The Pentose Phosphate Pathway Dynamics in Cancer and Its Dependency on Intracellular pH.

The Pentose Phosphate Pathway (PPP) is one of the key metabolic pathways occurring in living cells to produce energy and maintain cellular homeostasis. Cancer cells have higher cytoplasmic utilization of glucose (glycolysis), even in the presence of oxygen; this is known as the "Warburg Effect". However, cytoplasmic glucose utilization can also occur in cancer through the PPP. This pathway contributes to cancer cells by operating in many different ways: (i) as a defense mechanism via the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) to prevent apoptosis, (ii) as a provision for the maintenance of energy by intermediate glycolysis, (iii) by increasing genomic material to the cellular pool of nucleic acid bases, (iv) by promoting survival through increasing glycolysis, and so increasing acid production, and (v) by inducing cellular proliferation by the synthesis of nucleic acid, fatty acid, and amino acid. Each step of the PPP can be upregulated in some types of cancer but not in others. An interesting aspect of this metabolic pathway is the shared regulation of the glycolytic and PPP pathways by intracellular pH (pHi). Indeed, as with glycolysis, the optimum activity of the enzymes driving the PPP occurs at an alkaline pHi, which is compatible with the cytoplasmic pH of cancer cells. Here, we outline each step of the PPP and discuss its possible correlation with cancer.

The Interplay of Dysregulated pH and Electrolyte Imbalance in Cancer.

Cancer cells and tissues have an aberrant regulation of hydrogen ion dynamics driven by a combination of poor vascular perfusion, regional hypoxia, and increased the flux of carbons through fermentative glycolysis. This leads to extracellular acidosis and intracellular alkalinization. Dysregulated pH dynamics influence cancer cell biology, from cell transformation and tumorigenesis to proliferation, local growth, invasion, and metastasis. Moreover, this dysregulated intracellular pH (pHi) drives a metabolic shift to increased aerobic glycolysis and reduced mitochondrial oxidative phosphorylation, referred to as the Warburg effect, or Warburg metabolism, which is a selective feature of cancer. This metabolic reprogramming confers a thermodynamic advantage on cancer cells and tissues by protecting them against oxidative stress, enhancing their resistance to hypoxia, and allowing a rapid conversion of nutrients into biomass to enable cell proliferation. Indeed, most cancers have increased glucose uptake and lactic acid production. Furthermore, cancer cells have very dysregulated electrolyte balances, and in the interaction of the pH dynamics with electrolyte, dynamics is less well known. In this review, we highlight the interconnected roles of dysregulated pH dynamics and electrolytes imbalance in cancer initiation, progression, adaptation, and in determining the programming and reprogramming of tumor cell metabolism.

Mitochondrial Toxicity of Azithromycin Results in Aerobic Glycolysis and DNA Damage of Human Mammary Epithelia and Fibroblasts.

Mitochondria evolved from free-living bacteria via endocytosis within eukaryotic host cells millions of year ago. We hypothesized that antibiotics cause mammalian mitochondrial damage while causing bacterial lethality. Mitochondrial toxicity of azithromycin in human mammary epithelia MCF-12A and fibroblasts were tested by fluorescent and transmission electron microscopy. Gene expression and DNA damage were tested by real-time polymerase chain reaction (qPCR) and ELISA. We found azithromycin suppressed the mitochondrial membrane potential gradient of MCF-12A cells and fibroblasts. Ultrastructure exams showed that the antibiotic caused vacuolated and swollen mitochondria with disrupted cristae in MCF-12A cells and fibroblasts compared to the morphology of mitochondria in the cells without antibiotic treatment. Fluorescent microscopy also showed azithromycin-induced mitochondrial reactive oxygen species (ROS), superoxide, after 3 h of culture. The DNA oxidative damage product, 8-hydroxy-2'-deoxyguanosine (8-OHdG, significantly increased in the media after MCF-12A cells and fibroblasts were cultured in the media containing azithromycin for 24 h. Azithromycin upregulated gene expression of hypoxia inducible factor 1 alpha (HIF1a), glycolytic enzymes including hexokinase 2 (HK2), phosphofructokinase 1 (PFKM), pyruvate kinase muscle isozyme M2 (PKM2), and glucose transporters in MCF-12A cells and fibroblasts. Lactate production also increased in the culture media. After treatment with azithromycin, healthy MCF-12A and fibroblast cells increased aerobic glycolysis-the "Warburg Effect"-to generate energy. In summary, azithromycin caused mitochondrial toxicity, ROS overproduction, DNA oxidative damage, upregulation of the HIF1a gene, and aerobic glycolysis in healthy mammalian cells. Over-usage of antibiotics could contribute to tumorigenesis and neurodegeneration and aggravate existing mitochondria-associated diseases.

The Role of Sodium Hydrogen Exchanger 1 in Dysregulation of Proton Dynamics and Reprogramming of Cancer Metabolism as a Sequela

Cancer cells have an unusual regulation of hydrogen ion dynamics that are driven by poor vascularity perfusion, regional hypoxia, and increased glycolysis. All these forces synergize/orchestrate together to create extracellular acidity and intracellular alkalinity. Precisely, they lead to extracellular pH (pHe) values as low as 6.2 and intracellular pH values as high as 8. This unique pH gradient (∆pHi to ∆pHe) across the cell membrane increases as the tumor progresses, and is markedly displaced from the electrochemical equilibrium of protons. These unusual pH dynamics influence cancer cell biology, including proliferation, metastasis, and metabolic adaptation. Warburg metabolism with increased glycolysis, even in the presence of Oxygen with the subsequent reduction in Krebs' cycle, is a common feature of most cancers. This metabolic reprogramming confers evolutionary advantages to cancer cells by enhancing their resistance to hypoxia, to chemotherapy or radiotherapy, allowing rapid production of biological building blocks that support cellular proliferation, and shielding against damaging mitochondrial free radicals. In this article, we highlight the interconnected roles of dysregulated pH dynamics in cancer initiation, progression, adaptation, and in determining the programming and re-programming of tumor cell metabolism.

The adverse effect of gentamicin on cell metabolism in three cultured mammary cell lines: "Are cell culture data skewed?"

Many cells are cultured in media that contains an antibiotic to prevent bacterial contamination. Mycoplasma and other bacterial contamination is a serious problem for those involved in cell culture. Antibiotics in the media helps prevent this contamination and make life easier for the investigators; as performing cell culture experiments in antibiotic free media is difficult and requires vigorous sterile technique. There are many reports of antibiotics causing mitochondrial damage. In this study, we tested the effect of gentamicin in culture media on human mammary epithelial MCF-12A and breast cancer MCF-7 and MDA-MB-231 cell lines by real time PCR, immunofluorescent microscopy, lactate assay, DNA damage assay. We found that the addition of gentamicin in media upregulated the gene expression of hypoxia inducer factor 1 alpha (HIF1a), glycolytic enzymes and glucose transporters, compared to the cells cultured in gentamicin free media. Gentamicin also increased the lactate production and inhibited mitochondrial membrane potential of the cell lines. Furthermore, the antibiotics in media induced mitochondrial reactive oxygen species causing DNA damage. We found an increase of 8-hydroxy-2'-deoxyguanosine a product of DNA oxidative damage in the media of MCF-12A, MCF-7 and MDA-MB-231 cell lines. These results showed that normal epithelial and breast cancer cells cultured in the media with gentamicin had increased HIF1a, aerobic glycolysis and DNA oxidative damage. If we use these unhealthy cells in the experiment, all data will be different, compared to cells grown in gentamicin free media. We have studied the detrimental effects of three antibiotics on mitochondrial function in the untransformed MCF-12A human mammary cell line and two human mammary cancer cell lines, MCF-7 and MB-MDA-231. The metabolic changes in all cell lines were dramatically different between those in antibiotic free media versus antibiotic containing media. There was a marked difference in gene expression of glycolytic enzymes, reactive oxygen species production and effects on membrane potential. Ironically, our first studies were done in media containing gentamicin, and repeated studies were done in gentamicin free media. The results were very different. The purpose of this report is to emphasize that metabolic cell culture data may be inaccurate because experiments were performed in cell culture media containing antibiotics. We will present evidence to support this theory.

Decreased Iron in Cancer Cells and Their Microenvironment Improves Cytolysis of Breast Cancer Cells by Natural Killer Cells.

The association of iron with anticancer immunity is unclear. In order to determine the role of iron in anticancer immunity, we manipulated intracellular iron levels of the human MCF-7 and MDA-MB-231 breast cancer cell lines, and measured cytolysis of breast cancer cells by the natural killer cell line NK-92MI, nitric oxide (NO) production, tumor necrosis factor alpha (TNFα) production and gene expression of ferritin heavy chain (FTH1). We found that NK-92MI increased synthesis and release of NO and TNFα into the medium during co-culturing of NK-92MI cells with MCF-7 or MDA-MB-231 cells. Addition of iron inhibited the cytolysis of the breast cancer cell lines. The iron chelator deferoxamine (DFOM) increased NK-92MI cytolysis to MCF-7 or MDA-MB-231 cells. Iron reversed cytotoxicity to breast cancer cells induced by NO, released from S-nitroso-N-acetyl-penicillamine (NO donor). Real time quantitative polymerase chain reaction showed that iron up-regulated the expression of FTH1 and iron chelator DFOM reduced FTH1 expression of MCF-7 and MDA-MB-231 cells. In conclusion, increased iron in cancer cells and their microenvironment protects cancer cells from natural killer cell cytolysis by antagonizing NO- and TNFα-associated cytotoxicity and by up-regulation of ferritin expression in breast cancer cells. Conversely, a decrease in iron concentration caused by DFOM improves natural killer cytolysis of tumor cells.

Exogenous normal mammary epithelial mitochondria suppress glycolytic metabolism and glucose uptake of human breast cancer cells.

We hypothesized that normal mitochondria inhibited cancer cell proliferation and increased drug sensitivity by the mechanism of suppression of cancer aerobic glycolysis. To demonstrate the mechanism, we used real-time PCR and glycolysis cell-based assay to measure gene expression of glycolytic enzymes and glucose transporters, and extracellular lactate production of human breast cancer cells. We found that isolated fluorescent probe-stained mitochondria of MCF-12A (human mammary epithelia) could enter into human breast cancer cell lines MCF-7, T47D, and MDA-MB-231, confirmed by fluorescent and confocal microscopy. Mitochondria from the untransformed human mammary epithelia increased drug sensitivity of MCF-7 cells to paclitaxel. Real-time PCR showed that exogenous normal mitochondria of MCF-12A suppressed gene expression of glycolytic enzymes, lactate dehydrogenase A, and glucose transporter 1 and 3 of MCF-7 and MDA-MB-231 cells. Glycolysis cell-based assay revealed that normal mitochondria significantly suppressed lactate production in culture media of MCF-7, T47D, and MDA-MB-231 cells. In conclusion, normal mitochondria suppress cancer proliferation and increase drug sensitivity by the mechanism of inhibition of cancer cell glycolysis and glucose uptake.

Adjuvant breast cancer vaccine improves disease specific survival of breast cancer patients with depressed lymphocyte immunity.

PURPOSE: Beginning in 1995 breast cancer patients were vaccinated in the adjuvant setting with an autologous, allogeneic whole cell vaccine to evaluate the effect on host lymphocyte immunity and disease specific survival. METHODS: The breast cancer patients had host lymphocyte immunity against tumor associated antigens evaluated by a Lymphocyte Blastogenesis Assay (LBA) before vaccination. Thirty-seven patients with depressed immunity were vaccinated in the adjuvant setting. Patients were given six intradermal injections (three weekly followed by three monthly). Ten weeks after the last injection the LBA was repeated. RESULTS: Some patients experienced slight pain and swelling at the injection site with slight chills and fever, but there were no severe toxicities. The vaccinated patients had a mean follow-up of 12.7 years with mean follow-up of 8.9 and 9.2 years for the patients with normal and depressed immunity, respectively, in the historic control. The 10 year survival was 95% (20 of 21 patients) in the normal immunity historic control, 59% (33 of 56 patients) in the depressed immunity historic control and 89% (33 of 37 patients) in the patients with depressed immunity that were vaccinated in the present clinical trial. The disease specific survival of the vaccinated patients with depressed immunity in this trial is significantly greater than that of the historic controls of unvaccinated patients with depressed immunity to their tumor associated antigens. CONCLUSION: This study confirms the importance of maintaining good host lymphocyte immunity after completion of standard therapy and validates the value of cancer immunotherapy in the adjuvant setting.

Progranulin (GP88) tumor tissue expression is associated with increased risk of recurrence in breast cancer patients diagnosed with estrogen receptor positive invasive ductal carcinoma.

INTRODUCTION: GP88 (progranulin) has been implicated in tumorigenesis and resistance to anti-estrogen therapies for estrogen receptor positive (ER+) breast cancer. Previous pathological studies showed that GP88 is expressed in invasive ductal carcinoma (IDC), but not in normal mammary epithelial tissue, benign lesions or lobular carcinoma. Based on these results, the present study examines GP88 prognostic significance in association with recurrence and death risks for ER+ IDC patients. METHODS: Two retrospective multi-site clinical studies examined GP88 expression by immunohistochemistry (IHC) analysis of paraffin-embedded breast tumor tissue sections from ER+ IDC patients (lymph node positive and negative, stage 1 to 3) in correlation with patients' survival outcomes. The training study established a GP88 cut-off value associated with decreased disease-free (DFS) and overall (OS) survivals. The validation study verified the GP88 cut-off value and compared GP88 prognostic information with other prognostic factors, particularly tumor size, grade, disease stage and lymph node status in multivariate analysis. RESULTS: GP88 expression is associated with a statistically significant increase in recurrence risk for ER+ IDC patients. The training study established that GP88 3+ score was associated with decreased DFS (P = 0.0004) and OS (P = 0.0036). The independent validation study verified that GP88 3+ score was associated with a 5.9-fold higher hazard of disease recurrence and a 2.5-fold higher mortality hazard compared to patients with tumor GP88 < 3+. GP88 remained an independent risk predictor after considering age, ethnicity, nodal status, tumor size, tumor grade, disease stage, progesterone receptor expression and treatments. CONCLUSIONS: The survival factor GP88 is a novel prognostic biomarker, predictive of recurrence risk and increased mortality for non-metastatic ER+ IDC patients. Of importance, our data show that GP88 continues to be a prognostic factor even after five years. These results also provide evidence that GP88 provides prognostic information independent of tumor and clinical characteristics and would support prospective study to examine whether GP88 expression could help stratify patients with ER+ tumors for adjuvant therapy.

Down-regulation of expression of interleukin-6 and its receptor results in growth inhibition of MCF-7 breast cancer cells.

Interleukin-6 (IL-6) plays an important role in the neoplastic process through its action on cancer cell adhesion, motility, proliferation, tumor-specific antigen expression, and thrombopoiesis. IL-6 exerts its activity by binding to a high affinity receptor complex consisting of two membrane glycoproteins: the 80 kDa IL-6 a-receptor subunit (IL-6R) and the 130 kDa signal-transducing protein (GP130). In the present study, MCF-7 breast cancer cells were cultured with human IL-6 and IL-6 soluble receptor (sIL-6R). MCF-7 cells were also treated with either antibodies specific to human IL-6 and IL-6R, or synthetic antisense oligodeoxynucleotides (ODNs) targeted to IL-6 and IL-6R genes. Cell growth was measured, and it was found that human IL-6 and sIL-6R did not significantly increase the proliferation of MCF-7 cells. When IL-6 produced by the MCF-7 cells was bound by rabbit anti-human IL-6 antibody, there was a significant dose-dependent inhibition of cell proliferation. IL-6 and IL-6R antisense ODNs caused a marked and specific decrease in IL-6 and IL-6R mRNA and proteins, respectively. Both IL-6 and IL-6R antisense ODNs significantly inhibited the proliferation of MCF-7 cells, but the inhibitory effect of IL-6R antisense ODN was greater than that of IL-6 antisense ODN (IC50: IL-6R: 1 µM; IL-6: 5 µM, 72-hour incubation). Addition of exogenous IL-6 partially reversed the growth inhibition caused by IL-6 antisense ODN but not the growth inhibition caused by IL-6R antisense ODN. In conclusion, IL-6 plays an important role in maintaining the growth of MCF-7 breast cancer cells. These results suggest careful modulation of IL-6 and IL-6R expression of cells as a potential approach for breast cancer therapy.

Human leukocyte antigen G expression in breast cancer: role in immunosuppression.

Human leukocyte antigen G (HLA-G) is an immunotolerant nonclassical major histocompatibility complex Class Ib molecule. It is expressed by trophoblastic placental cells during pregnancy to protect the fetus from maternal alloreactivity. HLA-G is overexpressed in tumors and involved in cancer immune evasion. Reverse transcription-polymerase chain reaction and immunohistochemistry (IHC) were used to examine HLA-G expression in normal mammary and breast cancer cell lines and normal and human breast cancer tissues. Reverse transcription-polymerase chain reaction confirmed that normal epithelial MCF-12A cells had no HLA-G mRNA expression, whereas cancer cell lines MCF-7, T47D, and MDA-MB-231 and NCI/Adr-Res had various levels of HLA-G mRNA expression. Twelve (12) normal and 38 breast cancer tissues were examined by IHC. Fifty-eight (58) percent (22/38) of cancers had medium to strong staining to HLA-G, whereas only 8% (1/12) of normal breast tissues had medium to strong staining, and the difference was significant (p < 0.05). HLA-G staining was found in the membranes and cytoplasm of cancer cells. In conclusion, breast cancer cells overexpress HLA-G mRNA and protein, and this probably contributes to immune evasion.

Manipulation of iron transporter genes results in the suppression of human and mouse mammary adenocarcinomas.

Since malignant cells often have a high demand for iron, we hypothesize that breast cancer cells may alter the expression of iron transporter genes including iron importers [transferrin receptor (TFRC) and solute carrier family 11 (proton-coupled divalent metal ion transporters), member 2 (SLC11A2)] and the iron exporter SLC40A1 (ferroportin), and additionally that the growth of breast cancer can be inhibited by manipulating iron transporter gene expression. To test our hypothesis, reverse transcription polymerase chain reaction (RT-PCR) was used to determine mRNA expression of iron transporter genes in normal human mammary epithelial MCF-12A cells and human breast cancer MCF-7 cells. Antisense oligonucleotides were employed to suppress the expression of TFRC gene in the 4T1 mammary adenocarcinoma in both cell culture and a mouse tumor model. We found the following: i) the MCF-7 cells have higher expression of TFRC and SLC11A2 compared with MCF-12A epithelia; ii) SLC40A1 was only expressed in MCF-12A epithelia but not in MCF-7 cells; iii) iron increased mRNA levels of the SLC11A2 gene in both MCF-12A and MCF-7 cells; iv) TFRC antisense oligonucleotides reduced TFRC mRNA levels and intracellular total iron, and inhibited the proliferation of the 4T1 cells in cell culture; v) TFRC antisense oligonucleotide inhibited tumor growth and lung metastases in the 4T1 mammary adenocarcinoma mouse model. In conclusion, breast cancer cells up-regulate the expression of iron importer genes and down-regulate the expression of iron exporter SLC40A1 to satisfy their increased demand for iron. Suppression of transferrin receptor by antisense results in inhibition of tumor growth and lung metastasis in the 4T1 mammary adenocarcinoma mouse model.

Stereotactic radiofrequency ablation: a minimally invasive technique for nonpalpable breast cancer in postmenopausal patients.

BACKGROUND: The purpose of this study was to determine the feasibility of radiofrequency ablation (RFA) of nonpalpable breast cancer in postmenopausal women, and report on long-term follow-up with clinical examination and mammography. METHODS: Since November 2000, we have performed RFA on stereotactically localized nonpalpable breast cancers (only mammographic densities) in women older than 65 years with other serious health problems. RESULTS: The first patient had the procedure done in the office with sedation and local anesthesia. The radiofrequency probe was inserted by stereotactic localization, and the RFA proceeded for 20 min at 75 degrees C. Two weeks later, the lesion was not seen mammographically, but by palpation there was induration at the ablation site. Six weeks later, open excision of the area confirmed a prominent ablation site with no remaining viable tumor cells. The second patient had the same procedure, and has been followed without open biopsy. The third patient had DCIS and the probe arrays were not able to penetrate the lesion. The fourth and fifth patients had light sedation with an intercostal nerve block to eliminate discomfort and this approach was found to be a very effective office procedure. The last two patients' ablation sites were injected with depo-medrol and they were placed on anti-inflammatory therapy to decrease the palpable induration caused by fat necrosis. CONCLUSION: We found RFA feasible for definitive therapy for nonpalpable breast cancer. If our results are confirmed by larger clinical trials, RFA would eliminate open surgery and decrease the morbidity associated with lumpectomy and radiation.

Complete resolution of malignant ascites in stage IV breast cancer by peritoneal drainage and innovative chemoimmunotherapy: a case report.

Malignant ascites is a very serious and difficult to manage problem in the cancer patient. It is a sign of late stage disease and treatment is mainly palliative. Therefore the treatment should produce minimal discomfort and have few side effects. Numerous methods for managing the problem have been attempted, but few have afforded complete remission of the ascites with improved survival. We are reporting a case of complete remission of malignant ascites in a stage IV breast cancer patient. Her condition was managed by a peritoneal dialysis catheter and an aggressive intraperitoneal innovative chemoimmunotherapy protocol.

Radiofrequency ablation of a stereotactically localized nonpalpable breast carcinoma.

A nonpalpable breast lesion was detected in a 71-year-old woman who had returned for her annual mammogram. Stereotactic core needle biopsy revealed an infiltrating ductal carcinoma. The patient agreed to stereotactic localization and radiofrequency ablation of the lesion followed after 4 weeks by open surgical biopsy. The breast lesion was localized and the radiofrequency ablation performed under local anesthesia in the outpatient/office setting. The lesion was ablated for a total of 20 minutes at a sustained mean temperature of 75 degrees C. After a 30-second cooldown the peripheral temperature of the four peripheral thermocouples ranged from 58 degrees C to 70 degrees C. A surgical clip was placed at the site of the ablated lesion. The postprocedure course was uneventful and the patient proceeded to open biopsy 4 weeks later. The open biopsy specimen, a left segmental mastectomy, underwent specimen radiography, which confirmed the surgical clip in the center of the lesion. There was extensive central necrosis and hemorrhage surrounded by fat necrosis. There was no definite viable residual tumor and the margins were clear. This is the first case in a clinical protocol designed to determine the efficacy of stereotactic localization and radiofrequency ablation of nonpalpable breast lesions. Additional ablations will be required to define the procedure but the results from this initial patient suggest that this is a promising minimally invasive curative approach for nonpalpable breast lesions.

Gene targets of antisense therapies in breast cancer.

Advances in molecular and cell biology have led to further understanding of the mechanisms of malignant growth and metastasis in human breast cancer cells. Initiation and progression of breast cancer results from mutations and the abnormal expression of many genes that control cellular proliferation, differentiation, invasion, metastasis and sensitivity to therapy (chemotherapy and radiation therapy). Inhibition of host immunity also plays a role in breast cancer progression. Many genes have been selected as targets for antisense therapy, including HER-2/neu, PKA, TGF-alpha, EGFR, TGF-beta, IGFIR, P12, MDM2, BRCA, Bcl-2, ER, VEGF, MDR, ferritin, transferrin receptor, IRE, C-fos, HSP27, C-myc, C-raf and metallothionein genes. The strategy behind antisense therapy is the development of specific therapeutic agents that aim to correct the mutations and abnormal expression of cellular genes in breast tumour cells by decreasing gene expression, inducing degradation of target mRNA and causing premature termination of transcription. Many in vitro and in vivo studies have investigated the therapeutic efficacy of oligonucleotides and antisense RNAs. These studies have demonstrated specific inhibition of tumour cell growth by antisense therapy and have shown synergistic inhibitory effects between antisense oligonucleotides or antisense RNA and conventional chemotherapeutic drugs used in the treatment of breast cancer. Antisense oligonucleotides have been modified to improve their ability to penetrate cells, bind to gene sequences and downregulate target gene function. Many delivery systems for antisense RNA and antisense oligonucleotides have been developed, including virus vectors (retrovirus, adenovirus and adeno-associate virus) and liposomes, to carry the antisense RNA or oligonucleotides through the cell membrane into the cytoplasm and nucleus of the tumour cells. However, in order to determine their feasibility antisense therapies need to be further investigated to determine their antitumour activity, pharmacokinetics and toxicity in breast cancer patients.