Immune-mediated antitumor effect by type 2 diabetes drug, metformin. Proc Natl Acad Sci U S A. 2015;112:1809-1814. [PMID: 25624476 DOI: 10.1073/pnas.1417636112]

Phase II trial of nivolumab and metformin in patients with treatment-refractory microsatellite stable metastatic colorectal cancer

BACKGROUND

Preclinical studies showed metformin reduces exhaustion of tumor-infiltrating lymphocytes and potentiates programmed cell death protein-1 (PD-1) blockade. We hypothesized that metformin with nivolumab would elicit potent antitumor and immune modulatory activity in metastatic microsatellite stable (MSS) colorectal cancer (CRC). We evaluated this hypothesis in a phase II study.

METHODS

Nivolumab (480 mg) was administered intravenously every 4 weeks while metformin (1000 mg) was given orally, two times per day following a 14-day metformin only lead-in phase. Patients ≥18 years of age, with previously treated, stage IV MSS CRC, and Eastern Cooperative Oncology Group 0-1, having received no prior anti-PD-1 agent were eligible. The primary endpoint was overall response rate with secondary endpoints of overall survival (OS) and progression-free survival (PFS). Correlative studies using paired pretreatment/on-treatment biopsies and peripheral blood evaluated a series of immune biomarkers in the tumor microenvironment and systemic circulation using ChipCytometry and flow cytometry.

RESULTS

A total of 24 patients were enrolled, 6 patients were replaced per protocol, 18 patients had evaluable disease. Of the 18 evaluable patients, 11/18 (61%) were women and the median age was 58 (IQR 50-67). Two patients had stable disease, but no patients had objective response, hence the study was stopped for futility. Median OS and PFS was 5.2 months (95% CI (3.2 to 11.7)) and 2.3 months (95% CI (1.7 to 2.3)). Most common grade 3/4 toxicities: Anemia (n=2), diarrhea (n=2), and fever (n=2). Metformin alone failed to increase the infiltration of T-cell subsets in the tumor, but combined metformin and nivolumab increased percentages of tumor-infiltrating leukocytes (p=0.031). Dual treatment also increased Tim3+ levels in patient tissues and decreased naïve CD8+T cells (p=0.0475).

CONCLUSIONS

Nivolumab and metformin were well tolerated in patients with MSS CRC but had no evidence of efficacy. Correlative studies did not reveal an appreciable degree of immune modulation from metformin alone, but showed trends in tumorous T-cell infiltration as a result of dual metformin and PD-1 blockade despite progression in a majority of patients.

Metabolic reprogramming in inflammaging and aging in T cells

Aging represents an emerging challenge for public health due to the declined immune responses against pathogens, weakened vaccination efficacy, and disturbed tissue homeostasis. Metabolic alterations in cellular and systemic levels are also known to be cardinal features of aging. Moreover, cellular metabolism has emerged to provide regulations to guide immune cell behavior via modulations on signaling cascades and epigenetic landscape, and the aberrant aging process in immune cells can lead to inflammaging, a chronic and low-grade inflammation that facilitates aging by perturbing homeostasis in tissues and organs. Here, we review how the metabolic program in T cells is influenced by the aging process and how aged T cells modulate inflammaging. In addition, we discuss the potential approaches to reverse or ameliorate aging by rewiring the metabolic programming of immune cells.

It is worth the weight: obesity and the transition from monoclonal gammopathy of undetermined significance to multiple myeloma

The overweight/obesity epidemic is a serious public health concern that affects >40% of adults globally and increases the risk of numerous chronic diseases, such as type 2 diabetes, heart disease, and various cancers. Multiple myeloma (MM) is a lymphohematopoietic cancer caused by the uncontrolled clonal expansion of plasma cells. Recent studies have shown that obesity is a risk factor not only for MM but also monoclonal gammopathy of undetermined significance (MGUS), a precursor disease state of MM. Furthermore, obesity may promote the transition from MGUS to MM. Thus, in this review, we summarize the epidemiological evidence regarding the role of obesity in MM and MGUS, discuss the biologic mechanisms that drive these disease processes, and detail the obesity-targeted pharmacologic and lifestyle interventions that may reduce the risk of progression from MGUS to MM.

Research Progress of Metformin in the Treatment of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common malignancies and has a high mortality, posing a great threat to both human physical and mental health. With the advancement of scientific research, a variety of cancer therapies have been used for OSCC treatment. However, the prognosis of OSCC shows no significant improvement. Metformin has been recognized as the first-line drug for the treatment of diabetes, and recent studies have shown that metformin has a remarkable suppressive effect on tumor progression. Metformin can not only affect the energy metabolism of tumor cells but also play an antitumor role by modulating the tumor microenvironment and cancer stem cells. In this review, the molecular mechanism of metformin and its anticancer mechanism in OSCC are summarized. In addition, this article summarizes the side effects of metformin and the future prospects of its application in the treatment of OSCC.

The Impact of Metformin on Tumor-Infiltrated Immune Cells: Preclinical and Clinical Studies

The tumor microenvironment (TME) plays a pivotal role in the fate of cancer cells, and tumor-infiltrating immune cells have emerged as key players in shaping this complex milieu. Cancer is one of the leading causes of death in the world. The most common standard treatments for cancer are surgery, radiation therapy, and chemotherapeutic drugs. In the last decade, immunotherapy has had a potential effect on the treatment of cancer patients with poor prognoses. One of the immune therapeutic targeted approaches that shows anticancer efficacy is a type 2 diabetes medication, metformin. Beyond its glycemic control properties, studies have revealed intriguing immunomodulatory properties of metformin. Meanwhile, several studies focus on the impact of metformin on tumor-infiltrating immune cells in various tumor models. In several tumor models, metformin can modulate tumor-infiltrated effector immune cells, CD8+, CD4+ T cells, and natural killer (NK) cells, as well as suppressor immune cells, T regulatory cells, tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs). In this review, we discuss the role of metformin in modulating tumor-infiltrating immune cells in different preclinical models and clinical trials. Both preclinical and clinical studies suggest that metformin holds promise as adjunctive therapy in cancer treatment by modulating the immune response within the tumor microenvironment. Nonetheless, both the tumor type and the combined therapy have an impact on the specific targets of metformin in the TME. Further investigations are warranted to elucidate the precise mechanisms underlying the immunomodulatory effects of metformin and to optimize its clinical application in cancer patients.

Metformin promotes cGAS/STING signaling pathway activation by blocking AKT phosphorylation in gastric cancer

The cGAS/STING signaling pathway plays a pivotal role in regulating innate immunity. Emerging novel drugs aim to regulate the anti-tumor immune response by activating innate immunity. The anti-diabetic drug metformin has been reported to exhibit anti-cancer effect against various types of cancer. However, the role of metformin in regulating the cGAS/STING signaling pathway in gastric cancer remains unknown. In our study, we first used bioinformatic analysis to detect that metformin is closely related to tumor immunity in multiple tumors. Next, we validated the function of metformin in activating the cGAS/STING signaling pathway in gastric cancer cell lines. In addition, KEGG pathway enrichment analysis showed that metformin is negatively correlated with the PI3K/AKT signaling pathway in gastric cancer. We further verified that metformin activates the cGAS/STING signaling pathway by blocking AKT phosphorylation. Moreover, we found that metformin regulates the AKT signaling pathway by mediating the transcription factor SOX2. Thus, our study indicates that metformin activates the cGAS/STING signaling pathway by suppressing SOX2/AKT and has promising potential in gastric cancer immunotherapy.

Metformin as a booster of cancer immunotherapy

Metformin, a biguanide antidiabetic, has been studied for its repurposing effects in oncology. Although a modest effect was observed in a single-agent regimen, metformin can synergize the anti-tumor effects of other modalities. The promising combination for cancer treatment is with immunotherapy. Despite high efficacy for some cancers, immunotherapy could be limited by modulation of the tumor immune microenvironment and the immune exhaustion of cytotoxic immune cells. Combining immunotherapy with metformin, thus, exerted a rescuing effect of immunotherapy and potentiated the anti-tumor effects of each other. Although not fully understood, metformin shows promoting effects of immunotherapy by several mechanisms. Those proposed mechanisms have been partially proven and are suggested for possible therapeutic strategies for cancer treatment. In this review, a state-of-the-art of metformin's boosting effects on immunotherapy is reviewed and discussed. The future directions for metformin research in preclinical and clinical immunotherapy are also suggested.

Metformin Reprograms Tryptophan Metabolism to Stimulate CD8+ T-cell Function in Colorectal Cancer

Colorectal carcinogenesis coincides with immune cell dysfunction. Metformin has been reported to play a role in stimulating antitumor immunity, suggesting it could be used to overcome immunosuppression in colorectal cancer. Herein, using single-cell RNA sequencing (scRNA-seq), we showed that metformin remodels the immune landscape of colorectal cancer. In particular, metformin treatment expanded the proportion of CD8+ T cells and potentiated their function. Analysis of the metabolic activities of cells in the colorectal cancer tumor microenvironment (TME) at a single-cell resolution demonstrated that metformin reprogrammed tryptophan metabolism, which was reduced in colorectal cancer cells and increased in CD8+ T cells. Untreated colorectal cancer cells outcompeted CD8+ T cells for tryptophan, leading to impaired CD8+ T-cell function. Metformin in turn reduced tryptophan uptake by colorectal cancer cells, thereby restoring tryptophan availability for CD8+ T cells and increasing their cytotoxicity. Metformin inhibited tryptophan uptake in colorectal cancer cells by downregulating MYC, which led to a reduction in the tryptophan transporter SLC7A5. This work highlights metformin as an essential regulator of T-cell antitumor immunity by reprogramming tryptophan metabolism, suggesting it could be a potential immunotherapeutic strategy for treating colorectal cancer.

SIGNIFICANCE

Analysis of the impact of metformin on the colorectal cancer immunometabolic landscape at a single-cell resolution shows that metformin alters cancer cell tryptophan metabolism to stimulate CD8+ T-cell antitumor activity.

Metabolism and senescence in the immune microenvironment of osteosarcoma: focus on new therapeutic strategies

Osteosarcoma is a highly aggressive and metastatic malignant tumor. It has the highest incidence of all malignant bone tumors and is one of the most common solid tumors in children and adolescents. Osteosarcoma tissues are often richly infiltrated with inflammatory cells, including tumor-associated macrophages, lymphocytes, and dendritic cells, forming a complex immune microenvironment. The expression of immune checkpoint molecules is also high in osteosarcoma tissues, which may be involved in the mechanism of anti-tumor immune escape. Metabolism and senescence are closely related to the immune microenvironment, and disturbances in metabolism and senescence may have important effects on the immune microenvironment, thereby affecting immune cell function and immune responses. Metabolic modulation and anti-senescence therapy are gaining the attention of researchers as emerging immunotherapeutic strategies for tumors. Through an in-depth study of the interconnection of metabolism and anti- senescence in the tumor immune microenvironment and its regulatory mechanism on immune cell function and immune response, more precise therapeutic strategies can be developed. Combined with the screening and application of biomarkers, personalized treatment can be achieved to improve therapeutic efficacy and provide a scientific basis for clinical decision-making. Metabolic modulation and anti- senescence therapy can also be combined with other immunotherapy approaches, such as immune checkpoint inhibitors and tumor vaccines, to form a multi-level and multi-dimensional immunotherapy strategy, thus further enhancing the effect of immunotherapy. Multidisciplinary cooperation and integrated treatment can optimize the treatment plan and maximize the survival rate and quality of life of patients. Future research and clinical practice will further advance this field, promising more effective treatment options for patients with osteosarcoma. In this review, we reviewed metabolic and senescence characteristics in the immune microenvironment of osteosarcoma and related immunotherapies, and provide a reference for development of more personalized and effective therapeutic strategies.

Metformin and cancer hallmarks: shedding new lights on therapeutic repurposing

Metformin is a well-known anti-diabetic drug that has been repurposed for several emerging applications, including as an anti-cancer agent. It boasts the distinct advantages of an excellent safety and tolerability profile and high cost-effectiveness at less than one US dollar per daily dose. Epidemiological evidence reveals that metformin reduces the risk of cancer and decreases cancer-related mortality in patients with diabetes; however, the exact mechanisms are not well understood. Energy metabolism may be central to the mechanism of action. Based on altering whole-body energy metabolism or cellular state, metformin's modes of action can be divided into two broad, non-mutually exclusive categories: "direct effects", which induce a direct effect on cancer cells, independent of blood glucose and insulin levels, and "indirect effects" that arise from systemic metabolic changes depending on blood glucose and insulin levels. In this review, we summarize an updated account of the current knowledge on metformin antitumor action, elaborate on the underlying mechanisms in terms of the hallmarks of cancer, and propose potential applications for repurposing metformin for cancer therapeutics.

Metformin is associated with improved clinical outcomes in patients with melanoma: a retrospective, multi-institutional study

Background

Pre-clinical studies have shown that metformin reduces intratumoral hypoxia, improves T-cell function, and increases sensitivity to PD-1 blockade, and metformin exposure has been associated with improved clinical outcomes in various types of cancer. However, the impact of this drug in diabetic melanoma patients has not yet been fully elucidated.

Methods

We reviewed 4,790 diabetic patients with stage I-IV cutaneous melanoma treated at the UPMC-Hillman Cancer Center and Memorial Sloan Kettering Cancer Center between 1996-2020. The primary endpoints included recurrence rates, progression free survival (PFS), and overall survival (OS) with and without metformin exposure. Tabulated variables included BRAF mutational status, immunotherapy (IMT) by type, and incidence of brain metastases.

Results

The five-year incidence of recurrence in stage I/II patients was significantly reduced with metformin exposure (32.3% vs 47.7%, p=0.012). The five-year recurrence rate for stage III patients was also significantly reduced (58.3% vs 77.3%, p=0.013) in the metformin cohort. OS was numerically increased in nearly all stages exposed to metformin, though this did not reach statistical significance. The incidence of brain metastases was significantly lower in the metformin cohort (8.9% vs 14.6%, p=0.039).

Conclusion

This is the first study to demonstrate significantly improved clinical outcomes in diabetic melanoma patients exposed to metformin. Overall, these results provide further rationale for ongoing clinical trials studying the potential augmentation of checkpoint blockade with metformin in advanced melanoma.

The development and benefits of metformin in various diseases

Metformin has been used for the treatment of type II diabetes mellitus for decades due to its safety, low cost, and outstanding hypoglycemic effect clinically. The mechanisms underlying these benefits are complex and still not fully understood. Inhibition of mitochondrial respiratory-chain complex I is the most described downstream mechanism of metformin, leading to reduced ATP production and activation of AMP-activated protein kinase (AMPK). Meanwhile, many novel targets of metformin have been gradually discovered. In recent years, multiple pre-clinical and clinical studies are committed to extend the indications of metformin in addition to diabetes. Herein, we summarized the benefits of metformin in four types of diseases, including metabolic associated diseases, cancer, aging and age-related diseases, neurological disorders. We comprehensively discussed the pharmacokinetic properties and the mechanisms of action, treatment strategies, the clinical application, the potential risk of metformin in various diseases. This review provides a brief summary of the benefits and concerns of metformin, aiming to interest scientists to consider and explore the common and specific mechanisms and guiding for the further research. Although there have been countless studies of metformin, longitudinal research in each field is still much warranted.

Efficacy of metformin adjunctive therapy as the treatment for non-diabetic patients with advanced non-small cell lung cancer: A Systematic review and Meta-analysis

Background

Currently, the anticancer effects of metformin on different types of lung cancer have been frequently studied. However, the relationship between metformin and prognosis in nondiabetic patients with lung cancer remains controversial. To systematically evaluate the efficacy of metformin adjunctive therapy as the treatment for nondiabetic patients with advanced non-small cell lung cancer (NSCLC) to provide an evidence-based reference for clinical medication.

Materials and Methods

The literatures related to Phase II or III randomized controlled trials (RCTs) of metformin adjunctive therapy in nondiabetic patients with advanced NSCLC, including EMBASE, PubMed, the Cochrane Library, and Scopus database, were retrieved by computer, and the search time ranged from January 2017 to August 2022. The risk of bias assessment tool recommended by Cochrane Systematic Evaluator Manual 5.1.0 was used to evaluate the quality of the RCTs included. Rev Man 5.3 software and STATA15.0 were used for meta-analysis.

Results

A total of 8 studies were included (925 patients). Meta-analysis results showed that there were no significant differences in progression-free survival (PFS) (hazard ratio [HR] = 0.95, 95% confidence interval [CI]: 0.66-1.36, P = 0.77), overall survival (OS) (HR = 0.89, 95% CI: 0.61-1.30, P = 0.55, n =7), objective response rate (ORR) (odds ratio [OR] = 1.37, 95% CI: 0.76-2.46, P = 0.30), and 1-year PFS rate (OR = 0.87, 95% CI: 0.39-1.94, P = 0.73, n = 3). Sensitivity analysis showed that PFS and OS indexes were stable.

Conclusion

Metformin adjunctive therapy can improve the DCR of nondiabetic patients with advanced NSCLC. In addition, the patients cannot obtain a prolonged PFS, OS, 1-year PFS rate, and higher ORR rate.

The role of myeloid-derived suppressor cells in liver cancer

MDSCs are immature myeloid immune cells, which accumulate in models of liver cancer to reduce effector immune cell activity, contribute to immune escape and treatment resistance. The accumulation of MDSCs suppresses the role of CTL and the killing effects of NK cells, induces the accumulation of Treg cells, and blocks the antigen presentation of DCs, thus promoting the progression of liver cancer. Recently, immunotherapy has emerged a valuable approach following chemoradiotherapy in the therapy of advanced liver cancer. A considerable increasing of researches had proved that targeting MDSCs has become one of the therapeutic targets to enhance tumor immunity. In preclinical study models, targeting MDSCs have shown encouraging results in both alone and in combination administration. In this paper, we elaborated immune microenvironment of the liver, function and regulatory mechanisms of MDSCs, and therapeutic approaches to target MDSCs. We also expect these strategies to supply new views for future immunotherapy for the treatment of liver cancer.

Targeting Cancer Metabolism to Improve Outcomes with Immune Checkpoint Inhibitors

Immune checkpoint inhibitors have revolutionized the treatment paradigm of several cancers. However, not all patients respond to treatment. Tumor cells reprogram metabolic pathways to facilitate growth and proliferation. This shift in metabolic pathways creates fierce competition with immune cells for nutrients in the tumor microenvironment and generates by-products harmful for immune cell differentiation and growth. In this review, we discuss these metabolic alterations and the current therapeutic strategies to mitigate these alterations to metabolic pathways that can be used in combination with checkpoint blockade to offer a new path forward in cancer management.

Metformin plays an antitumor role by downregulating inhibitory cells and immune checkpoint molecules while activating protective immune responses in breast cancer

This study seeks to test the effect of metformin treatment on the outcomes of breast cancer in BALB/c mice bearing 4 T1 breast cancer cells. The survival rate and tumor size of mice were compared, as well as evaluation of the changes of immune cells in spleens and the microenvironment of tumors using flow cytometry and ELISA. Our results demonstrate that metformin prolongs mouse survival. A significant decrease in M2-like macrophages (F4/80⁺CD206⁺) was found in mice spleen treated with metformin. The treatment also inhibited monocytic myeloid-derived suppressor cells (M-MDSCs, CD11b⁺Gr-1⁺) and regulatory T cells (Tregs, CD4⁺CD25⁺Foxp3⁺). Metformin treatment resulted in an increase in the level of IFN-γ and a decrease in IL-10. Expression of the immune checkpoint molecule PD-1 on T cells was inhibited following treatment. Metformin enhances local antitumor activity in the tumor microenvironment, and our data supports the drug as a candidate for evaluation in the treatment of breast cancer.

Metformin improves cancer immunotherapy by directly rescuing tumor-infiltrating CD8 T lymphocytes from hypoxia-induced immunosuppression

BACKGROUND

Despite their revolutionary success in cancer treatment over the last decades, immunotherapies encounter limitations in certain tumor types and patients. The efficacy of immunotherapies depends on tumor antigen-specific CD8 T-cell viability and functionality within the immunosuppressive tumor microenvironment, where oxygen levels are often low. Hypoxia can reduce CD8 T-cell fitness in several ways and CD8 T cells are mostly excluded from hypoxic tumor regions. Given the challenges to achieve durable reduction of hypoxia in the clinic, ameliorating CD8 T-cell survival and effector function in hypoxic condition could improve tumor response to immunotherapies.

METHODS

Activated CD8 T cells were exposed to hypoxia and metformin and analyzed by fluorescence-activated cell sorting for cell proliferation, apoptosis and phenotype. In vivo, metformin was administered to mice bearing hypoxic tumors and receiving either adoptive cell therapy with tumor-specific CD8 T cells, or immune checkpoint inhibitors; tumor growth was followed over time and CD8 T-cell infiltration, survival and localization in normoxic or hypoxic tumor regions were assessed by flow cytometry and immunofluorescence. Tumor oxygenation and hypoxia were measured by electron paramagnetic resonance and pimonidazole staining, respectively.

RESULTS

We found that the antidiabetic drug metformin directly improved CD8 T-cell fitness in hypoxia, both in vitro and in vivo. Metformin rescued murine and human CD8 T cells from hypoxia-induced apoptosis and increased their proliferation and cytokine production, while blunting the upregulation of programmed cell death protein 1 and lymphocyte-activation gene 3. This appeared to result from a reduced production of reactive oxygen species, due to the inhibition of mitochondrial complex I. Differently from what others reported, metformin did not reduce tumor hypoxia, but rather increased CD8 T-cell infiltration and survival in hypoxic tumor areas, and synergized with cyclophosphamide to enhance tumor response to adoptive cell therapy or immune checkpoint blockade in different tumor models.

CONCLUSIONS

This study describes a novel mechanism of action of metformin and presents a promising strategy to achieve immune rejection in hypoxic and immunosuppressive tumors, which would otherwise be resistant to immunotherapy.

Targeting Myc-driven stress addiction in colorectal cancer

MYC is a proto-oncogene that encodes a powerful regulator of transcription and cellular programs essential for normal development, as well as the growth and survival of various types of cancer cells. MYC rearrangement and amplification is a common cause of hematologic malignancies. In epithelial cancers such as colorectal cancer, genetic alterations in MYC are rare. Activation of Wnt, ERK/MAPK, and PI3K/mTOR pathways dramatically increases Myc levels through enhanced transcription, translation, and protein stability. Elevated Myc promotes stress adaptation, metabolic reprogramming, and immune evasion to drive cancer development and therapeutic resistance through broad changes in transcriptional and translational landscapes. Despite intense interest and effort, Myc remains a difficult drug target. Deregulation of Myc and its targets has profound effects that vary depending on the type of cancer and the context. Here, we summarize recent advances in the mechanistic understanding of Myc-driven oncogenesis centered around mRNA translation and proteostress. Promising strategies and agents under development to target Myc are also discussed with a focus on colorectal cancer.

Metformin enhances T lymphocyte anti-tumor immunity by increasing the infiltration via vessel normalization

Abnormal tumor vasculature blocks the extravasation of T lymphocytes into the tumor, thereby suppressing anti-tumor immunity. Recently, metformin has been shown to affect tumor vasculature and enhance T lymphocyte anti-tumor immunity. However, whether or how metformin affects T lymphocyte anti-tumor immunity via a vascular mechanism remains poorly understood. Herein, we show that a large number of CD8⁺ lymphocytes gathered in the peri-tumoral region, while very few infiltrated the tumor. Metformin administration increased the expression of anti-tumor immunity-associated genes and the number of tumor-infiltrating CD8⁺ lymphocytes. Injection of CD8 but not CD4 neutralization antibody into tumor-bearing mice significantly abrogated the anti-tumor effect of metformin. Critically, CD8⁺ lymphocytes were found to pass through the wall of perfused vessel. Further results of immunofluorescent staining showed that metformin greatly elevated tumor perfusion, which was accompanied by increased vascular maturity in the intratumoral region (ITR) but not peritumoral region (PTR). These findings provide evidence for the vascular mechanism involved in metformin-induced enhancement of T lymphocyte anti-tumor immunity. By remodeling the abnormal tumor vasculature, also called vessel normalization metformin increases vascular maturity and tumor perfusion, thus allowing more CD8⁺ lymphocytes to infiltrate the tumor.

Metformin-containing hydrogel scaffold to augment CAR-T therapy against post-surgical solid tumors

Physiological barriers and immunosuppressive microenvironments of solid tumors present considerable hurdles to Chimeric antigen receptor T (CAR-T) cell therapy. Herein, we discovered that metformin, a prescribed drug for type 2 diabetes, could up-regulate the oxidative phosphorylation of CAR-T cells, increase their energy metabolism, and further promote their proliferation. Inspired by this finding, we designed a hydrogel scaffold to co-deliver metformin and CAR-T cells by adding CAR-T cells into a lyophilized alginate hydrogel containing metformin. The obtained hydrogel scaffold after being implanted into the tumor resection cavity could act as a cell reservoir to sustainably release both CAR-T cells and metformin. While the released metformin could suppress oxidative and glycolytic metabolism of cancer cells and lead to decreased tumor hypoxia, CAR-T cells would respond to metformin by markedly up-regulating oxidative metabolism and adopting a long-lived, highly activated phenotype, contributing to elevated antitumor responses. As demonstrated in several post-surgical tumor models, the proliferation and tumor-infiltration of CAR-T cells were significantly enhanced and the treatment efficacy of CAR-T cells was augmented, against both local tumors and distant abscopal tumors, while showing reduced systemic immune-related adverse effects. Our work presents a new strategy to achieve effective yet safe CAR-T therapy against solid tumors using a cell-delivery scaffold based on clinically validated drugs and biomaterials.

PD-L1 antibody enhanced β-glucan antitumor effects via blockade of the immune checkpoints in a melanoma model

In the tumor microenvironment (TME), one of the major functions of tumor-recruited CD11b⁺ cells are the suppression of the T-cell-mediated anti-tumor immune response. β-glucan could convert the phenotype of tumor-recruited CD11b⁺ cells from the suppressive to the promotive, and enhanced their anti-tumor effects. However, β-glucan could enhance the PD-1/PD-L1 expression on CD11b⁺ cells, while PD-1 could inhibit macrophage phagocytosis and PD-L1 could induce a co-inhibitory signal in T-cells and lead to T-cell apoptosis and anergy. These protumor effects may be reversed by PD-1/PD-L1 block therapy. In the present study, we focused on the efficacy of β-glucan anti-tumor therapy combined with anti-PD-L1 mAb treatment, and the mechanism of their synergistic effects could be fully verified. We verified the effect of β-glucan (i.e., inflammatory cytokine secretion of TNF-α, IL-12, IL-6, IL-1β and the expression of immune checkpoint PD-1/PD-L1) in naïve mouse peritoneal exudate CD11b⁺ cells. In our mouse melanoma model, treatment with a PD-L1 blocking antibody with β-glucan synergized tumor regression. After treatment with β-glucan and anti-PD-L1 mAb antibody, tumor infiltrating leukocyte (TILs) not only showed a competent T-cell function (CD107a, perforin, IL-2, IFN-γ and Ki67) and CTL population, but also showed enhanced tumor-recruited CD11b⁺ cell activity (IL-12, IL-6, IL-1β and PD-1). This effect was also verified in the peritoneal exudate CD11b⁺ cells of tumor-bearing mice. PD-1/PD-L1 blockade therapy enhanced the β-glucan antitumor effects via the blockade of tumor-recruited CD11b⁺ cell immune checkpoints in the melanoma model.

Melanoma antigens recognized by T cells and their use for immunotherapy

Melanoma has been a prototype for cancer immunology research, and the mechanisms of anti-tumor T-cell responses have been extensively investigated in patients treated with various immunotherapies. Individual differences in cancer-immune status are defined mainly by cancer cell characteristics such as DNA mutations generating immunogenic neo-antigens, and oncogene activation causing immunosuppression, but also by patients' genetic backgrounds such as HLA types and genetic polymorphisms of immune related molecules, and environmental and lifestyle factors such as UV rays, smoking, gut microbiota and concomitant medications; these factors have an influence on the efficacy of immunotherapy. Recent comparative studies on responders and non-responders in immune-checkpoint inhibitor therapy using various new technologies including multi-omics analyses on genomic DNA, mRNA, metabolites and microbiota and single cell analyses of various immune cells have led to the advance of human tumor immunology and the development of new immunotherapy. Based on the new findings from these investigations, personalized cancer immunotherapies along with appropriate biomarkers and therapeutic targets are being developed for patients with melanoma. Here, we will discuss one of the essential subjects in tumor immunology: identification of immunogenic tumor antigens and their effective use in various immunotherapies including cancer vaccines and adoptive T-cell therapy.

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.

Association of metformin use and survival in patients with cutaneous melanoma and diabetes

BACKGROUND

Metformin use has been associated with improved survival in patients with different types of cancer, but research regarding the effect of metformin on cutaneous melanoma (CM) survival is sparse and inconclusive.

OBJECTIVES

To investigate the association between metformin use and survival among patients with CM and diabetes.

METHODS

All adult patients with a primary invasive CM between 2007 and 2014 were identified in the Swedish Melanoma Registry and followed until death, or end of follow-up on 31 December 2017 in this population-based cohort study. Patients with both CM and type 2 diabetes mellitus were assessed further. Overall survival (OS) and melanoma-specific survival (MSS) were the primary endpoints. Cox proportional hazard models estimating crude and adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were used comparing peridiagnostic use vs. nonuse of metformin. Dose response was evaluated based on defined daily doses.

RESULTS

Among a total of 23 507 patients, 1162 patients with CM and type 2 diabetes mellitus were included in the final cohort, with a median follow-up time of 4.1 years (interquartile range 2.4-6.1). Peridiagnostic metformin use was associated with a significantly decreased risk of death by any cause (HR 0.68, 95% CI 0.57-0.81). Cumulative pre- and postdiagnostic metformin use was also associated with improved OS: the HR for prediagnostic use was 0.90 (95% CI 0.86-0.95) for every 6 months of use and the HR for postdiagnostic use ranged from 0.98 (95% CI 0.97-0.98) for 0-6 months to 0.59 (0.49-0.70) for 24-30 months of use. No association was found for metformin use and MSS.

CONCLUSIONS

Metformin use was associated with improved OS in patients with CM and diabetes regardless of timing (pre-, post- or peridiagnostic use) and followed a dose-response pattern. However, further research regarding the underlying mechanisms is warranted.

Effect of metformin on outcomes of patients treated with immune checkpoint inhibitors: a retrospective cohort study

BACKGROUND

Immune checkpoint inhibitors have transformed the treatment landscape of cancer treatment, but only a fraction of patients responds to treatment, leading to an increasing effort to repurpose clinically approved medications to augment ICI therapy. Metformin has been associated with improved survival outcomes in patients undergoing conventional chemotherapy. However, whether metformin provides survival benefits in patients receiving immune checkpoint inhibitors (ICIs) is unknown.

METHODS

We performed a retrospective cohort study at two tertiary referral centers in Taiwan. All adult diabetes mellitus patients who were treated with ICIs between January 2015 and December 2021 were included. The primary and secondary outcomes were overall survival (OS) and progression-free survival (PFS), respectively.

RESULTS

In total, 878 patients were enrolled in our study, of which 86 patients used metformin and 78 patients used non-metformin diabetes medications. Compared with non-users, metformin users had a longer median OS (15.4 [IQR 5.6-not reached] vs. 6.1 [IQR, 0.8-21.0] months, P = 0.003) and PFS (5.1 [IQR 2.0-14.3] vs. 1.9 [IQR 0.7-8.6] months, P = 0.041). In a univariate Cox proportional hazard analysis, the use of metformin was associated with a reduction in the risk of mortality (HR: 0.53 [95% confidence interval: 0.35-0.81], P = 0.004) and disease progression (HR: 0.69 [95% CI 0.49-0.99], P = 0.042). The use of metformin remained associated with a lower risk of mortality after adjusting for baseline variables such as age, cancer stage, and underlying comorbidities (OS, HR: 0.55 [95% CI 0.34-0.87], P = 0.011). Similarly, the use of metformin was associated with a lower risk of disease progression. Importantly, the use of metformin before ICI initiation was not associated with a reduction in mortality (HR: 0.61 [95% CI 0.27-1.42], P = 0.25) or disease progression (HR: 0.69 [95% CI 0.33-1.43], P = 0.32).

CONCLUSION

The use of metformin is associated with survival benefits in patients undergoing immunotherapy. Prospective clinical trials are warranted to define the role of metformin in augmenting immunotherapy.

Metformin and Its Immune-Mediated Effects in Various Diseases

Metformin has been a long-standing prescribed drug for treatment of type 2 diabetes (T2D) and its beneficial effects on virus infection, autoimmune diseases, aging and cancers are also recognized. Metformin modulates the differentiation and activation of various immune-mediated cells such as CD4+ and CD+8 T cells. The activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin complex 1 (mTORC1) pathway may be involved in this process. Recent studies using Extracellular Flux Analyzer demonstrated that metformin alters the activities of glycolysis, oxidative phosphorylation (OXPHOS), lipid oxidation, and glutaminolysis, which tightly link to the modulation of cytokine production in CD4+ and CD+8 T cells in various disease states, such as virus infection, autoimmune diseases, aging and cancers.

Effect of Metformin on the Prognosis of Gastric Cancer Patients with Type 2 Diabetes Mellitus: A Meta-Analysis Based on Retrospective Cohort Studies

BACKGROUND

Metformin is one of the most common drugs for type 2 diabetes mellitus (T2DM) treatment. In addition, metformin intends to have a positive effect on the prognosis of several cancers. However, the therapeutic effect of metformin on gastric cancer (GC) remains controversial. This study explores and updates the therapeutic effect of metformin in GC patients with T2DM.

METHODS

We searched through PubMed, Embase, Web of Science, and the Cochrane Library for relevant articles by July 2022. The relationship between metformin therapy and the prognosis of GC patients with T2DM was evaluated based on the hazard ratio (HR) at a 95% confidence interval (95% CI). Overall survival (OS), cancer-specific survival (CSS), and progression-free survival (PFS) were the primary outcomes analyzed.

RESULTS

Seven retrospective cohort studies with a combined 2,858 patients met the inclusion criteria. OS and CSS were reported in six studies, and PFS was reported in four studies. Pooled results showed that, compared to the nonmetformin group, the prolonged OS (HR = 0.72, p = 0.001), CSS (HR = 0.81, p = 0.001), and PFS (HR = 0.70, p = 0.008) of the experimental group may be associated with the exposure to metformin.

CONCLUSION

Metformin may have a beneficial effect on the prognosis of GC patients with T2DM.

Metformin: A Promising Antidiabetic Medication for Cancer Treatment

Metformin is a widely used drug in patients with type 2 diabetes mellitus. Metformin inhibits hepatic gluconeogenesis and increases glucose utilization in peripheral tissues. In recent years, several studies have shown that metformin is a potential therapeutic agent against cancer, alone or combined with other anticancer treatments. Metformin mainly activates the AMPK complex and regulates intracellular energy status, inhibiting the mitochondrial respiratory chain complex I and reducing the production of reactive oxygen species. Other anticancer targets of metformin are specific transcription factors inhibiting cell proliferation, promoting apoptosis and reducing drug resistance. In addition, metformin modulates tumor cells' response to anticancer treatments, favoring the activity of T cells. In diabetic patients, metformin reduces the occurrence of cancer and improves the prognosis and efficacy of anticancer treatments. In this review, we provided a comprehensive perspective of metformin as an anticancer drug.

Metabolism heterogeneity in melanoma fuels deactivation of immunotherapy: Predict before protect

Malignant melanoma is widely acknowledged as the most lethal skin malignancy. The metabolic reprogramming in melanoma leads to alterations in glycolysis and oxidative phosphorylation (OXPHOS), forming a hypoxic, glucose-deficient and acidic tumor microenvironment which inhibits the function of immune cells, resulting in a low response rate to immunotherapy. Therefore, improving the tumor microenvironment by regulating the metabolism can be used to improve the efficacy of immunotherapy. However, the tumor microenvironment (TME) and the metabolism of malignant melanoma are highly heterogeneous. Therefore, understanding and predicting how melanoma regulates metabolism is important to improve the local immune microenvironment of the tumor, and metabolism regulators are expected to increase treatment efficacy in combination with immunotherapy. This article reviews the energy metabolism in melanoma and its regulation and prediction, the integration of immunotherapy and metabolism regulators, and provides a comprehensive overview of future research focal points in this field and their potential application in clinical treatment.

Effects of metabolic cancer therapy on tumor microenvironment

Targeting tumor metabolism for cancer therapy is an old strategy. In fact, historically the first effective cancer therapeutics were directed at nucleotide metabolism. The spectrum of metabolic drugs considered in cancer increases rapidly - clinical trials are in progress for agents directed at glycolysis, oxidative phosphorylation, glutaminolysis and several others. These pathways are essential for cancer cell proliferation and redox homeostasis, but are also required, to various degrees, in other cell types present in the tumor microenvironment, including immune cells, endothelial cells and fibroblasts. How metabolism-targeted treatments impact these tumor-associated cell types is not fully understood, even though their response may co-determine the overall effectivity of therapy. Indeed, the metabolic dependencies of stromal cells have been overlooked for a long time. Therefore, it is important that metabolic therapy is considered in the context of tumor microenvironment, as understanding the metabolic vulnerabilities of both cancer and stromal cells can guide new treatment concepts and help better understand treatment resistance. In this review we discuss recent findings covering the impact of metabolic interventions on cellular components of the tumor microenvironment and their implications for metabolic cancer therapy.

Metformin enhances the antitumor activity of oncolytic herpes simplex virus HF10 (canerpaturev) in a pancreatic cell cancer subcutaneous model

Oncolytic virus (OV) therapy is a promising cancer immunotherapy, especially for cold tumors by inducing the direct lysis of cancer cells and initiation of potent antitumor response. Canerpaturev (C-REV) is an attenuated oncolytic herpes simplex virus-1, which demonstrated a potent antitumor effect in various preclinical models when used either alone or combined. Metformin is a commonly prescribed antidiabetic drug that demonstrated a potent immune modulator effect and antitumor response. We combined C-REV with metformin in a low immunogenic bilateral murine tumor model to enhance C-REV's antitumor efficacy. In vitro, metformin does not enhance the C-REV cell cytotoxic effect. However, in in vivo model, intratumoral administration of C-REV with the systemic administration of metformin led to synergistic antitumor effect on both sides of tumor and prolonged survival. Moreover, combination therapy increased the effector CD44⁺ CD8⁺ PD1^- subset and decreased the proportion of terminally-differentiated CD103⁺ KLRG-1⁺ T-regulatory cells on both sides of tumor. Interestingly, combination therapy efficiently modulates conventional dendritic cells type-1 (cDC1) on tumors, and tumor-drained lymph nodes. Our findings suggest that combination of C-REV and metformin enhances systemic antitumor immunity. This study may provide insights into the mechanism of action of OV therapy plus metformin combination against various tumor models.

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.

The Tumor Microenvironment Reprograms Immune Cells

Tumor tissue comprises a highly complex network of diverse cell types. The tumor microenvironment (TME) can be mainly subdivided into cancer cells and stromal cell compartments, the latter include different types of immune cells, fibroblasts, endothelial cells, and pericytes. Tumor cells reprogram immune cells and other stromal cells in the TME to constrain their antitumor capacity by creating an immunosuppressive milieu and metabolism competition. Moreover, the reprogramming effect on immune cells is localized not only in the tumor but also at the systemic level. With wide application of single-cell sequencing technology, tumor-specific characteristics of immune cells and other stromal cells in the TME have been dissected. In this review, we mainly focus on how tumor cells reprogram immune cells both within the TME and peripheral blood. This information can further help us to improve the efficiency of current immunotherapy as well as bring up new ideas to combat cancer.

The crosstalk within the breast tumor microenvironment in type II diabetes: Implications for cancer disparities

Obesity-driven (type 2) diabetes (T2D), the most common metabolic disorder, both increases the incidence of all molecular subtypes of breast cancer and decreases survival in postmenopausal women. Despite this clear link, T2D and the associated dysfunction of diverse tissues is often not considered during the standard of care practices in oncology and, moreover, is treated as exclusion criteria for many emerging clinical trials. These guidelines have caused the biological mechanisms that associate T2D and breast cancer to be understudied. Recently, it has been illustrated that the breast tumor microenvironment (TME) composition and architecture, specifically the surrounding cellular and extracellular structures, dictate tumor progression and are directly relevant for clinical outcomes. In addition to the epithelial cancer cell fraction, the breast TME is predominantly made up of cancer-associated fibroblasts, adipocytes, and is often infiltrated by immune cells. During T2D, signal transduction among these cell types is aberrant, resulting in a dysfunctional breast TME that communicates with nearby cancer cells to promote oncogenic processes, cancer stem-like cell formation, pro-metastatic behavior and increase the risk of recurrence. As these cells are non-malignant, despite their signaling abnormalities, data concerning their function is never captured in DNA mutational databases, thus we have limited insight into mechanism from publicly available datasets. We suggest that abnormal adipocyte and immune cell exhaustion within the breast TME in patients with obesity and metabolic disease may elicit greater transcriptional plasticity and cellular heterogeneity within the expanding population of malignant epithelial cells, compared to the breast TME of a non-obese, metabolically normal patient. These challenges are particularly relevant to cancer disparities settings where the fraction of patients seen within the breast medical oncology practice also present with co-morbid obesity and metabolic disease. Within this review, we characterize the changes to the breast TME during T2D and raise urgent molecular, cellular and translational questions that warrant further study, considering the growing prevalence of T2D worldwide.

Highly active selenium nanotherapeutics combined with metformin to achieve synergistic sensitizing effect on NK cells for osteosarcoma therapy

NK cells-based cancer therapy combined with chemotherapeutic drugs for the treatment of tumors can enhance the immunosensitivity of NK cells, increase the expression of NK cell receptors, and eventually boost the killing effect of NK cells on cancer cells. Selenium (Se) with different chemical structures can be metabolized into selenoproteins to regulate tumor and immune cells' fate and functions. Herein, we found that, functionalized Se nanoparticles (SeNPs) combining with metformin (met) could amply the immunotherapeutic effects of NK92 cells against osteosarcoma cancer. The results revealed that TW80-SeNPs combined with met had the optimum performance on NK92 cells for HepG2 cells, owing to the increased ROS in HepG2 cells and the augmented expression of cell surface receptor proteins ULBP-3/4, PD-L1, MICA, and NK92 cell surface receptor proteins PD-1 and FasL. Additionally, TW80-SeNPs were gradually metabolized into selenoproteins (Gpx4 and TR1) into human osteosarcoma MG63 cells to reinforce the anticancer effect of NK92 cells by regulating the redox balance in the tumor microenvironment. This study provides a therapeutic approach in treating cancer itself or diabetes coupled with cancer. Moreover, it provides a multidrug strategy to improve immune cell function in practical applications, especially for synergistic immunotherapy of osteosarcoma.

The Glycosylation of Immune Checkpoints and Their Applications in Oncology

Tumor therapies have entered the immunotherapy era. Immune checkpoint inhibitors have achieved tremendous success, with some patients achieving long-term tumor control. Tumors, on the other hand, can still accomplish immune evasion, which is aided by immune checkpoints. The majority of immune checkpoints are membrane glycoproteins, and abnormal tumor glycosylation may alter how the immune system perceives tumors, affecting the body's anti-tumor immunity. Furthermore, RNA can also be glycosylated, and GlycoRNA is important to the immune system. Glycosylation has emerged as a new hallmark of tumors, with glycosylation being considered a potential therapeutic approach. The glycosylation modification of immune checkpoints and the most recent advances in glycosylation-targeted immunotherapy are discussed in this review.

Overcoming current challenges to T-cell receptor therapy via metabolic targeting to increase antitumor efficacy, durability, and tolerability

The antitumor potential of personalized immunotherapy, including adoptive T-cell therapy, has been shown in both preclinical and clinical studies. Combining cell therapy with targeted metabolic interventions can further enhance therapeutic outcomes in terms of magnitude and durability. The ability of a T cell receptor to recognize peptides derived from tumor neoantigens allows for a robust yet specific response against cancer cells while sparing healthy tissue. However, there exist challenges to adoptive T cell therapy such as a suppressive tumor milieu, the fitness and survival of transferred cells, and tumor escape, all of which can be targeted to further enhance the antitumor potential of T cell receptor-engineered T cell (TCR-T) therapy. Here, we explore current strategies involving metabolic reprogramming of both the tumor microenvironment and the cell product, which can lead to increased T cell proliferation, survival, and anti-tumor cytotoxicity. In addition, we highlight potential metabolic pathways and targets which can be leveraged to improve engraftment of transferred cells and obviate the need for lymphodepletion, while minimizing off-target effects. Metabolic signaling is delicately balanced, and we demonstrate the need for thoughtful and precise interventions that are tailored for the unique characteristics of each tumor. Through improved understanding of the interplay between immunometabolism, tumor resistance, and T cell signaling, we can improve current treatment regimens and open the door to potential synergistic combinations.

Metformin as a Potential Antitumor Agent

Some recent findings suggest that metformin, an oral antidiabetic drug, may have antitumor properties. Studies have shown that metformin can alter cell metabolism, both tumor and immune cells, which can greatly influence disease outcome. In this review, we discuss the potential mechanisms in which metformin can directly induce apoptosis of tumor cells as well as mechanisms in which metformin can elicit or enhance antitumor immune response.

The effect of metformin or dipeptidyl peptidase 4 inhibitors on clinical outcomes in metastatic non-small cell lung cancer treated with immune checkpoint inhibitors

BACKGROUND

Preclinical data have shown the immunomodulatory effects of metformin and dipeptidyl peptidase 4 (DPP4) inhibitors in patients with diabetes. However, its clinical impact remains unclear in lung cancer.

METHODS

Between 2017 and 2021, 466 patients received ICI monotherapy. Patients were categorized into concurrent (MET; metformin or combination of metformin and DPP4 inhibitor) and without concomitant (NMET; nonmetformin/DPP4 inhibitors) administration of metformin and DPP4 inhibitors groups at least 8 weeks before and during ICI therapy. The primary objectives were the objective response rate (ORR) and progression-free survival (PFS). The second objective was to evaluate the overall survival (OS) and the occurrence of immune-related adverse events (irAEs).

RESULTS

Among 466 patients, 89 (19.0%) and 377 (81%) were categorized into the MET and NMET groups, respectively. MET group had a significantly higher ORR (MET group: 24.7% vs. NMET group: 14.8%, p = 0.025) and longer PFS than those in the NMET group (MET group 5.1 month vs. NMET group 2.8 months, p = 0.018). After patients were stratified based on the prior line of therapy and PD L1 expression status, the PFS of the second-line therapy and PD L1 ≥50 was significantly higher in the MET than in the NMET group. The proportion of patients experiencing all-grade irAEs was numerically higher in the MET group (19.1%) than in the NMET group (14.3%), without statistical significance (p = 0.382).

CONCLUSIONS

Concurrent use of metformin and DPP4 inhibitors with ICIs significantly improved the clinical outcomes without increasing the incidence of irAEs in NSCLC.

Metformin increases natural killer cell functions in head and neck squamous cell carcinoma through CXCL1 inhibition

BACKGROUND

Metformin slows tumor growth and progression in vitro, and in combination with chemoradiotherapy, resulted in high overall survival in patients with head and neck cancer squamous cell carcinoma (HNSCC) in our phase 1 clinical trial (NCT02325401). Metformin is also postulated to activate an antitumor immune response. Here, we investigate immunologic effects of metformin on natural killer (NK) and natural killer T cells, including results from two phase I open-label studies in patients with HNSCC treated with metformin (NCT02325401, NCT02083692).

METHODS

Peripheral blood was collected before and after metformin treatment or from newly diagnosed patients with HNSCC. Peripheral immune cell phenotypes were evaluated using flow cytometry, cytokine expression by ELISA and/or IsoLight, and NK cell-mediated cytotoxicity was determined with a flow-based NK cell cytotoxicity assay (NKCA). Patient tumor immune infiltration before and after metformin treatment was analyzed with immunofluorescence. NK cells were treated with either vehicle or metformin and analyzed by RNA sequencing (RNA-seq). NK cells were then treated with inhibitors of significant pathways determined by RNA-seq and analyzed by NKCA, ELISA, and western blot analyses.

RESULTS

Increased peripheral NK cell activated populations were observed in patients treated with metformin. NK cell tumor infiltration was enhanced in patients with HNSCC treated with metformin preoperatively. Metformin increased antitumorigenic cytokines ex vivo, including significant increases in perforin. Metformin increased HNSCC NK cell cytotoxicity and inhibited the CXCL1 pathway while stimulating the STAT1 pathway within HNSCC NK cells. Exogenous CXCL1 prevented metformin-enhanced NK cell-mediated cytotoxicity. Metformin-mediated NK cell cytotoxicity was found to be AMP-activated protein kinase independent, but dependent on both mechanistic target of rapamycin and pSTAT1.

CONCLUSIONS

Our data identifies a new role for metformin-mediated immune antitumorigenic function through NK cell-mediated cytotoxicity and downregulation of CXCL1 in HNSCC. These findings will inform future immunomodulating therapies in HNSCC.

Therapeutic targeting of regulatory T cells in cancer

The success of immunotherapy in oncology underscores the vital role of the immune system in cancer development. Regulatory T cells (Tregs) maintain a fine balance between autoimmunity and immune suppression. They have multiple roles in the tumor microenvironment (TME) but act particularly in suppressing T cell activation. This review focuses on the detrimental and sometimes beneficial roles of Tregs in tumors, our current understanding of recruitment and stabilization of Tregs within the TME, and current Treg-targeted therapeutics. Research identifying subpopulations of Tregs and their respective functions and interactions within the complex networks of the TME will be crucial to develop the next generation of immunotherapies. Through these advances, Treg-targeted immunotherapy could have important implications for the future of oncology.

Identification of patient characteristics associated with survival benefit from metformin treatment in patients with stage I non-small cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) continues to be a major cause of cancer deaths. Previous investigation has suggested that metformin use can contribute to improved outcomes in NSCLC patients. However, this association is not uniform in all analyzed cohorts, implying that patient characteristics might lead to disparate results. Identification of patient characteristics that affect the association of metformin use with clinical benefit might clarify the drug's effect on lung cancer outcomes and lead to more rational design of clinical trials of metformin's utility as an intervention. In this study, we examined the association of metformin use with long-term mortality benefit in patients with NSCLC and the possible modulation of this benefit by body mass index (BMI) and smoking status, controlling for other clinical covariates.

METHODS

This was a retrospective cohort study in which we analyzed data from the Veterans Affairs (VA) Tumor Registry in the United States. Data from all patients with stage I NSCLC from 2000 to 2016 were extracted from a national database, the Corporate Data Warehouse that captures data from all patients, primarily male, who underwent treatment through the VA health system in the United States. Metformin use was measured according to metformin prescriptions dispensed to patients in the VA health system. The association of metformin use with overall survival (OS) after diagnosis of stage I NSCLC was examined. Patients were further stratified according to BMI and smoking status (previous vs current) to examine the association of metformin use with OS across these strata.

RESULTS

Metformin use was associated with improved survival in patients with stage I NSCLC (average hazard ratio, 0.82; P < .001). An interaction between the effect of metformin use and BMI on OS was observed (χ2 = 3268.42; P < .001) with a greater benefit of metformin use observed in patients as BMI increased. Similarly, an interaction between smoking status and metformin use on OS was also observed (χ2 = 2997.05; P < .001) with a greater benefit of metformin use observed in previous smokers compared with current smokers.

CONCLUSIONS

In this large retrospective study, we showed that a survival benefit is enjoyed by users of metformin in a robust stage I NSCLC patient population treated in the VA health system. Metformin use was associated with an 18% improved OS. This association was stronger in patients with a higher BMI and in previous smokers. These observations deserve further mechanistic study and can help rational design of clinical trials with metformin in patients with lung cancer.

Fatty acid metabolism in T-cell function and differentiation

Immunometabolism has recently emerged as a field of study examining the intersection between immunology and metabolism. Studies in this area have yielded new findings on the roles of a diverse range of metabolic pathways and metabolites, which have been found to control many aspects of T-cell biology, including cell differentiation, function and fate. A particularly important finding has been the discovery that to meet the energy requirements associated with their proliferation, activation and specific functions, T cells switch their metabolic signatures during differentiation. For example, whereas the induction of de novo fatty acid biosynthesis and fatty acid uptake programs are required for antigen-stimulation-induced proliferation and differentiation of effector T cells, fatty acid catabolism via β-oxidation is essential for the generation of memory T cells and the differentiation of regulatory T cells. In this review, we discuss recent advances in our understanding of the metabolism in different stages of T cells and how fatty acid metabolism in these cells controls their specific functions.

The role of cancer-associated mesothelial cells in the progression and therapy of ovarian cancer

Ovarian cancer is currently one of the most common malignant tumors in females with poor survival rates around the world, killing about 200,000 women each year. Although great progress has been made in treatment, most patients receiving first-line therapy experience tumor recurrence. The tumor microenvironment plays an important role in regulating the progression and prognosis of ovarian cancer. Cancer-associated mesothelial cells are the main cell population in the tumor microenvironment, which affect the progression, prognosis and chemical resistance of ovarian cancer. Cancer-associated mesothelial cells can also interact with other microenvironmental components, such as exosomes, macrophages, and adipocytes. Some studies have developed drugs targeting cancer-associated mesothelial cells in ovarian cancer to evaluate the therapeutic efficiency. In this review we highlighted the key role of cancer-associated mesothelial cells in the progression and prognosis of ovarian cancer. We also described the progress of cancer-associated mesothelial cells targeted therapy for ovarian cancer. Continued insight into the role of cancer-associated mesothelial cells in ovarian cancer will potentially contribute to the development of new and effective therapeutic regiments.

A ROS/Akt/NF-κB Signaling Cascade Mediates Epidermal Growth Factor-Induced Epithelial-Mesenchymal Transition and Invasion in Human Breast Cancer Cells

BACKGROUND

As one of the most widely used anti-diabetic drugs for type II diabetes, metformin has been shown to exhibit anti-cancer activity in recent years. Epidermal growth factor (EGF) and its receptor, EGFR, play important roles in cancer metastasis in various tumors, including breast cancer. Epithelial-mesenchymal transition (EMT) is a critical process for cancer invasion and metastasis. In this study, we use EGF as a metastatic inducer to investigate the effect of metformin on cancer cell migration, invasion and EMT.

METHODS

Human breast cancer MCF-7 cells were exposed to EGF with or without metformin or N-acetyl cysteine (NAC). The effects of metformin on breast cancer cell proliferation were analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The production of reactive oxygen species (ROS) was tested using 2,7-dichlorodihydrofluorecein diacetate (DCFH-DA). The migratory and invasive abilities of tumor cells were analyzed using wound healing assay and transwell invasion assay, respectively. The expressions of E-cadherin, N-cadherin and Snail were tested using real-time quantitative polymerase chain reaction (qRT-PCR) and western blotting at mRNA and protein levels. The activation of protein kinase B (Akt) and nuclear factor kappa B (NF-κB) were measured by western blotting.

RESULTS

Our results showed that metformin inhibited breast cancer cell proliferation in a dose-dependent manner with or without EGF. EGF-induced alterations in cell morphology that are characteristic of EMT were reversed by metformin. Metformin also inhibited the EGF-modulated expression of E-cadherin, N-cadherin and Snail and further suppressed cell invasion and migration. In addition, metformin suppressed EGF-induced phosphorylation of Akt and NF-κB. ROS is involved in EGF-induced cancer invasion and activation of phosphatidylinositol 3-kinase (PI3K)/Akt/NF-κB pathway.

CONCLUSION

Taken together, these data indicate that metformin suppresses EGF-induced breast cancer cell migration, invasion and EMT through the inhibition of the PI3K/Akt/NF-κB pathway. These results provide a novel mechanism to explain the role of metformin as a potent anti-metastatic agent in breast cancer cells.

Mechanisms of resistance to immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) are effective for various types of cancer, and their application has led to paradigm shifts in cancer treatment. While many patients can obtain clinical benefits from ICI treatment, a large number of patients are primarily resistant to such treatment or acquire resistance after an initial response. Thus, elucidating the resistance mechanisms is warranted to improve the clinical outcomes of ICI treatment. ICIs exert their antitumor effects by activating T cells in the tumor microenvironment. There are various resistance mechanisms, such as insufficient antigen recognition by T cells, impaired T-cell migration and/or infiltration, and reduced T-cell cytotoxicity, most of which are related to the T-cell activation process. Thus, we classify them into three main mechanisms: resistance mechanisms related to antigen recognition, T-cell migration and/or infiltration, and effector functions of T cells. In this review, we summarize these mechanisms of resistance to ICIs related to the T-cell activation process and progress in the development of novel therapies that can overcome resistance.

The Role of Immunotherapy in Pancreatic Cancer

Pancreatic adenocarcinoma remains one of the most lethal cancers globally, with a significant need for improved therapeutic options. While the recent breakthroughs of immunotherapy through checkpoint inhibitors have dramatically changed treatment paradigms in other malignancies based on considerable survival benefits, this is not so for pancreatic cancer. Chemotherapies with modest benefits are still the cornerstone of advanced pancreatic cancer treatment. Pancreatic cancers are inherently immune-cold tumors and have been largely refractory to immunotherapies in clinical trials. Understanding and overcoming the current failures of immunotherapy through elucidating resistance mechanisms and developing novel therapeutic approaches are essential to harnessing the potential durable benefits of immune-modulating therapy in pancreatic cancer patients.

Immune State Conversion of the Mesenteric Lymph Node in a Mouse Breast Cancer Model

Secondary lymphoid tissues, such as the spleen and lymph nodes (LNs), contribute to breast cancer development and metastasis in both anti- and pro-tumoral directions. Although secondary lymphoid tissues have been extensively studied, very little is known about the immune conversion in mesenteric LNs (mLNs) during breast cancer development. Here, we demonstrate inflammatory immune conversion of mLNs in a metastatic 4T1 breast cancer model. Splenic T cells were significantly decreased and continuously suppressed IFN-γ production during tumor development, while myeloid-derived suppressor cells (MDSCs) were dramatically enriched. However, T cell numbers in the mLN did not decrease, and the MDSCs only moderately increased. T cells in the mLN exhibited conversion from a pro-inflammatory state with high IFN-γ expression to an anti-inflammatory state with high expression of IL-4 and IL-10 in early- to late-stages of breast cancer development. Interestingly, increased migration of CD103+CD11b+ dendritic cells (DCs) into the mLN, along with increased (1→3)-β-D-glucan levels in serum, was observed even in late-stage breast cancer. This suggests that CD103+CD11b+ DCs could prime cancer-reactive T cells. Together, the data indicate that the mLN is an important lymphoid tissue contributing to breast cancer development.

Liposomal oxaliplatin prodrugs loaded with metformin potentiate immunotherapy for colorectal cancer

Tumor hypoxia is confirmed to be associated with the formation of tumor immunosuppression, a general feature of solid tumors, and thus attenuates the effectiveness of various cancer therapies in clinic. We herein develop a tumor microenvironment (TME) modulating liposomal nanomedicine by encapsulating metformin with amphiphilic oxaliplatin prodrug constructed liposomes to potentiate cancer immunotherapy. While metformin could regulate metabolisms of tumor cells to reduce their oxygen consumption and relieve tumor hypoxia, oxaliplatin is a chemotherapy drug that induces immunogenic cell death (ICD). The obtained met-oxa(IV)-liposome upon intravenous injection effectively attenuates tumor hypoxia and induce ICD of cancer cells, thereby collectively suppresses the growth of murine colorectal tumors by eliciting potent antitumor immunity and reversing the immunosuppressive TME. As the result, the treatment with met-oxa(IV)-liposome effectively potentiates the immune checkpoint blockade (ICB) therapy against murine colorectal tumors. This liposomal nanomedicine is highlighted to be a TME modulating liposomal nanomedicine with high potency in suppressing tumor growth, particularly promising in synergizing with ICB therapy by boosting antitumor immune responses.