Extracellular Acidosis Modulates the Expression of Epithelial-Mesenchymal Transition (EMT) Markers and Adhesion of Epithelial and Tumor Cells

A 3D Pancreatic Cancer Model with Integrated Optical Sensors for Noninvasive Metabolism Monitoring and Drug Screening

A distinct feature of pancreatic ductal adenocarcinoma (PDAC) is a prominent tumor microenvironment (TME) with remarkable cellular and spatial heterogeneity that meaningfully impacts disease biology and treatment resistance. The dynamic crosstalk between cancer cells and the dense stromal compartment leads to spatially and temporally heterogeneous metabolic alterations, such as acidic pH that contributes to drug resistance in PDAC. Thus, monitoring the extracellular pH metabolic fluctuations within the TME is crucial to predict and to quantify anticancer drug efficacy. Here, a simple and reliable alginate-based 3D PDAC model embedding ratiometric optical pH sensors and cocultures of tumor (AsPC-1) and stromal cells for simultaneously monitoring metabolic pH variations and quantify drug response is presented. By means of time-lapse confocal laser scanning microscopy (CLSM) coupled with a fully automated computational analysis, the extracellular pH metabolic variations are monitored and quantified over time during drug testing with gemcitabine, folfirinox, and paclitaxel, commonly used in PDAC therapy. In particular, the extracellular acidification is more pronounced after drugs treatment, resulting in increased antitumor effect correlated with apoptotic cell death. These findings highlight the importance of studying the influence of cellular metabolic mechanisms on tumor response to therapy in 3D tumor models, this being crucial for the development of personalized medicine approaches.

The emerging role of lactate in tumor microenvironment and its clinical relevance

In recent years, the significant impact of lactate in the tumor microenvironment has been greatly documented. Acting not only as an energy substance in tumor metabolism, lactate is also an imperative signaling molecule. It plays key roles in metabolic remodeling, protein lactylation, immunosuppression, drug resistance, epigenetics and tumor metastasis, which has a tight relation with cancer patients' poor prognosis. This review illustrates the roles lactate plays in different aspects of tumor progression and drug resistance. From the comprehensive effects that lactate has on tumor metabolism and tumor immunity, the therapeutic targets related to it are expected to bring new hope for cancer therapy.

Role of pH-sensing receptors in colitis

Low pH in the gut is associated with severe inflammation, fibrosis, and colorectal cancer (CRC) and is a hallmark of active inflammatory bowel disease (IBD). Subsequently, pH-sensing mechanisms are of interest for the understanding of IBD pathophysiology. Tissue hypoxia and acidosis-two contributing factors to disease pathophysiology-are linked to IBD, and understanding their interplay is highly relevant for the development of new therapeutic options. One member of the proton-sensing G protein-coupled receptor (GPCR) family, GPR65 (T-cell death-associated gene 8, TDAG8), was identified as a susceptibility gene for IBD in a large genome-wide association study. In response to acidic extracellular pH, GPR65 induces an anti-inflammatory response, whereas the two other proton-sensing receptors, GPR4 and GPR68 (ovarian cancer G protein-coupled receptor 1, OGR1), mediate pro-inflammatory responses. Here, we review the current knowledge on the role of these proton-sensing receptors in IBD and IBD-associated fibrosis and cancer, as well as colitis-associated cancer (CAC). We also describe emerging small molecule modulators of these receptors as therapeutic opportunities for the treatment of IBD.

In Situ Insonation of Alkaline Buffer Containing Liposomes Leads to a Net Improvement of the Therapeutic Outcome in a Triple Negative Breast Cancer Murine Model

Breast cancer is characterized by an acidic micro-environment. Acidic extracellular pH gives cancer cells an evolutionary advantage, hence, neutralization of the extracellular pH has been considered as a potential therapeutic strategy. To address the issue of systemic pH alteration, an approach based on the targeted delivery of the buffering solution to the tumor region is investigated. The method relies on the use of low frequency ultrasound and sono-sensitive liposomes loaded with buffers at alkaline pH (LipHUS). After the i.v. injection of LipHUS, the application of ultrasound (US) at the sites of the pathology induces a local increase of pH that results highly effective in i) inhibiting primary tumor growth, ii) reducing tumor recurrence after surgery, and iii) suppressing metastases' formation. The experiments are carried out on a triple negative breast cancer mouse model. The results obtained demonstrate that localized and triggered release of bicarbonate or PBS buffer from sonosensitive liposomes represents an efficient therapeutic tool for treating triple-negative breast cancer. This approach holds promise for potential clinical translation.

PFKFB2 is a favorable prognostic biomarker for colorectal cancer by suppressing metastasis and tumor glycolysis

PURPOSE

This study was to investigate the biological effect of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2) in colorectal cancer (CRC).

METHODS

PFKFB2 was selected by metabolism polymerase chain reaction (PCR) array from CRC cells under alkaline culture medium (pH 7.4) and acidic culture medium (pH 6.8). The expression of PFKFB2 mRNA and protein was detected by quantitative real-time PCR and immunohistochemistry in 70 paired fresh and 268 paired paraffin-embedded human CRC tissues, respectively, and then the prognostic value of PFKFB2 was investigated. The effects of PFKFB2 on CRC cells were also verified in vitro, which were through detecting the change of migration, invasion, sphere formation, proliferation, colony formation, and extracellular acidification rate of CRC cells after PFKFB2 knockdown in alkaline culture medium (pH 7.4) and overexpression in acidic culture medium (pH 6.8).

RESULTS

PFKFB2 expression was downregulated in acidic culture medium (pH 6.8). In addition, we found PFKFB2 expression decreased in human CRC tissues compared with the adjacent normal tissues. Furthermore, the OS and DFS rate of CRC patients with low PFKFB2 expression was significantly shorter than those of patients with high PFKFB2 expression. Multivariate analysis indicated that low PFKFB2 expression was an independent prognostic factor for both OS and DFS in CRC patients. Moreover, the abilities of migration, invasion, spheroidizing ability, proliferation, and colony formation of CRC cells were significantly increased after depletion of PFKFB2 in alkaline culture medium (pH 7.4) and decreased after overexpression of PFKFB2 in acidic culture medium (pH 6.8) in vitro. Epithelial-mesenchymal transition (EMT) pathway was found and verified involved in the PFKFB2-mediated regulation of metastatic function in CRC cells. Further, glycolysis of CRC cells was significantly elevated after knockdown of PFKFB2 in alkaline culture medium (pH 7.4) and decreased after overexpression of PFKFB2 in acidic culture medium (pH 6.8).

CONCLUSION

PFKFB2 expression is downregulated in CRC tissues and associated with worse survival for CRC patients. PFKFB2 could inhibit metastasis and the malignant progression of CRC cells by suppressing EMT and glycolysis.

Acidic Growth Conditions Promote Epithelial-to-Mesenchymal Transition to Select More Aggressive PDAC Cell Phenotypes In Vitro

Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an acidic microenvironment, which contributes to therapeutic failure. So far there is a lack of knowledge with respect to the role of the acidic microenvironment in the invasive process. This work aimed to study the phenotypic and genetic response of PDAC cells to acidic stress along the different stages of selection. To this end, we subjected the cells to short- and long-term acidic pressure and recovery to pH_e 7.4. This treatment aimed at mimicking PDAC edges and consequent cancer cell escape from the tumor. The impact of acidosis was assessed for cell morphology, proliferation, adhesion, migration, invasion, and epithelial-mesenchymal transition (EMT) via functional in vitro assays and RNA sequencing. Our results indicate that short acidic treatment limits growth, adhesion, invasion, and viability of PDAC cells. As the acid treatment progresses, it selects cancer cells with enhanced migration and invasion abilities induced by EMT, potentiating their metastatic potential when re-exposed to pH_e 7.4. The RNA-seq analysis of PANC-1 cells exposed to short-term acidosis and pH_e-selected recovered to pH_e 7.4 revealed distinct transcriptome rewiring. We describe an enrichment of genes relevant to proliferation, migration, EMT, and invasion in acid-selected cells. Our work clearly demonstrates that upon acidosis stress, PDAC cells acquire more invasive cell phenotypes by promoting EMT and thus paving the way for more aggressive cell phenotypes.

Tumor heterogeneity: An oncogenic driver of PDAC progression and therapy resistance under stress conditions

Pancreatic ductal adenocarcinoma (PDAC) is a clinically challenging disease usually diagnosed at advanced or metastasized stage. By this year end, there are an expected increase in 62,210 new cases and 49,830 deaths in the United States, with 90% corresponding to PDAC subtype alone. Despite advances in cancer therapy, one of the major challenges combating PDAC remains tumor heterogeneity between PDAC patients and within the primary and metastatic lesions of the same patient. This review describes the PDAC subtypes based on the genomic, transcriptional, epigenetic, and metabolic signatures observed among patients and within individual tumors. Recent studies in tumor biology suggest PDAC heterogeneity as a major driver of disease progression under conditions of stress including hypoxia and nutrient deprivation, leading to metabolic reprogramming. We therefore advance our understanding in identifying the underlying mechanisms that interfere with the crosstalk between the extracellular matrix components and tumor cells that define the mechanics of tumor growth and metastasis. The bilateral interaction between the heterogeneous tumor microenvironment and PDAC cells serves as another important contributor that characterizes the tumor-promoting or tumor-suppressing phenotypes providing an opportunity for an effective treatment regime. Furthermore, we highlight the dynamic reciprocating interplay between the stromal and immune cells that impact immune surveillance or immune evasion response and contribute towards a complex process of tumorigenesis. In summary, the review encapsulates the existing knowledge of the currently applied treatments for PDAC with emphasis on tumor heterogeneity, manifesting at multiple levels, impacting disease progression and therapy resistance under stress.

Targeting autophagy and lipid metabolism in cancer stem cells

Cancer stem cells (CSCs) are a subset of cancer cells with self-renewal ability and tumor initiating properties. Unlike the other non-stem cancer cells, CSCs resist traditional therapy and remain a major cause of disease relapse. With the recent advances in metabolomics, various studies have demonstrated that CSCs have distinct metabolic properties. Metabolic reprogramming in CSCs contributes to self-renewal and maintenance of stemness. Accumulating evidence suggests that rewiring of energy metabolism is a key player that enables to meet energy demands, maintains stemness, and sustains cancer growth and invasion. CSCs use various mechanisms such as increased glycolysis, redox signaling and autophagy modulation to overcome nutritional deficiency and sustain cell survival. The alterations in lipid metabolism acquired by the CSCs support biomass production through increased dependence on fatty acid synthesis and β-oxidation and contribute to oncogenic signaling pathways. This review summarizes our current understanding of lipid metabolism in CSCs and how pharmacological regulation of autophagy and lipid metabolism influences CSC phenotype. Increased dependence on lipid metabolism appears as an attractive strategy to eliminate CSCs using therapeutic agents that specifically target CSCs based on their modulation of lipid metabolism.

Peritumoral scaffold neutralizes tumor pH for chemotherapy sensitization and metastasis inhibition

The abnormal metabolism of rapidly growing tumors can create an acidic tumor microenvironment (TME) that renders cancer cells resistant to chemotherapy and further facilitates endothelial-to-mesenchymal transition (EMT) progress to promote metastasis. Here, we developed a combination strategy consisting of (1) peritumorally injected scaffold that alleviates TME acidosis, and (2) intravenously injected nanoparticles that delivers anti-cancer agents to tumor. Concurrent treatment with these two drug delivery systems profoundly delayed the growth of primary tumor and reduced the spontaneous metastasis to lung in an orthotopic breast cancer mouse model. Mechanism studies both in vitro and in vivo further revealed that neutralization of TME pH by the hydrogel scaffold sensitized cancer cells to nanoparticle-based chemotherapy, thereby strengthening the cytotoxicity against tumor growth; In parallel, reversal of tumor acidity downregulated various pro-metastatic proteins intratumorally to block the EMT progress, thereby reducing the metastatic potential of cancer cells. This work provided proof-of-concept demonstration that chemotherapy sensitization and EMT suppression could be synchronized by the modulation of TME pH, which may be potentially beneficial for simultaneous inhibition of tumor growth and cancer metastasis.

Acidic urine is associated with poor prognosis in patients with bladder cancer undergoing radical cystectomy

Purpose

To assess the prognostic value of acidic urine (low urine pH) in patients with bladder cancer undergoing radical cystectomy.

Materials and methods

We reviewed patients enrolled in the Seoul National University Prospectively Enrolled Registry for Urothelial Cancer-Cystectomy (SUPER-UC-Cx) who underwent radical cystectomy for bladder cancer between March 2016 and December 2020 at the Seoul National University Hospital. During this period, 368 patients were registered in our database. To eliminate confounding factors, we excluded patients diagnosed with non-urothelial cancer and end-stage renal disease.

Results

A total of 351 patients with a mean age of 69.8 ± 10.5 years and median follow-up of 16.0 months were eligible for the analysis. The mean preoperative urine pH was 6.0. The patients were divided into low (pH ≤ 5.5) and high (pH≥6.0) urine pH groups for comparison. All clinicopathological features, including the tumor size, grade, and stage were comparable between the low and high urine pH groups. A Cox regression analysis was performed to assess the independent effect of acidic urine on patient survival. A multivariate analysis showed that high T stage (T3-4) (hazard ratio (HR) 5.18, P<0.001), decreased renal function (estimated glomerular filtration rate <60 mL/min/1.73 m²) (HR 2.29, P=0.003), and low urine pH (≤5.5) (HR 1.69, P=0.05) were associated with shortened recurrence-free survival (RFS). Regarding the overall survival (OS), high T stage (T3-4) (HR 7.15, P<0.001) and low urine pH (≤5.5) (HR 2.66, P=0.029) were significantly associated with shortened survival. A Kaplan–Meier analysis demonstrated that the acidic urine group showed shorter RFS (P=0.04) and OS (P=0.028) than the other groups.

Conclusions

Acidic urine was independently associated with reduced RFS and OS in patients with bladder cancer undergoing radical cystectomy. Acidic urine contributing to an acidic tumor environment may promote aggressive behavior in bladder cancer.

Proton export upregulates aerobic glycolysis

INTRODUCTION

Aggressive cancers commonly ferment glucose to lactic acid at high rates, even in the presence of oxygen. This is known as aerobic glycolysis, or the "Warburg Effect." It is widely assumed that this is a consequence of the upregulation of glycolytic enzymes. Oncogenic drivers can increase the expression of most proteins in the glycolytic pathway, including the terminal step of exporting H+ equivalents from the cytoplasm. Proton exporters maintain an alkaline cytoplasmic pH, which can enhance all glycolytic enzyme activities, even in the absence of oncogene-related expression changes. Based on this observation, we hypothesized that increased uptake and fermentative metabolism of glucose could be driven by the expulsion of H+ equivalents from the cell.

RESULTS

To test this hypothesis, we stably transfected lowly glycolytic MCF-7, U2-OS, and glycolytic HEK293 cells to express proton-exporting systems: either PMA1 (plasma membrane ATPase 1, a yeast H+-ATPase) or CA-IX (carbonic anhydrase 9). The expression of either exporter in vitro enhanced aerobic glycolysis as measured by glucose consumption, lactate production, and extracellular acidification rate. This resulted in an increased intracellular pH, and metabolomic analyses indicated that this was associated with an increased flux of all glycolytic enzymes upstream of pyruvate kinase. These cells also demonstrated increased migratory and invasive phenotypes in vitro, and these were recapitulated in vivo by more aggressive behavior, whereby the acid-producing cells formed higher-grade tumors with higher rates of metastases. Neutralizing tumor acidity with oral buffers reduced the metastatic burden.

CONCLUSIONS

Therefore, cancer cells which increase export of H+ equivalents subsequently increase intracellular alkalization, even without oncogenic driver mutations, and this is sufficient to alter cancer metabolism towards an upregulation of aerobic glycolysis, a Warburg phenotype. Overall, we have shown that the traditional understanding of cancer cells favoring glycolysis and the subsequent extracellular acidification is not always linear. Cells which can, independent of metabolism, acidify through proton exporter activity can sufficiently drive their metabolism towards glycolysis providing an important fitness advantage for survival.

The Role of ASIC1a in Inflammatory Immune Diseases: A Potential Therapeutic Target

It is acknowledged that chronic inflammation is associated with a rise in extracellular proton concentrations. The acid-sensing ion channel 1a (ASIC1a) belongs to the extracellular H⁺-activated cation channel family. Recently, many studies have been conducted on ASIC1a and inflammatory immune diseases. Here, in this review, we will focus on the role of ASIC1a in several inflammatory immune diseases so as to provide new perspectives for clinical treatment.

Interaction between tumor microenvironment, autophagy, and epithelial-mesenchymal transition in tumor progression

Tumor microenvironment (TME) is the ecosystem surrounding a tumor to influence tumor cells' growth, metastasis and immunological battlefield, in which the tumor systems fight against the body system. TME has been considered as the essential link between the tumorigenesis and development of neoplasm. Both nutrients intake and tumor progression to malignancy require the participation of components in TME. Epithelial-mesenchymal transition (EMT) is a key step in the metastasis of tumor cells. Cells that lost polarity and acquired migration ability are prone to metastasize. Autophagy is an important self-protective mechanism in tumor cells and a necessity for the tumor cells to respond to harmful stress. Protective autophagy benefits tumor cells while abnormal autophagy leads to cell injury or death. EMT and autophagy are directly regulated by TME. To date, there are numerous studies on TME, autophagy and EMT separately, but few on their complex interrelationships. This review aims to comprehensively analyze the existing mechanisms and convincing evidence so far to seek novel therapeutic strategies and research directions.

Targeting carbonic anhydrase IX and XII isoforms with small molecule inhibitors and monoclonal antibodies

Carbonic anhydrases IX and CAXII (CAIX/CAXII) are transmembrane zinc metalloproteins that catalyze a very basic but crucial physiological reaction: the conversion of carbon dioxide into bicarbonate with a release of the proton. CA, especially CAIX and CAXII isoforms gained the attention of many researchers interested in anticancer drug design due to pivotal functions of enzymes in the cancer cell metastasis and response to hypoxia, and their expression restricted to malignant cells. This offers an opportunity to develop new targeted therapies with fewer side effects. Continuous efforts led to the discovery of a series of diverse compounds with the most abundant sulphonamide derivatives. Here we review current knowledge considering small molecule and antibody-based targeting of CAIX/CAXII in cancer.

Identification of distinct slow mode of reversible adaptation of pancreatic ductal adenocarcinoma to the prolonged acidic pH microenvironment

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic neoplasm with high metastatic potential and poor clinical outcome. Like other solid tumors, PDAC in the early stages is often asymptomatic, and grows very slowly under a distinct acidic pHe (extracellular pH) microenvironment. However, most previous studies have only reported the fate of cancerous cells upon cursory exposure to acidic pHe conditions. Little is known about how solid tumors-such as the lethal PDAC originating within the pancreatic duct-acinar system that secretes alkaline fluids-evolve to withstand and adapt to the prolonged acidotic microenvironmental stress.

METHODS

Representative PDAC cells were exposed to various biologically relevant periods of extracellular acidity. The time effects of acidic pHe stress were determined with respect to tumor cell proliferation, phenotypic regulation, autophagic control, metabolic plasticity, mitochondrial network dynamics, and metastatic potentials.

RESULTS

Unlike previous short-term analyses, we found that the acidosis-mediated autophagy occurred mainly as an early stress response but not for later adaptation to microenvironmental acidification. Rather, PDAC cells use a distinct and lengthy process of reversible adaptive plasticity centered on the early fast and later slow mitochondrial network dynamics and metabolic adjustment. This regulates their acute responses and chronic adaptations to the acidic pHe microenvironment. A more malignant state with increased migratory and invasive potentials in long-term acidosis-adapted PDAC cells was obtained with key regulatory molecules being closely related to overall patient survival. Finally, the identification of 34 acidic pHe-related genes could be potential targets for the development of diagnosis and treatment against PDAC.

CONCLUSIONS

Our study offers a novel mechanism of early rapid response and late reversible adaptation of PDAC cells to the stress of extracellular acidosis. The presence of this distinctive yet slow mode of machinery fills an important knowledge gap in how solid tumor cells sense, respond, reprogram, and ultimately adapt to the persistent microenvironmental acidification.

Epithelial–Fibroblast Crosstalk Protects against Acidosis-Induced Inflammatory and Fibrotic Alterations

Pathogenesis of chronic kidney disease (CKD) is accompanied by extracellular acidosis inflammation, fibrosis and epithelial-to-mesenchymal transition (EMT). The aim of this study was to assess the influence of acidosis on tubule epithelial cells (NRK-52E) and fibroblasts (NRK-49F) in dependence of cellular crosstalk. NRK-52E and NRK-49F were used in mono- and co-cultures, and were treated with acidic media (pH 6.0) for 48 h. The intracellular proteins were measured by Western blot. Secreted proteins were measured by ELISA. Distribution of E-cadherin was assessed by immunofluorescence and epithelial barrier function by FITC-dextran diffusion. Inflammation: Acidosis led to an increase in COX-2 in NRK-52E and TNF in NRK-49F in monoculture. In co-culture, this effect was reversed. EMT: Acidosis led to an increase in vimentin protein in both cell lines, whereas in co-culture, the effect was abolished. In NRK-52E, the E-cadherin expression was unchanged, but subcellular E-cadherin showed a disturbed distribution, and cellular barrier function was decreased. Fibrosis: Monoculture acidosis led to an increased secretion of collagen I and fibronectin in NRK-52E and collagen I in NRK-49F. In co-culture, the total collagen I secretion was unchanged, and fibronectin secretion was decreased. Intercellular crosstalk between epithelial cells and fibroblasts has a protective function regarding the development of acidosis-induced damage.

Intracellular pH-mediated induction of apoptosis in HeLa cells by a sulfonamide carbonic anhydrase inhibitor

Carbonic anhydrase IX (CAIX) is a hypoxia-associated transmembrane protein that is critical in the survival of cells. Because CAIX has a key role in pH regulation, its therapeutic effects have been heavily studied by different research laboratories. This study aims to investigate how a synthetic CAIX inhibitor triggers apoptosis in a cancer cell line, HeLa. In this regard, we investigated the effects of the compound I, synthesized as a CAIX inhibitor, on the survival of cancer cells. The compound I inhibited the proliferation of the CAIX+ HeLa cells, kept the cells in G0/G1 phase (74.7%) and altered the cells morphologies (AO/EtBr staining) and the nuclear structure (γ-H2AX staining). CAIX inhibition triggered apoptosis in HeLa cells with a rate of 47.4%. According to the expression of mediator genes (CASP-3, -8, -9, BAX, BCL-2, BECLIN, LC3), the both death pathways were activated in HeLa cells with the inhibition of CAIX with the compound I. The compound I was also determined to affect the genes and proteins that have a critical role in the regulation of apoptotic pathways (pro casp-3, cleaved casp-3, -8, -9, cleaved PARP and CAIX). Furthermore, CAIX inhibition caused changes in pH balance, disruption in organelle integrity of mitochondria, and increase intracellular reactive oxygen level of HeLa cells. Taken together, our findings suggest that CAIX inhibition has a potential in cancer treatment, and the compound I, a CAIX inhibitor, could be a promising therapeutic strategy in the treatment of aggressive tumours.

A new era: tumor microenvironment in chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a solid malignant tumor with an extremely poor prognosis. Gemcitabine (GEM)-based chemotherapy remains one of the most important treatment choices for PDAC. However, either as monotherapy or as a part of the combination chemotherapy, GEM achieved only limited success in improving the survival of patients with advanced PDAC, primarily due to GEM resistance. PDAC is characterized by an extensive desmoplasia in the tumor microenvironment (TME). Increasing evidence indicates that this fibrotic TME not only actively participates in the tumor growth and spread of PDAC but also contributes to the induction of GEM resistance. Here we review the current advances of how TME components are involved in the induction of GEM resistance.

Acidic Urine Is Associated With Poor Prognosis of Upper Tract Urothelial Carcinoma

Purpose

To assess the prognostic role of acidic urine (low urine pH) in upper tract urothelial cancer (UTUC).

Materials and Methods

We reviewed patients enrolled in Seoul National University Prospectively Enrolled Registry for Urothelial Cancer-Upper Tract Urothelial Cancer (SUPER-UC-UTUC) who underwent surgical resection from March 2016 to December 2020 in Seoul National University Hospital (SNUH). Patients with non-urothelial cancer or those who are in condition at end-stage renal disease were excluded. Acidic urine was defined as urine pH ≤ 5.5.

Results

A total of 293 patients with a mean age of 70.7 ± 9.5 years were enrolled in this study. Pre-operative laboratory results showed a mean estimated glomerular filtration rate (eGFR) of 64.1 ± 19.2 mL/min/1.73m² and a mean urine pH of 5.86 ± 0.66. Patients were subdivided into low (pH ≤ 5.5) and high (pH > 5.5) urine pH for comparison. As a result, all variables were comparable except for the T stage, which was significantly higher in the low urine pH group (p = 0.017). Cox regression analysis was performed to assess the clinical impact of acidic urine on patient survival. Multivariate Cox regression analysis revealed that tumor multifocality (HR 2.07, p = 0.015), higher T stage (HR 1.54, p = 0.036), lymphovascular invasion (HR 1.69, p = 0.033), eGFR < 60 mL/min per 1.73 m² (HR 1.56, p = 0.017), and acidic urine (HR 1.63, p < 0.01) independently decreased disease-free survival (DFS), while multifocality (HR 9.50, p < 0.01), higher T stage (HR 9.51, p = 0.001) and acidic urine (HR 10.36, p = 0.004) independently reduced the overall survival (OS).

Conclusions

Acidic urine is independently associated with reduced DFS and OS in UTUC. Acidic urine contributing to acidic environment may promote acquisition of agressive behavior of UTUC.

Reprogramming Carbohydrate Metabolism in Cancer and Its Role in Regulating the Tumor Microenvironment

Altered metabolism has become an emerging feature of cancer cells impacting their proliferation and metastatic potential in myriad ways. Proliferating heterogeneous tumor cells are surrounded by other resident or infiltrating cells, along with extracellular matrix proteins, and other secretory factors constituting the tumor microenvironment. The diverse cell types of the tumor microenvironment exhibit different molecular signatures that are regulated at their genetic and epigenetic levels. The cancer cells elicit intricate crosstalks with these supporting cells, exchanging essential metabolites which support their anabolic processes and can promote their survival, proliferation, EMT, angiogenesis, metastasis and even therapeutic resistance. In this context, carbohydrate metabolism ensures constant energy supply being a central axis from which other metabolic and biosynthetic pathways including amino acid and lipid metabolism and pentose phosphate pathway are diverged. In contrast to normal cells, increased glycolytic flux is a distinguishing feature of the highly proliferative cancer cells, which supports them to adapt to a hypoxic environment and also protects them from oxidative stress. Such rewired metabolic properties are often a result of epigenetic alterations in the cancer cells, which are mediated by several factors including, DNA, histone and non-histone protein modifications and non-coding RNAs. Conversely, epigenetic landscapes of the cancer cells are also dictated by their diverse metabolomes. Altogether, this metabolic and epigenetic interplay has immense potential for the development of efficient anti-cancer therapeutic strategies. In this book chapter we emphasize upon the significance of reprogrammed carbohydrate metabolism in regulating the tumor microenvironment and cancer progression, with an aim to explore the different metabolic and epigenetic targets for better cancer treatment.

Characterization of the Safety Profile of Sweet Chestnut Wood Distillate Employed in Agriculture

In organic agriculture, synthetic pesticides and treatments are substituted by natural remedies with interesting success for product yield and environmental outcomes, but the safety of these bio-based products needs to be assessed in vertebrate and human models. Therefore, in this paper we assessed the safety profile of sweet chestnut (Castanea sativa) wood distillate (WD) on the different cellular components of tissues implied in transcutaneous absorption. We investigated the viability of different cell lines mimicking the skin (HaCaT keratinocytes), mucosa (A431), connective (normal human dermal fibroblasts, NHDF) and vascular (human umbilical vein endothelial cells, HUVEC) tissues after exposure to increasing concentrations (0.04–0.5%, v/v, corresponding to 1:2800–1:200 dilutions) of WD. A short exposure to increasing doses of WD was well tolerated up to the highest concentration. Instead, following a prolonged treatment, a concentration dependent cytotoxic effect was observed. Notably, a different behavior was found with the various cell lines, with higher sensitivity to cytotoxicity by the cells with higher proliferation rate and reduced doubling time (human keratinocytes). Moreover, to exclude an inflammatory effect at the not cytotoxic WD concentrations, the expression of the main inducible markers of inflammation, cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1), were assessed, and no improvement was found both after brief and prolonged exposure. In conclusion, our data exclude any inflammatory and cytotoxic effect at the lowest WD concentrations, namely 0.07% and 0.04%, mimicking some recommended dilutions of the product and the potential exposure doses for the operators in agriculture. Nevertheless, higher concentrations showed a safe profile for short time usage, but caution should be used by farmers following persistent product exposure.

A microenvironment of high lactate and low pH created by the blastocyst promotes endometrial receptivity and implantation

RESEARCH QUESTION

Is the blastocyst's idiosyncratic metabolic production of lactate, and creation of a specialized microenvironment at the implatation site, an important mediator of maternal-fetal signalling to promote endometrial receptivity and implantation?

DESIGN

Hormonally primed ECC-1 and Ishikawa cells were used to assess functional changes to the endometrial epithelium after exposure to lactic acid (LA), LA with neutralized pH (nLA) or acidic pH (pH_L). Tight junction integrity (transepithelial resistance [TER]), cellular proliferation or changes to gene expression by RT-PCR were analysed. The effect of LA on Endometrial stromal cells decidualization and migratory capacity, and HUVEC endothelial tube formation and angiogenesis, were also assessed.

RESULTS

Treatment of ECC-1 cells with 2.5 mM (P = 0.0037), 5 mM (P = 0.0044), 7.5 mM and 10 mM (P = 0.003) (P = 0.0021) LA significantly decreased the rate of cellular proliferation while TER was decreased with exposure to 2.5 mM LA (P = 0.024), 5 mM LA (P = 0.021) and 7.5 mM LA (P = 0.033). Exposure to nLA or pH_L had no effect on proliferation or TER. Upregulation of GLUT4 (P = 0.002), GPR81 (P = 0.048), VEGF, SNAI1 (both P < 0.001) and RELA (P = 0.023) mRNA expression was observed after exposure of Ishikawa cells to combined LA plus pH_L. Lactic acid increased the migratory capacity of decidualized stromal cells (P = 0.047) without changing the extent of decidualization. HUVEC tube formation was significantly increased by 5 mM LA exposure (P = 0.009).

CONCLUSIONS

The identification of LA as an important mediator in the maternal-fetal dialogue underpinning implantation is supported. Further examination of the role of LA within the infertile or compromised endometrium could improve natural and assisted pregnancy success and needs further investigation.

Acid-base transporters and pH dynamics in human breast carcinomas predict proliferative activity, metastasis, and survival

Breast cancer heterogeneity in histology and molecular subtype influences metabolic and proliferative activity and hence the acid load on cancer cells. We hypothesized that acid-base transporters and intracellular pH (pH_i) dynamics contribute inter-individual variability in breast cancer aggressiveness and prognosis. We show that Na⁺,HCO₃^- cotransport and Na⁺/H⁺ exchange dominate cellular net acid extrusion in human breast carcinomas. Na⁺/H⁺ exchange elevates pH_i preferentially in estrogen receptor-negative breast carcinomas, whereas Na⁺,HCO₃^- cotransport raises pH_i more in invasive lobular than ductal breast carcinomas and in higher malignancy grade breast cancer. HER2-positive breast carcinomas have elevated protein expression of Na⁺/H⁺ exchanger NHE1/SLC9A1 and Na⁺,HCO₃^- cotransporter NBCn1/SLC4A7. Increased dependency on Na⁺,HCO₃^- cotransport associates with severe breast cancer: enlarged CO₂/HCO₃^--dependent rises in pH_i predict accelerated cell proliferation, whereas enhanced CO₂/HCO₃^--dependent net acid extrusion, elevated NBCn1 protein expression, and reduced NHE1 protein expression predict lymph node metastasis. Accordingly, we observe reduced survival for patients suffering from luminal A or basal-like/triple-negative breast cancer with high SLC4A7 and/or low SLC9A1 mRNA expression. We conclude that the molecular mechanisms of acid-base regulation depend on clinicopathological characteristics of breast cancer patients. NBCn1 expression and dependency on Na⁺,HCO₃^- cotransport for pH_i regulation, measured in biopsies of human primary breast carcinomas, independently predict proliferative activity, lymph node metastasis, and patient survival.

Cancer stem cells, epithelial-mesenchymal transition, ATP and their roles in drug resistance in cancer

The cancer stem cell (CSC) state and epithelial-mesenchymal transition (EMT) activation are tightly interconnected. Cancer cells that acquire the EMT/CSC phenotype are equipped with adaptive metabolic changes to maintain low reactive oxygen species levels and stemness, enhanced drug transporters, anti-apoptotic machinery and DNA repair system. Factors present in the tumor microenvironment such as hypoxia and the communication with non-cancer stromal cells also promote cancer cells to enter the EMT/CSC state and display related resistance. ATP, particularly the high levels of intratumoral extracellular ATP functioning through both signaling pathways and ATP internalization, induces and regulates EMT and CSC. The three of them work together to enhance drug resistance. New findings in each of these factors will help us explore deeper into mechanisms of drug resistance and suggest new resistance-associated markers and therapeutic targets.

Cancer heterogeneity and metastasis: life at the edge

There is abundant evidence that the phenotype of cells the tumor at the stromal interface is distinct from the tumor cells that are within the core. Molecular phenotyping of cells at the edge show that they express higher levels of proteins associated with elevated glycolytic metabolism, including GLUT-1, HIF-1, and CA-IX. An end product of glycolysis is the production of acid, and acidosis of tumors is strongly associated with increased metastatic potential across a wide variety of tumor types. The molecular machinery promoting this export of acid is being defined, with close collaboration between carbonic anhydrases, sodium dependent bicarbonate and monocarboxylate transporters. Neutralization of this acidity can prevent local invasion and metastasis, and this has led to the "acid-mediated invasion hypothesis" wherein export of acid from the tumor into the stroma leads to matrix remodeling, which can promote local invasion.

Advances in research of extracellular mechanisms underlying gemcitabine resistance in pancreatic cancer

Pancreatic cancer is a solid malignant tumor with the worst prognosis worldwide, and about 90% of cases are pancreatic ductal adenocarcinoma (PDAC). Although surgical resection is the only potential way to cure PDAC, the overall survival rate after surgery is still not optimistic. Consequently, gemcitabine (GEM)-based chemotherapy is still one of the most important treatment options for PDAC. However, the survival improvement by GEM monotherapy for advanced PDAC is very limited, and GEM resistance is the key reason. The mechanism underlying gemcitabine resistance is complex and still unclear in PDAC. The extensive and dense fibrous mesenchyme in the tumor microenvironment (TME) is an important feature of PDAC. More and more evidence has shown that TME is not only an active participant in tumor growth and spread, but also a contributor to the induction of GEM resistance. This article will review the recent advances in the understanding of the cellular and molecular mechanisms underlying GEM resistance in PDAC, and discuss potential GEM chemosensitization strategies, in order to improve the effective rate of chemotherapy and the outcome.

Hypoxia-Induced Cancer Cell Responses Driving Radioresistance of Hypoxic Tumors: Approaches to Targeting and Radiosensitizing

Simple Summary

Some regions of aggressive malignancies experience hypoxia due to inadequate blood supply. Cancer cells adapting to hypoxic conditions somehow become more resistant to radiation exposure and this decreases the efficacy of radiotherapy toward hypoxic tumors. The present review article helps clarify two intriguing points: why hypoxia-adapted cancer cells turn out radioresistant and how they can be rendered more radiosensitive. The critical molecular targets associated with intratumoral hypoxia and various approaches are here discussed which may be used for sensitizing hypoxic tumors to radiotherapy.

Abstract

Within aggressive malignancies, there usually are the “hypoxic zones”—poorly vascularized regions where tumor cells undergo oxygen deficiency through inadequate blood supply. Besides, hypoxia may arise in tumors as a result of antiangiogenic therapy or transarterial embolization. Adapting to hypoxia, tumor cells acquire a hypoxia-resistant phenotype with the characteristic alterations in signaling, gene expression and metabolism. Both the lack of oxygen by itself and the hypoxia-responsive phenotypic modulations render tumor cells more radioresistant, so that hypoxic tumors are a serious challenge for radiotherapy. An understanding of causes of the radioresistance of hypoxic tumors would help to develop novel ways for overcoming this challenge. Molecular targets for and various approaches to radiosensitizing hypoxic tumors are considered in the present review. It is here analyzed how the hypoxia-induced cellular responses involving hypoxia-inducible factor-1, heat shock transcription factor 1, heat shock proteins, glucose-regulated proteins, epigenetic regulators, autophagy, energy metabolism reprogramming, epithelial–mesenchymal transition and exosome generation contribute to the radioresistance of hypoxic tumors or may be inhibited for attenuating this radioresistance. The pretreatments with a multitarget inhibition of the cancer cell adaptation to hypoxia seem to be a promising approach to sensitizing hypoxic carcinomas, gliomas, lymphomas, sarcomas to radiotherapy and, also, liver tumors to radioembolization.

Acid-Sensing Ion Channel-1a in Articular Chondrocytes and Synovial Fibroblasts: A Novel Therapeutic Target for Rheumatoid Arthritis

Acid-sensing ion channel 1a (ASIC1a) is a member of the extracellular H⁺-activated cation channel family. Emerging evidence has suggested that ASIC1a plays a crucial role in the pathogenesis of rheumatoid arthritis (RA). Specifically, ASIC1a could promote inflammation, synovial hyperplasia, articular cartilage, and bone destruction; these lead to the progression of RA, a chronic autoimmune disease characterized by chronic synovial inflammation and extra-articular lesions. In this review, we provided a brief overview of the molecular properties of ASIC1a, including the basic biological characteristics, tissue and cell distribution, channel blocker, and factors influencing the expression and function, and focused on the potential therapeutic targets of ASIC1a in RA and possible mechanisms of blocking ASIC1a to improve RA symptoms, such as regulation of apoptosis, autophagy, pyroptosis, and necroptosis of articular cartilage, and synovial inflammation and invasion of fibroblast-like cells in synovial tissue.

Impact of the acidic environment on gene expression and functional parameters of tumors in vitro and in vivo

Background

The low extracellular pH (pH_e) of tumors resulting from glycolytic metabolism is a stress factor for the cells independent from concomitant hypoxia. The aim of the study was to analyze the impact of acidic pH_e on gene expression on mRNA and protein level in two experimental tumor lines in vitro and in vivo and were compared to hypoxic conditions as well as combined acidosis+hypoxia.

Methods

Gene expression was analyzed in AT1 prostate and Walker-256 mammary carcinoma of the rat by Next Generation Sequencing (NGS), qPCR and Western blot. In addition, the impact of acidosis on tumor cell migration, adhesion, proliferation, cell death and mitochondrial activity was analyzed.

Results

NGS analyses revealed that 147 genes were uniformly regulated in both cell lines (in vitro) and 79 genes in both experimental tumors after 24 h at low pH. A subset of 25 genes was re-evaluated by qPCR and Western blot. Low pH consistently upregulated Aox1, Gls2, Gstp1, Ikbke, Per3, Pink1, Tlr5, Txnip, Ypel3 or downregulated Acat2, Brip1, Clspn, Dnajc25, Ercc6l, Mmd, Rif1, Zmpste24 whereas hypoxia alone led to a downregulation of most of the genes. Direct incubation at low pH reduced tumor cell adhesion whereas acidic pre-incubation increased the adhesive potential. In both tumor lines acidosis induced a G1-arrest (in vivo) of the cell cycle and a strong increase in necrotic cell death (but not in apoptosis). The mitochondrial O₂ consumption increased gradually with decreasing pH.

Conclusions

These data show that acidic pH_e in tumors plays an important role for gene expression independently from hypoxia. In parallel, acidosis modulates functional properties of tumors relevant for their malignant potential and which might be the result of pH-dependent gene expression.

Cisplatin prevents breast cancer metastasis through blocking early EMT and retards cancer growth together with paclitaxel

Cancer growth is usually accompanied by metastasis which kills most cancer patients. Here we aim to study the effect of cisplatin at different doses on breast cancer growth and metastasis.

Methods: We used cisplatin to treat breast cancer cells, then detected the migration of cells and the changes of epithelial-mesenchymal transition (EMT) markers by migration assay, Western blot, and immunofluorescent staining. Next, we analyzed the changes of RNA expression of genes by RNA-seq and confirmed the binding of activating transcription factor 3 (ATF3) to cytoskeleton related genes by ChIP-seq. Thereafter, we combined cisplatin and paclitaxel in a neoadjuvant setting to treat xenograft mouse models. Furthermore, we analyzed the association of disease prognosis with cytoskeletal genes and ATF3 by clinical data analysis.

Results: When administered at a higher dose (6 mg/kg), cisplatin inhibits both cancer growth and metastasis, yet with strong side effects, whereas a lower dose (2 mg/kg) cisplatin blocks cancer metastasis without obvious killing effects. Cisplatin inhibits cancer metastasis through blocking early steps of EMT. It antagonizes transforming growth factor beta (TGFβ) signaling through suppressing transcription of many genes involved in cytoskeleton reorganization and filopodia formation which occur early in EMT and are responsible for cancer metastasis. Mechanistically, TGFβ and fibronectin-1 (FN1) constitute a positive reciprocal regulation loop that is critical for activating TGFβ/SMAD3 signaling, which is repressed by cisplatin induced expression of ATF3. Furthermore, neoadjuvant administration of cisplatin at 2 mg/kg in conjunction with paclitaxel inhibits cancer growth and blocks metastasis without causing obvious side effects by inhibiting colonization of cancer cells in the target organs.

Conclusion: Thus, cisplatin prevents breast cancer metastasis through blocking early EMT, and the combination of cisplatin and paclitaxel represents a promising therapy for killing breast cancer and blocking tumor metastasis.

FNDC1 Promotes the Invasiveness of Gastric Cancer via Wnt/β-Catenin Signaling Pathway and Correlates With Peritoneal Metastasis and Prognosis

Background

Gastric cancer (GC) has a high morbidity and mortality rate, with peritoneal metastasis (PM) identified as the main site of metastasis. Our previous study found that FNDC1 has a higher frequency of mutations in patients with PM by high-throughput sequencing assay, suggesting that it may be associated with GC invasion and PM, however the specific mechanism remains unclear.

Methods

First, the correlation between FNDC1 and PM and prognosis of GC was clarified by bioinformatics and clinicopathological analysis. Next, the effect of FNDC1 expression on the invasion and metastasis ability of GC was investigated in vivo and in vitro. Finally, the signaling pathways involved in the regulation of FNDC1 were explored.

Results

FNDC1 was highly expressed in GC and was associated with PM and poor prognosis. FNDC1 was also associated with epithelial-mesenchymal transition (EMT) in GC cells. Through in vivo and in vitro experiments, it was clarified that knockdown of FNDC1 could inhibit the proliferation, invasion, and migration of GC cells. In addition, it was elucidated that FNDC1 promotes EMT through the Wnt/β-catenin signaling pathway.

Conclusion

FNDC1 may be associated with the invasion of GC and PM after surgery. FNDC1 was highly expressed in GC tissues and cell lines, while significantly associated with poor DFS and OS in GC patients. Both univariate and multivariate analyses suggested that the expression of FNDC1 was an independent factor for GC. Knockdown of FNDC1 also significantly inhibited the proliferation, migration, and activity of GC cells. FNDC1 may promote EMT in GC cells through the regulation of Wnt/β-catenin signaling pathway. FNDC1 has the potential to be used as a predictor of PM and may also be studied in depth as a therapeutic target for GC, which has potential clinical utility and is worthy of further validation.

Rosuvastatin inhibit spheroid formation and epithelial-mesenchymal transition (EMT) in prostate cancer PC-3 cell line

There is a growing body of evidence suggesting antitumor activity of statins. In metastasis and invasion of cancer the Epithelial-Mesenchymal Transition (EMT) of cancerous cells is an important process. Our goal was to understand the effect of Rosuvastatin on the EMT process in human prostate cancer cell line PC-3 cells in adherent 2 dimensional (2D) and spheroid 3 dimensional (3D) culture. PC-3 cells were cultured in adherence and/or spheroid culture system. The cells were treated with different concentrations of Rosuvastatin. After 96 h, the cell proliferation, viability, type and number of spheroids, the expression of E-Cadherin, Vimentin and Zeb-1 were analyzed. The results show that Rosuvastatin inhibit cell proliferation without significant cytotoxicity. The spheroid formation and spheroid sizes were inhibited by Rousavastatin in a dose dependent manner. In 2D culture, expression of the E-Cadherin was increased up to 2.0 fold in a dose dependent linear manner (R² = 0.89). Vimentin and Zeb-1 expressions were decreased up to 40 and 20% of untreated control cells expression level respectively, (R² = 0.99 and 0.92). In 3D system, the expression of E-Cadherin did not show a significant change, but Vimentin and Zeb-1 expressions were decreased up to 70 and 40% of untreated control cells expression level respectively in a dose dependent linear manner in comparison to 2D system (R² = 0.36 and 0.90). Our finding indicates that Rousavastatin inhibit cell proliferation and spheroid formation of PC-3 cells. This inhibition accompanies by inhibition of EMT markers. Therefor, this cholesterol lowering agent could probably have potential in the prevention and suppression of cancer in androgen dependent prostate cancer.

The acidic tumor microenvironment drives a stem-like phenotype in melanoma cells

Abstract

Acidosis characterizes the microenvironment of most solid tumors and is considered a new hallmark of cancer. It is mainly caused by both “aerobic” and “anaerobic” glycolysis of differently adapted cancer cells, with the final product lactic acid being responsible of the extracellular acidification. Many evidences underline the role of extracellular acidosis in tumor progression. Among the different findings, we demonstrated that acidosis-exposed cancer cells are characterized by an epithelial-to-mesenchymal transition phenotype with high invasive ability, high resistance to apoptosis, anchorage-independent growth, and drug therapy. Acidic melanoma cells over-express SOX2, which is crucial for the maintenance of their oxidative metabolism, and carbonic anhydrase IX, that correlates with poor prognosis of cancer patients. Considering these evidences, we realized that the profile outlined for acid cancer cells inevitably remind us the stemness profile. Therefore, we wondered whether extracellular acidosis might induce in cancer cells the acquisition of stem-like properties and contribute to the expansion of the cancer stem cell sub-population. We found that a chronic adaptation to acidosis stimulates in cancer cells the expression of stem-related markers, also providing a high in vitro/in vivo clonogenic and trans-differentiating ability. Moreover, we observed that the acidosis-induced stem-like phenotype of melanoma cells was reversible and related to the EMT induction. These findings help to characterize a further aspect of stem cell niche, contributing to the sustainment and expansion of cancer stem cell subpopulation. Thus, the usage of agents controlling tumor extracellular acidosis might acquire great importance in the clinic for the treatment of aggressive solid tumor.

Key messages

• Extracellular acidosis up-regulates EMT and stem-related markers in melanoma cells

• Acidic medium up-regulates in vitro self-renewal capacity of melanoma cells

• Chronic acidosis adaptation induces trans-differentiation ability in melanoma cells

• Melanoma cells adapted to acidosis show higher tumor-initiating potential than control cells

• Extracellular acidosis promotes a stem-like phenotype in prostate and colorectal carcinoma cells

Glucose promotes epithelial-mesenchymal transitions in bladder cancer by regulating the functions of YAP1 and TAZ

Glucose levels and type 2 diabetes (T2D) are both associated with tumorigenesis and epithelial‐mesenchymal transitions (EMTs). EMTs facilitate bladder cancer (BC) metastasis development, but the mechanism by which high‐glucose levels promote these EMTs in BC remains unclear. Therefore, we sought to elucidate the mechanism underlying EMT promotion due to increased glucose levels. T24 and UMUC‐3 cells were cultured in media containing different glucose concentrations. YAP1, TAZ, GLUT1 and EMT‐associated marker expression was analysed via Western blotting and qPCR. BC cell proliferation and invasion were assessed using MTT and Transwell assays, respectively. A xenograft nude mouse model of diabetes was used to evaluate tumour growth and metastasis in vivo. T2D was positively associated with pathologic grade (P = .016) and TNM stage (P < .001) in BC. High glucose triggered BC cell proliferation and invasion in both in vitro and in vivo conditions. High‐glucose levels also promoted EMTs in BC cells and increased YAP1 and TAZ expression. YAP1 or TAZ knockdown altered EMT marker expression and decreased GLUT1 expression. Overall, our results suggest that high‐glucose levels promote EMTs in BC cells via YAP1 and TAZ regulation. These effector molecules may be promising therapeutic targets for BC cases comorbid with T2D.

The Role of Aberrant Metabolism in Cancer: Insights Into the Interplay Between Cell Metabolic Reprogramming, Metabolic Syndrome, and Cancer

Metabolic syndrome (MetS) is characterized by hyperglycemia, hypertension, dyslipidemia and abdominal obesity. Patients with MetS or other metabolic disorders are more susceptible to cancer development and recurrence and have a worse long-term prognosis. Moreover, the metabolic reprogramming observed in cancer cells has also been described as one of the new hallmarks of cancer. Thus, aberrant metabolism has been proposed as an important risk factor for cancer. Chronic inflammation, reactive oxygen species (ROS), and oncogenic signaling pathways are considered as main potential triggers. Considering the strong association between metabolism and cancer, metabolism-modulating drugs, including metformin and statins, as well as adopting a healthy lifestyle, have been extensively investigated as strategies to combat cancer. Furthermore, strategies that interfere with the metabolic rewiring of cells may also have potent anti-cancer effects. In this article, we provide a comprehensive review of current knowledge on the relationship between aberrant metabolism and cancer and discuss the potential use of metabolism-targeting strategy for the treatment of cancer.

Pharmacological Inhibition of CA-IX Impairs Tumor Cell Proliferation, Migration and Invasiveness

Carbonic anhydrase IX (CA-IX) plays a pivotal role in regulation of pH in tumor milieu catalyzing carbonic acid formation by hydrating CO₂. An acidification of tumor microenvironment contributes to tumor progression via multiple processes, including reduced cell-cell adhesion, increased migration and matrix invasion. We aimed to assess whether the pharmacological inhibition of CA-IX could impair tumor cell proliferation and invasion. Tumor epithelial cells from breast (MDA-MB-231) and lung (A549) cancer were used to evaluate the cytotoxic effect of sulfonamide CA-IX inhibitors. Two CA-IX enzyme blockers were tested, SLC-0111 (at present in phase Ib clinical trial) and AA-06-05. In these cells, the drugs inhibited cell proliferation, migration and invasion through shifting of the mesenchymal phenotype toward an epithelial one and by impairing matrix metalloprotease-2 (MMP-2) activity. The antitumor activity was elicited via apoptosis pathway activation. An upregulation of p53 was observed, which in turn regulated the activation of caspase-3. Inhibition of proteolytic activity was accompanied by upregulation of the endogenous tissue inhibitor TIMP-2. Collectively, these data confirm the potential use of CA-IX inhibitors, and in particular SLC-0111 and AA-06-05, as agents to be further developed, alone or in combination with other conventional anticancer drugs.

Ellagic Acid Inhibits Extracellular Acidity-Induced Invasiveness and Expression of COX1, COX2, Snail, Twist 1, and c-myc in Gastric Carcinoma Cells

Extracellular acidity has been implicated in enhanced malignancy and metastatic features in various cancer cells. Gastric cancer cell lines (AGS and SNU601) maintained in an acidic medium have increased motility and invasiveness. In this study, we investigated the effect of ellagic acid, a plant-derived phenolic compound, on the acidity-promoted migration and invasion of gastric cancer cells. Treating cells maintained in acidic medium with ellagic acid inhibited acidity-mediated migration and invasion, and reduced the expression of MMP7 and MMP9. Examining regulatory factors contributing to the acidity-mediated invasiveness, we found that an acidic pH increased the expression of COX1 and COX2; importantly, expression decreased under the ellagic acid treatment. The general COX inhibitor, sulindac, also decreased acidity-mediated invasion and expression of MMP7 and MMP9. In addition, acidity increased the mRNA protein expression of transcription factors snail, twist1, and c-myc; these were also reduced by ellagic acid. Together, these results suggest that ellagic acid suppresses acidity-enhanced migration and invasion of gastric cancer cells via inhibition of the expression of multiple factors (COX1, COX2, snail, twist1, and c-myc); for this reason, it may be an effective agent for cancer treatment under acidosis.

Ellagic Acid Inhibits Extracellular Acidity-Induced Invasiveness and Expression of COX1, COX2, Snail, Twist 1, and c-myc in Gastric Carcinoma Cells

Extracellular acidity has been implicated in enhanced malignancy and metastatic features in various cancer cells. Gastric cancer cell lines (AGS and SNU601) maintained in an acidic medium have increased motility and invasiveness. In this study, we investigated the effect of ellagic acid, a plant-derived phenolic compound, on the acidity-promoted migration and invasion of gastric cancer cells. Treating cells maintained in acidic medium with ellagic acid inhibited acidity-mediated migration and invasion, and reduced the expression of MMP7 and MMP9. Examining regulatory factors contributing to the acidity-mediated invasiveness, we found that an acidic pH increased the expression of COX1 and COX2; importantly, expression decreased under the ellagic acid treatment. The general COX inhibitor, sulindac, also decreased acidity-mediated invasion and expression of MMP7 and MMP9. In addition, acidity increased the mRNA protein expression of transcription factors snail, twist1, and c-myc; these were also reduced by ellagic acid. Together, these results suggest that ellagic acid suppresses acidity-enhanced migration and invasion of gastric cancer cells via inhibition of the expression of multiple factors (COX1, COX2, snail, twist1, and c-myc); for this reason, it may be an effective agent for cancer treatment under acidosis.

A Model-System to Address the Impact of Phenotypic Heterogeneity and Plasticity on the Development of Cancer Therapies

The main challenges in developing effective anti-cancer therapies stem from the highly complex and heterogeneous nature of cancer, including the presence of multiple genetically-encoded and environmentally-induced cancer cell phenotypes within an individual. This diversity can make the development of successful treatments difficult as different phenotypes can have different responses to the same treatment. The lack of model-systems that can be used to simultaneously test the effect of therapies on multiple distinct phenotypic states further contributes to this problem. To mitigate these challenges, we suggest that in vitro model-systems that consist of several genetically-related but phenotypically distinct populations can be used as proxies for the several phenotypes (including adherent and circulating tumor cells) present in a patient with advanced disease. As proof of concept, we have developed such a model and showed that different phenotypes had different responses to the same challenge (i.e., a change in extracellular pH) both in terms of sensitivity and phenotypic plasticity. We suggest that similar model-systems could be developed and used when designing novel therapeutic strategies, to address the potential impact of phenotypic heterogeneity and plasticity of cancer on the development of successful therapies. Specifically, the effect of a therapy should be considered on more than one cancer cell phenotype (to increase its effectiveness), and both cell viability as well as changes in phenotypic state (to address potential plastic responses) should be evaluated. Although we are aware of the limitations of in vitro systems, we believe that the use of established cell lines that express multiple phenotypes can provide invaluable insights into the complex interplay between therapies and cancer's heterogeneous and plastic nature.

The role of carbonic anhydrase IX in cancer development: links to hypoxia, acidosis, and beyond

Cancer development is a complex process that follows an intricate scenario with a dynamic interplay of selective and adaptive steps and an extensive cast of molecules and signaling pathways. Solid tumor initially grows as an avascular bulk of cells carrying oncogenic mutations until diffusion distances from the nearest functional blood vessels limit delivery of nutrients and oxygen on the one hand and removal of metabolic waste on the other one. These restrictions result in regional hypoxia and acidosis that select for adaptable tumor cells able to promote aberrant angiogenesis, remodel metabolism, acquire invasiveness and metastatic propensity, and gain therapeutic resistance. Tumor cells are thereby endowed with capability to survive and proliferate in hostile microenvironment, communicate with stroma, enter circulation, colonize secondary sites, and generate metastases. While the role of oncogenic mutations initializing and driving these processes is well established, a key contribution of non-genomic, landscaping molecular players is still less appreciated despite they can equally serve as viable targets of anticancer therapies. Carbonic anhydrase IX (CA IX) is one of these players: it is induced by hypoxia, functionally linked to acidosis, implicated in invasiveness, and correlated with therapeutic resistance. Here, we summarize the available experimental evidence supported by accumulating preclinical and clinical data that CA IX can contribute virtually to each step of cancer progression path via its enzyme activity and/or non-catalytic mechanisms. We also propose that targeting tumor cells that express CA IX may provide therapeutic benefits in various settings and combinations with both conventional and newly developed treatments.