Causes, consequences, and therapy of tumors acidosis

Melatonin changes energy metabolism and reduces oncogenic signaling in ovarian cancer cells

Ovarian cancer (OC) adjusts energy metabolism in favor of its progression and dissemination. Because melatonin (Mel) has antitumor actions, we investigated its impact on energy metabolism and kinase signaling in OC cells (SKOV-3 and CAISMOV-24). Cells were divided into control and Mel-treated groups, in the presence or absence of the antagonist luzindole. There was a decrease in the levels of HIF-1α, G6PDH, GAPDH, PDH, and CS after Mel treatment even in the presence of luzindole in both OC cells. Mel treatment also reduced the activity of OC-related enzymes including PFK-1, G6PDH, LDH, CS, and GS whereas PDH activity was increased. Lactate and glutamine levels dropped after Mel treatment. Mel further promoted a reduction in the concentrations of CREB, JNK, NF-kB, p-38, ERK1/2, AKT, P70S6K, and STAT in both cell lines. Mel reverses Warburg-type metabolism and possibly reduces glutaminolysis, thereby attenuating various oncogenic molecules associated with OC progression and invasion.

Metabolism-Regulating Nanozyme System for Advanced Nanocatalytic Cancer Therapy

Nanocatalytic therapy, an emerging approach in cancer treatment, utilizes nanomaterials to initiate enzyme-mimetic catalytic reactions within tumors, inducing tumor-suppressive effects. However, the targeted and selective catalysis within tumor cells is challenging yet critical for minimizing the adverse effects. The distinctive reliance of tumor cells on glycolysis generates abundant lactate, influencing the tumor's pH, which can be manipulated to selectively activate nanozymatic catalysis. Herein, small interfering ribonucleic acid (siRNA) targeting lactate transporter-mediated efflux is encapsulated within the iron-based metal-organic framework (FeMOF) and specifically delivered to tumor cells through cell membrane coating. This approach traps lactate within the cell, swiftly acidifying the tumor cytoplasm and creating an environment for boosting the catalysis of the FeMOF nanozyme. The nanozyme generates hydroxyl radical (·OH) in the reversed acidic environment, using endogenous hydrogen peroxide (H2O2) produced by mitochondria as a substrate. The induced cytoplasmic acidification disrupts calcium homeostasis, leading to mitochondrial calcium overload, resulting in mitochondrial dysfunction and subsequent tumor cell death. Additionally, the tumor microenvironment is also remodeled, inhibiting migration and invasion, thus preventing metastasis. This groundbreaking strategy combines metabolic regulation with nanozyme catalysis in a toxic drug-free approach for tumor treatment, holding promise for future clinical applications.

The dilemmas and possible solutions for CAR-T cell therapy application in solid tumors

Chimeric antigen receptor T (CAR-T) cell therapy, as an adoptive immunotherapy, is playing an increasingly important role in the treatment of malignant tumors. CAR-T cells are referred to as "living drugs" as they not only target tumor cells directly, but also induce long-term immune memory that has the potential to provide long-lasting protection. CD19.CAR-T cells have achieved complete response rates of over 90 % for acute lymphoblastic leukemia and over 60 % for non-Hodgkin's lymphoma. However, the response rate of CAR-T cells in the treatment of solid tumors remains extremely low and the side effects potentially severe. In this review, we discuss the limitations that the solid tumor microenvironment poses for CAR-T application and the solutions that are being developed to address these limitations, in the hope that in the near future, CAR-T cell therapy for solid tumors can attain the same success rates as are now being seen clinically for hematological malignancies.

A novel approach to pH-Responsive targeted cancer Therapy: Inhibition of FaDu cancer cell proliferation with a pH low insertion Peptide-Conjugated DGAT1 inhibitor

Targeting enzymes involved in lipid metabolism is increasingly recognized as a promising anticancer strategy. Efficient inhibition of diacylglycerol O-transferase 1 (DGAT1) can block fatty acid (FA) storage. This, in turn, triggers an increase in free polyunsaturated FA concentration, leading to peroxidation and ferroptosis. In this study, we report the development of a pH-sensitive peptide (pHLIP)-drug conjugate designed to selectively deliver DGAT1 inhibitors to cancer cells nested within the acidic microenvironment of tumors. We utilized two previously established pHLIP sequences for coupling with drugs. The study of DGAT1 conjugates in large unilamellar vesicles (LUVs) of different compositions did not reveal enhanced pH-dependent insertion compared to POPC LUVs. However, using in vitro 3D tumor spheroids, significant antiproliferative effects were observed upon exposure to pHLIP-T863 (DGAT1 inhibitor) conjugates, surpassing the inhibitory activity of T863 alone. In conclusion, our study provides the first evidence that pHLIP-based conjugates with DGAT1 inhibitors have the potential to specifically target the acidic compartment of tumors. Moreover, it sheds light on the limitations of LUV models in capturing the pH-dependency of such conjugates.

Modulating Nonlinear Acoustic Response of Phospholipid-Coated Microbubbles with pH for Ultrasound Imaging

Activatable microbubble contrast agents for contrast-enhanced ultrasound have a potential role for measuring physiologic and pathologic states in deep tissues, including tumor acidosis. In this study, we describe a novel observation of increased harmonic oscillation of phosphatidylcholine microbubbles (PC-MBs) in response to lower ambient pH using a clinical ultrasound scanner. MB echogenicity and nonlinear echoes were monitored at neutral and acidic pH using B-mode and Cadence contrast pulse sequencing (CPS), a harmonic imaging technique at 7.0 and 1.5 MHz. A 3-fold increase in harmonic signal intensity was observed when the pH of PC-MB suspensions was decreased from 7.4 to 5.5 to mimic normal and pathophysiological levels that can be encountered in vivo. This pH-mediated activation is tunable based on the chemical structure and length of phospholipids composing the MB shell. It is also reliant on the presence of phosphate groups, as the use of lipids without phosphate instead of phospholipids completely abrogated this phenomenon. The increased harmonic signal likely is the result of increased MB oscillation caused by a decrease of the interfacial tension induced at a lower pH, altering the lipid conformation. While relative signal changes are interpreted clinically as mostly related to blood flow, pH effects could be significant contributors, particularly when imaging tumors. While our observation can be used clinically, it requires further research to isolate the effect of pH from other variables. These findings could pave the way toward for the development of new smart ultrasound contrast agents that expand the clinical utility of contrast-enhanced ultrasound.

Acid-sensing receptor GPR4 plays a crucial role in lymphatic cancer metastasis

Cancer tissues exhibit an acidic microenvironment owing to the accumulation of protons and lactic acid produced by cancer and inflammatory cells. To examine the role of an acidic microenvironment in lymphatic cancer metastasis, gene expression profiling was conducted using human dermal lymphatic endothelial cells (HDLECs) treated with a low pH medium. Microarray and gene set enrichment analysis revealed that acid treatment induced the expression of inflammation-related genes in HDLECs, including genes encoding chemokines and adhesion molecules. Acid treatment-induced chemokines C-X3-C motif chemokine ligand 1 (CX3CL1) and C-X-C motif chemokine ligand 6 (CXCL6) autocrinally promoted the growth and tube formation of HDLECs. The expression of vascular cell adhesion molecule 1 (VCAM-1) increased in HDLECs after acid treatment in a time-dependent manner, which, in turn, enhanced their adhesion to melanoma cells. Among various acid-sensing receptors, HDLECs basally expressed G protein-coupled receptor 4 (GPR4), which was augmented under the acidic microenvironment. The induction of chemokines or VCAM-1 under acidic conditions was attenuated by GPR4 knockdown in HDLECs. In addition, lymph node metastases in a mouse melanoma model were suppressed by administering an anti-VCAM-1 antibody or a GPR4 antagonist. These results suggest that an acidic microenvironment modifies the function of lymphatic endothelial cells via GPR4, thereby promoting lymphatic cancer metastasis. Acid-sensing receptors and their downstream molecules might serve as preventive or therapeutic targets in cancer.

Design and Development of Transient Sensing Devices for Healthcare Applications

With the ever-growing requirements in the healthcare sector aimed at personalized diagnostics and treatment, continuous and real-time monitoring of relevant parameters is gaining significant traction. In many applications, health status monitoring may be carried out by dedicated wearable or implantable sensing devices only within a defined period and followed by sensor removal without additional risks for the patient. At the same time, disposal of the increasing number of conventional portable electronic devices with short life cycles raises serious environmental concerns due to the dangerous accumulation of electronic and chemical waste. An attractive solution to address these complex and contradictory demands is offered by biodegradable sensing devices. Such devices may be able to perform required tests within a programmed period and then disappear by safe resorption in the body or harmless degradation in the environment. This work critically assesses the design and development concepts related to biodegradable and bioresorbable sensors for healthcare applications. Different aspects are comprehensively addressed, from fundamental material properties and sensing principles to application-tailored designs, fabrication techniques, and device implementations. The emerging approaches spanning the last 5 years are emphasized and a broad insight into the most important challenges and future perspectives of biodegradable sensors in healthcare are provided.

Tumoral acidosis promotes adipose tissue depletion by fostering adipocyte lipolysis

OBJECTIVE

Tumour progression drives profound alterations in host metabolism, such as adipose tissue depletion, an early event of cancer cachexia. As fatty acid consumption by cancer cells increases upon acidosis of the tumour microenvironment, we reasoned that fatty acids derived from distant adipose lipolysis may sustain tumour fatty acid craving, leading to the adipose tissue loss observed in cancer cachexia.

METHODS

To evaluate the pro-lipolytic capacities of acid-exposed cancer cells, primary mouse adipocytes from subcutaneous and visceral adipose tissue were exposed to pH-matched conditioned medium from human and murine acid-exposed cancer cells (pH 6.5), compared to naive cancer cells (pH 7.4). To further address the role of tumoral acidosis on adipose tissue loss, a pH-low insertion peptide was injected into tumour-bearing mice, and tumoral acidosis was neutralised with a sodium bicarbonate buffer. Prolipolytic mediators were identified by transcriptomic approaches and validated on murine and human adipocytes.

RESULTS

Here, we reveal that acid-exposed cancer cells promote lipolysis from subcutaneous and visceral adipocytes and that dampening acidosis in vivo inhibits adipose tissue depletion. We further found a set of well-known prolipolytic factors enhanced upon acidosis adaptation and unravelled a role for β-glucuronidase (GUSB) as a promising new actor in adipocyte lipolysis.

CONCLUSIONS

Tumoral acidosis promotes the mobilization of fatty acids derived from adipocytes via the release of soluble factors by cancer cells. Our work paves the way for therapeutic approaches aimed at tackling cachexia by targeting the tumour acidic compartment.

Tumor microenvironment reprogramming by nanomedicine to enhance the effect of tumor immunotherapy

With the rapid development of the fields of tumor biology and immunology, tumor immunotherapy has been used in clinical practice and has demonstrated significant therapeutic potential, particularly for treating tumors that do not respond to standard treatment options. Despite its advances, immunotherapy still has limitations, such as poor clinical response rates and differences in individual patient responses, largely because tumor tissues have strong immunosuppressive microenvironments. Many tumors have a tumor microenvironment (TME) that is characterized by hypoxia, low pH, and substantial numbers of immunosuppressive cells, and these are the main factors limiting the efficacy of antitumor immunotherapy. The TME is crucial to the occurrence, growth, and metastasis of tumors. Therefore, numerous studies have been devoted to improving the effects of immunotherapy by remodeling the TME. Effective regulation of the TME and reversal of immunosuppressive conditions are effective strategies for improving tumor immunotherapy. The use of multidrug combinations to improve the TME is an efficient way to enhance antitumor immune efficacy. However, the inability to effectively target drugs decreases therapeutic effects and causes toxic side effects. Nanodrug delivery carriers have the advantageous ability to enhance drug bioavailability and improve drug targeting. Importantly, they can also regulate the TME and deliver large or small therapeutic molecules to decrease the inhibitory effect of the TME on immune cells. Therefore, nanomedicine has great potential for reprogramming immunosuppressive microenvironments and represents a new immunotherapeutic strategy. Therefore, this article reviews strategies for improving the TME and summarizes research on synergistic nanomedicine approaches that enhance the efficacy of tumor immunotherapy.

On the Importance of Acidity in Cancer Cells and Therapy

Cancer cells are associated with high glycolytic activity, which results in acidification of the tumor microenvironment. The occurrence of this stressful condition fosters tumor aggressiveness, with the outcome of invasiveness and metastasis that are linked to a poor clinical prognosis. Acidosis can be both the cause or consequence of alterations in the functions and expressions of transporters involved in intracellular acidity regulation. This review aims to explore the origin of acidity in cancer cells and the various mechanisms existing in tumors to resist, survive, or thrive in the acidic environment. It highlights the difficulties in measuring the intracellular pH evolution that impedes our understanding of the many regulatory and feedback mechanisms. It finally presents the consequences of acidity on tumor development as well as the friend or foe role of acidity in therapy.

Lysosomal enzyme trafficking: from molecular mechanisms to human diseases

Lysosomes degrade and recycle macromolecules that are delivered through the biosynthetic, endocytic, and autophagic routes. Hydrolysis of the different classes of macromolecules is catalyzed by about 70 soluble enzymes that are transported from the Golgi apparatus to lysosomes in a mannose 6-phosphate (M6P)-dependent process. The molecular machinery that generates M6P tags for receptor-mediated targeting of lysosomal enzymes was thought to be understood in detail. However, recent studies on the M6P pathway have identified a previously uncharacterized core component, yielded structural insights in known components, and uncovered functions in various human diseases. Here we review molecular mechanisms of lysosomal enzyme trafficking and discuss its relevance for rare lysosomal disorders, cancer, and viral infection.

Carfilzomib-Loaded Ternary Polypeptide Nanoparticles Stabilized by Polycationic Complexation

Carfilzomib (CFZ) is a second-generation proteasome inhibitor showing great efficacy in multiple myeloma treatment, yet its clinical applications for other diseases such as solid cancers are limited due to low aqueous solubility and poor biostability. Ternary polypeptide nanoparticles (tPNPs) are drug carriers that we previously reported to overcome these pharmaceutical limitations by entrapping CFZ in the core of the nanoparticles and protecting the drugs from degradation in biological media. However, preclinical studies revealed that tPNPs would require further improvement in particle stability to suppress initial burst drug release and thus achieve prolonged inhibition of proteasome activity with CFZ against tumor cells in vivo. In this study, CFZ-loaded tPNPs are stabilized by polycations which have varying pKa values and thus differently modulate nanoparticle stability in response to solution pH. Through polyion complexation, the polycations appeared to stabilize the core of tPNPs entrapping CFZ-cyclodextrin inclusion complexes while allowing for uniform particle size before and after freeze drying. Interestingly, CFZ-loaded tPNPs (CFZ/tPNPs) showed pH-dependent drug release kinetics, which accelerated CFZ release as solution acidity increased (pH < 6) without compromising particle stability at the physiological condition (pH 7.4). In vitro cytotoxicity and proteasome activity assays confirmed that tPNPs stabilized with cationic polymers improved bioactivity of CFZ against CFZ-resistant cancer cells, which would be greatly beneficial in combination with pH-dependent drug release for treatment of solid cancers with drug resistance and tumor microenvironment acidosis by using CFZ and other proteasome inhibitors.

Sensitive simultaneous measurements of oxygenation and extracellular pH by EPR using a stable monophosphonated trityl radical and lithium phthalocyanine

The monitoring of acidosis and hypoxia is crucial because both factors promote cancer progression and impact the efficacy of anti-cancer treatments. A phosphonated tetrathiatriarylmethyl (pTAM) has been previously described to monitor both parameters simultaneously, but the sensitivity to tackle subtle changes in oxygenation was limited. Here, we describe an innovative approach combining the pTAM radical and lithium phthalocyanine (LiPc) crystals to provide sensitive simultaneous measurements of extracellular pH (pHe) and pO2. Both parameters can be measured simultaneously as both EPR spectra do not overlap, with a gain in sensitivity to pO2 variations by a factor of 10. This procedure was applied to characterize the impact of carbogen breathing in a breast cancer 4T1 model as a proof-of-concept. No significant change in pHe and pO2 was observed using pTAM alone, while LiPc detected a significant increase in tumor oxygenation. Interestingly, we observed that pTAM systematically overestimated the pO2 compared to LiPc. In addition, we analyzed the impact of an inhibitor (UK-5099) of the mitochondrial pyruvate carrier (MPC) on the tumor microenvironment. In vitro, the exposure of 4T1 cells to UK-5099 for 24 h induced a decrease in pHe and oxygen consumption rate (OCR). In vivo, a significant decrease in tumor pHe was observed in UK-5099-treated mice, while there was no change for mice treated with the vehicle. Despite the change observed in OCR, no significant change in tumor oxygenation was observed after the UK-5099 treatment. This approach is promising for assessing in vivo the effect of treatments targeting tumor metabolism.

Metabolic challengers selecting tumor-persistent cells

Resistance to anticancer therapy still represents one of the main obstacles to cancer treatment. Numerous components of the tumor microenvironment (TME) contribute significantly to the acquisition of drug resistance. Microenvironmental pressures arising during cancer evolution foster tumor heterogeneity (TH) and facilitate the emergence of drug-resistant clones. In particular, metabolic pressures arising in the TME may favor epigenetic adaptations supporting the acquisition of persistence features in tumor cells. Tumor-persistent cells (TPCs) are characterized by high phenotypic and metabolic plasticity, representing a noticeable advantage in chemo- and radio-resistance. Understanding the crosslink between the evolution of metabolic pressures in the TME, epigenetics, and TPC evolution is significant for developing novel therapeutic strategies specifically targeting TPC vulnerabilities to overcome drug resistance.

Tumor acidosis-induced DNA damage response and tetraploidy enhance sensitivity to ATM and ATR inhibitors

Tumor acidosis is associated with increased invasiveness and drug resistance. Here, we take an unbiased approach to identify vulnerabilities of acid-exposed cancer cells by combining pH-dependent flow cytometry cell sorting from 3D colorectal tumor spheroids and transcriptomic profiling. Besides metabolic rewiring, we identify an increase in tetraploid cell frequency and DNA damage response as consistent hallmarks of acid-exposed cancer cells, supported by the activation of ATM and ATR signaling pathways. We find that regardless of the cell replication error status, both ATM and ATR inhibitors exert preferential growth inhibitory effects on acid-exposed cancer cells. The efficacy of a combination of these drugs with 5-FU is further documented in 3D spheroids as well as in patient-derived colorectal tumor organoids. These data position tumor acidosis as a revelator of the therapeutic potential of DNA repair blockers and as an attractive clinical biomarker to predict the response to a combination with chemotherapy.

L-DOS47 Elevates Pancreatic Cancer Tumor pH and Enhances Response to Immunotherapy

Acidosis is an important immunosuppressive mechanism that leads to tumor growth. Therefore, we investigated the neutralization of tumor acidity to improve immunotherapy response. L-DOS47, a new targeted urease immunoconjugate designed to neutralize tumor acidity, has been well tolerated in phase I/IIa trials. L-DOS47 binds to CEACAM6, a cell-surface protein that is highly expressed in gastrointestinal cancers, allowing urease to cleave endogenous urea into two NH4+ and one CO2, thereby raising local pH. To test the synergetic effect of neutralizing tumor acidity with immunotherapy, we developed a pancreatic orthotopic murine tumor model (KPC961) expressing human CEACAM6. Using chemical exchange saturation transfer-magnetic resonance imaging (CEST-MRI) to measure the tumor extracellular pH (pHe), we confirmed that L-DOS47 raises the tumor pHe from 4 h to 96 h post injection in acidic tumors (average increase of 0.13 units). Additional studies showed that combining L-DOS47 with anti-PD1 significantly increases the efficacy of the anti-PD1 monotherapy, reducing tumor growth for up to 4 weeks.

ASIC1a contributes to the epithelial-mesenchymal transformation of breast cancer by activating the Ca2+ /β-catenin pathway

Breast cancer is the most common cancer in the world, with metastasis being one of the leading causes of death among patients. The acidic environment of breast cancer tissue promotes tumor cell invasion and migration by inducing epithelial-mesenchymal transformation (EMT) in tumor cells, but the exact mechanisms are not yet fully understood. This study investigated the expression of acid-sensitive ion channel 1a (ASIC1a) in breast cancer tissue samples and explored the mechanisms by which ASIC1a mediates the promotion of EMT in breast cancer cells in an acidic microenvironment through in vivo and in vitro experiments. The results showed that first, the expression of ASIC1a was significantly upregulated in breast cancer tissue and was correlated with the TNM (tumor node metastasis) staging of breast cancer. Furthermore, ASIC1a expression was higher in tumors with lymph node metastasis than in those without. Second, the acidic microenvironment promoted [Ca2+ ]i influx via ASIC1a activation and regulated the expression of β-catenin, Vimentin, and E-cadherin, thus promoting EMT in breast cancer cells. Inhibition of ASIC1a activation with PcTx-1 could suppress EMT in breast cancer cells. Finally, in vivo studies also showed that inhibition of ASIC1a could reduce breast cancer metastasis, invasion, and EMT. This study suggests that ASIC1a expression is associated with breast cancer staging and metastasis. Therefore, ASIC1a may become a new breast cancer biomarker, and the elucidation of the mechanism by which ASIC1a promotes EMT in breast cancer under acidic microenvironments provides evidence for the use of ASIC1a as a molecular target for breast cancer treatment.

The Role of Ion-Transporting Proteins in Human Disease

This Special Issue focuses on the significance of ion-transporting proteins, such as ion channels and transporters, providing evidence for their significant contribution to bodily and cellular functions via the regulation of signal transduction and ionic environments [...].

Glioblastoma multiforme influence on the elemental homeostasis of the distant organs: the results of inter-comparison study carried out with TXRF method

Glioblastoma (GBM) is a fast-growing and aggressive brain tumor which invades the nearby brain tissue but generally does not spread to the distant organs. Nonetheless, if untreated, GBM can result in patient death in time even less than few months from the diagnosis. The influence of the tumor progress on organs other than brain is obvious but still not well described. Therefore, we examined the elemental abnormalities appearing in selected body organs (kidney, heart, spleen, lung) in two rat models of GBM. The animals used for the study were subjected to the implantation of human GBM cell lines (U87MG and T98G) characterized by different levels of invasiveness. The elemental analysis of digested organ samples was carried out using the total reflection X-ray fluorescence (TXRF) method, independently, in three European laboratories utilizing various commercially available TXRF spectrometers. The comparison of the data obtained for animals subjected to T98G and U87MG cells implantation showed a number of elemental anomalies in the examined organs. What is more, the abnormalities were found for rats even if neoplastic tumor did not develop in their brains. The most of alterations for both experimental groups were noted in the spleen and lungs, with the direction of the found element changes in these organs being the opposite. The observed disorders of element homeostasis may result from many processes occurring in the animal body as a result of implantation of cancer cells or the development of GBM, including inflammation, anemia of chronic disease or changes in iron metabolism. Tumor induced changes in organ elemental composition detected in cooperating laboratories were usually in a good agreement. In case of elements with higher atomic numbers (Fe, Cu, Zn and Se), 88% of the results were classified as fully compliant. Some discrepancies between the laboratories were found for lighter elements (P, S, K and Ca). However, also in this case, the obtained results fulfilled the requirements of full (the results from three laboratories were in agreement) or partial agreement (the results from two laboratories were in agreement).

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.

Acidosis promotes the metastatic colonization of lung cancer via remodeling of the extracellular matrix and vasculogenic mimicry

Acidosis is a hallmark of the tumor microenvironment caused by the metabolic switch from glucose oxidative phosphorylation to glycolysis. It has been associated with tumor growth and progression; however, the precise mechanism governing how acidosis promotes metastatic dissemination has yet to be elucidated. In the present study, a long‑term acidosis model was established using patient‑derived lung cancer cells, to identify critical components of metastatic colonization via transcriptome profiling combined with both in vitro and in vivo functional assays, and association analysis using clinical samples. Xenograft inoculates of 1 or 10 acidotic cells mimicking circulating tumor cell clusters were shown to exhibit increased tumor incidence compared with their physiological pH counterparts. Transcriptomics revealed that profound remodeling of the extracellular matrix (ECM) occurred in the acidotic cells, including upregulation of the integrin subunit α‑4 (ITGA4) gene. In clinical lung cancer, ITGA4 expression was found to be upregulated in primary tumors with metastatic capability, and this trait was retained in the corresponding secondary tumors. Expression of ITGA4 was markedly upregulated around the vasculogenic mimicry structures of the acidotic tumors, while acidotic cells exhibited a higher ability of vasculogenic mimicry in vitro. Acidosis was also found to induce the enrichment of side population cells, suggesting an enhanced resistance to noxious attacks of the tumor microenvironment. Taken together, these results demonstrated that acidosis actively contributed to tumor metastatic colonization, and novel mechanistic insights into the therapeutic management and prognosis of lung cancer were discussed.

Physiological roles of chloride ions in bodily and cellular functions

Physiological roles of Cl-, a major anion in the body, are not well known compared with those of cations. This review article introduces: (1) roles of Cl- in bodily and cellular functions; (2) the range of cytosolic Cl- concentration ([Cl-]c); (3) whether [Cl-]c could change with cell volume change under an isosmotic condition; (4) whether [Cl-]c could change under conditions where multiple Cl- transporters and channels contribute to Cl- influx and efflux in an isosmotic state; (5) whether the change in [Cl-]c could be large enough to act as signals; (6) effects of Cl- on cytoskeletal tubulin polymerization through inhibition of GTPase activity and tubulin polymerization-dependent biological activity; (7) roles of cytosolic Cl- in cell proliferation; (8) Cl--regulatory mechanisms of ciliary motility; (9) roles of Cl- in sweet/umami taste receptors; (10) Cl--regulatory mechanisms of with-no-lysine kinase (WNK); (11) roles of Cl- in regulation of epithelial Na+ transport; (12) relationship between roles of Cl- and H+ in body functions.

Improving combination therapies: targeting A2B-adenosine receptor to modulate metabolic tumor microenvironment and immunosuppression

BACKGROUND

We investigated the role of A2B-adenosine receptor in regulating immunosuppressive metabolic stress in the tumor microenvironment. Novel A2B-adenosine receptor antagonist PBF-1129 was tested for antitumor activity in mice and evaluated for safety and immunologic efficacy in a phase I clinical trial of patients with non-small cell lung cancer.

METHODS

The antitumor efficacy of A2B-adenosine receptor antagonists and their impact on the metabolic and immune tumor microenvironment were evaluated in lung, melanoma, colon, breast, and epidermal growth factor receptor-inducible transgenic cancer models. Employing electron paramagnetic resonance, we assessed changes in tumor microenvironment metabolic parameters, including pO2, pH, and inorganic phosphate, during tumor growth and evaluated the immunologic effects of PBF-1129, including its pharmacokinetics, safety, and toxicity, in patients with non-small cell lung cancer.

RESULTS

Levels of metabolic stress correlated with tumor growth, metastasis, and immunosuppression. Tumor interstitial inorganic phosphate emerged as a correlative and cumulative measure of tumor microenvironment stress and immunosuppression. A2B-adenosine receptor inhibition alleviated metabolic stress, downregulated expression of adenosine-generating ectonucleotidases, increased expression of adenosine deaminase, decreased tumor growth and metastasis, increased interferon γ production, and enhanced the efficacy of antitumor therapies following combination regimens in animal models (anti-programmed cell death 1 protein vs anti-programmed cell death 1 protein plus PBF-1129 treatment hazard ratio = 11.74 [95% confidence interval = 3.35 to 41.13], n = 10, P < .001, 2-sided F test). In patients with non-small cell lung cancer, PBF-1129 was well tolerated, with no dose-limiting toxicities; demonstrated pharmacologic efficacy; modulated the adenosine generation system; and improved antitumor immunity.

CONCLUSIONS

Data identify A2B-adenosine receptor as a valuable therapeutic target to modify metabolic and immune tumor microenvironment to reduce immunosuppression, enhance the efficacy of immunotherapies, and support clinical application of PBF-1129 in combination therapies.

Acidity-Responsive Nanoreactors Destructed "Warburg Effect" for Toxic-Acidosis and Starvation Synergistic Therapy

"Warburg Effect" shows that most tumor cells rely on aerobic glycolysis for energy supply, leading to malignant energy deprivation and an "internal alkaline external acid" tumor microenvironment. Destructing the "Warburg Effect" is an effective approach to inhibit tumor progression. Herein, an acidity-responsive nanoreactor (Au@CaP-Flu@HA) is fabricated for toxic acidosis and starvation synergistic therapy. In the nanoreactor, the fluvastatin (Flu) could reduce lactate efflux by inhibiting the lactate-proton transporter (monocarboxylate transporters, MCT4), resulting in intracellular lactate accumulation. Meanwhile, the glucose oxidase-mimic Au-nanocomposite consumes glucose to induce cell starvation accompanied by gluconic acid production, coupling with lactate to exacerbate toxic acidosis. Also, the up-regulated autophagic energy supply of tumor cells under energy deprivation and hypoxia aggravation is blocked by autophagy inhibitor CaP. Cellular dysfunction under pHi acidification and impaired Adenosine Triphosphate (ATP) synthesis under starvation synergistically promote tumor cell apoptosis. Both in vitro and in vivo studies demonstrate that this combinational approach of toxic-acidosis/starvation therapy could effectively destruct the "Warburg Effect" to inhibit tumor growth and anti-metastatic effects.

The antagonist of β-adrenergic receptor propranolol inhibits T cell lymphoma growth and enhances antitumor efficacy of cisplatin in vivo: A role of modulated apoptosis, glucose metabolism, pH regulation, and antitumor immune response

Accumulating evidence has shown a vital role of stress-regulatory hormones, including epinephrine, in the progression of numerous cancers, including T cell lymphoma. Further, the antitumor and chemosensitizing potential of propranolol, an inexpensive β-adrenergic receptor antagonist has also been reported against breast, colon, ovarian, and pancreatic cancers. However, in vivo antitumor and chemopotentiating activity of propranolol have not yet been examined against malignancies of hematological origin, including T cell lymphoma. Therefore, the present study is designed to evaluate the antitumor and chemopotentiating action of propranolol in a T cell lymphoma murine model. In this study, T cell lymphoma-bearing mice were treated with vehicle alone (PBS) or containing propranolol followed by administration of with or without cisplatin. The progression of the tumor was assessed along with analysis of tumor cell apoptosis, glucose metabolism, pH regulation, and antitumor immune response. The apoptosis was estimated by cellular and nuclear morphology analysis through Wright-Giemsa, annexin-V, and DAPI staining. ELISA was used to detect the epinephrine level in serum. The glucose, lactate, and NO levels were measured in the tumor ascitic fluid by calorimetric methods. RT-PCR and Western blot were used to assess the levels of various crucial regulators at gene and protein levels, respectively. Our results showed that propranolol exerts antitumor as well as chemopotentiating ability in DL-bearing mice by altering apoptosis, glycolysis, acidification of TME, and immunosuppression.

Unlocking the potential of the tumor microenvironment for cancer therapy

The tumor microenvironment (TME) holds a crucial role in the progression of cancer. Epithelial-derived tumors share common traits in shaping the TME. The Warburg effect is a notable phenomenon wherein tumor cells exhibit resistance to apoptosis and an increased reliance on anaerobic glycolysis for energy production. Recognizing the pivotal role of the TME in controlling tumor growth and influencing responses to chemotherapy, researchers have focused on developing potential cancer treatment strategies. A wide array of therapies, including immunotherapies, antiangiogenic agents, interventions targeting cancer-associated fibroblasts (CAF), and therapies directed at the extracellular matrix, have been under investigation and have demonstrated efficacy. Additionally, innovative techniques such as tumor tissue explants, "tumor-on-a-chip" models, and multicellular tumor spheres have been explored in laboratory research. This comprehensive review aims to provide insights into the intricate cross-talk between cancer-associated signaling pathways and the TME in cancer progression, current therapeutic approaches targeting the TME, the immune landscape within solid tumors, the role of the viral TME, and cancer cell metabolism.

Warburg-associated acidification represses lactic fermentation independently of lactate, contribution from real-time NMR on cell-free systems

Lactate accumulation and acidification in tumours are a cancer hallmark associated with the Warburg effect. Lactic acidosis correlates with cancer malignancy, and the benefit it offers to tumours has been the subject of numerous hypotheses. Strikingly, lactic acidosis enhances cancer cell survival to environmental glucose depletion by repressing high-rate glycolysis and lactic fermentation, and promoting an oxidative metabolism involving reactivated respiration. We used real-time NMR to evaluate how cytosolic lactate accumulation up to 40 mM and acidification up to pH 6.5 individually impact glucose consumption, lactate production and pyruvate evolution in isolated cytosols. We used a reductive cell-free system (CFS) to specifically study cytosolic metabolism independently of other Warburg-regulatory mechanisms found in the cell. We assessed the impact of lactate and acidification on the Warburg metabolism of cancer cytosols, and whether this effect extended to different cytosolic phenotypes of lactic fermentation and cancer. We observed that moderate acidification, independently of lactate concentration, drastically reduces the glucose consumption rate and halts lactate production in different lactic fermentation phenotypes. In parallel, for Warburg-type CFS lactate supplementation induces pyruvate accumulation at control pH, and can maintain a higher cytosolic pyruvate pool at low pH. Altogether, we demonstrate that intracellular acidification accounts for the direct repression of lactic fermentation by the Warburg-associated lactic acidosis.

ADP-Ribosylation Factor 6 Pathway Acts as a Key Executor of Mesenchymal Tumor Plasticity

Despite the "big data" on cancer from recent breakthroughs in high-throughput technology and the development of new therapeutic modalities, it remains unclear as to how intra-tumor heterogeneity and phenotypic plasticity created by various somatic abnormalities and epigenetic and metabolic adaptations orchestrate therapy resistance, immune evasiveness, and metastatic ability. Tumors are formed by various cells, including immune cells, cancer-associated fibroblasts, and endothelial cells, and their tumor microenvironment (TME) plays a crucial role in malignant tumor progression and responses to therapy. ADP-ribosylation factor 6 (ARF6) and AMAP1 are often overexpressed in cancers, which statistically correlates with poor outcomes. The ARF6-AMAP1 pathway promotes the intracellular dynamics and cell-surface expression of various proteins. This pathway is also a major target for KRAS/TP53 mutations to cooperatively promote malignancy in pancreatic ductal adenocarcinoma (PDAC), and is closely associated with immune evasion. Additionally, this pathway is important in angiogenesis, acidosis, and fibrosis associated with tumor malignancy in the TME, and its inhibition in PDAC cells results in therapeutic synergy with an anti-PD-1 antibody in vivo. Thus, the ARF6-based pathway affects the TME and the intrinsic function of tumors, leading to malignancy. Here, we discuss the potential mechanisms of this ARF6-based pathway in tumorigenesis, and novel therapeutic strategies.

Increasing Chemotherapeutic Efficacy Using pH-Modulating and Doxorubicin-Releasing Injectable Chitosan-Poly(ethylene glycol) Hydrogels

Modulation of pH is crucial to maintaining the chemical homeostasis of biological environments. The irregular metabolic pathways exhibited by cancer cells result in the production of acidic byproducts that are excreted and accumulate in the extracellular tumor microenvironment, reducing the pH. As a consequence of the lower pH in tumors, cancer cells increase the expression of metastatic phenotypes and chemotherapeutic resistance. A significant limitation in current cancer therapies is the inability to locally deliver chemotherapeutics, leading to significant damage to healthy cells in systemic administration. To overcome these challenges, we present an injectable chitosan-poly(ethylene glycol) hydrogel that is dual-loaded with doxorubicin and sodium bicarbonate providing alkaline buffering of extracellular acidity and simultaneous chemotherapeutic delivery to increase chemotherapeutic efficacy. We conducted in vitro studies of weak base chemotherapeutic and alkaline buffer release from the hydrogel. The release of doxorubicin from hydrogels increased in a low-pH environment and was dependent on the encapsulated sodium bicarbonate concentration. We investigated the influence of pH on the doxorubicin efficacy and viability of MCF-7 and MDA-MB-231 breast cancer cell lines. The results show a 2- to 3-fold increase in IC50 values from neutral pH to low pH, showing decreased cancer cell viability at neutral pH as compared to acidic pH. The IC50 results were shown to correlate with a decrease in intracellular uptake of doxorubicin at low pH. The proposed hydrogels were confirmed to be nontoxic to healthy MCF-10A mammary epithelial cells. Rheological studies were performed to verify that the dual-loaded hydrogels were injectable. The mechanical and release properties of the hydrogels were maintained after extended storage. The chemotherapeutic activity of doxorubicin was evaluated in the presence of the proposed pH-regulating hydrogels. The findings suggest a promising nontoxic, biodegradable hydrogel buffer delivery system that can achieve two simultaneous important goals of local acidosis neutralization and chemotherapeutic release.

How to 19F MRI: applications, technique, and getting started

Magnetic resonance imaging (MRI) plays a significant role in the routine imaging workflow, providing both anatomical and functional information. 19F MRI is an evolving imaging modality where instead of 1H, 19F nuclei are excited. As the signal from endogenous 19F in the body is negligible, exogenous 19F signals obtained by 19F radiofrequency coils are exceptionally specific. Highly fluorinated agents targeting particular biological processes (i.e., the presence of immune cells) have been visualised using 19F MRI, highlighting its potential for non-invasive and longitudinal molecular imaging. This article aims to provide both a broad overview of the various applications of 19F MRI, with cancer imaging as a focus, as well as a practical guide to 19F imaging. We will discuss the essential elements of a 19F system and address common pitfalls during acquisition. Last but not least, we will highlight future perspectives that will enhance the role of this modality. While not an exhaustive exploration of all 19F literature, we endeavour to encapsulate the broad themes of the field and introduce the world of 19F molecular imaging to newcomers. 19F MRI bridges several domains, imaging, physics, chemistry, and biology, necessitating multidisciplinary teams to be able to harness this technology effectively. As further technical developments allow for greater sensitivity, we envision that 19F MRI can help unlock insight into biological processes non-invasively and longitudinally.

Unravelling the Glioblastoma Tumour Microenvironment: Can Aptamer Targeted Delivery Become Successful in Treating Brain Cancers?

The key challenges to treating glioblastoma multiforme (GBM) are the heterogeneous and complex nature of the GBM tumour microenvironment (TME) and difficulty of drug delivery across the blood-brain barrier (BBB). The TME is composed of various neuronal and immune cells, as well as non-cellular components, including metabolic products, cellular interactions, and chemical compositions, all of which play a critical role in GBM development and therapeutic resistance. In this review, we aim to unravel the complexity of the GBM TME, evaluate current therapeutics targeting this microenvironment, and lastly identify potential targets and therapeutic delivery vehicles for the treatment of GBM. Specifically, we explore the potential of aptamer-targeted delivery as a successful approach to treating brain cancers. Aptamers have emerged as promising therapeutic drug delivery vehicles with the potential to cross the BBB and deliver payloads to GBM and brain metastases. By targeting specific ligands within the TME, aptamers could potentially improve treatment outcomes and overcome the challenges associated with larger therapies such as antibodies.

Characterization of the metabolic alteration-modulated tumor microenvironment mediated by TP53 mutation and hypoxia

BACKGROUND

TP53 mutation and hypoxia play an essential role in cancer progression. However, the metabolic reprogramming and tumor microenvironment (TME) heterogeneity mediated by them are still not fully understood.

METHODS

The multi-omics data of 32 cancer types and immunotherapy cohorts were acquired to comprehensively characterize the metabolic reprogramming pattern and the TME across cancer types and explore immunotherapy candidates. An assessment model for metabolic reprogramming was established by integration of multiple machine learning methods, including lasso regression, neural network, elastic network, and survival support vector machine (SVM). Pharmacogenomics analysis and in vitro assay were conducted to identify potential therapeutic drugs.

RESULTS

First, we identified metabolic subtype A (hypoxia-TP53 mutation subtype) and metabolic subtype B (non-hypoxia-TP53 wildtype subtype) in hepatocellular carcinoma (HCC) and showed that metabolic subtype A had an "immune inflamed" microenvironment. Next, we established an assessment model for metabolic reprogramming, which was more effective compared to the traditional prognostic indicators. Then, we identified a potential targeting drug, teniposide. Finally, we performed the pan-cancer analysis to illustrate the role of metabolic reprogramming in cancer and found that the metabolic alteration (MA) score was positively correlated with tumor mutational burden (TMB), neoantigen load, and homologous recombination deficiency (HRD) across cancer types. Meanwhile, we demonstrated that metabolic reprogramming mediated a potential immunotherapy-sensitive microenvironment in bladder cancer and validated it in an immunotherapy cohort.

CONCLUSION

Metabolic alteration mediated by hypoxia and TP53 mutation is associated with TME modulation and tumor progression across cancer types. In this study, we analyzed the role of metabolic alteration in cancer and propose a predictive model for cancer prognosis and immunotherapy responsiveness. We also explored a potential therapeutic drug, teniposide.

Interactions between microglia and glioma in tumor microenvironment

Gliomas, the most prevalent primary tumors in the central nervous system, are marked by their immunosuppressive properties and consequent poor patient prognosis. Current evidence emphasizes the pivotal role of the tumor microenvironment in the progression of gliomas, largely attributed to tumor-associated macrophages (brain-resident microglia and bone marrow-derived macrophages) that create a tumor microenvironment conducive to the growth and invasion of tumor cells. Yet, distinguishing between these two cell subgroups remains a challenge. Thus, our review starts by analyzing the heterogeneity between these two cell subsets, then places emphasis on elucidating the complex interactions between microglia and glioma cells. Finally, we conclude with a summary of current attempts at immunotherapy that target microglia. However, given that independent research on microglia is still in its initial stages and has many shortcomings at the present time, we express our related concerns and hope that further research will be carried out to address these issues in the future.

L-DOS47 enhances response to immunotherapy in pancreatic cancer tumor

Acidosis is an important immunosuppressive mechanism that leads to tumor growth. Therefore, we investigated the neutralization of tumor acidity to improve immunotherapy response. L-DOS47, a new targeted urease immunoconjugate designed to neutralize tumor acidity, has been well tolerated in phase I/IIa trials. L-DOS47 binds CEACAM6, a cell surface protein highly expressed in gastrointestinal cancers, allowing urease to cleave endogenous urea into two NH4+ and one CO2, thereby raising local pH. To test the synergetic effect of neutralizing tumor acidity with immunotherapy, we developed a pancreatic orthotopic murine tumor model (KPC961) expressing human CEACAM6. Our results demonstrate that combining L DOS47 with anti-PD1 significantly increases the efficacy of anti-PD1 monotherapy, reducing tumor growth for up to 4 weeks.

Cellular Adaptation Takes Advantage of Atavistic Regression Programs during Carcinogenesis

Adaptation of cancer cells to extreme microenvironmental conditions (i.e., hypoxia, high acidity, and reduced nutrient availability) contributes to cancer resilience. Furthermore, neoplastic transformation can be envisioned as an extreme adaptive response to tissue damage or chronic injury. The recent Systemic-Evolutionary Theory of the Origin of Cancer (SETOC) hypothesizes that cancer cells "revert" to "primitive" characteristics either ontogenically (embryo-like) or phylogenetically (single-celled organisms). This regression may confer robustness and maintain the disordered state of the tissue, which is a hallmark of malignancy. Changes in cancer cell metabolism during adaptation may also be the consequence of altered microenvironmental conditions, often resulting in a shift toward lactic acid fermentation. However, the mechanisms underlying the robust adaptive capacity of cancer cells remain largely unknown. In recent years, cancer cells' metabolic flexibility has received increasing attention among researchers. Here, we focus on how changes in the microenvironment can affect cancer cell energy production and drug sensitivity. Indeed, changes in the cellular microenvironment may lead to a "shift" toward "atavistic" biologic features, such as the switch from oxidative phosphorylation (OXPHOS) to lactic acid fermentation, which can also sustain drug resistance. Finally, we point out new integrative metabolism-based pharmacological approaches and potential biomarkers for early detection.

Acidosis-induced regulation of adipocyte G0S2 promotes crosstalk between adipocytes and breast cancer cells as well as tumor progression

Bidirectional interactions between cancer cells and their microenvironment govern tumor progression. Among the stromal cells in this microenvironment, adipocytes have been reported to upregulate cancer cell migration and invasion by producing fatty acids. Conversely, cancer cells alter adipocyte phenotype notably via increased lipolysis. We aimed to identify the mechanisms through which cancer cells trigger adipocyte lipolysis and evaluate the functional consequences on cancer progression. Here, we show that cancer cell-induced acidification of the extracellular medium strongly promotes preadipocyte lipolysis through a mechanism that does not involve lipophagy but requires adipose triglyceride lipase (ATGL) activity. This increased lipolysis is triggered mainly by attenuation of the G0/G1 switch gene 2 (G0S2)-induced inhibition of ATGL. G0S2-mediated regulation in preadipocytes affects their communication with breast cancer cells, modifying the phenotype of the cancer cells and increasing their resistance to chemotherapeutic agents in vitro. Furthermore, we demonstrate that the adipocyte-specific overexpression of G0S2 impairs mammary tumor growth and lung metastasis formation in vivo. Our results highlight the importance of acidosis in cancer cell-adipocyte crosstalk and identify G0S2 as the main regulator of cancer-induced lipolysis, regulating tumor establishment and spreading.

ECM Composition Differentially Regulates Intracellular and Extracellular pH in Normal and Cancer Pancreatic Duct Epithelial Cells

Intracellular pH (pHi) regulation is a challenge for the exocrine pancreas, where the luminal secretion of bicarbonate-rich fluid is accompanied by interstitial flows of acid. This acid-base transport requires a plethora of ion transporters, including bicarbonate transporters and the Na⁺/H⁺ exchanger isoform 1 (NHE1), which are dysregulated in Pancreatic Ductal Adenocarcinoma (PDAC). PDAC progression is favored by a Collagen-I rich extracellular matrix (ECM) which exacerbates the physiological interstitial acidosis. In organotypic cultures of normal human pancreatic cells (HPDE), parenchymal cancer cells (CPCs) and cancer stem cells (CSCs) growing on matrices reproducing ECM changes during progression, we studied resting pHi, the pHi response to fluxes of NaHCO₃ and acidosis and the role of NHE1 in pHi regulation. Our findings show that: (i) on the physiological ECM, HPDE cells have the most alkaline pHi, followed by CSCs and CPCs, while a Collagen I-rich ECM reverses the acid-base balance in cancer cells compared to normal cells; (ii) both resting pHi and pHi recovery from an acid load are reduced by extracellular NaHCO₃, especially in HPDE cells on a normal ECM; (iii) cancer cell NHE1 activity is less affected by NaHCO₃. We conclude that ECM composition and the fluctuations of pHe cooperate to predispose pHi homeostasis towards the presence of NaHCO₃ gradients similar to that expected in the tumor.

A snapshot of the vast array of diamagnetic CEST MRI contrast agents

Since the inception of CEST MRI in the 1990s, a number of compounds have been identified as suitable for generating contrast, including paramagnetic lanthanide complexes, hyperpolarized atom cages and, most interesting, diamagnetic compounds. In the past two decades, there has been a major emphasis in this field on the identification and application of diamagnetic compounds that have suitable biosafety profiles for usage in medical applications. Even in the past five years there has been a tremendous growth in their numbers, with more and more emphasis being placed on finding those that can be ultimately used for patient studies on clinical 3 T scanners. At this point, a number of endogenous compounds present in tissue have been identified, and also natural and synthetic organic compounds that can be administered to highlight pathology via CEST imaging. Here we will provide a very extensive snapshot of the types of diamagnetic compound that can generate CEST MRI contrast, together with guidance on their utility on typical preclinical and clinical scanners and a review of the applications that might benefit the most from this new technology.

Fatty Acid Metabolites and the Tumor Microenvironment as Potent Regulators of Cancer Stem Cell Signaling

Individual cancer cells are not equal but are organized into a cellular hierarchy in which only a rare few leukemia cells can self-renew in a manner reminiscent of the characteristic stem cell properties. The PI3K/AKT pathway functions in a variety of cancers and plays a critical role in the survival and proliferation of healthy cells under physiologic conditions. In addition, cancer stem cells might exhibit a variety of metabolic reprogramming phenotypes that cannot be completely attributed to the intrinsic heterogeneity of cancer. Given the heterogeneity of cancer stem cells, new strategies with single-cell resolution will become a powerful tool to eradicate the aggressive cell population harboring cancer stem cell phenotypes. Here, this article will provide an overview of the most important signaling pathways of cancer stem cells regarding their relevance to the tumor microenvironment and fatty acid metabolism, suggesting valuable strategies among cancer immunotherapies to inhibit the recurrence of tumors.

Pleiotropic Signaling by Reactive Oxygen Species Concerted with Dietary Phytochemicals and Microbial-Derived Metabolites as Potent Therapeutic Regulators of the Tumor Microenvironment

The excessive generation of reactive oxygen species (ROS) plays a pivotal role in the pathogenesis of diseases. ROS are central to cellular redox regulation and act as second messengers to activate redox-sensitive signals. Recent studies have revealed that certain sources of ROS can be beneficial or harmful to human health. Considering the essential and pleiotropic roles of ROS in basic physiological functions, future therapeutics should be designed to modulate the redox state. Dietary phytochemicals, microbiota, and metabolites derived from them can be expected to be developed as drugs to prevent or treat disorders in the tumor microenvironment.

Epigenetic Regulation Mediated by Sphingolipids in Cancer

Epigenetic changes are heritable modifications that do not directly affect the DNA sequence. In cancer cells, the maintenance of a stable epigenetic profile can be crucial to support survival and proliferation, and said profile can differ significantly from that of healthy cells. The epigenetic profile of a cancer cell can be modulated by several factors, including metabolites. Recently, sphingolipids have emerged as novel modulators of epigenetic changes. Ceramide and sphingosine 1-phosphate have become well known in cancer due to activating anti-tumour and pro-tumour signalling pathways, respectively, and they have recently been shown to also induce several epigenetic modifications connected to cancer growth. Additionally, acellular factors in the tumour microenvironment, such as hypoxia and acidosis, are now recognised as crucial in promoting aggressiveness through several mechanisms, including epigenetic modifications. Here, we review the existing literature on sphingolipids, cancer, and epigenetic changes, with a focus on the interaction between these elements and components of the chemical tumour microenvironment.

The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat

Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.

Excited-state intramolecular proton transfer (ESIPT)-based fluorescent probes for biomarker detection: design, mechanism, and application

Biomarkers are essential in biology, physiology, and pharmacology; thus, their detection is of extensive importance. Fluorescent probes provide effective tools for detecting biomarkers exactly. Excited state intramolecular proton transfer (ESIPT), one of the significant photophysical processes that possesses specific photoisomerization between Keto and Enol forms, can effectively avoid annoying interference from the background with a large Stokes shift. Hence, ESIPT is an excellent choice for biomarker monitoring. Based on the ESIPT process, abundant probes were designed and synthesized using three major design methods. In this review, we conclude probes for 14 kinds of biomarkers based on ESIPT explored in the past five years, summarize these general design methods, and highlight their application for biomarker detection in vitro or in vivo.

Cellular Invasion Assay for the Real-Time Tracking of Individual Cells in Spheroid or Tumor-like Mimics

Cellular invasion is the gateway to metastasis, with cells moving from a primary tumor into neighboring regions of healthy tissue. Invasion assays provide a tractable experimental platform to quantitatively assess cellular movement in the presence of potential chemokines or inhibitors. Many such assays involve cellular movement from high cell densities to cell-free regions. To improve the physiological relevance of such assays, we developed an assay format to track cellular movement throughout a uniform density of cells. This assay format imparts diffusion-dominated environments along the channel, resulting in oxygen and nutrient gradients found in spheroids or poorly vascularized tumors. By incorporating oxygen- and pH-sensing films, we quantified spatial and temporal changes in the extracellular environment while simultaneously tracking the movement of a subset of cells engineered to express fluorescent proteins constitutively. Our results show the successful invasion into neighboring tissues likely arises from a small population with a highly invasive phenotype. These highly invasive cells continued to move throughout the 48 h experiment, suggesting they have stem-like or persister properties. Surprisingly, the distance these persister cells invaded was unaffected by the density of cells in the channel or the presence or absence of an oxygen gradient. While these datasets cannot determine if the invasive cells are inherent to the population or if diffusion-dominated environments promote them, they highlight the need for further study.

Engineering lactate-modulating nanomedicines for cancer therapy

Lactate in tumors has long been considered "metabolic junk" derived from the glycolysis of cancer cells and utilized only as a biomarker of malignancy, but is presently believed to be a pivotal regulator of tumor development, maintenance and metastasis. Indeed, tumor lactate can be a "fuel" for energy supply and functions as a signaling molecule, which actively contributes to tumor progression, angiogenesis, immunosuppression, therapeutic resistance, etc., thus providing promising opportunities for cancer treatment. However, the current approaches for regulating lactate homeostasis with available agents are still challenging, which is mainly due to the short half-life, low bioavailability and poor specificity of these agents and their unsatisfactory therapeutic outcomes. In recent years, lactate modulation nanomedicines have emerged as a charming and efficient strategy for fighting cancer, which play important roles in optimizing the delivery of lactate-modulating agents for more precise and effective modulation and treatment. Integrating specific lactate-modulating functions in diverse therapeutic nanomedicines may overcome the intrinsic restrictions of different therapeutic modalities by remodeling the pathological microenvironment for achieving enhanced cancer therapy. In this review, the most recent advances in the engineering of functional nanomedicines that can modulate tumor lactate for cancer therapy are summarized and discussed, and the fundamental mechanisms by which lactate modulation benefits various therapeutics are elucidated. Finally, the challenges and perspectives of this emerging strategy in the anti-tumor field are highlighted.

The Significance of Cancer Stem Cells and Epithelial-Mesenchymal Transition in Metastasis and Anti-Cancer Therapy

Cancer stem cells (CSCs) have been identified and characterized in both hematopoietic and solid tumors. Their existence was first predicted by Virchow and Cohnheim in the 1870s. Later, many studies showed that CSCs can be identified and isolated by their expression of specific cell markers. The significance of CSCs with respect to tumor biology and anti-cancer treatment lies in their ability to maintain quiescence with very slow proliferation, indefinite self-renewal, differentiation, and trans-differentiation such as epithelial-mesenchymal transition (EMT) and its reverse process mesenchymal-epithelial transition (MET). The ability for detachment, migration, extra- and intravasation, invasion and thereby of completing all necessary steps of the metastatic cascade highlights their significance for metastasis. CSCs comprise the cancer cell populations responsible for tumor growth, resistance to therapies and cancer metastasis. In this review, the history of the CSC theory, their identification and characterization and their biology are described. The contribution of the CSC ability to undergo EMT for cancer metastasis is discussed. Recently, novel strategies for drug development have focused on the elimination of the CSCs specifically. The unique functional and molecular properties of CSCs are discussed as possible therapeutic vulnerabilities for the development of novel anti-metastasis treatments. Prospectively, this may provide precise personalized anti-cancer treatments with improved therapeutic efficiency with fewer side effects and leading to better prognosis.

Therapeutic Strategies to Overcome Fibrotic Barriers to Nanomedicine in the Pancreatic Tumor Microenvironment

Pancreatic cancer is notorious for its dismal prognosis. The enhanced permeability and retention (EPR) effect theory posits that nanomedicines (therapeutics in the size range of approximately 10-200 nm) selectively accumulate in tumors. Nanomedicine has thus been suggested to be the "magic bullet"-both effective and safe-to treat pancreatic cancer. However, the densely fibrotic tumor microenvironment of pancreatic cancer impedes nanomedicine delivery. The EPR effect is thus insufficient to achieve a significant therapeutic effect. Intratumoral fibrosis is chiefly driven by aberrantly activated fibroblasts and the extracellular matrix (ECM) components secreted. Fibroblast and ECM abnormalities offer various potential targets for therapeutic intervention. In this review, we detail the diverse strategies being tested to overcome the fibrotic barriers to nanomedicine in pancreatic cancer. Strategies that target the fibrotic tissue/process are discussed first, which are followed by strategies to optimize nanomedicine design. We provide an overview of how a deeper understanding, increasingly at single-cell resolution, of fibroblast biology is revealing the complex role of the fibrotic stroma in pancreatic cancer pathogenesis and consider the therapeutic implications. Finally, we discuss critical gaps in our understanding and how we might better formulate strategies to successfully overcome the fibrotic barriers in pancreatic cancer.