 2 diabetes (T2DM). Recently, studies identified the potential anti-cancer ability of metformin in both T2DM patients and patients that are non-diabetic. The latest epidemiological and preclinical studies suggested a potential benefit of metformin in the prevention and treatment of patients with HM. The mechanism may involve the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway by metformin as well as other AMPK-independent pathways to exert anti-cancer properties. In addition, combining current conventional anti-cancer drugs with metformin may improve the efficacy and reduce adverse drug reactions. Therefore, metformin can also be used as an adjuvant therapeutic agent for HM. This paper highlights the anti-hyperglycemic effects and potential anti-cancer effects of metformin, and also compiles the in vitro and clinical trials of metformin as an anti-cancer and chemosensitizing agent for the treatment of HM. The need for future research on the use of metformin in the treatment of HM is indicated.

Obesity and myeloma: Clinical and mechanistic contributions to disease progression

Obesity and obesogenic behaviors are positively associated with both monoclonal gammopathy of unknown significance (MGUS) and multiple myeloma (MM). As the only known modifiable risk factor, this association has emerged as a new potential target for MM prevention, but little is known about the mechanistic relationship of body weight with MM progression. Here we summarize epidemiological correlations between weight, body composition, and the various stages of myeloma disease progression and treatments, as well as the current understanding of the molecular contributions of obesity-induced changes in myeloma cell phenotype and signaling. Finally, we outline groundwork for the future characterization of the relationship between body weight patterns, the bone marrow microenvironment, and MM pathogenesis in animal models, which have the potential to impact our understanding of disease pathogenesis and inform MM prevention messages.

The Risk of Multiple Myeloma Is Reduced in Metformin Initiators: A Retrospective Cohort Study in Taiwanese Patients with Type 2 Diabetes Mellitus

BACKGROUND

Whether metformin might reduce the risk of multiple myeloma (MM) has not been extensively researched in humans.

METHODS

The study subjects were enrolled from the reimbursement database of Taiwan's National Health Insurance. A total of 739,553 patients who had a new diagnosis of type 2 diabetes mellitus during 1999-2009 were identified. They were categorized as metformin initiators (metformin (+)) and non-metformin initiators (metformin (-)) based on the prescriptions of antidiabetic drugs that included metformin and did not include metformin within the initial 12 months, respectively. MM incidence was calculated after the initial 12 months of treatment group assignment until 31 December 2011. Hazard ratios based on intention-to-treat (ITT) and per-protocol (PP) approaches were estimated by Cox regression weighted by propensity scores.

RESULTS

In the ITT analyses, the respective incidence rates for 497,248 metformin (+) and 242,305 metformin (-) were 9.97 and 14.33 per 100,000 person-years. The hazard ratio that compared metformin (+) to metformin (-) in the ITT analysis was 0.710 (95% confidence interval 0.593-0.850). In the PP analysis, the respective incidence rates were 5.14 and 13.98 per 100,000 person-years, and the hazard ratio was 0.355 (95% confidence interval, 0.270-0.466). The lower risk of MM among metformin (+) was supported by subgroup and sensitivity analyses.

CONCLUSIONS

Type 2 diabetes patients who are initiated with metformin treatment have a significantly lower risk of MM, especially when they adhere to metformin treatment.

Metformin: Is it a drug for all reasons and diseases?

Metformin was first used to treat type 2 diabetes in the late 1950s and in 2022 remains the first-choice drug used daily by approximately 150 million people. An accumulation of positive pre-clinical and clinical data has stimulated interest in re-purposing metformin to treat a variety of diseases including COVID-19. In polycystic ovary syndrome metformin improves insulin sensitivity. In type 1 diabetes metformin may help reduce the insulin dose. Meta-analysis and data from pre-clinical and clinical studies link metformin to a reduction in the incidence of cancer. Clinical trials, including MILES (Metformin In Longevity Study), and TAME (Targeting Aging with Metformin), have been designed to determine if metformin can offset aging and extend lifespan. Pre-clinical and clinical data suggest that metformin, via suppression of pro-inflammatory pathways, protection of mitochondria and vascular function, and direct actions on neuronal stem cells, may protect against neurodegenerative diseases. Metformin has also been studied for its anti-bacterial, -viral, -malaria efficacy. Collectively, these data raise the question: Is metformin a drug for all diseases? It remains unclear as to whether all of these putative beneficial effects are secondary to its actions as an anti-hyperglycemic and insulin-sensitizing drug, or result from other cellular actions, including inhibition of mTOR (mammalian target for rapamycin), or direct anti-viral actions. Clarification is also sought as to whether data from ex vivo studies based on the use of high concentrations of metformin can be translated into clinical benefits, or whether they reflect a 'Paracelsus' effect. The environmental impact of metformin, a drug with no known metabolites, is another emerging issue that has been linked to endocrine disruption in fish, and extensive use in T2D has also raised concerns over effects on human reproduction. The objectives for this review are to: 1) evaluate the putative mechanism(s) of action of metformin; 2) analyze the controversial evidence for metformin's effectiveness in the treatment of diseases other than type 2 diabetes; 3) assess the reproducibility of the data, and finally 4) reach an informed conclusion as to whether metformin is a drug for all diseases and reasons. We conclude that the primary clinical benefits of metformin result from its insulin-sensitizing and antihyperglycaemic effects that secondarily contribute to a reduced risk of a number of diseases and thereby enhancing healthspan. However, benefits like improving vascular endothelial function that are independent of effects on glucose homeostasis add to metformin's therapeutic actions.