Mechanisms of tumor growth retardation by modulation of pH regulation in the tumor-microenvironment of a murine T cell lymphoma

Orchestral role of lipid metabolic reprogramming in T-cell malignancy

The immune function of normal T cells partially depends on the maneuvering of lipid metabolism through various stages and subsets. Interestingly, T-cell malignancies also reprogram their lipid metabolism to fulfill bioenergetic demand for rapid division. The rewiring of lipid metabolism in T-cell malignancies not only provides survival benefits but also contributes to their stemness, invasion, metastasis, and angiogenesis. Owing to distinctive lipid metabolic programming in T-cell cancer, quantitative, qualitative, and spatial enrichment of specific lipid molecules occur. The formation of lipid rafts rich in cholesterol confers physical strength and sustains survival signals. The accumulation of lipids through de novo synthesis and uptake of free lipids contribute to the bioenergetic reserve required for robust demand during migration and metastasis. Lipid storage in cells leads to the formation of specialized structures known as lipid droplets. The inimitable changes in fatty acid synthesis (FAS) and fatty acid oxidation (FAO) are in dynamic balance in T-cell malignancies. FAO fuels the molecular pumps causing chemoresistance, while FAS offers structural and signaling lipids for rapid division. Lipid metabolism in T-cell cancer provides molecules having immunosuppressive abilities. Moreover, the distinctive composition of membrane lipids has implications for immune evasion by malignant cells of T-cell origin. Lipid droplets and lipid rafts are contributors to maintaining hallmarks of cancer in malignancies of T cells. In preclinical settings, molecular targeting of lipid metabolism in T-cell cancer potentiates the antitumor immunity and chemotherapeutic response. Thus, the direct and adjunct benefit of lipid metabolic targeting is expected to improve the clinical management of T-cell malignancies.

BAPST. A Combo of Common use drugs as metabolic therapy of cancer-a theoretical proposal

Advances in cancer therapy have yet to impact worldwide cancer mortality. Poor cancer drug affordability is one of the factors limiting mortality burden strikes. Up to now, cancer drug repurposing had no meet expectations concerning drug affordability. The three FDA-approved cancer drugs developed under repurposing -all-trans-retinoic acid, arsenic trioxide, and thalidomide- do not differ in price from other drugs developed under the classical model. Though additional factors affect the whole process from inception to commercialization, the repurposing of widely used, commercially available, and cheap drugs may help. This work reviews the concept of the malignant metabolic phenotype and its exploitation by simultaneously blocking key metabolic processes altered in cancer. We elaborate on a combination called BAPST, which stands for the following drugs and pathways they inhibit: Benserazide (glycolysis), Apomorphine (glutaminolysis), Pantoprazole (Fatty-acid synthesis), Simvastatin (mevalonate pathway), and Trimetazidine (Fatty-acid oxidation). Their respective primary indications are: • Parkinson's disease (benserazide and apomorphine). • Peptic ulcer disease (pantoprazole). • Hypercholesterolemia (simvastatin). • Ischemic heart disease (trimetazidine). When used for their primary indication, the literature review on each of these drugs shows they have a good safety profile and lack predicted pharmacokinetic interaction among them. Most importantly, the inhibitory enzymatic concentrations required for inhibiting their cancer targets enzymes are below the plasma concentrations observed when these drugs are used for their primary indication. Based on that, we propose that the regimen BAPTS merits preclinical testing.

Esomeprazole enhances the effect of ionizing radiation to improve tumor control

The resistance of cancer cells to radiation-based treatment is a major clinical challenge confounding standard of care in cancer. This problem is particularly notable in many solid tumors where cancer cells are only partially responsive to radiation therapy. Combination of radiation with radiosensitizers is able to enhance tumor cell killing. However, currently available radiosensitizers are associated with significant normal tissue toxicity. Accordingly, there is an unmet need to develop safer and more effective radiosensitizers to improve tumor control. Here, we evaluated the radiosensitizing effect of the FDA-approved drug esomeprazole in normal and radioresistant human head and neck squamous cell carcinoma (HNSCC) cells in vitro, and in a mouse model of HNSCC. For the in vitro studies, we used cancer cell colony formation (clonogenicity) assay to compare cancer cell growth in the absence or presence of esomeprazole. To determine mechanism(s) of action, we assessed cell proliferation and profiled cell cycle regulatory proteins. In addition, we performed reverse phase protein array (RPPA) study to understand the global effect of esomeprazole on over 200 cancer-related proteins. For the in vivo study, we engrafted HNSCC in a mouse model and compared tumor growth in animals treated with radiation, esomeprazole, and combination of radiation with esomeprazole. We found that esomeprazole inhibits tumor growth and dose-dependently enhances the cell killing effect of ionizing radiation in wildtype and p53-mutant radioresistant cancer cells. Mechanistic studies demonstrate that esomeprazole arrests cancer cells in the G1 phase of the cell cycle through upregulation of p21 protein and inhibition of cyclin-dependent kinases (Cdks) type 1 (Cdk1) and type 2 (Cdk2). In vivo data showed greater tumor control in animals treated with combination of radiation and esomeprazole compared to either treatment alone, and that this was associated with inhibition of cell proliferation in vivo. In addition, combination of esomeprazole with radiation significantly impaired repair following radiation-induced DNA damage. Our studies indicate that esomeprazole sensitizes cancer cells to ionizing radiation, and is associated with upregulation of p21 to arrest cells in the G1 phase of the cell cycle. Our findings have significant therapeutic implications for the repurposing of esomeprazole as a radiosensitizer in HNSCC and other solid tumors.

Curcumin circumvent lactate-induced chemoresistance in hepatic cancer cells through modulation of hydroxycarboxylic acid receptor-1

Curcumin has been demonstrated to affect the chemoresistance in cancer cells of various origins. However, its ability to modulate lactate-induced chemoresistance remains unclear. The Present investigation demonstrates that curcumin inhibits the survival of HepG2 and HuT78 cells and can modulate chemo-susceptibility of HepG2 cells. Experimental simulation of simultaneous and pre-treatment suggest cooperatively between curcumin and anticancer drugs as well as the modulation of molecular regulators. Inhibition of glucose consumption, lactate production, extracellular acidity and augmented level of Nitric oxide were observed. DAPI staining revealed hyper condensation of chromatin in curcumin-treated HepG2 cells. Curcumin also diminished the lactate-induced chemoresistance against doxorubicin in hepatic cancer cells along with down regulation of lactate receptor (hydroxycarboxylic acid receptor-1; HCAR-1/GPR81). Alteration of the extracellular milieu along with inhibited expression of genes (hif-1α, ldh-a, mct-1, mdr-1 and stat-3) and proteins (HIF-1α and HCAR-1) are indicated to be involved in curcumin-induced reversal of chemoresistance in HepG2 cells. Findings of present investigation contribute to knowledge of curcumin mediated chemosensitization and its mechanism.

Diverse Stakeholders of Tumor Metabolism: An Appraisal of the Emerging Approach of Multifaceted Metabolic Targeting by 3-Bromopyruvate

Malignant cells possess a unique metabolic machinery to endure unobstructed cell survival. It comprises several levels of metabolic networking consisting of 1) upregulated expression of membrane-associated transporter proteins, facilitating unhindered uptake of substrates; 2) upregulated metabolic pathways for efficient substrate utilization; 3) pH and redox homeostasis, conducive for driving metabolism; 4) tumor metabolism-dependent reconstitution of tumor growth promoting the external environment; 5) upregulated expression of receptors and signaling mediators; and 6) distinctive genetic and regulatory makeup to generate and sustain rearranged metabolism. This feat is achieved by a "battery of molecular patrons," which acts in a highly cohesive and mutually coordinated manner to bestow immortality to neoplastic cells. Consequently, it is necessary to develop a multitargeted therapeutic approach to achieve a formidable inhibition of the diverse arrays of tumor metabolism. Among the emerging agents capable of such multifaceted targeting of tumor metabolism, an alkylating agent designated as 3-bromopyruvate (3-BP) has gained immense research focus because of its broad spectrum and specific antineoplastic action. Inhibitory effects of 3-BP are imparted on a variety of metabolic target molecules, including transporters, metabolic enzymes, and several other crucial stakeholders of tumor metabolism. Moreover, 3-BP ushers a reconstitution of the tumor microenvironment, a reversal of tumor acidosis, and recuperative action on vital organs and systems of the tumor-bearing host. Studies have been conducted to identify targets of 3-BP and its derivatives and characterization of target binding for further optimization. This review presents a brief and comprehensive discussion about the current state of knowledge concerning various aspects of tumor metabolism and explores the prospects of 3-BP as a safe and effective antineoplastic agent.

Antimetabolic Agent 3-Bromopyruvate Exerts Myelopotentiating Action in a Murine Host Bearing a Progressively Growing Ascitic Thymoma

Tumor growth and its chemotherapeutic regimens manifest myelosuppression, which is one of the possible causes underlying the limited success of immunotherapeutic anticancer strategies. Hence, approaches are being designed to develop safer therapeutic regimens that may have minimal damaging action on the process of myelopoiesis. 3-Bromopyruvate (3-BP) is a highly potent antimetabolic agent displaying a broad spectrum antineoplastic activity. However, 3-BP has not been investigated for its effect on the process of myelopoiesis in a tumor-bearing host. Hence, in this investigation, we studied the myelopoietic effect of in vivo administration of 3-BP to a murine host bearing a progressively growing ascitic thymoma designated as Dalton's lymphoma (DL). 3-BP administration to the DL-bearing mice resulted in a myelopotentiating action, reflected by an elevated count of bone marrow cells (BMC) accompanied by augmented proliferative ability and a declined induction of apoptosis. The BMC of 3-BP-administered mice displayed enhanced responsiveness to macrophage colony-stimulating factor for colony-forming ability of myeloid lineage along with an enhanced differentiation of F4/80⁺ bone marrow-derived macrophages (BMDM). BMDM differentiated from the BMC of 3-BP-administered DL-bearing mice showed an augmented response to lipopolysaccharide and interferon-γ for activation, displaying an augmented tumor cytotoxicity, expression of cytokines, reactive oxygen species, nitric oxide, CD11c, TLR-4, and HSP70. These features are indicative of the differentiation of M1 subtype of macrophages. Thus, this study demonstrates the myelopotentiating action of 3-BP, indicating its hematopoietic safety and potential for reinforcing the differentiation of macrophages in a tumor-bearing host.

Invariant Natural Killer T Cells in Immune Regulation of Blood Cancers: Harnessing Their Potential in Immunotherapies

Invariant natural killer T (iNKT) cells are a unique innate T lymphocyte population that possess cytolytic properties and profound immunoregulatory activities. iNKT cells play an important role in the immune surveillance of blood cancers. They predominantly recognize glycolipid antigens presented on CD1d, but their activation and cytolytic activities are not confined to CD1d expressing cells. iNKT cell stimulation and subsequent production of immunomodulatory cytokines serve to enhance the overall antitumor immune response. Crucially, the activation of iNKT cells in cancer often precedes the activation and priming of other immune effector cells, such as NK cells and T cells, thereby influencing the generation and outcome of the antitumor immune response. Blood cancers can evade or dampen iNKT cell responses by downregulating expression of recognition receptors or by actively suppressing or diverting iNKT cell functions. This review will discuss literature on iNKT cell activity and associated dysregulation in blood cancers as well as highlight some of the strategies designed to harness and enhance iNKT cell functions against blood cancers.

Repositioning of proton pump inhibitors in cancer therapy

Drug repositioning, as a smart way to exploit new molecular targets of a known drug, has been gaining increasing attention in the discovery of anti-cancer drugs. Proton pump inhibitors (PPIs) as benzimidazole derivatives, which are essentially H⁺-K⁺-ATPases inhibitors, are commonly used in the treatment of acid-related diseases such as gastric ulcer. In recent years, exploring the new application of PPIs in anti-cancer field has become a hot research topic. Interestingly, cancer cells display an alkaline intracellular pH and an acidic extracellular pH. The extracellular acidity of tumors can be corrected by PPIs that are selectively activated in an acid milieu. It is generally believed that PPIs might provoke disruption of pH homeostasis by targeting V-ATPase on cancer cells, which is the theoretical basis for PPIs to play an anti-cancer role. Numerous studies have shown specialized effects of the PPIs on tumor cell growth, metastasis, chemoresistance, and autophagy. PPIs may really represent new anti-cancer drugs due to better safety and tolerance, the potential selectivity in targeting tumor acidity, and the ability to inhibit mechanism pivotal for cancer homeostasis. In this review, we focus on the new therapeutic applications of PPIs in multiple cancers, explaining the rationale behind this approach and providing practical evidence.

A Transistor-like pH Nanoprobe for Tumour Detection and Image-guided Surgery

Because of profound genetic and histological differences in cancerous tissue, it is challenging to detect a broad range of malignant tumours at high resolution. Here, we report the design and performance of a fluorescent nanoprobe with transistor-like responses (transition pH = 6.9) for the detection of the deregulated pH that drives many of the invasive properties of cancer. The nanoprobe amplifies fluorescence signal in the tumour over that in the surrounding normal tissues, resulting in a discretized, binary output signal with spatial resolution smaller than 1 mm. The nanoprobe allowed us to image a broad range of tumours in mouse models using a variety of clinical cameras, and to perform real-time tumour-acidosis-guided detection and surgery of occult nodules (< 1 mm3) in mice bearing head-and-neck or breast tumours, significantly lengthening mice survivability. We also show that the pH nanoprobe can be used as a reporter in a fast, quantitative assay to screen for tumour-acidosis inhibitors. The binary delineation of pH achieved by the nanoprobe promises to improve the accuracy of cancer detection, surveillance and therapy.

Relationship between proton pump inhibitors and tumors

Proton pump inhibitors (PPIs) as benzene and imidazole derivatives are in essence H⁺-K⁺-ATPases inhibitors, and they are commonly used in the treatment of acid related diseases such as gastric ulcer. In recent years, exploring the relationship between PPIs and tumors has become a hot research topic. This paper summarizes the relationship of PPIs with tumor microenvironment, the improvement of drug resistance mechanisms, and related signaling pathways, with an aim to provide clues for the treatment of tumors.

Bicarbonate transport inhibitor SITS modulates pH homeostasis triggering apoptosis of Dalton's lymphoma: implication of novel molecular mechanisms

Bicarbonate transporter (BCT) plays a crucial role in maintaining pH homeostasis of tumor cells by import of HCO3(-). This helps the tumor cells in manifesting extracellular tumor acidosis, accompanied by a relative intracellular alkalinization, which in turn promotes tumor progression. Therefore, blocking BCT-mediated HCO3(-) transport is envisaged as a promising anticancer therapeutic approach. Thus, using a murine model of a T cell lymphoma, designated as Dalton's lymphoma (DL), in the present in vitro investigation the antitumor consequences of blocking BCT function by its inhibitor 4-acetamido-4-isothiocyanostilbene-2,2-disulfonate (SITS) were explored. Treatment of DL cells with SITS resulted in an increase in the extracellular pH, associated with a decline in DL cell survival and augmented induction of apoptosis. BCT inhibition also elevated the expression of cytochrome c, caspase-9, caspase-3, Bax, reactive oxygen species, and nitric oxide along with inhibition of HSP-70 and Bcl2, which regulate tumor cell survival and apoptosis. SITS-treated DL cells displayed upregulated production of IFN-γ and IL-6 along with a decline of IL-10. Treatment of DL cells with SITS also inhibited the expression of fatty acid synthase, which is crucial for membrane biogenesis in neoplastic cells. The expression of lactate transporter MCT-1 and multidrug resistance regulating protein MRP-1 got inhibited along with hampered uptake of glucose and lactate production in SITS-treated DL cells. Thus, the declined tumor cell survival following inhibition of BCT could be the consequence of interplay of several inter-connected regulatory molecular events. The outcome of this study indicates the potential of BCT inhibition as a novel therapeutic approach for treatment of hematological malignancies.

Janus-faced tumor microenvironment and redox

SIGNIFICANCE

Tumor microenvironment (TME) is a complex term that includes extracellular matrix, blood vessels, endothelial, stromal, and inflammatory cells, and other supporting structures of the particular organ; and physiological components such as oxygen, pH, nutrients, waste products, signaling molecules, reducing/oxidizing species, growth factors, protumorigenic factors, etc. TME is now widely recognized as a major contributor to cancer aggression and treatment resistance and as a potential target for therapeutic intervention.

RECENT ADVANCES

Among important physiological parameters of the TME, tissue hypoxia is considered to be a consequence of imbalanced angiogenesis and is associated with changes in metabolic pathways, including a higher dependence on glycolysis resulting in tissue acidosis. Both hypoxia and acidosis affect the tissue redox status and its key intracellular component, glutathione (GSH). Numerous publications support that these local TME conditions select for outgrowth of cells with appropriate phenotypes, which can reflect underlying genetics.

CRITICAL ISSUES

Here, we hypothesize that specific patterns of local TME, namely, tumor oxygenation, extracellular pH, redox, and GSH homeostasis, acting in orchestrated mechanism, can promote cancer cell survival, while at the same time being highly toxic and mutagenic for normal cells, thus contributing to the growth of cancers at the expense of the normal tissues they are invading. This review summarizes the experimental observations that support the hypothesized Janus-faced character of the redox axis.

FUTURE DIRECTIONS

Normalizing the TME redox parameters may decrease the selection pressure for malignant phenotypes, therefore providing a tool for TME-targeted anticancer therapy.

Tumor growth retardation and chemosensitizing action of fatty acid synthase inhibitor orlistat on T cell lymphoma: implication of reconstituted tumor microenvironment and multidrug resistance phenotype

BACKGROUND

Orlistat, a fatty acid synthase (FASN) inhibitor, has been demonstrated to inhibit tumor cell survival. However, the mechanism(s) of its tumor growth retarding action against malignancies of hematological origin remains unclear. It is also not understood if the antitumor action of orlistat implicates modulated susceptibility of tumor cell to anticancer drugs. Therefore, the present investigation focuses to study the antitumor and chemosensitizing action of orlistat in a murine host bearing a progressively growing T cell lymphoma.

METHODS

Tumor-bearing mice were administered with vehicle alone or containing orlistat followed by administration of PBS with or without cisplatin. Tumor progression and survival of tumor-bearing host were monitored along with analysis of tumor cell survival and apoptosis. Tumor ascitic fluid was examined for pH, NO and cytokines. Expression of genes and proteins was investigated by RT-PCR and western blot respectively. ROS was analyzed by DCFDA staining and FASN activity by spectrophotometry.

RESULTS

Orlistat administration to tumor-bearing mice resulted in tumor growth retardation, prolonged life span, declined tumor cell survival and chemosensitization to cisplatin. It was accompanied by increased osmotic fragility, modulated acidosis, expression of ROS, NO, cytokines, MCT-1 and VH(+) ATPase, Bcl2, Caspase-3, P53, inhibited FASN activity and declined expression of MDR and MRP-1 proteins.

CONCLUSION

Orlistat manifests antitumor and chemosensitizing action implicating modulated regulation of cell survival, reconstituted-tumor microenvironment and altered MDR phenotype.

GENERAL SIGNIFICANCE

These observations indicate that orlistat could be utilized as an adjunct regimen for improving antitumor efficacy of cisplatin.

Novel molecular mechanisms of antitumor action of dichloroacetate against T cell lymphoma: Implication of altered glucose metabolism, pH homeostasis and cell survival regulation

Pyruvate dehydrogenase kinase (PDK) inhibits pyruvate dehydrogenase (PDH) activity and thus promotes energetic switch from mitochondrial glucose oxidation to cytoplasmic glycolysis in cancerous cells (a phenomenon known as the 'Warburg effect') for their energy need, which facilitates the cancer progression by resisting induction of apoptosis and promoting tumor metastasis. Thus, in the present investigation, we explored the molecular mechanisms of the tumoricidal action of dichloroacetate (DCA), a pyruvate dehydrogenase kinase inhibitor, on cells of a murine T cell lymphoma, designated as Dalton's lymphoma (DL). In vitro treatment of tumor cells with DCA inhibited their survival accompanied by a modulation of the biophysical composition of tumor-conditioned medium with respect to pH, glucose and lactate. DCA treatment also altered expression of HIF1-α and pH regulators: VATPase and MCT1 and production of cytokines: IL-10, IL-6 and IFN-γ. Moreover, we also observed an alteration in the expression of other apoptosis and cell survival regulatory molecules: PUMA, GLUT1, Bcl2, p53, CAD, caspase-3 and HSP70. The study discusses the role of novel molecular mechanisms underlying DCA-dependent inhibition of tumor cell survival. This study shows for the first time that DCA-dependent alteration of tumor cell survival involves altered pH homeostasis and glucose metabolism. Thus, these findings will provide a new insight for therapeutic applications of DCA as a novel antineoplastic agent against T cell lymphoma.

Gender-specific antitumor action of aspirin in a murine model of a T-cell lymphoma bearing host

Aspirin is an anti-inflammatory drug demonstrated to possess a tremendous anticancer potential. As progression of some tumors is influenced by sex hormones, we investigated if the antineoplastic action of aspirin shows gender dependence. Using a murine model of T-cell lymphoma, the present investigation was undertaken to study if the antitumor actions of aspirin against lymphoma cells display gender dimorphism. The findings of the present investigation indicate that aspirin administration to male and female tumor-bearing hosts resulted in gender dependent differential tumor growth retardation. Such gender dichotomy of aspirin's antitumor action was associated with a differential impact on cell cycle progression and expression of cell survival regulatory molecules. Aspirin administration was also found to modulate crucial parameters of tumor microenvironment, including contents of glucose, lactate and cell growth regulatory cytokines, in a gender specific manner. Aspirin was found to reverse estrogen-dependent augmentation of tumor cell survival in vitro. Taken together the results of the present study suggest that the antineoplastic action of aspirin is gender-dependent and should be considered in designing of gender-specific therapeutic applications of aspirin.

Anti-neoplastic action of aspirin against a T-cell lymphoma involves an alteration in the tumour microenvironment and regulation of tumour cell survival

The present study explores the potential of the anti-neoplastic action of aspirin in a transplantable murine tumour model of a spontaneously originated T-cell lymphoma designated as Dalton's lymphoma. The antitumour action of aspirin administered to tumour-bearing mice through oral and/or intraperitoneal (intratumoral) routes was measured via estimation of survival of tumour-bearing mice, tumour cell viability, tumour progression and changes in the tumour microenvironment. Intratumour administration of aspirin examined to assess its therapeutic potential resulted in retardation of tumour progression in tumour-bearing mice. Oral administration of aspirin to mice as a prophylactic measure prior to tumour transplantation further primed the anti-neoplastic action of aspirin administered at the tumour site. The anti-neoplastic action of aspirin was associated with a decline in tumour cell survival, augmented induction of apoptosis and nuclear shrinkage. Tumour cells of aspirin-treated mice were found arrested in G0/G1 phase of the cell cycle and showed nuclear localization of cyclin B1. Intratumoral administration of aspirin was accompanied by alterations in the biophysical, biochemical and immunological composition of the tumour microenvironment with respect to pH, level of dissolved O2, glucose, lactate, nitric oxide, IFNγ (interferon γ), IL-4 (interleukin-4), IL-6 and IL-10, whereas the TGF-β (tumour growth factor-β) level was unaltered. Tumour cells obtained from aspirin-treated tumour-bearing mice demonstrated an altered expression of pH regulators monocarboxylate transporter-1 and V-ATPase along with alteration in the level of cell survival regulatory molecules such as survivin, vascular endothelial growth factor, heat-shock protein 70, glucose transporter-1, SOCS-5 (suppressor of cytokine signalling-5), HIF-1α (hypoxia-inducible factor-1α) and PUMA (p53 up-regulated modulator of apoptosis). The study demonstrates a possible indirect involvement of the tumour microenvironment in addition to a direct but limited anti-neoplastic action of aspirin in the retardation of tumour growth.