Hypoxia-induced Drug Resistance Research Articles

Cisplatin-activated and hemoglobin-mediated injectable hydrogel system for antitumor chemodynamic and chemotherapy

Low specificity and hypoxia-induced drug resistance are significant challenges in traditional cancer treatment. To enhance the anticancer efficacy, an injectable hydrogel system is developed through the formation of dynamic covalent bonds in hyaluronic acid, allowing for localized controlled release of drugs. This system also utilizes double-stranded DNA sequences for the intercalation delivery of the chemotherapeutic drug, enabling a multifaceted approach to therapy. Cisplatin not only serves as a chemotherapy drug but also acts as a catalyst for chemodynamic therapy (CDT) to initiate CDT cascades by creating hydrogen peroxide for the Fenton reaction. Hemoglobin, enclosed in PLGA nanoparticles, provides ferrous ions that react with hydrogen peroxide in an acidic environment, yielding hydroxyl radicals that induce cancer cell death. Additionally, oxygen released from hemoglobin mitigates hypoxia-induced chemoresistance, bolstering overall anticancer efficacy. Results demonstrate the shear-thinning properties and injectability of the hydrogel. Cisplatin elevates intracellular hydrogen peroxide levels in tumor cells, while hemoglobin efficiently releases ferrous ions and generates reactive oxygen species (ROS) in the presence of hydrogen peroxide. In in vitro and in vivo study, the combinational use of chemo- and chemodynamic therapies achieves a synergistic anticancer effect on combating glioblastoma. In summary, our CDT-based hydrogel, activated by endogenous cues and mediated by chemo drugs, spontaneously produces ROS and ameliorates the adverse tumor microenvironment with rational and selective antitumor strategies.

Abstract 374: Hypoxia-induced mitochondrial glutathione transporter expression causes drug resistance in colorectal cancer

Abstract Colorectal cancer (CRC) is the third most common type of cancer worldwide, with higher incidence and mortality rates. In order to adapt stress conditions during cancer progression, the cancer cells will be subject to metabolism reprogramming to increase energy production and remove hazardous substances. One of the important organelles, mitochondria is responsible for cellular ATP production, ion homeostasis, and several metabolic pathways. Therefore, mitochondria require a series of transporters called solute carrier family 25 (SLC25) to transport metabolites crossing the mitochondrial inner membrane, and dysregulation of those transporters causes abnormal cell morphology and diseases. In this study, members of the SLC25 family were analyzed in CRC via bioinformatics analysis, and a mitochondrial glutathione transporter was identified to overexpress in several public datasets of CRC and our own clinical specimens. In addition, its role has not been reported in any disease, including cancer. To systemically analyze the underlying mechanism causing overexpression of glutathione transporter during CRC progression, several stress conditions had been applied to colon cancer cells. However, only hypoxia was identified to induce its protein expression but not mRNA expression. Since a previous study reported that glutathione deprivation induced its protein expression, hypoxia didn’t alter the abundance of glutathione level suggesting that another glutathione-independent regulatory mechanism might be involve it. Interestingly, our findings revealed that hypoxia-induced glutathione transporter protein expression was mediated through the activation of internal ribosome binding site-mediated translation under hypoxia. To identify the potential role of glutathione transporter during colon cancer progression, its mitochondrial metabolite profiles from knockout cells of previous studies were further analyzed and identified that the changes of metabolites were associated with the urea cycle which had been reported to be associated with the sensitivity of oxaliplatin and 5-fluorouracil (5-FU) in cancer treatment. Importantly, our results showed that hypoxia-attenuated those chemotherapeutic effects were abolished by loss of glutathione transporter in colon cancer cells, indicating its crucial role in hypoxia-induced drug resistance. In conclusion, our study shows that glutathione transporter increased by hypoxia might lead to drug resistance of cancer therapy in colon cancer. Citation Format: Chin-Chun Lin. Hypoxia-induced mitochondrial glutathione transporter expression causes drug resistance in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 374.

Enhancing chemotherapy for pancreatic cancer through efficient and sustained tumor microenvironment remodeling with a fibroblast-targeted nanosystem

Pancreatic cancer (PC) carries a poor prognosis among all malignancies and poses great challenges to clinical drug accessibility due to the severely fibrotic and hypoxic tumor microenvironment (TME). Therein, cancer-associated fibroblasts (CAFs), which are extremely abundant in PC, play a key role in forming the complex PC microenvironment. Therefore, a highly efficient TME reprogramming therapeutic paradigm that can specifically inhibit CAF function is urgently needed. Herein, we successfully developed a novel CAF-tailored nanosystem (Dex-GP-DOCA, DPD) loaded with a potent anti-fibrosis flavonoid compound (Quercetin, QUE), which possesses biological responsiveness to fibroblast activation protein alpha (FAP-α), prolonged TME remodeling and enhancement of clinical chemotherapeutics. Specifically, DPD/QUE allowed for extracellular matrix (ECM) reduction, vessel normalization, hypoxia-induced drug resistance reversal, and blockade of Wnt16 paracrine in CAFs. More importantly, this chemotherapy conducive microenvironment persisted for at least 8 days following treatment with DPD/QUE. It should also be noted that the effective and prolonged microenvironment modulation induced by DPD/QUE significantly improved the chemotherapy sensitivity of Abraxane and gemcitabine, the first-line chemotherapeutic drugs for PC, with inhibition rates increasing from 37.5% and 40.0% to 87.5% and 85.2%, respectively. Overall, our CAFs-targeted nanosystem showed promising prospects for remodeling the TME and facilitating chemotherapy for refractory pancreatic cancer.

Monoacylglycerol Lipase Inhibitor JJKK048 Ameliorates ABCG2 Transporter-Mediated Regorafenib Resistance Induced by Hypoxia in Triple Negative Breast Cancer Cells

Triple negative breast cancer (TNBC) is among the most aggressive and deadly cancer subtypes. Intra-tumoral hypoxia is associated with aggressiveness and drug resistance in TNBC. One of the underlying mechanisms of hypoxia-induced drug resistance is the elevated expression of efflux transporters such as breast cancer resistant protein (ABCG2). In the present study, we investigated the possibility of ameliorating ABCG2-mediated drug resistance in hypoxic TNBC cells by monoacylglycerol lipase (MAGL) inhibition and the consequent downregulation of ABCG2 expression.The effect of MAGL inhibition on ABCG2 expression, function, and efficacy of regorafenib, an ABCG2 substrate was investigated in cobalt dichloride (CoCl2) induced pseudohypoxic TNBC (MDA-MB-231) cells, using quantitative targeted absolute proteomics, qRT-PCR, anti-cancer drug accumulation in the cells, cell invasiveness and resazurin-based cell viability assays.Our results showed that hypoxia-induced ABCG2 expression led to low regorafenib intracellular concentrations, reduced the anti-invasiveness efficacy, and elevated half maximal inhibitory concentration (IC50) of regorafenib in vitro MDA-MB-231 cells. MAGL inhibitor, JJKK048, reduced ABCG2 expression, increased regorafenib cell accumulation, which led to higher regorafenib efficacy.In conclusion, hypoxia-induced regorafenib resistance due to ABCG2 over-expression in TNBC cells can be ameliorated by MAGL inhibition.

An injectable, in situ forming and NIR-responsive hydrogel persistently reshaping tumor microenvironment for efficient melanoma therapy

BackgroundMelanoma is a highly aggressive form of skin cancer with increasing incidence and mortality rates. Chemotherapy, the primary treatment for melanoma, is limited by hypoxia-induced drug resistance and suppressed immune response at the tumor site. Modulating the tumor microenvironment (TME) to alleviate hypoxia and enhance immune response has shown promise in improving chemotherapy outcomes.MethodsIn this study, a novel injectable and in situ forming hydrogel named MD@SA was developed using manganese dioxide (MnO2) nanosheets pre-loaded with the chemotherapy drug doxorubicin (DOX) and mixed with sodium alginate (SA). The sustainable drug delivery, oxygen generation ability, and photothermal property of MD@SA hydrogel were characterized. The therapeutic efficacy of hydrogel was studied in B16F10 in vitro and B16F10 tumor-bearing mice in vivo. The immune effects on macrophages were analyzed by flow cytometry, real-time quantitative reverse transcription PCR, and immunofluorescence analyses.ResultsThe MD@SA hydrogel catalyzed the tumoral hydrogen peroxide (H2O2) into oxygen, reducing the hypoxic TME, down-regulating hypoxia-inducible factor-1 alpha (HIF-1α) and drug efflux pump P-glycoprotein (P-gp). The improved TME conditions enhanced the uptake of DOX by melanoma cells, enhancing its efficacy and facilitating the release of tumor antigens. Upon NIR irradiation, the photothermal effect of the hydrogel induced tumor apoptosis to expose more tumor antigens, thus re-educating the M2 type macrophage into the M1 phenotype. Consequently, the MD@SA hydrogel proposes an ability to constantly reverse the hypoxic and immune-inhibited TME, which eventually restrains cancer proliferation.ConclusionThe injectable and in situ forming MD@SA hydrogel represents a promising strategy for reshaping the TME in melanoma treatment. By elevating oxygen levels and activating the immune response, this hydrogel offers a synergistic approach for TME regulation nanomedicine.

Interaction of pregnane X receptor with hypoxia-inducible factor-1 regulates chemoresistance of prostate cancer cells.

Aim: The nuclear pregnane X receptor (PXR) is a pivotal regulator of steroid and xenobiotics metabolism and plays an important role in shaping tumor cell responses to chemotherapy. Hypoxia within tumor tissue has multifaceted effects, including multiple drug resistance. The goal of this study was to determine whether PXR contributes to hypoxia-induced drug resistance. Methods: Metastatic prostate cancer cells were used to study the interaction of PXR and hypoxia-inducible factor-1 (HIF-1 in drug resistance associated with hypoxia. The activities of PXR and HIF-1 were determined by assays for its reporter gene or target gene expression. Co-immunoprecipitation (Co-IP) was used to determine the interaction of PXR and HIF-1. Ablation or inhibition of PXR or HIF-1 was used to determine their roles in hypoxia-induced chemoresistance. Results: PXR was activated by hypoxia, leading to increased expression of multidrug resistance protein 1 (MDR1). Inhibition of PXR by pharmacological compounds or depletion by shRNAs reduced the hypoxic induction of MDR1 and sensitized prostate cancer cells to chemotherapy under hypoxia. HIF-1 was required for PXR activation under hypoxia. Co-immunoprecipitation results showed that HIF-1 and PXR could physically interact with each other, leading to crosstalk between these two transcription factors. Conclusion: PXR contributes to hypoxia-induced drug resistance in prostate cancer cells through its interaction with HIF-1.

A BODIPY-based activatable nanotheranostics for tumor hypoxia imaging and hypoxia-induced drug resistance reversal

Tumor hypoxic microenvironment contributes to AZD9291 (osimertinib) resistance in non-small cell lung cancer (NSCLC). Developing hypoxia-triggered theranostic formulation for simultaneous hypoxia tumor imaging and oxygen-independent photothermal therapy (PTT) will be an effective strategy to overcome AZD9291 resistance under hypoxic conditions. Herein, we designed and synthesized a boron-dipyrromethene (BODIPY) dye-modified chitosan (CsB) linked through a hypoxia-responsive azobenzene group and fabricated a nanoplatform CsBANs self-assembled by CsB and AZD9291 to achieve hypoxia-responsive imaging and synergistic PTT/targeted molecular therapy. CsBANs exhibited excellent cellular uptake efficiency and hypoxia imaging capacity either in two-dimensional NSCLC cell cultures under hypoxia or in multicellular tumor spheroids. The in vitro and in vivo results showed that the photothermal effects of BODIPY and AZD9291 could induce satisfactory anticancer effects in NSCLC cell lines and in xenograft mouse model. Hence, this work presents a promising hypoxia-activated nanotheranostic platform to deal with hypoxia-induced AZD9291 resistance and for other hypoxia-related diseases.

Rational Modulation of BODIPY Photosensitizers to Design Metal-Organic Framework-Based NIR Nanocomposites for High-Efficiency Photodynamic Therapy in a Hypoxic Environment.

Photodynamic therapy (PDT) is a promising noninvasive treatment that has drawn great attention. However, the hypoxic environment in tumors seriously limits the therapeutic effect of oxygen-dependent chemicals and PDT. Herein, a versatile nanocomposite DF-BODIPY@ZIF-8 with oxygen-generating ability was developed based on zeolitic imidazolate framework-8 (ZIF-8) by loading the near-infrared photosensitizer DF-BODIPY to overcome hypoxia-induced drug resistance in cancer therapy. ZIF-8 can catalyze the decomposition of hydrogen peroxide in tumors and increase the dissolved oxygen concentration, resulting in a significant improvement in PDT efficacy. Additionally, we found that enhancing the electronegativity of substituents can effectively reduce the energy level difference (ΔEst) between the minimum singlet state (S1) and the lowest triplet state (T1), leading to the enhancement of the singlet oxygen quantum yield. In vitro experiments suggested that DF-BODIPY@ZIF-8 indeed had a higher singlet oxygen quantum yield and better tumor cell phototoxicity than free DF-BODIPY. In vivo experiments also demonstrated that DF-BODIPY@ZIF-8 could effectively eliminate 4T1 tumors under light irradiation. Thus, we conclude that increasing the electronegativity of substituents and introducing a ZIF-8 material can effectively improve the singlet oxygen quantum yield and overcome the hypoxia limitations for high-efficiency PDT.

Hypoxia induces docetaxel resistance in triple-negative breast cancer via the HIF-1α/miR-494/Survivin signaling pathway

Cytotoxic chemotherapy is the major strategy to prevent and reduce triple-negative breast cancer (TNBC) progression and metastasis. Hypoxia increases chemoresistance and is associated with a poor prognosis for patients with cancer. Based on accumulating evidence, microRNAs (miRNAs) play an important role in acquired drug resistance. However, the role of miRNAs in hypoxia-induced TNBC drug resistance remains to be clarified. Here, we found that hypoxia induced TNBC docetaxel resistance by decreasing the miR-494 level. Modulating miR-494 expression altered the sensitivity of TNBC cells to DTX under hypoxic conditions. Furthermore, we identified Survivin as a direct miR-494 target. Hypoxia upregulated survivin expression. In a clinical study, the HIF-1α/miR-494/Survivin signaling pathway was also active in primary human TNBC, and miR-494 expression negatively correlated with HIF-1α and survivin expression. Finally, in a xenograft model, both miR-494 overexpression and the HIF-1α inhibitor PX-478 increased the sensitivity of TNBC to DTX by suppressing the HIF-1α/miR-494/Survivin signaling pathway in vivo. In conclusion, treatments targeting the HIF-1α/miR-494/Survivin signaling pathway potentially reverse hypoxia-induced drug resistance in TNBC.

Hypoxia-responsive nanocarriers for chemotherapy sensitization via dual-mode inhibition of hypoxia-inducible factor-1 alpha

The overexpression of hypoxia-inducible factor-1 alpha (HIF-1α) in solid tumor compromises the potency of chemotherapy under hypoxia. The high level of HIF-1α arises from the stabilization effect of reduced nicotinamideadeninedinucleotide(phosphate) NAD(P)H: quinone oxidoreductase 1 (NQO1). It was postulated that the inhibition of NQO1 could degrade HIF-1α and sensitize hypoxic cancer cells to antineoplastic agents. In the current work, we report hypoxia-responsive polymer micelles, i.e. methoxyl poly(ethylene glycol)-co-poly(aspartate-nitroimidazole) orchestrate with a NQO1 inhibitor (dicoumarol) to sensitize the ovarian cancer cell line (SKOV3) to a model anticancer agent (sorafenib) at low oxygen conditions. Both cargos were physically encapsulated in the nanoscale micelles. The placebo micelles transiently induced the depletion of reduced nicotinamideadeninedinucleotidephosphate (NADPH) as well as glutathione and thioredoxin under hypoxia, which further inactivated NQO1 because NADPH was the cofactor of NQO1. As a consequence, the expression of HIF-1α was repressed due to the dual action of dicoumarol and polymer. The degradation of HIF-1α significantly increased the vulnerability of SKOV3 cells to sorafenib-induced apoptosis, as indicated by the enhancement of cytotoxicity, and increase of caspase 3 and cytochrome C. The current work opens new avenues of addressing hypoxia-induced drug resistance in chemotherapy.

Mir-675-5p supports hypoxia-induced drug resistance in colorectal cancer cells

BackgroundThe uncontrolled proliferation of cancer cells determines hypoxic conditions within the neoplastic mass with consequent activation of specific molecular pathways that allow cells to survive despite oxygen deprivation. The same molecular pathways are often the cause of chemoresistance. This study aims to investigate the role of the hypoxia-induced miR-675-5p in 5-Fluorouracil (5-FU) resistance on colorectal cancer (CRC) cells.MethodsCRC cell lines were treated with 5-Fu and incubated in normoxic or hypoxic conditions; cell viability has been evaluated by MTT assay. MiR-675-5p levels were analysed by RT-PCR and loss and gain expression of the miRNA has been obtained by the transfection of miRNA antagomir or miRNA mimic. Total protein expression of different apoptotic markers was analysed through western blot assay. MirWalk 2.0 database search engine was used to investigate the putative targets of the miR-675-5p involved in the apoptotic process. Finally, the luciferase assay was done to confirm Caspase-3 as a direct target of the miR-675-5p.ResultsOur data demonstrated that hypoxia-induced miR-675-5p counteracts the apoptotic signal induced by 5-FU, thus taking part in the drug resistance response. We showed that the apoptotic markers, cleaved PARP and cleaved caspase-3, increased combining miR-675-5p inhibition with 5-FU treatment. Moreover, we identified pro-caspase-3 among the targets of the miR-675-5p.ConclusionOur data demonstrate that the inhibition of hypoxia-induced miR-675-5p combined with 5-FU treatment can enhances drug efficacy in both prolonged hypoxia and normoxia, indicating a possible strategy to partially overcome chemoresistance.

Hypoxia-Responsive Stereocomplex Polymeric Micelles with Improved Drug Loading Inhibit Breast Cancer Metastasis in an Orthotopic Murine Model.

Tumor metastasis is a leading cause of breast cancer-related death. Taxane-loaded polymeric formulations, such as Genexol PM and Nanoxel M using poly(ethylene glycol)-poly(d,l-lactide) (PEG-PLA) micelles as drug carriers, have been approved for the treatment of metastatic breast cancer. Unfortunately, the physical instability of PEG-PLA micelles, leading to poor drug loading, premature drug leakage, and consequently limited drug delivery to tumors, largely hinders their therapeutic outcome. Inspired by the enantiomeric nature of PLA, this work developed stereocomplex PEG-PLA micelles through stereoselective interactions of enantiomeric PLA, which are further incorporated with a hypoxia-responsive moiety used as a hypoxia-cleavable linker of PEG and PLA, to maximize therapeutic outcomes. The results showed that the obtained micelles had high structural stability, showing improved drug loading for effective drug delivery to tumors as well as other tissues. Especially, they were capable of sensitively responding to the hypoxic tumor environment for drug release, reversing hypoxia-induced drug resistance and hypoxia-promoted cell migration for enhanced bioavailability under hypoxia. In vivo results further showed that the micelles, especially at a high dose, inhibited the growth of the primary tumor and improved tumor pathological conditions, consequently remarkably inhibiting its metastasis to the lungs and liver, while not causing any systemic toxicity. Hypoxia-responsive stereocomplex micelles thus emerge as a reliable drug delivery system to treat breast cancer metastasis.

Overcoming Hypoxia-Induced Drug Resistance via Promotion of Drug Uptake and Reoxygenation by Acousto-Mechanical Oxygen Delivery.

Hypoxia-induced drug resistance (HDR) is a critical issue in cancer therapy. The presence of hypoxic tumor cells impedes drug uptake and reduces the cytotoxicity of chemotherapeutic drugs, leading to HDR and increasing the probability of tumor recurrence and metastasis. Microbubbles, which are used as an ultrasound contrast agent and drug/gas carrier, can locally deliver drugs/gas and produce an acousto–mechanical effect to enhance cell permeability under ultrasound sonication. The present study applied oxygen-loaded microbubbles (OMBs) to evaluate the mechanisms of overcoming HDR via promotion of drug uptake and reoxygenation. A hypoxic mouse prostate tumor cell model was established by hypoxic incubation for 4 h. After OMB treatment, the permeability of HDR cells was enhanced by 23 ± 5% and doxorubicin uptake was increased by 11 ± 7%. The 61 ± 14% reoxygenation of HDR cells increased the cytotoxicity of doxorubicin from 18 ± 4% to 58 ± 6%. In combination treatment with OMB and doxorubicin, the relative contributions of uptake promotion and reoxygenation towards overcoming HDR were 11 ± 7% and 28 ± 10%, respectively. Our study demonstrated that reoxygenation of hypoxic conditions is a critical mechanism in the inhibition of HDR and enhancing the outcome of OMB treatment.

Near-infrared and tumor environment Co-activated nanoplatform for precise tumor therapy in multiple models

Chemotherapy based on anti-tumor drugs is one of the most commonly utilized approaches for tumor treatment. However, the uncontrollable toxicity of these drugs to healthy tissue, insufficient therapeutic efficiency and chemotherapeutic resistance induced by hypoxic environment in most types of solid tumors still limited the clinical application of chemotherapy. Herein, a smart nanoplatform responsive to near-infrared (NIR) light and tumor-specific microenvironment is developed for precise and effective tumor therapy via chain procedures of rapid hypoxia inhibition, promoted catalytic medicine and low-resistance chemotherapy. The concept is demonstrated by co-encapsulating ferroferric oxide nanoparticles (Fe3O4 NPs, photothermal agent and catalyst), calcium peroxide (CaO2, H2O2/O2 generator) and paclitaxel (PTX, anticancer drug) into an enzyme and thermal breakable capsule, which contained a bilayer shell of hyaluronic acid (HA) and lauric acid (LA). The HA layer serves as tumor target agent to guide the nanoplatform to accumulate in tumor tissue, which would be subsequently degraded by the over-expressed hyaluronidase to expose LA layer for further activation by NIR irradiation. Due to the well-defined melting point of LA at 44°C and excellent photothermal property of Fe3O4, the LA layer undertakes a NIR-triggered phase-change to release the encapsulated therapeutic agents (CaO2, Fe3O4 and PTX) for controllable tumor therapy. The exposed CaO2 would react with water or acid in tumor cells to produce O2 and H2O2, where the O2 not only press PTX out of the capsule to accelerate its release, but reverse the hypoxic environment to inhibit the hypoxia-induced drug resistance for enhanced chemotherapy. The H2O2 would be further converted to cytotoxic hydroxyl radical by Fe3O4via catalytic medicine (Fenton reaction), resulting in an enhanced anticancer activity.Near-infrared and tumor environment co-activated nanoplatform, Effective hypoxia inhibition, Promoted catalytic medicine, Low-resistance chemotherapy, Precise tumor therapy via chain activities

Inhibition of AKT By MK2206 but Not PI3-Kinase δ By Idelalisib Is Effective Against CLL Cells in an In Vitro Model of the Hypoxic Microenvironment

Treatment of chronic lymphocytic leukemia (CLL) relies on targeting the leukemic cells that populate the bone marrow and lymph nodes. Recent studies (Shachar, Cohen et al. 2012, Muz, de la Puente et al. 2014, Valsecchi, Coltella et al. 2016) suggest that the ability of CLL cells to adapt to low oxygen tensions, particularly within the bone marrow, may play an important role in their survival, proliferation and resistance to current therapies. Understanding the mechanisms underlying hypoxia-induced drug resistance may help to identify novel treatment strategies.In this study, we compared the effects of the AKT inhibitor MK2206 and the PI3-kinase δ inhibitor idelalisib under in vitro conditions that mimic the hypoxic tumour microenvironment. MK2206 induced apoptosis of primary CLL cells in co-culture with stromal cells and caused a G0/G1 phase cell cycle arrest of OSU-CLL cells under both normoxic (21 % O2) and hypoxic (1 % O2) conditions. Consistent with other reports, no cytotoxic or cytostatic effects of idelalisib at clinically relevant doses were observed under these in vitro conditions. Treatment of both primary and OSU-CLL cells with MK2206 induced an accumulation of reactive oxygen species in the mitochondria and downregulated expression of P70-S6-kinase and Mcl-1, effects which were not observed following treatment with idelalisib.Collectively these data suggest that the anti-apoptotic and cell cycle-regulatory roles of AKT in CLL cells may not be dependent on activity of the d-isoform of PI3-kinase within the hypoxic tumour microenvironment. The efficacy of MK2206 in vitro and the toxicities associated with idelalisib suggest further studies of MK2206 may be warranted, particularly for CLL patients with bulky disease. DisclosuresNo relevant conflicts of interest to declare.

Reduction in mitochondrial oxidative stress mediates hypoxia-induced resistance to cisplatin in human transitional cell carcinoma cells

Tumor hypoxia is known to promote the acquisition of more aggressive phenotypes in human transitional cell carcinoma (TCC), including drug resistance. Accumulating evidence suggests that mitochondria play a central role in the chemoresistance of TCC. However, the role of mitochondria in the hypoxia-induced drug resistance in TCC remains elusive. The present study investigated the function of mitochondria in the drug resistance using a TCC cell line under hypoxic conditions. In vitro hypoxia (0.1% O2, 48 h) was achieved by incubating TCC cells in air chamber. Mitochondrial events involving hypoxia-induced drug resistance were assessed. Hypoxia significantly reduced the cisplatin-induced apoptosis of TCC cells. Additionally, hypoxia substantially decreased the level of mitochondrial reactive oxygen species (ROS) generated by cisplatin treatment. Analogously, elimination of mitochondrial ROS significantly rescued cells from cisplatin-induced apoptosis. Hypoxia enhanced mitochondrial hyperpolarization, which was not related to ATP production or the reversal of ATP synthase activity. The mitochondrial DNA (mtDNA) amplification efficiency data illustrated that hypoxia significantly prevented oxidative damage to the mitogenome. Moreover, transmission electron microscopy revealed that cisplatin-induced disruption of the mitochondrial ultrastructure was abated under hypoxic conditions. Notably, depletion of mtDNA by ethidium bromide abrogated hypoxia-induced resistance to cisplatin. Taken together, the present study demonstrated that TCC cells exposed to hypoxic conditions rendered mitochondria less sensitive to oxidative stress induced by cisplatin treatment, leading to enhanced drug resistance.

Hypoxia induces chemoresistance of esophageal cancer cells to cisplatin through regulating the lncRNA-EMS/miR-758-3p/WTAP axis.

Hypoxia contributes significantly to the development of chemoresistance of many malignancies including esophageal cancer (EC). Accumulating studies have indicated that long non-coding RNAs play important roles in chemotherapy resistance. Here, we identified a novel lncRNA-EMS/miR-758-3p/WTAP axis that was involved in hypoxia-mediated chemoresistance to cisplatin in human EC. Hypoxia induced the expressions of lncRNA EMS and WTAP, and reduced the expression of miR-758-3p in EC cell line ECA-109. In addition, the expressions of EMS and WTAP were required for the hypoxia-induced drug resistance to cisplatin in EC cells, while overexpression of miR-758-3p reversed such chemoresistance. The targeting relationships between EMS and miR-758-3p, as well as miR-758-3p and WTAP, were verified by luciferase-based reporter assays and multiple quantitative assays after gene overexpression/knockdown. Moreover, we found significant correlations between tumor expressions of these molecules. Notably, higher levels of EMS/WTAP, or lower levels of miR-758-3p in tumors predicted worse survivals of EC patients. Furthermore, in a xenograft mouse model, targeted knockdown of EMS and WTAP in ECA-109 cells markedly attenuated the resistance of tumors to cisplatin treatments. Our study uncovers a critical lncRNA-EMS/miR-758-3p/WTAP axis in regulating hypoxia-mediated drug resistance to cisplatin in EC.

An Original Aspirin-Containing Carbonic Anhydrase 9 Inhibitor Overcomes Hypoxia-Induced Drug Resistance to Enhance the Efficacy of Myocardial Protection.

Hypoxic microenvironment plays a vital role in myocardial ischemia injury, generally leading to the resistance of chemotherapeutic drugs. This induces an intriguing study on mechanism exploration and prodrug design to overcome the hypoxia-induced drug resistance. In this study, we hypothesized that the overexpression of carbonic anhydrase 9 (CAIX) in myocardial cells is closely related to the drug resistance. Herein, bioinformatics analysis, gene knockdown, and overexpression assay certificated the correlation between CAIX overexpression and hypoxia. An original aspirin-containing CAIX inhibitor AcAs has been developed. Based on the downregulation of CAIX level, both in vitro and in vivo, AcAs can overcome the acquired resistance and more effectively attenuate myocardial ischemia and hypoxia injury than that of aspirin. CAIX inhibitor is believed to recover the extracellular pH value so as to ensure the stable effect of aspirin. Results indicate great potential of CAIX inhibitor for further application in myocardial hypoxia injury therapy.

Targeted polymeric nanoparticle for anthracycline delivery in hypoxia-induced drug resistance in metastatic breast cancer cells.

Poly lactic-co-glycolic acid (PLGA) nanoparticles are intensively studied nanocarriers in drug delivery because of their biodegradability and biochemical characteristics. Polyethylene glycol (PEG) coating for nanocarriers gives them long circulation time in blood and makes them invisible to the reticuloendothelial system. Breast cancer cells have greater uptake of hyaluronic acid compared to normal cells as it binds to their overexpressed CD44 receptors. Since hypoxia plays an important role in cancer metastasis; we formulated PEG-PLGA nanoparticles coated with hyaluronic acid as targeted delivery system for doxorubicin (DOX) using nanoprecipitation method, and characterized them for chemical composition, size, surface charge, shape, and encapsulation efficiency. Then we tested them in vitro on hypoxia-optimized metastatic breast cancer cells. The nanoparticles were spherical with an average size of about 106 ± 53 nm, a negative surface charge (-15 ± 3 mV), and high encapsulation efficiency (73.3 ± 4.1%). In vitro investigation with hypoxia-elevated CD44 MDA-MB-231 cells showed that hyaluronic acid-targeted nanoparticles maintained their efficacy despite hypoxia-induced drug resistance unlike free DOX and nontargeted nanoparticles. In conclusion, this study revealed a simple third generation nanoparticle formulation for targeted treatment of hypoxia-induced drug resistance in breast cancer metastatic cells. Further, optimization is needed including In vivo efficacy and nanoparticle-specific pharmacokinetic studies.

The regulation of bcr-abl in hypoxia is through the mTOR pathway

Chronic myeloid leukemia (CML) is usually characterized by the formation of the fusion onco-protein bcr-abl. Therefore, the majority of CML treatments are bcr-abl specific tyrosine kinase inhibitors (TKIs). TKI resistance in CML treatment is becoming a major obstacle in managing this disease. One well-studied form of drug resistance is hypoxia-induced drug resistance, a phenomenon observed in many other cancers. This study aimed to determine the efficacy of TKIs in CML cells cultured in hypoxia. It was observed that bcr-abl translation was severely halted in hypoxia, rendering TKIs ineffective. We found that the mechanism by which bcr-abl protein levels were being suppressed in hypoxia was through the mTOR pathway, specifically via ribosomal protein S6 (RPS6). This information is vital to the improvement of CML treatments, as it can be used to determine how to best combat hypoxia-induced drug resistance in CML and subsequently to identify new targets for treatment.