Metformin Inhibits Progression of Head and Neck Squamous Cell Carcinoma by Acting Directly on Carcinoma-Initiating Cells

Histone modifications in head and neck squamous cell carcinoma

Head and neck cancer is the main cause of cancer death worldwide, with squamous cell carcinoma (HNSCC) being the second most frequent subtype. HNSCC poses significant health threats due to its high incidence and poor prognosis, underscoring the urgent need for advanced research. Histone modifications play a crucial role in the regulation of gene expression and influencing various biological processes. In the context of HNSCC, aberrant histone modifications are increasingly recognized as critical contributors to its development and pathologic progression. This review demonstrates the molecular mechanisms, by which histone modifications such as acetylation, methylation, phosphorylation, and ubiquitination, impact the pathogenesis of HNSCC. The dysregulation of histone-modifying enzymes, including histone acetyltransferases (HATs), histone deacetylases (HDACs), and histone methyltransferases (HMTs), is discussed for its role in altering chromatin structure and gene expression in HNSCC. Moreover, we will explore the potential of targeting histone modifications as a therapeutic strategy, highlighting current preclinical and clinical studies that investigate histone deacetylase inhibitors (HDIs) and other epigenetic drugs, referring to the completed and ongoing clinical trials on those medications.

The mechanisms of action of metformin on head and neck cancer in the pre-clinical setting: a scoping review

This scoping review identifies the mechanistic pathways of metformin when used to treat head and neck cancer cells, in the pre-clinical setting. Understanding the underlying mechanisms will inform future experimental designs exploring metformin as a potential adjuvant for head and neck cancer. This scoping review was conducted according to the Joanna-Briggs Institute framework. A structured search identified 1288 studies, of which 52 studies fulfilled the eligibility screen. The studies are presented in themes addressing hallmarks of cancer. Most of the studies demonstrated encouraging anti-proliferative effects in vitro and reduced tumor weight and volume in animal models. However, a few studies have cautioned the use of metformin which supported cancer cell growth under certain conditions.

Phase I / II trial of metformin as a chemo-radiosensitizer in a head and neck cancer patient population

OBJECTIVES

Retrospective studies have shown that head and neck squamous cell carcinoma (HNSCC) patients taking metformin demonstrate superior survival compared to their counterparts. We sought to determine whether metformin combined with chemoradiation would improve HNSCC patient survival compared to historical controls.

MATERIALS AND METHODS

We conducted a Phase I/II prospective, single arm clinical trial in patients with newly diagnosed HNSCC (NCT02949700). Patients received platinum-based chemoradiation in combination with orally dosed metformin at one of 2 doses- 850 mg BID or 1500 mg BID administered during radiation, with a 2-week lead-in phase. Toxicity, disease response and survival metrics were ascertained throughout the study period.

RESULTS

A total of 25 patients were evaluable for toxicity and survival; 9 failed to reach the predetermined 70% compliance with the study drug. No dose limiting toxicities were identified in the Phase I component and there were no grade 4 adverse events likely related to metformin throughout the study. The primary outcome for the Phase II component was met with a response rate of 96%. Three-year overall survival was ∼70% in the per protocol p16 + cohort and 0% in the per protocol p16- cohort. Survival among participants with a ≥70% metformin compliance to <70% metformin compliance demonstrated a trend towards improvement in the ≥70% compliance cohort, though this did not reach significance.

CONCLUSION

Metformin is well tolerated during concurrent chemoradiation for HNSCC. Its effectiveness as a chemo-radiosensitizer remains unclear and will require further study with randomized controlled clinical trials in this patient population.

Cancer stem cell fate determination: mito-nuclear communication

Cancer stem cells (CSCs) are considered to be responsible for tumor recurrence and metastasis. Therefore, clarification of the mechanisms involved in CSC stemness maintenance and cell fate determination would provide a new strategy for cancer therapy. Unregulated cellular energetics has been accepted as one of the hallmarks of cancer cells, but recent studies have revealed that mitochondrial metabolism can also actively determine CSC fate by affecting nuclear stemness gene expression. Herein, from the perspective of mito-nuclear communication, we review recent progress on the influence of mitochondria on CSC potential from four aspects: metabolism, dynamics, mitochondrial homeostasis, and reactive oxygen species (ROS). Video Abstract.

NDUFS3 knockout cancer cells and molecular docking reveal specificity and mode of action of anti-cancer respiratory complex I inhibitors

Inhibition of respiratory complex I (CI) is becoming a promising anti-cancer strategy, encouraging the design and the use of inhibitors, whose mechanism of action, efficacy and specificity remain elusive. As CI is a central player of cellular bioenergetics, a finely tuned dosing of targeting drugs is required to avoid side effects. We compared the specificity and mode of action of CI inhibitors metformin, BAY 87-2243 and EVP 4593 using cancer cell models devoid of CI. Here we show that both BAY 87-2243 and EVP 4593 were selective, while the antiproliferative effects of metformin were considerably independent from CI inhibition. Molecular docking predictions indicated that the high efficiency of BAY 87-2243 and EVP 4593 may derive from the tight network of bonds in the quinone binding pocket, although in different sites. Most of the amino acids involved in such interactions are conserved across species and only rarely found mutated in human. Our data make a case for caution when referring to metformin as a CI-targeting compound, and highlight the need for dosage optimization and careful evaluation of molecular interactions between inhibitors and the holoenzyme.

Integrating Genetic Alterations and the Hippo Pathway in Head and Neck Squamous Cell Carcinoma for Future Precision Medicine

Genetic alterations and dysregulation of signaling pathways are indispensable for the initiation and progression of cancer. Understanding the genetic, molecular, and signaling diversities in cancer patients has driven a dynamic change in cancer therapy. Patients can select a suitable molecularly targeted therapy or immune checkpoint inhibitor based on the driver gene alterations determined by sequencing of cancer tissue. This “precision medicine” approach requires detailed elucidation of the mechanisms connecting genetic alterations of driver genes and aberrant downstream signaling pathways. The regulatory mechanisms of the Hippo pathway and Yes-associated protein/transcriptional co-activator with PDZ binding motif (YAP/TAZ) that have central roles in cancer cell proliferation are not fully understood, reflecting their recent discovery. Nevertheless, emerging evidence has shown that various genetic alterations dysregulate the Hippo pathway and hyperactivate YAP/TAZ in cancers, including head and neck squamous cell carcinoma (HNSCC). Here, we summarize the latest evidence linking genetic alterations and the Hippo pathway in HNSCC, with the aim of contributing to the continued development of precision medicine.

Reversing multi-drug resistance by polymeric metformin to enhance antitumor efficacy of chemotherapy

Multi-drug resistance (MDR) in breast cancer poses a great threat to chemotherapy. The expression and function of the ATP binding cassette (ABC) transporter are the major cause of MDR. Herein, a linear polyethylene glycol (PEI) conjugated with dicyandiamide, which called polymeric metformin (PolyMet), was successfully synthesized as a simple and biocompatible polymer of metformin. PolyMet showed the potential to reverse MDR by inhibiting the efflux of the substrate of ATP-binding cassette (ABC) transporter from DOX resistant MCF-7 cells (MCF-7/DOX). To test its MDR reversing effect, PolyMet was combined with DOX to treat mice carrying MCF-7/DOX xenografts. In order to decrease the toxicities of DOX and delivery PolyMet and DOX to tumor at the same time, PolyMet was complexed with poly-γ-glutamic acid-doxorubicin (PGA-DOX) electrostatically at the optimal ratio of 2:3, which were further coated with lipid membrane to form lipid/PolyMet-(PGA-DOX) nanoparticles (LPPD). The particle size of LPPD was 165.8 nm, and the zeta potential was +36.5 mV. LPPD exhibited favorable cytotoxicity and cellular uptake in MCF-7/DOX. Meanwhile, the bioluminescence imaging and immunohistochemical analysis indicated that LPPD effectively conquered DOX-associated MDR by blocking ABC transporters (ABCB1 and ABCC1) via PolyMet. Remarkably, LPPD significantly inhibited the tumor growth and lowered the systemic toxicity in a murine MCF-7/DOX tumor model. This is the first time to reveal that PolyMet can enhance the anti-tumor efficacy of DOX by dampening ABC transporters and activating the AMPK/mTOR pathway, which is a promising strategy for drug-resistant breast cancer therapy.

Therapeutic approaches for the treatment of head and neck squamous cell carcinoma-An update on clinical trials

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common non-skin cancer with a tobacco consumption and infection with high-risk human papillomavirus (HPV) being major risk factors. Despite advances in numerous therapy modalities, survival rates for HNSCC have not improved considerably; a vast number of clinical outcomes have demonstrated that a combination strategy (the most well-known docetaxel, cisplatin, and 5-fluorouracil) is the most effective treatment choice. Immunotherapy that targets immunological checkpoints is being tested in a number of clinical trials, either alone or in conjunction with chemotherapeutic or targeted therapeutic drugs. Various monoclonal antibodies, such as cetuximab and bevacizumab, which target the EGFR and VEGFR, respectively, as well as other signaling pathway inhibitors, such as temsirolimus and rapamycin, are also being studied for the treatment of HNSCC. We have reviewed the primary targets in active clinical studies in this study, with a particular focus on the medications and drug targets used.

Metformin and Cancer Hallmarks: Molecular Mechanisms in Thyroid, Prostate and Head and Neck Cancer Models

Metformin is the most used drug for type 2 diabetes (T2DM). Its antitumor activity has been described by clinical studies showing reduced risk of cancer development in T2DM patients, as well as management of T2DM compared with those receiving other glucose-lowering drugs. Metformin has a plethora of molecular actions in cancer cells. This review focused on in vitro data on the action mechanisms of metformin on thyroid, prostate and head and neck cancer. AMPK activation regulating specific downstream targets is a constant antineoplastic activity in different types of cancer; however, AMPK-independent mechanisms are also relevant. In vitro evidence makes it clear that depending on the type of tumor, metformin has different actions; its effects may be modulated by different cell conditions (for instance, presence of HPV infection), or it may regulate tissue-specific factors, such as the Na⁺/I⁻ symporter (NIS) and androgen receptors. The hallmarks of cancer are a set of functional features acquired by the cell during malignant development. In vitro studies show that metformin regulates almost all the hallmarks of cancer. Interestingly, metformin is one of these therapeutic agents with the potential to synergize with other chemotherapeutic agents, with low cost, low side effects and high positive consequences. Some questions are still challenging: Are metformin in vitro data able to translate from bench to bedside? Does metformin affect drug resistance? Can metformin be used as a generic anticancer drug for all types of tumors? Which are the specific actions of metformin on the peculiarities of each type of cancer? Several clinical trials are in progress or have been concluded for repurposing metformin as an anticancer drug. The continuous efforts in the field and future in vitro studies will be essential to corroborate clinical trials results and to elucidate the raised questions.

AMP- activated protein kinase (AMPK) promotes breast cancer stemness and drug resistance

Breast cancer stem cells (BCSCs) are a major cause of therapy resistance and tumour progression. Currently, their regulation is not entirely understood. Previous work from our laboratory demonstrated a context-specific pro-tumorigenic role for AMP-activated protein kinase (AMPK) under anchorage-deprivation and mammosphere formation, which are hallmarks of BCSCs. Therefore, we investigated the role of AMPK in the maintenance of BCSC state/function. AMPK depletion reduces serial sphere formation in vitro and tumour initiation in vivo. Intriguingly, tumour-derived cell analysis using stem cell markers and functional assays revealed that AMPK is required for the maintenance of BCSC populations in vivo. AMPK promotes the expression of stemness genes such as NANOG, SOX2 and BMI1 through the transcriptional upregulation of TWIST via promoter acetylation. Further, AMPK-driven stemness plays a critical role in doxorubicin resistance. Significantly, AMPK activity increased after chemotherapy in patient-derived tumour samples alongside an increase in stemness markers. Importantly, AMPK depletion sensitises mouse tumours to doxorubicin treatment. Our work indicates that targeting of AMPK in conjunction with regular chemotherapy is likely to reduce the stem cell pool and improve chemosensitivity in breast cancers.

Summary: AMPK inhibition in conjunction with regular chemotherapy is likely to reduce the stem cell pool and improve chemosensitivity and therapeutic outcomes in breast cancers.

Metformin exerts a synergistic effect with venetoclax by downregulating Mcl-1 protein in acute myeloid leukemia

Background: Recently, one of the specific BH3-mimetics, Venetoclax has been approved by FDA providing new options for newly diagnosed AML patient especially who are unfitted to receive conventional chemotherapy. Though the clinical success of venetoclax has been achieved in clinical outcomes such as complete remission (CR) and overall survival. Acquired resistance to ABT-199 which is induced by the regulation of apoptosis pathway is still an important clinical problem. To this end, the attempt to combine drugs which can reverse the compensatory regulation is urgent.

Methods: In three AML cell lines (KG-1, Kasumi-1 and THP-1), the anti-AML effects of the combination of ABT-199 (Venetoclax) and metformin or the two drugs used alone were compared. CCK8 was used to evaluate the cell viability, and flow cytometry was used to estimate the rate of apoptosis, Western blot method was performed to detect apoptosis-related protein levels. In mice experiments, female BALB/c-nu nude mice were subcutaneously injected with THP-1 cells for subcutaneous tumor formation, and the combined effect of ABT-199 and metformin was tested. The evaluation indicators were tumor size, tumor weight, and Ki67 staining. Mouse body weight and HE staining were detected to evaluate liver damage and adverse drug reactions.

Results: Both in vitro and in vivo experiments showed that compared with metformin or ABT-199 alone, the combined use of the two drugs exerts a synergistic effect on promoting apoptosis, thereby producing a strong anti-leukemia effect. Furthermore, after a short incubation time, ABT-199 swiftly increased the expression level of the anti-apoptotic protein Mcl-1, while the combined use of metformin and ABT-199 significantly reduced the level of Mcl-1. Notably, Metformin significantly downregulates the level of Mcl-1 protein by inhibiting its protein production. To less extent, metformin can also downregulate the expression of another anti-apoptotic protein, BCL-xl.

Conclusion: Metformin downregulates the expression of anti-apoptotic proteins Mcl-1 and Bcl-xl by inhibiting protein production, and shows a synergistic anti-tumor effect with ABT-199 in acute myeloid leukemia.

Metformin inhibits hepatocellular carcinoma development by inducing apoptosis and pyroptosis through regulating FOXO3

This study aimed to expand our understanding of metformin (Met) in inhibiting hepatocellular carcinoma (HCC) progression and to investigate its underlying mechanism. Met was administrated to HCC cells at 5, 10, and 20 μM, after which the cell phenotype was evaluated. RNA-seq cluster analysis was used to screen for target genes modulated by Met. Luciferase activity and ChIP assays were performed to detect the effect of FOXO3 on the transcriptional activation of NLRP3. We evaluated the effect of Met and FOXO3 and on the growth of HCC cells in vivo. Met inhibited HCC cell proliferation and promoted apoptosis. Met also induced pyroptosis of HCC cells. FOXO3 was significantly upregulated by Met treatment, and FOXO3 activated transcription of NLRP3. Cells after Met treatment together with FOXO3 knockdown have a stronger colony formation and migration ability but a lower apoptosis rate compared to the Met treatment alone group. In vivo, Met inhibited HCC tumor growth. The tumors in Met treatment and FOXO3 knockdown group grew faster than in Met treatment group. Thus, Met attenuates HCC cell development by inducing apoptosis and pyroptosis. This effect of metformin is partially dependent on FOXO3 which can activate the transcription of NLRP3.

Metformin generates profound alterations in systemic and tumor immunity with associated antitumor effects

BACKGROUND

Metformin is a commonly used antidiabetic medication which has demonstrated promise as an anticancer agent alone and in combination with conventional treatment regimens. There is increasing evidence that metformin can also generate immunomodulatory effects in solid tumors and is currently being investigated as an adjunct to immune checkpoint inhibitors (ICIs). We hypothesized that metformin would generate a shift in immunity unfavorable to tumor growth and tested this hypothesis in a preclinical model of head and neck cancer.

METHODS

Using a syngeneic mouse model of human papillomavirus-associated head and neck cancer (mEER/MTEC), we tested the impact of metformin on systemic and local immunity and tumor growth velocity. We compared the effects of acute and chronic treatment regimens on immunocyte presence and activation using a combination of flow cytometry and targeted transcriptomic analysis.

RESULTS

Acute metformin exposure generated measurable shifts in systemic myeloid and T-cell populations in non-tumor-bearing mice and decreased myeloid derived suppressor cell (MDSC) levels in tumor draining lymph nodes of tumor-bearing mice. Although metformin decreased regulatory T-cell (T-reg) and MDSC levels and increased CD8+ levels in murine tumors when combined with ICIs, acute metformin exposure was insufficient to generate substantial antitumor activity. Conversely, long-term metformin treatment significantly reduced tumor growth velocity, increased the CD8+/T-reg ratio, increased tumor infiltrating lymphocyte levels and upregulated component genes of the previously validated T-cell inflamed expression profile.

CONCLUSIONS

Metformin generates complex systemic and local immune effects which vary as a function of treatment duration. Combinatorial strategies with ICIs must take into account both the complexity and variability of these effects in order to generate maximal antitumor activity in future clinical trials.

Survival and glycemic control in patients with co-existing squamous cell carcinoma and diabetes mellitus

Aim:

This study examined the impact of diabetes mellitus (DM) on survival in squamous cell carcinoma (SCC) patients, and the impact of SCC on glycemic control.

Materials & methods:

Patients with newly diagnosed SCC with and without DM were matched 1:1 (2007–2017). Overall survival and recurrence-free survival were estimated using the Kaplan–Meier method. Hemoglobin A_1c (HbA_1c) and glucose level during the year following cancer diagnosis were compared using mixed models.

Results:

HbA_1c decreased over time in DM patients (p = 0.04). The 5-year overall survival was 61% in DM patients, compared with 78% in patients without DM (p = 0.004).

Conclusion:

The presence of co-existing DM adversely impacted survival in patients with SCC. SCC did not affect glycemic control.

The objective of this study was to identify the effect of diabetes mellitus (DM) on survival of patients with squamous cell carcinoma (SCC) and to determine whether SCC and its treatment affected glycemic control. We used an institutional cancer registry to identify 190 patients with SCC and grouped them by the presence (n = 95) or absence (n = 95) of DM. Patients were matched by age and year of SCC diagnosis. For individuals with SCC, DM did decrease survival rates, and the diagnosis of SCC did not affect glycemic control.

Combined inhibition of RNA polymerase I and mTORC1/2 synergize to combat oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the major cause of morbidity and mortality in head and neck cancer patients worldwide. This malignant disease is challenging to treat because of the lack of effective curative strategies and the high incidence of recurrence. This study aimed to investigate the efficacy of a single and dual approach targeting ribosome biogenesis and protein translation to treat OSCC associated with the copy number variation (CNV) of ribosomal DNA (rDNA). Here, we found that primary OSCC tumors frequently exhibited a partial loss of 45S rDNA copy number and demonstrated a high susceptibility to CX5461 (a selective inhibitor of RNA polymerase I) and the coadministration of CX5461 and INK128 (a potent inhibitor of mTORC1/2). Combined treatment displayed the promising synergistic effects that induced cell apoptosis and reactive oxygen species (ROS) generation, and inhibited cell growth and proliferation. Moreover, INK128 compromised NHEJ-DNA repair pathway to reinforce the antitumor activity of CX5461. In vivo, the cotreatment synergistically suppressed tumor growth, triggered apoptosis and strikingly extended the survival time of tumor-bearing mice. Additionally, treatment with the individual compounds and coadministration appeared to reduce the incidence of enlarged inguinal lymph nodes. Our study supports that the combination of CX5461 and INK128 is a novel and efficacious therapeutic strategy that can combat this cancer and that 45S rDNA may serve as a useful indicator to predict the efficacy of this cotreatment.

Melanotic neuroectodermal tumor of infancy successfully treated with metformin: A case report

RATIONALE

Melanotic neuroectodermal tumor of infancy (MNTI) is a rare tumor originated from neural crest cells with the potential for recurrence and metastasis. The peak age for the disease is during the first year after birth. The current therapy is primarily surgery. The patient reported here is the first case of MNTI treated with metformin.

PATIENT CONCERNS

A case of a 4-month-old infant with a history of swelling in the mouth for 1 month.

DIAGNOSIS

The tumor was diagnosed using radiology, pathology, and immunohistochemistry, and it was performed with complete surgical resection. Unfortunately, the tumor recurred 3 months after surgery.

INTERVENTIONS

We prescribed metformin for the infant.

OUTCOMES

Currently, after 9 months of treatment, the tumor is well controlled without apparent side effects.

LESSONS

The case presented suggested that metformin may be an underlying therapy for MNTI.

Glucose 6-phosphate dehydrogenase inhibition sensitizes melanoma cells to metformin treatment

Most cancer cells exacerbate the pentose phosphate pathway (PPP) to enhance biosynthetic precursors and antioxidant defenses. Metformin, which is used as a first-line oral drug for the treatment of type 2 diabetes, has been proposed to inhibit the malignant progression of different types of cancers. However, metformin has shown poor efficacy as single agent in several clinical trials. Thus, the aim of the present work was to investigate whether the pharmacological inhibition of G6PDH, the first and rate-limiting enzyme of the PPP, by 6-amino nicotinamide (6-AN) potentiates the antitumoral activity of metformin on different human melanoma cell lines. Our results showed that 6-AN has sensitizing properties to metformin cytotoxicity. The combination of metformin and 6-AN decreased glucose consumption and lactate production, altered the mitochondrial potential and redox balance, and thereby blocked melanoma cell progression, directing cells to apoptosis and necrosis. To our knowledge, this is the first study describing the effect of this combination. Future preclinical studies should be performed to reveal the biological relevance of this finding.

Radiotherapy targeting cancer stem cells "awakens" them to induce tumour relapse and metastasis in oral cancer

Radiotherapy is one of the most common treatments for oral cancer. However, in the clinic, recurrence and metastasis of oral cancer occur after radiotherapy, and the underlying mechanism remains unclear. Cancer stem cells (CSCs), considered the “seeds” of cancer, have been confirmed to be in a quiescent state in most established tumours, with their innate radioresistance helping them survive more easily when exposed to radiation than differentiated cancer cells. There is increasing evidence that CSCs play an important role in recurrence and metastasis post-radiotherapy in many cancers. However, little is known about how oral CSCs cause tumour recurrence and metastasis post-radiotherapy. In this review article, we will first summarise methods for the identification of oral CSCs and then focus on the characteristics of a CSC subpopulation induced by radiation, hereafter referred to as “awakened” CSCs, to highlight their response to radiotherapy and potential role in tumour recurrence and metastasis post-radiotherapy as well as potential therapeutics targeting CSCs. In addition, we explore potential therapeutic strategies targeting these “awakened” CSCs to solve the serious clinical challenges of recurrence and metastasis in oral cancer after radiotherapy.

Impact of metformin on immunological markers: Implication in its anti-tumor mechanism

Metformin, an anti-hyperglycemic drug, has been known to have antitumor properties for around 15 years. Although there are a number of reports attributing the antitumor function of metformin to its impact on energy homeostasis and oxygen re-distribution in tumor microenvironment, detailed mechanisms remain largely unknown. In the past several years, there is an increasing number of publications indicating that metformin can affect various immunological components including lymphocytes, macrophages, cytokines and several key immunological molecules in both human and animal studies. These interesting results appear to be in line with emerging data that suggest associations between immune responses and energy homeostasis/oxygen re-distribution, which may explain effective impacts of metformin on immunotherapies against autoimmune diseases as well as cancers. This review article is to analyse and discuss recent development in the above areas with aim to justify metformin as a new adjuvant for immunotherapy against human cancers. We hope that our summary will help to optimize the application of metformin for various types of human cancers.

Metformin Promotes Beclin1-Dependent Autophagy to Inhibit the Progression of Gastric Cancer

Background

Metformin is the first-line blood sugar control drug for type 2 diabetes, but recent epidemiological studies have shown that it inhibits the growth of a variety of tumours. However, few studies have examined metformin effects on gastric cancer (GC), and the anticancer mechanism has not been fully elucidated.

Materials and Methods

We examined the inhibitory effect of metformin on GC cells by cell proliferation, migration and invasion assay. Transmission electron microscopy, confocal microscopy and Western blotting confirmed that metformin enhanced beclin1-dependent autophagy in gastric cancer cells. TCGA database and tissue chip analysis confirmed the differential expression of beclin1 in GC and adjacent tissues. Relevant functional tests verified the role of beclin1 as a tumour suppressor gene in GC. Western blotting, cell proliferation, cell migration and invasion were used to verify that metformin enhances autophagy in GC cells through the AMPK-mTOR signalling pathway. Xenograft tumour models were constructed to explore the inhibitory effect of metformin and the role of beclin1 as a suppressor on GC in vivo.

Results

In this study, we observed that metformin inhibits proliferation, migration and invasion of GC cells. Metformin could also promote beclin1-dependent autophagy in GC cells. We further discovered that beclin1 expression was downregulated in GC and that its low expression was associated with poor prognosis. Beclin1 acts as a tumour suppressor that inhibits the malignant phenotypes of GC cells in vitro and in vivo. Furthermore, we verified that metformin can upregulate beclin1-mediated autophagy to inhibit GC cells through the AMPK-mTOR signalling pathway.

Conclusion

In summary, the results revealed the role of autophagy in metformin inhibition of gastric cancer and suggest that beclin1 may be a potential target for gastric cancer therapy.

Anticancer mechanisms of metformin: A review of the current evidence

Metformin, a US Food and Drug Administration-approved "star" drug used for diabetes mellitus type 2, has become a topic of increasing interest to researchers due to its anti-neoplastic effects. Growing evidence has demonstrated that metformin may be a promising chemotherapeutic agent, and several clinical trials of metformin use in cancer treatment are ongoing. However, the anti-neoplastic effects of metformin and its underlying mechanisms have not been fully elucidated. In this review, we present the newest findings on the anticancer activities of metformin, and highlight its diverse anticancer mechanisms. Several clinical trials, as well as the limitations of the current evidence are also demonstrated. This review explores the crucial roles of metformin and provides supporting evidence for the repurposing of metformin as a treatment of cancer.

miR-93-5p enhances migration and invasion by targeting RGMB in squamous cell carcinoma of the head and neck

Invasion and metastasis represent the primary causes of therapeutic failure in patients diagnosed with squamous cell carcinoma of the head and neck (SCCHN). Therefore, disease prediction and inhibition of invasion and metastasis are critical for enhancing the survival of patients with SCCHN. Our previous study revealed that increased expression of miR-93-5p is associated with poor prognosis in SCCHN; however, the mechanism underlying the oncogenic functions of miR-93-5p in SCCHN migration and invasion remains unclear. Using qPCR analyses, transwell assays, and scratch tests, we demonstrated that expression of ectopic miR-93-5p induced the migration and invasion of SCCHN, and this was accompanied by corresponding alterations in biomarkers and transcription factors specific for epithelial-mesenchymal transition (EMT). Luciferase reporter assays were used to demonstrate that miR-93-5p directly targeted the 3' UTR of RGMB, and we further found that the tumor-promoting functions of miR-93-5p were partly mediated by targeting RGMB, whose downregulation also promoted the migration and invasion of SCCHN. Overall, our results indicate that miR-93-5p acts as an oncogene in the regulation of migration and invasion by suppressing RGMB in SCCHN. These findings provide novel evidence that miR-93-5p may serve as a valuable predictive biomarker and potential intervention target in patients with SCCHN.

Metformin reduces HGF-induced resistance to alectinib via the inhibition of Gab1

Alectinib is a second-generation anaplastic lymphoma kinase (ALK) inhibitor that has sufficient clinical efficacy and satisfactory safety in ALK-positive non-small cell lung cancer (NSCLC) patients with or without brain metastasis. Alectinib has now become an important drug in the first-line treatment of advanced ALK-positive NSCLC; however, resistance is almost inevitable. The increased expression of hepatocyte growth factor (HGF) and its physiological receptor tyrosine kinase MET have been shown to be linked to acquired resistance to various tyrosine kinase inhibitors (TKIs), and this phenomenon has been observed in some ALK-positive NSCLC tumour tissues. In this study, we found that HGF levels in the culture supernatant of an ALK-positive cell line tended to increase with time and could be further increased by alectinib in a time-dependent manner. Exogenous or endogenous HGF did not cause resistance to the ALK/MET double-targeted small molecule inhibitor crizotinib, but it was an important cause of alectinib resistance. Furthermore, Gab1 was a key effector in the HGF/MET signal transduction pathway that mediated alectinib resistance. The antidiabetic drug metformin combined with alectinib overcame alectinib resistance triggered by HGF/MET through disrupting the complex between MET and Gab1, thereby inhibiting Gab1 phosphorylation and the activation of downstream signal transduction pathways. These results suggest that metformin combined with alectinib may be useful for overcoming alectinib resistance induced by the activation of the HGF/MET signalling pathway and improving the efficacy of alectinib.

Metformin as Potential Therapy for High-Grade Glioma

Metformin (MET), 1,1-dimethylbiguanide hydrochloride, is a biguanide drug used as the first-line medication in the treatment of type 2 diabetes. The recent years have brought many observations showing metformin in its new role. The drug, commonly used in the therapy of diabetes, may also find application in the therapy of a vast variety of tumors. Its effectiveness has been demonstrated in colon, breast, prostate, pancreatic cancer, leukemia, melanoma, lung and endometrial carcinoma, as well as in gliomas. This is especially important in light of the poor options offered to patients in the case of high-grade gliomas, which include glioblastoma (GBM). A thorough understanding of the mechanism of action of metformin can make it possible to discover new drugs that could be used in neoplasm therapy.