The hypoxic core: a possible answer to the cancer paradox

Synthetic engineered bacteria for cancer therapy

INTRODUCTION

Cancer mortality worldwide highlights the urgency for advanced therapeutic methods to fill the gaps in conventional cancer therapies. Bacteriotherapy is showing great potential in tumor regression due to the motility and colonization tendencies of bacteria. However, the complicated in vivo environment and tumor pathogenesis hamper the therapeutic outcomes. Synthetic engineering methods endow bacteria with flexible abilities both at the extracellular and intracellular levels to meet treatment requirements. In this review, we introduce synthetic engineering methods for bacterial modifications. We highlight the recent progress in engineered bacteria and explore how these synthetic methods endow bacteria with superior abilities in cancer therapy. The current clinical translations are further discussed. Overall, this review may shed light on the advancement of engineered bacteria for cancer therapy.

AREAS COVERED

Recent progress in synthetic methods for bacterial engineering and specific examples of their applications in cancer therapy are discussed in this review.

EXPERT OPINION

Bacteriotherapy bridges the gaps of conventional cancer therapies through the natural motility and colonization tendency of bacteria, as well as their synthetic engineering. Nevertheless, to fulfill the bacteriotherapy potential and move into clinical trials, more research focusing on its safety concerns should be conducted.

Cleaning the dose falloff with low modulation in SBRT lung plans

Purpose.This dosimetric study is intended to lower the modulation factor in lung SBRT plans generated in the Eclipse TPS that could replace highly modulated plans that are prone to the interplay effect.Materials and methods.Twenty clinical lung SBRT plans with high modulation factors (≥4) were replanned in Varian Eclipse TPS version 15.5 utilizing 2 mm craniocaudal and 1 mm axial block margins followed by light optimization in order to reduce modulation. A unique plan optimization methodology, which utilizes a novel shell structure (OptiForR₅₀) for R_50%optimization in addition to five consecutive concentric 5 mm shells, was utilized to control dose falloff according to RTOG 0813 and 0915 recommendations. The prescription varied from 34-54 Gy in 1-4 fractions, and the dose objectives were PTV D_95%= Rx, PTV D_max< 140% of Rx, and minimizing the modulation factor. Plan evaluation metrics included modulation factor, CI_RTOG, homogeneity index (HI), R_50%, D_2cm, V_105%, and lung V_8-12.8Gy(Timmerman Constraint). A random-intercept linear mixed effects model was used with a p ≤ 0.05 threshold to test for statistical significance.Results.The retrospectively generated plans had significantly lower modulation factors (3.65 ± 0.35 versus 4.59 ± 0.54; p < 0.001), lower CI_RTOG(0.97 ± 0.02 versus 1.02 ± 0.06; p = 0.001), higher HI (1.35 ± 0.06 versus 1.14 ± 0.04; p < 0.001), lower R_50%(4.09 ± 0.45 versus 4.56 ± 0.56; p < 0.001), and lower lungs V_8-12.8Gy(Timmerman) (4.61% ± 3.18% versus 4.92% ± 3.37%; p < 0.001). The high dose spillage V_105%was borderline significantly lower (0.44% ± 0.49% versus 1.10% ± 1.64%; p = 0.051). The D_2cmwas not statistically different (46.06% ± 4.01% versus 46.19% ± 2.80%; p = 0.835).Conclusion.Lung SBRT plans with significantly lower modulation factors can be generated that meet the RTOG constraints, using our planning strategy.

Gas-modulating microcapsules for spatiotemporal control of hypoxia

Oxygen is a vital molecule involved in regulating development, homeostasis, and disease. The oxygen levels in tissue vary from 1 to 14% with deviations from homeostasis impacting regulation of various physiological processes. In this work, we developed an approach to encapsulate enzymes at high loading capacity, which precisely controls the oxygen content in cell culture. Here, a single microcapsule is able to locally perturb the oxygen balance, and varying the concentration and distribution of matrix-embedded microcapsules provides spatiotemporal control. We demonstrate attenuation of hypoxia signaling in populations of stem cells, cancer cells, endothelial cells, cancer spheroids, and intestinal organoids. Varying capsule placement, media formulation, and timing of replenishment yields tunable oxygen gradients, with concurrent spatial growth and morphogenesis in a single well. Capsule containing hydrogel films applied to chick chorioallantoic membranes encourages neovascularization, providing scope for topical treatments or hydrogel wound dressings. This platform can be used in a variety of formats, including deposition in hydrogels, as granular solids for 3D bioprinting, and as injectable biomaterials. Overall, this platform's simplicity and flexibility will prove useful for fundamental studies of oxygen-mediated processes in virtually any in vitro or in vivo format, with scope for inclusion in biomedical materials for treating injury or disease.

The poorly immunogenic tumor microenvironment of pancreatic cancer: the impact of radiation therapy, and strategies targeting resistance

Pancreatic cancer is one of the most lethal cancers, due to its uniquely aggressive behavior and resistance to therapy. The tumor microenvironment of pancreatic cancer is immunosuppressive, and attempts at utilizing immunotherapies have been unsuccessful. Radiation therapy (RT) results in immune activation and antigen presentation in other cancers, but in pancreatic cancer has had limited success in stimulating immune responses. RT activates common pathways of fibrosis and chronic inflammation seen in pancreatic cancer, resulting in immune suppression. Here we describe the pancreatic tumor microenvironment with regard to fibrosis, myeloid and lymphoid cells, and the impact of RT. We also describe strategies of targeting these pathways that have promise to improve outcomes by harnessing the cytotoxic and immune-activating aspects of RT.

2-Amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitriles with microtubule disruptive, centrosome declustering and antiangiogenic effects in vitro and in vivo

A series of fifteen 2‐amino‐4‐aryl‐5‐oxo‐4,5‐dihydropyrano[3,2‐c]chromene‐3‐carbonitriles (1 a–o) were synthesized via a three‐component reaction of 4‐hydroxycoumarin, malononitrile, and diversely substituted benzaldehydes or pyridine carbaldehydes. The compounds were tested for anticancer activities against a panel of eight human tumor cell lines. A few derivatives with high antiproliferative activities and different cancer cell specificity were identified and investigated for their modes of action. They led to microtubule disruption, centrosome de‐clustering and G2/M cell cycle arrest in 518 A2 melanoma cells. They also showed anti‐angiogenic effects in vitro and in vivo.

Intracellular Signaling Responses Induced by Radiation within an In Vitro Bone Metastasis Model after Pre-Treatment with an Estrone Analogue

2-Ethyl-3-O-sulfamoyl-estra-1,3,5(10)16-tetraene (ESE-16) is an in silico-designed estradiol analogue which has improved the parent compound’s efficacy in anti-cancer studies. In this proof-of-concept study, the potential radiosensitizing effects of ESE-16 were investigated in an in vitro deconstructed bone metastasis model. Prostate (DU 145) and breast (MDA-MB-231) tumor cells, osteoblastic (MC3T3-E1) and osteoclastic (RAW 264.7) bone cells and human umbilical vein endothelial cells (HUVECs) were representative components of such a lesion. Cells were exposed to a low-dose ESE-16 for 24 hours prior to radiation at non-lethal doses to determine early signaling and molecular responses of this combination treatment. Tartrate-resistant acid phosphatase activity and actin ring formation were investigated in osteoclasts, while cell cycle progression, reactive oxygen species generation and angiogenic protein expression were investigated in HUVECs. Increased cytotoxicity was evident in tumor and endothelial cells while bone cells appeared to be spared. Increased mitotic indices were calculated, and evidence of increased deoxyribonucleic acid damage with retarded repair, together with reduced metastatic signaling was observed in tumor cells. RAW 264.7 macrophages retained their ability to differentiate into osteoclasts. Anti-angiogenic effects were observed in HUVECs, and expression of hypoxia-inducible factor 1-α was decreased. Through preferentially inducing tumor cell death and potentially inhibiting neovascularization whilst preserving bone physiology, this low-dose combination regimen warrants further investigation for its promising therapeutic application in bone metastases management, with the additional potential of limited treatment side effects.

Metabolic heterogeneity in cancer: An overview and therapeutic implications

Recent research on cancer metabolism has revealed that individual tumors have highly heterogeneous metabolic profiles that contribute to the connective metabolic networks within the tumor and its environment. Indeed, tumor-associated cells types, including tumor cells, cancer-associated fibroblasts (CAFs) and immune cells, reprogram their metabolism in many different ways due to diverse genetic backgrounds and complex environmental stimuli. This intratumoral metabolic heterogeneity and the derived metabolic interactions play an instrumental role in cancer progression. Understanding how this heterogeneity occurs may provide promising therapeutic strategies. Here, we review the diverse metabolic profiles of several important cell subpopulations in tumors and their impact on tumor progression and discuss the consequent metabolic interactions as well as the related therapeutic concerns.

HIF1α-dependent upregulation of ATAD2 promotes proliferation and migration of stomach cancer cells in response to hypoxia

Stomach cancer is a difficult-to-treat disease. Lack of detection markers and limited understanding of the disease mechanisms contribute to the aggressive nature of stomach cancer cells (SCCs). Recently, an ATPase, ATAD2 has been found to be highly expressed in stomach cancer contributing to increased malignancy. However, nothing is known about the mechanism of ATAD2 upregulation and its involvement in stomach carcinogenesis. Since hypoxic microenvironment plays a crucial role in the progression of solid tumors like stomach cancer; we have examined the regulation and function of ATAD2 expression in hypoxic SCCs. ATAD2 is induced in hypoxia-treated SCCs. Stomach adenocarcinoma and metastatic tissues with high HIF1α level also show enhanced ATAD2 expression. In the absence of hypoxia-inducible factor HIF1α, ATAD2 protein level is found to be less indicating towards a potential correlation between them. We identify the presence of HIF1α-binding site (HBS) and HIF1α ancillary site (HAS) in the ATAD2 promoter. Using both in vitro and in vivo binding studies, we confirm that HIF1α binds with the ATAD2 promoter in hypoxic condition. ATAD2 upregulation promotes proliferation and migration of SCCs exposed to hypoxia. Thus, we identify ATAD2 as a hypoxia-responsive and HIF1α-regulated gene and elucidate that upregulated expression of ATAD2 enhances tumor-promoting functions in hypoxic SCCs. Therefore, we propose ATAD2 as a promising therapeutic target for stomach cancer.

B cell lymphoma with different metabolic characteristics show distinct sensitivities to metabolic inhibitors

Purpose: Cancer cells exhibit profound alterations in their metabolism (abnormal glucose and glutamine metabolism). Targeting cancer metabolism is a promising therapeutic strategy. Lymphoma can be classified into many different types and it is very complicated. Therefore, in this paper, we want to know whether the B cell lymphoma cells with different metabolic characteristics have distinct sensitivities to metabolic inhibitors. Methods: We classified 9 B cell lymphoma cell lines into different metabolic subtypes according to the dependency on glutamine and glucose. Then we detected the OCR, ECAR, glucose consumption and lactate production, mitochondrial content and growth rate. And we also determined the IC50 of these 9 cell lines to metabolic inhibitors. Results: According to the dependency on glutamine and glucose, we successfully classified three distinct metabolic subtypes in B cell lymphoma cell lines, one subtype was defined glutamine and glucose equally utilized subtype (GLN=Glu), whereas the other two subtypes were GLN-addicted and Glu-dependent. And these three subtypes showed striking differences in glucose and glutamine utilization, glycolysis and mitochondrial function, and proliferation rate. GLN-addicted and Glu-dependence subtypes also showed differences in cell sensitivity to inhibitors of glutamine and glycolysis metabolism, respectively. However, GLN=Glu subtype seems minimal sensitive to glycolytic and glutaminolytic inhibitors, and with high proliferation rate. Conclusions: The cells rely more on glucose/gltamine have a stronger sensitivity to glucose/glutamine depletion or glycolysis/ glutaminolysis inhibition and a lessened sensitivity to glutaminolysis/glycolysis inhibitors. To target tumor metabolism based on metabolic characteristics may provide a new therapeutic strategy for the treatment of B cell lymphoma.

Identification of Potential MR-Derived Biomarkers for Tumor Tissue Response to 177Lu-Octreotate Therapy in an Animal Model of Small Intestine Neuroendocrine Tumor

Magnetic resonance (MR) methods enable noninvasive, regional tumor therapy response assessment, but associations between MR parameters, underlying biology, and therapeutic effects must be investigated. The aim of this study was to investigate response assessment efficacy and biological associations of MR parameters in a neuroendocrine tumor (NET) model subjected to radionuclide treatment. Twenty-one mice with NETs received 177Lu-octreotate at day 0. MR experiments (day -1, 1, 3, 8, and 13) included T2-weighted, dynamic contrast-enhanced (DCE) and diffusion-weighted imaging (DWI) and relaxation measurements (T1/T2*). Tumor tissue was analyzed using proteomics. MR-derived parameters were evaluated for each examination day and for different radial distances from the tumor center. Response assessment efficacy and biological associations were evaluated using feature selection and protein expression correlations, respectively. Reduced tumor growth rate or shrinkage was observed until day 8, followed by reestablished growth in most tumors. The most important MR parameter for response prediction was DCE-MRI-derived pretreatment signal enhancement ratio (SER) at 40% to 60% radial distance, where it correlated significantly also with centrally sampled protein CCD89 (association: DNA damage and repair, proliferation, cell cycle arrest). The second most important was changed diffusion (D) between day -1 and day 3, at 60% to 80% radial distance, where it correlated significantly also with peripherally sampled protein CATA (association: oxidative stress, proliferation, cell cycle arrest, apoptotic cell death). Important information regarding tumor biology in response to radionuclide therapy is reflected in several MR parameters, SER and D in particular. The spatial and temporal information provided by MR methods increases the sensitivity for tumor therapy response.

The Linkage between Breast Cancer, Hypoxia, and Adipose Tissue

OBJECTIVE

The development of breast cancer cells is linked to hypoxia. The hypoxia-induced factor HIF-1α influences metastasis through neovascularization. Hypoxia seems to decrease the responsiveness to hormonal treatment due to loss of estrogen receptors (ERs). Obesity is discussed to increase hypoxia in adipocytes, which promotes a favorable environment for tumor cells in mammary fat tissue, whereas, tumor cells profit from good oxygen supply and are influenced by its deprivation as target regions within tumors show. This review gives an overview of the current state on research of hypoxia and breast cancer in human adipose tissue.

METHODS

A systematic literature search was conducted on PubMed (2000-2016) by applying hypoxia and/or adipocytes and breast cancer as keywords. Review articles were excluded as well as languages other than English or German. There was no restriction regarding the study design or type of breast cancer. A total of 35 papers were found. Eight studies were excluded due to missing at least two of the three keywords. One paper was removed due to Russian language, and one was dismissed due to lack of adherence. Seven papers were identified as reviews. After applying exclusion criteria, 18 articles were eligible for inclusion.

RESULTS

Two articles describe the impairment of mammary epithelial cell polarization through hypoxic preconditioning. A high amount of adipocytes enhances cancer progression due to the increased expression of HIF-1α which causes the loss of ER α protein as stated in four articles. Four articles analyzed that increased activation of HIF's induces a series of transcriptions resulting in tumor angiogenesis. HIF inhibition, especially when combined with cytotoxic chemotherapy, holds strong potential for tumor suppression as stated in further four articles. In two articles there is evidence of a strong connection between hypoxia, oxidative stress and a poor prognosis for breast cancer via HIF regulated pathways. Acute hypoxia seems to normalize the microenvironment in breast cancer tissue and has proven to affect tumor growth positively as covered in two articles.

CONCLUSION

This review indicates that the development of breast cancer is influenced by hypoxia. A high amount of adipocytes enhances cancer progression due to the increased expression of HIF-1α.

From Prokaryotes to Cancer: Glutamine Flux in Multicellular Units

Bacteria in nature reside in organized communities, termed biofilms, which are composed of multiple individual cells adhering to each other. Similarly, tumors are a multicellular mass with distinct cellular phenotypes. Both tumors and biofilms are considered to be an active interphase between unicellular and multicellular life states. Because both of these units depend on glutamine for growth and survival, we review here glutamine flux within them as a readout for intra- and inter-commensal metabolism. We suggest that the difference between glutamine fluxes in these cellular communities lies mainly in their global multicellular metabolic organization. Both the differences and similarities described here should be taken into account when considering glutamine-targeting therapeutic approaches.

Monitoring Mitochondrial Complex-I Activity Using Novel PET Probe 18F-BCPP-EF Allows Early Detection of Radiotherapy Effect in Murine Squamous Cell Carcinoma

Objectives

Aerobic glycolysis, the main pathway of energy production in tumors (Warburg effect) allows detection of tumors by positron emission tomography (PET) using ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Since ionizing radiation (IR) is reported to switch aerobic glycolysis to mitochondrial oxidative phosphorylation, radiotherapeutic efficacy was monitored by the activity of mitochondrial complex I (MC-I), using a new PET probe ¹⁸F-BCPP-EF, ¹⁸F-2-tert-butyl-4-chloro-5-{6-[2-(2-fluoro-ethoxy)-ethoxy] -pyridine-3-ylmethoxy}-2H-pyridazin-3-one, compared with ¹⁸F-FDG uptake and the apoptosis index.

Methods

Tumor uptake of ¹⁸F-BCPP-EF or ¹⁸F-FDG was examined in C3H/HeN mice inoculated with murine squamous cell carcinoma SCCVII at various time points after a single dose of x-ray irradiation at 0, 6, 15, or 30 Gy. Apoptosis incidence was determined by TUNEL staining in excised tumor tissue.

Results

Tumor growth suppression was dose-dependent; tumor grew 10-fold (0 Gy), 5-fold (6 Gy), 2-fold (15 Gy), and reduced to half in its volume (30 Gy) 14 days after treatment. ¹⁸F-BCPP-EF uptake was significantly increased as early as 3 days after 15 Gy or 30 Gy, when tumor size and apoptosis index showed no difference among radiation doses. In contrast, ¹⁸F-FDG uptake was initially increased dose-dependently, remained elevated up to 7 days, and eventually decreased 10 days after 30 Gy and also 14 days after 15 Gy when tumor size was already reduced. Apoptosis index was increased after irradiation but failed to correlate with tumor response.

Conclusion

Tumor uptake of ¹⁸F-BCPP-EF was increased dose-dependently early after effective doses of IR when ¹⁸F-FDG uptake as well as apoptosis incidence were not indicative of tumor response. The results suggest that ¹⁸F-BCPP-EF is a promising “positive” MC-I imaging PET probe for early detection of efficacy of tumor radiotherapy.

GC/TOF-MS-based metabolomic profiling in cultured fibroblast-like synoviocytes from rheumatoid arthritis

OBJECTIVES

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial inflammation and hyperplasia. Fibroblast-like synoviocytes (FLS) in RA exhibit a tumor cell-like aggressive phenotype. Thus, gas chromatography/time-of-flight-mass spectrometry (GC/TOF-MS) was employed to identify the characteristic metabolic profiling of RA FLS.

METHODS

Metabolite profiling of RA FLS and osteoarthritis (OA) FLS was performed using GC/TOF-MS in conjunction with statistical analyses. We performed metabolite set enrichment analysis to establish which pathways are affected.

RESULTS

A total of 129 metabolites were identified. A principal component analysis and hierarchical clustering analysis demonstrated clear differentiation of the metabolic profiling between RA FLS and OA FLS. The levels of 35 metabolites that belonged to the amines, fatty acids, phosphates, and organic acids class were significantly increased in RA FLS compared to those in OA FLS. Also, the levels of 26 metabolites that belonged to the amino acids, sugars, and sugar alcohols class were significantly decreased in RA FLS compared to those in OA FLS. The sugar metabolism (glycolysis and pentose phosphate pathway) and amino acid metabolism (tyrosine and catecholamine biosynthesis, and protein biosynthesis) were severely disturbed in RA FLS compared to those in OA FLS.

CONCLUSIONS

Our metabolic results suggested that the alteration of sugar metabolism, lipolysis, and amino acid metabolism in RA FLS is related to synovial hyperplasia and inflammation. This is the first metabolomic study to determine metabolic changes characteristic of RA FLS, which will provide valuable information to gain in-depth insights into the pathogenesis of RA.

Imaging metabolic heterogeneity in cancer

As our knowledge of cancer metabolism has increased, it has become apparent that cancer metabolic processes are extremely heterogeneous. The reasons behind this heterogeneity include genetic diversity, the existence of multiple and redundant metabolic pathways, altered microenvironmental conditions, and so on. As a result, methods in the clinic and beyond have been developed in order to image and study tumor metabolism in the in vivo and in vitro regimes. Both regimes provide unique advantages and challenges, and may be used to provide a picture of tumor metabolic heterogeneity that is spatially and temporally comprehensive. Taken together, these methods may hold the key to appropriate cancer diagnoses and treatments in the future.

The Plasma Membrane Calcium Pump in Pancreatic Cancer Cells Exhibiting the Warburg Effect Relies on Glycolytic ATP

Evidence suggests that the plasma membrane Ca²⁺-ATPase (PMCA), which is critical for maintaining a low intracellular Ca²⁺ concentration ([Ca²⁺]_i), utilizes glycolytically derived ATP in pancreatic ductal adenocarcinoma (PDAC) and that inhibition of glycolysis in PDAC cell lines results in ATP depletion, PMCA inhibition, and an irreversible [Ca²⁺]_i overload. We explored whether this is a specific weakness of highly glycolytic PDAC by shifting PDAC cell (MIA PaCa-2 and PANC-1) metabolism from a highly glycolytic phenotype toward mitochondrial metabolism and assessing the effects of mitochondrial versus glycolytic inhibitors on ATP depletion, PMCA inhibition, and [Ca²⁺]_i overload. The highly glycolytic phenotype of these cells was first reversed by depriving MIA PaCa-2 and PANC-1 cells of glucose and supplementing with α-ketoisocaproate or galactose. These culture conditions resulted in a significant decrease in both glycolytic flux and proliferation rate, and conferred resistance to ATP depletion by glycolytic inhibition while sensitizing cells to mitochondrial inhibition. Moreover, in direct contrast to cells exhibiting a high glycolytic rate, glycolytic inhibition had no effect on PMCA activity and resting [Ca²⁺]_i in α-ketoisocaproate- and galactose-cultured cells, suggesting that the glycolytic dependence of the PMCA is a specific vulnerability of PDAC cells exhibiting the Warburg phenotype.

Broadband optical mammography: chromophore concentration and hemoglobin saturation contrast in breast cancer

This study reports the optical characterization and quantitative oximetry of human breast cancer using spectrally-resolved images collected with a broadband, continuous-wave optical mammography instrument. On twenty-six cancer patients, we collected two-dimensional optical mammograms and created maps of the concentrations of hemoglobin, water, and lipids, as well as the oxygen saturation of hemoglobin. For each cancerous breast, we analyzed the difference between the tumor region (as identified by x-ray and optical mammography) and the remainder of breast tissue. With respect to the surrounding tissue, we found that cancer regions have significantly higher concentrations of total hemoglobin (+2.4±0.4 μM) and water (+7±1% v/v), and significantly lower lipid concentration (8±2% v/v) and oxygen saturation of hemoglobin (5±1%). We also found a significant correlation between the tumor optical contrast and the grade of breast cancer as quantified by the Nottingham histologic score; this demonstrates how optical signatures may be representative of metabolic and morphological features, as well as the aggressive potential of the tumor.

Delivery-corrected imaging of fluorescently-labeled glucose reveals distinct metabolic phenotypes in murine breast cancer

When monitoring response to cancer therapy, it is important to differentiate changes in glucose tracer uptake caused by altered delivery versus a true metabolic shift. Here, we propose an optical imaging method to quantify glucose uptake and correct for in vivo delivery effects. Glucose uptake was measured using a fluorescent D-glucose derivative 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-deoxy-D-glucose (2-NBDG) in mice implanted with dorsal skin flap window chambers. Additionally, vascular oxygenation (SO₂) was calculated using only endogenous hemoglobin contrast. Results showed that the delivery factor proposed for correction, “R_D”, reported on red blood cell velocity and injected 2-NBDG dose. Delivery-corrected 2-NBDG uptake (2-NBDG₆₀/R_D) inversely correlated with blood glucose in normal tissue, indicating sensitivity to glucose demand. We further applied our method in metastatic 4T1 and nonmetastatic 4T07 murine mammary adenocarcinomas. The ratio 2-NBDG₆₀/R_D was increased in 4T1 tumors relative to 4T07 tumors yet average SO₂ was comparable, suggesting a shift toward a “Warburgian” (aerobic glycolysis) metabolism in the metastatic 4T1 line. In heterogeneous regions of both 4T1 and 4T07, 2-NBDG₆₀/R_D increased slightly but significantly as vascular oxygenation decreased, indicative of the Pasteur effect in both tumors. These data demonstrate the utility of delivery-corrected 2-NBDG and vascular oxygenation imaging for differentiating metabolic phenotypes in vivo.

The metabolic cooperation between cells in solid cancer tumors

Cancer cells cooperate with stromal cells and use their environment to promote tumor growth. Energy production depends on nutrient availability and O₂ concentration. Well-oxygenated cells are highly proliferative and reorient the glucose metabolism towards biosynthesis, whereas glutamine oxidation replenishes the TCA cycle coupled with OXPHOS-ATP production. Glucose, glutamine and alanine transformations sustain nucleotide and fatty acid synthesis. In contrast, hypoxic cells slow down their proliferation, enhance glycolysis to produce ATP and reject lactate which is recycled as fuel by normoxic cells. Thus, glucose is spared for biosynthesis and/or for hypoxic cell function. Environmental cells, such as fibroblasts and adipocytes, serve as food donors for cancer cells, which reject waste products (CO₂ , H⁺, ammoniac, polyamines…) promoting EMT, invasion, angiogenesis and proliferation. This metabolic-coupling can be considered as a form of commensalism whereby non-malignant cells support the growth of cancer cells. Understanding these cellular cooperations within tumors may be a source of inspiration to develop new anti-cancer agents.

Hypoxia promotes stem-like properties of laryngeal cancer cell lines by increasing the CD133+ stem cell fraction

Evidence indicates that a hypoxic micro-environment plays an essential role in the regulation of cancer stem cells (CSCs). However, whether hypoxia is able to regulate the stem-like biological properties of laryngeal cancer cells remains unknown. In this study, we investigated the influence of hypoxia on the stemness of two laryngeal cancer cell lines, Hep-2 and AMC-HN-8. We cultured the two cell lines under hypoxia and normoxia and examined the influence of hypoxia on the expression of hypoxia-inducible factors (HIFs) and the cancer stem-like properties of these cells, including cell cycle distribution, expression of stem cell genes (OCT4, SOX2 and NANOG) and laryngeal CSC surface marker (CD133), proliferation, invasion, colony formation and sphere formation capacity. We determined that both of these cell lines, when maintained under hypoxic conditions, showed expanded cells in the G0/G1 phase, exhibited preferential expression of stem cell genes and CD133, and manifested upregulation of HIFs. When treated with hypoxia followed by normoxia exposure, the two cell lines exhibited enhanced capacities for proliferation, invasion, and sphere and colony formation compared with cells maintained consistently under normoxia. Our findings indicate that a hypoxic microenvironment may upgrade the stem-like biological properties of laryngeal cancer cell lines by the expansion of the CD133(+) stem cell fraction.

Inhibition of MAPKs, Myc/Max, NFκB, and hypoxia pathways by Phyllanthus prevents proliferation, metastasis and angiogenesis in human melanoma (MeWo) cancer cell line

BACKGROUND

Melanoma is the most fatal form of skin cancer. Different signalling pathways and proteins will be differentially expressed to pace with the tumour growth. Thus, these signalling molecules and proteins are become potential targets to halt the progression of cancer. The present works were attempted to investigate the underlying molecular mechanisms of anticancer effects of Phyllanthus (P.amarus, P.niruri, P.urinaria and P.watsonii) on skin melanoma, MeWo cells.

METHODS

The ten cancer-related pathways reporter array was performed by transfection of plasmid construct of transcription factor-responsive reporter of each pathway in MeWo cells. The affected pathways in MeWo cells after treatment of Phyllanthus extracts were determined using luciferase assay. Western blot, 2D gel electrophoresis and mass spectrometry analysis were performed to identity and confirm the affected proteins and signalling molecules in treated cells.

RESULTS

The ten-pathway reporter array revealed five different cancer-related signalling pathways were altered by Phyllanthus species in MeWo cells; NFκB, Myc/Max, Hypoxia, MAPK/ERK and MAPK/JNK (p<0.05). Western blot revealed that their intracellular signalling molecules including pan-Ras, c-Raf, RSK, phospho-Elk1, c-myc, Akt, HIF-1α, Bcl-2, and VEGF were down-regulated with concurrent of up-regulation; Bax, phospho-JNK-1/2 and phospho-GSK3β, in MeWo cells upon Phyllanthus treatment (p<0.05). Proteomics-based approach was performed and MS/MS results revealed that 52 differential expressed proteins were identified (p<0.05) and involved in tumour growth, metastasis, apoptosis, glycogenesis and glycolysis, angiogenesis, protein synthesis and energy metabolism.

CONCLUSION

This study provides insight into the regulation on multiple survival signalling pathways by Phyllanthus in melanoma and might be a therapeutic target for cancer treatment.

Role of integrated cancer nanomedicine in overcoming drug resistance

Cancer remains a major killer of mankind. Failure of conventional chemotherapy has resulted in recurrence and development of virulent multi drug resistant (MDR) phenotypes adding to the complexity and diversity of this deadly disease. Apart from displaying classical physiological abnormalities and aberrant blood flow behavior, MDR cancers exhibit several distinctive features such as higher apoptotic threshold, aerobic glycolysis, regions of hypoxia, and elevated activity of drug-efflux transporters. MDR transporters play a pivotal role in protecting the cancer stem cells (CSCs) from chemotherapy. It is speculated that CSCs are instrumental in reviving tumors after the chemo and radiotherapy. In this regard, multifunctional nanoparticles that can integrate various key components such as drugs, genes, imaging agents and targeting ligands using unique delivery platforms would be more efficient in treating MDR cancers. This review presents some of the important principles involved in development of MDR and novel methods of treating cancers using multifunctional-targeted nanoparticles. Illustrative examples of nanoparticles engineered for drug/gene combination delivery and stimuli responsive nanoparticle systems for cancer therapy are also discussed.

Microenvironment and tumor cell plasticity: an easy way out

Cancer cells undergo genetic changes allowing their adaptation to environmental changes, thereby obtaining an advantage during the long metastatic route, disseminated of several changes in the surrounding environment. In particular, plasticity in cell motility, mainly due to epigenetic regulation of cancer cells by environmental insults, engage adaptive strategies aimed essentially to survive in hostile milieu, thereby escaping adverse sites. This review is focused on tumor microenvironment as a collection of structural and cellular elements promoting plasticity and adaptive programs. We analyze the role of extracellular matrix stiffness, hypoxia, nutrient deprivation, acidity, as well as different cell populations of tumor microenvironment.

The nanomechanical signature of breast cancer

Cancer initiation and progression follow complex molecular and structural changes in the extracellular matrix and cellular architecture of living tissue. However, it remains poorly understood how the transformation from health to malignancy alters the mechanical properties of cells within the tumour microenvironment. Here, we show using an indentation-type atomic force microscope (IT-AFM) that unadulterated human breast biopsies display distinct stiffness profiles. Correlative stiffness maps obtained on normal and benign tissues show uniform stiffness profiles that are characterized by a single distinct peak. In contrast, malignant tissues have a broad distribution resulting from tissue heterogeneity, with a prominent low-stiffness peak representative of cancer cells. Similar findings are seen in specific stages of breast cancer in MMTV-PyMT transgenic mice. Further evidence obtained from the lungs of mice with late-stage tumours shows that migration and metastatic spreading is correlated to the low stiffness of hypoxia-associated cancer cells. Overall, nanomechanical profiling by IT-AFM provides quantitative indicators in the clinical diagnostics of breast cancer with translational significance.

A global view of the biochemical pathways involved in the regulation of the metabolism of cancer cells

Cancer cells increase glucose uptake and reject lactic acid even in the presence of oxygen (Warburg effect). This metabolism reorients glucose towards the pentose phosphate pathway for ribose synthesis and consumes great amounts of glutamine to sustain nucleotide and fatty acid synthesis. Oxygenated and hypoxic cells cooperate and use their environment in a manner that promotes their development. Coenzymes (NAD(+), NADPH,H(+)) are required in abundance, whereas continuous consumption of ATP and citrate precludes the negative feedback of these molecules on glycolysis, a regulation supporting the Pasteur effect. Understanding the metabolism of cancer cells may help to develop new anti-cancer treatments.

Metabolic reprogramming of the tumor

Cancer is classically considered as a genetic and, more recently, epigenetic multistep disease. Despite seminal studies in the 1920s by Warburg showing a characteristic metabolic pattern for tumors, cancer bioenergetics has often been relegated to the backwaters of cancer biology. This review aims to provide a historical account on cancer metabolism research, and to try to integrate and systematize the metabolic strategies in which cancer cells engage to overcome selective pressures during their inception and evolution. Implications of this renovated view on some common concepts and in therapeutics are also discussed.

Pyruvate kinase expression (PKM1 and PKM2) in cancer-associated fibroblasts drives stromal nutrient production and tumor growth

We have previously demonstrated that enhanced aerobic glycolysis and/or autophagy in the tumor stroma supports epithelial cancer cell growth and aggressive behavior, via the secretion of high-energy metabolites. These nutrients include lactate and ketones, as well as chemical building blocks, such as amino acids (glutamine) and nucleotides. Lactate and ketones serve as fuel for cancer cell oxidative metabolism, and building blocks sustain the anabolic needs of rapidly proliferating cancer cells. We have termed these novel concepts the "Reverse Warburg Effect," and the "Autophagic Tumor Stroma Model of Cancer Metabolism." We have also identified a loss of stromal caveolin-1 (Cav-1) as a marker of stromal glycolysis and autophagy. The aim of the current study was to provide genetic evidence that enhanced glycolysis in stromal cells favors tumorigenesis. To this end, normal human fibroblasts were genetically-engineered to express the two isoforms of pyruvate kinase M (PKM1 and PKM2), a key enzyme in the glycolytic pathway. In a xenograft model, fibroblasts expressing PKM1 or PKM2 greatly promoted the growth of co-injected MDA-MB-231 breast cancer cells, without an increase in tumor angiogenesis. Interestingly, PKM1 and PKM2 promoted tumorigenesis by different mechanism(s). Expression of PKM1 enhanced the glycolytic power of stromal cells, with increased output of lactate. Analysis of tumor xenografts demonstrated that PKM1 fibroblasts greatly induced tumor inflammation, as judged by CD45 staining. In contrast, PKM2 did not lead to lactate accumulation, but triggered a "pseudo-starvation" response in stromal cells, with induction of an NFκB-dependent autophagic program, and increased output of the ketone body 3-hydroxy-buryrate. Strikingly, in situ evaluation of Complex IV activity in the tumor xenografts demonstrated that stromal PKM2 expression drives mitochondrial respiration specifically in tumor cells. Finally, immuno-histochemistry analysis of human breast cancer samples lacking stromal Cav-1 revealed PKM1 and PKM2 expression in the tumor stroma. Thus, our data indicate that a subset of human breast cancer patients with a loss of stromal Cav-1 show profound metabolic changes in the tumor microenvironment. As such, this subgroup of patients may benefit therapeutically from potent inhibitors targeting glycolysis, autophagy and/or mitochondrial activity (such as metformin).

Multi-modal strategies for overcoming tumor drug resistance: hypoxia, the Warburg effect, stem cells, and multifunctional nanotechnology

Inefficiencies in systemic drug delivery and tumor residence as well as micro-environmental selection pressures contribute to the development of multidrug resistance (MDR) in cancer. Characteristics of MDR include abnormal vasculature, regions of hypoxia, up-regulation of ABC-transporters, aerobic glycolysis, and an elevated apoptotic threshold. Nano-sized delivery vehicles are ideal for treating MDR cancer as they can improve the therapeutic index of drugs and they can be engineered to achieve multifunctional parameters. The multifunctional ability of nanocarriers makes them more adept at treating heterogeneous tumor mass than traditional chemotherapy. Nanocarriers also have preferential tumor accumulation via the EPR effect; this accumulation can be further enhanced by actively targeting the biological profile of MDR cells. Perhaps the most significant benefit of using nanocarrier drug delivery to treat MDR cancer is that nanocarrier delivery diverts the effects of ABC-transporter mediated drug efflux; which is the primary mechanism of MDR. This review discusses the capabilities, applications, and examples of multifunctional nanocarriers for the treatment of MDR. This review emphasizes multifunctional nanocarriers that enhance drug delivery efficiency, the application of RNAi, modulation of the tumor apoptotic threshold, and physical approaches to overcome MDR.

Role of hypoxia and glycolysis in the development of multi-drug resistance in human tumor cells and the establishment of an orthotopic multi-drug resistant tumor model in nude mice using hypoxic pre-conditioning

Background

The development of multi-drug resistant (MDR) cancer is a significant challenge in the clinical treatment of recurrent disease. Hypoxia is an environmental selection pressure that contributes to the development of MDR. Many cancer cells, including MDR cells, resort to glycolysis for energy acquisition. This study aimed to explore the relationship between hypoxia, glycolysis, and MDR in a panel of human breast and ovarian cancer cells. A second aim of this study was to develop an orthotopic animal model of MDR breast cancer.

Methods

Nucleic and basal protein was extracted from a panel of human breast and ovarian cancer cells; MDR cells and cells pre-exposed to either normoxic or hypoxic conditions. Western blotting was used to assess the expression of MDR markers, hypoxia inducible factors, and glycolytic proteins. Tumor xenografts were established in the mammary fat pad of nu/nu mice using human breast cancer cells that were pre-exposed to either hypoxic or normoxic conditions. Immunohistochemistry was used to assess the MDR character of excised tumors.

Results

Hypoxia induces MDR and glycolysis in vitro, but the cellular response is cell-line specific and duration dependent. Using hypoxic, triple-negative breast cancer cells to establish 100 mm³ tumor xenografts in nude mice is a relevant model for MDR breast cancer.

Conclusion

Hypoxic pre-conditiong and xenografting may be used to develop a multitude of orthotopic models for MDR cancer aiding in the study and treatment of the disease.

Development of EGFR-targeted polymer blend nanocarriers for combination paclitaxel/lonidamine delivery to treat multi-drug resistance in human breast and ovarian tumor cells

Multi-drug resistant (MDR) cancer is a significant clinical obstacle and is often implicated in cases of recurrent, nonresponsive disease. Targeted nanoparticles were made by synthesizing a poly(D,L-lactide-co-glycolide)/poly(ethylene glycol)/epidermal growth factor receptor targeting peptide (PLGA/PEG/EGFR-peptide) construct for incorporation in poly(epsilon-caprolactone) (PCL) nanoparticles. MDR was induced in a panel of nine human breast and ovarian cancer cell lines using hypoxia. EGFR-targeted polymer blend nanoparticles were shown to actively target EGFR overexpressing cell lines, especially upon induction of hypoxia. The nanoparticles were capable of sustained drug release. Combination therapy with lonidamine and paclitaxel significantly improved the therapeutic index of both drugs. Treatment with a nanoparticle dose of 1 μM paclitaxel/10 μM lonidamine resulted in less than 10% cell viability for all hypoxic/MDR cell lines and less than 5% cell viability for all normoxic cell lines. Comparatively, treatment with 1 μM paclitaxel alone was the approximate IC₅₀ value of the MDR cells while treatment with lonidamine alone had very little effect. The PLGA/PEG/EGFR-peptide delivery system actively targets a MDR cell by exploiting the expression of EGFR. This system treats MDR by inhibiting the Warburg effect and promoting mitochondrial binding of pro-apoptotic Bcl-2 proteins (lonidamine), while hyperstabilizing microtubules (paclitaxel). This nanocarrier system actively targets a MDR associated phenotype (EGFR receptor overexpression), further enhancing the therapeutic index of both drugs and potentiating the use of lonidamine/paclitaxel combination therapy in the treatment of MDR cancer.

Genetics of keloid scarring

Keloid scarring, also known as keloid disease (KD), is a common, abnormally raised fibroproliferative cutaneous lesion that can occur following even minor skin trauma. The aetiopathogenesis of KD has remained an enigma todate compounded by an ill-defined clinical management. There is strong evidence suggesting a genetic susceptibility in individuals affected by KD, including familial heritability, common occurrence in twins and high prevalence in certain ethnic populations. This review aims to address the genetic aspects of KD that have been described in present literature that include inheritance patterns, linkage studies, case-control association studies, whole genome gene expression microarray studies and gene pathways that were significant in KD. In addition to our clinical and scientific background in KD, we used search engines, Scopus, Scirus and PubMed, which searched for key terms covering various genetic aspects of KD. Additionally, genes reported in seven whole genome gene expression microarray studies were separately compared in detail. Our findings indicate a varied inheritance pattern in KD (predominantly autosomal dominant), linkage loci (chromosomes 2q23 and 7p11), several human leukocyte antigen (HLA) alleles (HLA-DRB1*15, HLA-DQA1*0104, DQ-B1*0501 and DQB1*0503), negative candidate gene case-control association studies and at least 25 dysregulated genes reported in multiple microarray studies. The major pathways reportedly proposed to be involved in KD include apoptosis, mitogen-activated protein kinase, transforming growth factor-beta, interleukin-6 and plasminogen activator inhibitor-1. In summary, involvement of more than one gene is likely to be responsible for susceptibility to KD. A better understanding of the genes involved in KD may potentially lead to the development of more effective diagnostic, therapeutic and prognostic measures.

The role of cellular oxidative stress in regulating glycolysis energy metabolism in hepatoma cells

Background

The Warburg effect has been found in a wide spectrum of human cancers, however the underlying mechanisms are still unclear. This study aims to explore the role of cellular oxidative stress in relation to glycolysis and the Warburg effect in hepatoma cells.

Methods

Various cell lines combining environmental hypoxia was used as an in vitro model to mimic tumor microenvironment in vivo. Superoxide dismutases (SOD) and xanthine oxidase (XO) gene transfection were used to produce various cellular redox levels. 2',7'-dichlorofluorescin (DCF) fluorescence and ESR spectrum were used to detect cellular reactive oxygen species (ROS).

Results

We found that endogenous or exogenous interference with the cellular oxidative stress can sensitively regulate glycolysis and the Warburg effect in hepatoma cells. Hepatoma cells displayed a high level of free radicals compared to immortalized normal hepatocyte cells. Increasing the level of ROS stress in hepatoma cells can directly upregulate HIF-1 and activate glycolysis without requirement of a hypoxic condition. This explains the mechanism whereby aerobic glycolysis, i.e. the Warburg effect arises. Either endogenously upregulating SOD or exogenously administration with antioxidant can, through downregulating ROS level, effectively regulate energy pathways in hepatoma cells and can inhibit the growth of tumor cells and xenograft tumors.

Conclusion

This study suggests that the Warburg effect was related to an inherently high level of cellular ROS and HIF-1. Hepatoma cells adaptation to hypoxia for survival and rapid growth exploits oxidative stress ectopically activated glycolysis to compensate the energy supply. This specific mechanism in which tumor cells through cellular oxidative stress activate glycolysis to meet their energy metabolism requirement could be exploited to selectively kill tumor cells.

Multi-functional nanocarriers to overcome tumor drug resistance

The development of resistance to variety of chemotherapeutic agents is one of the major challenges in effective cancer treatment. Tumor cells are able to generate a multi-drug resistance (MDR) phenotype due to microenvironmental selection pressures. This review addresses the use of nanotechnology-based delivery systems to overcome MDR in solid tumors. Our own work along with evidence from the literature illustrates the development of various types of engineered nanocarriers specifically designed to enhance tumor-targeted delivery through passive and active targeting strategies. Additionally, multi-functional nanocarriers are developed to enhance drug delivery and overcome MDR by either simultaneous or sequential delivery of resistance modulators (e.g., with P-glycoprotein substrates), agents that regulate intracellular pH, agents that lower the apoptotic threshold (e.g., with ceramide), or in combination with energy delivery (e.g., sound, heat, and light) to enhance the effectiveness of anticancer agents in refractory tumors. In preclinical studies, the use of multi-functional nanocarriers has shown significant promise in enhancing cancer therapy, especially against MDR tumors.

Suppression of adenine nucleotide translocase-2 by vector-based siRNA in human breast cancer cells induces apoptosis and inhibits tumor growth in vitro and in vivo

INTRODUCTION

Adenine nucleotide translocator (ANT) 2 is highly expressed in proliferative cells, and ANT2 induction in cancer cells is known to be directly associated with glycolytic metabolisms and carcinogenesis. In addition, ANT2 repression results in the growth arrest of human cells, implying that ANT2 is a candidate for cancer therapy based on molecular targeting.

METHODS

We utilized an ANT2-specific RNA interference approach to inhibit ANT2 expression for evaluating its antitumor effect in vitro and in vivo. Specifically, to investigate the therapeutic potential of ANT2 repression, we used a DNA vector-based RNA interference approach by expressing shRNA to knockdown ANT2 in breast cancer cell lines overexpressing ANT2.

RESULTS

ANT2 shRNA treatment in breast cancer cell line MDA-MB-231 repressed cell growth as well as proliferation. In addition, cell cycle arrest, ATP depletion and apoptotic cell death characterized by the potential disruption of mitochondrial membrane were observed from the ANT2 shRNA-treated breast cancer cells. Apoptotic breast cancer cells transfected with ANT2 shRNA also induced a cytotoxic bystander effect that generates necrotic cell death to the neighboring cells. The intracellular levels of TNFalpha and TNF-receptor I were increased in ANT2 shRNA transfected cells and the bystander effect was partly blocked by anti-TNFalpha antibody. Ultimately, ANT2 shRNA effectively inhibited tumor growth in vivo.

CONCLUSION

These results suggest that vector-based ANT2 RNA interference could be an efficient molecular therapeutic method for breast cancer with high expression of ANT2.

Prostate carcinoma cells selected by long-term exposure to reduced oxygen tension show remarkable biochemical plasticity via modulation of superoxide, HIF-1alpha levels, and energy metabolism

Cancer cells are able to tolerate levels of O(2) that are damaging or lethal to normal cells; we hypothesize that this tolerance is the result of biochemical plasticity which maintains cellular homeostasis of both energy levels and oxidation state. In order to examine this hypothesis, we used different O(2) levels as a selective agent during long-term culture of DU145 prostate cancer cells to develop three isogenic cell lines that grow in normoxic (4%), hyperoxic (21%), or hypoxic (1%) O(2) conditions. Growth characteristics and O(2) consumption differed significantly between these cell lines without changes in ATP levels or altered sensitivity to 2-deoxy-D-glucose, an inhibitor of glycolysis. O(2) consumption was significantly higher in the hyperoxic line as was the level of endogenous superoxide. The hypoxic cell line regulated the chemical gradient of the proton motive force (PMF) independent of the electrical component without O(2)-dependent changes in Hif-1alpha levels. In contrast, the normoxic line regulated Hif-1alpha without tight regulation of the chemical component of the PMF noted in the hypoxic cell line. From these studies, we conclude that selection of prostate cancer cells by long-term exposure to low ambient levels of O(2) resulted in cells with unique biochemical properties in which energy metabolism, reactive oxygen species (ROS), and HIF-1alpha levels are modulated to allow cell survival and growth. Thus, cancer cells exhibit remarkable biochemical plasticity in response to various O(2) levels.

Protein kinase C-ERK1/2 signal pathway switches glucose depletion-induced necrosis to apoptosis by regulating superoxide dismutases and suppressing reactive oxygen species production in A549 lung cancer cells

Cells typically die by either apoptosis or necrosis. However, the consequences of apoptosis and necrosis are quite different for a whole organism. In the case of apoptosis, the cell content remains packed in the apoptotic bodies that are removed by macrophages, and thereby inflammation does not occur; during necrosis, the cell membrane is ruptured, and the cytosolic constituents are released into the extracellular space provoking inflammation. Recently, inflammation and necrosis have been suggested to promote tumor growth. We investigated the molecular mechanism underlying cell death in response to glucose depletion (GD), a common characteristic of the tumor microenvironment. GD induced necrosis through production of reactive oxygen species (ROS) in A549 lung carcinoma cells. Inhibition of ROS production by N-acetyl-L-cysteine and catalase prevented necrosis and switched the cell death mode to apoptosis that depends on mitochondrial death pathway involving caspase-9 and caspase-3 activation, indicating a critical role of ROS in determination of GD-induced cell death mode. We demonstrate that protein kinase C-dependent extracellular regulated kinase 1/2 (ERK1/2) activation also switched GD-induced necrosis to apoptosis through inhibition of ROS production possibly by inducing manganese superoxide dismutase (SOD) expression and by preventing GD-induced degradation of copper zinc SOD. Thus, these results suggest that GD-induced cell death mode is determined by the protein kinase C/ERK1/2 signal pathway that regulates MnSOD and CuZnSOD and that these antioxidants may exert their known tumor suppressive activities by inducing necrosis-to-apoptosis switch.

A quinoxaline 1,4-di-N-oxide derivative induces DNA oxidative damage not attenuated by vitamin C and E treatment

Some anticancer compounds are pro-drugs which give rise to toxic species through enzymatic reduction. The quinoxaline-di-N-oxide derivative Q-85 HCl (7-chloro-3-[[(N,N-dimethylamino)propyl]amino]-2-quinoxalinecarbonitrile 1,4-di-N-oxide hydrochloride) is a bioreductive compound selectively toxic in hypoxia. Due to the possibility of secondary tumors the study of the genotoxic capability of antitumoral drugs is very important. The aim of this study was to assess the ability of Q-85 HCl to produce reactive oxygen species (ROS) and oxidative DNA damage in Caco-2 cells, both in hypoxia and in well-oxygenated conditions. Secondly, we attempted to evaluate the effect of vitamins C and E under hypoxic and normoxic conditions, in order to determine if these antioxidant substances modify Q-85 HCl effect in hypoxic cells or possibly exert a protective action in normal cells. Caco-2 cells were treated with Q-85 HCl for 2h, at high concentrations in normoxia (0.1-5 microM) and at low concentrations in hypoxia (0.002-0.1 microM). In normoxia, a dose-related significant increase in intracellular ROS level was evident; in hypoxia all the concentrations produced very high level of ROS. Just after the treatment and 24h later, oxidative DNA damage was evaluated by the modified comet assay after post-digestion of the cells with formamidopyrimidine-DNA glycosylase (FPG) and endonuclease III (Endo III). Q-85 HCl treatment evoked a significant dose-dependent increase in the total comet score of the cells both in hypoxia and normoxia, indicating that this compound or some metabolite is able to oxidize purine and pyrimidine bases. After 24h DNA damage caused by the compound was completely repaired with only one exception: cells treated with the highest concentration of Q-85 HCl in hypoxia and post-digested with FPG. Vitamin C (5-100 microM) and vitamin E (500-400 microM) did not have a pro-oxidant effect in Caco-2 cells. Treatment of cells with vitamin C (10 microM) or vitamin E (100 microM) did not significantly reduce oxidative DNA damage in hypoxia and normoxia. In conclusion, the use of these vitamins would not hinder toxicity against hypoxic cells, but a protective effect in normoxic cells was not evident.

Cell surface oxygen consumption: a major contributor to cellular oxygen consumption in glycolytic cancer cell lines

Oxygen consumption for bioenergetic purposes has long been thought to be the prerogative of mitochondria. Nevertheless, mitochondrial gene knockout (rho(0)) cells that are defective in mitochondrial respiration require oxygen for growth and consume oxygen at the cell surface via trans-plasma membrane electron transport (tPMET). This raises the possibility that cell surface oxygen consumption may support glycolytic energy metabolism by reoxidising cytosolic NADH to facilitate continued glycolysis. In this paper we determined the extent of cell surface oxygen consumption in a panel of 19 cancer cell lines. Non-mitochondrial (myxothiazol-resistant) oxygen consumption was demonstrated to consist of at least two components, cell surface oxygen consumption (inhibited by extracellular NADH) and basal oxygen consumption (insensitive to both myxothiazol and NADH). The extent of cell surface oxygen consumption varied considerably between parental cell lines from 1% to 80% of total oxygen consumption rates. In addition, cell surface oxygen consumption was found to be associated with low levels of superoxide production and to contribute significantly (up to 25%) to extracellular acidification in HL60rho(0) cells. In summary, cell surface oxygen consumption contributes significantly to total cellular oxygen consumption, not only in rho(0) cells but also in mitochondrially competent tumour cell lines with glycolytic metabolism.

Expression of transforming K-Ras oncogene affects mitochondrial function and morphology in mouse fibroblasts

K-ras transformed fibroblasts have been shown to have a stronger dependence from glycolysis, reduced oxidative phosphorylation ability and a fragility towards glucose depletion compared to their immortalized, normal counterparts. In this paper, using RNA profiling assays and metabolic perturbations, we report changes in expression of genes encoding mitochondrial proteins and alterations in mitochondrial morphology that correlate with mitochondrial functionality. In fact, unlike normal cells, transformed cells show reduced ATP content and inability to modify mitochondria morphology upon glucose depletion. Being reverted by GEF-DN expression, such morphological and functional changes are directly connected to Ras activation. Taken together with reported partial mitochondrial uncoupling and more sustained apoptosis of transformed cells, our results indicate that activation of the Ras pathway strikingly impacts on energy and signaling-related aspects of mitochondria functionality, that in turn may affect the terminal phenotype of transformed cells.

Multi-tracer small animal PET imaging of the tumour response to the novel pan-Erb-B inhibitor CI-1033

PURPOSE

This study was designed as "proof of concept" for a drug development model utilising multi-tracer serial small animal PET imaging to characterise tumour responses to molecularly targeted therapy.

METHODS

Mice bearing subcutaneous A431 human squamous carcinoma xenografts (n=6-8) were treated with the pan-Erb-B inhibitor CI-1033 or vehicle and imaged serially (days 0, 3 and 6 or 7) with [(18)F]fluorodeoxyglucose, [(18)F]fluoro-L: -thymidine, [(18)F]fluoro-azoazomycinarabinoside or [(18)F]fluoromisonidazole. Separate cohorts (n=3) were treated identically and tumours were assessed ex vivo for markers of glucose metabolism, proliferation and hypoxia.

RESULTS

During the study period, mean uptake of all PET tracers generally increased for control tumours compared to baseline. In contrast, tracer uptake into CI-1033-treated tumours decreased by 20-60% during treatment. Expression of the glucose transporter Glut-1 and cell cycle markers was unchanged or increased in control tumours and generally decreased with CI-1033 treatment, compared to baseline. Thymidine kinase activity was reduced in all tumours compared to baseline at day 3 but was sevenfold higher in control versus CI-1033-treated tumours by day 6 of treatment. Uptake of the hypoxia marker pimonidazole was stable in control tumours but was severely reduced following 7 days of CI-1033 treatment.

CONCLUSION

CI-1033 treatment significantly affects tumour metabolism, proliferation and hypoxia as determined by PET. The PET findings correlated well with ex vivo biomarkers for each of the cellular processes studied. These results confirm the utility of small animal PET for evaluation of the effectiveness of molecularly targeted therapies and simultaneously definition of specific cellular processes involved in the therapeutic response.

Homoplasmic MELAS A3243G mtDNA mutation in a colon cancer sample

We have analyzed mtDNA variation in various cancer samples, comparing them with normal tissue controls, and identified mutations and polymorphisms, both known and novel, in mitochondrial tRNA, rRNA and protein genes. Most remarkably, in a colon cancer sample we have found the A3243G mutation in the homoplasmic state. This mutation is known to cause severe mitochondrial dysfunction and, until now, has not been found in cancer cells, nor in the homoplasmic state in living subjects. The mutation was absent from normal tissue, suggesting that mtDNA mutation and resulting respiratory deficiency played a role in carcinogenesis.

Quantitative biochemical analysis of lactate dehydrogenase in human ovarian tissues: correlation with tumor grade

In an attempt to identify glycolytic capacity of normal and neoplastic human ovary, total lactate dehydrogenase (LDH) activity was measured in tissue cytosol originating from 69 patients (18 with benign ovarian tumor, 34 with ovarian carcinoma, six with nonepithelial ovarian malignant tumors, and 11 with tumor metastatic to ovary) and compared to the LDH activity of normal ovarian tissues (n = 19). Median value of total LDH-specific activity expressed as U/mg protein was 0.546 in normal tissues, 0.584 in benign tumors, 1.071 in malignancies metastatic to ovaries, 0.872 in nonepithelial primary ovarian tumors, and 0.818 in primary carcinomas. A significant rise in LDH-specific activity was found in malignant primary and secondary tumors of epithelial and nonepithelial origin, but not in benign neoplasms, compared to the activity in normal tissue. Ovarian carcinomas of serous histologic type did not differ in LDH activity from mucinous tumors. However, poorly differentiated carcinomas (grade 3) showed significantly enhanced activity of this glycolytic enzyme when compared to its grade 1 counterpart. The subgroup of grade 1 tumors did not differ in LDH activity from normal and benign ovarian tissue. Obtained results suggest that direct correlation might exist between ovarian epithelial tumor grade and lactate dehydrogenase activity.