The influence of pH and hypoxia on tumor metastasis

Nanotechnology-mediated photodynamic therapy: Focus on overcoming tumor hypoxia

The oxygen level in the tumor is a critical marker that determines response to different treatments. Cancerous cells can adapt to hypoxia and low pH conditions within the tumor microenvironment (TME) to regulate tumor metabolism, proliferation, and promote tumor metastasis as well as angiogenesis, consequently leading to treatment failure and recurrence. In recent years, widespread attempts have been made to overcome tumor hypoxia through different methods, such as hyperbaric oxygen therapy (HBOT), hyperthermia, O2 carriers, artificial hemoglobin, oxygen generator hydrogels, and peroxide materials. While oxygen is found to be an essential agent to improve the treatment response of photodynamic therapy (PDT) and other cancer treatment modalities, the development of hypoxia within the tumor is highly associated with PDT failure. Recently, the use of nanoparticles has been a hot topic for researchers and exploited to overcome hypoxia through Oxygen-generating hydrogels, O2 nanocarriers, and O2 -generating nanoparticles. This review aimed to discuss the role of nanotechnology in tumor oxygenation and highlight the challenges, prospective, and recent advances in this area to improve PDT outcomes. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Lactate-induced protein lactylation: A bridge between epigenetics and metabolic reprogramming in cancer

Lactate is not only an endpoint of glycolysis but is gradually being discovered to play the role of a universal metabolic fuel for energy via the 'lactate shuttle' moving between cells and transmitting signals. The glycolytic-dependent metabolism found in tumours and fast-growing cells has made lactate a pivotal player in energy metabolism reprogramming, which enables cells to obtain abundant energy in a short time. Moreover, lactate can provide favourable conditions for tumorigenesis by shaping the acidic tumour microenvironment, recruiting immune cells, etc. and the recently discovered lactate-induced lactylation moves even further on pro-tumorigenesis mechanisms of lactate production, circulation and utilization. As with other epigenetic modifications, lactylation can modify histone proteins to alter the spatial configuration of chromatin, affect DNA accessibility and regulate the expression of corresponding genes. What's more, the degree of lactylation is inseparable from the spatialized lactate concentration, which builds a bridge between epigenetics and metabolic reprogramming. Here, we review the important role of lactate in energy reprogramming, summarize the latest finding of lactylation in tumorigenesis and try to explore therapeutic strategies in oncotherapy that can kill two birds with one stone.

FOXK2 regulates PFKFB3 in promoting glycolysis and tumorigenesis in multiple myeloma

Forkhead box K2 (FOXK2) is a transcription factor involved in regulating the pathophysiological processes in many types of cancers. Functioning as either an oncogene or tumor suppressor, FOXK2 is involved in cell proliferation, metastasis, DNA damage, metabolism, and autophagy. However, the functions of FOXK2 in multiple myeloma (MM) are still unexplored. Here we show that FOXK2 silencing by small interfering RNA (siRNA) prevented the expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) via dephosphorylation of an AMP-activated protein kinase (AMPK). Consistently, suppression of FOXK2 inhibited glycolysis and cell proliferation in MM cells. Furthermore, the correlation between FOXK2 expression and disease progression in MM was evaluated using the TCGA (The Cancer Genome Atlas) database. Taken together, we identified a novel FOXK2-dependent signaling pathway involved in the regulation of PFKFB3 expression in response to glycolysis, which might serve as a potential therapeutic target in MM.

Proton pump inhibitors and sensitization of cancer cells to radiation therapy

This review article outlines six molecular pathways that confer resistance of cancer cells to ionizing radiation, and describes how proton pump inhibitors (PPIs) may be used to overcome radioresistance induced by alteration of one or more of these signaling pathways. The inflammatory, adaptive, hypoxia, DNA damage repair, cell adhesion, and developmental pathways have all been linked to the resistance of cancer cells to ionizing radiation. Here we describe the molecular link between alteration of these pathways in cancer cells and development of resistance to ionizing radiation, and discuss emerging data on the use of PPIs to favorably modify one or more components of these pathways to sensitize cancer cells to ionizing radiation. Understanding the relationship between altered signaling pathways, radioresistance, and biological activity of PPIs may serve as a basis to repurpose PPIs to restore key biological processes that are involved in cancer progression and to sensitize cancer cells to radiation therapy.

Glucose deprivation reduces proliferation and motility, and enhances the anti-proliferative effects of paclitaxel and doxorubicin in breast cell lines in vitro

Background

Breast cancer chemotherapy with high dose alkylating agents is severely limited by their collateral toxicity to crucial normal tissues such as immune and gut cells. Taking advantage of the selective dependence of cancer cells on high glucose and combining glucose deprivation with these agents could produce therapeutic synergy.

Methods

In this study we examined the effect of glucose as well as its deprivation, and antagonism using the non-metabolized analogue 2-deoxy glucose, on the proliferation of several breast cancer cell lines MCF7, MDA-MB-231, YS1.2 and pII and one normal breast cell line, using the MTT assay. Motility was quantitatively assessed using the wound healing assay. Lactate, as the end product of anaerobic glucose metabolism, secreted into culture medium was measured by a biochemical assay. The effect of paclitaxel and doxorubicin on cell proliferation was tested in the absence and presence of low concentrations of glucose using MTT assay.

Results

In all cell lines, glucose supplementation enhanced while glucose deprivation reduced both their proliferation and motility. Lactate added to the medium could substitute for glucose. The inhibitory effects of paclitaxel and doxorubicin were significantly enhanced when glucose concentration was decreased in the culture medium, requiring 1000-fold lesser concentration to achieve a similar degree of inhibition to that seen in glucose-containing medium.

Conclusion

Our data show that a synergy was obtained by combining paclitaxel and doxorubicin with glucose reduction to inhibit cancer cell growth, which in vivo, might be achieved by applying a carbohydrate-restricted diet during the limited phase of application of chemotherapy; this could permit a dose reduction of the cytotoxic agents, resulting in greater tolerance and lesser side effects.

Therapeutic approach for digestive system cancers and potential implications of exercise under hypoxia condition: what little is known? a narrative review

BACKGROUND

Cancer, like other chronic pathologies, is associated with the presence of hypoxic regions due to the uncontrolled cell growth. Under this pathological hypoxic condition, various molecular signaling pathways are activated to ensure cell survival, such as those that govern angiogenesis, erythropoiesis, among others. These molecular processes are very similar to the physiological response caused by exposure to altitude (natural hypobaric systemic hypoxia), the use of artificial hypoxia devices (systemic normobaric simulated hypoxia) or the delivery of vascular occlusion to the extremities (also called local hypoxia by the blood flow restriction technique). "Tumor hypoxia" has gained further clinical importance due to its crucial role in both tumor progression and resistance to treatment. However, the ability to manipulate this pathway through physical exercise and systemic hypoxia-mediated signaling pathways could offer an important range of therapeutic opportunities that should be further investigated.

METHODS

This review is focused on the potential implications of systemic hypoxia combined with exercise in digestive system neoplasms prognosis. Articles included in the review were retrieved by searching among the three main scientific databases: PubMed, Scopus, and Embase.

FINDINGS

The findings of this review suggest that exercise performed under systemic hypoxic conditions could have a positive impact in prognosis and quality of life of the population with digestive system cancers.

CONCLUSIONS

Further studies are needed to consider this paradigm as a new potential intervention in digestive oncological population.

Review of Oxygenation with Nanobubbles: Possible Treatment for Hypoxic COVID-19 Patients

The coronavirus disease (COVID-19) pandemic, which has spread around the world, caused the death of many affected patients, partly because of the lack of oxygen arising from impaired respiration or blood circulation. Thus, maintaining an appropriate level of oxygen in the patients' blood by devising alternatives to ventilator systems is a top priority goal for clinicians. The present review highlights the ever-increasing application of nanobubbles (NBs), miniature gaseous vesicles, for the oxygenation of hypoxic patients. Oxygen-containing NBs can exert a range of beneficial physiologic and pharmacologic effects that include tissue oxygenation, as well as tissue repair mechanisms, antiinflammatory properties, and antibacterial activity. In this review, we provide a comprehensive survey of the application of oxygen-containing NBs, with a primary focus on the development of intravenous platforms. The multimodal functions of oxygen-carrying NBs, including antimicrobial, antiinflammatory, drug carrying, and the promotion of wound healing are discussed, including the benefits and challenges of using NBs as a treatment for patients with acute hypoxemic respiratory failure, particularly due to COVID-19.

Lactate Dehydrogenase A or B Knockdown Reduces Lactate Production and Inhibits Breast Cancer Cell Motility in vitro

Background: Lactate dehydrogenase (LDH) plays an important role in cancer pathogenesis and enhanced expression/activity of this enzyme has been correlated with poor prognosis. In this study we determined the expression profile of LDH-A and B in normal as well as in endocrine-resistant and -responsive breast cancer cells and the effect of their knockdown on LDH activity, lactate production, proliferation and cell motility.

Methods: Knockdown experiments were performed using siRNA and shRNA. The expression profile of LDH and signaling molecules was determined using PCR and western blotting. Intracellular LDH activity and extracellular lactate levels were measured by a biochemical assay. Cell motility was determined using wound healing, while proliferation was determined using MTT assay.

Results: LDH-A was expressed in all of the tested cell lines, while LDH-B was specifically expressed only in normal and endocrine-resistant breast cancer cells. This was correlated with significantly enhanced LDH activity and lactate production in endocrine resistant breast cancer cells when compared to normal or endocrine responsive cancer cells. LDH-A or -B knockdown significantly reduced LDH activity and lactate production, which led to reduced cell motility. Exogenous lactate supplementation enhanced cell motility co-incident with enhanced phosphorylation of ERK1/2 and reduced E-cadherin expression. Also, LDH-A or -B knockdown reduced ERK 1/2 phosphorylation.

Conclusion: Enhanced cell motility in endocrine resistant breast cancer cells is at least in part mediated by enhanced extracellular lactate levels, and LDH inhibition might be a promising therapeutic target to inhibit cancer cell motility.

Precise Cancer Anti-acid Therapy Monitoring Using pH-Sensitive MnO2@BSA Nanoparticles by Magnetic Resonance Imaging

Microfluctuations in a pH gradient create a harsh microenvironment in tumors, leaving behind the most aggressive, invasive, and drug-resistant tumor cells. Directly visualizing the spatiotemporal distribution of pH variations and accurately quantifying the dynamic acid-base changes during cancer treatment are critical to estimate prognosis and to evaluate therapeutic efficacy. However, the quantification of subtle pH variations dynamically and noninvasively remains challenging. The purpose of this study is to determine and visualize dynamic acid-base changes in solid tumors during anti-acid treatments by magnetic resonance imaging (MRI) using pH-sensitive nanoparticles. We report the development of pH-sensitive nanoparticles, MnO₂@BSA, that rapidly and strongly amplify the MR contrast signal in response to the extracellular acidic environment of solid tumors. The spatiotemporal distribution and dynamic fluctuations of pH heterogeneity in NCI-H460 lung tumors were observed with MnO₂@BSA at different time points after an anti-acid treatment with esomeprazole, which directly interferes with the acidic microenvironment of the tumor. Imaging results were validated using a pH microsensor. MRI of pH-sensitive MnO₂@BSA nanoparticles provided direct readouts of the kinetics of pH gradient fluctuations during esomeprazole treatment. A significant MR signal reduction was observed at the 48 h time point after treatment. The manipulated extracellular pH changes detected noninvasively by MRI coincided with the extracellular pH fluctuations measured with a pH microsensor (pH 6.12-6.63). Immunofluorescence and Western blot analyses confirmed the expression of V-ATPase in NCI-H460 lung cancer cells, which could be inhibited by esomeprazole, as detected by ELISA assay. Overall, these results demonstrate that MnO₂@BSA MRI has great potential as a noninvasive tool to accurately monitor pH fluctuations, thereby paving the way for the dynamic detection of acidic microenvironments in vivo without the need for pH microsensors.

Identification and validation of a glycolysis-associated multiomics prognostic model for hepatocellular carcinoma

Increased glycolysis has been reported as a major metabolic hallmark in many cancers, and is closely related to malignant behavior of tumors. However, the potential mechanism of glycolysis in hepatocellular carcinoma (HCC) and its prognostic value are not well understood. To address this, we investigated glycolysis-related gene expression data of patients with HCC from TCGA and ICGC. Patients were categorized into three different glycolysis-associated subgroups: Glycolysis-M, Glycolysis-H, and Glycolysis-L. We found that Glycolysis-H combined with Glycolysis-M (Glycolysis-H+M) subgroup was associated with poor overall survival and distinct cancer stem cell characteristics and immune infiltrate patterns. Additionally, multiomics-based analyses were conducted to evaluate genomic patterns of glycolysis subgroups, including their gene mutations, copy number variations, and RNA-sequencing data. Finally, a glycolysis-associated multiomics prognostic model (GMPM) consisting of 19 glycolysis-associated genes was developed. The capability of GMPM in categorizing patients with HCC into high- and low-risk groups was validated with independent HCC datasets. Finally, GMPM was confirmed as an independent risk factor for the prognosis of patients with HCC. We believe that our findings provide new insights into the mechanism of glycolysis and highlight the potential clinical value of GMPM in predicting the prognosis of patients with HCC.

Binary blended co-delivery nanoparticles with the characteristics of precise pH-responsive acting on tumor microenvironment

Although combined chemotherapy had achieved the ideal efficacy in clinical anti-cancer therapeutic, the issues that need to be addressed are non-targeting and toxic-side effects of small molecule chemical drug (SMCD). In this study, we designed and prepared a novel binary blended co-delivered nanoparticles (BBCD NPs) with pH-responsive feature on tumor microenvironment. The BBCD NPs consists of two kind of drug-loaded NPs, in one of which carboxymethyl chitosan (CMC) and Poly (lactic-co-glycolic acid) (PLGA) were chosen as delivery carrier to load anti-cancer drug vincristine (VCR), named CMC-PLGA-VCR NPs (or CPNP_VCR); and in the other of which methoxy poly(ethylene glycol)-poly(β-amino ester) (mPEG-PAE) were chosen as delivery carrier to load anti-fibrotic drug pirfenidone (PFD), named mPEG-PAE-PFD NPs (or PPNP_PFD). Then, the two types of NPs (CPNP_VCR and PPNP_PFD) were physically mixed in mass ratios to form BBCD NPs, which was named CPNP_VCR&PPNP_PFD. CPNP_VCR&PPNP_PFD had good encapsulation efficiency and loading capacity, and the particle size distribution was uniform. In cytotoxicity experiments and non-contact co-culture studies in vitro, the model drugs loaded in CPNPVCR&PPNPPFD could respectively target cancer cell and cancer associated fibroblast (CAF) owing to the precise pH-sensitive drug release in the pharmacological targets and show stronger synergism than that of the combined treatment of two free drugs. As a modularity and assemble ability feature in design, BBCD NPs would have the advantages on the terms of concise on preparation process, controllable on quality standard, stable in natural environment storage. The research results can provide scientific evidence for the further development of a novel drug co-delivery system with multi-type cell targets.

Alterations in glycolytic/cholesterogenic gene expression in hepatocellular carcinoma

Metabolic reprogramming is a hallmark of tumors, including hepatocellular carcinoma (HCC). We used data from The Cancer Genome Atlas and the International Cancer Genome Consortium to assess the alterations in glycolytic and cholesterogenic genes in HCC and to determine their association with clinical features in HCC patients. Based on the gene expression profiles from these databases, we established four subtypes of HCC: cholesterogenic, glycolytic, mixed, and quiescent. The prognosis of the cholesterogenic subgroup was poorer than that of the glycolytic group. Tumors in the glycolytic group were more sensitive to chemotherapy. We also explored the relationships between these metabolic subtypes and previously established HCC subgroups. Glycolytic gene expression correlated strongly with poorer prognostic gene expression in the Hoshida classification of HCC. Whole-genome analyses indicated that aberrant amplification of TP53 and MYC in HCC were associated with abnormal anabolic cholesterol metabolism. The mRNA levels of mitochondrial pyruvate carriers 1 and 2 differed among the HCC metabolic subtypes. In a bioinformatics analysis we identified genomic characteristics of tumor metabolism that varied among different cancer types. These findings demonstrate that metabolic subtypes may be valuable prognostic indicators in HCC patients.

Effects of Environmental pH on the Growth of Gastric Cancer Cells

Background

Proton pump inhibitor (PPI) and other acid-suppressing drugs are widely used in the treatment of gastrointestinal ulcer, upper gastrointestinal bleeding, gastritis, and gastric cancer (GC). About 80% of GC patients receive acid suppression treatment. PPI suppresses the production of gastric acid by inhibiting the function of H⁺/K⁺-ATPase in gastric parietal cells and raises the pH value to achieve therapeutic purposes. Some studies have found that PPI had a certain antitumor effect in the proliferation and apoptosis of tumor cells. But the effects of environmental pH on the growth of GC cells and its mechanism are unknown. Therefore, we hoped to find the effects of culture medium pH on the biological behavior of GC cells by in vitro experiments and provide guidance for the use of acid-suppressing drugs in GC patients.

Aims

We aimed to observe the effects of pH changes in GC cell culture medium on the cell biological behavior of cancer cells and to analyze the potential mechanisms. We hoped to find out the effect of acid suppression on the growth of GC cells.

Methods

The GC cell lines (SGC-7901 and MKN45) were used as the research object. We adjusted the pH value in the cell culture medium to observe the changes in cell viability (MTT), apoptosis (flow cytometry), and invasion (Transwell) at pH 6, pH 7, and pH 8. qRT-PCR and western blot (WB) assays were used to determine the expression changes of genes and proteins (mTOR, AKT, Wnt, Glut, and HIF-1α) at pH 6, pH 7, and pH 8.

Results

The results of MTT showed that the viability of SGC-7901 and MKN45 in the pH 8.0 group was significantly weaker than that in the pH 6.0 or pH 7.0 group (P < 0.001). Flow cytometry results showed that the apoptosis of SGC-7901 and MKN45 in the pH 8.0 group was more obvious than that in the pH 6.0 or pH 7.0 group (P < 0.001). Flow cytometry results showed that the apoptosis of SGC-7901 and MKN45 in the pH 8.0 group was more obvious than that in the pH 6.0 or pH 7.0 group (P < 0.001). Flow cytometry results showed that the apoptosis of SGC-7901 and MKN45 in the pH 8.0 group was more obvious than that in the pH 6.0 or pH 7.0 group (α) at pH 6, pH 7, and pH 8. P < 0.001). Flow cytometry results showed that the apoptosis of SGC-7901 and MKN45 in the pH 8.0 group was more obvious than that in the pH 6.0 or pH 7.0 group (

Conclusions

Compared with the microacid environment, the microalkaline environment inhibited the viability, invasion, and expression of genes and proteins (mTOR, AKT, Wnt, Glut, and HIF-1α) but promoted the apoptosis of GC cells and thus inhibited the growth of GC.α) at pH 6, pH 7, and pH 8.

The Metabolic Inhibitor CPI-613 Negates Treatment Enrichment of Ovarian Cancer Stem Cells

One of the most significant therapeutic challenges in the treatment of ovarian cancer is the development of recurrent platinum-resistant disease. Cancer stem cells (CSCs) are postulated to contribute to recurrent and platinum-resistant ovarian cancer (OvCa). Drugs that selectively target CSCs may augment the standard of care cytotoxics and have the potential to prevent and/or delay recurrence. Increased reliance on metabolic pathway modulation in CSCs relative to non-CSCs offers a possible therapeutic opportunity. We demonstrate that treatment with the metabolic inhibitor CPI-613 (devimistat, an inhibitor of tricarboxylic acid (TCA) cycle) in vitro decreases CD133+ and CD117+ cell frequency relative to untreated OvCa cells, with negligible impact on non-CSC cell viability. Additionally, sphere-forming capacity and tumorigenicity in vivo are reduced in the CPI-613 treated cells. Collectively, these results suggest that treatment with CPI-613 negatively impacts the ovarian CSC population. Furthermore, CPI-613 impeded the unintended enrichment of CSC following olaparib or carboplatin/paclitaxel treatment. Collectively, our results suggest that CPI-613 preferentially targets ovarian CSCs and could be a candidate to augment current treatment strategies to extend either progression-free or overall survival of OvCa.

Hyperpolarized in vivo pH imaging reveals grade-dependent acidification in prostate cancer

There is an unmet clinical need for new and robust imaging biomarkers to distinguish indolent from aggressive prostate cancer. Hallmarks of aggressive tumors such as a decrease in extracellular pH (pH_e) can potentially be used to identify aggressive phenotypes. In this study, we employ an optimized, high signal-to-noise ratio hyperpolarized (HP) ¹³C pH_e imaging method to discriminate between indolent and aggressive disease in a murine model of prostate cancer. Transgenic adenocarcinoma of the mouse prostate (TRAMP) mice underwent a multiparametric MR imaging exam, including HP [¹³C] bicarbonate MRI for pH_e, with ¹H apparent diffusion coefficient (ADC) mapping and HP [1-¹³C] pyruvate MRI to study lactate metabolism. Tumor tissue was excised for histological staining and qRT-PCR to quantify mRNA expression for relevant glycolytic enzymes and transporters. We observed good separation in pH_e between low- and high-grade tumor regions, with high-grade tumors demonstrating a lower pH_e. The pH_e also correlated strongly with monocarboxylate transporter Mct4 gene expression across all tumors, suggesting that lactate export via MCT4 is associated with acidification in this model. Our results implicate extracellular acidification as an indicator of indolent-to-aggressive transition in prostate cancer and suggest feasibility of HP pH_e imaging to detect high-grade, clinically significant disease in men as part of a multiparametric MRI examination.

Cationic Modulation of Voltage-Gated Sodium Channel (Nav1.5): Neonatal Versus Adult Splice Variants-1. Monovalent (H+) Ions

Background: Voltage-gated sodium channels are functionally expressed in human carcinomas. In breast and colon cancers, the neonatal splice variant of Nav1.5 (nNav1.5) is dominant. This differs from the adult (aNav1.5) by several amino acids, including an outer charge reversal (residue-211): negatively charged aspartate (aNav1.5) versus positively charged lysine (nNav1.5). Thus, nNav1.5 and aNav1.5 may respond to extracellular charges differently. Materials and Methods: We used whole-cell patch-clamp recording to compare the electrophysiological effects of the monovalent cation hydrogen (H+) on nNav1.5 and aNav1.5 expressed stably in EBNA cells. Results: Increasing the H+ concentration (acidifying pH) reduced channel conductance and inhibited peak currents. Also, there was a positive shift in the voltage dependence of activation. These changes were significantly smaller for nNav1.5, compared with aNav1.5. Conclusions: nNav1.5 was more resistant to the suppressive effects of acidification compared with aNav1.5. Thus, nNav1.5 may have an advantage in promoting metastasis from the acidified tumor microenvironment.

Ivermectin induces cell cycle arrest and apoptosis of HeLa cells via mitochondrial pathway

OBJECTIVES

The aim of study was to investigate the anticancer activities of Ivermectin (IVM) and the possible mechanisms in cells level via cell proliferation inhibition, apoptosis and migration inhibition in model cancer cell HeLa.

MATERIALS AND METHODS

The MTT assay was used to study the inhibitory effect of IVM on the proliferation of Hela cells, and the cell cycle was analysed by flow cytometry. The neutral comet assay was used to study the DNA damage. The presence of apoptosis was confirmed by DAPI nuclear staining and flow cytometry. Changes in mitochondrial membrane potential and reactive oxygen species (ROS) levels were determined using Rhodamine 123 staining and DCFH-DA staining. Western blot analysis for apoptosis-related proteins was carried out. We use scratch test to analyse the antimigration potential of IVM.

RESULTS

Ivermectin can inhibit the viability of HeLa cells significantly. In addition, treatment with IVM resulted in cell cycle arrest at the G1/S phase which partly account for the suppressed proliferation. Typical apoptosis morphological changes were shown in IVM treatment cells including DNA fragmentation and chromatin condensation. At the same time, the results of flow cytometry analysis showed that the number of apoptotic cells increased significantly with the increase of IVM concentration. Moreover, we observed that the mitochondrial membrane potential collapses and the ratio of Bax/Bcl-2 in the cytoplasm increases, which induces cytochrome c release from the mitochondria to the cytoplasm, activates caspase-9/-3 and finally induces apoptosis. We also found that IVM can significantly increase intracellular ROS content. At the same time, we determined that IVM can significantly inhibit the migration of HeLa cells.

CONCLUSIONS

Our experimental results show that IVM might be a new potential anticancer drug for therapy of human cancer.

"Smart" Nanoprobes for Visualization of Tumor Microenvironments

Physiological parameters in tumor microenvironments, including hypoxia, low extracellular pH, enzymes, reducing conditions, and so on, are closely associated with the proliferation, angiogenesis, invasion, and metastasis of cancer, and impact the therapeutic administrations. Therefore, monitoring the tumor microenvironment is significant for diagnosing tumors, predicting the invasion potential, evaluating therapeutic efficacy, planning the treatment, and cancer prognostics. Noninvasive molecular imaging technologies combined with novel "smart" nanoparticle-based activatable probes provide a feasible approach to visualize tumor-associated microenvironment factors. This review summarizes recent achievements in the designs of "smart" molecular imaging nanoprobes responding to the tumor microenvironment-related features, and highlights the state of the art in tumor heterogeneity imaging.

Repositioning of proton pump inhibitors in cancer therapy

Drug repositioning, as a smart way to exploit new molecular targets of a known drug, has been gaining increasing attention in the discovery of anti-cancer drugs. Proton pump inhibitors (PPIs) as benzimidazole derivatives, which are essentially H⁺-K⁺-ATPases inhibitors, are commonly used in the treatment of acid-related diseases such as gastric ulcer. In recent years, exploring the new application of PPIs in anti-cancer field has become a hot research topic. Interestingly, cancer cells display an alkaline intracellular pH and an acidic extracellular pH. The extracellular acidity of tumors can be corrected by PPIs that are selectively activated in an acid milieu. It is generally believed that PPIs might provoke disruption of pH homeostasis by targeting V-ATPase on cancer cells, which is the theoretical basis for PPIs to play an anti-cancer role. Numerous studies have shown specialized effects of the PPIs on tumor cell growth, metastasis, chemoresistance, and autophagy. PPIs may really represent new anti-cancer drugs due to better safety and tolerance, the potential selectivity in targeting tumor acidity, and the ability to inhibit mechanism pivotal for cancer homeostasis. In this review, we focus on the new therapeutic applications of PPIs in multiple cancers, explaining the rationale behind this approach and providing practical evidence.

Cellular acidification as a new approach to cancer treatment and to the understanding and therapeutics of neurodegenerative diseases

During the last few years, the understanding of the dysregulated hydrogen ion dynamics and reversed proton gradient of cancer cells has resulted in a new and integral pH-centric paradigm in oncology, a translational model embracing from cancer etiopathogenesis to treatment. The abnormalities of intracellular alkalinization along with extracellular acidification of all types of solid tumors and leukemic cells have never been described in any other disease and now appear to be a specific hallmark of malignancy. As a consequence of this intracellular acid-base homeostatic failure, the attempt to induce cellular acidification using proton transport inhibitors and other intracellular acidifiers of different origins is becoming a new therapeutic concept and selective target of cancer treatment, both as a metabolic mediator of apoptosis and in the overcoming of multiple drug resistance (MDR). Importantly, there is increasing data showing that different ion channels contribute to mediate significant aspects of cancer pH regulation and etiopathogenesis. Finally, we discuss the extension of this new pH-centric oncological paradigm into the opposite metabolic and homeostatic acid-base situation found in human neurodegenerative diseases (HNDDs), which opens novel concepts in the prevention and treatment of HNDDs through the utilization of a cohort of neural and non-neural derived hormones and human growth factors.

Synthesis and biological assessment of novel N-(hydroxy/methoxy)alkyl β-enaminone curcuminoids

Curcumin, a natural compound extracted from the rhizomes of Curcuma Longa, is known to display pronounced anticancer activity but lacks good pharmacokinetic properties. In that respect, augmenting the water solubility by structural modification of the curcumin scaffold may result in improved bioavailability and pharmacokinetics. A possible scaffold modification, especially important for this study, concerns the imination of the labile β-diketone moiety in curcumin. Previous work revealed that novel N-alkyl β-enaminones showed a similar water solubility as compared to curcumin, accompanied by a stronger anti-proliferative activity. To extend this β-enaminone compound library, new analogues were prepared in this work using more polar amines (hydroxyalkylamines and methoxyalkylamines instead of alkylamines) with the main purpose to improve the water solubility without compromising the biological activity of the resulting curcuminoids. Compared to their respective parent compounds, i.e. curcumin and bisdemethoxycurcumin, the bisdemethoxycurcumin N-(hydroxy/methoxy)alkyl enaminone analogues showed better water solubility, antioxidant and anti-proliferative activities. In addition, the curcumin enaminones displayed activities comparable to or better than curcumin, and the water solubility was improved significantly. The constructed new analogues may thus be of interest for further exploration concerning their impact on oxidative stress related diseases such as cancer.

Ultrasound-mediated destruction of oxygen and paclitaxel loaded lipid microbubbles for combination therapy in hypoxic ovarian cancer cells

We synthesized oxygen and paclitaxel (PTX) loaded lipid microbubbles (OPLMBs) for ultrasound mediated combination therapy in hypoxic ovarian cancer cells. Our experiments successfully demonstrated that ultrasound induced OPLMBs destruction significantly enhanced the local oxygen release. We also demonstrated that OPLMBs in combination with ultrasound (300 kHz, 0.5 W/cm(2), 15s) yielded anti-proliferative activities of 52.8 ± 2.75% and cell apoptosis ratio of 35.25 ± 0.17% in hypoxic cells at 24h after the treatment, superior to other treatment groups such as PTX only and PTX-loaded MBs (PLMBs) with or without ultrasound mediation. RT-PCR and Western blot tests further confirmed the reduced expression of HIF-1α and MDR-1/P-gp after ultrasound mediation of OPLMBs. Our experiment suggests that ultrasound mediation of oxygen and drug-loaded MBs may be a useful method to overcome chemoresistance in the hypoxic ovarian cancer cells.

Stitching of tyrosine and 10H-acridin-9-one: turn-ON fluorescence in the narrow pH range 7.4–8.5 and intracellular labelling of cancer cells

We tailored 10H-acridin-9-one and (S)-tyrosine into 3-(4-hydroxyphenyl)-2-[(9-oxo-9,10-dihydroacridine-4-carbonyl) amino]propionic acid (2).

Expression of hypoxic marker carbonic anhydrase IX predicts poor prognosis in resectable hepatocellular carcinoma

Carbonic anhydrase IX (CA-IX), a hypoxia marker, correlates with tumor progression in a variety of human cancers. However, the role of CA-IX in hepatocellular carcinomas (HCCs) remains largely unknown. We examined the expression of 277 unifocal, resectable, primary HCC tumors using immunohistochemistry. The CA-IX protein was expressed in 110 of the 227 (48.5%) HCC tumors. The expression of CA-IX correlated with younger age (P = 0.0446), female sex (P = 0.0049), high serum α-fetoprotein levels (P<1x10^-6), larger tumor size (P = 0.0031), high tumor grade P<1x10^-6) and high tumor stage (P = 1.5x10^-6). Patients with HCC tumors that expressed CA-IX were more likely to have lower 5-year disease-free survival (DFS; P = 0.0001) and 5-year overall survival (OS; P<1x10^-6). The multivariate analysis indicated that CA-IX expression was an independent predictor for high tumor stage (P = 0.0047) and DFS (P = 0.0456), and a borderline predictor for OS (P = 0.0762). Furthermore, CA-IX expression predicted poor DFS and OS in patients with high tumor stage (P = 0.0004 and P<1x10^-6, respectively). Interestingly, CA-IX expression might contribute to the worse prognosis of female patients with advanced HCCs. Our study indicates the expression of the CA-IX protein is a crucial predictor of poor prognosis in resectable HCC, and it is also an unfavorable prognostic predictor in HCC patients with high tumor stage.

Bleb formation is induced by alkaline but not acidic pH in estrogen receptor silenced breast cancer cells

De novo and acquired resistance to endocrine-based therapies in breast cancer occurs in parallel with epithelial to mesenchymal transition (EMT), which is associated with enhanced proliferative and metastatic potential, and poor clinical outcome. We have established several endocrine insensitive breast cancer lines by shRNA-induced depletion of estrogen receptor (ER) by transfection of MCF7 cells. All of these exhibit EMT. We have previously reported that brief exposure of specifically ER- breast cancer cells, to extracellular alkaline pH, results in cell rounding and segregation, and leads to enhanced invasive potential. In this study we describe more detailed morphological changes and compare these with cell exposure to acidic pH. Morphological changes and localization of various molecules critical for cell adhesion and motility, associated with pH effects, were assessed by live cell microscopy, electron microscopy, and immunofluorescence. Exposure of either ER- or ER+ breast cancer cells to extracellular acidic pH did not induce significant changes in morphological appearance. Conversely, brief exposure of specifically ER silenced cells, to alkaline pH, resulted in cell contractolation and formation of bleb-like actin-rich structures which were evenly distributed on the outer membrane. Integrin α2, FAK, and JAM-1 were found in the cytoplasm streaming into the newly formed blebs. These blebs appear to be related to cell polarity and movement. Pre-treatment with cytochalasin-D or inhibitors of Rho or MLCK prevented both contractolation and bleb formation. Our data suggest that the effect of pH on the microenvironment of endocrine resistant breast cancer cells needs to be more extensively investigated. Alkaline, rather than acidic pH, appears to induce dramatic morphological changes, and enhances their invasive capabilities, through re-organization of cortical actin.

A 3-D multicellular tumor spheroid on ultrathin matrix coated single cancer cells provides a tumor microenvironment model to study epithelial-to-mesenchymal transitions

We report a 3D tumor spheroid model to study epithelial-to-mesenchymal transitions (EMT) using ultra-thin matrix coated single cancer cells.

3D tissue-engineered model of Ewing's sarcoma

Despite longstanding reliance upon monolayer culture for studying cancer cells, and numerous advantages from both a practical and experimental standpoint, a growing body of evidence suggests that more complex three-dimensional (3D) models are necessary to properly mimic many of the critical hallmarks associated with the oncogenesis, maintenance and spread of Ewing's sarcoma (ES), the second most common pediatric bone tumor. And as clinicians increasingly turn to biologically-targeted therapies that exert their effects not only on the tumor cells themselves, but also on the surrounding extracellular matrix, it is especially important that preclinical models evolve in parallel to reliably measure antineoplastic effects and possible mechanisms of de novo and acquired drug resistance. Herein, we highlight a number of innovative methods used to fabricate biomimetic ES tumors, encompassing both the surrounding cellular milieu and the extracellular matrix (ECM), and suggest potential applications to advance our understanding of ES biology, preclinical drug testing, and personalized medicine.

Regulatory effect of merlin-1 on adhesion/metastasis and cytoskeleton remodeling in gastric cancer cells under hypoxia

AIM: To investigate the regulatory effect of merlin-1 on cell proliferation, adhesion/metastasis and cytoskeleton remodeling in gastric cancer cells under hypoxia from Qinghai Han-, Hui- and Tibetan-ethnic patients, and to study if the function of merlin-1 in different ethnic groups is related to ethnic specificity under normoxic or hypoxic conditions.

METHODS: MTT assay was used to analyze the influence of merlin-1 on the cell proliferation, adhesion/metastasis and motility, and immunofluorescence staining was performed to detect cytoskeleton remodeling, morphological changes, and the distribution of microvilli on the surface of gastric cancer cells from Han-, Hui- and Tibetan-ethnic patients. In addition, we explored whether the function of merlin-1 in different ethnic groups is correlated with ethnic specificity under normoxic or hypoxic conditions.

RESULTS: The proliferation of gastric cancer cells from Han-, Hui- and Tibetan-ethnic groups was inhibited by merlin-1 under both normoxic and conditions (P_normoxic = 0.00, 0.00, 0.00; P_hypoxic = 0.00, 0.00, 0.00), and the influence of merlin-1 on cancer cell proliferation was not related to ethnic specificity (P_normoxic ≥ 0.05; P_hypoxic ≥ 0.05). The results of adhesion/metastasis analysis showed that merlin-1 inhibited the adhesion/metastasis ability of gastric cancer cells from Han-, Hui- and Tibetan-ethnic groups under both normoxic and hypoxic conditions (P_normoxic = 0.00, 0.00, 0.00; P_hypoxic = 0.00, 0.00, 0.00), and the inhibitory effect of merlin-1 in three ethnic groups showed no significant differences [P_normoxic = 0.51 (3 h), 0.07 (48 h); P_hypoxic = 0.47 (3 h), 0.17 (48 h)]. By detection of cytoskeleton remodeling, morphological change and microvilli distribution, it was found that merlin-1 enhanced cytoskeleton remodeling under hypoxic conditions compared with normoxic conditions.

CONCLUSION: Merlin-1 can inhibit the proliferation and adhesion/metastasis of gastric cancer cells under both hypoxic and normoxic conditions, which is independent on the ethnicity of patients from whom gastric cancer cells are obtained. However, merlin-1 enhances cytoskeleton remodeling under hypoxic conditions.

Upregulation of autophagy by hypoxia-inducible factor-1α promotes EMT and metastatic ability of CD133+ pancreatic cancer stem-like cells during intermittent hypoxia

Epithelial-to-mesenchymal transition (EMT) facilitates the escape of pancreatic cancer cells from the primary tumor site, which is a key early event in metastasis. In the present study, we examined if intermittent hypoxia facilitates the invasiveness of human pancreatic cancer cell lines (Panc-1 and BxPC-3) by Transwell assay. We used western blotting and flow cytometry analysis to quantify stem-like cells in the migratory cells during intermittent hypoxia in the human pancreatic cancer cells. Under normoxia or intermittent hypoxia, the expression of autophagy-related proteins (LC3-II and Beclin), hypoxia-inducible factor-1α (HIF-1α) and EMT-related markers (E-cadherin, Vimentin and N-cadherin) was examined by western blotting. siRNA and the autophagic inhibitor were used to access the role of HIF-1α and autophagy in promoting metastasis and EMT. Under intermittent hypoxia, pancreatic cancer cells demonstrated enhanced invasive ability and enriched stem-like cells. The migratory cells displayed stem-like cell characteristics and elevated the expression of LC3-II and Beclin-1, HIF-1α, E-cadherin, Vimentin and N-cadherin under intermittent hypoxia conditions. Moreover, enhanced autophagy was induced by the elevated level of HIF-1α. The metastatic ability and EMT of pancreatic cancer stem cells was associated with HIF-1α and autophagy. This novel finding may indicate the specific role of HIF-1α and autophagy in promoting the metastatic ability of pancreatic cancer stem cells. Additionally, it emphasizes the importance of developing therapeutic strategies targeting cancer stem cells and autophagy to reduce metastasis.