High glucose and insulin differentially modulates proliferation in MCF-7 and MDA-MB-231 cells

Does insulin make breast cancer cells resistant to doxorubicin toxicity?

The effects of insulin on the doxorubicin (Dox) sensitivity of breast cancer cell line MCF-7 and its Dox-resistant counterpart MCF-7/Dox were studied and glucose metabolism, content of essential minerals, and the expression of several microRNAs in these cells upon exposure to insulin and Dox were compared. Cell viability colorimetric assay, colorimetric enzymatic technique, flow cytometry, immunocytochemical techniques, inductively-coupled plasma atomic emission spectroscopy, and quantitative polymerase chain reaction were used in the study. We found that insulin in high concentration significantly suppressed Dox toxicity, especially in parental MCF-7 cell line. The increase in proliferative activity triggered by insulin in MCF-7 but not MCF-7/Dox cells occurred in the setting of the increased level of specific binding sites for insulin and increased glucose uptake. Insulin treatment of MCF-7 cells in low and high concentrations resulted in the increase of Mg, Ca, and Zn content while in DOX-resistant cells, only Mg content increased upon exposure to insulin. High concentration of insulin increased the expression of kinase Akt1, P-glycoprotein 1 (P-gp1) and DNA excision repair protein ERCC-1 in MCF-7 cells, while in MCF-7/Dox cells, Akt1 expression decreased, and cytoplasmic expression of P-gp1 increased. In addition, insulin treatment affected expression of miR-122-5p, miR-133a-3p, miR-200b-3p, and miR-320a-3p. The decreased manifestation of biological effects of insulin in Dox-resistant cells could be partly explained by the different patterns of energy metabolism in MCF-7 cells and their Dox-resistant counterpart.

Effects of photobiomodulation by low-power lasers and LEDs on the viability, migration, and invasion of breast cancer cells

Among the malignant tumors, breast cancer is the most commonly diagnosed worldwide, being the most prevalent in women. Photobiomodulation has been used for wound healing, swelling and pain reduction, and muscle repair. The application of photobiomodulation in cancer patients has been controversial. Therefore, a better understanding of radiation-induced effects involved in photobiomodulation on cancer cells is needed. Thus, this study aimed to investigate the effects of exposure to low-power lasers and LEDs on cell viability, migration, and invasion in human breast cancer cells. MCF-7 and MDA-MB-231 cells were irradiated with a low-power red laser (23, 46, and 69 J/cm2, 0.77 W/cm2) and blue LED (160, 321, and 482 J/cm2, 5.35 W/cm2), alone or in combination. Cell viability was assessed using the WST-1 assay, cell migration was evaluated using the wound healing assay, and cell invasion was performed using the Matrigel transwell assay. Viability and migration were not altered in MCF-7 and MDA-MB-231 cultures after exposure to low-power red laser and blue LED. However, there was a decrease in cell invasion from the cultures of the two cell lines evaluated. The results suggest that photobiomodulation induced by low-power red laser and blue LED does not alter cell viability and migration but decreases cell invasion in human breast cancer cells.

Assessing the Link between Diabetic Metabolic Dysregulation and Breast Cancer Progression

Diabetes mellitus is a burdensome disease that affects various cellular functions through altered glucose metabolism. Several reports have linked diabetes to cancer development; however, the exact molecular mechanism of how diabetes-related traits contribute to cancer progression is not fully understood. The current study aimed to explore the molecular mechanism underlying the potential effect of hyperglycemia combined with hyperinsulinemia on the progression of breast cancer cells. To this end, gene dysregulation induced by the exposure of MCF7 breast cancer cells to hyperglycemia (HG), or a combination of hyperglycemia and hyperinsulinemia (HGI), was analyzed using a microarray gene expression assay. Hyperglycemia combined with hyperinsulinemia induced differential expression of 45 genes (greater than or equal to two-fold), which were not shared by other treatments. On the other hand, in silico analysis performed using a publicly available dataset (GEO: GSE150586) revealed differential upregulation of 15 genes in the breast tumor tissues of diabetic patients with breast cancer when compared with breast cancer patients with no diabetes. SLC26A11, ALDH1A3, MED20, PABPC4 and SCP2 were among the top upregulated genes in both microarray data and the in silico analysis. In conclusion, hyperglycemia combined with hyperinsulinemia caused a likely unique signature that contributes to acquiring more carcinogenic traits. Indeed, these findings might potentially add emphasis on how monitoring diabetes-related metabolic alteration as an adjunct to diabetes therapy is important in improving breast cancer outcomes. However, further detailed studies are required to decipher the role of the highlighted genes, in this study, in the pathogenesis of breast cancer in patients with a different glycemic index.

Formulation and characterization of insulin nanoclusters for a controlled release

The growing interest in biopharmaceuticals combined with the challenges regarding formulation and delivery continues to encourage the development of new and improved formulations of this class of therapeutics. Nanoclusters (NCs) represent a type of formulation strategy where the biopharmaceutical is clustered in a reversible manner to function as both the therapeutic and the vehicle. In this study, insulin NCs (INCs) were formulated by a new methodology of first crosslinking proteins followed by desolvation. Crosslinking of the protein with the reducible DTSSP crosslinker improved control of the INC synthesis process to give INCs with a mean size of 198 ± 7 nm and a mean zeta potential of -39 ± 1 mV. Crosslinking and clustering of insulin did not induce cytotoxicity or major differences in the biological activity compared to the free unmodified protein. The potency of the crosslinked insulin and the INCs appeared slightly lower than that of the unmodified protein, and significantly higher doses of the INCs compared to the free protein were applied to achieve similar blood sugar lowering effects in vivo. Interestingly, the INCs allowed for high doses to be subcutaneously delivered with prolonged efficacy without being lethal in rats.

SIRT5 is involved in the proliferation and metastasis of breast cancer by promoting aerobic glycolysis

OBJECTIVE

Breast cancer (BC) is the most commonly diagnosed cancer among females and has a poor prognosis, breast invasive ductal carcinoma is the most common histological type. The occurrence and development of BC is closely related to aberrant glucose metabolism. In the hyperglycemic environment caused by abnormal glucose metabolism, hypoxia-inducible factor-1 alpha (HIF-1α) enables tumor cells to absorb large amounts of glucose and enhance glycolysis by inducing the expression of glucose transporter type1 (GLUT1) and glycolysis genes, thus promoting tumor cell proliferation and metastasis. Mitochondrial Sirtuin5 (SIRT5) plays a role in the rewiring of glucose metabolism during the progression of cancers. Thus, we aimed to elucidate whether SIRT5 promotes BC proliferation and metastasis by facilitating aerobic glycolysis in BC.

METHODS

The expression of SIRT5 in breast carcinoma tissue and cells was evaluated using immunohistochemical staining, western blot and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis to confirm the biological role of SIRT5 in breast carcinoma. We established a stable cell line with SIRT5 knockdown using lentiviral transduction in T47D cells to reduce SIRT5 expression and then evaluated the effect of SIRT5 on cells cultured in the presence of high glucose (4500 mg/L) and normal glucose (2000 mg/L) concentrations. Cell proliferation was detected using the CCK-8 assay, the cell cycle and cell apoptosis were measured using flow cytometry and Annexin V staining, and cell migration was tested by performing Celigo scratch and Transwell assays. The expression of PKM2, HK2, mTOR and HIF-1α, which play roles in aerobic glycolysis, was investigated using western blot.

RESULTS

SIRT5 was overexpressed in BC tissues compared with paired normal tissues. Prognostic and OS analyses showed that the SIRT5 expression level was an individual prognostic factor for patients with BC. SIRT5 knockdown inhibited proliferation and metastasis and slightly increased apoptosis in T47D cells under high-glucose conditions. Furthermore, the downregulation of HK2 and HIF-1α caused by SIRT5 knockdown was a high glucose-dependent process, while the downregulation of PKM2 was mediated by a high glucose-independent process.

CONCLUSIONS

SIRT5 is an independent prognostic factor for BC and contributes to cell proliferation and metastasis in a high glucose-dependent manner to some degree, which might be mediated by promoting aerobic glycolysis.

Selenium nanoparticles stimulate osteoblast differentiation via BMP-2/MAPKs/β-catenin pathway in diabetic osteoporosis

Aim: To evaluate whether selenium nanoparticles (SeNPs) can stimulate bone formation and inhibit the bone loss involved in hyperglycemia-induced osteoporosis. Methods: Rat osteoblastic UMR-106 cells were used for in vitro studies and female Sprague–Dawley rats were used for type 2 diabetes-associated osteoporosis in vivo study. Results: In vitro studies show that SeNPs promote osteoblast differentiation via modulating alkaline phosphatase (ALP) activity, and promoting calcium nodule formation and collagen content. The authors also provide evidence regarding the involvement of the BMP-2/MAPKs/β-catenin pathway in preventing diabetic osteoporosis. Further, in vivo and ex vivo studies suggested that SeNPs can preserve mechanical and microstructural properties of bone. Conclusion: To the best of our knowledge, this study provides the first evidence regarding the therapeutic benefits of SeNPs in preventing diabetes-associated bone fragility.

Differences in glucose concentration shows new perspectives in gastric cancer metabolism

Gastric cancer (GC) is among the deadliest cancers worldwide despite available therapies, highlighting the need for novel therapies and pharmacological agents. Metabolic deregulation is a potential study area for new anticancer targets, but the in vitro metabolic studies are controversial, as different ranges of glucose used in the culture medium can influence results. In this study, we evaluated cellular viability, glucose uptake, and LDH activity in gastric cell lines when exposed to different glucose concentrations: high (HG, 25 mM), low (LG, 5.5 mM), and free (FG, 0 mM) glucose mediums. Moreover, we evaluated how glucose variations may influence cellular phenotype and the expression of genes related to epithelial-mesenchymal transition (EMT), metabolism, and cancer development in metastatic GC cells (AGP-01). Results showed that in the FG metastatic cells evidenced higher viability when compared with other cell lines and that when exposed to either LG or HG mediums most of the phenotypic assays did not differ. However, cells exposed to LG increased colony formation and mRNA levels of metabolic-related genes when compared to HG medium. Our results recommend LG medium to metabolic studies once glucose concentration is closer to physiological levels. These findings are important to point out new relevant targets in metabolic reprogramming that can be alternatives to current chemotherapies in patients with metastatic GC.

Imaging Sub-Cellular Methionine and Insulin Interplay in Triple Negative Breast Cancer Lipid Droplet Metabolism

Triple negative breast cancer (TNBC) is a particularly aggressive cancer subtype that is difficult to diagnose due to its discriminating epidemiology and obscure metabolome. For the first time, 3D spatial and chemometric analyses uncover the unique lipid metabolome of TNBC under the tandem modulation of two key metabolites - insulin and methionine - using non-invasive optical techniques. By conjugating heavy water (D2O) probed Raman scattering with label-free two-photon fluorescence (TPF) microscopy, we observed altered de novo lipogenesis, 3D lipid droplet morphology, and lipid peroxidation under various methionine and insulin concentrations. Quantitative interrogation of both spatial and chemometric lipid metabolism under tandem metabolite modulation confirms significant interaction of insulin and methionine, which may prove to be critical therapeutic targets, and proposes a powerful optical imaging platform with subcellular resolution for metabolic and cancer research.

Hyperglycemic conditions proliferate triple negative breast cancer cells: role of ornithine decarboxylase

PURPOSE

Several cancer subtypes (pancreatic, breast, liver, and colorectal) rapidly advance to higher aggressive stages in diabetes. Though hyperglycemia has been considered as a fuel for growth of cancer cells, pathways leading to this condition are still under investigation. Cellular polyamines can modulate normal and cancer cell growth, and inhibitors of polyamine synthesis have been approved for treating colon cancer, however the role of polyamines in diabetes-mediated cancer advancement is unclear as yet. We hypothesized that polyamine metabolic pathway is involved with increased proliferation of breast cancer cells under high glucose (HG) conditions.

METHODS

Studies were performed with varying concentrations of glucose (5-25 mM) exposure in invasive, triple negative breast cancer cells, MDA-MB-231; non-invasive, estrogen/progesterone receptor positive breast cancer cells, MCF-7; and non-tumorigenic mammary epithelial cells, MCF-10A.

RESULTS

There was a significant increase in proliferation with HG (25 mM) at 48-72 h in both MDA-MB-231 and MCF-10A cells but no such effect was observed in MCF-7 cells. This was correlated to higher activity of ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine synthesis pathway. Inhibitor of polyamine synthesis (difluoromethylornithine, DFMO, 5 mM) was quite effective in suppressing HG-mediated cell proliferation and ODC activity in MDA-MB-231 and MCF-10A cells. Polyamine (putrescine) levels were significantly elevated with HG treatment in MDA-MB-231 cells. HG exposure also increased the metastasis of MDA-MB-231 cells.

CONCLUSIONS

Our cellular findings indicate that polyamine inhibition should be explored in patient population as a target for future chemotherapeutics in diabetic breast cancer.

The rate of aerobic glycolysis is a pivotal regulator of tumor progression

Purpose

Cancer cells depend on glucose metabolism via exclusive glycolysis pathway is named Aerobic glycolysis or Warburg effect. The aim of this study was investigation of different glucose accessibility conditions on the rate of Warburg effect and its impact on Hypoxia inducible factors-1 α (HIF-1 α)/vascular endothelium growth factor (VEGF) pathway in breast cancer cells lines.

Methods

MDA-MB-231 (Warburg phenomenon) and MCF-7 (oxidative) cell lines were cultured in DMEM and exposed to three different glucose accessibility medium for 48 h (5.5 mM as normal glucose (NG), 25 mM as high glucose (HG) and 2-Deoxyglucose (2-DG) as restricted glucose accessibility). Glucose uptake, intra/extracellular lactate and pyruvate, HIF-1α accumulation and vascular endothelium growth factor (VEGF) expression were evaluated by standard methods.

Results

Our results showed in NG condition both of cell lines produce lactate, but it was higher in MDA-MB-231. HG condition increased extracellular lactate in both cell lines especially in MCF-7 cells whereas intracellular lactate and pyruvate raised only in MCF-7. 2-DG decreased extracellular and intracellular lactate and pyruvate in both cell lines especially in MDA-MB-231. HIF-1α accumulation was detectable in NG condition in both cell lines. HG condition increased HIF-1α accumulation in MCF-7 cells but not in MDA-MB-231 and 2-DG decreased it in both call lines, especially in MDA-MB-231. Expression of VEGF had similar pattern with HIF-1α in different conditions.

Conclusions

Our findings revealed the rate of Warburg effect is an important indicator for tumor promotion and invasion due to its impacts on important transcription factors like HIF-1α.

Effect of SSRI exposure on the proliferation rate and glucose uptake in breast and ovary cancer cell lines

Breast cancer is the most prevalent malignancy amongst women worldwide while ovarian cancer represents the leading cause of death among gynecological malignancies. Women suffering from these cancers displayed heightened rates of major depressive disorder, and antidepressant treatment with selective serotonin reuptake inhibitors (SSRIs) is frequently recommended. Recently, narrative reviews and meta-analyses showed increased recurrence risks and mortality rates in SSRI-treated women with breast and ovarian cancer. We therefore examined whether three commonly prescribed SSRIs, fluoxetine, sertraline and citalopram, affect proliferation or glucose uptake of human breast and ovarian cancer cell lines characterized by different malignancies and metastatic potential. SSRI treatment or serotonin stimulation with therapeutically relevant concentrations over various time periods revealed no consistent dose- or time-dependent effect on proliferation rates. A marginal, but significant increase in glucose uptake was observed in SK-OV-3 ovarian cancer cells upon fluoxetine or sertraline, but not citalopram treatment. In three breast cancer cell lines and in two additional ovarian cancer cell lines no significant effect of SSRIs on glucose uptake was observed. Our data suggest that the observed increase in recurrence- and mortality rates in SSRI-treated cancer patients is unlikely to be linked to antidepressant therapies.

Dermal fibroblasts and triple-negative mammary epithelial cancer cells differentially stiffen their local matrix

The bulk measurement of extracellular matrix (ECM) stiffness is commonly used in mechanobiology. However, past studies by our group show that peri-cellular stiffness is quite heterogeneous and divergent from the bulk. We use optical tweezers active microrheology (AMR) to quantify how two phenotypically distinct migratory cell lines establish dissimilar patterns of peri-cellular stiffness. Dermal fibroblasts (DFs) and triple-negative human breast cancer cells MDA-MB-231 (MDAs) were embedded within type 1 collagen (T1C) hydrogels polymerized at two concentrations: 1.0 mg/ml and 1.5 mg/ml. We found DFs increase the local stiffness of 1.0 mg/ml T1C hydrogels but, surprisingly, do not alter the stiffness of 1.5 mg/ml T1C hydrogels. In contrast, MDAs predominantly do not stiffen T1C hydrogels as compared to cell-free controls. The results suggest that MDAs adapt to the bulk ECM stiffness, while DFs regulate local stiffness to levels they intrinsically prefer. In other experiments, cells were treated with transforming growth factor-β1 (TGF-β1), glucose, or ROCK inhibitor Y27632, which have known effects on DFs and MDAs related to migration, proliferation, and contractility. The results show that TGF-β1 alters stiffness anisotropy, while glucose increases stiffness magnitude around DFs but not MDAs and Y27632 treatment inhibits cell-mediated stiffening. Both cell lines exhibit an elongated morphology and local stiffness anisotropy, where the stiffer axis depends on the cell line, T1C concentration, and treatment. In summary, our findings demonstrate that AMR reveals otherwise masked mechanical properties such as spatial gradients and anisotropy, which are known to affect cell behavior at the macro-scale. The same properties manifest with similar magnitude around single cells.

Glucose Concentration in Cell Culture Medium Influences the BRCA1-Mediated Regulation of the Lipogenic Action of IGF-I in Breast Cancer Cells

Hyperglycaemia is a common metabolic alteration associated with breast cancer risk and progression. We have previously reported that BRCA1 restrains metabolic activity and proliferative response to IGF-I anabolic actions in breast cancer cells cultured in high glucose. Here, we evaluated the impact of normal physiological glucose on these tumour suppressive roles of BRCA1. Human breast cancer cells cultured in normal physiological and high glucose were treated with IGF-I (0-500 ng/mL). Cellular responses were evaluated using immunoblotting, co-immunoprecipitation, and cell viability assay. As we previously reported, IGF-I induced ACCA dephosphorylation by reducing the association between BRCA1 and phosphorylated ACCA in high glucose, and upregulated FASN abundance downstream of ACCA. However, these effects were not observed in normal glucose. Normal physiological glucose conditions completely blocked IGF-I-induced ACCA dephosphorylation and FASN upregulation. Co-immunoprecipitation studies showed that normal physiological glucose blocked ACCA dephosphorylation by increasing the association between BRCA1 and phosphorylated ACCA. Compared to high glucose, the proliferative response of breast cancer cells to IGF-I was reduced in normal glucose, whereas no difference was observed in normal mammary epithelial cells. Considering these results collectively, we conclude that normal physiological glucose promotes the novel function of BRCA1 as a metabolic restraint of IGF-I actions. These data suggest that maintaining normal glucose levels may improve BRCA1 function in breast cancer and slow down cancer progression.

Cannabinoid Combination Induces Cytoplasmic Vacuolation in MCF-7 Breast Cancer Cells

This study evaluated the synergistic anti-cancer potential of cannabinoid combinations across the MDA-MB-231 and MCF-7 human breast cancer cell lines. Cannabinoids were combined and their synergistic interactions were evaluated using median effect analysis. The most promising cannabinoid combination (C6) consisted of tetrahydrocannabinol, cannabigerol (CBG), cannabinol (CBN), and cannabidiol (CBD), and displayed favorable dose reduction indices and limited cytotoxicity against the non-cancerous breast cell line, MCF-10A. C6 exerted its effects in the MCF-7 cell line by inducing cell cycle arrest in the G₂ phase, followed by the induction of apoptosis. Morphological observations indicated the induction of cytoplasmic vacuolation, with further investigation suggesting that the vacuole membrane was derived from the endoplasmic reticulum. In addition, lipid accumulation, increased lysosome size, and significant increases in the endoplasmic reticulum chaperone protein glucose-regulated protein 78 (GRP78) expression were also observed. The selectivity and ability of cannabinoids to halt cancer cell proliferation via pathways resembling apoptosis, autophagy, and paraptosis shows promise for cannabinoid use in standardized breast cancer treatment.

NF-κB and STAT3 co-operation enhances high glucose induced aggressiveness of cholangiocarcinoma cells

AIMS

The present report aimed to investigate the underlying genes and pathways of high glucose driving cholangiocarcinoma (CCA) aggressiveness.

MAIN METHODS

We screened and compared the gene expression profiles obtained by RNA sequencing, of CCA cells cultured in high and normal glucose. Results from the transcriptomic analysis were confirmed in additional cell lines using in vitro migration-invasion assay, Western blotting and immunocytofluorescence.

KEY FINDINGS

Data indicated that high glucose increased the expression of interleukin-1β (IL-1β), an upstream regulator of nuclear factor-κB (NF-κB) pathway, through the nuclear localization of NF-κB. High glucose-induced NF-κB increased the migration and invasion of CCA cells and the expression of downstream NF-κB targeted genes associated with aggressiveness, including interleukin-6, a potent triggering signal of the signal transducer and activator of transcription 3 (STAT3) pathway. Such effects were reversed by inhibiting NF-κB nuclear translocation which additionally reduced the phosphorylation of STAT3 at Y705.

SIGNIFICANCE

These results indicate that NF-κB is activated by high glucose and they suggest that NF-κB interaction with STAT3 enhances CCA aggressiveness. Therefore, targeting multiple pathways such as STAT3 and NF-κB might improve CCA treatment outcome especially in condition such as hyperglycemia.

SGLT2 inhibition slows tumor growth in mice by reversing hyperinsulinemia

Background

Obesity confers an increased risk and accelerates the progression of multiple tumor types in rodents and humans, including both breast and colon cancer. Because sustained weight loss is rarely achieved, therapeutic approaches to slow or prevent obesity-associated cancer development have been limited, and mechanistic insights as to the obesity-cancer connection have been lacking.

Methods

E0771 breast tumors and MC38 colon tumors were treated in vivo in mice and in vitro with two mechanistically different insulin-lowering agents, a controlled-release mitochondrial protonophore (CRMP) and sodium-glucose cotransporter-2 (SGLT2) inhibitors, and tumor growth and glucose metabolism were assessed. Groups were compared by ANOVA with Bonferroni’s multiple comparisons test.

Results

Dapagliflozin slows tumor growth in two mouse models (E0771 breast cancer and MC38 colon adenocarcinoma) of obesity-associated cancers in vivo, and a mechanistically different insulin-lowering agent, CRMP, also slowed breast tumor growth through its effect to reverse hyperinsulinemia. In both models and with both agents, tumor glucose uptake and oxidation were not constitutively high, but were hormone-responsive. Restoration of hyperinsulinemia by subcutaneous insulin infusion abrogated the effects of both dapagliflozin and CRMP to slow tumor growth.

Conclusions

Taken together, these data demonstrate that hyperinsulinemia per se promotes both breast and colon cancer progression in obese mice, and highlight SGLT2 inhibitors as a clinically available means of slowing obesity-associated tumor growth due to their glucose- and insulin-lowering effects.

High-Glucose Conditions Promote Anchorage-Independent Colony Growth in Human Breast Cancer MCF-7 Cells

Previous studies have shown that hyperglycemia is connected to the malignant progression of breast cancer; however, the effects of hyperglycemia on tumorigenic potential in breast cancer cells are largely unknown. Here, we demonstrated that the ability of the human breast cancer cell line MCF-7 to undertake anchorage-independent colony growth was significantly enhanced when cultured under high-glucose conditions compared with that under physiological glucose conditions. The high-glucose conditions also promoted phosphorylation of Akt, suggesting that MCF-7 cells cultured in these conditions acquired an increased ability to undergo anchorage-independent growth at least in part through Akt activation, which has been linked to the development of breast cancer. These results raise the possibility that regulation of Akt activity contributes to the tumorigenesis of breast cancer under high-glucose conditions, and we propose that additional analyses of high glucose-induced tumor formation would provide novel strategies for the diagnosis and therapy of breast cancer with hyperglycemia.

The activation of lactate dehydrogenase induced by mTOR drives neoplastic change in breast epithelial cells

mTOR kinase and the A isoform of lactate dehydrogenase (LDH-A) are key players controlling the metabolic characteristics of cancer cells. By using cultured human breast cells as a “metabolic tumor” model, we attempted to explore the correlation between these two factors. “Metabolic tumors” are defined as neoplastic conditions frequently associated with features of the metabolic syndrome, such as hyper-insulinemia and hyper-glycemia. MCF-7 cells (a well differentiated carcinoma) and MCF-10A cells (a widely used model for studying normal breast cell transformation) were used in this study. These cells were exposed to known factors triggering mTOR activation. In both treated cultures, we evaluated the link between mTOR kinase activity and the level of LDH expression / function. Furthermore, we elaborated the metabolic changes produced in cells by the mTOR-directed LDH-A up-regulation. Interestingly, we observed that in the non-neoplastic MCF-10A culture, mTOR-directed up-regulation of LDH-A was followed by a reprogramming of cell metabolism, which showed an increased dependence on glycolysis rather than on oxidative reactions. As a consequence, lactate production appeared to be enhanced and cells began to display increased self-renewal and clonogenic power: signals suggestive of neoplastic change. Enhanced clonogenicity of cells was abolished by rapamycin treatment, and furthermore heavily reduced by LDH enzymatic inhibition. These results highlighted a mechanistic link between metabolic alterations and tumorigenesis, whereby suggesting LDH inhibition as a possible chemo-preventive measure to target the metabolic alterations driving neoplastic change.

Gold nanoparticles-induced cytotoxicity in triple negative breast cancer involves different epigenetic alterations depending upon the surface charge

Gold nanoparticles (AuNPs) are used enormously in different cancers but very little is known regarding their molecular mechanism and surface charge role in the process of cell death. Here, we elucidate the molecular mechanism by which differentially charged AuNPs induce cytotoxicity in triple negative breast cancer (TNBC) cells. Cytotoxicity assay revealed that both negatively charged (citrate-capped) and positively charged (cysteamine-capped) AuNPs induced cell-death in a dose-dependent manner. We provide first evidence that AuNPs-induced oxidative stress alters Wnt signalling pathway in MDA-MB-231 and MDA-MB-468 cells. Although both differentially charged AuNPs induced cell death, the rate and mechanism involved in the process of cell death were different. Negatively charged AuNPs increased the expression of MKP-1, dephosphorylated and deacetylated histone H3 at Ser10 and K9/K14 residues respectively whereas, positively charged AuNPs decreased the expression of MKP-1, phosphorylated and acetylated histone H3 at Ser 10 and K9/K14 residues respectively. High-resolution transmission electron microscopy (HRTEM) studies revealed that AuNPs were localised in cytoplasm and mitochondria of MDA-MB-231 cells. Interestingly, AuNPs treatment makes MDA-MB-231 cells sensitive to 5-fluorouracil (5-FU) by decreasing the expression of thymidylate synthetase enzyme. This study highlights the role of surface charge (independent of size) in the mechanisms of toxicity and cell death.

Biological impact of advanced glycation endproducts on estrogen receptor-positive MCF-7 breast cancer cells

Diabetes mellitus potentiates the risk of breast cancer. We have previously described the pro-tumorigenic effects of advanced glycation endproducts (AGEs) on estrogen receptor (ER)-negative MDA-MB-231 breast cancer cell line mediated through the receptor for AGEs (RAGE). However, a predominant association between women with ER-positive breast cancer and type 2 diabetes mellitus has been reported. Therefore, we have investigated the biological impact of AGEs on ER-positive human breast cancer cell line MCF-7 using in vitro cell-based assays including cell count, migration, and invasion assays. Western blot, FACS analyses and quantitative real time-PCR were also performed. We found that AGEs at 50-100μg/mL increased MCF-7 cell proliferation and cell migration associated with an enhancement of pro-matrix metalloproteinase (MMP)-9 activity, without affecting their poor invasiveness. However, 200μg/mL AGEs inhibited MCF-7 cell proliferation through induction of apoptosis indicated by caspase-3 cleavage detected using Western blotting. A phospho-protein array analysis revealed that AGEs mainly induce the phosphorylation of extracellular-signal regulated kinase (ERK)1/2 and cAMP response element binding protein-1 (CREB1), both signaling molecules considered as key regulators of AGEs pro-tumorigenic effects. We also showed that AGEs up-regulate RAGE and ER expression at the protein and transcript levels in MCF-7 cells, in a RAGE-dependent manner after blockade of AGEs/RAGE interaction using neutralizing anti-RAGE antibody. Throughout the study, BSA had no effect on cellular processes. These findings pave the way for future studies investigating whether the exposure of AGEs-treated ER-positive breast cancer cells to estrogen could lead to a potentiation of breast cancer development and progression.

Mutant p53 potentiates the oncogenic effects of insulin by inhibiting the tumor suppressor DAB2IP

Obesity and type 2 diabetes are significant risk factors for malignancies, being associated with chronic inflammation and hyperinsulinemia. In this context, insulin can synergize with inflammation to promote proliferation, survival, and dissemination of cancer cells. Point mutation of p53 is a frequent event and a significant factor in cancer development and progression. Mutant p53 protein(s) (mutp53) can acquire oncogenic properties that increase metastasis, proliferation, and cell survival. We report that breast and prostate cancer cells with mutant p53 respond to insulin stimulation by increasing cell proliferation and invasivity, and that such a response depends on the presence of mutp53. Mechanistically, we find that mutp53 augments insulin-induced AKT1 activation by binding and inhibiting the tumor suppressor DAB2IP (DAB2-interacting protein) in the cytoplasm. This molecular axis reveals a specific gain of function for mutant p53 in the response to insulin stimulation, offering an additional perspective to understand the relationship between hyperinsulinemia and cancer evolution.

High glucose and insulin enhance uPA expression, ROS formation and invasiveness in breast cancer-derived cells

BACKGROUND

Accumulating evidence indicates that type 2 diabetes is associated with an increased risk to develop breast cancer. This risk has been attributed to hyperglycemia, hyperinsulinemia and chronic inflammation. As yet, however, the mechanisms underlying this association are poorly understood. Here, we studied the effect of high glucose and insulin on breast cancer-derived cell proliferation, migration, epithelial-mesenchymal transition (EMT) and invasiveness, as well as its relationship to reactive oxygen species (ROS) production and the plasminogen activation system.

METHODS

MDA-MB-231 cell proliferation, migration and invasion were assessed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), scratch-wound and matrigel transwell assays, respectively. ROS production was determined using 2' 7'-dichlorodihydrofluorescein diacetate. The expression of E-cadherin, vimentin, fibronectin, urokinase plasminogen activator (uPA), its receptor (uPAR) and its inhibitor (PAI-1) were assessed using qRT-PCR and/or Western blotting assays, respectively. uPA activity was determined using gel zymography.

RESULTS

We found that high glucose stimulated MDA-MB-231 cell proliferation, migration and invasion, together with an increased expression of mesenchymal markers (i.e., vimentin and fibronectin). These effects were further enhanced by the simultaneous administration of insulin. In both cases, the invasion and growth responses were found to be associated with an increased expression of uPA, uPAR and PAI-1, as well as an increase in active uPA. An osmolality effect of high glucose was excluded by using mannitol at an equimolar concentration. We also found that all changes induced by high glucose and insulin were attenuated by the anti-oxidant N-acetylcysteine (NAC) and, thus, depended on ROS production.

CONCLUSIONS

From our data we conclude that hyperglycemia and hyperinsulinemia can promote breast cancer cell proliferation, migration and invasion. We found that these features were associated with increased expression of the mesenchymal markers vimentin and fibronectin, as well as increased uPA expression and activation through a mechanism mediated by ROS.

High glucose enhances progression of cholangiocarcinoma cells via STAT3 activation

Epidemiological studies have indicated diabetes mellitus (DM) as a risk of cholangiocarcinoma (CCA), however, the effects and mechanisms of high glucose on progression of CCA remain unclear. This study reports for the first time of the enhancing effects of high glucose on aggressive phenotypes of CCA cells via STAT3 activation. CCA cells cultured in high glucose media exerted significantly higher rates of cell proliferation, adhesion, migration and invasion than those cultured in normal glucose. The phosphokinase array revealed STAT3 as the dominant signal activated in response to high glucose. Increased nuclear STAT3, p-STAT3 and its downstream target proteins, cyclin D1, vimentin and MMP2, were shown to be underling mechanisms of high glucose stimulation. The link of high glucose and STAT3 activation was confirmed in tumor tissues from CCA patients with DM that exhibited higher STAT3 activation than those without DM. Moreover, the levels of STAT3 activation were correlated with the levels of blood glucose. Finally, decreasing the level of glucose or using a STAT3 inhibitor could reduce the effects of high glucose. These findings suggest that controlling blood glucose or using a STAT3 inhibitor as an alternative approach may improve the therapeutic outcome of CCA patients with DM.

The anti-proliferative effect of metformin in triple-negative MDA-MB-231 breast cancer cells is highly dependent on glucose concentration: implications for cancer therapy and prevention

BACKGROUND

Metformin has been shown to have a strong anti-proliferative effect in many breast cancer cell lines, mainly due to the activation of the energy sensing kinase, AMP-activated protein kinase (AMPK). MDA-MB-231 cells are aggressive and invasive breast cancer cells that are known to be resistant to several anti-cancer agents as well as to the anti-proliferative effect of metformin. As metformin is a glucose lowering drug, we hypothesized that normoglycemia will sensitize MDA-MB-231 cells to the anti-proliferative effect of metformin.

METHODS

MDA-MB-231 cells were treated with increasing metformin concentrations in hyperglycemic or normoglycemic conditions. The growth inhibitory effect of metformin was assessed by MTT assay. The expression of several proteins involved in cell proliferation was measured by Western blotting.

RESULTS

In agreement with previous studies, treatment with metformin did not inhibit the growth of MDA-MB-231 cells cultured in hyperglycemic conditions. However, metformin significantly inhibited MDA-MB-231 growth when the cells were cultured in normoglycemic conditions. In addition, we show that metformin-treatment of MDA-MB-231 cells cultured in normoglycemic conditions and not in hyperglycemic conditions caused a striking activation of AMPK, and an AMPK-dependent inhibition of multiple molecular signaling pathways known to control protein synthesis and cell proliferation.

CONCLUSION

Our data show that normoglycemia sensitizes the triple negative MDA-MB-231 breast cancer cells to the anti-proliferative effect of metformin through an AMPK-dependent mechanism.

GENERAL SIGNIFICANCE

These findings suggest that tight normoglycemic control may enhance the anti-proliferative effect of metformin in diabetic cancer patients.