Metformin transiently inhibits colorectal cancer cell proliferation as a result of either AMPK activation or increased ROS production. Sci Rep. 2017;7:15992. [PMID: 29167573 PMCID: PMC5700100 DOI: 10.1038/s41598-017-16149-z]

Non-coding RNAs as potential targets in metformin therapy for cancer

Metformin, a widely used oral hypoglycemic drug, has emerged as a potential therapeutic agent for cancer treatment. While initially known for its role in managing diabetes, accumulating evidence suggests that metformin exhibits anticancer properties through various mechanisms. Several cellular or animal experiments have attempted to elucidate the role of non-coding RNA molecules, including microRNAs and long non-coding RNAs, in mediating the anticancer effects of metformin. The present review summarized the current understanding of the mechanisms by which non-coding RNAs modulate the response to metformin in cancer cells. The regulatory roles of non-coding RNAs, particularly miRNAs, in key cellular processes such as cell proliferation, cell death, angiogenesis, metabolism and epigenetics, and how metformin affects these processes are discussed. This review also highlights the role of lncRNAs in cancer types such as lung adenocarcinoma, breast cancer, and renal cancer, and points out the need for further exploration of the mechanisms by which metformin regulates lncRNAs. In addition, the present review explores the potential advantages of metformin-based therapies over direct delivery of ncRNAs, and this review highlights the mechanisms of non-coding RNA regulation when metformin is combined with other therapies. Overall, the present review provides insights into the molecular mechanisms underlying the anticancer effects of metformin mediated by non-coding RNAs, offering novel opportunities for the development of personalized treatment strategies in cancer patients.

Metformin's role in lowering colorectal cancer risk among individuals with diabetes from the Southern Community Cohort Study

BACKGROUND

Metformin, utilized to manage hyperglycemia, has been linked to a reduced risk of colorectal cancer (CRC) among individuals with diabetes. However, evidence is lacking for non-Hispanic Black individuals and those with lower socioeconomic status (SES), who face elevated risk for both diabetes and CRC. In this study, we investigated the association between metformin use and incident CRC risk within the Southern Community Cohort Study (SCCS), a racially- and SES-diverse prospective cohort.

METHODS

Participants reported their diabetes diagnosis and medications, including metformin, upon enrollment (2002-2009) and during follow-up surveys approximately every five years. Incident cases of CRC were identified through state cancer registries and the National Death Index. Proportional hazards models were employed to explore the relationship between metformin use and CRC risk, adjusted for cancer risk factors.

RESULTS

A total of 25,992 participants with diabetes were included in the analysis, among whom 10,095 were taking metformin. Of these participants, 76% identified as non-Hispanic Black, and 60% reported household incomes <$15,000/year. Metformin use was associated with a significantly lower CRC risk (HR [95% CI]: 0.71 [0.55-0.93]), with consistent results for both colon (0.80 [0.59-1.07]) and rectal cancers (0.49 [0.28-0.86]). The protective association appeared to be stronger among non-Hispanic White individuals (0.51 [0.31-0.85]) compared to non-Hispanic Black participants (0.80 [0.59-1.08], p-interaction =.13). Additionally, a protective association was observed among obese individuals (BMI ≥30 kg/m2, 0.59 [0.43-0.82] but not among non-obese participants (0.99 [0.65-1.51], p-interaction =.05) CONCLUSION: Our findings indicate that metformin use is associated with a reduced risk of CRC in individuals with diabetes, including among those from predominantly low SES backgrounds. These results support previous epidemiological findings, and demonstrate that the protective association for metformin in relation to incident CRC likely generalizes to populations with higher underlying risk.

Metformin as anticancer agent and adjuvant in cancer combination therapy: Current progress and future prospect

Metformin, as the preferred antihyperglycemic drug for type 2 diabetes, has been found to have a significant effect in inhibiting tumor growth in recent years. However, metformin alone in cancer treatment has the disadvantages of high dose concentrations and few targeted cancer types. Increasing studies have confirmed that metformin can be used in combination with conventional anticancer therapy to obtain more promising clinical benefits, which is expected to be rapidly transformed and applied in clinic. Some combination therapy strategies including metformin combined with chemotherapy, radiotherapy, targeted therapy and immunotherapy have been proven to have more significant antitumor effects and longer survival time than monotherapy. In this review, we summarize the synergistic antitumor effects and mechanisms of metformin in combination with other current conventional anticancer therapies. In addition, we update the research progress and the latest prospect of the metformin-combined application in the cancer treatment. This work could provide more evidence and future direction for the clinical application of metformin in antitumor.

Metformin: From Diabetes to Cancer-Unveiling Molecular Mechanisms and Therapeutic Strategies

Metformin, a widely used anti-diabetic drug, has garnered attention for its potential in cancer management, particularly in breast and colorectal cancer. It is established that metformin reduces mitochondrial respiration, but its specific molecular targets within mitochondria vary. Proposed mechanisms include inhibiting mitochondrial respiratory chain Complex I and/or Complex IV, and mitochondrial glycerophosphate dehydrogenase, among others. These actions lead to cellular energy deficits, redox state changes, and several molecular changes that reduce hyperglycemia in type 2 diabetic patients. Clinical evidence supports metformin's role in cancer prevention in type 2 diabetes mellitus patients. Moreover, in these patients with breast and colorectal cancer, metformin consumption leads to an improvement in survival outcomes and prognosis. The synergistic effects of metformin with chemotherapy and immunotherapy highlights its potential as an adjunctive therapy for breast and colorectal cancer. However, nuanced findings underscore the need for further research and stratification by molecular subtype, particularly for breast cancer. This comprehensive review integrates metformin-related findings from epidemiological, clinical, and preclinical studies in breast and colorectal cancer. Here, we discuss current research addressed to define metformin's bioavailability and efficacy, exploring novel metformin-based compounds and drug delivery systems, including derivatives targeting mitochondria, combination therapies, and novel nanoformulations, showing enhanced anticancer effects.

Exosomes biogenesis was increased in metformin-treated human ovary cancer cells; possibly to mediate resistance

BACKGROUND

Exosomes derived from tumor cells contribute to the pathogenesis of cancers. Metformin, the most usually used drug for type 2 diabetes, has been frequently investigated for anticancer effects. Here, we examined whether metformin affects exosomes signaling in human ovary cancer cells in vitro.

METHODS

Human ovary cancer cells, including A2780 and Skov3 cells, were treated with metformin for either 24-48 h. Cell viability and caspase-3 activity were determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and colorimetric assays respectively. Oil-Red-O staining and in vitro, scratch assays were used to examine cellular toxicity and wound healing rate. After treatment with metformin, exosomes were isolated from cells and quantified by acetylcholinesterase (AChE) assay, Dynamic Light Scattering (DLS), and their markers. Genes related to exosomes signaling were analyzed by real-time PCR or western blotting.

RESULTS

Our results showed that metformin decreased the viability of both cells dose/time-dependently (P < 0.05). Metformin increased the activity of caspase-3 (P < 0.05) as well as the number of Oil-Red-O positive cells in both cell lines. In vitro scratch assay showed that the cell migration rate of metformin-treated cells was decreased (P < 0.05), whereas AChE activity of exosomes from metformin-treated cells was increased (P < 0.05). Concurrent with an increase in CD63 protein levels, expression of Alix, CD63, CD81, Lamp-2, and Rab27b up-regulated in treated cells (P < 0.05).

CONCLUSION

Results indicated that metformin had a cytotoxic effect on ovary cancer cells and enhanced exosome biogenesis and secretion.

Metformin: A Dual-Role Player in Cancer Treatment and Prevention

Cancer continues to pose a significant global health challenge, as evidenced by the increasing incidence rates and high mortality rates, despite the advancements made in chemotherapy. The emergence of chemoresistance further complicates the effectiveness of treatment. However, there is growing interest in the potential of metformin, a commonly prescribed drug for type 2 diabetes mellitus (T2DM), as an adjuvant chemotherapy agent in cancer treatment. Although the precise mechanism of action of metformin in cancer therapy is not fully understood, it has been found to have pleiotropic effects, including the modulation of metabolic pathways, reduction in inflammation, and the regulation of cellular proliferation. This comprehensive review examines the anticancer properties of metformin, drawing insights from various studies conducted in vitro and in vivo, as well as from clinical trials and observational research. This review discusses the mechanisms of action involving both insulin-dependent and independent pathways, shedding light on the potential of metformin as a therapeutic agent for different types of cancer. Despite promising findings, there are challenges that need to be addressed, such as conflicting outcomes in clinical trials, considerations regarding dosing, and the development of resistance. These challenges highlight the importance of further research to fully harness the therapeutic potential of metformin in cancer treatment. The aims of this review are to provide a contemporary understanding of the role of metformin in cancer therapy and identify areas for future exploration in the pursuit of effective anticancer strategies.

Metformin Treatment Leads to Increased HIV Transcription and Gene Expression through Increased CREB Phosphorylation and Recruitment to the HIV LTR Promoter

Antiretroviral therapy has effectively suppressed HIV infection and replication and prolonged the lifespan of HIV-infected individuals. In the meantime, various complications including type 2 diabetes associated with the long-term antiviral therapy have shown steady increases. Metformin has been the front-line anti-hyperglycemic drug of choice and the most widely prescribed medication for the treatment of type 2 diabetes. However, little is known about the effects of Metformin on HIV infection and replication. In this study, we showed that Metformin treatment enhanced HIV gene expression and transcription in HIV-transfected 293T and HIV-infected Jurkat and human PBMC. Moreover, we demonstrated that Metformin treatment resulted in increased CREB expression and phosphorylation, and TBP expression. Furthermore, we showed that Metformin treatment increased the recruitment of phosphorylated CREB and TBP to the HIV LTR promoter. Lastly, we showed that inhibition of CREB phosphorylation/activation significantly abrogated Metformin-enhanced HIV gene expression. Taken together, these results demonstrated that Metformin treatment increased HIV transcription, gene expression, and production through increased CREB phosphorylation and recruitment to the HIV LTR promoter. These findings may help design the clinical management plan and HIV cure strategy of using Metformin to treat type 2 diabetes, a comorbidity with an increasing prevalence, in people living with HIV.

Impact of Combination Therapy with Chemical Drugs and Megavoltage X-ray Exposure on Breast Cancer Stem Cells' Viability and Proliferation of MCF-7 and MDA-MB-231 Cell Lines

BACKGROUND

Breast Cancer (BC) is a serious malignancy among women. However, chemotherapy is an important tool for cancer treatments, but the long-term use of chemotherapy drugs may lead to drug resistance and tumor recurrence. Since Breast Cancer Stem Cells (BCSCs) can be the main factor to induce BC treatment resistance and recurrence, investigation of BCSCs signaling pathways can be an effective modality to enhance cancer treatment efficiency.

OBJECTIVE

In this study, the effect of metformin, SB203580, and takinib alone or in combination with radiotherapy on MCF-7 and MDA-MB-231 breast cancer cell lines was evaluated.

METHODS

MCF-7 and MDA-MB-231 breast cancer cell lines were treated with metformin, SB203580, and takinib for 24 or 48 hours, followed by X-ray exposure. The MTT assay and flow cytometry analysis were performed to assess cell growth inhibition and cellular death, CXCr4 expression, and BCSCs, respectively.

RESULTS

The results showed the combination of takinib/SB203580 with radiotherapy to remarkably reduce the CXCR4 expression and BCSCs levels in the MCF-7 cell line. Also, the concurrent administration of takinib/metformin/radiotherapy significantly reduced BCSCs and CXCR4 metastatic markers in the MDA-MB- 231 cells. Since the MAPK signaling pathway has an important role in inducing drug resistance and cell proliferation, the use of SB203580 as an inhibitor of p38 MAPK can improve breast cancer treatment. Furthermore, metformin and ionizing radiation by suppression of the mTOR signaling pathway can control AMPK activation and cellular proliferation.

CONCLUSION

Anti-cancer and cytotoxic effects of metformin can be effective in this strategy. In conclusion, the combination of conventional chemotherapeutic drugs, including SB203580, metformin, and takinib with X-ray exposure can be a new approach to diminish the drug resistance of breast cancer.

Combination of metformin/efavirenz/fluoxetine exhibits profound anticancer activity via a cancer cell-specific ROS amplification

The possible anticancer activity of combination (M + E + F) of metformin (M), efavirenz (E), and fluoxetine (F) was investigated in normal HDF cells and HCT116 human colon cancer cells. Metformin increased cellular FOXO3a, p-FOXO3a, AMPK, p-AMPK, and MnSOD levels in HDFs but not in HCT116 cells. Cellular ATP level was decreased only in HDFs by metformin. Metformin increased ROS level only in HCT116 cells. Transfection of si-FOXO3a into HCT116 reversed the metformin-induced cellular ROS induction, indicating that FOXO3a/MnSOD is the key regulator for cellular ROS level. Viability readout with M, E, and F alone decreased slightly, but the combination of three drugs dramatically decreased cell survival in HCT116, A549, and SK-Hep-1 cancer cells but not in HDF cells. ROS levels in HCT116 cells were massively increased by M + E + F combination, but not in HDF cells. Cell cycle analysis showed that of M + E + F combination caused cell death only in HCT116 cells. The combination of M + E + F reduced synergistically mitochondrial membrane potential and mitochondrial electron transport chain complex I and III activities in HCT116 cells when compared with individual treatments. Western blot analysis indicated that DNA damage, apoptosis, autophagy, and necroptosis-realated factors increased in M + E + F-treated HCT116 cells. Oral administration with M + E + F combination for 3 weeks caused dramatic reductions in tumor volume and weight in HCT116 xenograft model of nude mice when compared with untreated ones. Our results suggest that M + E + F have profound anticancer activity both in vitro and in vivo via a cancer cell-specific ROS amplification (CASRA) through ROS-induced DNA damage, apoptosis, autophagy, and necroptosis.

Targeted Inhibition of Hsp90 in Combination with Metformin Modulates Programmed Cell Death Pathways in A549 Lung Cancer Cells

The pathophysiology of lung cancer is dependent on the dysregulation in the apoptotic and autophagic pathways. The intricate link between apoptosis and autophagy through shared signaling pathways complicates our understanding of how lung cancer pathophysiology is regulated. As drug resistance is the primary reason behind treatment failure, it is crucial to understand how cancer cells may respond to different therapies and integrate crosstalk between apoptosis and autophagy in response to them, leading to cell death or survival. Thus, in this study, we have tried to evaluate the crosstalk between autophagy and apoptosis in A549 lung cancer cell line that could be modulated by employing a combination therapy of metformin (6 mM), an anti-diabetic drug, with gedunin (12 µM), an Hsp90 inhibitor, to provide insights into the development of new cancer therapeutics. Our results demonstrated that metformin and gedunin were cytotoxic to A549 lung cancer cells. Combination of metformin and gedunin generated ROS and promoted MMP loss and DNA damage. The combination further increased the expression of AMPKα1 and promoted the nuclear localization of AMPKα1/α2. The expression of Hsp90 was downregulated, further decreasing the expression of its clients, EGFR, PIK3CA, AKT1, and AKT3. Inhibition of the EGFR/PI3K/AKT pathway upregulated TP53 and inhibited autophagy. The combination was promoting nuclear localization of p53; however, some cytoplasmic signals were also detected. Further increase in the expression of caspase 9 and caspase 3 was observed. Thus, we concluded that the combination of metformin and gedunin upregulates apoptosis by inhibiting the EGFR/PI3K/AKT pathway and autophagy in A549 lung cancer cells.

The Role and Mechanism of Metformin in Inflammatory Diseases

Metformin is a classical drug used to treat type 2 diabetes. With the development of research on metformin, it has been found that metformin also has several advantages aside from its hypoglycemic effect, such as anti-inflammatory, anti-aging, anti-cancer, improving intestinal flora, and other effects. The prevention of inflammation is critical because chronic inflammation is associated with numerous diseases of considerable public health. Therefore, there has been growing interest in the role of metformin in treating various inflammatory conditions. However, the precise anti-inflammatory mechanisms of metformin were inconsistent in the reported studies. Thus, this review aims to summarize various currently known possible mechanisms of metformin involved in inflammatory diseases and provide references for the clinical application of metformin.

Salicylate induces AMPK and inhibits c-MYC to activate a NRF2/ARE/miR-34a/b/c cascade resulting in suppression of colorectal cancer metastasis

Aspirin and its active metabolite salicylate have emerged as promising agents for the chemoprevention of colorectal cancer (CRC). Moreover, aspirin suppresses the progression of established CRCs. However, the underlying molecular mechanisms are not completely understood. Here we found that salicylate induces the expression of the miR-34a and miR-34b/c genes, which encode tumor suppressive microRNAs, in a p53-independent manner. Salicylate activated AMPK, thereby activating NRF2, which directly induced miR-34a/b/c expression via ARE motifs. In addition, salicylate suppressed c-MYC, a known repressor of NRF2-mediated transactivation, via activating AMPK. The suppression of c-MYC by salicylate was necessary for NRF2-mediated activation of miR-34a/b/c. Inactivation of miR-34a/b/c largely abrogated the inhibitory effects of salicylate on migration, invasion and metastasis formation by CRC cells. In the future, aspirin and its derivates may be used therapeutically to activate miR-34a and miR-34b/c in tumors that have lost p53.

Repurposing drugs targeting metabolic diseases for cancer therapeutics

Hurdles in the identification of new drugs for cancer treatment have made drug repurposing an increasingly appealing alternative. The approach involves the use of old drugs for new therapeutic purposes. It is cost-effective and facilitates rapid clinical translation. Given that cancer is also considered a metabolic disease, drugs for metabolic disorders are being actively repurposed for cancer therapeutics. In this review, we discuss the repurposing of such drugs approved for two major metabolic diseases, diabetes and cardiovascular disease (CVD), which have shown potential as anti-cancer treatment. We also highlight the current understanding of the cancer signaling pathways that these drugs target.

Metformin is a metabolic modulator and radiosensitiser in rectal cancer

Resistance to neoadjuvant chemoradiation therapy, is a major challenge in the management of rectal cancer. Increasing evidence supports a role for altered energy metabolism in the resistance of tumours to anti-cancer therapy, suggesting that targeting tumour metabolism may have potential as a novel therapeutic strategy to boost treatment response. In this study, the impact of metformin on the radiosensitivity of colorectal cancer cells, and the potential mechanisms of action of metformin-mediated radiosensitisation were investigated. Metformin treatment was demonstrated to significantly radiosensitise both radiosensitive and radioresistant colorectal cancer cells in vitro. Transcriptomic and functional analysis demonstrated metformin-mediated alterations to energy metabolism, mitochondrial function, cell cycle distribution and progression, cell death and antioxidant levels in colorectal cancer cells. Using ex vivo models, metformin treatment significantly inhibited oxidative phosphorylation and glycolysis in treatment naïve rectal cancer biopsies, without affecting the real-time metabolic profile of non-cancer rectal tissue. Importantly, metformin treatment differentially altered the protein secretome of rectal cancer tissue when compared to non-cancer rectal tissue. Together these data highlight the potential utility of metformin as an anti-metabolic radiosensitiser in rectal cancer.

Metformin and thymoquinone co-treatment enhance 5-fluorouracil cytotoxicity by suppressing the PI3K/mTOR/HIF1α pathway and increasing oxidative stress in colon cancer cells

This study investigated the chemotherapeutic effects of 5-fluorouracil (5-FU), metformin (Met), and/or thymoquinone (TQ) single/dual/triple therapies in the HT29, SW480 and SW620 colon cancer (CRC) cell lines. Cell cycle/apoptosis were measured by flow cytometry. The gene and protein expression of apoptosis (PCNA/survivin/BAX/Cytochrome-C/Caspase-3) and cell cycle (CCND1/CCND3/p21/p27) molecules, the PI3K/mTOR/HIF1α oncogenic pathway, and glycolysis regulatory enzymes were measured by quantitative-PCR and Western blot. Markers of oxidative stress were also measured by colorimetric assays. Although all treatments induced anti-cancer effects related to cell cycle arrest and apoptosis, the triple therapy showed the highest pro-apoptotic actions that coincided with the lowest expression of CCND1/CCND3/PCNA/survivin and the maximal increases in p21/p27/BAX/Cytochrome-C/Caspase-3 in all cell lines. The triple therapy also revealed the best suppression of the PI3K/mTOR/HIF1α pathway by increasing its endogenous inhibitors (PTEN/AMPKα) in all cell lines. Moreover, the lowest expression of lactate dehydrogenase and pyruvate dehydrogenase kinase-1 with the highest expression of pyruvate dehydrogenase were seen with the triple therapy, which also showed the highest increases in oxidative stress markers (ROS/RNS/MDA/protein carbonyl groups) alongside the lowest antioxidant levels (GSH/CAT) in all cell lines. In conclusion, this is the first study to reveal enhanced anti-cancer effects for metformin/thymoquinone in CRC that were superior to all monotherapies and the other dual therapies. However, the triple therapy approach showed the best tumoricidal actions related to cell cycle arrest and apoptosis in all cell lines, possibly by enhancing oxidative glycolysis and augmenting oxidative stress through stronger modulation of the PI3K/mTOR/HIF1α oncogenic network.

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 and Cancer: Solutions to a Real-World Evidence Failure

The quest to repurpose metformin, an antidiabetes drug, as an agent for cancer prevention and treatment, which began in 2005 with an observational study that reported a reduction in cancer incidence among metformin users, generated extensive experimental, observational, and clinical research. Experimental studies revealed that metformin has anticancer effects via various pathways, potentially inhibiting cancer cell proliferation. Concurrently, multiple nonrandomized observational studies reported remarkable reductions in cancer incidence and outcomes with metformin use. However, these studies were shown, in 2012, to be affected by time-related biases, such as immortal time bias, which tend to greatly exaggerate the benefit of a drug. The observational studies that avoided these biases did not find an association. Subsequently, the randomized trials of metformin for the treatment of type 2 diabetes and as adjuvant therapy for the treatment of various cancers, advanced or metastatic, did not find reductions in cancer incidence or outcomes. Most recently, the largest phase 3 randomized trial of metformin as adjuvant therapy for breast cancer, which enrolled 3,649 women with a 5-year follow-up, found no benefit for disease-free survival or overall survival with metformin. This major failure of observational real-world evidence studies in correctly assessing the effects of metformin on cancer incidence and outcomes was caused by preventable biases which, surprisingly, are still prominent in 2022. Rigorous approaches for observational studies that emulate randomized trials, such as the incident and prevalent new-user designs along with propensity scores, avoid these biases and can provide more accurate real-world evidence for the repurposing of drugs such as metformin.

Counteracting Colon Cancer by Inhibiting Mitochondrial Respiration and Glycolysis with a Selective PKCδ Activator

Metabolic reprogramming is a central hub in tumor development and progression. Therefore, several efforts have been developed to find improved therapeutic approaches targeting cancer cell metabolism. Recently, we identified the 7α-acetoxy-6β-benzoyloxy-12-O-benzoylroyleanone (Roy-Bz) as a PKCδ-selective activator with potent anti-proliferative activity in colon cancer by stimulating a PKCδ-dependent mitochondrial apoptotic pathway. Herein, we investigated whether the antitumor activity of Roy-Bz, in colon cancer, could be related to glucose metabolism interference. The results showed that Roy-Bz decreased the mitochondrial respiration in human colon HCT116 cancer cells, by reducing electron transfer chain complexes I/III. Consistently, this effect was associated with downregulation of the mitochondrial markers cytochrome c oxidase subunit 4 (COX4), voltage-dependent anion channel (VDAC) and mitochondrial import receptor subunit TOM20 homolog (TOM20), and upregulation of synthesis of cytochrome c oxidase 2 (SCO2). Roy-Bz also dropped glycolysis, decreasing the expression of critical glycolytic markers directly implicated in glucose metabolism such as glucose transporter 1 (GLUT1), hexokinase 2 (HK2) and monocarboxylate transporter 4 (MCT4), and increasing TP53-induced glycolysis and apoptosis regulator (TIGAR) protein levels. These results were further corroborated in tumor xenografts of colon cancer. Altogether, using a PKCδ-selective activator, this work evidenced a potential dual role of PKCδ in tumor cell metabolism, resulting from the inhibition of both mitochondrial respiration and glycolysis. Additionally, it reinforces the antitumor therapeutic potential of Roy-Bz in colon cancer by targeting glucose metabolism.

Metformin enhances anti-cancer properties of resveratrol in MCF-7 breast cancer cells via induction of apoptosis, autophagy and alteration in cell cycle distribution

Breast cancer is the fifth leading cause of death, worldwide affecting both genders. Accumulating evidence suggests that metformin, an oral hypoglycemic agent used in the management of type 2 diabetes, exerts anti-tumor effects in many cancers, including the breast cancer. Resveratrol, a natural product found abundantly in many fruits, exhibits marked cytotoxic and pro-oxidant effects. This study was designed to investigate the effect of metformin in combination with resveratrol and cisplatin in MCF-7 cells. Study groups were as follows: untreated control group, single treatment groups (metformin, resveratrol, and cisplatin), double treatment groups (metformin + resveratrol, metformin + cisplatin, and cisplatin + resveratrol) and triple treatment groups (metformin + resveratrol + cisplatin). Our results indicated that metformin inhibits proliferation of MCF-7 cells, an effect that was associated with ROS production and G0/G1 cell cycle arrest, but not apoptosis. Moreover, resveratrol suppressed the proliferation of MCF-7 cells by induction of apoptosis as well as cell cycle arrest. Notably, a significant inhibitory effect in the co-treatment of metformin, resveratrol, and cisplatin was observed which was attributed to induction of autophagy-mediated cell death and apoptosis along cell cycle arrest. In conclusion, our results advocate the anti-cancer properties of metformin and resveratrol on MCF-7 cell s via induction of cell cycle arrest. Additionally, synergistic anti-cancer effects of metformin in a triple combination with cisplatin and resveratrol was attributed to induction of autophagy-mediated cell death and apoptosis along cell cycle arrest. Based on our findings it is proposed that patients may benefit from addition of a drug with a safe profile to conventional anticancer therapies.

Autophagy and the Insulin-like Growth Factor (IGF) System in Colonic Cells: Implications for Colorectal Neoplasia

Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Along with apoptosis and inflammation, autophagy is one of three important mechanisms in CRC. The presence of autophagy/mitophagy in most normal mature intestinal epithelial cells has been confirmed, where it has mainly protective functions against reactive oxygen species (ROS)-induced DNA and protein damage. Autophagy regulates cell proliferation, metabolism, differentiation, secretion of mucins and/or anti-microbial peptides. Abnormal autophagy in intestinal epithelial cells leads to dysbiosis, a decline in local immunity and a decrease in cell secretory function. The insulin-like growth factor (IGF) signaling pathway plays an important role in colorectal carcinogenesis. This is evidenced by the biological activities of IGFs (IGF-1 and IGF-2), IGF-1 receptor type 1 (IGF-1R) and IGF-binding proteins (IGF BPs), which have been reported to regulate cell survival, proliferation, differentiation and apoptosis. Defects in autophagy are found in patients with metabolic syndrome (MetS), inflammatory bowel diseases (IBD) and CRC. In neoplastic cells, the IGF system modulates the autophagy process bidirectionally. In the current era of improving CRC therapies, it seems important to investigate the exact mechanisms not only of apoptosis, but also of autophagy in different populations of tumor microenvironment (TME) cells. The role of the IGF system in autophagy in normal as well as transformed colorectal cells still seems poorly understood. Hence, the aim of the review was to summarize the latest knowledge on the role of the IGF system in the molecular mechanisms of autophagy in the normal colon mucosa and in CRC, taking into account the cellular heterogeneity of the colonic and rectal epithelium.

Cross-talk between AMP-activated protein kinase and the sonic hedgehog pathway in the high-fat diet triggered colorectal cancer

The major cause of colorectal cancer (CRC) related mortality is due to its metastasis. Signaling pathways play a definite role in the development and progression of CRC. Recent studies demonstrate that the regulation of the sonic hedgehog (Shh) pathway is beneficial in the CRC treatment strategy. Also, 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a well-known regulator of metabolism and inflammation, making it a suitable treatment option for CRC. Consumption of a high-fat diet (HFD) is a significant cause of CRC genesis. Also, the lipids play an indispensable role in aberrant activation of the Shh pathway. This review explains in detail the interconnection between HFD consumption, Shh pathway activation, and the progression of CRC. According to recent studies and literature, AMPK is a potential regulator that can control the complexities of CRC and reduce lipid levels and may directly inhibit shh signalling. The review also suggests the possible risk elements of AMPK activation in CRC due to its context-dependent role. Also, the activation of AMPK in HFD-induced CRC may modulate cancer progression by regulating the Shh pathway and metabolism.

Metformin Induces Apoptosis in Human Pancreatic Cancer (PC) Cells Accompanied by Changes in the Levels of Histone Acetyltransferases (Particularly, p300/CBP-Associated Factor (PCAF) Protein Levels)

Accumulating evidence (mainly from experimental research) suggests that metformin possesses anticancer properties through the induction of apoptosis and inhibition of the growth and proliferation of cancer cells. However, its effect on the enzymes responsible for histone acetylation status, which plays a key role in carcinogenesis, remains unclear. Therefore, the aim of our study was to evaluate the impact of metformin on histone acetyltransferases (HATs) (i.e., p300/CBP-associated factor (PCAF), p300, and CBP) and on histone deacetylases (HDACs) (i.e., SIRT-1 in human pancreatic cancer (PC) cell lines, 1.2B4, and PANC-1). The cells were exposed to metformin, an HAT inhibitor (HATi), or a combination of an HATi with metformin for 24, 48, or 72 h. Cell viability was determined using an MTT assay, and the percentage of early apoptotic cells was determined with an Annexin V-Cy3 Apoptosis Detection Assay Kit. Caspase-9 activity was also assessed. SIRT-1, PCAF, p300, and CBP expression were determined at the mRNA and protein levels using RT-PCR and Western blotting methods, respectively. Our results reveal an increase in caspase-9 in response to the metformin, indicating that it induced the apoptotic death of both 1.2B4 and PANC-1 cells. The number of cells in early apoptosis and the activity of caspase-9 decreased when treated with an HATi alone or a combination of an HATi with metformin, as compared to metformin alone. Moreover, metformin, an HATi, and a combination of an HATi with metformin also modified the mRNA expression of SIRT-1, PCAF, CBP, and p300. However, metformin did not change the expression of the studied genes in 1.2B4 cells. The results of the Western blot analysis showed that metformin diminished the protein expression of PCAF in both the 1.2B4 and PANC-1 cells. Hence, it appears possible that PCAF may be involved in the metformin-mediated apoptosis of PC cells.

Tumor lysis syndrome promotes cancer chemoresistance and relapse through AMPK inhibition

Cancer is a disease caused when cells divide uncontrollably and spread into surrounding tissues. There are different therapeutic modalities that control cancer growth, of which surgery, chemotherapy, and radiotherapy. Chemotherapy is a cancer treatment approach in which medications are used to inhibit cell proliferation and tumor multiplication, thus avoiding invasion and metastasis and thus eradicate cancer. One of the common complications associated with cancer chemotherapy is rapid lysis of expanding tumor cells, known as tumor lysis syndrome (TLS). TLS is associated with number of metabolic changes such as hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcemia. Among the consequences of hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcemia is the inhibition of 5' AMP-activated protein kinase (AMPK). Inhibition of AMPK induced different cancer chemo-resistance mechanisms such as cancer stem cells (CSCs), p-glycoproteins, Octamer-binding transcription factor 4 (OCT-4), homeobox protein NANOG, Krüppel-like factor 4 (KLF4) and immune microenvironment and thus leads to poor response to chemotherapy and even relapses after treatment. Our review aims to uncover new mechanisms underlying the metabolic consequences of tumor lysis on AMPK in tumor microenvironment. In this review, we also investigated the effect of AMPK on different cancer chemo-resistance mechanisms such as cancer stem cells, p-glycoproteins, OCT-4, NANOG, KLF4 and immune microenvironment.

Nanostructured lipid carrier-loaded metformin hydrochloride: Design, optimization, characterization, assessment of cytotoxicity and ROS evaluation

Metformin hydrochloride (MET) is commonly used in diabetes treatment. Recently, it has gained interest for its anticancer potential against a wide range of cancers. Owing to its hydrophilic nature, the delivery and clinical actions of MET are limited. Therefore, the present work aims to develop MET-encapsulated NLCs using the hot-melt emulsification and probe-sonication method. The optimization was accomplished by 3³ BB design wherein lipid ratio, surfactant concentration, and sonication time were independent variables while the PS (nm), PDI, and EE (%) were dependent variables. The PS, PDI, % EE and ZP of optimized _GMSMET-NLCs were found to be 114.9 ± 1.32 nm, 0.268 ± 0.04 %, 60.10 ± 2.23 %, and ZP - 15.76 mV, respectively. The morphological features, DSC and PXRD, and FTIR analyses suggested the confirmation of formation of the NLCs. Besides, optimized _GMSMET-NLCs showed up to 88 % MET release in 24 h. Moreover, _GMSMET-NLCs showed significant cell cytotoxicity against KB oral cancer cells compared with MET solution as shown by the reduction of IC₅₀ values. Additionally, _GMSMET-NLCs displayed significantly increased intracellular ROS levels suggesting the _GMSMET-NLCs induced cell death in KB cells. _GMSMET-NLCs can therefore be explored to deliver MET through different routes of administration for the effective treatment of oral cancer.

Metformin-induced AMPK activation promotes cisplatin resistance through PINK1/Parkin dependent mitophagy in gastric cancer

Gastric cancer (GC) is one of the most common tumors worldwide, and cisplatin is a standard chemotherapeutic reagent for GC treatment. However, chemoresistance is an inherent challenge which limits its application and effectiveness in clinic. This study aims to investigate the mechanism of metformin-induced cisplatin resistance in GC. Intriguingly, the upregulation of mitophagy markers, mitochondrial fission, autophagy and mitophagosome were observed in SGC-7901/DDP cells compared to those in the SGC-7901 cells. Treatment with metformin significantly increased mitochondrial fission and mitophagy in both AGS and SGC-7901 cells, resulting in decreased ATP production, which unexpectedly protected GC cells against the cytotoxicity of cisplatin. In contrast, application of Chloroquine and 3-methyladenine, two inhibitors of autophagy, significantly alleviated the protective effect of metformin on SGC-7901 and AGS cells against cytotoxicity of cisplatin. Moreover, metformin also stimulated the phosphorylation of AMPK (Thr172) and increased the expression of mitophagy markers including Parkin and PINK1 in the AMPK signaling-dependent manner. Consistently, the cell viability and cell apoptosis assay showed that metformin-induced cisplatin resistance was prevented by knockdown of AMPKα1. Taken together, all data in this study indicate that metformin induced AMPK activation and PINK1/Parkin dependent mitophagy, which may contribute to the progression of cisplatin resistance in GC.

Current perspectives on clinical use of exosomes as novel biomarkers for cancer diagnosis

Exosomes are a heterogeneous subset of extracellular vesicles (EVs) that biogenesis from endosomes. Besides, exosomes contain a variety of molecular cargoes including proteins, lipids and nucleic acids, which play a key role in the mechanism of exosome formation. Meanwhile, exosomes are involved with physiological and pathological conditions. The molecular profile of exosomes reflects the type and pathophysiological status of the originating cells so could potentially be exploited for diagnostic of cancer. This review aims to describe important molecular cargoes involved in exosome biogenesis. In addition, we highlight exogenous factors, especially autophagy, hypoxia and pharmacology, that regulate the release of exosomes and their corresponding cargoes. Particularly, we also emphasize exosome molecular cargoes as potential biomarkers in liquid biopsy for diagnosis of cancer.

Exploring the Mechanism of Adjuvant Treatment of Glioblastoma Using Temozolomide and Metformin

Glioblastoma is the most frequent and lethal primary central nervous system tumor in adults, accounting for around 15% of intracranial neoplasms and 40–50% of all primary malignant brain tumors, with an annual incidence of 3–6 cases per 100,000 population. Despite maximum treatment, patients only have a median survival time of 15 months. Metformin is a biguanide drug utilized as the first-line medication in treating type 2 diabetes. Recently, researchers have noticed that metformin can contribute to antineoplastic activity. The objective of this study is to investigate the mechanism of metformin as a potential adjuvant treatment drug in glioblastoma. Glioblastoma cell lines U87MG, LNZ308, and LN229 were treated with metformin, and several cellular functions and metabolic states were evaluated. First, the proliferation capability was investigated using the MTS assay and BrdU assay, while cell apoptosis was evaluated using the annexin V assay. Next, a wound-healing assay and mesenchymal biomarkers (N-cadherin, vimentin, and Twist) were used to detect the cell migration ability and epithelial–mesenchymal transition (EMT) status of tumor cells. Gene set enrichment analysis (GSEA) was applied to the transcriptome of the metformin-treated glioblastoma cell line. Then, DCFH-DA and MitoSOX Red dyes were used to quantify reactive oxygen species (ROS) in the cytosol and mitochondria. JC-1 dye and Western blotting analysis were used to evaluate mitochondrial membrane potential and biogenesis. In addition, the combinatory effect of temozolomide (TMZ) with metformin treatment was assessed by combination index analysis. Metformin could decrease cell viability, proliferation, and migration, increase cell apoptosis, and disrupt EMT in all three glioblastoma cell lines. The GSEA study highlighted increased ROS and hypoxia in the metformin-treated glioblastoma cells. Metformin increased ROS production, impaired mitochondrial membrane potential, and reduced mitochondrial biogenesis. The combined treatment of metformin and TMZ had U87 as synergistic, LNZ308 as antagonistic, and LN229 as additive. Metformin alone or combined with TMZ could suppress mitochondrial transcription factor A, Twist, and O⁶-methylguanine-DNA methyltransferase (MGMT) proteins in TMZ-resistant LN229 cells. In conclusion, our study showed that metformin decreased metabolic activity, proliferation, migration, mitochondrial biogenesis, and mitochondrial membrane potential and increased apoptosis and ROS in some glioblastoma cells. The sensitivity of the TMZ-resistant glioblastoma cell line to metformin might be mediated via the suppression of mitochondrial biogenesis, EMT, and MGMT expression. Our work provides new insights into the choice of adjuvant agents in TMZ-resistant GBM therapy.

Metformin Protects Against Sunitinib-induced Cardiotoxicity: Investigating the Role of AMPK

ABSTRACT

Sunitinib is associated with cardiotoxicity through inhibition of AMP-protein kinase (AMPK) signaling. By contrast, the common antidiabetic agent metformin has demonstrated cardioprotection through indirect AMPK activation. In this study, we investigate the effects of metformin during sunitinib-induced cytotoxicity. Left ventricular developed pressure, coronary flow, heart rate, and infarct size were measured in Langendorff-perfused rat hearts treated with 1 µM sunitinib ±50 µM metformin ±1 µM human equilibrative nucleoside transporter inhibitor S-(4-Nitrobenzyl)-6-thioinosine (NBTI). Western blot analysis was performed for p-AMPKα levels. Primary isolated cardiac myocytes from the left ventricular tissue were used to measure live cell population levels. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to assess adjunctive treatment of and metformin in human hepatoma G2 and promyelocytic leukemia (HL-60) cells treated with 0.1-100 µM sunitinib ±50 µM metformin. In the perfused hearts, coadministration of metformin attenuated the sunitinib-induced changes to left ventricular developed pressure, infarct size, and cardiac myocyte population. Western blot analysis revealed a significant decrease in p-AMPKα during sunitinib treatment, which was attenuated after coadministration with metformin. All metformin-induced effects were attenuated, and NBTI was coadministered. The MTT assay demonstrated an increase in the EC50 value during coadministration of metformin with sunitinib compared with sunitinib monotherapy in hepatoma G2 and HL-60 cell lines, demonstrating the impact and complexity of metformin coadministration and the possible role of AMPK signaling. This study highlights the novel cardioprotective properties of metformin and AMPK activation during sunitinib-induced cardiotoxicity when administered together in the Langendorff heart model.

Metformin Enhancement of Therapeutic Effects of 5-Fluorouracil and Oxaliplatin in Colon Cancer Cells and Nude Mice

Studies have demonstrated that metformin has antitumor effects in addition to therapeutic effects on hyperglycemia; however, few studies have explored the effects of metformin in chemotherapy. Therefore, we hypothesized that the administration of metformin would enhance the therapeutic effects of 5-fluorouracil and oxaliplatin (FuOx) to inhibit the growth of colorectal cancer (CRC) cells in vitro and in vivo. The results of our in vitro experiments demonstrated that metformin significantly increased the effects of FuOx with respect to cell proliferation (p < 0.05), colony formation (p < 0.05), and migration (p < 0.01) and induced cell cycle arrest in the G0/G1 phase in HT29 cells and the S phase in SW480 and SW620 cells (p < 0.05). Flow cytometry analysis revealed that metformin combined with FuOx induced late apoptosis (p < 0.05) by mediating mitochondria-related Mcl-1 and Bim protein expression. Furthermore, in vivo, metformin combined with FuOx more notably reduced tumor volume than FuOx or metformin alone did in BALB/c mice (p < 0.05). These findings demonstrate that metformin may act as an adjunctive agent to enhance the chemosensitivity of CRC cells to FuOx. However, further clinical trials are warranted to validate the clinical implications of the findings.

Crosstalk Between ROS and Autophagy in Tumorigenesis: Understanding the Multifaceted Paradox

Cancer formation is a highly regulated and complex process, largely dependent on its microenvironment. This complexity highlights the need for developing novel target-based therapies depending on cancer phenotype and genotype. Autophagy, a catabolic process, removes damaged and defective cellular materials through lysosomes. It is activated in response to stress conditions such as nutrient deprivation, hypoxia, and oxidative stress. Oxidative stress is induced by excess reactive oxygen species (ROS) that are multifaceted molecules that drive several pathophysiological conditions, including cancer. Moreover, autophagy also plays a dual role, initially inhibiting tumor formation but promoting tumor progression during advanced stages. Mounting evidence has suggested an intricate crosstalk between autophagy and ROS where they can either suppress cancer formation or promote disease etiology. This review highlights the regulatory roles of autophagy and ROS from tumor induction to metastasis. We also discuss the therapeutic strategies that have been devised so far to combat cancer. Based on the review, we finally present some gap areas that could be targeted and may provide a basis for cancer suppression.

Metformin and ICG-001 Act Synergistically to Abrogate Cancer Stem Cells-Mediated Chemoresistance in Colorectal Cancer by Promoting Apoptosis and Autophagy

Simple Summary

Colorectal cancer (CRC) is one of the most frequently diagnosed and lethal malignancies. The majority of CRC patients experience disease relapse after the primary curative treatment strategy of surgery followed by 5FU-based chemotherapy. The presence of cancer stem-like cells (CSCs) is considered to be one of the contributing factors to therapy resistance and disease relapse in CRC. Previous studies implicated the role of the Wnt signaling pathway in the maintenance of the CSC phenotype. Therefore, in this study we explored a novel therapeutic strategy using metformin along with ICG-001, a Wnt signaling inhibitor, to abrogate CSC-mediated chemoresistance in CRC. We observed that metformin and ICG-001 abrogate stemness in a synergistic manner by promoting autophagy and apoptosis in 5FU-resistant CRC cells as well as in CRC patient-derived tumor organoids. Hence, metformin and ICG-001 can be used as part of a therapeutic strategy to overcome 5FU-mediated therapeutic resistance in CRC.

Abstract

Colorectal cancer (CRC) remains the third most frequently diagnosed cancer in the United States. The current treatment regimens for CRC include surgery followed by 5FU-based chemotherapy. Cancer stem-like cells (CSCs) have been implicated in 5FU-mediated chemoresistance, which leads to poor prognosis. In this study, we used metformin along with ICG-001, a Wnt signaling inhibitor, to abrogate CSC-mediated chemoresistance in CRC. We observed that 5FU-resistant (5FUR) CRC cells exhibited increased expression of CSC markers and enhanced spheroid formation. Genome-wide transcriptomic profiling analysis revealed that Wnt signaling, colorectal cancer metastasis signaling, etc., were enriched in 5FUR CRC cells. Accordingly, selective targeting of Wnt signaling using ICG-001 along with metformin abrogated CSC-mediated chemoresistance by decreasing the expression of CSC markers and promoting autophagy and apoptosis in a synergistic manner. We also observed that metformin and ICG-001 exhibited anti-tumor activity in CRC patient-derived tumor organoids. In conclusion, our study highlights that metformin and ICG-001 act synergistically and can be used as part of a therapeutic strategy to overcome 5FU-mediated therapeutic resistance in CRC.

Metformin suppresses the growth of colorectal cancer by targeting INHBA to inhibit TGF-β/PI3K/AKT signaling transduction

Multiple evidence shows that metformin serves as a potential agent for Colorectal Cancer (CRC) treatment, while its molecular mechanisms still require detailed investigation. Here, we revealed that metformin specifically suppressed the proliferation of CRC cells by causing G1/S arrest, and INHBA is a potential target for metformin to play an anti-proliferation effect in CRC. We verified the oncogene role of INHBA by knocking down and overexpressing INHBA in CRC cells. Silencing INHBA abrogated the cell growth, while overexpression INHBA promotes the proliferation of CRC cells. As an oncogene, INHBA was aberrant overexpression in CRC tissues and closely related to the poor prognosis of CRC patients. In mechanism, INHBA is an important ligand of TGF-β signaling and metformin blocked the activation of TGF-β signaling by targeting INHBA, and then down-regulated the activity of PI3K/Akt pathway, leading to the reduction of cyclinD1 and cell cycle arrest. Together, these findings indicate that metformin down-regulates the expression of INHBA, then attenuating TGF-β/PI3K/Akt signaling transduction, thus inhibiting the proliferation of CRC. Our study elucidated a novel molecular mechanism for the anti-proliferation effect of metformin, providing a theoretical basis for the application of metformin in CRC therapy.

Autophagy-mediated degradation of NOTCH1 intracellular domain controls the epithelial to mesenchymal transition and cancer metastasis

Backgound

Autophagy controls levels of cellular components during normal and stress conditions; thus, it is a pivotal process for the maintenance of cell homeostasis. In cancer, autophagy protects cells from cancerous transformations that can result from genomic instability induced by reactive oxygen species or other damaged components, but it can also promote cancer survival by providing essential nutrients during the metabolic stress condition of cancer progression. However, the molecular mechanism underlying autophagy-dependent regulation of the epithelial to mesenchymal transition (EMT) and metastasis is still elusive.

Methods

The intracellular level of NOTCH1 intracellular domain (NICD) in several cancer cells was studied under starvation, treatment with chloroquine or ATG7-knockdown. The autophagy activity in these cells was assessed by immunocytochemistry and molecular analyses. Cancer cell migration and invasion under modulation of autophagy were determined by in vitro scratch and Matrigel assays.

Results

In the study, autophagy activation stimulated degradation of NICD, a key transcriptional regulator of the EMT and cancer metastasis. We also found that NICD binds directly to LC3 and that the NICD/LC3 complex associates with SNAI1 and sequestosome 1 (SQSTM1)/p62 proteins. Furthermore, the ATG7 knockdown significantly inhibited degradation of NICD under starvation independent of SQSTM1-associated proteasomal degradation. In addition, NICD degradation by autophagy associated with the cellular level of SNAI1. Indeed, autophagy inhibited nuclear translocation of NICD protein and consequently decreased the transcriptional activity of its target genes. Autophagy activation substantially suppressed in vitro cancer cell migration and invasion. We also observed that NICD and SNAI1 levels in tissues from human cervical and lung cancer patients correlated inversely with expression of autophagy-related proteins.

Conclusions

These findings suggest that the cellular level of NICD is regulated by autophagy during cancer progression and that targeting autophagy-dependent NICD/SNAI1 degradation could be a strategy for the development of cancer therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00752-3.

Functional assessment of miR‑1291 in colon cancer cells

miR‑1291 exerts an anti‑tumor effect in a subset of human carcinomas, including pancreatic cancer. However, its role in colorectal cancer (CRC) is largely unknown. In the present study, the expression and effect of miR‑1291 in CRC cells was investigated. It was identified that miR‑1291 significantly suppressed the proliferation, invasion, cell mobility and colony formation of CRC cells. Additionally, miR‑1291 induced cell apoptosis. A luciferase reporter assay revealed that miR‑1291 directly bound the 3'‑untranslated region sequence of doublecortin‑like kinase 1 (DCLK1). miR‑1291 also suppressed DCLK1 mRNA and protein expression in HCT116 cells that expressed DCLK1. Furthermore, miR‑1291 suppressed cancer stem cell markers BMI1 and CD133, and inhibited sphere formation. The inhibitory effects on sphere formation, invasion and mobility in HCT116 cells were also explored and verified using DCLK1 siRNAs. Furthermore, miR‑1291 induced CDK inhibitors p21WAF1/CIP1 and p27KIP1 in three CRC cell lines, and the overexpression of DCLK1 in HCT116 cells led to a decrease of p21WAF1/CIP1 and p27KIP1. Intravenous administration of miR‑1291 loaded on the super carbonate apatite delivery system significantly inhibited tumor growth in the DLD‑1 xenograft mouse model. Additionally, the resultant tumors exhibited significant upregulation of the p21WAF1/CIP1 and p27KIP1 protein with treatment of miR‑1291. Taken together, the results indicated that miR‑1291 served an anti‑tumor effect by modulating multiple functions, including cancer stemness and cell cycle regulation. The current data suggested that miR‑1291 may be a promising nucleic acid medicine against CRC.

Dual anticancer role of metformin: an old drug regulating AMPK dependent/independent pathways in metabolic, oncogenic/tumorsuppresing and immunity context

Metformin has been known to treat type 2 diabetes for decades and is widely prescribed antidiabetic drug. Recently, its anticancer potential has also been discovered. Moreover, metformin has low cost thus it has attained profound research interest. Comprehensing the complexity of the molecular regulatory networks in cancer provides a mode for advancement of research in cancer development and treatment. Metformin targets many pathways that play an important role in cancer cell survival outcome. Here, we described anticancer activity of metformin on the AMPK dependent/independent mechanisms regulating metabolism, oncogene/tumor suppressor signaling pathways together with the issue of clinical studies. We also provided brief overwiev about recently described metformin's role in cancer immunity. Insight in these complex molecular networks, will simplify application of metformin in clinical trials and contribute to improvement of anti-cancer therapy.

Adverse Effects of Metformin From Diabetes to COVID-19, Cancer, Neurodegenerative Diseases, and Aging: Is VDAC1 a Common Target?

Metformin has been used for treating diabetes mellitus since the late 1950s. In addition to its antihyperglycemic activity, it was shown to be a potential drug candidate for treating a range of other diseases that include various cancers, cardiovascular diseases, diabetic kidney disease, neurodegenerative diseases, renal diseases, obesity, inflammation, COVID-19 in diabetic patients, and aging. In this review, we focus on the important aspects of mitochondrial dysfunction in energy metabolism and cell death with their gatekeeper VDAC1 (voltage-dependent anion channel 1) as a possible metformin target, and summarize metformin's effects in several diseases and gut microbiota. We question how the same drug can act on diseases with opposite characteristics, such as increasing apoptotic cell death in cancer, while inhibiting it in neurodegenerative diseases. Interestingly, metformin's adverse effects in many diseases all show VDAC1 involvement, suggesting that it is a common factor in metformin-affecting diseases. The findings that metformin has an opposite effect on various diseases are consistent with the fact that VDAC1 controls cell life and death, supporting the idea that it is a target for metformin.

Combining repurposed drugs to treat colorectal cancer

The drug development process, especially of antineoplastic agents, has become increasingly costly and ineffective. Drug repurposing and drug combination are alternatives to de novo drug development, being low cost, rapid, and easy to apply. These strategies allow higher efficacy, decreased toxicity, and overcoming of drug resistance. The combination of antineoplastic agents is already being applied in cancer therapy, but the combination of repurposed drugs is still under-explored in pre- and clinical development. In this review, we provide a set of pharmacological concepts focusing on drug repurposing for treating colorectal cancer (CRC) and that are relevant for the application of new drug combinations against this disease.

Implications of reactive oxygen species on cancer formation and its treatment

Elevated levels of reactive oxygen species (ROS) are a hallmark of cancer. Although increased ROS concentrations play important roles in cancer formation and progression, levels above a cytotoxic threshold cause cancer cell death. Cancer cells adapt to high concentrations of ROS via antioxidant production and reprogrammed cellular metabolism (eg, the Warburg effect). Because some widely used anticancer therapies such as radiation therapy and chemotherapy rely on ROS accumulation as a mechanism to induce cancer cell death, a cancer cell's ability to control ROS levels is a driver of treatment resistance and a critical consideration for successful cancer treatment. The necessity for cancer cells to adapt to elevated levels of ROS to survive may represent an Achilles heel for some malignancies, as therapies designed to interfere with this adaptation would be expected to kill cancer cells. In this review, we provide an overview of the implications of ROS on cancer formation and anticancer treatment strategies, with a focus on treatment-resistant disease.

Disulfiram and metformin combination anticancer effect reversible partly by antioxidant nitroglycerin and completely by NF-κB activator mebendazole in hamster fibrosarcoma

We investigated the anticancer effect of disulfiram and metformin combination on fibrosarcoma in hamsters. Hamsters of both sexes (~ 70 g) were randomly allocated to control and experimental groups (8 animals per group). In all 10 groups, 2 × 10⁶ BHK-21/C13 cells in 1 ml were injected subcutaneously into the animals' backs. Peroral treatments were carried out with disulfiram 50 mg/kg daily, or with metformin 500 mg/kg daily, or with their combination. Validation and rescue grups were treated by double doses of the single therapy and by the combination with addition of rescue daily doses of ROS inhibitor nitroglycerin 25 mg/kg or NF-κB stimulator mebendazole 460 mg/kg, via a gastric probe after tumor inoculation. After 19 days all animals were sacrificed. Blood samples were collected for hematological and biochemical analyses, the tumors were excised and weighed, and their diameters and volumes were measured. The tumor samples were pathohistologically and immunohistochemically assessed (Ki-67, PCNA, CD34, CD31, COX4, Cytochrome C, GLUT1, iNOS), and the main organs were toxicologically tested. The combination of disulfiram and metformin significantly inhibited fibrosarcoma growth in hamsters without toxicity, compared to monotherapy or control. The single treatments did not show significant antisarcoma effect. Co-treatment with nitroglycerin partly rescued tumor progression, probably by ROS inhibition, while mebendazole completely blocked anticancer activity of the disulfiram and metformin combination, most likely by NF-κB stimulation. Combination of disulfiram with metformin may be used as an effective and safe candidate for novel nontoxic adjuvant and relapse prevention anticancer therapy.

Metformin attenuates the epithelial-mesenchymal transition of lens epithelial cells through the AMPK/TGF-β/Smad2/3 signalling pathway

Posterior capsule opacification (PCO) is a common ocular fibrosis disease related to the epithelial-mesenchymal transition (EMT) of human lens epithelial cells (HLECs). However, safe and effective drugs that prevent or treat PCO are lacking. Metformin (Mtf) has been used to treat fibrosis-related diseases affecting many organs and tissues, but its effect on ocular fibrosis-related diseases is unclear. We investigated whether Mtf can inhibit EMT and fibrosis in HLECs to prevent and treat PCO and elucidated the potential molecular mechanism. Here, we established an HLEC model of TGF-β-induced EMT and found that 400 μM Mtf inhibited vertical and lateral migration and EMT-related gene and protein expression in HLECs. Smad2/3 are downstream molecules of TGF-β that enter the nucleus to regulate EMT-related gene expression during the occurrence and development of PCO. We revealed that Mtf suppressed TGF-β-induced Smad2/3 phosphorylation and nuclear translocation. Mtf induces AMP-activated protein kinase (AMPK) phosphorylation. In this study, we found that Mtf induced the activation of AMPK phosphorylation in HLECs. To further explore the mechanism of Mtf, we pretreated HLECs with Compound C (an AMPK inhibitor) to repeat the above experiments and found that Compound C abolished the inhibitory effect of Mtf on HLEC EMT and the TGF-β/Smad2/3 signalling pathway. Thus, Mtf targets AMPK phosphorylation to inhibit the TGF-β/Smad2/3 signalling pathway and prevent HLEC EMT. Notably, we first illustrated the AMPK/TGF-β/Smad2/3 signalling pathway in HLECs, which may provide a new therapeutic strategy for PCO.

Estradiol ameliorates metformin-inhibited Sertoli cell proliferation via AMPK/TSC2/mTOR signaling pathway

Metformin is a commonly used for treating type 2 diabetes and it acts on a variety of organs including the male reproductive system. 17β-estradiol plays an important role in Sertoli cell (SC) proliferation which determines the germ cell development and spermatogenesis. The aim of this study is to investigate the effect of metformin on immature chicken SC proliferation and the potential mechanisms by which 17β-estradiol regulate this process. Results showed that metformin significantly inhibited SC proliferation, whereas 17β-estradiol weakened the inhibitory effects of metformin on SC viability, cell growth, and cell cycle progression. SC proliferation-inhibiting effect of metformin exposure was regulated by decreasing adenosine triphosphate level and respiratory enzyme activity in the mitochondria; this process was possibly mediated by the adenosine monophosphate-activated protein kinase (AMPK)/tuberous sclerosis complex 2 (TSC2)/mammalian target of rapamycin (mTOR) signaling pathway, which was regulated by the down-expressed miR-1764 and by the decreased antioxidant enzyme activity and excessive reactive oxygen species generation. In addition, SCs transfected with the miR-1764 agomir led to an improvement of proliferation capacity through down-regulating AMPKα2 level, which further decreased TSC2 expression and induced mTOR activation. However, the anti-proliferative effect of miR-1764 antagomir can be alleviated by 17β-estradiol treatment via the up-expression of miR-1764 in transfected SCs. Our findings suggest appropriate dose of exogenous 17β-estradiol treatment can ameliorate the inhibitory effect of metformin on SC proliferation via the regulation of AMPK/TSC2/mTOR signaling pathway, this might reduce the risk of poor male fertility caused by the abuse of anti-diabetic agents.

Reactive Oxygen Species: A Promising Therapeutic Target for SDHx-Mutated Pheochromocytoma and Paraganglioma

Simple Summary

Pheochromocytoma and paraganglioma are rare neuroendocrine tumors that arise from chromaffin cells of the adrenal medulla or their neural crest progenitors located outside the adrenal gland, respectively. About 10–15% of patients develop metastatic disease for whom treatment options and availability are extremely limited. The risk of developing metastatic disease is increased for patients with mutations in succinate dehydrogenase subunit B, which leads to metabolic reprogramming and redox imbalance. From this perspective, we focus on redox imbalance caused by this mutation and explore potential opportunities to therapeutically target reactive oxygen species production in these rare tumors.

Abstract

Pheochromocytoma (PHEO) and paraganglioma (PGL) are rare neuroendocrine tumors derived from neural crest cells. Germline variants in approximately 20 PHEO/PGL susceptibility genes are found in about 40% of patients, half of which are found in the genes that encode succinate dehydrogenase (SDH). Patients with SDH subunit B (SDHB)-mutated PHEO/PGL exhibit a higher likelihood of developing metastatic disease, which can be partially explained by the metabolic cell reprogramming and redox imbalance caused by the mutation. Reactive oxygen species (ROS) are highly reactive molecules involved in a multitude of important signaling pathways. A moderate level of ROS production can help regulate cellular physiology; however, an excessive level of oxidative stress can lead to tumorigenic processes including stimulation of growth factor-dependent pathways and the induction of genetic instability. Tumor cells effectively exploit antioxidant enzymes in order to protect themselves against harmful intracellular ROS accumulation, which highlights the essential balance between ROS production and scavenging. Exploiting ROS accumulation can be used as a possible therapeutic strategy in ROS-scavenging tumor cells. Here, we focus on the role of ROS production in PHEO and PGL, predominantly in SDHB-mutated cases. We discuss potential strategies and approaches to anticancer therapies by enhancing ROS production in these difficult-to-treat tumors.

The Anti-Tumor Effect of Lactococcus lactis Bacteria-Secreting Human Soluble TRAIL Can Be Enhanced by Metformin Both In Vitro and In Vivo in a Mouse Model of Human Colorectal Cancer

Simple Summary

Colorectal cancer (CRC) is a major cause of morbidity and mortality in Europe, and accounts for over 10% of all cancer-related deaths worldwide. These indicate an urgent need for novel therapeutic options in CRC. Here, we analysed if genetically modified non-pathogenic Lactococcus lactis bacteria can be used for local delivery of human recombinant Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) and induction of tumor cells death in vitro and in vivo in CRC mouse model. We showed that modified L. lactis bacteria were able to secrete biologically active human soluble TRAIL (L. lactis(hsTRAIL+)), which selectively eliminated human CRC cells in vitro, and was further strengthened by metformin (MetF). Our results from in vitro studies were confirmed in vivo using subcutaneous NOD-SCID mouse model of human CRC. The data showed a significant reduction of the tumor growth by intratumor injection of L. lactis(hsTRAIL+) bacteria producing hsTRAIL. This effect could be further enhanced by oral administration of MetF.

Abstract

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) induces apoptosis of many cancer cells, including CRC cells, being non-harmful for normal ones. However, recombinant form of human TRAIL failed in clinical trial when administered intravenously. To assess the importance of TRAIL in CRC patients, new form of TRAIL delivery would be required. Here we used genetically modified, non-pathogenic Lactococcus lactis bacteria as a vehicle for local delivery of human soluble TRAIL (hsTRAIL) in CRC. Operating under the Nisin Controlled Gene Expression System (NICE), the modified bacteria (L. lactis(hsTRAIL+)) were able to induce cell death of HCT116 and SW480 human cancer cells and reduce the growth of HCT116-tumor spheres in vitro. This effect was cancer cell specific as the cells of normal colon epithelium (FHC cells) were not affected by hsTRAIL-producing bacteria. Metformin (MetF), 5-fluorouracil (5-FU) and irinotecan (CPT-11) enhanced the anti-tumor actions of hsTRAIL in vitro. In the NOD-SCID mouse model, treatment of subcutaneous HCT116-tumors with L. lactis(hsTRAIL+) bacteria given intratumorally, significantly reduced the tumor growth. This anti-tumor activity of hsTRAIL in vivo was further enhanced by oral administration of MetF. These findings indicate that L. lactis bacteria could be suitable for local delivery of biologically active human proteins. At the same time, we documented that anti-tumor activity of hsTRAIL in experimental therapy of CRC can be further enhanced by MetF given orally, opening a venue for alternative CRC-treatment strategies.

Cross talk between autophagy and oncogenic signaling pathways and implications for cancer therapy

Autophagy is a highly conserved metabolic process involved in the degradation of intracellular components including proteins and organelles. Consequently, it plays a critical role in recycling metabolic energy for the maintenance of cellular homeostasis in response to various stressors. In cancer, autophagy either suppresses or promotes cancer progression depending on the stage and cancer type. Epithelial-mesenchymal transition (EMT) and cancer metastasis are directly mediated by oncogenic signal proteins including SNAI1, SLUG, ZEB1/2, and NOTCH1, which are functionally correlated with autophagy. In this report, we discuss the crosstalk between oncogenic signaling pathways and autophagy followed by possible strategies for cancer treatment via regulation of autophagy. Although autophagy affects EMT and cancer metastasis, the overall signaling pathways connecting cancer progression and autophagy are still illusive. In general, autophagy plays a critical role in cancer cell survival by providing a minimum level of energy via self-digestion. Thus, cancer cells face nutrient limitations and challenges under stress during EMT and metastasis. Conversely, autophagy acts as a potential cancer suppressor by degrading oncogenic proteins, which are essential for cancer progression, and by removing damaged components such as mitochondria to enhance genomic stability. Therefore, autophagy activators or inhibitors represent possible cancer therapeutics. We further discuss the regulation of autophagy-dependent degradation of oncogenic proteins and its functional correlation with oncogenic signaling pathways, with potential applications in cancer therapy.

Repurposing metformin for the treatment of gastrointestinal cancer

Diabetes mellitus type 2 and cancer share many risk factors. The pleiotropic insulin-dependent and insulin-independent effects of metformin might inhibit pathways that are frequently amplified in neoplastic tissue. Particularly, modulation of inflammation, metabolism, and cell cycle arrest are potential therapeutic cancer targets utilized by metformin to boost the anti-cancer effects of chemotherapy. Studies in vitro and in vivo models have demonstrated the potential of metformin as a chemo- and radiosensitizer, besides its chemopreventive and direct therapeutic activity in digestive system (DS) tumors. Hence, these aspects have been considered in many cancer clinical trials. Case-control and cohort studies and associated meta-analyses have evaluated DS cancer risk and metformin usage, especially in colorectal cancer, pancreatic cancer, and hepatocellular carcinoma. Most clinical studies have demonstrated the protective role of metformin in the risk for DS cancers and survival rates. On the other hand, the ability of metformin to enhance the actions of chemotherapy for gastric and biliary cancers is yet to be investigated. This article reviews the current findings on the anti-cancer mechanisms of metformin and its apparatus from pre-clinical and ongoing studies in DS malignancies.

Oxidative Stress in Cancer Cell Metabolism

Reactive oxygen species (ROS) are important in regulating normal cellular processes whereas deregulated ROS leads to the development of a diseased state in humans including cancers. Several studies have been found to be marked with increased ROS production which activates pro-tumorigenic signaling, enhances cell survival and proliferation and drives DNA damage and genetic instability. However, higher ROS levels have been found to promote anti-tumorigenic signaling by initiating oxidative stress-induced tumor cell death. Tumor cells develop a mechanism where they adjust to the high ROS by expressing elevated levels of antioxidant proteins to detoxify them while maintaining pro-tumorigenic signaling and resistance to apoptosis. Therefore, ROS manipulation can be a potential target for cancer therapies as cancer cells present an altered redox balance in comparison to their normal counterparts. In this review, we aim to provide an overview of the generation and sources of ROS within tumor cells, ROS-associated signaling pathways, their regulation by antioxidant defense systems, as well as the effect of elevated ROS production in tumor progression. It will provide an insight into how pro- and anti-tumorigenic ROS signaling pathways could be manipulated during the treatment of cancer.

Repositioning metformin and propranolol for colorectal and triple negative breast cancers treatment

Drug repositioning refers to new uses for existing drugs outside the scope of the original medical indications. This approach fastens the process of drug development allowing finding effective drugs with reduced side effects and lower costs. Colorectal cancer (CRC) is often diagnosed at advanced stages, when the probability of chemotherapy resistance is higher. Triple negative breast cancer (TNBC) is the most aggressive type of breast cancer, highly metastatic and difficult to treat. For both tumor types, available treatments are generally associated to severe side effects. In our work, we explored the effect of combining metformin and propranolol, two repositioned drugs, in both tumor types. We demonstrate that treatment affects viability, epithelial-mesenchymal transition and migratory potential of CRC cells as we described before for TNBC. We show that combined treatment affects different steps leading to metastasis in TNBC. Moreover, combined treatment is also effective preventing the development of 5-FU resistant CRC. Our data suggest that combination of metformin and propranolol could be useful as a putative adjuvant treatment for both TNBC and CRC and an alternative for chemo-resistant CRC, providing a low-cost alternative therapy without associated toxicity.