Extracellular Acidity Research Articles

Tumor site-specific PEG detachment and active tumor homing of therapeutic PEGylated chitosan/folate-decorated polydopamine nanoparticles to augment antitumor efficacy of photothermal/chemo combination therapy

To effectively promote tumor-targeted delivery of photothermal/chemo combined therapy for boosted antitumor efficacy, the versatile photothermal hybrid polymeric nanoparticles capable of detaching poly(ethylene glycol) (PEG) segments and exposing tumor-targeting folate (FA) moieties in response to tumor extracellular acidity (pHe) are developed to selectively deliver doxorubicin (DOX), a chemotherapy drug, to the tumor sites. Through one-pot co-deposition of dopamine molecules with acidity-responsive benzoic imine-containing PEGylated chitosan (BI-PC) adducts, the hybrid BI-PC/polydopamine (PDA) nanoparticles were attained as DOX vehicles and characterized to have a spherical structure composed of a PDA core surrounded by hydrophilic BI-PC shells. The DOX@BI-PC/PDA nanoparticles not only showed prominent colloidal stability in serum-containing environment and photothermal conversion efficiency, but also exhibited acidity/photothermal-activated drug release. The PEG detachment and FA exposure of FA-DOX@BI-PC/PDA nanoparticles in weak acidic environment appreciably promoted their uptake by FA receptor-overexpressed CT-26 colon cancer cells, thus largely augmenting anticancer potency based on the photothermal/chemo therapy. Importantly, the pHe-responsive FA-DOX@BI-PC/PDA nanoparticles markedly accumulated in CT-26 tumor sites in vivo and inhibited tumor growth without significant systemic toxicity upon the near infrared (NIR)-triggered hyperthermia integrated with DOX chemotherapy. This work presents a practical strategy for improved antitumor potency of photothermal/chemo combination therapy.

Lipogenesis mediated by OGR1 regulates metabolic adaptation to acid stress in cancer cells via autophagy.

SUMMARYMalignant tumors exhibit altered metabolism resulting in a highly acidic extracellular microenvironment. Here, we show that cytoplasmic lipid droplet (LD) accumulation, indicative of a lipogenic phenotype, is a cellular adaption to extracellular acidity. LD marker PLIN2 is strongly associated with poor overall survival in breast cancer patients. Acid-induced LD accumulation is triggered by activation of the acid-sensing G-protein-coupled receptor (GPCR) OGR1, which is expressed highly in breast tumors. OGR1 depletion inhibits acid-induced lipid accumulation, while activation by a synthetic agonist triggers LD formation. Inhibition of OGR1 downstream signaling abrogates the lipogenic phenotype, which can be rescued with OGR1 ectopic expression. OGR1-depleted cells show growth inhibition under acidic growth conditions in vitro and tumor formation in vivo. Isotope tracing shows that the source of lipid precursors is primarily autophagy-derived ketogenic amino acids. OGR1-depleted cells are defective in endoplasmic reticulum stress response and autophagy and hence fail to accumulate LDs affecting survival under acidic stress.

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

BackgroundPancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic neoplasm with high metastatic potential and poor clinical outcome. Like other solid tumors, PDAC in the early stages is often asymptomatic, and grows very slowly under a distinct acidic pHe (extracellular pH) microenvironment. However, most previous studies have only reported the fate of cancerous cells upon cursory exposure to acidic pHe conditions. Little is known about how solid tumors—such as the lethal PDAC originating within the pancreatic duct-acinar system that secretes alkaline fluids—evolve to withstand and adapt to the prolonged acidotic microenvironmental stress.MethodsRepresentative PDAC cells were exposed to various biologically relevant periods of extracellular acidity. The time effects of acidic pHe stress were determined with respect to tumor cell proliferation, phenotypic regulation, autophagic control, metabolic plasticity, mitochondrial network dynamics, and metastatic potentials.ResultsUnlike previous short-term analyses, we found that the acidosis-mediated autophagy occurred mainly as an early stress response but not for later adaptation to microenvironmental acidification. Rather, PDAC cells use a distinct and lengthy process of reversible adaptive plasticity centered on the early fast and later slow mitochondrial network dynamics and metabolic adjustment. This regulates their acute responses and chronic adaptations to the acidic pHe microenvironment. A more malignant state with increased migratory and invasive potentials in long-term acidosis-adapted PDAC cells was obtained with key regulatory molecules being closely related to overall patient survival. Finally, the identification of 34 acidic pHe-related genes could be potential targets for the development of diagnosis and treatment against PDAC.ConclusionsOur study offers a novel mechanism of early rapid response and late reversible adaptation of PDAC cells to the stress of extracellular acidosis. The presence of this distinctive yet slow mode of machinery fills an important knowledge gap in how solid tumor cells sense, respond, reprogram, and ultimately adapt to the persistent microenvironmental acidification.

ES-MION-Based Dual-Modality PET/MRI Probes for Acidic Tumor Microenvironment Imaging.

Among all characteristics of the tumor microenvironment (TME), which are caused by abnormal proliferation of solid tumors, extracellular acidity is an important indicator for malignancy grading. pH-low insertion peptides (pHLIPs) are adopted to discern the acidic TME. To date, different imaging agents including fluorescent, positron emission tomography (PET), single photon emission computed tomography (SPECT), and magnetic resonance (MR) contrast agents with pHLIPs to target the acidic TME have been used to image various tumor models successfully. In this article, a PET/MRI dual-modality probe, based on extremely small magnetic iron oxide nanoparticles (ES-MIONs) with pHLIPs as a targeting unit, was proposed for the first time. In the phantom study, the probe showed relatively high r1 relaxivity (r1 = 1.03 mM–1 s–1), indicating that it could be used as a T1-weighted MR contrast agent. The 68Ga-radiolabeled probe was further studied in vitro and in vivo to evaluate pHLIP targeting efficacy and feasibility for PET/MRI. PET with intratumoral injection and T1-weighted MRI with intravenous injection both showed pHLIP-specific delivery of the probe. Therefore, we successfully designed and developed a radiolabeled ES-MION-based dual-modality PET/MRI agent to target the acidic tumor microenvironment. Although the accumulation of the probe in tumors with intravenous injection was not high enough to exhibit signals in the PET imaging study, our study still provides further insights into the ES-MION-based PET/MRI strategy.

In Vivo Distribution and Therapeutic Efficacy of Radioiodine-Labeled pH-Low Insertion Peptide Variant 3 in a Mouse Model of Breast Cancer.

Purpose Extracellular acidity is a marker of highly aggressive breast cancer (BC). pH-low insertion peptides (pHLIPs) target the acidic tumor microenvironment. This study evaluates the distribution and therapeutic efficacy of radioiodine-labeled pHLIP variant 3 (Var3) in a mouse model of BC. Methods The binding of fluorescein isothiocyanate (FITC)- or radioiodine-125 (125I) labeled Var3-pHLIP to MDA-MB-231, 4T1, and SK-BR-3 BC cell lines under different pH values was evaluated in vitro. The distribution of 125I-labeled Var3-pHLIP and wild-type- (WT-) pHLIP in tumor-bearing mice was analyzed in vivo using micro-SPECT/CT imaging. The therapeutic efficacy of radioiodine-131 (131I)-labeled Var3-pHLIP in MDA-MB-231 xenografts was evaluated by relative tumor volume measurement and immunohistochemical analysis. Results The binding ability of FITC- or 125I-labeled Var3-pHLIP to tumor cells increased with the decrease in pH. The tumor-to-background ratio of 125I-Var3-pHLIP in BC xenografts showed the best imaging contrast at 24 h or 48 h postinjection. The uptake of 125I-Var3-pHLIP in MDA-MB-231 xenografts at 2 h postinjection was significantly higher than that of 125I-WT-pHLIP (3.76 ± 0.37 vs. 2.87 ± 0.60%ID/g, p = 0.046). The relative tumor volume in MDA-MB-231 xenografts was significantly lower in the 131I-Var3-pHLIP-treated group than in the groups treated with Var3-pHLIP (p = 0.027), 131I (p = 0.001), and saline (p < 0.001). The 131I-Var 3-pHLIP group presented a lower expression of Ki67 and a higher expression of caspase 3. Conclusion Radioiodine-labeled Var3-pHLIP effectively targeted BC cells in an acidic environment and inhibited the growth of MDA-MB-231 xenografts by ionizing radiation.

Dysregulated proton and sodium gradients highlight cancer invasion and proliferation

Acidity and salinity of the extracellular fluid, reflecting degrees of acid and sodium contents respectively, regulate essential cellular functions in health and disease, especially cancer. Tumor invasiveness is enhanced by the acidic extracellular milieu as a consequence of upregulated aerobic glycolysis. But recent discoveries also suggest that enhanced proliferative mitosis, which also hallmarks cancer, is impacted by interstitial salinity. Abnormal transmembrane proton/sodium gradients lead to pathophysiological alterations at the cellular level. These novel perspectives mandate pioneering imaging of extracellular acidity and salinity, preferably monitored simultaneously. By dissecting the interplay between dysregulated pH and electrolyte imbalance within the tumor habitat, these biomarkers hold promise for early cancer diagnosis and tracking therapies, from chemotherapy to immunotherapy.

Why may citrate sodium significantly increase the effectiveness of transarterial chemoembolization in hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) represents the third cause of cancer death in men worldwide, and its increasing incidence can be explained by the increasing occurrence of non-alcoholic steatohepatitis (NASH). HCC prognosis is poor, as its 5-year overall survival is approximately 18 % and most cases are diagnosed at an inoperable advanced stage. Moreover, tumor sensitivity to conventional chemotherapeutics (particularly to cisplatin-based regimen), trans-arterial chemoembolization (cTACE), tyrosine kinase inhibitors, anti-angiogenic molecules and immune checkpoint inhibitors is limited. Oncogenic signaling pathways, such as HIF-1α and RAS/PI3K/AKT, may provoke drug resistance by enhancing the aerobic glycolysis ("Warburg effect") in cancer cells. Indeed, this metabolism, which promotes cancer cell development and aggressiveness, also induces extracellular acidity. In turn, this acidity promotes the protonation of drugs, hence abrogating their internalization, since they are most often weakly basic molecules. Consequently, targeting the Warburg effect in these cancer cells (which in turn would reduce the extracellular acidification) could be an effective strategy to increase the delivery of drugs into the tumor. Phosphofructokinase-1 (PFK1) and its activator PFK2 are the main regulators of glycolysis, and they also couple the enhancement of glycolysis to the activation of key signaling cascades and cell cycle progression. Therefore, targeting this "Gordian Knot" in HCC cells would be of crucial importance. Here, we suggest that this could be achieved by citrate administration at high concentration, because citrate is a physiologic inhibitor of PFK1 and PFK2. As shown in various in vitro studies, including HCC cell lines, administration of high concentrations of citrate inhibits PFK1 and PFK2 (and consequently glycolysis), decreases ATP production, counteracts HIF-1α and PI3K/AKT signaling, induces apoptosis, and sensitizes cells to cisplatin treatment. Administration of high concentrations of citrate in animal models (including Ras-driven tumours) has been shown to effectively inhibit cancer growth, reverse cell dedifferentiation, and neutralize intratumor acidity, without apparent toxicity in animal studies. Citrate may also induce a rapid secretion of pro-inflammatory cytokines by macrophages, and it could favour the destruction of cancer stem cells (CSCs) sustaining tumor recurrence. Consequently, this "citrate strategy" could improve the tumor sensitivity to current treatments of HCC by reducing the extracellular acidity, thus enhancing the delivery of chemotherapeutic drugs into the tumor. Therefore, we propose that this strategy should be explored in clinical trials, in particular to enhance cTACE effectiveness.

Abstract LBA050: Bioenergetic evaluation of Mito-compound Mito-Met as potent cytotoxic agents in gastric cancer

Abstract Gastric cancer (GC) kills around 800,000 people each year around the world, placing it among the deadliest types of cancer. The evolution of intestinal metaplasia is unknown, but there are different factors that are involved in its development, the diet rich in salt, the Epstein-Barr virus, Helicobacter pylori and a wide variety of genes that affect cell activity. Currently, surgical resection with chemotherapy is the main treatment with a 5-year survival of 30% that varies according to the metastatic extension. The mitochondria is now one of the therapeutic targets in the development of new compounds with anticancer capacity and it has been observed that metformin behaves as an insulin sensitizer at high concentrations, inhibiting the mitochondrial complex I. For this reason, Mito-metformin (Mito-Met) was designed, this is a mitochondrial analogue of metformin that is linked to the lipophilic alkyl triphenylphosphonium cation (TPP) with a mitochondrial effect 1000 times greater at low concentrations. In this study, the effects of Mito-Met were evaluated in two GC cell lines (AGS and KATO III) and in the healthy gastric epithelium cell line (HPSEC). Cell viability, cytotoxicity, colony formation and cell migration assays were performed. Also, it was evaluated whether Mito-Met had the potential to affect mitochondrial bioenergetics by evaluating the OCR oxygen consumption rate, ECAR extracellular acidity rate, glycolytic capacity and mitochondrial fuel oxidation in live cells in real time using the analyzer XFe24 extracellular flux from Seahorse Biosciences. A dose-time-dependent decrease in cell viability was observed with IC50 values of 2.9 µM, 19,3 µM and 22,1 µM in AGS, KATO and HPSEC cells, respectively. The results in clonogenic assay showed that Mito-Met strongly affected AGS with an IC50 of 11.7 uM and a greater impact was observed in HPSEC than in KATO III, with IC50 values of 31.8 uM and 3.6 x 103 uM, respectively. The results of the wound healing assay showed that Mito-Met has a significant time-dependent dose effect on metastasis. Mito-Met affects the mitocondrial bioenergetics, our results showed affectation of basal respiration, maximum respiration, ATP production and reserve capacity in both cell lines. Mito-Met decreased baseline OCR and stressed OCR in a dose-dependent manner in both GC cell lines. Mito-Met increased the metabolic potential in a dose-dependent manner of OCR in AGS, on the contrary, a dose-dependent decrease of ECAR was observed in KATO III. There was no change in HPSEC. These results show that Mito-Met is promising compound for treatment of GC. Citation Format: Giovanni A Lineros Franco, Yenny Bueno, Micael Hardy, Olivier Ouari, Julio C. Montoya-Villegas, Marcos López-Casilla, Sandra M. Sanabria-Barrera. Bioenergetic evaluation of Mito-compound Mito-Met as potent cytotoxic agents in gastric cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr LBA050.

The role of tumor acidification in aggressiveness, cell dissemination and treatment resistance of oral squamous cell carcinoma

AimsTo investigate the role of tumor acidification in cell behavior, migration, and treatment resistance of oral squamous cell carcinoma (OSCC). Main methodsThe SCC4 and SCC25 cell lines were exposed to acidified (pH 6.8) cell culture medium for 7 days. Alternatively, a long-term acidosis was induced for 21 days. In addition, to mimic dynamic pH fluctuation of the tumor microenvironment, cells were reconditioned to neutral pH after experimental acidosis. This study assessed cell proliferation and viability by sulforhodamine B and flow cytometry. Individual and collective cell migration was analyzed by wound healing, time lapse, and transwell assays. Modifications of cell phenotype, EMT induction and stemness potential were investigated by qRT-PCR, western blot, and immunofluorescence. Finally, resistance to chemo- and radiotherapy of OSCC when exposed to acidified environmental conditions (pH 6.8) was determined. Key findingsThe exposure to an acidic microenvironment caused an initial reduction of OSCC cells viability, followed by an adaptation process. Acidic adapted cells acquired a mesenchymal-like phenotype along with increased migration and motility indexes. Moreover, tumoral extracellular acidity was capable to induce cellular stemness and to increase chemo- and radioresistance of oral cancer cells. SignificanceIn summary, the results showed that the acidic microenvironment leads to a more aggressive and treatment resistant OSCC cell population.

Acid-Sensing Ion Channels: Expression and Function in Resident and Infiltrating Immune Cells in the Central Nervous System.

Peripheral and central immune cells are critical for fighting disease, but they can also play a pivotal role in the onset and/or progression of a variety of neurological conditions that affect the central nervous system (CNS). Tissue acidosis is often present in CNS pathologies such as multiple sclerosis, epileptic seizures, and depression, and local pH is also reduced during periods of ischemia following stroke, traumatic brain injury, and spinal cord injury. These pathological increases in extracellular acidity can activate a class of proton-gated channels known as acid-sensing ion channels (ASICs). ASICs have been primarily studied due to their ubiquitous expression throughout the nervous system, but it is less well recognized that they are also found in various types of immune cells. In this review, we explore what is currently known about the expression of ASICs in both peripheral and CNS-resident immune cells, and how channel activation during pathological tissue acidosis may lead to altered immune cell function that in turn modulates inflammatory pathology in the CNS. We identify gaps in the literature where ASICs and immune cell function has not been characterized, such as neurotrauma. Knowledge of the contribution of ASICs to immune cell function in neuropathology will be critical for determining whether the therapeutic benefits of ASIC inhibition might be due in part to an effect on immune cells.

Extracellular acidity in tumor tissue upregulates programmed cell death protein1 expression on tumor cells via proton-sensing G protein-coupled receptors.

Acidity in the tumor microenvironment has been reported to promote cancer growth and metastasis. In our study, we examined a potential relation between extracellular acidity and expression level of the immune checkpoint molecule programmed cell death protein1 (PD-L1) in murine squamous cell carcinoma (SCC) and melanoma cell lines. PD-L1 expression in the tumor cells was upregulated by culturing in a low pH culture medium. Tumor-bearing mice were allowed to ingest sodium bicarbonate, resulting in neutralization of acidity in the tumor tissue, a decrease in PD-L1 expression in tumor cells and suppression of tumor growth in vivo. Proton-sensing G protein-coupled receptors, T-cell death-associated gene 8 (TDAG8) and ovarian cancer G-protein-coupled receptor 1 (OGR1), were upregulated by low pH, and essentially involved in the acidity-induced elevation of PD-L1 expression in the tumor cells. Human head and neck SCC RNAseq data from the Cancer Genome Atlas also suggested a statistically significant correlation between expression levels of the proton sensors and PD-L1 mRNA expression. These findings strongly suggest that neutralization of acidity in tumor tissue may result in reduction of PD-L1 expression, potentially leading to inhibition of an immune checkpoint and augmentation of antitumor immunity.

Modulation of Tumor Microenvironment to Enhance Radiotherapy Efficacy in Esophageal Squamous Cell Carcinoma by Inhibiting Carbonic Anhydrase IX.

The radiotherapy outcomes of patients with advanced esophageal squamous cell carcinoma (ESCC) remain poor due to hypoxia. Carbonic anhydrase IX (CAIX) is a membrane-associated enzyme that induces hypoxia, extracellular acidity, and upregulation of hypoxia-related factors in tumor microenvironment, thereby promoting tumor metastasis. CAIX is upregulated in ESCC tissues compared to normal surrounding tissues. In the current study, we aimed to investigate the effect of CAIX inhibition on the modulation of tumor microenvironment and radiotherapy efficacy in ESCC. Higher CAIX expression was correlated with poorer progression-free survival in ESCC patients. Then, the ethyl N-(4-methylphenyl) sulfonylcarbamate (S4) was used to inhibit CAIX expression in ESCC cells and mice xenografts. The pretreatment of ESCC cells with S4 significantly downregulated CAIX expression, decreased intracellular pH, reduced cell viability, resulting in decreased oxygen consumption and more sensitive response to X-ray irradiation. In mice inoculated with ESCC cells, the combination of X-ray irradiation with S4 further improved survival, delayed tumor growth, decreased hypoxia level, exaggerated DNA damage, and increased apoptosis compared with the groups treated solely with S4 or radiotherapy. In conclusion, our study showed that the inhibition of CAIX by S4 treatment altered hypoxic tumor micro-environment, exaggerated DNA damage, increased apoptosis, and thus enhanced radiotherapy efficacy in ESCC. These findings provided a potential therapeutic strategy for patients with resistant ESCC.

Understanding the Central Role of Citrate in the Metabolism of Cancer Cells and Tumors: An Update.

Citrate plays a central role in cancer cells’ metabolism and regulation. Derived from mitochondrial synthesis and/or carboxylation of α-ketoglutarate, it is cleaved by ATP-citrate lyase into acetyl-CoA and oxaloacetate. The rapid turnover of these molecules in proliferative cancer cells maintains a low-level of citrate, precluding its retro-inhibition on glycolytic enzymes. In cancer cells relying on glycolysis, this regulation helps sustain the Warburg effect. In those relying on an oxidative metabolism, fatty acid β-oxidation sustains a high production of citrate, which is still rapidly converted into acetyl-CoA and oxaloacetate, this latter molecule sustaining nucleotide synthesis and gluconeogenesis. Therefore, citrate levels are rarely high in cancer cells. Resistance of cancer cells to targeted therapies, such as tyrosine kinase inhibitors (TKIs), is frequently sustained by aerobic glycolysis and its key oncogenic drivers, such as Ras and its downstream effectors MAPK/ERK and PI3K/Akt. Remarkably, in preclinical cancer models, the administration of high doses of citrate showed various anti-cancer effects, such as the inhibition of glycolysis, the promotion of cytotoxic drugs sensibility and apoptosis, the neutralization of extracellular acidity, and the inhibition of tumors growth and of key signalling pathways (in particular, the IGF-1R/AKT pathway). Therefore, these preclinical results support the testing of the citrate strategy in clinical trials to counteract key oncogenic drivers sustaining cancer development and resistance to anti-cancer therapies.

Extracellular Acidity Reprograms Macrophage Metabolism and Innate Responsiveness.

Although organ hypofunction and immunosuppression are life-threatening features of severe sepsis, the hypofunctioning organs and immune cells usually regain normal functionality if patients survive. Because tissue interstitial fluid can become acidic during the septic response, we tested the hypothesis that low extracellular pH (pHe) can induce reversible metabolic and functional changes in peritoneal macrophages from C57BL/6J mice. When compared with macrophages cultured at normal pHe, macrophages living in an acidic medium used less glucose and exogenous fatty acid to produce ATP. Lactate, glutamine, and de novo-synthesized fatty acids supported ATP production by mitochondria that gained greater mass, maximal oxygen consumption rate, and spare respiratory capacity. The cells transitioned to an M2-like state, with altered immune responses to LPS and slightly decreased phagocytic ability, yet they regained basal energy production, normal mitochondrial function, and proinflammatory responsiveness when neutral pHe was restored. Low pHe induces changes that support macrophage survival while rendering the cells less proinflammatory (more "tolerant") and less able to phagocytose bacteria. Macrophage responses to low interstitial pH may contribute to the reversible organ hypofunction and immunoparalysis noted in many patients with sepsis.

Targeted and intracellular delivery of protein therapeutics by a boronated polymer for the treatment of bone tumors

The treatment of malignant bone tumors by chemotherapeutics often receives poor therapeutic response due to the specific physiological bone environment, and thus calls for the development of new therapeutic options. Here, we reported a bone-targeted protein nanomedicine for this purpose. Saporin, a toxin protein, was co-assembled with a boronated polymer for intracellular protein delivery, and the formed nanoparticles were further coated with an anionic polymer poly (aspartic acid) to shield the positive charges on nanoparticles and provide the bone targeting function. The prepared ternary complex nanoparticles showed high bone accumulation both in vitro and in vivo, and could reverse the surface charge property from negative to positive after locating at tumor site triggered by tumor extracellular acidity. The boronated polymer in the de-shielded nanoparticles further promote intracellular delivery of saporin into tumor cells, exerting the anticancer activity of saporin by inactivation of ribosomes. As a result, the bone-targeted and saporin-loaded nanomedicine could kill cancer cells at a low saporin dose, and efficiently prevented the progression of osteosarcoma xenograft tumors and bone metastatic breast cancer in vivo. This study provides a facile and promising strategy to develop protein-based nanomedicines for the treatment of malignant bone tumors.

Extracellular Acidity-mediated Expression of cPLA2γ Confers Resistance in Gastric Cancer Cells.

Extracellular acidity, a characteristic of solid tumors, has been proposed to be a critical factor for aggravating tumor malignancy and conferring resistance to therapeutics. Recently, acidity has been implicated in inflammatory responses, which are mediated through active lipid metabolites in various human tissues. In the present study, we investigated whether acidity can affect lipid-mediated signaling, and found that phospholipase A2 (PLA2) activity increased at acidic pH in SNU601 and AGS gastric carcinoma cell lines. To identify the PLA2 isoform that is responsible for the acidity-induced activity, we assessed mRNA levels of cPLA2 isotypes through real-time qPCR, and protein levels through immunoblot assay in cells cultured in acidic medium. It was found that acidic pH conditions markedly elevated the PLA2γ expression. A gene interference study using specific siRNA of cPLA2γ suggested that expression of cPLA2γ in acidic culture conditions may be associated with protection of cancer cells in acidic environment, as shown by cell viability and clonogenic assays. In addition, expression of cPLA2γ appeared to confer cell resistance to anticancer drugs under acidic pH conditions. Acidity-induced cPLA2γ expression may exert protective effects by imparting resistance to the gastric cancer cells under acidic environment.

Nanocatalytic Medicine of Iron-Based Nanocatalysts

Iron can be found in all mammalian cells and is of critical significance to diverse cellular activities within human bodies. Widespread applications and the underlying chemical and biological funda...

Carrier-Free Platinum Nanomedicine for Targeted Cancer Therapy.

Numerous nanomedicines have been developed to improve the efficiency and safety of conventional anticancer drugs; however, the complexities in carrier materials and functional integration make it challenging to promote these candidates for clinical translation. In this study, a facile method to prepare carrier-free anticancer nanodrug with inherent bone targeting and osteoclastogenesis inhibition capabilities is reported. Phytic acid, a naturally occurring and nontoxic product, is reacted with cisplatin to form uniform nanoparticles of different sizes. The prepared nanoparticles possess high drug loading and pH-responsive drug release behaviors. Phytic acid in the nanomedicine ensures high bone targeting and osteoclastogenesis inhibition, and the released platinum drugs triggered by tumor extracellular acidity eradicate tumor cells. The nanomedicine around 100nm shows high anticancer activity and much reduced side effects in a subcutaneous breast cancer model when compared with cisplatin. In addition, it shows high accumulation at osteolytic lesions, and efficiently inhibits tumor growth and tumor-associated osteolysis in a bone metastatic breast cancer model. Here, a facile and efficient strategy to prepare carrier-free nanomedicines with high anticancer drug loading, inherent bone targeting, and osteoclast inhibitory activities for cancer therapy is provided.

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

Simple SummaryMultiple 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.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.

Abstract PO-049: Exploiting tumor acidic microenvironment for improved therapeutics

Abstract The tumor acidic microenvironment is a fundamental characteristic of solid tumors which distinguishes the tumor from adjacent normal tissues. This unique tumor microenvironment (TME) feature directly contributes to various aspect of tumor progression including gene expression, immune suppression, drug resistance, invasion and metastasis. Acidic TME poses great challenges for the efficacy of therapeutics; extracellular acidity of cancer cells provides less permissive conditions for optimal target engagement and drug efficacy. In addition targeting the effectors of acid-base balance enriched in hypoxia and acidic regions of the tumor provide valuable tools for normalizing the extracellular acidity and delivery of therapeutics agents to areas of the tumor less malleable to conventional therapies. Thus in the case of therapeutic antibodies, strategies that specifically integrates this TME specific feature in the design could improve binding to the target under low pH conditions and serve as delivery moiety that improve tumor specificity and functional efficacy. Here we describe two examples of these therapeutic strategies that leverage the acidic and hypoxic microenvironment to overcome the challenges posed by this hostile environment with the aim of generating improved therapeutic antibodies. A. Characterization of a set of function blocking therapeutic antibodies against key target expressed in response to hypoxia which contributes to tumor acidification, we demonstrate functional efficacy of this antibody to block the activity of the target in vitro and consequently reduce tumor spheroid growth. This and similar antibodies provide tools for specific targeting of the tumor areas that are often inaccessible to most therapeutics. B. Identification of targets enriched in acidic tumor microenvironment and design of pH selective therapeutic antibodies that preferentially bind to the target and exert their function under tumor acidic conditions. We demonstrate the functional selectivity of a variant of antibody targeting HER 2, with optimized binding under low pH conditions, on the growth of BT474 spheroids. The pH selective antibody variant blocked the tumor spheroid growth when spheroids were grown in TME-relevant- low pH conditions but it remained ineffective under normal physiological pH conditions. Suggesting increased selectivity of this antibody variant towards the acidic TME that in turn lower the on-target -off-tumor toxicity. In conclusion here we provide two examples of the strategies which exploit the targeting of hypoxia induced genes and pH selective design of the therapeutic antibodies in order to improve tumor targeting capacity and reduce systemic toxicity of conventional therapeutics. Citation Format: Nazanin Rohani Larijani, Traian Sulea, Mehdi Arbabi Ghahroudi, Beatrice Paul Roc, Mylene Gosselin, Joey Sheff, John C. Zwaagstra, Anne E.G. Lenferink. Exploiting tumor acidic microenvironment for improved therapeutics [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-049.