[New perspectives for metformin in cancer therapy]

Metformin Inducing the Change of Functional and Exhausted Phenotypic Tumor-Infiltrated Lymphocytes and the Correlation with JNK Signal Pathway in Triple-Negative Breast Cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer. Metformin has been shown to have the potential to inhibit the proliferation of malignant cells. This study aimed to investigate the regulatory effect of metformin on phenotypic tumor-infiltrated lymphocytes (TILs) and mechanisms in TNBC.

METHODS

Microarray analysis was performed on 4T1 cells post metformin treatment. BALB/c mice were inoculated with 4T1 cells with knockdown/overexpression of C-Jun N-terminal kinase (JNK), and administered with metformin. Phenotypic TILs in the tumor microenvironment (TME) were visualized by immunofluorescence staining.

RESULTS

Metformin inhibited 4T1 cell proliferation and increased expression of JNK by 21% in vitro. In vivo, Metformin increased cell counts of CD4+ and CD8+TILs by 100% and 85%, respectively, and the increase of TILs was associated with JNK pathway. Cell counts of CD4+/PD-1+ and CD8+/PD-1+TILs were reduced by 64% and 58%, respectively, post metformin treatment, but the reduction of exhausted TILs was not associated with JNK pathway. Metformin induced a 11% and 20% reduction of IL-6 and TNF-α level in the TNBC model.

CONCLUSION

Our study demonstrated that metformin increased the functional phenotype of TILs and associated with JNK pathway, and suppressed the exhausted phenotype of TILs independently to JNK pathway in TNBC microenvironment. Further studies are needed to explore the basic mechanism of action of the drug. Metformin has potentially enhanced efficacy when used in combination with immunotherapy against TNBC.

Metformin Inhibits ROS Production by Human M2 Macrophages via the Activation of AMPK

Metformin (1,1-dimethylbiguanide hydrochloride) is the most commonly used drug to treat type II diabetic patients. It is believed that this drug has several other beneficial effects, such as anti-inflammatory and anticancer effects. Here, we wanted to evaluate the effect of metformin on the production of reactive oxygen species (ROS) by human macrophages. Macrophages are generated in vivo from circulating monocytes depending on the local tissue environment. In vitro proinflammatory macrophages (M1) and anti-inflammatory macrophages (M2) can be generated by culturing monocytes in the presence of different cytokines, such as GM-CSF or M-CSF, respectively. We show that metformin selectively inhibited human monocyte differentiation into proinflammatory macrophages (M1) without inhibiting their differentiation into anti-inflammatory macrophages (M2). Moreover, we demonstrate that, in response to LPS, M2 macrophages produced ROS, which could be very harmful for nearby tissues, and metformin inhibited this process. Interestingly, metformin with LPS induced activation of the adenosine-monophosphate-activated protein kinase (AMPK) and pharmacological activation of AMPK by AICAR, a known AMPK activator, decreased ROS production, whereas the deletion of AMPK in mice dramatically enhanced ROS production in different types of immune cells. These results suggest that metformin exhibits anti-inflammatory effects by inhibiting the differentiation of human monocytes into M1 macrophages and by limiting ROS production by macrophages via the activation of AMPK.

Metformin Inhibits Abdominal Aortic Aneurysm Formation through the Activation of the AMPK/mTOR Signaling Pathway

BACKGROUND AND OBJECTIVE

Epidemiological evidence suggests that the antidiabetic drug metformin (MET) can also inhibit abdominal aortic aneurysm (AAA) formation. However, the underlying protective mechanism remains unknown. It has been reported that phosphorylated AMP-activated protein kinase (AMPK) levels are significantly lower in AAA tissues than control aortic tissues. AMPK activation can inhibit the downstream signaling molecule called mechanistic target of rapamycin (mTOR), which has also been reported be upregulated in thoracic aneurysms. Thus, blocking mTOR signaling could attenuate AAA progression. MET is a known agonist of AMPK. Therefore, in this study, we investigated if MET could inhibit formation of AAA by activating the AMPK/mTOR signaling pathway.

MATERIALS AND METHODS

The AAA animal model was induced by intraluminal porcine pancreatic elastase (PPE) perfusion in male Sprague Dawley rats. The rats were treated with MET or compound C (C.C), which is an AMPK inhibitor. AAA formation was monitored by serial ultrasound. Aortas were collected 4 weeks after surgery and subjected to immunohistochemistry, Western blot, and transmission electron microscopy analyses.

RESULTS

MET treatment dramatically inhibited the formation of AAA 4 weeks after PPE perfusion. MET reduced the aortic diameter, downregulated both macrophage infiltration and matrix metalloproteinase expression, decreased neovascularization, and preserved the contractile phenotype of the aortic vascular smooth muscle cells. Furthermore, we detected an increase in autophagy after MET treatment. All of these effects were reversed by the AMPK inhibitor C.C.

CONCLUSION

This study demonstrated that MET activates AMPK and suppresses AAA formation. Our study provides a novel mechanism for MET and suggests that MET could be potentially used as a therapeutic candidate for preventing AAA.

Combination of metformin with sodium selenite induces a functional phenotypic switch of human GM-CSF monocyte-derived macrophages

OBJECTIVES

We evaluated the effects of metformin (Met, 1,1‑dimethylbiguanide hydrochloride) combined or not with sodium selenite (Ss, Na₂SeO₃) on the functional activities of LPS-activated GM-CSF monocyte-derived macrophages (GM-MDM).

MATERIALS AND METHODS

Human GM-MDMs from three healthy donors were treated with Met or Ss alone, or with the combination of Met and Ss, and assayed for various biological activities and cytokines expression.

RESULTS

Met alone and Ss alone had significantly different effects on phagocytosis and killing capacities and IL-β production, but had similar effects on the downregulation of inducible nitric oxide synthase (iNOS) activity, relative nicotinamide adenine dinucleotide reduced (NADH) dehydrogenase (Complex I), intracellular free calcium ions (_ifCa²⁺), and on the upregulation of arginase activity. Additionally, iNOS activity-to-arginase activity ratio was downregulated in Met or Ss treated-GM-MDMs, and, conversely, upregulated in GM-MDMs treated with Met + Ss in combination, indicating that arginase activity dominates that of iNOS when the two treatments are associated. Moreover, combination of Met with Ss significantly upregulated hydrogen peroxide (H₂O₂) production and phagocytic capacity, but significantly downregulated the production of IL-1β, iNOS activity and killing capacity. On the contrary, we show that Met alone induced significant downregulation of phagocytic capacity and slight upregulation of killing capacity. Nevertheless, Ss seems to accentuate the effect of Met on the downregulation of NO production, as well as to reverse its effect on both phagocytic and killing capacities. On the other hand, all treatments induced a sharp decrease in relative levels of NADH dehydrogenase, and a marked decrease in the levels of _ifCa²⁺. Finally, we found that GM-MDMs treated with Met or Ss, or Met combined with Ss exhibited different functional activation phenotypes, as indicated by the surface expression of co-stimulatory and cell activation and presentation molecules CD14, CD80, CD86 and HLA-DR.

CONCLUSIONS

Our results demonstrated that Met/Ss combination can play an important role in the modulation of functional activities of human LPS-activated GM-MDMs. Additionally, the overall effects of Met and the induction of "M2" GM-MDMs-associated arginase could be influenced by its combination with Ss.

Sleeping Beauty and the Microenvironment Enchantment: Microenvironmental Regulation of the Proliferation-Quiescence Decision in Normal Tissues and in Cancer Development

Cells from prokaryota to the more complex metazoans cease proliferating at some point in their lives and enter a reversible, proliferative-dormant state termed quiescence. The appearance of quiescence in the course of evolution was essential to the acquisition of multicellular specialization and compartmentalization and is also a central aspect of tissue function and homeostasis. But what makes a cell cease proliferating even in the presence of nutrients, growth factors, and mitogens? And what makes some cells "wake up" when they should not, as is the case in cancer? Here, we summarize and discuss evidence showing how microenvironmental cues such as those originating from metabolism, extracellular matrix (ECM) composition and arrangement, neighboring cells and tissue architecture control the cellular proliferation-quiescence decision, and how this complex regulation is corrupted in cancer.

[Is cancer incidence different between type 2 diabetes patients compared to non-diabetics in hemodialysis? A study from the REIN registry]

BACKGROUND AND OBJECTIVES

In France, diabetes mellitus is now the second cause of end stage renal disease. In a large previous French national study, we observed that dialyzed diabetics have a significant lower risk of death by cancer. This first study was focused on cancer death but did not investigate cancer incidence. In this context, the aim of this second study was to compare the incidence of cancer in diabetic dialyzed patients compared to non-diabetic dialyzed patients in a French region.

METHODS

This epidemiologic multicentric study included 588 diabetic and non-diabetic patients starting hemodialysis between 2002 and 2007 in Bretagne. Data were issued from REIN registry and cancer incidence were individually collected from medical records. Diabetics and non-diabetics were matched one by one on age, sex and year of dialysis initiation.

RESULTS

During the follow-up, we observed 28 cancers (9.4%) in diabetic patients and 26 cancers (8.9%) in non-diabetics patients. The cumulative incidence to develop a cancer 2 years after the dialysis start was approximately 6% in both diabetics and non-diabetics patients. In univariate Fine and Gray analysis, BMI, hemoglobin, statin use had P-value<0.2. However, in the adjusted model, these variables were not significantly associated with cancer incidence.

CONCLUSION

This study lead on a little number of dialyzed patients did not show any significant difference on cancer incidence between diabetic and non-diabetic patients after hemodialysis start.

Re-evaluation of cytostatic therapies for meningiomas in vitro

PURPOSE

The purpose was to re-evaluate in cell culture models the therapeutic usefulness of some discussed chemotherapies or targeted therapies for meningiomas with a special emphasis on the role of the neurofibromatosis type 2 (NF2) tumor suppressor, which had been neglected so far. In addition, the study intended to evaluate a potential benefit from a treatment with drugs which are well established in other fields of medicine and have been linked recently with tumor disease by epidemiological studies.

METHODS

Meningioma cell lines corresponding to various subtypes and pairs of syngenic meningioma cell lines with or without shRNA-induced NF2 knockdown were analyzed for their dose-dependent response to the drugs in microtiter tetrazolium assays, BrdU assays and for selected cases in ELISAs measuring nucleosome liberation to specifically separate cell death from pure inhibition of cell proliferation.

RESULTS

We confirmed a moderate efficacy of hydroxyurea (HU) in clinically relevant concentrations. Under appropriate dosing, we neither detected major responses to the alkylating compound temozolomide nor to various drugs targeting membrane receptors or enzymes (tamoxifen, erlotinib, mifepristone, losartan, metformin and verapamil). Only concentrations far beyond achievable serum levels generated significant effects with the exception of losartan, which showed no effects at all. Chemosensitivity varied markedly among meningioma cell lines. Importantly, cells with NF2 loss exhibited a significantly higher induction of cell death by HU.

CONCLUSIONS

Alternative chemotherapeutic or targeted approaches besides HU have still to be evaluated in further studies, and the role of NF2 must be taken into account.

Complications of diabetes therapy

Current strategies for the treatment of type 2 diabetes mellitus promote individualized plans to achieve target glucose levels on a patient-by-patient basis while minimizing treatment related risks. Maintaining glycemic control over time is a significant challenge because of the progressive nature of diabetes as a result of declining β-cell function. This article identifies complications of non-insulin treatments for diabetes. The major classes of medications are reviewed with special focus on target population, mechanism of action, effect on weight, cardiovascular outcomes and additional class-specific side effects including effects on bone. Effects on β-cell function are also highlighted.