Revisiting prostate cancer metabolism: From metabolites to disease and therapy.

Prostate cancer (PCa), one of the most commonly diagnosed cancers worldwide, still presents important unmet clinical needs concerning treatment. In the last years, the metabolic reprogramming and the specificities of tumor cells emerged as an exciting field for cancer therapy. The unique features of PCa cells metabolism, and the activation of specific metabolic pathways, propelled the use of metabolic inhibitors for treatment. The present work revises the knowledge of PCa metabolism and the metabolic alterations that underlie the development and progression of the disease. A focus is given to the role of bioenergetic sources, namely, glucose, lipids, and glutamine sustaining PCa cell survival and growth. Moreover, it is described as the action of oncogenes/tumor suppressors and sex steroid hormones in the metabolic reprogramming of PCa. Finally, the status of PCa treatment based on the inhibition of metabolic pathways is presented. Globally, this review updates the landscape of PCa metabolism, highlighting the critical metabolic alterations that could have a clinical and therapeutic interest.

Targeting the Stromal Pro-Tumoral Hyaluronan-CD44 Pathway in Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies. Present-day treatments have not shown real improvements in reducing the high mortality rate and the short survival of the disease. The average survival is less than 5% after 5 years. New innovative treatments are necessary to curtail the situation. The very dense pancreatic cancer stroma is a barrier that impedes the access of chemotherapeutic drugs and at the same time establishes a pro-proliferative symbiosis with the tumor, thus targeting the stroma has been suggested by many authors. No ideal drug or drug combination for this targeting has been found as yet. With this goal in mind, here we have explored a different complementary treatment based on abundant previous publications on repurposed drugs. The cell surface protein CD44 is the main receptor for hyaluronan binding. Many malignant tumors show over-expression/over-activity of both. This is particularly significant in pancreatic cancer. The independent inhibition of hyaluronan-producing cells, hyaluronan synthesis, and/or CD44 expression, has been found to decrease the tumor cell's proliferation, motility, invasion, and metastatic abilities. Targeting the hyaluronan-CD44 pathway seems to have been bypassed by conventional mainstream oncological practice. There are existing drugs that decrease the activity/expression of hyaluronan and CD44: 4-methylumbelliferone and bromelain respectively. Some drugs inhibit hyaluronan-producing cells such as pirfenidone. The association of these three drugs has never been tested either in the laboratory or in the clinical setting. We present a hypothesis, sustained by hard experimental evidence, suggesting that the simultaneous use of these nontoxic drugs can achieve synergistic or added effects in reducing invasion and metastatic potential, in PDAC. A non-toxic, low-cost scheme for inhibiting this pathway may offer an additional weapon for treating pancreatic cancer.

Adenosine inhibits human astrocyte proliferation independently of adenosine receptor activation.

Brain adenosine concentrations can reach micromolar concentrations in stressful situations such as stroke, neurodegenerative diseases or hypoxic regions of brain tumours. Adenosine can act by receptor-independent mechanism by reversing the reaction catalysed by S-adenosylhomocysteine (SAH) hydrolase, leading to SAH accumulation and inhibition of S-adenosylmethionine (SAM)-dependent methyltransferases. Astrocytes are essential in maintaining brain homeostasis but their pathological activation and uncontrolled proliferation plays a role in neurodegeneration and glioma. Adenosine can affect cell proliferation, but the effect of increased adenosine concentration on proliferation of astrocytes is not clarified and was addressed in present work. Human astrocytes (HA) were treated for 3 days with test drugs. Cell proliferation/viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium assay and by cell counting. Cell death was evaluated by assessing lactate dehydrogenase release and by western blot analysis of αII-Spectrin cleavage. 30 µM-Adenosine caused a 40% ± 3% (p < .05, n = 5) reduction in cell proliferation/viability, an effect reversed by 2U/ml-adenosine deaminase, but unchanged in the presence of antagonists of any of the adenosine receptors. Adenosine alone did not induce cell death. 100 µM-Homocysteine alone caused 16% ± 3% (p < .05) decrease in HA proliferation. Combined action of adenosine and homocysteine decreased HA proliferation by 76% ± 4%, an effect higher (p < .05) than the sum of the effects of adenosine and homocysteine alone (56% ± 5%). The inhibitory effect of adenosine on HA proliferation/viability was mimicked by two adenosine kinase inhibitors and attenuated in the presence of folate (100 µM) or SAM (50-100 µM). The results suggest that adenosine reduces HA proliferation by a receptor-independent mechanism probably involving reversal of SAH hydrolase-catalysed reaction.

The Pros and Cons of Estrogens in Prostate Cancer: An Update with a Focus on Phytoestrogens.

The role of estrogens in prostate cancer (PCa) is shrouded in mystery, with its actions going from angelic to devilish. The findings by Huggins and Hodges establishing PCa as a hormone-sensitive cancer have provided the basis for using estrogens in therapy. However, despite the clinical efficacy in suppressing tumor growth and the panoply of experimental evidence describing its anticarcinogenic effects, estrogens were abolished from PCa treatment because of the adverse secondary effects. Notwithstanding, research work over the years has continued investigating the effects of estrogens, reporting their pros and cons in prostate carcinogenesis. In contrast with the beneficial therapeutic effects, many reports have implicated estrogens in the disruption of prostate cell fate and tissue homeostasis. On the other hand, epidemiological data demonstrating the lower incidence of PCa in Eastern countries associated with a higher consumption of phytoestrogens support the beneficial role of estrogens in counteracting cancer development. Many studies have investigated the effects of phytoestrogens and the underlying mechanisms of action, which may contribute to developing safe estrogen-based anti-PCa therapies. This review compiles the existing data on the anti- and protumorigenic actions of estrogens and summarizes the anticancer effects of several phytoestrogens, highlighting their promising features in PCa treatment.

Tumor Microenvironment Modulates Invadopodia Activity of Non-Selected and Acid-Selected Pancreatic Cancer Cells and Its Sensitivity to Gemcitabine and C18-Gemcitabine.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with high mortality due to early metastatic dissemination and high chemoresistance. All these factors are favored by its extracellular matrix (ECM)-rich microenvironment, which is also highly hypoxic and acidic. Gemcitabine (GEM) is still the first-line therapy in PDAC. However, it is quickly deaminated to its inactive metabolite. Several GEM prodrugs have emerged to improve its cytotoxicity. Here, we analyzed how the acidic/hypoxic tumor microenvironment (TME) affects the response of PDAC cell death and invadopodia-mediated ECM proteolysis to both GEM and its C18 prodrug. METHODS: For this, two PDAC cell lines, PANC-1 and Mia PaCa-2 were adapted to pHe 6.6 or not for 1 month, grown as 3D organotypic cultures and exposed to either GEM or C18 in the presence and absence of acidosis and the hypoxia inducer, deferoxamine. RESULTS: We found that C18 has higher cytotoxic and anti-invadopodia activity than GEM in all culture conditions and especially in acid and hypoxic environments. CONCLUSIONS: We propose C18 as a more effective approach to conventional GEM in developing new therapeutic strategies overcoming PDAC chemoresistance.

Increased demand for FAD synthesis in differentiated and stem pancreatic cancer cells is accomplished by modulating FLAD1 gene expression: the inhibitory effect of Chicago Sky Blue.

FLAD1, along with its FAD synthase (FADS, EC 2.7.7.2) product, is crucial for flavin homeostasis and, due to its role in the mitochondrial respiratory chain and nuclear epigenetics, is closely related to cellular metabolism. Therefore, it is not surprising that it could be correlated with cancer. To our knowledge, no previous study has investigated FLAD1 prognostic significance in pancreatic ductal adenocarcinoma (PDAC). Thus, in the present work, the FAD synthesis process was evaluated in two PDAC cell lines: (a) PANC-1- and PANC-1-derived cancer stem cells (CSCs), presenting the R273H mutation in the oncosuppressor p53, and (b) MiaPaca2 and MiaPaca2-derived CSCs, presenting the R248W mutation in p53. As a control, HPDE cells expressing wt-p53 were used. FADS expression/activity increase was found with malignancy and even more with stemness. An increased FAD synthesis rate in cancer cell lines is presumably demanded by the increase in the FAD-dependent lysine demethylase 1 protein amount as well as by the increased expression levels of the flavoprotein subunit of complex II of the mitochondrial respiratory chain, namely succinate dehydrogenase. With the aim of proposing FADS as a novel target for cancer therapy, the inhibitory effect of Chicago Sky Blue on FADS enzymatic activity was tested on the recombinant 6His-hFADS2 (IC50 = 1.2 µm) and PANC-1-derived CSCs' lysate (IC50 = 2-10 µm). This molecule was found effective in inhibiting the growth of PANC-1 and even more of its derived CSC line, thus assessing its role as a potential chemotherapeutic drug.

Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma: A Physiopathologic and Pharmacologic Review.

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a poor prognosis and inadequate response to treatment. Many factors contribute to this therapeutic failure: lack of symptoms until the tumor reaches an advanced stage, leading to late diagnosis; early lymphatic and hematic spread; advanced age of patients; important development of a pro-tumoral and hyperfibrotic stroma; high genetic and metabolic heterogeneity; poor vascular supply; a highly acidic matrix; extreme hypoxia; and early development of resistance to the available therapeutic options. In most cases, the disease is silent for a long time, andwhen it does become symptomatic, it is too late for ablative surgery; this is one of the major reasons explaining the short survival associated with the disease. Even when surgery is possible, relapsesare frequent, andthe causes of this devastating picture are the low efficacy ofand early resistance to all known chemotherapeutic treatments. Thus, it is imperative to analyze the roots of this resistance in order to improve the benefits of therapy. PDAC chemoresistance is the final product of different, but to some extent, interconnected factors. Surgery, being the most adequate treatment for pancreatic cancer and the only one that in a few selected cases can achieve longer survival, is only possible in less than 20% of patients. Thus, the treatment burden relies on chemotherapy in mostcases. While the FOLFIRINOX scheme has a slightly longer overall survival, it also produces many more adverse eventsso that gemcitabine is still considered the first choice for treatment, especially in combination with other compounds/agents. This review discusses the multiple causes of gemcitabine resistance in PDAC.

Androgens and low density lipoprotein-cholesterol interplay in modulating prostate cancer cell fate and metabolism.

BACKGROUND: Androgens, the known drivers of prostate cancer (PCa), have been indicated as important metabolic regulators with a relevant role in stimulating lipid metabolism. Also, the relationship between obesity and the aggressiveness of PCa has been established. However, it is unknown if the androgenic hormonal environment may alter the response of PCa cells to lipid availability. PURPOSE: The present study evaluated the effect of 5α-dihydrotestosterone (DHT) in regulating lipid metabolism, and the interplay between this hormone and low-density lipoprotein (LDL)-cholesterol in modulating PCa cells fate. METHODS: Non-neoplastic and neoplastic PCa cells were treated with 10 nM DHT, and the expression of fatty acids transporter, fatty acid synthase (FASN), and carnitine palmitoyltransferase 1A (CPT1A) evaluated. PCa cells were also exposed to LDL (100 µg/ml) in the presence or absence of DHT. RESULTS: Treatment with DHT upregulated the expression of FASN and CPT1A in androgen-sensitive PCa cells. In contrast, LDL supplementation suppressed FASN expression regardless of the presence of DHT, whereas augmenting CPT1A levels. Our results also showed that LDL-cholesterol increased PCa cells viability, proliferation, and migration dependently on the presence of DHT. Moreover, LDL and DHT synergistically enhanced the accumulation of lipid droplets in PCa cells. CONCLUSIONS: The obtained results show that androgens deregulate lipid metabolism and enhance the effects of LDL increasing PCa cells viability, proliferation and migration. The present findings support clinical data linking obesity with PCa and first implicate androgens in this relationship. Also, they sustain the application of pharmacological approaches targeting cholesterol availability and androgens signaling simultaneously.

Cancer Associated Fibroblast (CAF) Regulation of PDAC Parenchymal (CPC) and CSC Phenotypes Is Modulated by ECM Composition.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest of all cancers, having one of the lowest five-year survival rates. One of its hallmarks is a dense desmoplastic stroma consisting in the abnormal accumulation of extracellular matrix (ECM) components, especially Collagen I. This highly fibrotic stroma embeds the bulk cancer (parenchymal) cells (CPCs), cancer stem cells (CSCs) and the main producers of the stromal reaction, the Cancer Associated Fibroblasts (CAFs). Little is known about the role of the acellular ECM in the interplay of the CAFs with the different tumor cell types in determining their phenotypic plasticity and eventual cell fate. METHODS: Here, we analyzed the role of ECM collagen I in modulating the effect of CAF-derived signals by incubating PDAC CPCs and CSCs grown on ECM mimicking early (low collagen I levels) and late (high collagen I levels) stage PDAC stroma with conditioned medium from primary cultured CAFs derived from patients with PDAC in a previously described three-dimensional (3D) organotypic model of PDAC. RESULTS: We found that CAFs (1) reduced CPC growth while favoring CSC growth independently of the ECM; (2) increased the invasive capacity of only CPCs on the ECM mimicking the early tumor; and (3) favored vasculogenic mimicry (VM) especially of the CSCs on the ECM mimicking an early tumor. CONCLUSIONS: We conclude that the CAFs and acellular stromal components interact to modulate the tumor behaviors of the PDAC CPC and CSC cell types and drive metastatic progression by stimulating the phenotypic characteristics of each tumor cell type that contribute to metastasis.

Role of pH in Regulating Cancer Pyrimidine Synthesis.

Replication is a fundamental aspect of cancer, and replication is about reproducing all the elements and structures that form a cell. Among them are DNA, RNA, enzymes, and coenzymes. All the DNA is doubled during each S (synthesis) cell cycle phase. This means that six billion nucleic acids must be synthesized in each cycle. Tumor growth, proliferation, and mutations all depend on this synthesis. Cancer cells require a constant supply of nucleotides and other macromolecules. For this reason, they must stimulate de novo nucleotide synthesis to support nucleic acid provision. When deregulated, de novo nucleic acid synthesis is controlled by oncogenes and tumor suppressor genes that enable increased synthesis and cell proliferation. Furthermore, cell duplication must be achieved swiftly (in a few hours) and in the midst of a nutrient-depleted and hypoxic environment. This also means that the enzymes participating in nucleic acid synthesis must work efficiently. pH is a critical factor in enzymatic efficiency and speed. This review will show that the enzymatic machinery working in nucleic acid synthesis requires a pH on the alkaline side in most cases. This coincides with many other pro-tumoral factors, such as the glycolytic phenotype, benefiting from an increased intracellular pH. An increased intracellular pH is a perfect milieu for high de novo nucleic acid production through optimal enzymatic performance.

Tumor Microenvironment Features and Chemoresistance in Pancreatic Ductal Adenocarcinoma: Insights into Targeting Physicochemical Barriers and Metabolism as Therapeutic Approaches.

Currently, the median overall survival of PDAC patients rarely exceeds 1 year and has an overall 5-year survival rate of about 9%. These numbers are anticipated to worsen in the future due to the lack of understanding of the factors involved in its strong chemoresistance. Chemotherapy remains the only treatment option for most PDAC patients; however, the available therapeutic strategies are insufficient. The factors involved in chemoresistance include the development of a desmoplastic stroma which reprograms cellular metabolism, and both contribute to an impaired response to therapy. PDAC stroma is composed of immune cells, endothelial cells, and cancer-associated fibroblasts embedded in a prominent, dense extracellular matrix associated with areas of hypoxia and acidic extracellular pH. While multiple gene mutations are involved in PDAC initiation, this desmoplastic stroma plays an important role in driving progression, metastasis, and chemoresistance. Elucidating the mechanisms underlying PDAC resistance are a prerequisite for designing novel approaches to increase patient survival. In this review, we provide an overview of the stromal features and how they contribute to the chemoresistance in PDAC treatment. By highlighting new paradigms in the role of the stromal compartment in PDAC therapy, we hope to stimulate new concepts aimed at improving patient outcomes.

Glutaminolysis is a metabolic route essential for survival and growth of prostate cancer cells and a target of 5α-dihydrotestosterone regulation.

PURPOSE: Resistance to androgen-deprivation therapies and progression to so-called castrate-resistant prostate cancer (CRPC) remain challenges in prostate cancer (PCa) management and treatment. Among other alterations, CRPC has been associated with metabolic reprogramming driven by androgens. Here, we investigated the role of androgens in regulating glutaminolysis in PCa cells and determined the relevance of this metabolic route in controlling the survival and growth of androgen-sensitive (LNCaP) and CRPC (DU145 and PC3) cells. METHODS: PCa cells (LNCaP, DU145 and PC3) and 3-month old rats were treated with 5α-dihydrotestosterone (DHT). Alternatively, LNCaP cells were exposed to the glutaminase inhibitor BPTES, alone or in combination with the anti-androgen bicalutamide. Biochemical, Western blot and extracellular flux assays were used to evaluate the viability, proliferation, migration and metabolism of PCa cells in response to DHT treatment or glutaminase inhibition. RESULTS: We found that DHT up-regulated the expression of the glutamine transporter ASCT2 and glutaminase, both in vitro in LNCaP cells and in vivo in rat prostate cells. BPTES diminished the viability and migration of PCa cells, while increasing caspase-3 activity. CRPC cells were found to be more dependent on glutamine and more sensitive to glutaminase inhibition. BPTES and bicalutamide co-treatment had an additive effect on suppressing LNCaP cell viability. Finally, we found that inhibition of glutaminolysis differentially affected glycolysis and lipid metabolism in both androgen-sensitive and CRPC cells. CONCLUSION: Our data reveal glutaminolysis as a central metabolic route controlling PCa cell fate and highlight the relevance of targeting glutaminase for CRPC treatment.

Adenosine Inhibits Cell Proliferation Differently in Human Astrocytes and in Glioblastoma Cell Lines.

Glioblastoma (GBM) is the most common brain primary tumour. Hypoxic regions in GBM are associated to tumour growth. Adenosine accumulates in hypoxic regions and can affect cell proliferation and survival. However, how proliferating GBM cells respond/adapt to increased adenosine levels compared to human astrocytes (HA) is not clarified and was addressed in the present work. GBM cell lines and HA were treated for 3 days with test drugs. Thirty Adenosine (30 µM) caused a 43% ± 5% (P < 0.05) reduction of cell proliferation/viability in HA, through an adenosine receptor-independent mechanism, but had no effect in GBM cell lines U87MG, U373MG and SNB19. Contrastingly, inhibition of adenosine phosphorylation (using the adenosine kinase (ADK) inhibitor 5-iodotubercidin (ITU) (25 µM)), produced a strong and similar decrease on cell proliferation in both HA and GBM cells. The effect of adenosine on HA proliferation/viability was potentiated by 100 µM-homocysteine. Combined application of 30 µM-adenosine and 100 µM-homocysteine reduced the cell proliferation/viability in all three GBM cell lines, but this reduction was much lower than that observed in HA. Adenosine alone did not induce cell death, assessed by lactate dehydrogenase (LDH) release, both in HA and GBM cells, but potentiated the cytotoxic effect of homocysteine in HA and in U87MG and U373MG cells. Results show a strong attenuation of adenosine anti-proliferative effect in GBM cells compared to HA, probably resulting from increased adenosine elimination by ADK, suggesting a proliferative-prone adaptation of tumour cells to increased adenosine levels.

Tyrosine kinase inhibitor imatinib modulates the viability and apoptosis of castrate-resistant prostate cancer cells dependently on the glycolytic environment.

AIMS: The tyrosine kinase inhibitor imatinib has been used in prostate cancer treatment with outcomes that did not follow the in vitro findings. The glycolytic environment has been shown to influence the efficacy of anti-cancer drugs. This study aimed to evaluate the effect of imatinib on cell viability, apoptosis, and metabolism in cell line models of castrate-resistant prostate cancer (CRPC) under hyperglycemic and hypoglycemic conditions. MAIN METHODS: DU145 and PC3 CRPC cell lines were exposed to 20 µM imatinib under 5 mM (hypoglycemia) or 30 mM glucose (hyperglycemia) for 48-72 h. Cell viability was assessed by the MTS assay. The expression of apoptosis regulators and glycolytic metabolism-related proteins was analysed by Western blot, and the activity of caspase-3 and lactate dehydrogenase (LDH) was determined spectrophotometrically. Glucose consumption and lactate production were determined using biochemical assays. KEY FINDINGS: Imatinib decreased CRPC cells viability, whereas increasing apoptosis; effects only observed in hyperglycemic conditions. Glucose consumption and lactate production were significantly increased in imatinib-treated DU145 and PC3 cells, and independently of glucose availability. Accordingly, LDH expression and activity were significantly increased in response to imatinib. SIGNIFICANCE: Higher glucose availability improved the effectiveness of imatinib suppressing survival and growth of CRPC cells. It was also shown that imatinib treatment stimulated the glycolytic metabolism of CRPC cells. This study first demonstrated that a glucose-enriched environment intensifies the effect of imatinib, which stimulates the interest for testing this compound into the clinical setting, namely in hyperglycemia conditions (diabetic patients) or in co-administration with inhibitors of glycolytic metabolism.