SGLT gene expression in primary lung cancers and their metastatic lesions

Atrial fibrillation in cancer, anticancer therapies, and underlying mechanisms

Atrial fibrillation (AF) is a common arrhythmic complication in cancer patients and can be exacerbated by traditional cytotoxic and targeted anticancer therapies. Increased incidence of AF in cancer patients is independent of confounding factors, including preexisting myocardial arrhythmogenic substrates, type of cancer, or cancer stage. Mechanistically, AF is characterized by fast unsynchronized atrial contractions with rapid ventricular response, which impairs ventricular filling and results in various symptoms such as fatigue, chest pain, and shortness of breath. Due to increased blood stasis, a consequence of both cancer and AF, concern for stroke increases in this patient population. To compound matters, cardiotoxic anticancer therapies themselves promote AF; thereby exacerbating AF morbidity and mortality in cancer patients. In this review, we examine the relationship between AF, cancer, and cardiotoxic anticancer therapies with a focus on the shared molecular and electrophysiological mechanisms linking these disease processes. We also explore the potential role of sodium-glucose co-transporter 2 inhibitors (SGLT2i) in the management of anticancer-therapy-induced AF.

Empagliflozin demonstrates cytotoxicity and synergy with tamoxifen in ER-positive breast cancer cells: anti-proliferative and anti-survival effects

Accumulating evidence suggests that sodium-glucose cotransporter 2 (SGLT2) inhibitors may be effective at eliminating tumor cells. While empagliflozin exhibits nearly the highest selectivity for SGLT2 over SGLT1, its specific impact alone and in combination with tamoxifen remains largely unexplored in estrogen receptor α-positive (ERα +) breast cancer. This study investigated the anticancer effects of empagliflozin and its potential synergy with tamoxifen in MCF-7 breast cancer cells. The individual and combined cytotoxic effects of empagliflozin and tamoxifen were assessed using the xCELLigence system. The activities of AMP-activated protein kinase α (AMPKα), p38 mitogen-activated protein kinase (p38 MAPKα), p70-S6 kinase 1 (p70S6K1), and protein kinase B (Akt) were assessed using Western blotting. The gene expression levels of peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) and Forkhead box O3a (FOXO3a) were assessed via qPCR. Our results revealed time- and concentration-dependent cytotoxic effects of empagliflozin and tamoxifen whether administered separately or in combination. While tamoxifen exhibits potency with an IC50 value of 17 μM, approximately ten times greater than that of empagliflozin (IC50 = 177 μM), synergistic effects are observed when the concentrations of the two agents approach their respective IC50 values. Additionally, empagliflozin significantly increases AMPKα activity while concurrently inhibiting Akt, p70S6K1, and p38 MAPKα, and these effects are significantly enhanced when empagliflozin is combined with tamoxifen. Moreover, empagliflozin modulates the gene expression, downregulating PGC-1α while upregulating FOXO3a. Empagliflozin exerts anti-proliferative and anti-survival effects by inhibiting mTOR, Akt, and PGC-1α, and it exhibits synergy with tamoxifen in MCF-7 breast cancer cells.

SGLT2 inhibitor promotes mitochondrial dysfunction and ER-phagy in colorectal cancer cells

BACKGROUND

Sodium-glucose transporter 2 (SGLT2) inhibitors (iSGLT2) are approved medications for type 2 diabetes. Recent studies indicate that iSGLT2 inhibit the growth of some cancer cells. However, the mechanism(s) remains to be fully elucidated.

METHODS

The SGLT2 levels were determined in normal colon CCD 841 CoN and, HCT 116, HT-29, SW480 and LoVo colorectal cancer (CRC) cell lines by quantitative real-time PCR and western blot. The effect of iSGLT2 canagliflozin on cell proliferation was examined using CCK-8, as its role on CRC cells metabolism and tumorigenesis has been evaluated by XF HS Seahorse Bioanalyzer and flow cytometric analyses. Transient gene silencing experiments and analysis of protein-protein interaction network were conducted to evaluate the SGLT2 molecular targets in CRC cells.

RESULTS

Data showed that the treatment with iSGLT2 (50 µM) for 72 h induced cell cycle arrest (p < 0.001), impaired glucose and energetic metabolism (p < 0.001), promoted apoptotic cell death and ER stress flowing into autophagy (p < 0.001) in HCT 116 and HT-29 cells. These cellular events were accompanied by sirtuin 3 (SIRT3) upregulation (p < 0.01), as also supported by SIRT3 transient silencing experiments resulting in the attenuation of the effects of iSGLT2 on the cellular metabolic/energetic alterations and the induction of programmed cell death. The identification and validation of dipeptidyl peptidase 4 (DPP4) as potential common target of SGLT2 and SIRT3 were also assessed.

CONCLUSIONS

These results deepened knowledge on the iSGLT2 contribution in limiting CRC tumorigenesis unveiling the SGLT2/SIRT3 axis in the cytotoxic mechanisms.

The Clinical Relevance of the Expression of SGLT2 in Lung Adenocarcinoma

PURPOSE

We aimed to elucidate the functions and clinical relevance of sodium-glucose cotransporter 2 (SGLT2) in resected lung adenocarcinoma.

METHODS

The protein expression of SGLT2 in tumor samples from 199 patients with lung adenocarcinoma was analyzed by immunohistochemistry, and the protein expression, clinical variables, and survival outcomes were compared.

RESULTS

The median SGLT2 expression was significantly higher in advanced-stage and more aggressive adenocarcinomas. Age ≥70 (p < 0.01), BI ≥600 (p < 0.01), PRDX4 <25 (p < 0.01), and SGLT2 ≥12% (p = 0.03) were significant factors for RFS in multivariate analysis. Significant differences were observed in the RFS rates of the groups divided using the cutoff value of SGLT2 ≥12% (5-year RFS: 72.6% vs. 90%) (p < 0.01).

CONCLUSION

The expression of SGLT2 was more frequently detected in advanced-stage and more aggressive adenocarcinomas with aggressive biological behavior than in their counterparts. The survival analysis revealed that the strong expression of SGLT2 was associated with poorer RFS. The SGLT2 expression predicts postoperative recurrence in lung adenocarcinoma patients.

Role of SLC5A2 polymorphisms and effects of genetic polymorphism on sodium glucose cotransporter 2 inhibitorsinhibitor response

Type 2 diabetes mellitus (T2DM) is a complex metabolic disease characterized by hyperglycaemia. T2DM is a highly heterogeneous polygenic disease. Due to genetic variation, variations in lifestyle and other environmental exposures, there are certain variations in the phenotype of T2DM patients. Sodium glucose cotransporter 2 (SGLT2) inhibitors are novel hypoglycaemic agents that increase urinary glucose excretion by inhibiting glucose reabsorption in the proximal tubules of the kidney. For glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, studies have confirmed a variety of gene variants that may modify their effects. For SGLT2 inhibitors, research has focused on the SLC5A2 gene encoding SGLT2 and UGT1A9 gene polymorphisms affecting SGLT2 inhibitor metabolism. The SLC5A2 polymorphism rs9934336 have been associated with decreased HbA1c during the oral glucose tolerance test. Common variants of the SLC5A2 gene are related to blood glucose and insulin concentrations, but not glucagon concentrations. SLC5A2 rs9934336 and rs3116150 are related to a lower risk of heart failure. SGLT2 inhibitor exposure of UGT1A9*3 carriers is commonly higher than that of noncarriers, while these effects commonly have no obvious clinical significance on SGLT2 inhibitor pharmacokinetics. In terms of efficacy, general SLC5A2 variants show no significant effect on the response to the SGLT2 inhibitor empagliflozin. At present, research on the relationship between genetic polymorphisms and the efficacy of SGLT2 inhibitors is limited. The main purpose of this review is to elucidate the general effects of SGLT2 polymorphisms and the association between polymorphisms and the treatment response to SGLT2 inhibitors.

SGLT1 as an adverse prognostic factor in invasive ductal carcinoma of the breast

PURPOSE

Sodium/glucose cotransporter (SGLT) 1 and 2 expression in carcinoma cells was recently examined, but their association with the clinicopathological factors of the patients and their biological effects on breast carcinoma cells have remained remain virtually unknown. Therefore, in this study, we explored the expression status of SGLT1 and SGLT2 in breast cancer patients and examined the effects of SGLT1 inhibitors on breast carcinoma cells in vitro.

METHODS

SGLT1 and SGLT2 were immunolocalized and we first correlated the findings with clinicopathological factors of the patients. We then administered mizagliflozin and KGA-2727, SGLT1 specific inhibitors to MCF-7 and MDA-MB-468 breast carcinoma cell lines, and their growth-inhibitory effects were examined. Protein arrays were then used to further explore their effects on the growth factors.

RESULTS

The SGLT1 high group had significantly worse clinical outcome including both overall survival and disease-free survival than low group. SGLT2 status was not significantly correlated with clinical outcome of the patients. Both mizagliflozin and KGA-2727 inhibited the growth of breast cancer cell lines. Of particular interest, mizagliflozin inhibited the proliferation of MCF-7 cells, even under very low glucose conditions. Mizagliflozin downregulated vascular endothelial growth factor receptor 2 phosphorylation.

CONCLUSION

High SGLT1 expression turned out as an adverse clinical prognostic factor in breast cancer patient. This is the first study demonstrating that SGLT1 inhibitors suppressed breast carcinoma cell proliferation. These results indicated that SGLT1 inhibitors could be used as therapeutic agents for breast cancer patients with aggressive biological behaviors.

Correlations between class I glucose transporter expression patterns and clinical outcomes in non-small cell lung cancer

BACKGROUND

Glucose transporters (GLUTs) are highly expressed in various cancers. However, the implications of these variable expression patterns are unclear. This study aimed to clarify the correlation between class I GLUT expression patterns and clinical outcomes in non-small cell lung cancer (NSCLC), including their potential role in inflammatory signaling.

METHODS

Biopsy tissues from 132 patients with NSCLC (92 adenocarcinomas [ADC] and 40 squamous cell carcinomas [SQCC]) were analyzed. mRNA expression levels of class I GLUTs (solute carrier 2A [SLC2A]1, SLC2A2, SLC2A3, and SLC2A4) and inflammation-related molecules (toll-like receptors TLR4, RelA/p65, and interleukins IL8 and IL6) were measured. Cellular localization of GLUT3 and GLUT4 was investigated using immunofluorescence.

RESULTS

Single, combined, and negative GLUT (SLC2A) expression were observed in 27/92 (29.3%), 27/92 (29.3%), and 38/92 (41.3%, p < 0.001) of ADC and 8/40 (20.0%), 29/40 (72.5%, p < 0.001), and 3/40 (7.5%) of SQCC, respectively. In ADC, the single SLC2A3-expressed group had a significantly poorer prognosis, whereas the single SLC2A4-expressed group had a significantly better prognosis. The combined expression groups showed no significant difference. SLC2A expression was not correlated with SQCC prognosis. SLC2A4 expression correlated with lower IL8 expression. GLUT3 and GLUT4 expressions were localized in the tumor cytoplasm.

CONCLUSIONS

In lung ADC, single SLC2A3 expression correlated with poor prognosis, whereas single SLC2A4 expression correlated with better prognosis and lower IL8 expression. GLUT3 expression, which is increased by IL8 overexpression, may be suppressed by increasing the expression of GLUT4 through decreased IL8 expression.

SGLT2 Inhibitors as Potential Anticancer Agents

Sodium-glucose cotransporter 2 (SGLT2) serves as a critical glucose transporter that has been reported to be overexpressed in cancer models, followed by increased glucose uptake in both mice and humans. Inhibition of its expression can robustly thwart tumor development in vitro and in vivo. SGLT2 inhibitors are a comparatively new class of antidiabetic drugs that have demonstrated anticancer effects in several malignancies, including breast, liver, pancreatic, thyroid, prostate, and lung cancers. This review aims to assess the extent of SGLT involvement in different cancer cell lines and discuss the pharmacology, mechanisms of action, and potential applications of SGLT2 inhibitors to reduce tumorigenesis and its progression. Although these agents display a common mechanism of action, they exhibit distinct affinity towards the SGLT type 2 transporter compared to the SGLT type 1 transporter and varying extents of bioavailability and half-lives. While suppression of glucose uptake has been attributed to their primary mode of antidiabetic action, SGLT2 inhibitors have demonstrated several mechanistic ways to combat cancer, including mitochondrial membrane instability, suppression of β-catenin, and PI3K-Akt pathways, increase in cell cycle arrest and apoptosis, and downregulation of oxidative phosphorylation. Growing evidence and ongoing clinical trials suggest a potential benefit of combination therapy using an SGLT2 inhibitor with the standard chemotherapeutic regimen. Nevertheless, further experimental and clinical evidence is required to characterize the expression and role of SGLTs in different cancer types, the activity of different SGLT subtypes, and their role in tumor development and progression.

Sodium channels and the ionic microenvironment of breast tumours

Cancers of epithelial origin such as breast, prostate, cervical, gastric, colon and lung cancer account for a large proportion of deaths worldwide. Better treatment of metastasis, the main cause of cancer deaths, is therefore urgently required. Several of these tumours have been shown to have an abnormally high concentration of Na+ ([Na+ ]) and emerging evidence points to this accumulation being due to elevated intracellular [Na+ ]. This poses intriguing questions about the cellular mechanisms underlying Na+ dysregulation in cancer, and its pathophysiological significance. Elevated intracellular [Na+ ] may be due to alterations in activity of the Na+ /K+ -ATPase, and/or increased influx via Na+ channels and Na+ -linked transporters. Maintenance of the electrochemical Na+ gradient across the plasma membrane is vital to power many cellular processes that are highly active in cancer cells, including glucose and glutamine import. Na+ channels are also upregulated in cancer cells, which in turn promotes tumour growth and metastasis. For example, ENaC and ASICs are overexpressed in cancers, increasing invasion and proliferation. In addition, voltage-gated Na+ channels are also upregulated in a range of tumour types, where they promote metastatic cell behaviours via various mechanisms, including membrane potential depolarisation and altered pH regulation. Together, recent findings relating to elevated Na+ in the tumour microenvironment and how this may be regulated by several classes of Na+ channels provide a link between altered Na+ handling and poor clinical outcome. There are new opportunities to leverage this altered Na+ microenvironment for therapeutic benefit, as exemplified by several ongoing clinical trials.

Sodium-glucose cotransporter 2 (SGLT2) inhibitors and non-small cell lung cancer survival

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a relatively new class of antidiabetic drugs with demonstrated renal and cardiovascular disease benefit. This study evaluates the role of SGLT2 inhibitors on the survival of non-small cell lung cancer (NSCLC) patients.

METHODS

We used National Surveillance, Epidemiology and End Results (SEER)-Medicare linked data. Twenty four thousand nine hundred fifteen NSCLC patients newly diagnosed between 2014 and 2017 with pre-exiting diabetes and aged 66 years or older were included and followed to the end of 2019. Information on SGLT2 inhibitors use was extracted from the Medicare Part D file.

RESULTS

SGLT2 inhibitor use was associated with significantly reduced mortality risk after adjusting for potential confounders (HR = 0.68, 95% CI = 0.60-0.77) with stronger association for longer duration of use (HR = 0.54, 85% CI = 0.44-0.68). Further, we found that SGLT2 inhibitor use was associated with a significant reduced risk of mortality regardless of patients' demographic, tumour characteristics and cancer treatments.

CONCLUSION

Our large SEER-Medicare linked data study indicates that SGLT2 inhibitors use was associated with improved overall survival of NSCLC patients with pre-existing diabetes. Further studies are needed to confirm our findings and elucidate the possible mechanisms behind the association.

Nutrient transporters: connecting cancer metabolism to therapeutic opportunities

Cancer cells rely on certain extracellular nutrients to sustain their metabolism and growth. Solute carrier (SLC) transporters enable cells to acquire extracellular nutrients or shuttle intracellular nutrients across organelles. However, the function of many SLC transporters in cancer is unknown. Determining the key SLC transporters promoting cancer growth could reveal important therapeutic opportunities. Here we summarize recent findings and knowledge gaps on SLC transporters in cancer. We highlight existing inhibitors for studying these transporters, clinical trials on treating cancer by blocking transporters, and compensatory transporters used by cancer cells to evade treatment. We propose targeting transporters simultaneously or in combination with targeted therapy or immunotherapy as alternative strategies for effective cancer therapy.

Platinum glycoconjugates: "Sweet bullets" for targeted cancer therapy?

Cancer, which is characterized by uncontrolled proliferation of abnormal cells, is a leading cause of morbidity and mortality worldwide. Cytotoxic chemotherapy, especially with platinum drugs, remains the mainstay of cancer treatment in the clinical setting. Despite phenomenal success, small-molecule chemotherapeutic drugs suffer from some serious drawbacks. Lack of cancer selectivity and the ensuing side effects mar the therapeutic potential of these drugs. Glycoconjugation has emerged as an attractive strategy for imparting selectivity and improving pharmacokinetics of cytotoxic agents. In this review, we provide an overview of the glycoconjugation strategy and then illustrate the application of this strategy with the help of some concrete examples of platinum based glycoconjugates. At the end we discuss a few important aspects of these glycoconjugates which merit further investigations.

SGLT-2 Inhibitors in Cancer Treatment-Mechanisms of Action and Emerging New Perspectives

A new group of antidiabetic drugs, sodium-glucose cotransporter 2 inhibitors (SGLT-2 inhibitors), have recently been shown to have anticancer effects and their expression has been confirmed in many cancer cell lines. Given the metabolic reprogramming of these cells in a glucose-based model, the ability of SGLT-2 inhibitors to block the glucose uptake by cancer cells appears to be an attractive therapeutic approach. In addition to tumour cells, SGLT-2s are only found in the proximal tubules in the kidneys. Furthermore, as numerous clinical trials have shown, the use of SGLT-2 inhibitors is well-tolerated and safe in patients with diabetes and/or heart failure. In vitro cell culture studies and preclinical in vivo studies have confirmed that SGLT-2 inhibitors exhibit antiproliferative effects on certain types of cancer. However, the mechanisms of this action remain unclear. Even in those tumour cell types in which SGLT-2 is present, there is sometimes an SGLT-2-independent mechanism of anticancer action of this group of drugs. This article presents the current state of knowledge of the potential mechanisms of the anticancer action of SGLT-2 inhibitors and their possible future application in clinical oncology.

Renal Cell Carcinoma as a Metabolic Disease: An Update on Main Pathways, Potential Biomarkers, and Therapeutic Targets

Clear cell renal cell carcinoma (ccRCC) is the most frequent histological kidney cancer subtype. Over the last decade, significant progress has been made in identifying the genetic and metabolic alterations driving ccRCC development. In particular, an integrated approach using transcriptomics, metabolomics, and lipidomics has led to a better understanding of ccRCC as a metabolic disease. The metabolic profiling of this cancer could help define and predict its behavior in terms of aggressiveness, prognosis, and therapeutic responsiveness, and would be an innovative strategy for choosing the optimal therapy for a specific patient. This review article describes the current state-of-the-art in research on ccRCC metabolic pathways and potential therapeutic applications. In addition, the clinical implication of pharmacometabolomic intervention is analyzed, which represents a new field for novel stage-related and patient-tailored strategies according to the specific susceptibility to new classes of drugs.

18F-FDG PET/CT for assessing heterogeneous metabolic response between primary tumor and metastases and prognosis in non-small cell lung cancer

INTRODUCTION

This study aimed to use ¹⁸F-fluorodeoxyglucose positron emission tomography and/or computed tomography (¹⁸FDG-PET/CT) imaging to evaluate the heterogeneous metabolic response between primary tumor and metastases in NSCLC after therapy and explored its correlation with prognosis.

METHODS

The data of patients with NSCLC who underwent ¹⁸FDG-PET/CT before and after treatment were retrospectively analyzed. Heterogeneous metabolic response (HR), defined as the difference in metabolic response between any metastases and primary lesion, was evaluated using ¹⁸FDG-PET/CT. And the correlation between HR and clinical prognosis was also analyzed.

RESULTS

A total of 56 patients with NSCLC including 56 primary lesions and 491 metastases were enrolled in the study. 46.4% (26/56) of patients had HR, especially in patients with stage IV disease and whose metastases with high metabolic burden. HR was significantly correlated with poorer overall survival (OS) and progression-free survival (PFS) (P < .001 and P = .045, respectively). The multivariate analysis suggested that HR was an unfavorable independent prognostic factor for OS (HR = 4.36; 95% CI, 2.00-9.49; P < .001) but not for PFS (P = .469). HR between lymph node metastases was correlated with shorter OS (P < .001) but not with PFS (P = .370).

CONCLUSION

HR was observed between primary and metastatic lesions in NSCLC after treatment using PET/CT. HR is significantly associated with poor prognosis and is an independent prognostic factor for OS.

Impact of anti-diabetic sodium-glucose cotransporter 2 inhibitors on tumor growth of intractable hematological malignancy in humans

Under the dysfunction of mitochondria, cancer cells preferentially utilize both glycolytic and pentose phosphate pathways rather than electron transport chains to desperately generate adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH), classically recognized as the Warburg effect. Based on this background, the present study tested the hypothesis that anti-diabetic sodium-glucose cotransporter 2 (SGLT2) inhibitors would exert a tumor-suppressive impact on intractable human hematological malignancies via the modulation of glucose metabolism within cells and cell cycles. The level of mRNA for SGLT2 was remarkably elevated in leukemic cells from patients with adult T-cell leukemia (ATL), one of the most intractable blood cancers in humans, and as well as in two kinds of ATL cell lines (MT-1 and MT-2). Two kinds of SGLT2 inhibitors, Luseogliflozin and Tofogliflozin substantially suppressed the proliferation of MT-1 and MT-2 cells in both adherent and anchorage-independent culture conditions. Such a suppressive effect on tumor cell growth was reproduced by Luseogliflozin in leukemic cells in peripheral blood from patients with ATL. In MT-2 cells, both of SGLT2 inhibitors considerably attenuated glucose uptake, intracellular ATP levels, and NADPH production, resultantly enhancing cell cycle arrest at the G0/G1 phase. From the standpoint of metabolic oncology, the present study suggests that SGLT2 inhibitors would be a promising adjunctive option for the treatment of the most intractable human hematological malignancies like ATL.

Downregulated miR-18a and miR-92a synergistically suppress non-small cell lung cancer via targeting Sprouty 4

As a novel noncoding RNA cluster, miR-17-92 cluster include six members: miR-17, miR-18a, miR-19a, miR-19b-1, miR-20a, and miR-92a. Dysregulation of miR-17-92 has been proved to be connected with the advancement of a series of human diseases, but the roles of miR-17-92 cluster in non-small cell lung cancer (NSCLC) have not been absolutely elaborated. Herein, we determined that miR-17-92 cluster were upregulated significantly in NSCLC tissues, and the cell proliferation, migration and cycle progression of NSCLC were also facilitated under the function of miR-17-92 cluster. Sprouty 4 (SPRY4) was a direct target of miR-92a, and its overexpression restrained the exacerbation of NSCLC induced by miR-92a. Furthermore, the tumor xenograft assay showed that miR-92a facilitated tumor growth by inhibiting the expression of SPRY4 and mediating Epithelial-Mesenchymal Transition (EMT) in vivo. Finally, we looked into the synergistic effects of miR-92a and miR-18a on NSCLC, and found that antagomiR-18a treatment arrested the tumor growth rate of xenografted mice markedly.

Glucose transporters as markers of diagnosis and prognosis in cancer diseases

The primary metabolic substrate for cells is glucose, which acts as both a source of energy and a substrate in several processes. However, being lipophilic, the cell membrane is impermeable to glucose and specific carrier proteins are needed to allow transport. In contrast to normal cells, cancer cells are more likely to generate energy by glycolysis; as this process generates fewer molecules of adenosine triphosphate (ATP) than complete oxidative breakdown, more glucose molecules are needed. The increased demand for glucose in cancer cells is satisfied by overexpression of a number of glucose transporters, and decreased levels of others. As specific correlations have been observed between the occurrence of cancer and the expression of glucose carrier proteins, the presence of changes in expression of glucose transporters may be treated as a marker of diagnosis and/or prognosis for cancer patients.

Sodium-glucose cotransporter-2 inhibitors: Understanding the mechanisms for therapeutic promise and persisting risks

In a healthy person, the kidney filters nearly 200 g of glucose per day, almost all of which is reabsorbed. The primary transporter responsible for renal glucose reabsorption is sodium-glucose cotransporter-2 (SGLT2). Based on the impact of SGLT2 to prevent renal glucose wasting, SGLT2 inhibitors have been developed to treat diabetes and are the newest class of glucose-lowering agents approved in the United States. By inhibiting glucose reabsorption in the proximal tubule, these agents promote glycosuria, thereby reducing blood glucose concentrations and often resulting in modest weight loss. Recent work in humans and rodents has demonstrated that the clinical utility of these agents may not be limited to diabetes management: SGLT2 inhibitors have also shown therapeutic promise in improving outcomes in heart failure, atrial fibrillation, and, in preclinical studies, certain cancers. Unfortunately, these benefits are not without risk: SGLT2 inhibitors predispose to euglycemic ketoacidosis in those with type 2 diabetes and, largely for this reason, are not approved to treat type 1 diabetes. The mechanism for each of the beneficial and harmful effects of SGLT2 inhibitors-with the exception of their effect to lower plasma glucose concentrations-is an area of active investigation. In this review, we discuss the mechanisms by which these drugs cause euglycemic ketoacidosis and hyperglucagonemia and stimulate hepatic gluconeogenesis as well as their beneficial effects in cardiovascular disease and cancer. In so doing, we aim to highlight the crucial role for selecting patients for SGLT2 inhibitor therapy and highlight several crucial questions that remain unanswered.

Glucose transport in lymphocytes

Glucose uptake into lymphocytes is accomplished by non-concentrative glucose carriers of the GLUT family (GLUT1, GLUT3, GLUT4, GLUT6) and/or by the Na⁺-coupled glucose carrier SGLT1. The latter accumulates glucose against glucose gradients and is still effective at very low extracellular glucose concentrations. Signaling involved in SGLT1 expression and activity includes protein kinase A (PKA), protein kinase C (PKC), serum- and glucocorticoid-inducible kinase (SGK1), AMP-activated kinase (AMPK), and Janus kinases (JAK2 and JAK3). Glucose taken up is partially stored as glycogen. In hypoxic environments, such as in tumors as well as infected and inflamed tissues, lymphocytes depend on energy production from glycogen-dependent glycolysis. The lack of SGLT1 may compromise glycogen storage and thus lymphocyte survival and function in hypoxic tissues. Accordingly, in mice, genetic knockout of sglt1 compromised bacterial clearance following Listeria monocytogenes infection leading to an invariably lethal course of the disease. Whether the effect was due to the lack of sglt1 in lymphocytes or in other cell types still remains to be determined. Clearly, additional experimental effort is required to define the role of glucose transport by GLUTs and particularly by SGLT1 for lymphocyte survival and function, as well as orchestration of the host defense against tumors and bacterial infections.

Heterogeneity of Glucose Transport in Lung Cancer

Increased glucose uptake is a known hallmark of cancer. Cancer cells need glucose for energy production via glycolysis and the tricarboxylic acid cycle, and also to fuel the pentose phosphate pathway, the serine biosynthetic pathway, lipogenesis, and the hexosamine pathway. For this reason, glucose transport inhibition is an emerging new treatment for different malignancies, including lung cancer. However, studies both in animal models and in humans have shown high levels of heterogeneity in the utilization of glucose and other metabolites in cancer, unveiling a complexity that is difficult to target therapeutically. Here, we present an overview of different levels of heterogeneity in glucose uptake and utilization in lung cancer, with diagnostic and therapeutic implications.

Sodium-Dependent Glucose Transporter 1 (SGLT1) Stabled by HER2 Promotes Breast Cancer Cell Proliferation by Activation of the PI3K/Akt/mTOR Signaling Pathway in HER2+ Breast Cancer

Aerobic glycolysis is a hallmark of tumor cells. SGLT1 plays a vital role in glucose metabolism. However, whether SGLT1 could promote cell growth and proliferation in breast cancer remains unclear. Here, we investigated the expression of SGLT1 in breast cancer and examined its role in malignant behavior and prognosis. Further, we examined the SGLT1 expression in breast cancer tissues and its relationship with clinicopathologic characteristics. We clarified that SGLT1 was overexpressed in HER2+ breast cancer cell lines and was affected by HER2 status. We further found that SGLT1 affected breast cancer cell proliferation and patient survival by mediating cell survival pathway activation. SGLT1 was overexpressed in HER2+ breast cancers and associated with lymph node metastasis and HER2+ status. Inhibition of HER2 decreased SGLT1 expression, and the extracellular acidification rate was also reduced in the UACC812 and SKBR3 cell lines. These changes could be reversed by proteasome inhibitor treatment. Knockdown of SGLT1 blocked PI3K/Akt/mTOR signaling, thereby inhibiting cell proliferation. Further, we demonstrated that high SGLT1 was significantly correlated with shorter survival in all breast cancer patients and specifically in HER2+ breast cancer patients. Therefore, we conclude that SGLT1 is overexpressed in HER2+ breast cancer, thereby promoting cell proliferation and shortening survival by activating PI3K/Akt/mTOR signaling. This study submits that SGLT1 is promising not only as a novel biomarker of HER2+ breast cancer subtype but also as a potential drug target.

Canagliflozin reduces cisplatin uptake and activates Akt to protect against cisplatin-induced nephrotoxicity

Cisplatin is a widely used chemotherapy drug with notorious nephrotoxicity. Na⁺-glucose cotransporter 2 inhibitors are a class of novel antidiabetic agents that may have other effects in the kidneys besides blood glucose control. In the present study, we demonstrated that canagliflozin significantly attenuates cisplatin-induced nephropathy in C57BL/6 mice and suppresses cisplatin induced renal proximal tubular cell apoptosis in vitro. The protective effect of canagliflozin was associated with inhibition of p53, p38 and JNK activation. Mechanistically, canagliflozin partially reduced cisplatin uptake by kidney tissues in mice and renal tubular cells in culture. In addition, canagliflozin enhanced the activation of Akt and inhibited the mitochondrial pathway of apoptosis during cisplatin treatment. The protective effect of canagliflozin was diminished by the phosphatidylinositol 3-kinase/Akt inhibitor LY294002. Notably, canagliflozin did not affect the chemotherapeutic efficacy of cisplatin in A549 and HCT116 cancer cell lines. These results suggest a new application of canagliflozin for renoprotection in cisplatin chemotherapy. Canagliflozin may protect kidneys by reducing cisplatin uptake and activating cell survival pathways.

Sodium homeostasis in the tumour microenvironment

The concentration of sodium ions (Na+) is raised in solid tumours and can be measured at the cellular, tissue and patient levels. At the cellular level, the Na+ gradient across the membrane powers the transport of H+ ions and essential nutrients for normal activity. The maintenance of the Na+ gradient requires a large proportion of the cell's ATP. Na+ is a major contributor to the osmolarity of the tumour microenvironment, which affects cell volume and metabolism as well as immune function. Here, we review evidence indicating that Na+ handling is altered in tumours, explore our current understanding of the mechanisms that may underlie these alterations and consider the potential consequences for cancer progression. Dysregulated Na+ balance in tumours may open opportunities for new imaging biomarkers and re-purposing of drugs for treatment.

Trilobatin, a Novel SGLT1/2 Inhibitor, Selectively Induces the Proliferation of Human Hepatoblastoma Cells

Studies have indicated that Na⁺-d-glucose co-transporter (SGLT) inhibitors had anti-proliferative activity by attenuating the uptake of glucose in several tumor cell lines. In this study, the molecular docking showed that, trilobatin, one of the dihydrochalcones from leaves of Lithocarpus polystachyus Rehd., might be a novel inhibitor of SGLT1 and SGLT2, which evidently attenuated the uptake of glucose in vitro and in vivo. To our surprise, we observed that trilobatin did not inhibit, but promoted the proliferation of human hepatoblastoma HepG2 and Huh 7 cells when it was present at high concentrations. At the same time, incubation with high concentrations of trilobatin arrested the cell cycle at S phase in HepG2 cells. We also found that treatment with trilobatin had no significant effect on the expression of hepatitis B x-interacting protein (HBXIP) and hepatocyte nuclear factor (HNF)-4α, the two key regulators of hepatocyte proliferation. Taken together, although trilobatin worked as a novel inhibitor of SGLTs to attenuate the uptake of glucose, it also selectively induced the cell proliferation of HepG2 cells, suggesting that not all the SGLT inhibitors inhibited the proliferation of tumor cells, and further studies are needed to assess the anti-cancer potentials of new glucose-lowering agents.

Sodium-glucose cotransporters: new targets of cancer therapy?

Glucose, the key source of metabolic energy, is imported into cells by two categories of transporters: 1) facilitative glucose transporters (GLUTs) and 2) secondary active sodium-glucose cotransporters (SGLTs). Cancer cells have an increased demand for glucose uptake and utilisation compared to normal cells. Previous studies have demonstrated the overexpression of GLUTs, mainly GLUT1, in many cancer types. As the current standard positron emission tomography (PET) tracer 2-deoxy-2-(18F)fluoro-D-glucose (2-FDG) for imaging tumour cells via GLUT1 lacks in sensitivity and specificity, it may soon be replaced by the newly designed, highly sensitive and specific SGLT tracer α-methyl-4-(F-18)fluoro-4-deoxy-Dglucopyranoside (Me-4FDG) in clinical detection and tumour staging. This tracer has recently demonstrated the functional activity of SGLT in pancreatic, prostate, and brain cancers. The mRNA and protein expression of SGLTs have also been reported in colon/colorectal, lung, ovarian, head, neck, and oral squamous carcinomas. So far, SGLTs have been poorly investigated in cancer, and their protein expression and localisation are often controversial due to a lack of specific SGLT antibodies. In this review, we describe current knowledge concerning SGLT1 and SGLT2 (over)expression in various cancer types. The findings of SGLTs in malignant cells may help in developing novel cancer therapies with SGLT2 or SGLT1/SGLT2 inhibitors already used in diabetes mellitus treatment.

Licochalcone A induces apoptotic cell death via JNK/p38 activation in human nasopharyngeal carcinoma cells

Licochalcone A is widely studied in different fields and possesses antiasthmatic, antibacterial, anti-inflammatory, antioxidative, and anticancer properties. Its antimalignancy activity on renal, liver, lung, and oral cancer has been explored. However, limited studies have been conducted on the inhibitory effects of licochalcone A in human nasopharyngeal carcinoma cells. We determined cell viability using MTT assay. Cell cycle distribution and apoptotic cell death were measured via flow cytometry. Caspase activation and mitogen-activated protein kinase-related proteins in nasopharyngeal cancer cells in response to licochalcone A were identified by Western blot analysis. Results indicated that licochalcone A reduces cell viability and induces apoptosis, as evidenced by the upregulation of caspase-8 and caspase-9, caspase-3 activation, and cleaved-poly ADP-ribose polymerase expression. Treatment with licochalcone A significantly increases ERK1/2, p38, and JNK1/2 activation. Co-administration of a JNK inhibitor (JNK-IN-8) or p38 inhibitor (SB203580) abolishes the activation of caspase-9, caspase-8, and caspase-3 protein expression during licochalcone A treatment. These findings indicate that licochalcone A exerts a cytostatic effect through apoptosis by targeting the JNK/p38 pathway in human nasopharyngeal carcinoma cells. Therefore, licochalcone A is a promising therapeutic agent for the treatment of human nasopharyngeal cancer cells.

Immunohistochemical expressionof sodium-dependent glucose transporter - 2 (SGLT-2) in clear cell renal carcinoma: possible prognostic implications

Purpose:

Glucose is a major energy resource for tumor cell survival and growth, and its influx into cells is mainly carried out by facilitative glucose transporters (GLUTs). Sodium - dependent glucose transporters (SGLTs) have been highlighted as playing important roles in diabetic treatment. However, their potential roles in cancer remain unclear. We examined expression patterns of SGLTs in tumor tissues together with conventional pathological variables to determine prognostic significance in patients with renal cell carcinoma (RCC).

Materials and Methods:

Nephrectomy specimens were obtained from 68 patients. GLUT - 1, - 2 and SGLT - 1, - 2 expression in tumor and adjacent normal tissues were analyzed by immunohistochemical staining, and intensity was quantified using an image analyzer.

Results:

The four glucose transporters evaluated were broadly distributed in tumor tissues as well as throughout the normal parenchyma. There was no significant correlation between transporter expression and conventional pathological variables. However, increased SGLT - 2 expression was significantly associated with shorter overall survival (p < 0.01), regardless of metastatic status.

Conclusions:

We propose possible prognostic significance of SGLT - 2 expression in human RCC. Given that glucose is a major energy resource for tumor cells and that glucose transport is largely mediated by SGLT, SGLT - 2 may serve as a possible therapeutic target in RCC.

Sodium-glucose transporter 2 is a diagnostic and therapeutic target for early-stage lung adenocarcinoma

The diagnostic definition of indeterminate lung nodules as malignant or benign poses a major challenge for clinicians. We discovered a potential marker, the sodium-dependent glucose transporter 2 (SGLT2), whose activity identified metabolically active lung premalignancy and early-stage lung adenocarcinoma (LADC). We found that SGLT2 is expressed early in lung tumorigenesis and is found specifically in premalignant lesions and well-differentiated adenocarcinomas. SGLT2 activity could be detected in vivo by positron emission tomography (PET) with the tracer methyl 4-deoxy-4-[18F] fluoro-alpha-d-glucopyranoside (Me4FDG), which specifically detects SGLT activity. Using a combination of immunohistochemistry and Me4FDG PET, we identified high expression and functional activity of SGLT2 in lung premalignancy and early-stage/low-grade LADC. Furthermore, selective targeting of SGLT2 with FDA-approved small-molecule inhibitors, the gliflozins, greatly reduced tumor growth and prolonged survival in autochthonous mouse models and patient-derived xenografts of LADC. Targeting SGLT2 in lung tumors may intercept lung cancer progression at early stages of development by pairing Me4FDG PET imaging with therapy using SGLT2 inhibitors.

MicroRNA-296, a suppressor non-coding RNA, downregulates SGLT2 expression in lung cancer

Non-small cell lung cancer (NSCLC) is one of the most common types of cancer worldwide and has the highest mortality rate in China. MicroRNAs (miRNAs or miRs) are involved in tumorigenesis and their important role in cancer is becoming increasingly apparent. The expression of miR‑296‑5p in particular has been shown to be significantly downregulated in lung cancer. Sodium-glucose co-transporter-2 [SGLT2, also known as solute carrier family 5 member 2 (SLC5A2)] is an oncogene that promotes tumorigenesis. In this study, we aimed to determine the role of miR‑296‑5p in lung cancer and whether this involves the targeting of SGLT2. For this purpose, we examined miR‑296‑5p and SGLT2 expression in human lung cancer samples and cell lines by RT-qPCR and western blot analysis. In addition, the data analysis website TCGA was used for survival analysis with respect to SGLT2 expression. The effects of miR‑296‑5p were also examined on cell proliferation and cell cycle progression using respective assays. The results demonstrate that miR‑296‑5p is significantly downregulated in NSCLC tissues. Additionally, it is demonstrated that SGLT2 is directly targeted by miR‑296‑5p. Furthermore, our data reveal that the knockdown of SGLT2 using siRNA inhibits cell proliferation and impedes cell cycle progression. Collectively, data suggest that miR‑296‑5p not only inhibits NSCLC by downregulating SGLT2 expression, but also acts as a novel regulator of aberrant lung cancer cells to limit lung cancer progression.

Comparison of GLUT-1, SGLT-1, and SGLT-2 expression in false-negative and true-positive lymph nodes during the 18F-FDG PET/CT mediastinal nodal staging of non-small cell lung cancer

INTRODUCTION

Although positron emission tomography (PET) with 2-deoxy-2-[fluorine-18]fluoro-d-glucose integrated with computed tomography (CT), (¹⁸F-FDG PET/CT), has recently improved the mediastinal nodal staging of non-small cell lung cancer (NSCLC), this method can show false negativity. We immunohistochemically investigated the expression of glucose transporters (GLUT-1, SGLT-1, and SGLT-2) in false negative and true positive mediastinal nodes via ¹⁸F-FDG PET/CT.

METHODS

We investigated patients with clinically-diagnosed N0/pathological N2 diseases and patients with clinically-diagnosed N2/pathological N2 disease. The patients who were included in this study were evaluated using ¹⁸F-FDG PET/CT followed by surgical resection between January 2004 and December 2015. The expression of GLUT-1, SGLT-1, and SGLT-2 in the metastatic mediastinal lymph nodes, and clinicopathological variables such as primary tumor size, lymph node size, histological type, and SUV_max of the primary lesion, were compared between false negative nodes and true positive nodes.

RESULTS

The total number of PET false negative metastatic mediastinal lymph nodes was 22 in the 17 patients who were clinical N0/pathological N2, and the number of PET true positives was 15 in the 11 patients who were clinical N2/pathological N2. GLUT-1 expression was positive in five false negative nodes and 10 true positive nodes. SGLT-2 expression was positive in 12 false negative nodes and one true positive node, whereas both false negative and true positive nodes showed no SGLT-1 staining. Univariate analysis showed that the reduced expression of GLUT-1 (P = 0.015), and overexpression of SGLT-2 (P = 0.004) were the significant causative factors for false negative nodes. Multivariate analysis also showed that the reduced expression of GLUT-1 (P = 0.012) and overexpression of SGLT-2 (P = 0.006) were the significant causative factors for false negative nodes.

CONCLUSION

It suggests that the reduced expression of GLUT-1 and overexpression of SGLT-2 are associated with false-negative lymph node metastases in NSCLC.

Black bean peptides inhibit glucose uptake in Caco-2 adenocarcinoma cells by blocking the expression and translocation pathway of glucose transporters

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Common bean protein fractions decreased glucose uptake in colorectal cancer cells.

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Protein fractions decreased SGLT1 and GLUT2 gene and protein expression and translocation.

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Black bean protein fractions could be used as anticancer drug adjuvants.

The objective was to evaluate the effect of black bean protein fraction (PFRA), and its derived peptides on glucose uptake, SGLT1 and GLUT2 expression and translocation on Caco-2 cells. The effect of treatments was evaluated on glucose uptake, protein expression and localization and gene expression on Caco-2 cells. PFRA (10 mg/mL) lowered glucose uptake from 27.4% after 30 min to 33.9% after 180 min of treatment compared to untreated control (p < 0.05). All treatments lowered GLUT2 expression after 30 min of treatment compared to untreated control (31.4 to 48.6%, p < 0.05). Similarly, after 24 h of treatment, GLUT2 was decreased in all treatments (23.5% to 48.9%) (p < 0.05). SGLT1 protein expression decreased 18.3% for LSVSVL (100 μM) to 45.1% for PFRA (10 mg/mL) after 24 h. Immunofluorescence microscopy showed a decrease in expression and membrane translocation of GLUT2 and SGLT1 for all treatments compared to untreated control (p < 0.05). Relative gene expression of SLC2A2 (GLUT2) and SLC5A1 (SGLT1) was downregulated significantly up to two-fold change compared to the untreated control after 24 h treatment. Black bean protein fractions are an inexpensive, functional ingredient with significant biological potential to reduce glucose uptake and could be used as an adjuvant in the treatment of colorectal cancer.

Sodium-glucose transporter as a novel therapeutic target in disease

Glucose is the primary energy fuel of life. A glucose transporter, the sodium-glucose transporter (SGLT), is receiving attention as a novel therapeutic target in disease. This review summarizes the physiological role of SGLT in cerebral ischemia, cancer, cardiac disease, and intestinal ischemia, which has encouraged analysis of SGLT function. In cerebral ischemia and cardiomyopathy, SGLT-1 is involved in worsening of the injury. In addition, SGLT-1 promotes the development of cancer. On the other hand, SGLT-1 has a protective effect against cardiac and intestinal ischemia. Interestingly, SGLT-1 expression levels are increased in some diseased tissue, such as in cerebral ischemia and cancer. This suggests that SGLT-1 may have an important role in many diseases. This review discusses the potential of SGLT as a target for novel therapeutic agents.

Is it time to think about the sodium glucose co-transporter 2 sympathetically?

Disturbances in glucose homeostasis are a key feature of the metabolic syndrome and type 2 diabetes. Renal glucose reabsorption is an important factor in glycaemic control. Glucose reabsorption in the proximal tubules is mediated by the sodium glucose co-transporter 2. The capacity for glucose reabsorption is increased in type 2 diabetes and contributes significantly to hyperglycaemia and impaired glucose control. Understanding the mechanisms underpinning the regulation of the sodium glucose co-transporter 2 is therefore of high clinical relevance. However, despite recent advances in the field and the availability of pharmacological inhibitors of this glucose transporter for the treatment of type 2 diabetes, the mechanisms that regulate sodium glucose co-transporter 2 expression are not fully understood. The sympathetic nervous system is an important modulator of glucose homeostasis, and sympathetic hyperactivity is a characteristic feature of obesity, the metabolic syndrome and type 2 diabetes. Sympathetic inhibition either achieved pharmacologically or by renal sympathetic denervation has been associated with improved glucose control. Importantly, sympathetic nerves innervate the proximal tubules of the kidney where they have been shown to regulate the expression of other transporters such as the sodium hydrogen exchanger 3. This review aims to explore the evidence for the regulation of sodium glucose co-transporter 2-mediated glucose reabsorption by the sympathetic nervous system.

Chemical Approach to Positional Isomers of Glucose-Platinum Conjugates Reveals Specific Cancer Targeting through Glucose-Transporter-Mediated Uptake in Vitro and in Vivo

Glycoconjugation is a promising strategy for specific targeting of cancer. In this study, we investigated the effect of d-glucose substitution position on the biological activity of glucose-platinum conjugates (Glc-Pts). We synthesized and characterized all possible positional isomers (C1α, C1β, C2, C3, C4, and C6) of a Glc-Pt. The synthetic routes presented here could, in principle, be extended to prepare glucose conjugates with different active ingredients, other than platinum. The biological activities of the compounds were evaluated both in vitro and in vivo. We discovered that varying the position of substitution of d-glucose alters not only the cellular uptake and cytotoxicity profile but also the GLUT1 specificity of resulting glycoconjugates, where GLUT1 is glucose transporter 1. The C1α- and C2-substituted Glc-Pts (1α and 2) accumulate in cancer cells most efficiently compared to the others, whereas the C3-Glc-Pt (3) is taken up least efficiently. Compounds 1α and 2 are more potent compared to 3 in DU145 cells. The α- and β-anomers of the C1-Glc-Pt also differ significantly in their cellular uptake and activity profiles. No significant differences in uptake of the Glc-Pts were observed in non-cancerous RWPE2 cells. The GLUT1 specificity of the Glc-Pts was evaluated by determining the cellular uptake in the absence and in the presence of the GLUT1 inhibitor cytochalasin B, and by comparing their anticancer activity in DU145 cells and a GLUT1 knockdown cell line. The results reveal that C2-substituted Glc-Pt 2 has the highest GLUT1-specific internalization, which also reflects the best cancer-targeting ability. In a syngeneic breast cancer mouse model overexpressing GLUT1, compound 2 showed antitumor efficacy and selective uptake in tumors with no observable toxicity. This study thus reveals the synthesis of all positional isomers of d-glucose substitution for platinum warheads with detailed glycotargeting characterization in cancer.

MAP17 Is a Necessary Activator of Renal Na+/Glucose Cotransporter SGLT2

The renal proximal tubule reabsorbs 90% of the filtered glucose load through the Na⁺-coupled glucose transporter SGLT2, and specific inhibitors of SGLT2 are now available to patients with diabetes to increase urinary glucose excretion. Using expression cloning, we identified an accessory protein, 17 kDa membrane-associated protein (MAP17), that increased SGLT2 activity in RNA-injected Xenopus oocytes by two orders of magnitude. Significant stimulation of SGLT2 activity also occurred in opossum kidney cells cotransfected with SGLT2 and MAP17. Notably, transfection with MAP17 did not change the quantity of SGLT2 protein at the cell surface in either cell type. To confirm the physiologic relevance of the MAP17-SGLT2 interaction, we studied a cohort of 60 individuals with familial renal glucosuria. One patient without any identifiable mutation in the SGLT2 coding gene (SLC5A2) displayed homozygosity for a splicing mutation (c.176+1G>A) in the MAP17 coding gene (PDZK1IP1). In the proximal tubule and in other tissues, MAP17 is known to interact with PDZK1, a scaffolding protein linked to other transporters, including Na⁺/H⁺ exchanger 3, and to signaling pathways, such as the A-kinase anchor protein 2/protein kinase A pathway. Thus, these results provide the basis for a more thorough characterization of SGLT2 which would include the possible effects of its inhibition on colocalized renal transporters.

Cellular Internalization of Therapeutic Oligonucleotides by Peptide Amphiphile Nanofibers and Nanospheres

Oligonucleotides are promising drug candidates due to the exceptionally high specificity they exhibit toward their target DNA and RNA sequences. However, their poor pharmacokinetic and pharmacodynamic properties, in conjunction with problems associated with their internalization by cells, necessitates their delivery through specialized carrier systems for efficient therapy. Here, we investigate the effects of carrier morphology on the cellular internalization mechanisms of oligonucleotides by using self-assembled fibrous or spherical peptide nanostructures. Size and geometry were both found to be important parameters for the oligonucleotide internalization process; direct penetration was determined to be the major mechanism for the internalization of nanosphere carriers, whereas nanofibers were internalized by clathrin- and dynamin-dependent endocytosis pathways. We further showed that glucose conjugation to carrier nanosystems improved cellular internalization in cancer cells due to the enhanced glucose metabolism associated with oncogenesis, and the internalization of the glucose-conjugated peptide/oligonucleotide complexes was found to be dependent on glucose transporters present on the surface of the cell membrane.

SGLT1 activity in lung alveolar cells of diabetic rats modulates airway surface liquid glucose concentration and bacterial proliferation

High glucose concentration in the airway surface liquid (ASL) is an important feature of diabetes that predisposes to respiratory infections. We investigated the role of alveolar epithelial SGLT1 activity on ASL glucose concentration and bacterial proliferation. Non-diabetic and diabetic rats were intranasally treated with saline, isoproterenol (to increase SGLT1 activity) or phlorizin (to decrease SGLT1 activity); 2 hours later, glucose concentration and bacterial proliferation (methicillin-resistant Sthaphylococcus aureus, MRSA and Pseudomonas aeruginosa, P. aeruginosa) were analyzed in bronchoalveolar lavage (BAL); and alveolar SGLT1 was analyzed by immunohistochemistry. BAL glucose concentration and bacterial proliferation increased in diabetic animals: isoproterenol stimulated SGLT1 migration to luminal membrane, and reduced (50%) the BAL glucose concentration; whereas phlorizin increased the BAL glucose concentration (100%). These regulations were accompanied by parallel changes of in vitro MRSA and P. aeruginosa proliferation in BAL (r = 0.9651 and r = 0.9613, respectively, Pearson correlation). The same regulations were observed in in vivo P. aeruginosa proliferation. In summary, the results indicate a relationship among SGLT1 activity, ASL glucose concentration and pulmonary bacterial proliferation. Besides, the study highlights that, in situations of pulmonary infection risk, such as in diabetic subjects, increased SGLT1 activity may prevent bacterial proliferation whereas decreased SGLT1 activity can exacerbate it.

A Potent Glucose-Platinum Conjugate Exploits Glucose Transporters and Preferentially Accumulates in Cancer Cells

Three rationally designed glucose-platinum conjugates (Glc-Pts) were synthesized and their biological activities evaluated. The Glc-Pts, 1-3, exhibit high levels of cytotoxicity toward a panel of cancer cells. The subcellular target and cellular uptake mechanism of the Glc-Pts were elucidated. For uptake into cells, Glc-Pt 1 exploits both glucose and organic cation transporters, both widely overexpressed in cancer. Compound 1 preferentially accumulates in and annihilates cancer, compared to normal epithelial, cells in vitro.

EGFR kinase-dependent and kinase-independent roles in clear cell renal cell carcinoma

Epidermal growth factor receptor (EGFR) is associated with progression of many epithelial malignancies and represents a significant therapeutic target. Although clear cell renal cell carcinoma (CCRCC) has been widely investigated for EGFR molecular alterations, genetic evidences of EGFR gene activating mutations and/or gene amplification have been rarely confirmed in the literature. Therefore, until now EGFR-targeted therapies in clinical trials have been demonstrated unsuccessful. New evidence has been given about the interactions between EGFR and the sodium glucose co-transporter-1 (SGLT1) in maintaining the glucose basal intracellular level to favour cancer cell growth and survival; thus a new functional role may be attributed to EGFR, regardless of its kinase activity. To define the role of EGFR in CCRCC an extensive investigation of genetic changes and functional kinase activities was performed in a series of tumors by analyzing the EGFR mutational status and expression profile, together with the protein expression of downstream signaling pathways members. Furthermore, we investigated the co-expression of EGFR and SGLT1 proteins and their relationships with clinic-pathological features in CCRCC. EGFR protein expression was identified in 98.4% of CCRCC. Furthermore, it was described for the first time that SGLT1 is overexpressed in CCRCC (80.9%), and that co-expression with EGFR is appreciable in 79.4% of the tumours. Moreover, the activation of downstream EGFR pathways was found in about 79.4% of SGLT1-positive CCRCCs. The mutational status analysis of EGFR failed to demonstrate mutations on exons 18 to 24 and the presence of EGFR-variantIII (EGFRvIII) in all CCRCCs analyzed. FISH analysis revealed absence of EGFR amplification, and high polysomy of chromosome 7. Finally, the EGFR gene expression profile showed gene overexpression in 38.2% of CCRCCs. Our study contributes to define the complexity of EGFR role in CCRCC, identifying its bivalent kinase-dependent and kinase-independent functions, both potentially involved in CCRCC progression. These results might have important implications on therapeutic approaches to CCRCC, since the disruption of the interaction between EGFR/SGLT1, mediated by anti-EGFR antibodies and/or SGLT1 inhibitors, might constitute a novel therapeutic target for CCRCC treatment, and new clinical trials should be evaluated on the basis of this therapeutic proposal.

L-methionase: a therapeutic enzyme to treat malignancies

Cancer is an increasing cause of mortality and morbidity throughout the world. L-methionase has potential application against many types of cancers. L-Methionase is an intracellular enzyme in bacterial species, an extracellular enzyme in fungi, and absent in mammals. L-Methionase producing bacterial strain(s) can be isolated by 5,5′-dithio-bis-(2-nitrobenzoic acid) as a screening dye. L-Methionine plays an important role in tumour cells. These cells become methionine dependent and eventually follow apoptosis due to methionine limitation in cancer cells. L-Methionine also plays an indispensable role in gene activation and inactivation due to hypermethylation and/or hypomethylation. Membrane transporters such as GLUT1 and ion channels like Na²⁺, Ca²⁺, K⁺, and Cl⁻ become overexpressed. Further, the α-subunit of ATP synthase plays a role in cancer cells growth and development by providing them enhanced nutritional requirements. Currently, selenomethionine is also used as a prodrug in cancer therapy along with enzyme methionase that converts prodrug into active toxic chemical(s) that causes death of cancerous cells/tissue. More recently, fusion protein (FP) consisting of L-methionase linked to annexin-V has been used in cancer therapy. The fusion proteins have advantage that they have specificity only for cancer cells and do not harm the normal cells.

A Review on the Relationship between SGLT2 Inhibitors and Cancer

Risk of increasing breast and bladder cancer remains a safety issue of SGLT2 (sodium glucose cotransporter type 2) inhibitors, a novel class of antidiabetic agent. We reviewed related papers published before January 29, 2014, through Pubmed search. Dapagliflozin and canagliflozin are the first two approved SGLT2 inhibitors for diabetes therapy. Although preclinical animal toxicology did not suggest a cancer risk of dapagliflozin and overall tumor did not increase, excess numbers of female breast cancer and male bladder cancer were noted in preclinical trials (without statistical significance). This concern of cancer risk hindered its approval by the US FDA in January, 2012. New clinical data suggested that the imbalance of bladder and breast cancer might be due to early diagnosis rather than a real increase of cancer incidence. No increased risk of overall bladder or breast cancer was noted for canagliflozin. Therefore, the imbalance observed with dapagliflozin treatment should not be considered as a class effect of SGLT2 inhibitors and the relationship with cancer for each specific SGLT2 inhibitor should be examined individually. Relationship between SGLT2 inhibition and cancer formation is still inconclusive and studies with larger sample size, longer exposure duration, and different ethnicities are warranted.

Ionizing radiation, ion transports, and radioresistance of cancer cells

The standard treatment of many tumor entities comprises fractionated radiation therapy which applies ionizing radiation to the tumor-bearing target volume. Ionizing radiation causes double-strand breaks in the DNA backbone that result in cell death if the number of DNA double-strand breaks exceeds the DNA repair capacity of the tumor cell. Ionizing radiation reportedly does not only act on the DNA in the nucleus but also on the plasma membrane. In particular, ionizing radiation-induced modifications of ion channels and transporters have been reported. Importantly, these altered transports seem to contribute to the survival of the irradiated tumor cells. The present review article summarizes our current knowledge on the underlying mechanisms and introduces strategies to radiosensitize tumor cells by targeting plasma membrane ion transports.

Up-regulation of Na(+)-coupled glucose transporter SGLT1 by caveolin-1

The Na(+)-coupled glucose transporter SGLT1 (SLC5A1) accomplishes concentrative cellular glucose uptake even at low extracellular glucose concentrations. The carrier is expressed in renal proximal tubules, small intestine and a variety of nonpolarized cells including several tumor cells. The present study explored whether SGLT1 activity is regulated by caveolin-1, which is known to regulate the insertion of several ion channels and carriers in the cell membrane. To this end, SGLT1 was expressed in Xenopus oocytes with or without additional expression of caveolin-1 and electrogenic glucose transport determined by dual electrode voltage clamp experiments. In SGLT1-expressing oocytes, but not in oocytes injected with water or caveolin-1 alone, the addition of glucose to the extracellular bath generated an inward current (Ig), which was increased following coexpression of caveolin-1. Kinetic analysis revealed that caveolin-1 increased maximal Ig without significantly modifying the glucose concentration required to trigger half maximal Ig (KM). According to chemiluminescence and confocal microscopy, caveolin-1 increased SGLT1 protein abundance in the cell membrane. Inhibition of SGLT1 insertion by brefeldin A (5μM) resulted in a decline of Ig, which was similar in the absence and presence of caveolin-1. In conclusion, caveolin-1 up-regulates SGLT1 activity by increasing carrier protein abundance in the cell membrane, an effect presumably due to stimulation of carrier protein insertion into the cell membrane.