Metformin inhibits cell proliferation, migration and invasion by attenuating CSC function mediated by deregulating miRNAs in pancreatic cancer cells

Machine Learning Helps Identify New Drug Mechanisms in Triple-Negative Breast Cancer

This paper demonstrates the ability of mach- ine learning approaches to identify a few genes among the 23,398 genes of the human genome to experiment on in the laboratory to establish new drug mechanisms. As a case study, this paper uses MDA-MB-231 breast cancer single-cells treated with the antidiabetic drug metformin. We show that mixture-model-based unsupervised methods with validation from hierarchical clustering can identify single-cell subpopulations (clusters). These clusters are characterized by a small set of genes (1% of the genome) that have significant differential expression across the clusters and are also highly correlated with pathways with anticancer effects driven by metformin. Among the identified small set of genes associated with reduced breast cancer incidence, laboratory experiments on one of the genes, CDC42, showed that its downregulation by metformin inhibited cancer cell migration and proliferation, thus validating the ability of machine learning approaches to identify biologically relevant candidates for laboratory experiments. Given the large size of the human genome and limitations in cost and skilled resources, the broader impact of this work in identifying a small set of differentially expressed genes after drug treatment lies in augmenting the drug-disease knowledge of pharmacogenomics experts in laboratory investigations, which could help establish novel biological mechanisms associated with drug response in diseases beyond breast cancer.

Epigenetic effects of metformin: From molecular mechanisms to clinical implications

There is a growing body of evidence that links epigenetic modifications to type 2 diabetes. Researchers have more recently investigated effects of commonly used medications, including those prescribed for diabetes, on epigenetic processes. This work reviews the influence of the widely used antidiabetic drug metformin on epigenomics, microRNA levels and subsequent gene expression, and potential clinical implications. Metformin may influence the activity of numerous epigenetic modifying enzymes, mostly by modulating the activation of AMP-activated protein kinase (AMPK). Activated AMPK can phosphorylate numerous substrates, including epigenetic enzymes such as histone acetyltransferases (HATs), class II histone deacetylases (HDACs) and DNA methyltransferases (DNMTs), usually resulting in their inhibition; however, HAT1 activity may be increased. Metformin has also been reported to decrease expression of multiple histone methyltransferases, to increase the activity of the class III HDAC SIRT1 and to decrease the influence of DNMT inhibitors. There is evidence that these alterations influence the epigenome and gene expression, and may contribute to the antidiabetic properties of metformin and, potentially, may protect against cancer, cardiovascular disease, cognitive decline and aging. The expression levels of numerous microRNAs are also reportedly influenced by metformin treatment and may confer antidiabetic and anticancer activities. However, as the reported effects of metformin on epigenetic enzymes act to both increase and decrease histone acetylation, histone and DNA methylation, and gene expression, a significant degree of uncertainty exists concerning the overall effect of metformin on the epigenome, on gene expression, and on the subsequent effect on the health of metformin users.

Metformin Alters Gut Microbiota of Healthy Mice: Implication for Its Potential Role in Gut Microbiota Homeostasis

In recent years, the first-line anti-diabetic drug metformin has been shown to be also useful for the treatment of other diseases like cancer. To date, few reports were about the impact of metformin on gut microbiota. To fully understand the mechanism of action of metformin in treating diseases other than diabetes, it is especially important to investigate the impact of long-term metformin treatment on the gut microbiome in non-diabetic status. In this study, we treated healthy mice with metformin for 30 days, and observed 46 significantly changed gut microbes by using the 16S rRNA-based microbiome profiling technique. We found that microbes from the Verrucomicrobiaceae and Prevotellaceae classes were enriched, while those from Lachnospiraceae and Rhodobacteraceae were depleted. We further compared the altered microbiome profile with the profiles under various disease conditions using our recently developed comparative microbiome tool known as MicroPattern. Interestingly, the treatment of diabetes patients with metformin positively correlates with colon cancer and type 1 diabetes, indicating a confounding effect on the gut microbiome in patients with diabetes. However, the treatment of healthy mice with metformin exhibits a negative correlation with multiple inflammatory diseases, indicating a protective anti-inflammatory role of metformin in non-diabetes status. This result underscores the potential effect of metformin on gut microbiome homeostasis, which may contribute to the treatment of non-diabetic diseases.

Mitochondrial dysfunction induces the invasive phenotype, and cell migration and invasion, through the induction of AKT and AMPK pathways in lung cancer cells

Mitochondria are well known for their important roles in oxidative phosphorylation, amino acid metabolism, fatty acid oxidation and ion homeostasis. Although the effects of mitochondrial dysfunction on tumorigenesis in various cancer cells have been reported, the correlation between mitochondrial dysfunction and epithelial‑to‑mesenchymal transition (EMT) in lung cancer development and metastasis has not been well elucidated. In the present study, the effects of mitochondrial dysfunction on EMT and migration in lung cancer cells were investigated using inhibitors of mitochondrial respiration, oligomycin A and antimycin A. Oligomycin A and antimycin A induced distinct mesenchymal‑like morphological features in H23, H1793 and A549 lung cancer cells. In addition, they decreased the expression levels of the epithelial marker protein E‑cadherin, but increased the expression levels of the mesenchymal marker proteins Vimentin, Snail and Slug. The results of immunofluorescence staining indicated that oligomycin A and antimycin A downregulated cortical E‑cadherin expression and upregulated the expression of Vimentin. In addition, oligomycin A and antimycin A increased the migration and invasion of A549 lung cancer cells, and promoted the expression levels of phosphorylated (p)‑protein kinase B (AKT) and p‑AMP‑activated protein kinase (AMPK). Notably, the production of reactive oxygen species by oligomycin A and antimycin A did not affect the expression of EMT protein markers. Conversely, treatment with the AKT inhibitor wortmannin and the AMPK inhibitor Compound C upregulated E‑cadherin and downregulated Vimentin expression. These results suggested that oligomycin A and antimycin A may induce migration and invasion of lung cancer cells by inducing EMT via the upregulation of p‑AKT and p‑AMPK expression.

Glyoxalase 1 sustains the metastatic phenotype of prostate cancer cells via EMT control

Metastasis is the primary cause of death in prostate cancer (PCa) patients. Effective therapeutic intervention in metastatic PCa is undermined by our poor understanding of its molecular aetiology. Defining the mechanisms underlying PCa metastasis may lead to insights into how to decrease morbidity and mortality in this disease. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a potent precursor of advanced glycation end products (AGEs). Hydroimidazolone (MG-H1) and argpyrimidine (AP) are AGEs originating from MG-mediated post-translational modification of proteins at arginine residues. AP is involved in the control of epithelial to mesenchymal transition (EMT), a crucial determinant of cancer metastasis and invasion, whose regulation mechanisms in malignant cells are still emerging. Here, we uncover a novel mechanism linking Glo1 to the maintenance of the metastatic phenotype of PCa cells by controlling EMT by engaging the tumour suppressor miR-101, MG-H1-AP and TGF-β1/Smad signalling. Moreover, circulating levels of Glo1, miR-101, MG-H1-AP and TGF-β1 in patients with metastatic compared with non-metastatic PCa support our in vitro results, demonstrating their clinical relevance. We suggest that Glo1, together with miR-101, might be potential therapeutic targets for metastatic PCa, possibly by metformin administration.

Metformin influences drug sensitivity in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive, highly metastatic malignancy and accounts for 85% of pancreatic cancers. PDAC patients have poor prognosis with a five-year survival of only 5-10% after diagnosis and treatment. Pancreatic cancer has been associated with type II diabetes as the frequency of recently diagnosed diabetics that develop pancreatic cancer within a 10-year period of initial diagnosis of diabetes in increased in comparison to non-diabetic patients. Metformin is a very frequently prescribed drug used to treat type II diabetes. Metformin acts in part by stimulating AMP-kinase (AMPK) and results in the suppression of mTORC1 activity and the induction of autophagy. In the following studies, we have examined the effects of metformin in the presence of various chemotherapeutic drugs, signal transduction inhibitors and natural products on the growth of three different PDAC lines. Metformin, by itself, was not effective at suppressing growth of the pancreatic cancer cell lines at concentration less than 1000 nM, however, in certain PDAC lines, a suboptimal dose of metformin (250 nM) potentiated the effects of various chemotherapeutic drugs used to treat pancreatic cancer (e.g., gemcitabine, cisplatin, 5-fluorouracil) and other cancer types (e.g., doxorubicin, docetaxel). Furthermore, metformin could increase anti-proliferative effects of mTORC1 and PI3K/mTOR inhibitors as well as natural products such as berberine and the anti-malarial drug chloroquine in certain PDAC lines. Thus, metformin can enhance the effects of certain drugs and signal transduction inhibitors which are used to treat pancreatic and various other cancers.

TRPV4-Mediated Anti-nociceptive Effect of Suberanilohydroxamic Acid on Mechanical Pain

Biological effects of suberanilohydroxamic acid (SAHA) have mainly been observed in the context of tumor suppression via epigenetic mechanisms, but other potential outcomes from its use have also been proposed in different fields such as pain modulation. Here, we tried to understand whether SAHA modulates specific pain modalities by a non-epigenetic unknown mechanism. From 24 h Complete Freund's Adjuvant (CFA)-inflamed hind paws of mice, mechanical and thermal inflammatory pain indices were collected with or without immediate intraplantar injection of SAHA. To examine the action of SAHA on sensory receptor-specific pain, transient receptor potential (TRP) ion channel-mediated pain indices were collected in the same manner of intraplantar treatment. Activities of primarily cultured sensory neurons and heterologous cells transfected with TRP channels were monitored to determine the molecular mechanism underlying the pain-modulating effect of SAHA. As a result, immediate and localized pretreatment with SAHA, avoiding an epigenetic intervention, acutely attenuated mechanical inflammatory pain and receptor-specific pain evoked by injection of a TRP channel agonist in animal models. We show that a component of the mechanisms involves TRPV4 inhibition based on in vitro intracellular Ca²⁺ imaging and electrophysiological assessments with heterologous expression systems and cultured sensory neurons. Taken together, the present study provides evidence of a novel off-target action and its mechanism of SAHA in its modality-specific anti-nociceptive effect and suggests the utility of this compound for pharmacological modulation of pain.

Metformin inhibits ovarian cancer via decreasing H3K27 trimethylation

Metformin has been used for the treatment of type II diabetes mellitus for decades. Recently, used of metformin in the therapy of diverse human cancer types has received widespread attention, while the underlying mechanisms have been not fully elucidated. In the current study, 5-ethynyl-20-de-oxyuridine assay to detect cell proliferation, flow cytometry to detect apoptosis, scratch wound healing and Transwell migration assay to detect cell migration capacity. The current study reported that metformin inhibited cell proliferation and migration, and promoted apoptosis in ovarian cancer cells, particularly under normoglycemic conditions in vitro. Metformin treatment significantly promoted the phosphorylation of AMP-activated protein kinase (AMPK), and reduced histone H3 lysine 27 trimethylation (H3K27me3) and polycomb repressor complex 2 (PRC2) levels. Additionally, overexpression of EZH2 to increase H3K27me3 abrogated the effect of metformin on the cell proliferation, migration and apoptosis in SKOV3 and ES2 cells. Similar to metformin, another AMPK agonist, 2-deoxy-D-glucose, reduced the H3K27me3 level and PRC2 expression. In cells pretreated with Compound C, an AMPK inhibitor, metformin was not able to induce AMPK phosphorylation or reduce H3K27me3. Metformin-mediated AMPK activation and H3K27me3 inhibition were more robust in cells exposed to low glucose (5.5 mM) compared with those exposed to high glucose (25 mM). These findings implicate H3K27me3 repression mediated by AMPK phosphorylation in the antitumor effect of metformin in ovarian cancer, indicating that metformin alters epigenetic modifications by targeting PRC2 and supports the use of metformin in treatment of patients with epithelial ovarian cancer without diabetes.

Metformin-induced anticancer activities: recent insights

Metformin is a widely used antidiabetic drug, and there is evidence among diabetic patients that metformin is a chemopreventive agent against multiple cancers. There is also evidence in human studies that metformin is a cancer chemotherapeutic agent, and several clinical trials that use metformin alone or in combination with other drugs are ongoing. In vivo and in vitro cancer cell culture studies demonstrate that metformin induces both AMPK-dependent and AMPK-independent genes/pathways that result in inhibition of cancer cell growth and migration and induction of apoptosis. The effects of metformin in cancer cells resemble the patterns observed after treatment with drugs that downregulate specificity protein 1 (Sp1), Sp3 and Sp4 or by knockdown of Sp1, Sp3 and Sp4 by RNA interference. Studies in pancreatic cancer cells clearly demonstrate that metformin decreases expression of Sp1, Sp3, Sp4 and pro-oncogenic Sp-regulated genes, demonstrating that one of the underlying mechanisms of action of metformin as an anticancer agent involves targeting of Sp transcription factors. These observations are consistent with metformin-mediated effects on genes/pathways in many other tumor types.

Sirolimus and metformin synergistically inhibit hepatocellular carcinoma cell proliferation and improve long-term survival in patients with HCC related to hepatitis B virus induced cirrhosis after liver transplantation

Immunosuppressive agents used postoperatively after liver transplantation (LT) for hepatocellular carcinoma (HCC) favor recurrence and metastasis. Therefore, new effective immunosuppressants are needed. This retrospective study assessed combined sirolimus and metformin on survival of HCC patients after LT. In 2001-2013, 133 HCC patients with LT were divided into four groups: sirolimus and metformin combination (Sir+Met), sirolimus monotherapy (Sir), other immunosuppressants in diabetes mellitus (DM) patients without metformin (No Sir with DM), and other immunosuppressants in patients without DM (No Sir without DM). Kaplan-Meier and Log-rank tests were used to assess survival. Cell proliferation and tumor xenograft assays were performed to disclose the mechanisms underlying the sirolimus and metformin effects. The Sir+Met group showed significantly prolonged survival compared to the other groups. The most significant cytotoxicity was seen in the Sir+Met group, with significantly decreased levels of phosphorylated PI3K, AKT, AMPK, mTOR, 4EBP1 and S6K, compared with the other groups. In agreement, Sir+Met had the highest suppressive effect on tumor growth among all groups (P<0.01). In summary, Sir+Met treatment significantly prolonged survival, likely by suppressing cell proliferation. Therefore, this combination could represent a potential routine-regimen for patients post LT.

Impact of diabetes mellitus on the risk and survival of nasopharyngeal carcinoma: a meta-analysis

Background

Diabetes mellitus (DM) has been identified to be both a risk factor and a prognostic factor in a variety of malignancies, but its association with the risk and outcome of nasopharyngeal carcinoma (NPC) is still unclear. To elucidate this issue, we systematically reviewed the evidence concerning the association between DM status and NPC.

Materials and methods

We identified studies by a literature search of PubMed, Embase, and ISI Web of Knowledge through May 31, 2017, and by searching the reference lists of pertinent articles. Odds ratios (ORs) and hazard ratios (HRs) with 95% CIs were used to estimate the effect size. Heterogeneity across studies was evaluated by the Cochran’s Q and I² statistics.

Results

A total of nine studies were included. Four studies with a total sample size of 221,611 reported the effect of DM on NPC risk, and the other five studies with a sample size of 9,442 reported the impact of DM on survival in NPC patients. All included studies were retrospective, and mostly conducted in Asian populations. Meanwhile, condition of metformin usage was not considered in all studies. A pooled OR of 0.65 (95% CI: 0.43–0.98, P=0.04) revealed an inverse association between DM and NPC. Additionally, pooled analyses of studies investigating the prognosis value of DM revealed that preexisting DM had no effect on overall survival (HR =1.17, 95% CI: 0.94–1.46, P=0.16), local recurrence-free survival (HR =1.16, 95% CI: 0.80–1.67, P=0.44), and distant metastasis-free survival (HR =1.14, 95% CI: 0.92–1.40, P=0.22).

Conclusion

Our results suggested that DM patients might have decreased NPC risk, and have little impact on prognosis of NPC patients. This conclusion should be limited to Asian population. Our results also suggest that more attention should be paid to metformin medication in further studies in order to clarify whether the effects of DM on NPC risk and prognosis are influenced by the anticancer effect of metformin.

Metformin inhibits the migration and invasion of esophageal squamous cell carcinoma cells by downregulating the protein kinase B signaling pathway

Previous studies have suggested that metformin, a biguanide family member widely used as an oral antidiabetic drug, may inhibit proliferation and induce apoptosis in certain types of cancer cell. However, the molecular mechanisms underlying metformin-associated anticancer effects, and in particular antimetastatic effects, remain to be fully understood. The present study assessed the efficacy of metformin in inhibiting the migration and invasion of the esophageal carcinoma cell line EC109, and evaluated the effect of metformin on the protein kinase B (AKT) signaling pathway. EC109 cells were treated with 0, 5, 10 or 20 mM metformin during the logarithmic growth phase. A Transwell assay and western blot analysis revealed that metformin inhibited the migration and invasion of EC109 cells, nuclear factor-κB activation, matrix metallopeptidase 9 and N-cadherin expression in a phosphorylated-AKT dependent manner. These results suggested that metformin inhibits the migration and invasion of human esophageal carcinoma cells by suppressing AKT phosphorylation and regulating the expression of migration- and invasion-associated genes.

Targeting cancer stem cells in the clinic: Current status and perspectives

Resistance to chemotherapy and cancer relapse are major clinical challenges attributed to a sub population of cancer stem cells (CSCs). The concept of CSCs has been the subject of intense research by the oncology community since evidence for their existence was first published over twenty years ago. Emerging data indicates that they are also able to evade novel therapies such as targeted agents, immunotherapies and anti-angiogenics. The inability to appropriately identify and isolate CSCs is a major hindrance to the field and novel technologies are now being utilized. Agents that target CSC-associated cell surface receptors and signaling pathways have generated promising pre-clinical results and are now entering clinical trial. Here we discuss and evaluate current therapeutic strategies to target CSCs.

Metformin as an anti-cancer agent: actions and mechanisms targeting cancer stem cells

Metformin, a first line medication for type II diabetes, initially entered the spotlight as a promising anti-cancer agent due to epidemiologic reports that found reduced cancer risk and improved clinical outcomes in diabetic patients taking metformin. To uncover the anti-cancer mechanisms of metformin, preclinical studies determined that metformin impairs cellular metabolism and suppresses oncogenic signaling pathways, including receptor tyrosine kinase, PI3K/Akt, and mTOR pathways. Recently, the anti-cancer potential of metformin has gained increasing interest due to its inhibitory effects on cancer stem cells (CSCs), which are associated with tumor metastasis, drug resistance, and relapse. Studies using various cancer models, including breast, pancreatic, prostate, and colon, have demonstrated the potency of metformin in attenuating CSCs through the targeting of specific pathways involved in cell differentiation, renewal, metastasis, and metabolism. In this review, we provide a comprehensive overview of the anti-cancer actions and mechanisms of metformin, including the regulation of CSCs and related pathways. We also discuss the potential anti-cancer applications of metformin as mono- or combination therapies.

Metformin enhances TRAIL-induced apoptosis by Mcl-1 degradation via Mule in colorectal cancer cells

Metformin is an anti-diabetic drug with a promising anti-cancer potential. In this study, we show that subtoxic doses of metformin effectively sensitize human colorectal cancer (CRC) cells to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), which induces apoptosis. Metformin alone did not induce apoptosis, but significantly potentiated TRAIL-induced apoptosis in CRC cells. CRC cells treated with metformin and TRAIL showed activation of the intrinsic and extrinsic pathways of caspase activation. We attempted to elucidate the underlying mechanism, and found that metformin significantly reduced the protein levels of myeloid cell leukemia 1 (Mcl-1) in CRC cells and, the overexpression of Mcl-1 inhibited cell death induced by metformin and/or TRAIL. Further experiments revealed that metformin did not affect mRNA levels, but increased proteasomal degradation and protein stability of Mcl-1. Knockdown of Mule triggered a significant decrease of Mcl-1 polyubiquitination. Metformin caused the dissociation of Noxa from Mcl-1, which allowed the binding of the BH3-containing ubiquitin ligase Mule followed by Mcl-1ubiquitination and degradation. The metformin-induced degradation of Mcl-1 required E3 ligase Mule, which is responsible for the polyubiquitination of Mcl-1. Our study is the first report indicating that metformin enhances TRAIL-induced apoptosis through Noxa and favors the interaction between Mcl-1 and Mule, which consequently affects Mcl-1 ubiquitination.

Alveolar rhabdomyosarcoma: morphoproteomics and personalized tumor graft testing further define the biology of PAX3-FKHR(FOXO1) subtype and provide targeted therapeutic options

Alveolar rhabdomyosarcoma (ARMS) represents a block in differentiation of malignant myoblasts. Genomic events implicated in the pathogenesis of ARMS involve PAX3-FKHR (FOXO1) or PAX7-FKHR (FOXO1) translocation with corresponding fusion transcripts and fusion proteins. Commonalities in ARMS include uncontrollable proliferation and failure to differentiate. The genomic-molecular correlates contributing to the etiopathogenesis of ARMS incorporate PAX3-FKHR (FOXO1) fusion protein stimulation of the IGF-1R, c-Met and GSK3-β pathways. With sequential morphoproteomic profiling on such a case in conjunction with personalized tumor graft testing, we provide an expanded definition of the biology of PAX3-FKHR (FOXO1) ARMS that integrates genomics, proteomics and pharmacogenomics. Moreover, therapies that target the genomic and molecular biology and lead to tumoral regression and/or tumoral growth inhibition in a xenograft model of ARMS are identified.

Morphoproteomics and biomedical analytics confirm the mTORC2/Akt pathway as a resistance signature and activated ERK and STAT3 as concomitant prosurvival/antiapoptotic pathways in metastatic renal cell carcinoma (RCC) progressing on rapalogs: pathogenesis and therapeutic options

Background

It has been proposed that resistance to rapalog therapies in renal cell carcinoma (RCC) is due to adaptive switching from mammalian target of rapamycin complex 1 (mTORC1) to mTORC2.

Objective

To combine phosphoprotein staining and applied biomedical analytics to investigate resistance signatures in patients with metastatic RCC progressing on rapalog therapies.

Design

We applied morphoproteomic analysis to biopsy specimens from nine patients with metastatic RCC who continued to show clinical progression of their tumors while being treated with a rapalog.

Results

In patients who were on temsirolimus or everolimus at the time of biopsy, a moderate to strong expression of phosphorylated (p)-mTOR (Ser 2448) in the nuclear compartment with concomitant expression of p-Akt (Ser 473) confirmed the mTORC2 pathway. Concomitant moderate to strong nuclear expression of p-ERK 1/2 (Thr202/Tyr204) and p-STAT3 (Tyr705) was confirmed. Histopathologic changes of hypoxic-type coagulative necrosis in 5 cases as well as identification of insulin-like growth factor-1 receptor (IGF-1R) expression and histone methyltransferase EZH2 in all tumors studied suggested that hypoxia also contributed to the resistance signature. Biomedical analytics provided insight into therapeutic options that could target such adaptive and pathogenetic mechanisms.

Conclusions

Morphoproteomics and biomedical analytics confirm mTORC2/Akt as a resistance signature to rapalog therapy in metastatic RCC and demonstrate activation of the prosurvival ERK and STAT3 pathways and involvement of hypoxic pathways that contribute to pathogenesis of such adaptive resistance. These results highlight the need for a novel combinatorial therapeutic approach in metastatic RCC progressing on rapalogs.

Targeting Pancreatic Cancer Cell Plasticity: The Latest in Therapeutics

Mortality remains alarmingly high for patients diagnosed with pancreatic ductal adenocarcinoma (PDAC), with 93% succumbing to the disease within five years. The vast majority of PDAC cases are driven by activating mutations in the proto-oncogene KRAS, which results in constitutive proliferation and survival signaling. As efforts to target RAS and its downstream effectors continue, parallel research aimed at identifying novel targets is also needed in order to improve therapeutic options and efficacy. Recent studies demonstrate that self-renewing cancer stem cells (CSCs) contribute to metastatic dissemination and therapy failure, the causes of mortality from PDAC. Here, we discuss current challenges in PDAC therapeutics, highlight the contribution of mesenchymal/CSC plasticity to PDAC pathogenesis, and propose that targeting the drivers of plasticity will prove beneficial. Increasingly, intrinsic oncogenic and extrinsic pro-growth/survival signaling emanating from the tumor microenvironment (TME) are being implicated in the de novo generation of CSC and regulation of tumor cell plasticity. An improved understanding of key regulators of PDAC plasticity is providing new potential avenues for targeting the properties associated with CSC (including enhanced invasion and migration, metastatic outgrowth, and resistance to therapy). Finally, we describe the growing field of therapeutics directed at cancer stem cells and cancer cell plasticity in order to improve the lives of patients with PDAC.

Metformin and cancer: An existing drug for cancer prevention and therapy

Metformin is a standard clinical drug used to treat type 2 diabetes mellitus (T2DM) and polycystic ovary syndrome. Recently, epidemiological studies and meta-analyses have revealed that patients with T2DM have a lower incidence of tumor development than healthy controls and that patients diagnosed with cancer have a lower risk of mortality when treated with metformin, demonstrating an association between metformin and tumorigenesis. In vivo and in vitro studies have revealed that metformin has a direct antitumor effect, which may depress tumor proliferation and induce the apoptosis, autophagy and cell cycle arrest of tumor cells. The mechanism underpinning the antitumor effect of metformin has not been well established. Studies have demonstrated that reducing insulin and insulin-like growth factor levels in the peripheral blood circulation may lead to the inhibition of phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin (mTOR) signaling or activation of AMP-activated protein kinase, which inhibits mTOR signaling, a process that may be associated with the antitumor effect of metformin. The present review primarily focuses on the recent progress in understanding the function of metformin in tumor development.

Synergistic Chemopreventive and Therapeutic Effects of Co-drug UA-Met: Implication in Tumor Metastasis

The anticancer properties of ursolic acid (UA) and metformin (Met) have been well demonstrated. However, whether these compounds can act synergistically to prevent and treat cancer is not known. We present in this study, the synergism between UA and Met, and that of a new codrug made of UA and Met (UA-Met) against several cancer cell lines. The combination of high concentration of UA (25, 50, 75, 100 μM) and Met (5, 10, 20, 40 mM) resulted in synergetic cytotoxicity on MDA-MB-231 and MCF-7 cells (CI < 0.8). Molecular and cellular studies showed that codrug UA-Met significantly inhibited the invasion (∼55.3 ± 2.74%) and migration (∼52.4 ± 1.57%) of TGF-β induced breast cancer MDA-MB-231 and MCF-7 cells in vitro at low concentration of 10 μM. These effects were accompanied by down-regulation of CXCR4, uPA, vimentin, E-cadherin, N-cadherin, and MMP-2/9 proteins expression and regulation of the AMPK/m-TOR signaling pathways as expected from UA and Met. Moreover, UA-Met could reduce the progression of pulmonary metastasis by 4T1 cells (63.4 ± 3.52%) without influencing the glucose blood level in mice. Our study suggests that the codrug UA-Met is safe and effective in preventing cancer metastasis and possibly treatment of cancer.

MicroRNA-429 decreases the invasion ability of gastric cancer cell line BGC-823 by downregulating the expression of heparanase

The present study aimed to measure the expression of microRNA (miRNA/miR) −429 in gastric cancer and investigate the associated mechanism of action. A total of 30 patients with gastric cancer who received radical or palliative resection at Jining No. 1 People's Hospital between January-October 2016 were included in the present study. Resected gastric cancer and tumor-adjacent tissues were resected. Gastric cancer BGC-823 cells were transfected with miR-429 mimics to induce the overexpression of miR-429, or transfected with small interfering (si)RNA of heparanase (HPSE) for the silencing of HPSE. Reverse transcription-quantitative polymerase chain reaction was used to measure the expression of miR-429 or HPSE mRNA. Western blotting was employed to determine the protein expression of HPSE. Cell-Counting Kit-8 assay was carried out to test cell proliferation and a Transwell assay was used to determine cell invasion ability. Expression of HPSE mRNA and protein in gastric cancer tissues was increased compared with tumor-adjacent tissues. Reduced expression of miR-429 in gastric cancer tissues may be associated with the targeting of HPSE mRNA by miR-429. Overexpression of miR-429 inhibited the transcription and translation of the HPSE gene. However, overexpression of miR-429 did not affect the proliferation of gastric cancer cells. Notably, overexpression of miR-429 reduced the invasion ability of gastric cancer cells. Transfection with HPSE siRNA decreased the expression of the HPSE protein in BGC-823 cells and inhibited the occurrence and development of gastric cancer by reducing the invasion ability of the cells. The present study demonstrated that expression of miR-429 in gastric cancer tissues was significantly reduced compared with tumor-adjacent tissues. As a tumor-suppressor gene, miR-429 decreases the invasion ability of gastric cancer cells by downregulating the expression of HSPE.

Arsenic trioxide inhibits cell growth and motility via up-regulation of let-7a in breast cancer cells

Arsenic trioxide (ATO) has been reported to exert its anti-cancer activities in human cancers. However, the molecular mechanism of ATO-triggered anti-tumor activity has not been fully elucidated. Recently, multiple studies demonstrated that ATO could regulate miRNAs in human cancers. Therefore, in this study, we investigated whether ATO regulated let-7a in breast cancer cells. We found that ATO upregulated let-7a level in breast cancer cells. We also found that up-regulation of let-7a inhibited cell growth and induced apoptosis and retarded cell migration and invasion. We also observed that up-regulation of let-7a enhanced cell growth inhibition and invasion suppression induced by ATO treatment. Our findings suggest that ATO suppressed cell growth, stimulated apoptosis, and retarded cell invasion partly via upregulation of let-7a in breast cancer cells. Our study provides a new anti-tumor mechanism of ATO treatment in breast cancer.

Metformin depresses overactivated Notch1/Hes1 signaling in colorectal cancer patients with type 2 diabetes mellitus

The function of metformin in colorectal cancer (CRC) patients with diabetes mellitus (DM) remains a controversial topic because studies are increasingly focusing on epidemiologic features. We examined Notch1/Hes1 signaling in CRC with DM (DM-CRC) and investigated alterations in signaling caused by metformin treatment. For this purpose, information on pathological characteristics was collected from each patient. The proliferation of epithelium labeled with proliferating cell nuclear antigen and the differentiation of goblet cells were investigated using immunohistochemistry and periodic acid-Schiff staining, respectively. The factors involved in Notch1/Hes1 signaling were detected using qRT-PCR and western blot. In our study, we found that lymphatic metastasis, pTNM staging, and the carcinoembryonic antigen level were significantly different between groups. The depth of crypts and the rate of proliferating cell nuclear antigen-positive cells were distinctly higher in DM-CRC and patients who were managed with insulin. Moreover, the goblet cell differentiation rate was decreased in DM-CRC. The expression of Dll1, Notch1, Math1, and RBP-Jκ was increased in DM-CRC, whereas the expression of Dll4 and Hes1 was decreased in this group in normal tissue. In CRC tissue, the expression of Dll1 and Notch1 was clearly higher than that in DM-CRC. Furthermore, the trend in these changes was aggravated with insulin management and alleviated with metformin treatment. In conclusion, the abnormal cell proliferation and differentiation observed in DM-CRC are correlated with overactivated Notch1/Hes1 signaling, which is potentially relieved by metformin treatment.

Therapeutic potential of the metabolic modulator Metformin on osteosarcoma cancer stem-like cells

PURPOSE

Osteosarcoma is the most common primary bone tumour appearing in children and adolescents. Recent studies demonstrate that osteosarcoma possesses a stem-like cell subset, so-called cancer stem-like cells, refractory to conventional chemotherapeutics and pointed out as responsible for relapses frequently observed in osteosarcoma patients. Here, we explored the therapeutic potential of Metformin on osteosarcoma stem-like cells, alone and as a chemosensitizer of doxorubicin.

METHODS

Stem-like cells were isolated from human osteosarcoma cell lines, MNNG/HOS and MG-63, using the sphere-forming assay. Metformin cytotoxicity alone and combined with doxorubicin were evaluated using MTT/BrdU assays. Protein levels of AMPK and AKT were evaluated by Western Blot. Cellular metabolic status was assessed based on [¹⁸F]-FDG uptake and lactate production measurements. Sphere-forming efficiency and expression of pluripotency transcription factors analysed by qRT-PCR were tested as readout of Metformin effects on stemness features.

RESULTS

Metformin induced a concentration-dependent decrease in the metabolic activity and proliferation of sphere-forming cells and improved doxorubicin-induced cytotoxicity. This drug also down-regulated the expression of master regulators of pluripotency (OCT4, SOX2, NANOG), and decreased spheres' self-renewal ability. Metformin effects on mitochondria led to the activation and phosphorylation of the energetic sensor AMPK along with an upregulation of the pro-survival AKT pathway in both cell populations. Furthermore, Metformin-induced mitochondrial stress increased [¹⁸F]-FDG uptake and lactate production in parental cells but not in the quiescent stem-like cells, suggesting the inability of the latter to cope with the energy crisis induced by metformin.

CONCLUSIONS

This preclinical study suggests that Metformin may be a potentially useful therapeutic agent and chemosensitizer of osteosarcoma stem-like cells to doxorubicin.

The expanding role of metformin in cancer: an update on antitumor mechanisms and clinical development

Metformin has been used for nearly a century to treat type 2 diabetes mellitus. Epidemiologic studies first identified the association between metformin and reduced risk of several cancers. The anticancer mechanisms of metformin involve both indirect or insulin-dependent pathways and direct or insulin-independent pathways. Preclinical studies have demonstrated metformin's broad anticancer activity across a spectrum of malignancies. Prospective clinical trials involving metformin in the chemoprevention and treatment of cancer now number in the hundreds. We provide an update on the anticancer mechanisms of metformin and review the results thus far available from prospective clinical trials investigating metformin's efficacy in cancer.

Diabetic concentrations of metformin inhibit platelet-mediated ovarian cancer cell progression

Clinical studies have suggested a survival benefit in ovarian cancer patients with type 2 diabetes mellitus taking metformin, however the mechanism by which diabetic concentrations of metformin could deliver this effect is still poorly understood. Platelets not only represent an important reservoir of growth factors and angiogenic regulators, they are also known to participate in the tumor microenvironment implicated in tumor growth and dissemination. Herein, we investigated if diabetic concentrations of metformin could impinge upon the previously reported observation that platelet induces an increase in the tube forming capacity of endothelial cells (angiogenesis) and upon ovarian cancer cell aggressiveness. We demonstrate that metformin inhibits the increase in angiogenesis brought about by platelets in a mechanism that did not alter endothelial cell migration. In ovarian cancer cell lines and primary cultured cancer cells isolated from the ascitic fluid of ovarian cancer patients, we assessed the effect of combinations of platelets and metformin upon angiogenesis, migration, invasion and cancer sphere formation. The enhancement of each of these parameters by platelets was abrogated by the present of metformin in the vast majority of cancer cell cultures tested. Neither metformin nor platelets altered proliferation; however, metformin inhibited the increase in phosphorylation of focal adhesion kinase induced by platelets. We present the first evidence suggesting that concentrations of metformin present in diabetic patients may reduce the actions of platelets upon both endothelial cells and cancer cell survival and dissemination.

Inhibition of glioblastoma tumorspheres by combined treatment with 2-deoxyglucose and metformin

Background

Deprivation of tumor bioenergetics by inhibition of multiple energy pathways has been suggested as an effective therapeutic approach for various human tumors. However, this idea has not been evaluated in glioblastoma (GBM). We hypothesized that dual inhibition of glycolysis and oxidative phosphorylation could effectively suppress GBM tumorspheres (TS).

Methods

Effects of 2-deoxyglucose (2DG) and metformin, alone and in combination, on GBM-TS were evaluated. Viability, cellular energy metabolism status, stemness, invasive properties, and GBM-TS transcriptomes were examined. In vivo efficacy was tested in a mouse orthotopic xenograft model.

Results

GBM-TS viability was decreased by the combination of 2DG and metformin. ATP assay and PET showed that cellular energy metabolism was also decreased by this combination. Sphere formation, expression of stemness-related proteins, and invasive capacity of GBM-TS were also significantly suppressed by combined treatment with 2DG and metformin. A transcriptome analysis showed that the expression levels of stemness- and epithelial mesenchymal transition-related genes were also significantly downregulated by combination of 2DG and metformin. Combination treatment also prolonged survival of tumor-bearing mice and decreased invasiveness of GBM-TS.

Conclusion

The combination of 2DG and metformin effectively decreased the stemness and invasive properties of GBM-TS and showed a potential survival benefit in a mouse orthotopic xenograft model. Our findings suggest that targeting TS-forming cells by this dual inhibition of cellular bioenergetics warrants expedited clinical evaluation for the treatment of GBM.

Repurposing metformin for the prevention of cancer and cancer recurrence

Multiple epidemiological studies have documented an association between metformin, used for treatment of type 2 diabetes, and reduced cancer incidence and mortality. Cell line models may not accurately reflect the effects of metformin in the clinical setting. Moreover, findings from animal model studies have been inconsistent, whilst those from more recent epidemiological studies have tempered the overall effect size. The purpose of this review is to examine metformin's chemopreventive potential by outlining relevant mechanisms of action, the most recent epidemiologic evidence, and recently completed and ongoing clinical trials. Although repurposing drugs with excellent safety profiles is an appealing strategy for cancer prevention and treatment in the adjuvant setting, there is no substitute for well-executed, large randomised clinical trials to define efficacy and determine the populations that are most likely to benefit from an intervention. Thus, enthusiasm remains for understanding the role of metformin in cancer through ongoing clinical research.

Metformin ameliorates skeletal muscle insulin resistance by inhibiting miR-21 expression in a high-fat dietary rat model

Insulin resistance (IR) plays a major role in the pathogenesis of abdominal obesity, hypertension, coronary heart disease, atherosclerosis and diabetes. miR-21 and TGF-β/smads is closely related to IR. However, it remained elusive whether metformin improved skeletal muscle insulin resistance (IRSM) by regulating miR-21 and its target signal TGF-β1/smads expression. In this study, high-fat diet rats with IR model and IR-skeletal muscle L6 cells (L6-SMCs) model were established, insulin sensitive index (ISI) and Homeostasis model assessment of IR (HOMA-IR) were applied, miR-21 and TGF-β1/smads mRNA expression were examined by RT-PCR, smad3 and smad7 protein were detected by western-blotting and laser scanning confocal microscopy (LSCM), the valid target of miR-21 was detected by luciferase reporter gene assay. Here, we found that metformin dose-dependently decreased miR-21 expression, accompanied by the decrease of HOMA-IR and the increase of HOMA-ISI. Luciferase report gene assay showed that smad7 was an effective target of miR-21. miR-21 overexpression directly downregulated smad7 and indirectly upregulated smad3 expression. Interestingly, miR-21 expression positively correlated with HOMA-IR and negatively correlated with HOMA-ISI. In conclusion, our results demonstrated that metformin improved IRSM by inhibiting miR-21 expression, and that miR-21 may be one of the therapeutic targets for IR.

Morphoproteomics, E6/E7 in-situ hybridization, and biomedical analytics define the etiopathogenesis of HPV-associated oropharyngeal carcinoma and provide targeted therapeutic options

BACKGROUND

Human papillomavirus (HPV) has been identified as an etiopathogenetic factor in oropharyngeal squamous cell carcinoma. The HPV E6 and E7 oncogenes are instrumental in promoting proliferation and blocking differentiation leading to tumorigenesis. Although surgical intervention can remove such tumors, the potential for an etiologic field effect with recurrent disease is real. A downstream effector of E7 oncoprotein, enhancer of zeste homolog 2 (EZH2), is known to promote proliferation and to pose a block in differentiation and in turn, could lead to HPV-induced malignant transformation. However, the EZH2 pathway is amenable to low toxicity therapies designed to promote differentiation to a more benign state and prevent recurrent disease by inhibiting the incorporation of HPV into the genome. This is the first study using clinical specimens to demonstrate EZH2 protein expression in oropharyngeal carcinoma (OPC).

METHODS

The study included eight patients with oropharyngeal carcinoma, confirmed p16INK4a- positive by immunohistochemistry (IHC). The tissue expression of E6/E7 messenger RNA (mRNA) was measured by RNAscope® in-situ hybridization technology. Expression of EZH2, Ki-67, and mitotic indices were assessed by morphoproteomic analysis. Biomedical analytics expanded the results with data from Ingenuity Pathway Analysis (IPA) and KEGG databases to construct a molecular network pathway for further insights.

RESULTS

Expression of E6 and E7 oncogenes in p16INK4a- positive oropharyngeal carcinoma was confirmed. EZH2 and its correlates, including elevated proliferation index (Ki-67) and mitotic progression were also present. Biomedical analytics validated the relationship between HPV- E6 and E7 and the expression of the EZH2 pathway.

CONCLUSION

There is morphoproteomic and mRNA evidence of the association of p16INK4a-HPV infection with the E6 and E7 oncogenes and the expression of EZH2, Ki-67 and mitotic progression in oropharyngeal carcinoma. The molecular network biology was confirmed by biomedical analytics as consistent with published literature. This is significant because the biology lends itself to targeted therapeutic options using metformin, curcumin, celecoxib and sulforaphane as therapeutic strategies to prevent progression or recurrence of disease.

Cytotoxic effect of a family of peroxisome proliferator-activated receptor antagonists in colorectal and pancreatic cancer cell lines

Recent studies report an interesting role of peroxisome proliferator-activated receptor (PPAR) antagonists in different tumor models, being these compounds able to perturb metabolism and viability in cancer cells. In this work, the identification of a novel PPAR antagonist, showing inhibitory activity on PPARα and a weaker antagonism on PPARγ, is described. The activity of this compound and of a series of chemical analogues was investigated in selected tumor cell lines, expressing both PPARα and PPARγ. Data obtained show a dose-dependent cytotoxic effect of the novel PPAR antagonist in colorectal and pancreatic cancer models.

MicroRNA-26a inhibits the growth and invasiveness of malignant melanoma and directly targets on MITF gene

Metastatic melanoma is the most aggressive form of skin cancer and is refractory to therapy. MicroRNAs have been recently discovered as novel molecules that provide therapeutic benefits against melanoma. This work aims to examine the effects of miR-26a and let-7a on the growth and invasiveness of malignant melanoma in vitro and in vivo. In addition, we elucidate the mechanism of action by identifying the target gene of miR-26a. Both miR-26a and let-7a inhibited proliferation and invasiveness and halted the cell cycle at the G₁/G₀ phase in SKMEL-28 and WM1552C malignant melanoma cell lines. Moreover, miR-26a potently induced apoptosis and downregulated the expressions of microphthalmia-associated transcription factor (MITF) and MAP4K3 in both cell lines. The luciferase reporter assay demonstrated that miR-26a suppresses MITF expression by binding the 3′-UTR, suggesting that MITF is a bona fide target of miR-26a. SiRNA knockdown of the MITF gene confirmed that miR-26a reduced cell viability and induced apoptosis by regulating MITF. Using a murine model, we also found miR-26a significantly retarded the growth of melanoma tumors in vivo. In conclusion, miR-26a and let-7a suppressed the growth and invasiveness of melanoma cells, suggesting that miR-26a and let-7a may represent novel therapies for malignant melanoma.

Metformin Inhibits Tumorigenesis and Tumor Growth of Breast Cancer Cells by Upregulating miR-200c but Downregulating AKT2 Expression

Background: Metformin has been reported to inhibit the growth of various types of cancers, including breast cancer. Yet the mechanisms underlying the anticancer effects of metformin are not fully understood. Growing evidence suggests that metformin's anticancer effects are mediated at least in part by modulating microRNAs, including miR-200c, which has a tumor suppressive role in breast cancer. We hypothesized that miR-200c has a role in the antitumorigenic effects of metformin on breast cancer cells.

Methods: To delineate the role of miR-200c in the effects of metformin on breast cancer, plasmids containing pre-miR-200c or miR-200c inhibitor were transfected into breast cancer cell lines. The MDA-MB-231, BT549, MCF-7, and T-47-D cells' proliferation, apoptosis, migration, and invasion were assessed. The antitumor role of metformin in vivo was investigated in a MDA-MB-231 xenograft tumor model in SCID mice.

Results: Metformin significantly inhibited the growth, migration, and invasion of breast cancer cells, and induced their apoptosis; these effects were dependent on both dose and time. Metformin also suppressed MDA-MB-231 tumor growth in SCID mice in vivo. Metformin treatment was associated with increased miR-200c expression and decreased c-Myc and AKT2 protein expression in both breast cancer cells and tumor tissues. Overexpression of miR-200c exhibited effects on breast cancer cells similar to those of metformin treatment. In contrast, inhibiting the expression of miR-200c increased the growth, migration, and invasion of MCF-7 and MDA-MB-231 cells.

Conclusion: Metformin inhibits the growth and invasiveness of breast cancer cells by upregulation of miR-200c expression by targeting AKT2. These findings provide novel insight into the molecular functions of metformin that suggest its potential as an anticancer agent.

MicroRNAs in HPV associated cancers: small players with big consequences

INTRODUCTION

MicroRNAs (miRs) are short (~20 nucleotides) non-coding ribonuecleic acids (ncRNAs) known to be involved in cellular processes such as proliferation, differentiation, immune response, pathogenicity and tumourigenesis, among many others. The regulatory mechanisms exerted by miRs have been implicated in many cancers, including Human Papillomavirus (HPV)-associated cancers. Areas covered: In this review, the authors discuss the involvement of miRs (-143, -375, -21, -200, -296 etc.) that have been shown to be dysregulated in HPV-associated cancers. This review also encompasses both intracellular and exosomal miRs, and their potential as diagnostic biomarkers in saliva and blood. The authors have also attempted to dissect the functional impact of miRs on cellular processes such as changes in cellular polarity, loss of apoptosis and tumour suppression, and unchecked and uncontrolled cell cycle regulation, all of which ultimately lead to aberrant cellular proliferation. Expert commentary: Identification of dysregulated miRs in HPV-associated cancers opens up new opportunities to develop diagnostic, therapeutic and prognostic biomarkers. Studies on global expression patterns of miRs dysregulated in HPV-associated cancers can be instrumental in developing broader therapeutic strategies. Therapies like anti-miR, miR-replacement and those based on alternative natural products targeting miRs, need to be improved and better synchronized to be cost-effective and have better treatment outcomes.

Elimination of cancer stem cells and reactivation of latent HIV-1 via AMPK activation: Common mechanism of action linking inhibition of tumorigenesis and the potential eradication of HIV-1

Although promising treatments are currently in development to slow disease progression and increase patient survival, cancer remains the second leading cause of death in the United States. Cancer treatment modalities commonly include chemoradiation and therapies that target components of aberrantly activated signaling pathways. However, treatment resistance is a common occurrence and recent evidence indicates that the existence of cancer stem cells (CSCs) may underlie the limited efficacy and inability of current treatments to effectuate a cure. CSCs, which are largely resistant to chemoradiation therapy, are a subpopulation of cancer cells that exhibit characteristics similar to embryonic stem cells (ESCs), including self-renewal, multi-lineage differentiation, and the ability to initiate tumorigenesis. Interestingly, intracellular mechanisms that sustain quiescence and promote self-renewal in adult stem cells (ASCs) and CSCs likely also function to maintain latency of HIV-1 in CD4⁺ memory T cells. Although antiretroviral therapy is highly effective in controlling HIV-1 replication, the persistence of latent but replication-competent proviruses necessitates the development of compounds that are capable of selectively reactivating the latent virus, a method known as the "shock and kill" approach. Homeostatic proliferation in central CD4⁺ memory T (T_CM) cells, a memory T cell subset that exhibits limited self-renewal and differentiation and is a primary reservoir for latent HIV-1, has been shown to reinforce and stabilize the latent reservoir in the absence of T cell activation and differentiation. HIV-1 has also been found to establish durable and long-lasting latency in a recently discovered subset of CD4⁺ T cells known as T memory stem (T_SCM) cells. T_SCM cells, compared to T_CM cells, exhibit stem cell properties that more closely match those of ESCs and ASCs, including self-renewal and differentiation into all memory T cell subsets. It is our hypothesis that activation of AMPK, a master regulator of cellular metabolism that plays a critical role in T cell activation and differentiation of ESCs and ASCs, will lead to both T cell activation-induced latent HIV-1 reactivation, facilitating virus destruction, as well as "activation", differentiation, and/or apoptosis of CSCs, thus inhibiting tumorigenesis. We also propose the novel observation that compounds that have been shown to both facilitate latent HIV-1 reactivation and promote CSC differentiation/apoptosis (e.g. bryostatin-1, JQ1, metformin, butyrate, etc.) likely do so through a common mechanism of AMPK activation.

Metformin increases chemo-sensitivity via gene downregulation encoding DNA replication proteins in 5-Fu resistant colorectal cancer cells

Metformin is most widely prescribed for type 2 diabetes. Recently, evidences have shown that metformin has anticancer effects on pancreatic-, colorectal-, ovarian-, and other cancers. Because metformin has less adverse effects and is inexpensive, it could be a useful chemo-therapeutic agent with anticancer effects. In this study, we demonstrated metformin inhibited by cell proliferation, cell migration ability, clonogenic ability, and cancer stem cell population. Metformin also induced cell cycle arrest in parental-(SNU-C5), and 5-Fu resistant-colorectal cancer cell line (SNU-C5_5FuR). Moreover, a treatment that combines 5-Fu and metformin was found to have a synergistic effect on the cell proliferation rate, especially in SNU-C5_5FuR, which was mediated by the activation of AMPK pathway and NF-ƙB pathway, well-known metformin mechanisms. In this study, we suggested novel anticancer mechanism of metformin that inhibited DNA replication machinery, such as the MCM family in SNU-C5_5FuR. In conclusion, we provided that how metformin acts as not only a chemo-sensitizer, but also as a synergistic effector of 5-Fu in the 5-Fu resistant-cell line. We speculate that metformin used for adjuvant therapy is effective on 5-Fu resistant cancer cells.

Prognostic role of metformin intake in diabetic patients with colorectal cancer: An updated qualitative evidence of cohort studies

Several observational studies have shown that metformin can modify the risk and survival of colorectal cancer (CRC) in patients with diabetes mellitus, although the magnitude of this relationship has not been determined. We conducted an updated systematic review and meta-analysis to analyze the association between metformin and CRC mortality and searched relevant databases up to July 2016. The primary outcome was overall survival (OS). Secondary outcomes were cancer-specific survival (CS) and disease-free survival (DFS). Summary hazard ratios (HRs) were calculated using a random-effects model. Seventeen studies enrolling 269,417 participants were eligible for inclusion. Comparing with non-metformin users in diabetic CRC patients, the summary HRs for OS in metformin users were 0.69 (95% CI, 0.61-0.77). Subgroup analyses stratified by the study characteristics and sensitivity analysis by the trim-and-fill method (adjusted HR 0.77, 95% CI, 0.67-0.87) confirmed the robustness of the results. However, significant OS benefit was noted in patients with stage II and III disease. Five studies reported the CRC prognosis for CS and three for DFS; metformin intake was significantly associated with patient CS (HR 0.75, 95% CI, 0.59-0.94), but not DFS (HR 0.38, 95% CI, 0.13-1.17). Our findings suggest that metformin intake is associated with improved survival outcomes in terms of OS and CS in CRC patients with diabetes, particular for OS in stage II and stage III patients. Further studies should be conducted to determine CRC survival between metformin use and patient specific clinical and molecular profiles.

Model-based unsupervised learning informs metformin-induced cell-migration inhibition through an AMPK-independent mechanism in breast cancer

We demonstrate that model-based unsupervised learning can uniquely discriminate single-cell subpopulations by their gene expression distributions, which in turn allow us to identify specific genes for focused functional studies. This method was applied to MDA-MB-231 breast cancer cells treated with the antidiabetic drug metformin, which is being repurposed for treatment of triple-negative breast cancer. Unsupervised learning identified a cluster of metformin-treated cells characterized by a significant suppression of 230 genes (p-value < 2E-16). This analysis corroborates known studies of metformin action: a) pathway analysis indicated known mechanisms related to metformin action, including the citric acid (TCA) cycle, oxidative phosphorylation, and mitochondrial dysfunction (p-value < 1E-9); b) 70% of these 230 genes were functionally implicated in metformin response; c) among remaining lesser functionally-studied genes for metformin-response was CDC42, down-regulated in breast cancer treated with metformin. However, CDC42's mechanisms in metformin response remained unclear. Our functional studies showed that CDC42 was involved in metformin-induced inhibition of cell proliferation and cell migration mediated through an AMPK-independent mechanism. Our results points to 230 genes that might serve as metformin response signatures, which needs to be tested in patients treated with metformin and, further investigation of CDC42 and AMPK-independence's role in metformin's anticancer mechanisms.

Dual inhibiting OCT4 and AKT potently suppresses the propagation of human cancer cells

AKT serves as an epigenetic modulator that links epigenetic regulation to cell survival and proliferation while the epigenetic mediator OCT4 critically controls stem cell pluripotency and self-renewal. Emerging evidence indicated their complicated interplays in cancer cells and cancer stem cells (CSCs), and inhibiting either one may activate the other. Thus, in this study, we propose a strategy to targeting both factors simultaneously. Firstly, a combination of an OCT4-specific shRNA and the specific AKT inhibitor Akti-1/2 potently suppressed the propagation of human embryonal carcinoma cells, adherent cancer cells and stem-like cancer cells, establishing the proof-of-concept that dual inhibiting OCT4 and AKT can effectively target various cancer cells. Next, we combined Akti-1/2 with metformin, a widely-prescribed drug for treating type 2 diabetes, which was reported to down-regulate OCT4 expression. The metformin + Akti-1/2 combo significantly altered multiple signaling and epigenetic pathways, induced growth arrest and cell death of adherent and stem-like glioblastoma U87 cells, and attenuated their tumorigenicity in vivo. Taken together, we demonstrate here that simultaneously targeting an epigenetic mediator and an epigenetic modulator, by dual inhibiting OCT4 and AKT, can have significantly improved efficacies over single treatment in suppressing the propagation of CSCs as well as the entire bulk of differentiated cancer cells.

miRNA-320a inhibits tumor proliferation and invasion by targeting c-Myc in human hepatocellular carcinoma

BACKGROUND

Downregulated expression levels of microRNA-320a (miR-320a) were found in primary breast cancers and colorectal cancer. Previous findings indicated that miRNA-320a may involve in the cancer development. In this study, we explored the roles of miR-320a by targeting c-Myc in the tumor growth of hepatocellular carcinoma (HCC).

METHODS

Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was performed to detect the expression of miR-320a in 50 HCC tissues and four HCC cells. Luciferase reporter assay was conducted to confirm the direct downstream target of miR-320a in HEK-293 cells. The effect of miR-320a on endogenous c-Myc expression was investigated by transfecting miR-320a mimics into HepG2 and QGY-7703 cell lines. The c-Myc and miR-320a expressions were analyzed by immunohistochemistry (IHC) and qRT-PCR in the same HCC tissues. Furthermore, the biological functional correlation of miR-320a with c-Myc was determined by studying the effect of miR-320a mimics or c-Myc small interfering RNA (siRNA) on HCC cell proliferation and invasion.

RESULTS

The expression of miR-320a was downregulated in 50 HCC tissues and 4 HCC cells. Luciferase assay revealed that c-Myc is a direct target of miR-320a. IHC and Western blot analysis showed that the c-Myc expression was inhibited by miR-320a in HCC tissues and cell lines. Upregulation of miR-320a suppressed the HCC cell proliferation and invasion capacity induced by inhibiting c-Myc, and the results were consistent with the effects of c-Myc siRNA on tumor suppression. These results revealed that miRNA-320a inhibits tumor proliferation and invasion by targeting c-Myc in HCC cells.

CONCLUSION

Our results showed that miR-320a functions as a tumor suppressor in HCC. By targeting c-Myc directly, miR-320a inhibits the HCC cell growth. Our studies provide evidence of miR-320a as a potentially target for HCC treatment.

Expression of metastasis related genes S100A4 and MMP-9 in pancreatic cancer cells treated with metformin

AIM

To investigate the expression of metastasis related genes S100A4 and matrix metalloproteinase (MMP)-9 in pancreatic cancer cell lines BxPC-3 and AsPC-1 treated with metformin.

METHODS

Cells were incubated with metformin at different concentrations for 24, 48, or 72 h. Then, cell viability was measured by MTT assay, and IC₅₀ values were calculated. The two cell lines were then treated with metformin at IC₅₀ concentrations for 48 h, and RT-PCR was used to detect the expression of S100A4 and MMP-9 mRNAs.

RESULTS

Cell viability was apparently inhibited by metformin in both cell lines, and the inhibitory effect showed a time- and dose-dependent manner. The IC₅₀ values for BxPC-3 cells at 24, 48, and 72 h were 12.13 mmol/L, 10.43 mmol/L, and 9.55 mmol/L, respectively, and the corresponding values for AsPC-1 cells were 23.45 mmol/L, 15.44 mmol/L, and 11.30 mmol/L. After treatment with metformin for 48 h, the expression of S100A4 and MMP-9 mRNAs in the two cell lines was significantly decreased compared with control cells (P < 0.01).

CONCLUSION

Metformin inhibits pancreatic cancer cell growth in a time- and dose-dependent manner. Metformin may exert anti-metastasis effects by decreasing the expression of S100A4 and MMP-9 in pancreatic cancer cell lines.

Metformin targets multiple signaling pathways in cancer

Metformin, an inexpensive and well-tolerated oral agent commonly used in the first-line treatment of type 2 diabetes, has become the focus of intense research as a candidate anticancer agent. Here, we discuss the potential of metformin in cancer therapeutics, particularly its functions in multiple signaling pathways, including AMP-activated protein kinase, mammalian target of rapamycin, insulin-like growth factor, c-Jun N-terminal kinase/mitogen-activated protein kinase (p38 MAPK), human epidermal growth factor receptor-2, and nuclear factor kappaB pathways. In addition, cutting-edge targeting of cancer stem cells by metformin is summarized.

microRNA regulation of human pancreatic cancer stem cells

microRNAs (miRNAs) are a group of small non-coding RNAs that function primarily in the post transcriptional regulation of gene expression in plants and animals. Deregulation of miRNA expression in cancer cells, including pancreatic cancer cells, is well documented, and the involvement of miRNAs in orchestrating tumor genesis and cancer progression has been recognized. This review focuses on recent reports demonstrating that miRNAs are involved in regulation of pancreatic cancer stem cells (CSCs). A number of miRNA species have been identified to be involved in regulating pancreatic CSCs, including miR-21, miR-34, miR-1246, miR-221, the miR-17-92 cluster, the miR-200 and let-7 families. Furthermore, the Notch-signaling pathway and epithelial-mesenchymal transition (EMT) process are associated with miRNA regulation of pancreatic CSCs. Given the significant contribution of CSCs to chemo-resistance and tumor progression, a better understanding of how miRNAs function in pancreatic CSCs could provide novel strategies for the development of therapeutics and diagnostics for this devastating disease.

Metformin Prevents the Progression of Dysplastic Mucosa of the Head and Neck to Carcinoma in Nondiabetic Patients

OBJECTIVE

Metformin is an oral anti-hyperglycemic agent used to treat type 2 diabetes mellitus (DM). In vitro and animal models have shown that metformin can prevent the progression of oral lesions to carcinoma; however, there is conflicting data in the clinical literature regarding risk reduction for malignancy in head and neck cancer (HNC).

STUDY DESIGN

Case series.

METHODS

We present 3 cases in which adjuvant metformin therapy was used to treat recurrent and multifocal dysplastic lesions in previously treated nondiabetic HNC patients.

RESULTS

Patients included 1 with a history of oral cavity squamous cell carcinoma (SCC) and 2 with a history of laryngeal SCC. Follow-up time ranged between 3 and 33 months. All 3 patients showed complete or partial regression of the remaining mucosal lesions and did not require any additional surgeries.

CONCLUSION

We present 3 cases of nondiabetic HNC patients with field cancerization who showed a good response to adjuvant therapy with metformin. The nondiabetic population is not affected by confounding factors such as increased risk of malignancy and decreased overall survival that is itself associated with abnormal glucose metabolism and is therefore an excellent cohort in which to study the use of adjuvant metformin therapy in HNC patients.

Galeterone and its analogs inhibit Mnk-eIF4E axis, synergize with gemcitabine, impede pancreatic cancer cell migration, invasion and proliferation and inhibit tumor growth in mice

Survival rate for pancreatic cancer (pancreatic ductal adenocarcinoma, PDAC) is poor, with about 80% of patients presenting with the metastatic disease. Gemcitabine, the standard chemotherapeutic agent for locally advanced and metastatic PDAC has limited efficacy, attributed to innate/acquired resistance and activation of pro-survival pathways. The Mnk1/2-eIF4E and NF-κB signaling pathways are implicated in PDAC disease progression/metastasis and also associated with gemcitabine-induced resistance in PDAC. Galeterone (gal), a multi-target, agent in phase III clinical development for prostate cancer has also shown effects on the aforementioned pathways. We show for the first time, that gal/analogs (VNPT55, VNPP414 and VNPP433-3β) profoundly inhibited cell viability of gemcitabine-naive/resistance PDAC cell lines and strongly synergized with gemcitabine in gemcitabine-resistant PDAC cells. In addition, to inducing G1 cell cycle arrest, gal/analogs induced caspase 3-mediated cell-death of PDAC cells. Gal/analogs caused profound downregulation of Mnk1/2, peIF4E and NF-κB (p-p65), metastatic inducing factors (N-cadherin, MMP-1/-2/-9, Slug, Snail and CXCR4) and putative stem cell factors, (β-Catenin, Nanog, BMI-1 and Oct-4). Gal/analog also depleted EZH2 and upregulated E-Cadherin. These effects resulted in significant inhibition of PDAC cell migration, invasion and proliferation. Importantly, we also observed strong MiaPaca-2 tumor xenograft growth inhibition (61% to 92%). Collectively, these promising findings strongly support further development of gal/analogs as novel therapeutics for PDAC.