Microenvironmental acidosis in carcinogenesis and metastases: new strategies in prevention and therapy

Direct visualization of emergent metastatic features within an ex vivo model of the tumor microenvironment

Ischemic conditions such as hypoxia and nutrient starvation, together with interactions with stromal cells, are critical drivers of metastasis. These conditions arise deep within tumor tissues, and thus, observing nascent metastases is exceedingly challenging. We thus developed the 3MIC-an ex vivo model of the tumor microenvironment-to study the emergence of metastatic features in tumor cells in a 3-dimensional (3D) context. Here, tumor cells spontaneously create ischemic-like conditions, allowing us to study how tumor spheroids migrate, invade, and interact with stromal cells under different metabolic conditions. Consistent with previous data, we show that ischemia increases cell migration and invasion, but the 3MIC allowed us to directly observe and perturb cells while they acquire these pro-metastatic features. Interestingly, our results indicate that medium acidification is one of the strongest pro-metastatic cues and also illustrate using the 3MIC to test anti-metastatic drugs on cells experiencing different metabolic conditions. Overall, the 3MIC can help dissecting the complexity of the tumor microenvironment for the direct observation and perturbation of tumor cells during the early metastatic process.

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.

Metabolic Responses of Lung Adenocarcinoma Cells to Survive under Stressful Conditions Associated with Tumor Microenvironment

Solid tumors frequently present a heterogeneous tumor microenvironment. Because tumors have the potential to proliferate quickly, the consequence is a reduction in the nutrients, a reduction in the pH (<6.8), and a hypoxic environment. Although it is often assumed that tumor clones show a similar growth rate with little variations in nutrient consumption, the present study shows how growth-specific rate (µ), the specific rates of glucose, lactate, and glutamine consumption (qS), and the specific rates of lactate and glutamate production (qP) of 2D-cultured lung tumor cells are affected by changes in their environment. We determined in lung tumor cells (A427, A549, Calu-1, and SKMES-1) the above mentioned kinetic parameters during the exponential phase under different culture conditions, varying the predominant carbon source, pH, and oxygen tension. MCF-7 cells, a breast tumor cell line that can consume lactate, and non-transformed fibroblast cells (MRC-5) were included as controls. We also analyzed how cell-cycle progression and the amino acid transporter CD98 expression were affected. Our results show that: (1) In glucose presence, μ increased, but qS Glucose and qP Lactate decreased when tumor cells were cultured under acidosis as opposed to neutral conditions; (2) most lung cancer cell lines consumed lactate under normoxia or hypoxia; (3) although qS Glutamine diminished under hypoxia or acidosis, it slightly increased in lactate presence, a finding that was associated with CD98 upregulation; and (4) under acidosis, G0/G1 arrest was induced in A427 cancer cells, although this phenomenon was significantly increased when glucose was changed by lactate as the predominant carbon-source. Hence, our results provide an understanding of metabolic responses that tumor cells develop to survive under stressful conditions, providing clues for developing promising opportunities to improve traditional cancer therapies.

Current Update of Research on Exosomes in Cancer

Exosomes are vesicles secreted by the plasma membrane of the cells delimited by a lipid bilayer membrane into the extracellular space of the cell. Their release is associated with the disposal mechanism to remove unwanted materials from the cells. Exosomes released from primary tumour sites migrate to other parts of the body to create a metastatic environment for spreading the tumour cells. We have reviewed that exosomes interfere with the tumour progression by (i) promoting angiogenesis, (ii) initiating metastasis, (iii) regulating tumour microenvironment (TME) and inflammation, (iv) modifying energy metabolism, and (v) transferring mutations. We have found that EVs play an important role in inducing tumour drug resistance against anticancer drugs. This review discusses the potential of exosomes to generate a significant therapeutic effect along with improved diagnosis, prognosis, insights on the various research conducted and their significant findings of our interest.

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.

Heterocyclic and non-heterocyclic arena of monocarboxylate transporter inhibitors to battle tumorigenesis

Monocarboxylate transporters (MCTs) have gained significant attention in cancer research due to their critical role in tumour metabolism. MCTs are legends for transporting lactate molecules in cancer cells, an oncometabolite and waste product of glycolysis, acting as an indispensable factor of tumour proliferation. Targeting MCTs with inhibitors has emerged as a promising strategy to combat tumorigenesis. This article summarizes the most recent research on MCT inhibitors in preventing carcinogenesis, covering both heterocyclic and non-heterocyclic compounds. Heterocyclic and non-heterocyclic compounds such as pteridine, pyrazole, indole, flavonoids, coumarin derivatives and cyanoacetic acid derivatives have been reported as potent MCT inhibitors. We examine the molecular underpinnings of MCTs in cancer metabolism, the design and synthesis of heterocyclic and non-heterocyclic MCT inhibitors, their impact on tumour cells and the microenvironment and their potential as therapeutic agents. Moreover, we explore the challenges associated with MCT inhibitor development and propose future directions for advancing this field. This write-up aims to provide researchers, scientists and clinicians with a comprehensive understanding of the heterocyclic and non-heterocyclic MCT inhibitors and their potential in combating tumorigenesis.

Acidification of intracellular pH in MM tumor cells overcomes resistance to hypoxia-mediated apoptosis in vitro and in vivo

Introduction

Multiple myeloma (MM) is an incurable cancer of malignant plasma cells that engraft in the bone marrow (BM). It is more than likely that the poorly investigated physical parameters of hypoxia and pH in the tumor microenvironment (TME) is critical for MM survival. Here, we explore the effects of a hypoxic environment on pH regulation and its role in MM survival.

Methods

We used in vitro models of MM, in which the culturing medium was modified to specific pH and pO2 levels and then measured the effects on cell survival that was correlated with changes in intracellular (pHi) and extracellular pH (pHe). In a MM xenograft model, we used PET/CT to study hypoxia-mediated effects on tumor growth.

Results

Hypoxia-mediated apoptosis of MM cells is correlated with acidic intracellular pHi (less than < 6.6) that is dependent on HIF activity. Using a polyamide HIF responsive element binding compound, a carbonic anhydrase inhibitor (acetazolamide), and an NHE-1 inhibitor (amiloride) acidified the pHi and lead to cell death. In contrast, treatment of cells with an alkalization agent, Na-lactate, rescued these cells by increasing the pHi (pH > 6.6). Finally, treatment of mice with acetazolamide decreased cell growth in the tumor nodules.

Discussion

Targeting hypoxia and HIF have been proposed as an anti-tumor therapy but the clinical efficacy of such strategies are modest. We propose that targeting the pHi may be more effective at treating cancers within a hypoxic TME.

Serum/glucose starvation strikingly reduces heterogeneous nuclear ribonucleoprotein A1 protein and its target, cyclin D1

Our investigation to explore cellular alterations related to undernutrition in cancer cells revealed that the protein level of heterogenous nuclear ribonucleoprotein A1 (hnRNP A1) is drastically decreased by serum/glucose starvation. Its loss was reversible, serum/glucose starvation-specific and universal throughout cell types and species. The hnRNP A1 mRNA level and hnRNP A1 mRNA/protein stability were not altered under this condition. CCND1 mRNA, which we newly identified as the binding target of hnRNP A1, was decreased by serum/glucose starvation. Under similar conditions, CCND1 protein was reduced in vitro and in vivo, whereas hnRNP A1 mRNA level and CCND1 mRNA level revealed no correlation in most clinical samples. Functional analyses revealed that CCND1 mRNA stability is certainly dependent on hnRNP A1 protein level and that RNA recognition motif-1 (RRM1) in hnRNP A1 plays a central role in maintaining CCND1 mRNA stability and subsequent protein expression. The injection of RRM1-deleted hnRNP A1-expressing cancer cells in the mouse xenograft model did not form any tumours, and that of hnRNP A1-expressing cancer cells retained CCND1 expression at the lesion adjacent to necrosis with a slight increase in tumour volume. Furthermore, RRM1 deletion caused growth suppression with the induction of apoptosis and autophagy, whereas CCND1 restoration completely recovered it. Our results indicate that serum/glucose starvation triggers entire hnRNP A1 protein loss, and its loss may play a role in CCND1 mRNA destabilization and CCND1-mediated cellular event inhibition, i.e. growth promotion, apoptosis induction and autophagosome formation.

Increased mortality in patients with hematologic malignancies treated with proton pump inhibitors: a nationwide cohort study

Proton Pump inhibitors (PPIs) are frequently prescribed to cancer patients to prevent gastric mucosal damage. Post-diagnostic PPI use in patients with solid tumors may be associated with increased cancer mortality. However, the hazardous impact of PPIs in patients with hematologic malignancies remains unknown. This association was investigated in a large, retrospective cohort study using data from the Danish nationwide health registries. The outcomes were cancer-specific or non-cancer deaths. We identified 15,320 patients with hematologic malignancies and of these 1811 were identified as post-diagnostic PPI users. PPI users had significantly increased HRs for cancer-specific mortality (HR 1.31; 95% CI, 1.18-1.44) and 1-year cancer-specific mortality (HR 1.50, 95% CI 1.29-1.74) as compared to nonusers. The association between PPI use and increased cancer-specific mortality in Danish patients with hematologic malignancies supports the raised concerns regarding the frequent use of PPIs in cancer patients.

Horizontal Transfer of Malignant Traits and the Involvement of Extracellular Vesicles in Metastasis

Metastases are responsible for the vast majority of cancer deaths, yet most therapeutic efforts have focused on targeting and interrupting tumor growth rather than impairing the metastatic process. Traditionally, cancer metastasis is attributed to the dissemination of neoplastic cells from the primary tumor to distant organs through blood and lymphatic circulation. A thorough understanding of the metastatic process is essential to develop new therapeutic strategies that improve cancer survival. Since Paget's original description of the "Seed and Soil" hypothesis over a hundred years ago, alternative theories and new players have been proposed. In particular, the role of extracellular vesicles (EVs) released by cancer cells and their uptake by neighboring cells or at distinct anatomical sites has been explored. Here, we will outline and discuss these alternative theories and emphasize the horizontal transfer of EV-associated biomolecules as a possibly major event leading to cell transformation and the induction of metastases. We will also highlight the recently discovered intracellular pathway used by EVs to deliver their cargoes into the nucleus of recipient cells, which is a potential target for novel anti-metastatic strategies.

Cancer metabolism within tumor microenvironments

BACKGROUND

Tumor microenvironments could determine cancer heterogeneity and malignancy. Hypoxia, nutrition starvation, and acidic pH could contribute to cancer malignancy associated with genetic, epigenetic, and metabolic alterations, promoting invasion and metastasis. Cancer cells adapting to extreme tumor microenvironments could enable evasion of cell death and immune responses. It could stimulate drug resistance and recurrence, resulting in poor patient prognosis. Therefore, investigating druggable targets of the malignant cancer cells within tumor microenvironments is necessary, but such treatments are limited. Cell-cell metabolic interaction may also contribute to cancer malignancy within the tumor microenvironments. Organelle-organelle interactions have recently gained attention as new cancer therapy targets as they play essential roles in the metabolic adaptation to the tumor microenvironment. In this review, we overview (1) metabolic alterations within tumor microenvironments, (2) cell-to-cell, and (3) organelle-to-organelle metabolic interactions, and we add novel insights into cancer therapy.

Stress-Inducible SCAND Factors Suppress the Stress Response and Are Biomarkers for Enhanced Prognosis in Cancers

The cell stress response is an essential system present in every cell for responding and adapting to environmental stimulations. A major program for stress response is the heat shock factor (HSF)–heat shock protein (HSP) system that maintains proteostasis in cells and promotes cancer progression. However, less is known about how the cell stress response is regulated by alternative transcription factors. Here, we show that the SCAN domain (SCAND)-containing transcription factors (SCAN-TFs) are involved in repressing the stress response in cancer. SCAND1 and SCAND2 are SCAND-only proteins that can hetero-oligomerize with SCAN-zinc finger transcription factors, such as MZF1(ZSCAN6), for accessing DNA and transcriptionally co-repressing target genes. We found that heat stress induced the expression of SCAND1, SCAND2, and MZF1 bound to HSP90 gene promoter regions in prostate cancer cells. Moreover, heat stress switched the transcript variants’ expression from long noncoding RNA (lncRNA-SCAND2P) to protein-coding mRNA of SCAND2, potentially by regulating alternative splicing. High expression of HSP90AA1 correlated with poorer prognoses in several cancer types, although SCAND1 and MZF1 blocked the heat shock responsiveness of HSP90AA1 in prostate cancer cells. Consistent with this, gene expression of SCAND2, SCAND1, and MZF1 was negatively correlated with HSP90 gene expression in prostate adenocarcinoma. By searching databases of patient-derived tumor samples, we found that MZF1 and SCAND2 RNA were more highly expressed in normal tissues than in tumor tissues in several cancer types. Of note, high RNA expression of SCAND2, SCAND1, and MZF1 correlated with enhanced prognoses of pancreatic cancer and head and neck cancers. Additionally, high expression of SCAND2 RNA was correlated with better prognoses of lung adenocarcinoma and sarcoma. These data suggest that the stress-inducible SCAN-TFs can function as a feedback system, suppressing excessive stress response and inhibiting cancers.

Low Serum Bicarbonate Levels Increase the Risk of All-Cause, Cardiovascular Disease, and Cancer Mortality in Type 2 Diabetes

CONTEXT

The evidence regarding bicarbonate status and mortality among diabetes is scarce.

OBJECTIVE

The purpose of this study was to investigate the associations of bicarbonate concentrations with risk of all-cause, cardiovascular disease (CVD), and cancer mortality among patients with type 2 diabetes (T2D).

METHODS

This study included 8163 adult diabetic patients from the National Health and Nutrition Examination Survey (NHANES), 1999 to 2018. Death outcomes were ascertained by linkage to National Death Index records through 31 December 2019. The Cox proportional-risk model was used to estimate hazard ratios (HR) and 95% CIs for mortality from all causes, CVD, and cancer. The mediating effects of 11 metabolic, cardiovascular, and renal biomarkers were evaluated using a logistic regression model within a counterfactual framework.

RESULTS

During 8163 person-years of follow-up, 2310 deaths were documented, including 659 CVD deaths and 399 cancer deaths. After multivariate adjustment, lower serum bicarbonate levels were significantly linearly correlated with higher all-cause, CVD, and cancer mortality: The risk of all-cause death increased by 40%, the risk of CVD death increased by 48%, and the risk of cancer death increased by 84% compared with the normal group (all P < .05). Altered levels of estimated glomerular filtration rate explained 12.10% and 16.94% of the relation between serum bicarbonate with all-cause and CVD mortality, respectively. Total cholesterol mediated 4.70% and 10.51% of the associations of all-cause and CVD mortality, respectively.

CONCLUSION

Lower serum bicarbonate concentrations were significantly associated with higher all-cause, CVD, and cancer mortality. These findings suggest that maintaining adequate bicarbonate status may lower mortality risk in individuals with T2D.

Proposal to Consider Chemical/Physical Microenvironment as a New Therapeutic Off-Target Approach

The molecular revolution could lead drug discovery from chance observation to the rational design of new classes of drugs that could simultaneously be more effective and less toxic. Unfortunately, we are witnessing some failure in this sense, and the causes of the crisis involve a wide range of epistemological and scientific aspects. In pharmacology, one key point is the crisis of the paradigm the “magic bullet”, which is to design therapies based on specific molecular targets. Drug repurposing is one of the proposed ways out of the crisis and is based on the off-target effects of known drugs. Here, we propose the microenvironment as the ideal place to direct the off-targeting of known drugs. While it has been extensively investigated in tumors, the generation of a harsh microenvironment is also a phenotype of the vast majority of chronic diseases. The hostile microenvironment, on the one hand, reduces the efficacy of both chemical and biological drugs; on the other hand, it dictates a sort of “Darwinian” selection of those cells armed to survive in such hostile conditions. This opens the way to the consideration of the microenvironment as a convenient target for pharmacological action, with a clear example in proton pump inhibitors.

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.

Kaempferol impairs aerobic glycolysis against melanoma metastasis via inhibiting the mitochondrial binding of HK2 and VDAC1

Metastasis is the leading cause of death in melanoma patients. Aerobic glycolysis is a common metabolic feature in tumor and is closely related to cell growth and metastasis. Kaempferol (KAM) is one of the active ingredients in the total flavonoids of Chinese traditional medicine Sparganii Rhizoma. Studies have shown that it interferes with the cell cycle, apoptosis, angiogenesis and metastasis of tumor cells, but whether it can affect the aerobic glycolysis of melanoma is still unclear. Here, we explored the effects and mechanisms of KAM on melanoma metastasis and aerobic glycolysis. KAM inhibited the migration and invasion of A375 and B16F10 cells, and reduced the lung metastasis of melanoma cells. Extracellular acidification rates (ECAR) and glucose consumption were obviously suppressed by KAM, as well as the production of ATP, pyruvate and lactate. Mechanistically, the activity of hexokinase (HK), the first key kinase of aerobic glycolysis, was significantly inhibited by KAM. Although the total protein expression of HK2 was not significantly changed, the binding of HK2 and voltage-dependent anion channel 1 (VDAC1) on mitochondria was inhibited by KAM through AKT/GSK-3β signal pathway. In conclusion, KAM inhibits melanoma metastasis via blocking aerobic glycolysis of melanoma cells, in which the binding of HK2 and VDAC1 on mitochondria was broken.

The acidic tumour microenvironment: Manipulating the immune response to elicit escape

The success of cancer treatment relies on the composition of the tumour microenvironment which is comprised of tumour cells, blood vessels, stromal cells, immune cells, and extracellular matrix components. Barriers to effective cancer treatment need to be overcome, and the acidic microenvironment of the tumour provides a key target for treatment. This review intends to provide an overview of the effects that low extracellular pH has on components of the tumour microenvironment and how they contribute to immune escape. Further, potential therapeutic targets will be discussed.

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.

Targeting the Interplay between Cancer Metabolic Reprogramming and Cell Death Pathways as a Viable Therapeutic Path

In cancer cells, metabolic adaptations are often observed in terms of nutrient absorption, biosynthesis of macromolecules, and production of energy necessary to meet the needs of the tumor cell such as uncontrolled proliferation, dissemination, and acquisition of resistance to death processes induced by both unfavorable environmental conditions and therapeutic drugs. Many oncogenes and tumor suppressor genes have a significant effect on cellular metabolism, as there is a close relationship between the pathways activated by these genes and the various metabolic options. The metabolic adaptations observed in cancer cells not only promote their proliferation and invasion, but also their survival by inducing intrinsic and acquired resistance to various anticancer agents and to various forms of cell death, such as apoptosis, necroptosis, autophagy, and ferroptosis. In this review we analyze the main metabolic differences between cancer and non-cancer cells and how these can affect the various cell death pathways, effectively determining the susceptibility of cancer cells to therapy-induced death. Targeting the metabolic peculiarities of cancer could represent in the near future an innovative therapeutic strategy for the treatment of those tumors whose metabolic characteristics are known.

Extracellular vesicles: General features and usefulness in diagnosis and therapeutic management of colorectal cancer

In the world, among all type of cancers, colorectal cancer (CRC) is the third most commonly diagnosed in males and the second in females. In most of cases, (RP1) patients’ prognosis limitation with malignant tumors can be attributed to delayed diagnosis of the disease. Identification of patients with early-stage disease leads to more effective therapeutic interventions. Therefore, new screening methods and further innovative treatment approaches are mandatory as they may lead to an increase in progression-free and overall survival rates. For the last decade, the interest in extracellular vesicles (EVs) research has exponentially increased as EVs generation appears to be a universal feature of every cell that is strongly involved in many mechanisms of cell-cell communication either in physiological or pathological situations. EVs can cargo biomolecules, such as lipids, proteins, nucleic acids and generate transmission signal through the intercellular transfer of their content. By this mechanism, tumor cells can recruit and modify the adjacent and systemic microenvironment to support further invasion and dissemination. This review intends to cover the most recent literature on the role of EVs production in colorectal normal and cancer tissues. Specific attention is paid to the use of EVs for early CRC diagnosis, follow-up, and prognosis as EVs have come into the spotlight of research as a high potential source of ‘liquid biopsies’. The use of EVs as new targets or nanovectors as drug delivery systems for CRC therapy is also summarized.

Plasmatic Exosome Number and Size Distinguish Prostate Cancer Patients From Healthy Individuals: A Prospective Clinical Study

There is a urgent need for valuable strategy in early and less invasive diagnosis for cancer. Preliminary data have shown that the plasmatic levels of exosomes increase in cancer condition. This study investigates the relevance of plasmatic levels and size distribution of exosomes in 42 individuals with no signs of urological disease (CTR) as compared to 65 prostate cancer patients (PCa). It was used Nanoparticle Tracking Analysis (NTA), a highly reliable and sensitive method for exosomes characterization and quantification. The relation structure among the NTA-derived parameters was assessed by means of Principal Component Analysis, which allowed detecting the global discriminant power of NTA test in terms of Receiver Operating Characteristic (ROC) curve and the selection of cut-off thresholds. The results showed that PCa had significantly higher plasmatic levels of exosomes and that the exosomes were smaller in size as compared to the CTR; the values reached 89% sensitivity and 71% specificity, in distinguishing PCa from CTR. These results propose a new exosome-based non-invasive clinical approach for the clinical follow-up of prostate cancer undergoing surgical treatment; in addition this method may be developed as a new screening test for prostate cancer's early diagnosis. While this clinical study was performed in prostate cancer, it may represent a proof of concept extendable to virtually all cancers, as it is suggested by both pre-clinical evidence and clinical data obtained with different technical approaches.

Improved Chemotherapy Outcomes of Patients With Small-cell Lung Cancer Treated With Combined Alkalization Therapy and Intravenous Vitamin C

Background/Aim

This study aimed to investigate the effects of the combination of alkalization therapy (an alkaline diet and bicarbonate therapy) and intravenous vitamin C treatment on chemotherapy outcomes in patients with small-cell lung cancer (SCLC) (study registration: UMIN000043056).

Patients and Methods

Twelve patients with SCLC in the intervention group (receiving both alkalization therapy and vitamin C treatment together with chemotherapy) were retrospectively compared to 15 patients with SCLC in the control group (receiving chemotherapy only).

Results

The mean urine pH of the intervention group was significantly higher than that of the control group (7.32±0.45 vs. 6.44±0.74, respectively; p<0.005). The median overall survival for the intervention group was 44.2 months (95% confidence interval=22.0-not reached), as compared with 17.7 months for the control group (95% confidence intervaI=13.5-not reached; p<0.05).

Conclusion

The combination of alkalization therapy and intravenous vitamin C treatment may be associated with favorable outcomes in patients with SCLC receiving chemotherapy.

Effects of Alkalization Therapy on Chemotherapy Outcomes in Advanced Pancreatic Cancer: A Retrospective Case-Control Study

BACKGROUND/AIM

Neutralization of the acidic tumor microenvironment, which is associated with both progression and drug resistance of cancer cells, may be a new treatment option for progressing forms of cancer. We conducted a case-control study to investigate the effects of alkalization therapy, consisting of an alkaline diet with supplementary oral sodium bicarbonate, in patients with metastatic or recurrent pancreatic cancer (study registration no.: UMIN000036126).

PATIENTS AND METHODS

Thirty-six patients in the alkalization group (Karasuma Wada Clinic; alkalization therapy plus chemotherapy) were retrospectively compared to 89 patients in the control group (Kyoto University Hospital; chemotherapy only).

RESULTS

The median overall survival (OS) in the alkalization group was significantly longer than that in the control group (15.4 vs. 10.8 months; p<0.005). In the alkalization group, mean urine pH was significantly increased after alkalization therapy [6.38±0.85 (before) vs. 6.80±0.71 (after); p<0.05]. Furthermore, the median OS of patients with increased urine pH (pH>7.0 or ΔpH>1.0) in the alkalization group was significantly longer than that of the control group.

CONCLUSION

Alkalization therapy may enhance the effects of chemotherapy in patients with advanced pancreatic cancer.

A Mathematical Study of the Influence of Hypoxia and Acidity on the Evolutionary Dynamics of Cancer

Hypoxia and acidity act as environmental stressors promoting selection for cancer cells with a more aggressive phenotype. As a result, a deeper theoretical understanding of the spatio-temporal processes that drive the adaptation of tumour cells to hypoxic and acidic microenvironments may open up new avenues of research in oncology and cancer treatment. We present a mathematical model to study the influence of hypoxia and acidity on the evolutionary dynamics of cancer cells in vascularised tumours. The model is formulated as a system of partial integro-differential equations that describe the phenotypic evolution of cancer cells in response to dynamic variations in the spatial distribution of three abiotic factors that are key players in tumour metabolism: oxygen, glucose and lactate. The results of numerical simulations of a calibrated version of the model based on real data recapitulate the eco-evolutionary spatial dynamics of tumour cells and their adaptation to hypoxic and acidic microenvironments. Moreover, such results demonstrate how nonlinear interactions between tumour cells and abiotic factors can lead to the formation of environmental gradients which select for cells with phenotypic characteristics that vary with distance from intra-tumour blood vessels, thus promoting the emergence of intra-tumour phenotypic heterogeneity. Finally, our theoretical findings reconcile the conclusions of earlier studies by showing that the order in which resistance to hypoxia and resistance to acidity arise in tumours depend on the ways in which oxygen and lactate act as environmental stressors in the evolutionary dynamics of cancer cells.

Interplay within tumor microenvironment orchestrates neoplastic RNA metabolism and transcriptome diversity

The heterogeneous population of cancer cells within a tumor mass interacts intricately with the multifaceted aspects of the surrounding microenvironment. The reciprocal crosstalk between cancer cells and the tumor microenvironment (TME) shapes the cancer pathophysiome in a way that renders it uniquely suited for immune tolerance, angiogenesis, metastasis, and therapy resistance. This dynamic interaction involves a dramatic reconstruction of the transcriptomic landscape of tumors by altering the synthesis, modifications, stability, and processing of gene readouts. In this review, we categorically evaluate the influence of TME components, encompassing a myriad of resident and infiltrating cells, signaling molecules, extracellular vesicles, extracellular matrix, and blood vessels, in orchestrating the cancer-specific metabolism and diversity of both mRNA and noncoding RNA, including micro RNA, long noncoding RNA, circular RNA among others. We also highlight the transcriptomic adaptations in response to the physicochemical idiosyncrasies of TME, which include tumor hypoxia, extracellular acidosis, and osmotic stress. Finally, we provide a nuanced analysis of existing and prospective therapeutics targeting TME to ameliorate cancer-associated RNA metabolism, consequently thwarting the cancer progression. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease.

New hypotheses for cancer generation and progression

Since Nixon famously declared war on cancer in 1971, trillions of dollars have been spent on cancer research but the life expectancy for most forms of cancer is still poor. There are many reasons for the partial success of cancer translational research. One of these can be the predominance of certain paradigms that potentially narrowed the vision in interpreting cancer. The main paradigm to explain carcinogenesis is based on DNA mutations, which is well interpreted by the somatic mutation theory (SMT). However, a different theory claims that cancer is instead a tissue disease as proposed by the Tissue Organization Field Theory (TOFT). Here, we propose new hypotheses to explain the origin and pathogenesis of cancer. In this perspective, the systemic-evolutionary theory of cancer (SETOC) is discussed as well as how the microenvironment affects the adaptation of transformed cells and the reversion to a unicellular-like or embryo-like phenotype.

Performance of capecitabine in novel combination therapies in colorectal cancer

Colorectal cancer is one of the most common cancers throughout the world, and no definitive cure has ever been found. Perhaps a new insight into the effectiveness of chemotherapy drugs could help better treat patients. Targeted therapies have significantly improved the median overall survival of colorectal cancer patients. One of the standard chemotherapy regimens used for colorectal cancer is capecitabine, which is important in monotherapy and combination therapies. Capecitabine, with other chemotherapeutic agents (irinotecan, oxaliplatin, perifosine, 17-allylamino-17-demethoxygeldanamycin, aspirin, celecoxib, statins, quinacrine, inositol hexaphosphate and inositol, cystine/theanine, curcumin, and isorhamnetin), and biological ones (antibodies) plays an important role in the inhibition of some signaling pathways, increasing survival, reducing tumor growth and side effects of capecitabine. However, some drugs, such as proton pump inhibitors, are negatively related to capecitabine; therefore, the purpose of this work is to review and discuss the performance of capecitabine combination therapies in colorectal cancer.

Sodium bicarbonate transporter NBCe1 regulates proliferation and viability of human prostate cancer cells LNCaP and PC3

Studies on cultured cancer cells or cell lines have revealed multiple acid extrusion mechanisms and their involvement in cancer cell growth and progression. In the present study, the role of the sodium bicarbonate transporters (NBCs) in prostate cancer cell proliferation and viability was examined. qPCR revealed heterogeneous expression of five NBC isoforms in human prostate cancer cell lines LNCaP, PC3, 22RV1, C4-2, DU145, and the prostate cell line RWPE-1. In fluorescence pH measurement of LNCaP cells, which predominantly express NBCe1, Na⁺ and HCO₃^–-mediated acid extrusion was identified by bath ion replacement and sensitivity to the NBC inhibitor S0859. NBCe1 knockdown using siRNA oligonucleotides decreased the number of viable cells, and pharmacological inhibition with S0859 (50 µM) resulted in a similar decrease. NBCe1 knockdown and inhibition also increased cell death, but this effect was small and slow. In PC3 cells, which express all NBC isoforms, NBCe1 knockdown decreased viable cell number and increased cell death. The effects of NBCe1 knockdown were comparable to those by S0859, indicating that NBCe1 among NBCs primarily contributes to PC3 cell proliferation and viability. S0859 inhibition also decreased the formation of cell spheres in 3D cultures. Immunohistochemistry of human prostate cancer tissue microarrays revealed NBCe1 localization to the glandular epithelial cells in prostate tissue and robust expression in acinar and duct adenocarcinoma. In conclusion, our study demonstrates that NBCe1 regulates acid extrusion in prostate cancer cells and inhibiting or abolishing this transporter decreases cancer cell proliferation.

Abnormal saccharides affecting cancer multi-drug resistance (MDR) and the reversal strategies

Clinically, chemotherapy is the mainstay in the treatment of multiple cancers. However, highly adaptable and activated survival signaling pathways of cancer cells readily emerge after long exposure to chemotherapeutics drugs, resulting in multi-drug resistance (MDR) and treatment failure. Recently, growing evidences indicate that the molecular action mechanisms of cancer MDR are closely associated with abnormalities in saccharides. In this review, saccharides affecting cancer MDR development are elaborated and analyzed in terms of aberrant aerobic glycolysis and its related enzymes, abnormal glycan structures and their associated enzymes, and glycoproteins. The reversal strategies including depletion of ATP, circumventing the original MDR pathway, activation by or inhibition of sugar-related enzymes, combination therapy with traditional cytotoxic agents, and direct modification on the sugar moiety, are ultimately proposed. It follows that abnormal saccharides have a significant effect on cancer MDR development, providing a new perspective for overcoming MDR and improving the outcome of chemotherapy.

Biomarkers in Prostate Cancer Diagnosis: From Current Knowledge to the Role of Metabolomics and Exosomes

Early detection of prostate cancer (PC) is largely carried out using assessment of prostate-specific antigen (PSA) level; yet it cannot reliably discriminate between benign pathologies and clinically significant forms of PC. To overcome the current limitations of PSA, new urinary and serum biomarkers have been developed in recent years. Although several biomarkers have been explored in various scenarios and patient settings, to date, specific guidelines with a high level of evidence on the use of these markers are lacking. Recent advances in metabolomic, genomics, and proteomics have made new potential biomarkers available. A number of studies focused on the characterization of the specific PC metabolic phenotype using different experimental approaches has been recently reported; yet, to date, research on metabolomic application for PC has focused on a small group of metabolites that have been known to be related to the prostate gland. Exosomes are extracellular vesicles that are secreted from all mammalian cells and virtually detected in all bio-fluids, thus allowing their use as tumor biomarkers. Thanks to a general improvement of the technical equipment to analyze exosomes, we are able to obtain reliable quantitative and qualitative information useful for clinical application. Although some pilot clinical investigations have proposed potential PC biomarkers, data are still preliminary and non-conclusive.

[Phosphorus MR spectroscopy and 18F-FDG PET/CT in the study of energy metabolism of glial tumors]

OBJECTIVE

To study energy metabolism in glial tumors using dynamic MR spectroscopy and ¹⁸F-FDG PET/CT.

MATERIAL AND METHODS

The study included 19 patients (9 women and 10 men) with newly diagnosed supratentorial glial tumors WHO Grade I-IV (diffuse astrocytoma - 4 cases, oligodendroglioma - 4 cases, anaplastic astrocytoma - 5 cases, glioblastoma - 6 cases). All patients underwent examination and surgical treatment at the Burdenko Neurosurgery Center. Dynamic MR spectroscopy and ¹⁸F-FDG PET/CT were applied in each patient.

RESULTS

We found multiple correlations between the ratio of bioorganic phosphate peaks and parameters of glucose uptake by tumor tissue. These relationships were more significant in patients with high-grade tumors: positive significant correlation between SUVtumor and PME/PCr ratio (R_S=0.75, p=0.01), T/Nmix and βATP/Pi ratio (R_s=0.76, p=0.02), SUVpeaktumor and aATP/Pi ratio (R_S=0.77, p=0.008). Moreover, there were negative correlations between SUVtumor and PCr/bATP ratio (R_S= -0.66, p=0.05), T/Nmix and PDE/bATP ratio (R_S= -0.83, p=0.006), SUVpeaktumor and PDE/aATP ratio (R_S= -0.76, p=0.009).

CONCLUSION

High-grade gliomas were characterized by higher glucose consumption, ATP release (intensification of energy metabolism) and faster cell membrane synthesis. These processes indicate enhanced proliferation of tumor cells (intensification of plastic metabolism).

Warburg Effect Is a Cancer Immune Evasion Mechanism Against Macrophage Immunosurveillance

Evasion of immunosurveillance is critical for cancer initiation and development. The expression of “don’t eat me” signals protects cancer cells from being phagocytosed by macrophages, and the blockade of such signals demonstrates therapeutic potential by restoring the susceptibility of cancer cells to macrophage-mediated phagocytosis. However, whether additional self-protective mechanisms play a role against macrophage surveillance remains unexplored. Here, we derived a macrophage-resistant cancer model from cells deficient in the expression of CD47, a major “don’t eat me” signal, via a macrophage selection assay. Comparative studies performed between the parental and resistant cells identified self-protective traits independent of CD47, which were examined with both pharmacological or genetic approaches in in vitro phagocytosis assays and in vivo tumor models for their roles in protecting against macrophage surveillance. Here we demonstrated that extracellular acidification resulting from glycolysis in cancer cells protected them against macrophage-mediated phagocytosis. The acidic tumor microenvironment resulted in direct inhibition of macrophage phagocytic ability and recruitment of weakly phagocytic macrophages. Targeting V-ATPase which transports excessive protons in cancer cells to acidify extracellular medium elicited a pro-phagocytic microenvironment with an increased ratio of M1-/M2-like macrophage populations, therefore inhibiting tumor development and metastasis. In addition, blockade of extracellular acidification enhanced cell surface exposure of CD71, targeting which by antibodies promoted cancer cell phagocytosis. Our results reveal that extracellular acidification due to the Warburg effect confers immune evasion ability on cancer cells. This previously unrecognized role highlights the components mediating the Warburg effect as potential targets for new immunotherapy harnessing the tumoricidal capabilities of macrophages.

The Mitochondrial Chaperone TRAP1 as a Candidate Target of Oncotherapy

Tumor necrosis factor receptor-associated protein 1 (TRAP1), a member of the heat shock protein 90 (Hsp90) chaperone family, protects cells against oxidative stress and maintains mitochondrial integrity. To date, numerous studies have focused on understanding the relationship between aberrant TRAP1 expression and tumorigenesis. Mitochondrial TRAP1 is a key regulatory factor involved in metabolic reprogramming in tumor cells that favors the metabolic switch of tumor cells toward the Warburg phenotype. In addition, TRAP1 is involved in dual regulation of the mitochondrial apoptotic pathway and exerts an antiapoptotic effect on tumor cells. Furthermore, TRAP1 is involved in many cellular pathways by disrupting the cell cycle, increasing cell motility, and promoting tumor cell invasion and metastasis. Thus, TRAP1 is a very important therapeutic target, and treatment with TRAP1 inhibitors combined with chemotherapeutic agents may become a new therapeutic strategy for cancer. This review discusses the molecular mechanisms by which TRAP1 regulates tumor progression, considers its role in apoptosis, and summarizes recent advances in the development of selective, targeted TRAP1 and Hsp90 inhibitors.

Potential roles and prognostic significance of exosomes in cancer drug resistance

Drug resistance is a major impediment in cancer therapy which strongly reduces the efficiency of anti-cancer drugs. Exosomes are extracellular vesicles with cup or spherical shape with a size range of 40-150 nm released by eukaryotic cells that contain genetic materials, proteins, and lipids which mediate a specific cell-to-cell communication. The potential roles of exosomes in intrinsic and acquired drug resistance have been reported in several studies. Furthermore, a line of evidence suggested that the content of exosomes released from tumor cells in biological samples may be associated with the clinical outcomes of cancer patients. In this review, we highlighted the recent studies regarding the potential roles of exosomes in tumor initiation, progression, and chemoresistance. This study suggests the possible role of exosomes for drug delivery and their contents in prognosis and resistance to chemotherapy in cancer patients.

Lipidomic analysis of cancer cells cultivated at acidic pH reveals phospholipid fatty acids remodelling associated with transcriptional reprogramming

Cancer cells need to modulate the biosynthesis of membrane lipids and fatty acids to adapt themselves to an accelerated rate of cell division and survive into an extracellular environment characterised by a low pH. To gain insight this crucial survival process, we investigated the lipid composition of Mel 501 melanoma cells cultured at either physiological or acidic pH and observed the remodelling of phospholipids towards longer and more unsaturated acyl chains at low pH. This modification was related to changes in gene expression profile, as we observed an up-regulation of genes involved in acyl chain desaturation, elongation and transfer to phospholipids. PC3 prostate and MCF7 breast cancer cells adapted at acidic pH also demonstrated phospholipid fatty acid remodelling related to gene expression changes. Overall findings clearly indicate that low extracellular pH impresses a specific lipid signature to cells, associated with transcriptional reprogramming.

[Intracellular pH measurement in glioblastoma cells: the possibilities of phosphorus-31 MR spectroscopy]

OBJECTIVE

To analyze intracellular pH measurement with phosphorus-31 MR spectroscopy in glioblastoma cells and to compare these data with intracellular pH in healthy volunteers.

MATERIAL AND METHODS

There were 10 patients aged 41 - 67 years with supratentorial glioblastomas. Intracellular pH in glioblastoma cells was compared with pH in healthy persons.

RESULTS

We found a tendency to increased intracellular pH in glioblastoma cells in comparison with pH in intact brain tissue.

CONCLUSION

Intracellular pH in brain tissue can be used as a potential marker of early abnormalities which could not be detected by conventional MRI. Moreover, these data may be valuable to estimate the efficacy of chemotherapy. The study was supported by Russian Science Foundation (grant No. 18-15-00337).

Role of Regular Physical Exercise in Tumor Vasculature: Favorable Modulator of Tumor Milieu

The tumor vessel network has been investigated as a precursor of an inhospitable tumor microenvironment, including its repercussions in tumor perfusion, oxygenation, interstitial fluid pressure, pH, and immune response. Dysfunctional tumor vasculature leads to the extravasation of blood to the interstitial space, hindering proper perfusion and causing interstitial hypertension. Consequently, the inadequate delivery of oxygen and clearance of by-products of metabolism promote the development of intratumoral hypoxia and acidification, hampering the action of immune cells and resulting in more aggressive tumors. Thus, pharmacological strategies targeting tumor vasculature were developed, but the overall outcome was not satisfactory due to its transient nature and the higher risk of hypoxia and metastasis. Therefore, physical exercise emerged as a potential favorable modulator of tumor vasculature, improving intratumoral vascularization and perfusion. Indeed, it seems that regular exercise practice is associated with lasting tumor vascular maturity, reduced vascular resistance, and increased vascular conductance. Higher vascular conductance reduces intratumoral hypoxia and increases the accessibility of circulating immune cells to the tumor milieu, inhibiting tumor development and improving cancer treatment. The present paper describes the implications of abnormal vasculature on the tumor microenvironment and the underlying mechanisms promoted by regular physical exercise for the re-establishment of more physiological tumor vasculature.

Plasmatic exosomes from prostate cancer patients show increased carbonic anhydrase IX expression and activity and low pH

Acidity, hypoxia and increased release of exosomes are severe phenotypes of tumours. The regulation of pH in tumours involves the interaction of several proteins, including the carbonic anhydrases which catalyze the formation of bicarbonate and protons from carbon dioxide and water. Among CA isoforms, CA IX is over-expressed in a large number of solid tumours, conferring to cancer cells a survival advantage in hypoxic and acidic microenvironment, but there isn't evidence that CA IX expression could have a real clinical impact. Therefore, in this study for the first time the expression and activity of CA IX have been investigated in the plasmatic exosomes obtained from patients with prostate carcinoma (PCa). For this purpose, the study was performed through different methodological approaches, such as NTA, western blot analysis, enzyme activity assay, Nanoscale flow cytometry, ELISA, confocal microscopy. The results showed that PCa exosomes significantly overexpressed CA IX levels and related activity as compared to healthy donors. Furthermore, CA IX expression and activity were correlated to the exosome intraluminal pH, demonstrating for the first time that PCa exosomes are acidic. Our data suggest the possible use of the exosomal CA IX expression and activity as a biomarker of cancer progression in PCa.

The Acidic Microenvironment: Is It a Phenotype of All Cancers? A Focus on Multiple Myeloma and Some Analogies with Diabetes Mellitus

Simple Summary

Multiple myeloma (MM) is a hematological malignancy characterized by an abnormal clone of plasma cells in the bone marrow. Currently, both the disease progression and its therapy are too often followed by a series of complications and the standard treatment for MM is aimed at improving the quality of life and to prolong progression-free survival (PFS), and overall survival (OS) of patients. This review looks at MM therapies from a different sight. It starts from a clear scientific background, suggesting that many malignant tumors have some common phenotype that isolates the tumor from the rest of the body. Between these phenotypes, extracellular acidity exerts a key role and data collected in the last two decades support the use of anti-acidic drugs in the treatment of cancers, including MM. Lastly, as many cancers, MM has some similarities with type II diabetes mellitus (DM) in the mechanism leading to the extracellular acidity, supporting the use of both a wide panel of proton transporters inhibitors and probably also of some anti-DM drugs in the treatment of both MM and DM.

Abstract

Multiple myeloma (MM) is a hematological malignancy with a poor prognosis while with a long and progressive outcome. To date, the therapeutic options are restricted to few drugs, including thalidomide or its derivates and autologous transplantation including stem-cell transplantation. More recently, the use of both proteasome inhibitors and monoclonal antibodies have been included in MM therapy, but the clinical results are still under evaluation. Unfortunately, death rates (within the 5-year overall survival rates) are still very high (45%), with no relevant improvement over the past 10 years. Here, we discuss data supporting a new therapeutic approach against MM, based on a common phenotype of tumor malignancies, which is the acidic microenvironment. Extracellular acidity drastically reduces the efficacy of both anti-tumor drugs and the immune reaction against tumors. Pre-clinical data have shown that anti-acidic drugs, such as proton pump inhibitors (PPIs), have a potent cytotoxic effect against human MM cells, thus supporting their use in the treatment of this malignancy. Here, we discuss also similarities between MM and type II diabetes mellitus (DM) with high risk of developing MM, suggesting that both anti-diabetic drugs and a hypocaloric diet may help in curing MM patients.

Combination Therapy of High-Dose Rabeprazole Plus Metronomic Capecitabine in Advanced Gastro-Intestinal Cancer: A Randomized Phase II Trial

Simple Summary

This is the first phase II study of high dose rabeprazole repurposing (1.5 mg/kg bid, three days a week) combined with metronomic capecitabine (mCAP), 1500 mg/daily, in gastrointestinal cancer, aimed at evaluating the activity and safety of high-dose proton pump inhibitor in combination with mCAP as salvage treatment in pretreated patients. A 3-months PFS rate of 66% and 57% was reported in the mCAP-rabeprazole and mCAP group, respectively. Although, the adjunct of high dose rabeprazole to mCAP did not improve mCAP activity, the combination of proton pump inhibitor with chemotherapy would deserve to be further investigated.

Abstract

Background: In recent years, proton pump inhibitors (PPIs) have been investigated at high-dose to modulate tumor microenvironment acidification thus restoring chemotherapeutic sensitivity. This is the first trial to study activity and safety of repurposing high dose rabeprazole combined with metronomic capecitabine (mCAP). Methods: A phase II study in which patients with gastrointestinal cancer, refractory to standard treatments, who had a life expectancy >3 months, were blind randomized 1:1 to mCAP, 1500 mg/daily, continuously with or without rabeprazole 1.5 mg/kg bid, three days a week. The primary endpoint was 3-months progression-free survival (PFS). The secondary endpoints were clinical benefit (CB) and overall survival (OS). Safety and plasma concentrations of capecitabine and its metabolites (5′-DFUR and 5-FU) were also evaluated. Results: Sixty-seven (median age 69 years; 63% male; 84% colorectal cancer, 76% ECOG-PS ≤ 1; 84% pretreated with two or more lines of chemotherapy) out of 90 patients screened for eligibility, were randomized to receive mCAP+rabeprazole (n = 32) vs. mCAP (n = 35). All patients were evaluable for response. No significant difference between mCAP+rabeprazole vs. mCAP, in terms of 3-months PFS rate (HR = 1.43, 95%CI 0.53–3.85; p = 0.477), median PFS (HR = 1.22, 95%CI 0.75–2.00, p = 0.420), CB (RR = 0.85, 95%CI 0.29–2.44; p = 0.786) and median OS (HR = 0.89, 95%CI 0.54–1.48; p = 0.664) was observed. However, a 3-year OS rate of 10% and 12% was reported in the mCAP-rabeprazole and mCAP groups, respectively. Overall, no grade 3 or 4 toxicity occurred but grade 1 or 2 adverse event of any type were more frequently in the mCAP+rabeprazole group than in the mCAP (OR 2.83, 95%CI 1.03–7.79; p = 0.043). Finally, there was not statistically significant difference in the plasma concentration of capecitabine and its metabolites between the two groups. Conclusions: Although the adjunct of high dose rabeprazole to mCAP was not shown to affect mCAP activity, as PPI are being investigated worldwide as drugs to be repositioned in cancer treatment and also considering the limited sample size as well as the favorable safety profile of the combination in the present study, further clinical investigations are desirable.

Towards an Integral Therapeutic Protocol for Breast Cancer Based upon the New H+-Centered Anticancer Paradigm of the Late Post-Warburg Era

A brand new approach to the understanding of breast cancer (BC) is urgently needed. In this contribution, the etiology, pathogenesis, and treatment of this disease is approached from the new pH-centric anticancer paradigm. Only this unitarian perspective, based upon the hydrogen ion (H+) dynamics of cancer, allows for the understanding and integration of the many dualisms, confusions, and paradoxes of the disease. The new H+-related, wide-ranging model can embrace, from a unique perspective, the many aspects of the disease and, at the same time, therapeutically interfere with most, if not all, of the hallmarks of cancer known to date. The pH-related armamentarium available for the treatment of BC reviewed here may be beneficial for all types and stages of the disease. In this vein, we have attempted a megasynthesis of traditional and new knowledge in the different areas of breast cancer research and treatment based upon the wide-ranging approach afforded by the hydrogen ion dynamics of cancer. The concerted utilization of the pH-related drugs that are available nowadays for the treatment of breast cancer is advanced.

Exosomes: A Source for New and Old Biomarkers in Cancer

Clinical oncology needs reliable tumor biomarkers to allow a follow-up of tumor patients who do not necessarily need invasive approaches. To date, the existing biomarkers are not sufficiently reliable, and many of them have generated more problems than facilitating the commitment of clinical oncologists. Over the last decades, a broad family of extracellular vesicles, with size ranging between micro to nano, has been raised as a new hope for potential sources of new tumor biomarkers. However, while knowledge in the field is increasing, we do not currently have definitive information allowing a clinical use of extracellular vesicles in cancer clinics. Recent evidence provides new perspective in clinical oncology, based on data showing that circulating nanovesicles called exosomes may represent a valuable source of tumor biomarkers. In this review, we discuss the existing clinical data supporting a key role of exosomes as a source of tumor biomarkers, including proteins and miRNAs, but also discuss the importance of the expression of known tumor biomarkers when expressed on exosomes.

Use of Acid-Suppressant Medications After Diagnosis Increases Mortality in a Subset of Gastrointestinal Cancer Patients

BACKGROUND

Acid-suppressant medications, including proton pump inhibitors (PPIs) and H₂ receptor antagonists (H₂RAs), are frequently prescribed and have been linked to increased risk of some gastrointestinal cancers.

AIMS

We examined whether post-diagnosis use of PPIs/H₂RAs is associated with the risk of mortality in gastrointestinal cancer patients.

METHODS

We used data from patients with esophageal cancer, gastric cancer, or hepatocellular carcinomas (HCCs) in the national VA Central Cancer Registry diagnosed between 2002 and 2016. We identified PPI/H₂RA prescriptions that were filled before and after cancer diagnosis and used time-dependent Cox regression models to calculate adjusted hazard ratios (HRs) and 95% CIs for mortality risk. We used a time-varying exposure to avoid immortal-time bias and a 3-month lag to reduce reverse causation. A sensitivity analysis was conducted varying the lag duration between the date of cancer diagnosis and the start of follow-up.

RESULTS

PPIs were used by the majority (54% post-diagnosis use) of patients. We found no association between post-diagnosis PPI use and cancer-specific mortality in esophageal adenocarcinoma (HR 0.93; 95% CI 0.84-1.02), esophageal squamous cell carcinoma (HR 0.99; 95% CI 0.87-1.12), or gastric cardia cancer (HR 1.04; 95% CI 0.89-1.22) patients. Post-diagnosis PPI use was, however, associated with the increased risk of cancer-specific mortality for patients with gastric non-cardia cancer (HR 1.50; 95% CI 1.29-1.74) and HCC (HR 1.31; 95% CI 1.23-1.40). The results were similar for associations with post-diagnosis use of H₂RAs. There was no association with pre-diagnosis PPI/H₂RA use.

CONCLUSION

Post-diagnosis PPI/H₂RA use was associated with the increased mortality in gastric non-cardia cancer and HCC patients.

Role of microenvironmental acidity and tumor exosomes in cancer immunomodulation

Tumor microenvironment (TME) is a complex milieu in which tumor grows, develops and progresses through a complex bi-directional cross-talk with immune-, stromal cells, and the extracellular matrix (ECM). In this context, tumor-derived exosomes (TE) drive the fate of tumor cells through a stimulatory or inhibitory role on immune system. In fact, TE can induce the apoptosis of cells of the immune surveillance, and enhance the proliferation and survival of stromal cells that sustain tumor development. However, depending on the molecular cargo, TE are also able to stimulate anti-tumor immune response. TME is mainly characterized by the acidic pH that contributes to tumor development, through multiple mechanisms. Among these, the impairment of tumor immune surveillance does occur within acidic TME, and is directly mediated by acidic pH or by molecular cargo carried by TE. Little is known about the role of TE in immunomodulation in acidic conditions. The present review summarizes the studies describing the role of microenvironmental acidity and TE in immune system modulation.

Lower Lactate Levels and Lower Intracellular pH in Patients with IDH-Mutant versus Wild-Type Gliomas

BACKGROUND AND PURPOSE

Preclinical evidence points toward a metabolic reprogramming in isocitrate dehydrogenase (IDH) mutated tumor cells with down-regulation of the expression of genes that encode for glycolytic metabolism. We noninvasively investigated lactate and Cr concentrations, as well as intracellular pH using ¹H/phosphorus 31 (³¹P) MR spectroscopy in a cohort of patients with gliomas.

MATERIALS AND METHODS

Thirty prospectively enrolled, mostly untreated patients with gliomas met the spectral quality criteria (World Health Organization II [n = 7], III [n = 16], IV [n = 7]; IDH-mutant [n = 23]; IDH wild-type [n = 7]; 1p/19q codeletion [n = 9]). MR imaging protocol included 3D ³¹P chemical shift imaging and ¹H single-voxel spectroscopy (point-resolved spectroscopy sequence at TE = 30 ms and TE = 97 ms with optimized echo spacing for detection of 2-hydroxyglutarate) from the tumor area. Values for absolute metabolite concentrations were calculated (phantom replacement method). Intracellular pH was determined from ³¹P chemical shift imaging.

RESULTS

At TE = 97 ms, lactate peaks can be fitted with little impact of lipid/macromolecule contamination. We found a significant difference in lactate concentrations, lactate/Cr ratios, and intracellular pH when comparing tumor voxels of patients with IDH-mutant with those of patients with IDH wild-type gliomas, with reduced lactate levels and near-normal intracellular pH in patients with IDH-mutant gliomas. We additionally found evidence for codependent effects of 1p/19q codeletion and IDH mutations with regard to lactate concentrations for World Health Organization tumor grades II and III, with lower lactate levels in patients exhibiting the codeletion. There was no statistical significance when comparing lactate concentrations between IDH-mutant World Health Organization II and III gliomas.

CONCLUSIONS

We found indirect evidence for metabolic reprogramming in IDH-mutant tumors with significantly lower lactate concentrations compared with IDH wild-type tumors and a near-normal intracellular pH.

Proton pump inhibitors enhance chemosensitivity, promote apoptosis, and suppress migration of breast cancer cells

Breast cancer is the most common cancer and is the leading cause of cancer deaths among women worldwide. Despite the availability of numerous therapeutics for breast cancer management, cytotoxicity and emergence of drug resistance are major challenges that limit their benefits. The acidic microenvironment surrounding tumor cells is a common feature inducing cancer cell invasiveness and chemoresistance. Proton pump inhibitors (PPIs) are one of the most commonly prescribed drugs for the treatment of acid-related conditions. PPIs have been reported to exhibit antitumorigenic effects in many cancer types. In this study, the anti-proliferative and anti-migratory effects of PPIs in three breast cancer cell lines; MCF-7, T47D, and MDA-MB-231 cells, have been investigated. In addition, the combined effects of PPIs with anticancer drugs, as well as the mechanism of PPI-mediated anti-proliferative activity were evaluated. The anti-proliferative and combined effects of PPIs were evaluated by MTT assay. Cell migration was assessed using the wound-healing assay. The mechanism of cell death was assessed using annexin V-FITC/propidium iodide staining flow cytometry method. Our results indicated that PPIs treatment significantly inhibited the growth of breast cancer cells in a dose-dependent manner. The antiproliferative activity of PPIs was significantly induced by apoptosis in all tested cell lines. The combined treatment of PPIs with doxorubicin resulted in a synergistic effect in all cell lines, whereas the combined treatment with raloxifene exhibited synergistic effect in T47D cells only and additive effects in MDA-MB-231 and MCF-7 cells. In addition, PPIs treatment significantly reduced cell migration in MDA-MB-231 cells. In conclusion, the addition of PPIs to the treatment regimen of breast cancer appears to be a promising strategy to potentiate the efficacy of chemotherapy and may suppress cancer metastasis.

Unexpected therapeutic effects of cisplatin

Cisplatin is a widely used chemotherapeutic agent that is clinically approved to fight both carcinomas and sarcomas. It has relatively high efficiency in treating ovarian cancers and metastatic testicular cancers. It is generally accepted that the major mechanism of cisplatin anti-cancer action is DNA damage. However, cisplatin is also effective in metastatic cancers and should, therefore, affect slow-cycling cancer stem cells in some way. In this review, we focused on the alternative effects of cisplatin that can support a good therapeutic response. First, attention was paid to the effects of cisplatin at the cellular level such as changes in intracellular pH and cellular mechanical properties. Alternative cellular targets of cisplatin, and the effects of cisplatin on cancer cell metabolism and ER stress were also discussed. Furthermore, the impacts of cisplatin on the tumor microenvironment and in the whole organism context were reviewed. In this review, we try to reveal possible causes of the unexpected effectiveness of this anti-cancer drug.

Extracellular Acidosis Promotes Metastatic Potency via Decrease of the BMAL1 Circadian Clock Gene in Breast Cancer

Circadian oscillation is an essential process that influences many physiological and biological mechanisms and a decrease of circadian genes is associated with many diseases such as cancer. Despite many efforts to identify the detailed mechanism for decreasing circadian genes and recovering reduced circadian genes in cancer, it is still largely unknown. We found that BMAL1 was reduced in tumor hypoxia-induced acidosis, and recovered by selectively targeting acidic pH in breast cancer cell lines. Surprisingly, BMAL1 was reduced by decrease of protein stability as well as inhibition of transcription under acidosis. In addition, melatonin significantly prevented acidosis-mediated decrease of BMAL1 by inhibiting lactate dehydrogenase-A during hypoxia. Remarkably, acidosis-mediated metastasis was significantly alleviated by BMAL1 overexpression in breast cancer cells. We therefore suggest that tumor hypoxia-induced acidosis promotes metastatic potency by decreasing BMAL1, and that tumor acidosis could be a target for preventing breast cancer metastasis by sustaining BMAL1.