Targeting Tumor Adaption to Chronic Hypoxia: Implications for Drug Resistance, and How It Can Be Overcome

Hypoxia-induced LAMB2-enriched extracellular vesicles promote peritoneal metastasis in gastric cancer via the ROCK1-CAV1-Rab11 axis

Peritoneal metastasis is one of the most common risk factors contributing to the poor prognosis of gastric cancer. We previously reported that extracellular vesicles from gastric cancer cells could facilitate peritoneal metastasis. However, their impact on gastric cancer-induced peritoneal metastasis under hypoxic conditions remains unclear. This study aims to elucidate how hypoxia-resistant gastric cancer cell-derived extracellular vesicles affect the peritoneal metastasis of normoxic gastric cancer cells. Proteomic analysis revealed elevated levels of Caveolin1 and Laminin β2 in hypoxia-resistant gastric cancer cells and their corresponding extracellular vesicles. Importantly, Caveolin1 was found to play a central role in mediating Laminin β2 sorting into extracellular vesicles derived from hypoxia-resistant gastric cancer cells, and subsequently, extracellular vesicle-associated Laminin β2 promoted peritoneal metastasis in normoxic gastric cancer cells by activating the AKT pathway. Further investigation confirmed that Caveolin1 activation by Rho-related Coiled-coil kinase 1-mediated phosphorylation of Y14 residue is a key factor facilitating Laminin β2 sorting into extracellular vesicles. Moreover, Y14 phosphorylated- Caveolin1 enhanced Laminin β2 sorting by activating Rab11. Finally, our study demonstrated that a combined assessment of plasma extracellular vesicle-associated Caveolin1 and extracellular vesicle-associated Laminin β2 could provide an accurate predictive tool for peritoneal metastasis occurrence in gastric cancer.

Cellular and Molecular Mechanisms of Chemoresistance for Gastric Cancer

Gastric cancer (GC) is one of the most common malignant tumors in the digestive tract, and chemotherapy plays an irreplaceable role in the comprehensive treatment of GC. However, chemoresistance makes it difficult for patients with GC to benefit steadily from chemotherapy in the long term, which ultimately leads to tumor recurrence, metastasis, and patient death. Elucidating the detailed mechanism of chemoresistance in GC and identifying specific therapeutic targets will help to solve the difficult problem of chemoresistance and improve the prognosis of patients with GC. This review summarizes and clarifies the cellular and molecular mechanisms underlying chemoresistance for GC.

Ultrasound-Induced Tumor Perfusion Changes and Doxorubicin Delivery: A Study on Pulse Length and Pulse Repetition Frequency

OBJECTIVES

To investigate the appropriate combination of pulse length (PL) and pulse repetition frequency (PRF) when performing ultrasound stimulated microbubble (USMB) to enhance doxorubicin (DOX) delivery to tumors.

METHODS

A total of 48 tumor-bearing mice were divided into four groups, namely groups A-D. The mice in groups B-D were treated with chemotherapy and USMB treatment with different combinations of PL and PRF, and group A was control. Contrast-enhanced ultrasound imaging was conducted to analyze tumor blood perfusion. Fluorescence microscopy and high-performance liquid chromatography were used to qualitatively and quantitatively analyse DOX release. The structural changes of tumors were observed under light microscope and transmission electron microscope. Furthermore, another 24 tumor-bearing mice were treated with sonochemotherapy and some related inflammatory factors were measured to explore the underlying mechanism.

RESULTS

With PL of three cycles and PRF of 2 kHz, the tumor perfusion area ratio increased by 26.67%, and the DOX concentration was 4.69 times higher than the control (P < .001). With PL of 34.5 cycles and PRF of 200 Hz, the tumor perfusion area ratio decreased by 12.7% and DOX did not exhibit increased extravasation compared with the control. Microvascular rupture and hemorrhage were observed after long PL and low PRF treatment. While vasodilation and higher levels of some vasodilator inflammatory factors were found after treatment with short PL and high PRF.

CONCLUSIONS

USMB treatment using short PL and high PRF could enhance tumor blood perfusion and increase DOX delivery, whereas long PL and low PRF could not serve the same purpose.

Targeting Glucose Metabolism in Cancer Cells as an Approach to Overcoming Drug Resistance

The "Warburg effect" consists of a metabolic shift in energy production from oxidative phosphorylation to glycolysis. The continuous activation of glycolysis in cancer cells causes rapid energy production and an increase in lactate, leading to the acidification of the tumour microenvironment, chemo- and radioresistance, as well as poor patient survival. Nevertheless, the mitochondrial metabolism can be also involved in aggressive cancer characteristics. The metabolic differences between cancer and normal tissues can be considered the Achilles heel of cancer, offering a strategy for new therapies. One of the main causes of treatment resistance consists of the increased expression of efflux pumps, and multidrug resistance (MDR) proteins, which are able to export chemotherapeutics out of the cell. Cells expressing MDR proteins require ATP to mediate the efflux of their drug substrates. Thus, inhibition of the main energy-producing pathways in cancer cells, not only induces cancer cell death per se, but also overcomes multidrug resistance. Given that most anticancer drugs do not have the ability to distinguish normal cells from cancer cells, a number of drug delivery systems have been developed. These nanodrug delivery systems provide flexible and effective methods to overcome MDR by facilitating cellular uptake, increasing drug accumulation, reducing drug efflux, improving targeted drug delivery, co-administering synergistic agents, and increasing the half-life of drugs in circulation.

A PDA-Functionalized 3D Lung Scaffold Bioplatform to Construct Complicated Breast Tumor Microenvironment for Anticancer Drug Screening and Immunotherapy

2D cell culture occupies an important place in cancer progression and drug discovery research. However, it limitedly models the "true biology" of tumors in vivo. 3D tumor culture systems can better mimic tumor characteristics for anticancer drug discovery but still maintain great challenges. Herein, polydopamine (PDA)-modified decellularized lung scaffolds are designed and can serve as a functional biosystem to study tumor progression and anticancer drug screening, as well as mimic the tumor microenvironment. PDA-modified scaffolds with strong hydrophilicity and excellent cell compatibility can promote cell growth and proliferation. After 96 h treatment with 5-FU, cisplatin, and DOX, higher survival rates in PDA-modified scaffolds are observed compared to nonmodified scaffolds and 2D systems. The E-cadhesion formation, HIF-1α-mediated senescence decrease, and tumor stemness enhancement can drive drug resistance and antitumor drug screening of breast cancer cells. Moreover, there is a higher survival rate of CD45+ /CD3+ /CD4+ /CD8+ T cells in PDA-modified scaffolds for potential cancer immunotherapy drug screening. This PDA-modified tumor bioplatform will supply some promising information for studying tumor progression, overcoming tumor resistance, and screening tumor immunotherapy drugs.

N-Acetyl-L-Cysteine Reduces Cervical Carcinogenesis by Promoting Apoptosis

BACKGROUND AND OBJECTIVE

Cervical cancer is the fourth leading cause of cancer death in women, and is one of the most common malignant tumors of the reproductive system. However, more effective treatment for cervical cancer is needed. In this study, we aim to investigate whether N-acetyl-L-cysteine (NAC) could inhibit the proliferation of human papillomavirus (HPV)-positive cells, and reduce cervical carcinogenesis.

METHODS

The cervical cancer cell lines SiHa, HeLa, HPV-negative cell line C33A, and the immortalized human cervical keratinocyte cells S12 were used. The protein expression was determined using Western blot assay. mRNA expression was determined using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cell proliferation was determined by Cell Counting Kit-8 assay. Cell apoptosis was evaluated using Annexin V-FITC apoptosis kits. The numbers of colonies were measured using colony-forming assay. Xenograft tumor necrosis and HPV16 E7 expression were determined using hematoxylin and eosin (H&E) staining and immunohistochemistry.

RESULTS

Our results showed that NAC treatment at the concentration of 1.5 mM significantly promoted cell apoptosis and reduced cell growth by inhibiting HPV16 E7 expression. NAC inhibited HPV16-oncoprotein-induced hypoxia-inducible factor (HIF)-1α protein expression and Akt activation in vitro. Additionally, NAC suppressed tumor growth, as evidenced by the smaller tumor size in the xenograft mouse model and decreased HPV16 E7 expression in tumor tissues.

CONCLUSION

Our findings demonstrate that NAC exhibits the potential to promote HPV-positive cell apoptosis, and suppress the proliferation of HPV-positive cells by inhibiting cell inhibitor of apoptosis protein 2 and HIF-1α.

The vascular endothelial growth factor (VEGF) system as a key regulator of ovarian follicle angiogenesis and growth

The vascular endothelial growth factor-A (VEGFA) system is a complex set of proteins, with multiple isoforms and receptors, including both angiogenic (VEGFxxx, VEGFR2) and antiangiogenic members (VEGFxxxb, VEGFR1 and soluble forms of VEGFR). The members of the VEGF system affect the proliferation, survival, and migration of endothelial and nonendothelial cells and are involved in the regulation of follicular angiogenesis and development. The production of VEGF by secondary follicles stimulates preantral follicular development by directly affecting follicular cells and promoting the acquisition of the follicular vasculature and downstream antrum formation. Additionally, the pattern of expression of the components of the VEGF system may provide a proangiogenic milieu capable of triggering angiogenesis and stimulating follicular cells to promote antral follicle growth, whereas, during atresia, this milieu becomes antiangiogenic and blocks follicular development.

Visualization of hypoxia in cancer cells from effusions in animals and cancer patients

Objective

Tumor hypoxia is frequently observed in primary solid malignancies, but the hypoxic status of tumor cells floating in body cavity effusions is largely unknown, especially in patients. This study was to observe the hypoxia and proliferation status of cancer cells floating in effusions in mice and patients.

Methods

The distribution of hypoxia in cancer cells floating in ascites was first studied in nude mice. Hypoxia was detected by immunofluorescent visualization of pimonidazole and GLUT-1. For cancer patients, we retrospectively collected 21 ascites and 7 pleural effusion sample blocks of cancer patients, which were confirmed to contain tumor cells. Immunohistochemistry was performed to detect the expression of endogenous hypoxic markers HIF-1α and GLUT-1, proliferation index Ki-67. ¹⁸F-FDG PET/CT was performed to detect the glucose metabolism status of tumor cells in effusions.

Results

The tumor cells collected from ascites were positive for pimonidazole and GLUT-1, which suggesting that the cancer cells floating in ascites were hypoxic. Patterns of tumor hypoxia in human patients are similar to those observed in animal. HIF-1α and GLUT-1 were expressed by tumor cells in nearly all 28 cytological cases. For Ki-67 index, ascites tumor cells had a relatively low expression level compared with their corresponding primary or its metastatic lesions. Tumor cells in effusions showed high ¹⁸F-FDG uptake indicated the enhanced activity of glucose metabolism.

Conclusion

Tumor cells in body cavity effusions, as a unique subgroup of tumor, are in a state of hypoxia and low proliferation, which would be one of the driven causes of chemo-radiotherapy resistance. Novel therapeutic interventions are urgently needed to overcome tumor hypoxia.

The role of erythrocytes and erythroid progenitor cells in tumors

In the current research context of precision treatment of malignant tumors, the advantages of immunotherapy are unmatched by conventional antitumor therapy, which can prolong progression-free survival and overall survival. The search for new targets and novel combination therapies can improve the efficacy of immunotherapy and reduce adverse effects. Since current research targets for immunotherapy mainly focus on lymphocytes, little research has been done on erythrocytes. Nucleated erythroid precursor stem cells have been discovered to play an essential role in tumor progression. Researchers are exploring new targets and therapeutic approaches for immunotherapy from the perspective of erythroid progenitor cells (EPCs). Recent studies have shown that different subtypes of EPCs have specific surface markers and distinct biological roles in tumor immunity. CD45⁺ EPCs are potent myeloid-derived suppressor cell-like immunosuppressants that reduce the patient's antitumor immune response. CD45^- EPCs promote tumor invasion and metastasis by secreting artemin. A specific type of EPC also promotes angiogenesis and provides radiation protection. Therefore, EPCs may be involved in tumor growth, infiltration, and metastasis. It may also be an important cause of anti-angiogenesis and immunotherapy resistance. This review summarizes recent research advances in erythropoiesis, EPC features, and their impacts and processes on tumors.

Targeting Tumor Angiogenesis with the Selective VEGFR-3 Inhibitor EVT801 in Combination with Cancer Immunotherapy

The receptor tyrosine kinase VEGFR-3 plays a crucial role in cancer-induced angiogenesis and lymphangiogenesis, promoting tumor development and metastasis. Here, we report the novel VEGFR-3 inhibitor EVT801 that presents a more selective and less toxic profile than two major inhibitors of VEGFRs (i.e., sorafenib and pazopanib). As monotherapy, EVT801 showed a potent antitumor effect in VEGFR-3–positive tumors, and in tumors with VEGFR-3–positive microenvironments. EVT801 suppressed VEGF-C–induced human endothelial cell proliferation in vitro and tumor (lymph)angiogenesis in different tumor mouse models. In addition to reduced tumor growth, EVT801 decreased tumor hypoxia, favored sustained tumor blood vessel homogenization (i.e., leaving fewer and overall larger vessels), and reduced important immunosuppressive cytokines (CCL4, CCL5) and myeloid-derived suppressor cells (MDSC) in circulation. Furthermore, in carcinoma mouse models, the combination of EVT801 with immune checkpoint therapy (ICT) yielded superior outcomes to either single treatment. Moreover, tumor growth inhibition was inversely correlated with levels of CCL4, CCL5, and MDSCs after treatment with EVT801, either alone or combined with ICT. Taken together, EVT801 represents a promising anti(lymph)angiogenic drug for improving ICT response rates in patients with VEGFR-3 positive tumors.

Significance:

The VEGFR-3 inhibitor EVT801 demonstrates superior selectivity and toxicity profile than other VEGFR-3 tyrosine kinase inhibitors. EVT801 showed potent antitumor effects in VEGFR-3–positive tumors, and tumors with VEGFR-3–positive microenvironments through blood vessel homogenization, and reduction of tumor hypoxia and limited immunosuppression. EVT801 increases immune checkpoint inhibitors’ antitumor effects.

Current Landscape of Therapeutic Resistance in Lung Cancer and Promising Strategies to Overcome Resistance

Lung cancer is one of the leading causes of cancer-related deaths worldwide with a 5-year survival rate of less than 18%. Current treatment modalities include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy. Despite advances in therapeutic options, resistance to therapy remains a major obstacle to the effectiveness of long-term treatment, eventually leading to therapeutic insensitivity, poor progression-free survival, and disease relapse. Resistance mechanisms stem from genetic mutations and/or epigenetic changes, unregulated drug efflux, tumor hypoxia, alterations in the tumor microenvironment, and several other cellular and molecular alterations. A better understanding of these mechanisms is crucial for targeting factors involved in therapeutic resistance, establishing novel antitumor targets, and developing therapeutic strategies to resensitize cancer cells towards treatment. In this review, we summarize diverse mechanisms driving resistance to chemotherapy, radiotherapy, targeted therapy, and immunotherapy, and promising strategies to help overcome this therapeutic resistance.

Secretome analysis reveals reduced expression of COL4A2 in hypoxic cancer-associated fibroblasts with a tumor-promoting function in gastric cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs) are major components of the tumor microenvironment (TME). Hypoxic TME is known to promote tumor progression. However, how a hypoxic condition regulates CAFs remains elusive.

METHODS

To investigate the underlying mechanism involved in the regulation of gastric cancer (GC) progression by hypoxic CAFs, we performed secretome profiling. Normoxic or hypoxic CAFs conditioned media (CM) were filter-concentrated and in-gel trypsin digested. Resulting peptides were analyzed with LC-MS/MS.

RESULTS

We observed that CM derived from hypoxic CAFs could promote migration of a panel of GC cell lines (AGS, SNU668, SNU638). Mass spectrometry analysis of hypoxic or normoxic CAFs CM identified 1595 proteins, of which 19 proteins (10 upregulated and 9 downregulated) were differentially expressed in the hypoxic secretome. We focused on COL4A2, whose expression was significantly decreased in hypoxic CAFs in HIF-1α-independent manner. Silencing of COL4A2 expression in normoxic CAFs phenocopied the effect of hypoxic CAFs in promoting GC cell migration.

CONCLUSIONS

The reduced expression of COL4A2 in a hypoxic environment might be associated with the tumor-promoting role of hypoxic CAFs in GC.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Manganese Dioxide-Based Nanocarrier Delivers Paclitaxel to Enhance Chemotherapy against Orthotopic Glioma through Hypoxia Relief

Chemotherapy plays an important role in treating cancers in clinic. Hypoxia-mediated chemoresistance remains a major hurdle for effective tumor chemotherapy. Herein, a new class of tLyP-1-modified dopamine (DOPA)-β-cyclodextrin (CD)-coated paclitaxel (PTX)- and manganese dioxide (MnO₂ )-loaded nanoparticles (tLyP-1-CD-DOPA-MnO₂ @PTX) is developed to enhance glioma chemotherapy. The nanomedicine delivered to the tumor site decomposes in response to the weak acidity and high hydrogen peroxide in the tumor microenvironment (TME), resulting in collapse of the system to release PTX and generates Mn²⁺ and O₂ . In a rat model of intracranial glioma, tLyP-1-CD-DOPA-MnO₂ @PTX can efficiently pass through the blood-brain-barrier to accumulate in tumor sites. The hypoxia in TME can be relieved via O₂ generated by MnO₂ and the reactive oxygen species produced by Mn²⁺ can kill tumor cells. The tLyP-1-CD-DOPA-MnO₂ @PTX nanoparticles exert a remarkable antitumor effect by promoting apoptosis and inhibiting proliferation of tumor cells in addition to enabling real-time tumor monitoring with magnetic resonance imaging. This MnO₂ -based theranostic medicine will offer a novel strategy to simultaneously enhance chemotherapy and achieve real-time imaging of therapeutic process in glioma treatment.

YY1 Is a Key Player in Melanoma Immunotherapy/Targeted Treatment Resistance

Malignant melanoma, with its increasing incidence and high potential to form metastases, is one of the most aggressive types of skin malignancies responsible for a significant number of deaths worldwide. However, melanoma also demonstrates a high potential for induction of a specific adaptive anti-tumor immune response being one of the most immunogenic malignancies. Yin Yang 1 (YY1) transcription factor is essential to numerous cellular processes and the regulation of transcriptional and posttranslational modifications of various genes. It regulates programmed cell death 1 (PD1) and lymphocyte-activation gene 3 (LAG3) by binding to its promoters, as well as suppresses both Fas and TRAIL by negatively regulating DR5 transcription and expression and interaction with the silencer region of the Fas promoter, rendering cells resistant to apoptosis. Moreover, YY1 is considered a master regulator in various stages of embryogenesis, especially in neural crest stem cells (NCSCs) survival and proliferation as it acts as transcriptional repressor on cancer stem cells-related transcription factors. In addition, YY1 increases the metastatic potential of melanoma through negative regulation of microRNA-9 (miR-9) expression, acts as a cofactor of transcription factor EB (TFEB) and contributes to autophagy regulation, mainly due to increased transcription of genes related to autophagy and lysosome biogenesis. Therefore, focusing on the detailed biology and administration of therapies that directly target YY1 or crosstalk pathways in malignant melanoma could facilitate the development of new and more effective treatment strategies and improve patients’ outcomes.

Significance of Specific Oxidoreductases in the Design of Hypoxia-Activated Prodrugs and Fluorescent Turn Off–On Probes for Hypoxia Imaging

Simple Summary

Hypoxia-activated prodrugs (HAPs), selectively reduced by specific oxidoreductases under hypoxic conditions, form cytotoxic agents damaging the local cancer cells. On the basis of the reported clinical data concerning several HAPs, one can draw conclusions regarding their preclinical attractiveness and, regrettably, the low efficacy of Phase III clinical trials. Clinical failure may be explained, inter alia, by the lack of screening of patients on the basis of tumor hypoxia and low availability of specific oxidoreductases involved in HAP activation. There is surprisingly little information on the quantification of these enzymes in cells or tissues, compared to the advanced research associated with the use of HAPs. Our knowledge about the expression and activity of these enzymes in various cancer cell lines under hypoxic conditions is inadequate. Only in a few cases were researchers able to demonstrate the differences in the expression or activity of selected oxidoreductases, depending on the oxygen concentration. Additionally, it was cell line dependent. More systematic studies are required. The optical probes, based on turning on the fluorescence emission upon irreversible reduction catalyzed by the overexpressed oxidoreductases, can be helpful in this type of research. Ultimately, such sensors can estimate both the oxidoreductase activity and the degree of oxygenation in one step. To achieve this goal, their response must be correlated with the expression or activity of enzymes potentially involved in turning on their emissions, as determined by biochemical methods. In conclusion, the incorporation of biomarkers to identify hypoxia is a prerequisite for successful HAP therapies. However, it is equally important to assess the level of specific oxidoreductases required for their activation.

Abstract

Hypoxia is one of the hallmarks of the tumor microenvironment and can be used in the design of targeted therapies. Cellular adaptation to hypoxic stress is regulated by hypoxia-inducible factor 1 (HIF-1). Hypoxia is responsible for the modification of cellular metabolism that can result in the development of more aggressive tumor phenotypes. Reduced oxygen concentration in hypoxic tumor cells leads to an increase in oxidoreductase activity that, in turn, leads to the activation of hypoxia-activated prodrugs (HAPs). The same conditions can convert a non-fluorescent compound into a fluorescent one (fluorescent turn off–on probes), and such probes can be designed to specifically image hypoxic cancer cells. This review focuses on the current knowledge about the expression and activity of oxidoreductases, which are relevant in the activation of HAPs and fluorescent imaging probes. The current clinical status of HAPs, their limitations, and ways to improve their efficacy are briefly discussed. The fluorescence probes triggered by reduction with specific oxidoreductase are briefly presented, with particular emphasis placed on those for which the correlation between the signal and enzyme expression determined with biochemical methods is achievable.

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

Background

The 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.

Methods

CRC 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.

Results

Our 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.

Conclusion

Our 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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09666-2.

Renal hypoxia-HIF-PHD-EPO signaling in transition metal nephrotoxicity: friend or foe?

The kidney is the main organ that senses changes in systemic oxygen tension, but it is also the key detoxification, transit and excretion site of transition metals (TMs). Pivotal to oxygen sensing are prolyl-hydroxylases (PHDs), which hydroxylate specific residues in hypoxia-inducible factors (HIFs), key transcription factors that orchestrate responses to hypoxia, such as induction of erythropoietin (EPO). The essential TM ion Fe is a key component and regulator of the hypoxia–PHD–HIF–EPO (HPHE) signaling axis, which governs erythropoiesis, angiogenesis, anaerobic metabolism, adaptation, survival and proliferation, and hence cell and body homeostasis. However, inadequate concentrations of essential TMs or entry of non-essential TMs in organisms cause toxicity and disrupt health. Non-essential TMs are toxic because they enter cells and displace essential TMs by ionic and molecular mimicry, e. g. in metalloproteins. Here, we review the molecular mechanisms of HPHE interactions with TMs (Fe, Co, Ni, Cd, Cr, and Pt) as well as their implications in renal physiology, pathophysiology and toxicology. Some TMs, such as Fe and Co, may activate renal HPHE signaling, which may be beneficial under some circumstances, for example, by mitigating renal injuries from other causes, but may also promote pathologies, such as renal cancer development and metastasis. Yet some other TMs appear to disrupt renal HPHE signaling, contributing to the complex picture of TM (nephro-)toxicity. Strikingly, despite a wealth of literature on the topic, current knowledge lacks a deeper molecular understanding of TM interaction with HPHE signaling, in particular in the kidney. This precludes rationale preventive and therapeutic approaches to TM nephrotoxicity, although recently activators of HPHE signaling have become available for therapy.

p53 Signaling on Microenvironment and Its Contribution to Tissue Chemoresistance

Chemoresistance persists as a significant, unresolved clinical challenge in many cancer types. The tumor microenvironment, in which cancer cells reside and interact with non-cancer cells and tissue structures, has a known role in promoting every aspect of tumor progression, including chemoresistance. However, the molecular determinants of microenvironment-driven chemoresistance are mainly unknown. In this review, we propose that the TP53 tumor suppressor, found mutant in over half of human cancers, is a crucial regulator of cancer cell-microenvironment crosstalk and a prime candidate for the investigation of microenvironment-specific modulators of chemoresistance. Wild-type p53 controls the secretion of factors that inhibit the tumor microenvironment, whereas altered secretion or mutant p53 interfere with p53 function to promote chemoresistance. We highlight resistance mechanisms promoted by mutant p53 and enforced by the microenvironment, such as extracellular matrix remodeling and adaptation to hypoxia. Alterations of wild-type p53 extracellular function may create a cascade of spatial amplification loops in the tumor tissue that can influence cellular behavior far from the initial oncogenic mutation. We discuss the concept of chemoresistance as a multicellular/tissue-level process rather than intrinsically cellular. Targeting p53-dependent crosstalk mechanisms between cancer cells and components of the tumor environment might disrupt the waves of chemoresistance that spread across the tumor tissue, increasing the efficacy of chemotherapeutic agents.

The Clinical Outcomes, Prognostic Factors and Nomogram Models for Primary Lung Cancer Patients Treated With Stereotactic Body Radiation Therapy

PURPOSE

Stereotactic body radiation therapy (SBRT) is a standard treatment for early primary lung cancer patients. However, there are few simple models for predicting the clinical outcomes of these patients. Our study analyzed the clinical outcomes, identified the prognostic factors, and developed prediction nomogram models for these patients.

MATERIALS AND METHODS

We retrospectively analyzed 114 patients with primary lung cancer treated with SBRT from 2012 to 2020 at our institutions and assessed patient's clinical outcomes and levels of toxicity. Kaplan-Meier analysis with a log-rank test was used to generate the survival curve. The cut-off values of continuous factors were calculated with the X-tile tool. Potential independent prognostic factors for clinical outcomes were explored using cox regression analysis. Nomograms for clinical outcomes prediction were established with identified factors and assessed by calibration curves.

RESULTS

The median overall survival (OS) was 40.6 months, with 3-year OS, local recurrence free survival (LRFS), distant disease-free survival (DDFS) and progression free survival (PFS) of 56.3%, 61.3%, 72.9% and 35.8%, respectively, with grade 3 or higher toxicity rate of 7%. The cox regression analysis revealed that the clinical stage, immobilization device, and the prescription dose covering 95% of the target area (D95) were independent prognostic factors associated with OS. Moreover, the clinical stage, and immobilization device were independent prognostic factors of LRFS and PFS. The smoking status, hemoglobin (Hb) and immobilization device were significant prognostic factors for DDFS. The nomograms and calibration curves incorporating the above factors indicated good predictive accuracy.

CONCLUSIONS

SBRT is effective and safe for primary lung cancer. The prognostic factors associated with OS, LRFS, DDFS and PFS are proposed, and the nomograms we proposed are suitable for clinical outcomes prediction.

Identifying a Hypoxia-Related Long Non-Coding RNAs Signature to Improve the Prediction of Prognosis and Immunotherapy Response in Hepatocellular Carcinoma

Abstract Background: Both hypoxia and long non-coding RNAs (lncRNAs) contribute to the tumor progression in hepatocellular carcinoma (HCC). We sought to establish a hypoxia-related lncRNA signature and explore its correlation with immunotherapy response in HCC.

Materials and Methods: Hypoxia-related differentially expressed lncRNAs (HRDELs) were identified by conducting the differential gene expression analyses in GSE155505 and The Cancer Genome Atlas (TCGA)- liver hepatocellular carcinoma (LIHC) datasets. The HRDELs landscape in patients with HCC in TCGA-LIHC was dissected by an unsupervised clustering method. Patients in the TCGA-LIHC cohort were stochastically split into the training and testing dataset. The prognostic signature was developed using LASSO (least absolute shrinkage and selection operator) penalty Cox and multivariable Cox analyses. The tumor immune microenvironment was delineated by the single-sample gene set enrichment analysis (ssGSEA) algorithm. The Tumor Immune Dysfunction and Exclusion (TIDE) algorithm was applied to evaluate the predictive value of the constructed signature in immunotherapeutic responsiveness.

Results: A total of 55 HRDELs were identified through integrated bioinformatical analyses in GSE155505 and TCGA-LIHC. Patients in the TCGA-LIHC cohort were categorized into three HRDELs-specific clusters associated with different clinical outcomes. The prognostic signature involving five hypoxia-related lncRNAs (LINC00869, CAHM, RHPN1-AS1, MKLN1-AS, and DUXAP8) was constructed in the training dataset and then validated in the testing dataset and entire TCGA-LIHC cohort. The 5-years AUC of the constructed signature for prognostic prediction reaches 0.705 and is superior to that of age, AJCC stage, and histopathological grade. Patients with high-risk scores consistently had poorer overall survival outcomes than those with low-risk scores irrespective of other clinical parameters status. The low-risk group had more abundance in activated CD8⁺ T cell and activated B cell and were predicted to be more responsive to immunotherapy and targeted therapy than the high-risk group.

Conclusion: We established a reliable hypoxia-related lncRNAs signature that could accurately predict the clinical outcomes of HCC patients and correlate with immunotherapy response and targeted drug sensitivity, providing new insights for immunotherapy and targeted therapy in HCC.

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.

Targeting Hypoxia: Hypoxia-Activated Prodrugs in Cancer Therapy

Hypoxia is an important characteristic of most solid malignancies, and is closely related to tumor prognosis and therapeutic resistance. Hypoxia is one of the most important factors associated with resistance to conventional radiotherapy and chemotherapy. Therapies targeting tumor hypoxia have attracted considerable attention. Hypoxia-activated prodrugs (HAPs) are bioreductive drugs that are selectively activated under hypoxic conditions and that can accurately target the hypoxic regions of solid tumors. Both single-agent and combined use with other drugs have shown promising antitumor effects. In this review, we discuss the mechanism of action and the current preclinical and clinical progress of several of the most widely used HAPs, summarize their existing problems and shortcomings, and discuss future research prospects.

Links between the unfolded protein response and the DNA damage response in hypoxia: a systematic review

Hypoxia is a feature of most solid tumours and predicts for poor prognosis. In radiobiological hypoxia (<0.1% O₂) cells become up to three times more resistant to radiation. The biological response to radiobiological hypoxia is one of few physiologically relevant stresses that activates both the unfolded protein and DNA damage responses (UPR and DDR). Links between these pathways have been identified in studies carried out in normoxia. Based in part on these previous studies and recent work from our laboratory, we hypothesised that the biological response to hypoxia likely includes overlap between the DDR and UPR. While inhibition of the DDR is a recognised strategy for improving radiation response, the possibility of achieving this through targeting the UPR has not been realised. We carried out a systematic review to identify links between the DDR and UPR, in human cell lines exposed to <2% O₂. Following PRISMA guidance, literature from January 2010 to October 2020 were retrieved via Ovid MEDLINE and evaluated. A total of 202 studies were included. LAMP3, ULK1, TRIB3, CHOP, NOXA, NORAD, SIAH1/2, DYRK2, HIPK2, CREB, NUPR1, JMJD2B, NRF2, GSK-3B, GADD45a, GADD45b, STAU1, C-SRC, HK2, CAV1, CypB, CLU, IGFBP-3 and SP1 were highlighted as potential links between the hypoxic DDR and UPR. Overall, we identified very few studies which demonstrate a molecular link between the DDR and UPR in hypoxia, however, it is clear that many of the molecules highlighted warrant further investigation under radiobiological hypoxia as these may include novel therapeutic targets to improve radiotherapy response.

Role of Alpha-Fetoprotein in Hepatocellular Carcinoma Drug Resistance

Hepatocellular carcinoma (HCC) is a major type of primary liver cancer and a major cause of cancer-related deaths worldwide because of its high recurrence rate and poor prognosis. Surgical resection is currently the major treatment measure for patients in the early and middle stages of the disease. Because due to late diagnosis, most patients already miss the opportunity for surgery upon disease confirmation, conservative chemotherapy (drug treatment) remains an important method of comprehensive treatment for patients with middle- and late-stage liver cancer. However, multidrug resistance (MDR) in patients with HCC severely reduces the treatment effect and is an important obstacle to chemotherapeutic success. Alpha-fetoprotein (AFP) is an important biomarker for the diagnosis of HCC. The serum expression levels of AFP in many patients with HCC are increased, and a persistently increased AFP level is a risk factor for HCC progression. Many studies have indicated that AFP functions as an immune suppressor, and AFP can promote malignant transformation during HCC development and might be involved in the process of MDR in patients with liver cancer. This review describes drug resistance mechanisms during HCC drug treatment and reviews the relationship between the mechanism of AFP in HCC development and progression and HCC drug resistance.

Therapeutic strategies to overcome taxane resistance in cancer

One of the primary causes of attenuated or loss of efficacy of cancer chemotherapy is the emergence of multidrug resistance (MDR). Numerous studies have been published regarding potential approaches to reverse resistance to taxanes, including paclitaxel (PTX) and docetaxel, which represent one of the most important classes of anticancer drugs. Since 1984, following the FDA approval of paclitaxel for the treatment of advanced ovarian carcinoma, taxanes have been extensively used as drugs that target tumor microtubules. Taxanes, have been shown to affect an array of oncogenic signaling pathways and have potent cytotoxic efficacy. However, the clinical success of these drugs has been restricted by the emergence of cancer cell resistance, primarily caused by the overexpression of MDR efflux transporters or by microtubule alterations. In vitro and in vivo studies indicate that the mechanisms underlying the resistance to PTX and docetaxel are primarily due to alterations in α-tubulin and β-tubulin. Moreover, resistance to PTX and docetaxel results from: 1) alterations in microtubule-protein interactions, including microtubule-associated protein 4, stathmin, centriole, cilia, spindle-associated protein, and kinesins; 2) alterations in the expression and activity of multidrug efflux transporters of the ABC superfamily including P-glycoprotein (P-gp/ABCB1); 3) overexpression of anti-apoptotic proteins or inhibition of apoptotic proteins and tumor-suppressor proteins, as well as 4) modulation of signal transduction pathways associated with the activity of several cytokines, chemokines and transcription factors. In this review, we discuss the abovementioned molecular mechanisms and their role in mediating cancer chemoresistance to PTX and docetaxel. We provide a detailed analysis of both in vitro and in vivo experimental data and describe the application of these findings to therapeutic practice. The current review also discusses the efficacy of different pharmacological modulations to achieve reversal of PTX resistance. The therapeutic roles of several novel compounds, as well as herbal formulations, are also discussed. Among them, many structural derivatives had efficacy against the MDR phenotype by either suppressing MDR or increasing the cytotoxic efficacy compared to the parental drugs, or both. Natural products functioning as MDR chemosensitizers offer novel treatment strategies in patients with chemoresistant cancers by attenuating MDR and increasing chemotherapy efficacy. We broadly discuss the roles of inhibitors of P-gp and other efflux pumps, in the reversal of PTX and docetaxel resistance in cancer cells and the significance of using a nanomedicine delivery system in this context. Thus, a better understanding of the molecular mechanisms mediating the reversal of drug resistance, combined with drug efficacy and the application of target-based inhibition or specific drug delivery, could signal a new era in modern medicine that would limit the pathological consequences of MDR in cancer patients.

Hypoxia up-regulates VEGF ligand and downregulates VEGF soluble receptor mRNA expression in bovine granulosa cells in vitro

Oxygen concentration (0₂) in antral ovarian follicles is below that found in most tissues, which is important for adequate granulosa cell function. The VEGF system is linked to angiogenesis and responds to changing 0₂ by stimulating neovascularization when levels are low. However, in the avascular granulosa cell layer of the follicle, VEGF action is directed to stimulating cell viability and steroidogenesis. The aim of this study was to examine the effect of 0₂ concentration on granulosa cell expression of the VEGF-system components. Bovine granulosa cells were isolated from medium-sized follicles (4-7 mm in diameter), placed in McCoy 5a medium supplemented with 10 ng/mL of insulin, 1 ng/mL of IGF-I, and 1 ng/mL of FSH, and cultured in four well plates (500 thousand cells per well), on three separate occasions. Culture plates were placed in gas-impermeable jars with a gas mixture containing either 2%, or 5% of O₂, or under atmospheric air condition inside an incubator (20% of 0₂). Media was replaced at 48 h of culture and cells from the plate in each oxygen concentration were pooled for RNA extraction after 96 h. The number of mRNA copies for the VEGF-system components - including ligands (VEGF120, VEGF120b, VEGF165 and VEGF165b), enzymes (cyclin-dependent like kinases-1, CLK1 and serine-arginine protein kinase 1, SRPK1), splicing factors (serine-arginine-rich splicing factors, SRSF1 and SRSF6), and the membrane-bound (VEGFR1, VEGFR2) and soluble forms of the receptors (sVEGFR1 and sVEGFR2) were quantified by qPCR. Granulosa cells cultured with low 0₂ (2%) had a higher expression of VEGF ligands (P < 0.05) when compared to cells cultured at 20% 0₂. VEGF164b mRNA was absent in granulosa cells from all culture conditions. The 2 and 5% 0₂ levels, which coincide with physiological concentrations, in the ovarian follicle, induced higher SRSF6 expression than atmospheric 0₂ concentrations (20%, P < 0.05). In contrast, mRNA copies for SRPK1, CLK1, SRSF1, VEGFR1 or VEGFR2 did not differ between 0₂ culture conditions. (P > 0.05). Nonetheless, mRNA copies for the soluble receptors, sVEGFR1 and sVEGFR2, linearly increased (P < 0.05) with 0₂ concentration. These results suggest that when cultured under hypoxic conditions, granulosa cells may develop an autocrine milieu that favors VEGF's biological effects on their survival and function.

The Chemosensitizing Role of Metformin in Anti-Cancer Therapy

Chemoresistance, which leads to the failure of chemotherapy and further tumor recurrence, presents the largest hurdle for the success of anti-cancer therapy. In recent years, metformin, a widely used first-line antidiabetic drug, has attracted increasing attention for its anti-cancer effects. A growing body of evidence indicates that metformin can sensitize tumor responses to different chemotherapeutic drugs, such as hormone modulating drugs, anti-metabolite drugs, antibiotics, and DNA-damaging drugs via selective targeting of Cancer Stem Cells (CSCs), improving the hypoxic microenvironment, and by suppressing tumor metastasis and inflammation. In addition, metformin may regulate metabolic programming, induce apoptosis, reverse Epithelial to Mesenchymal Transition (EMT), and Multidrug Resistance (MDR). In this review, we summarize the chemosensitization effects of metformin and focus primarily on its molecular mechanisms in enhancing the sensitivity of multiple chemotherapeutic drugs, through targeting of mTOR, ERK/P70S6K, NF-κB/HIF-1 α, and Mitogen- Activated Protein Kinase (MAPK) signaling pathways, as well as by down-regulating the expression of CSC genes and Pyruvate Kinase isoenzyme M2 (PKM2). Through a comprehensive understanding of the molecular mechanisms of chemosensitization provided in this review, the rationale for the use of metformin in clinical combination medications can be more systematically and thoroughly explored for wider adoption against numerous cancer types.>.

Recent Research on Methods to Improve Tumor Hypoxia Environment

Cancer is a major disease burden worldwide. In recent years, in addition to surgical resection, radiotherapy and chemotherapy are recognized as the most effective methods for treating solid tumors. These methods have been introduced to treat tumors of different origins and stages clinically. However, due to insufficient blood flow and oxygen (O2) supply in solid tumors, hypoxia is caused, leading to decreased sensitivity of tumor cells and poor therapeutic effects. In addition, hypoxia will also lead to resistance to most anticancer drugs, accelerate malignant progress, and increase metastasis. In solid tumors, adequate O2 supply and adequate delivery of anticancer drugs are essential to improve radiotherapy and chemotherapy sensitivity. In recent decades, the researches on relieving tumor hypoxia have attracted researchers' extensive attention and achieved good results. However, as far as we know, there is no detailed review of the researches on alleviating tumor hypoxia. Therefore, in this contribution, we hope to give an overview of the researches on methods to improve tumor hypoxia environment and summarize their effect and application in tumor therapy, to provide a methodological reference for the research and development of new antitumor agents.

Hypoxia-Inducible Factor α Subunits Regulate Tie2-Expressing Macrophages That Influence Tumor Oxygen and Perfusion in Murine Breast Cancer

Tie2-expressing monocytes/macrophages (TEMs) are a distinct subset of proangiogenic monocytes selectively recruited to tumors in breast cancer. Because of the hypoxic nature of solid tumors, we investigated if oxygen, via hypoxia-inducible transcription factors HIF-1α and HIF-2α, regulates TEM function in the hypoxic tumor microenvironment. We orthotopically implanted PyMT breast tumor cells into the mammary fat pads of syngeneic LysMcre, HIF-1α fl/fl /LysMcre, or HIF-2α fl/fl /LysMcre mice and evaluated the tumor TEM population. There was no difference in the percentage of tumor macrophages among the mouse groups. In contrast, HIF-1α fl/fl /LysMcre mice had a significantly smaller percentage of tumor TEMs compared with control and HIF-2α fl/fl /LysMcre mice. Proangiogenic TEMs in macrophage HIF-2α-deficient tumors presented significantly more CD31+ microvessel density but exacerbated hypoxia and tissue necrosis. Reduced numbers of proangiogenic TEMs in macrophage HIF-1α-deficient tumors presented significantly less microvessel density but tumor vessels that were more functional as lectin injection revealed more perfusion, and functional electron paramagnetic resonance analysis revealed more oxygen in those tumors. Macrophage HIF-1α-deficient tumors also responded significantly to chemotherapy. These data introduce a previously undescribed and counterintuitive prohypoxia role for proangiogenic TEMs in breast cancer which is, in part, suppressed by HIF-2α.

Computed tomography and photoacoustic imaging guided photodynamic therapy against breast cancer based on mesoporous platinum with insitu oxygen generation ability

Photodynamic therapy (PDT) has been widely used in cancer treatment. However, hypoxia in most solid tumors seriously restricts the efficacy of PDT. To improve the hypoxic microenvironment, we designed a novel mesoporous platinum (mPt) nanoplatform to catalyze hydrogen peroxide (H₂O₂) within the tumor cells in situ without an extra enzyme. During the fabrication, the carboxy terminus of the photosensitizer chlorin e6 (Ce6) was connected to the amino terminus of the bifunctional mercaptoaminopolyglycol (SH-PEG-NH₂) by a condensation reaction, and then PEG-Ce6 was modified onto the mPt moiety via the mercapto terminal of SH-PEG-NH₂. Material, cellular and animal experiments demonstrated that Pt@PEG-Ce6 catalyzed H₂O₂ to produce oxygen (O₂) and that Ce6 transformed O₂ to generate reactive oxygen species (ROS) upon laser irradiation. The Pt@PEG-Ce6 nanoplatform with uniform diameter presented good biocompatibility and efficient tumor accumulation. Due to the high atomic number and good near-infrared absorption for Pt, this Pt@PEG-Ce6 nanoplatform showed computed tomography (CT) and photoacoustic (PA) dual-mode imaging ability, thus providing an important tool for monitoring the tumor hypoxic microenvironment. Moreover, the Pt@PEG-Ce6 nanoplatform reduced the expression of hypoxia-inducible factor-1α (HIF-1α) and programmed death-1 (PD-1) in tumors, discussing the relationship between hypoxia, PD-1, and PDT for the first time.

Identification of Potential Chemical Substrates as Fuel for Hypoxic Tumors That May Be Linked to Invadopodium Formation in Hypoxia-Induced MDA-MB-231 Breast-Cancer Cell Line

Hypoxia plays a significant role in solid tumors by the increased expression of hypoxia-inducible factor-1α (HIF-1α), which is known to promote cancer invasion and metastasis. Cancer-cell invasion dynamically begins with the degradation of the extracellular matrix (ECM) via invadopodia formation. The chemical substrates that are utilized by hypoxic cells as fuel to drive invadopodia formation are still not fully understood. Therefore, the aim of the study was to maintain MDA-MB-231 cells under hypoxia conditions to allow cells to form a large number of invadopodia as a model, followed by identifying their nutrient utilization. The results of the study revealed an increase in the number of cells forming invadopodia under hypoxia conditions. Moreover, Western blot analysis confirmed that essential proteins for hypoxia and invadopodia, including HIF-1α, vascular endothelial growth factor (VEGF), metallopeptidase-2 (MMP-2), and Rho guanine nucleotide exchange factor 7 (β-PIX), significantly increased under hypoxia. Interestingly, phenotype microarray showed that only 11 chemical substrates from 367 types of substrates were significantly metabolized in hypoxia compared to in normoxia. This is thought to be fuel for hypoxia to drive the invasion process. In conclusion, we found 11 chemical substrates that could have potential energy sources for hypoxia-induced invadopodia formation of these cells. This may in part be a target in the hypoxic tumor and invadopodia formation. Additionally, these findings can be used as potential carrier targets in cancer-drug discovery, such as the usage of dextrin.

Lipid Signaling in Ocular Neovascularization

Vasculogenesis and angiogenesis play a crucial role in embryonic development. Pathological neovascularization in ocular tissues can lead to vision-threatening vascular diseases, including proliferative diabetic retinopathy, retinal vein occlusion, retinopathy of prematurity, choroidal neovascularization, and corneal neovascularization. Neovascularization involves various cellular processes and signaling pathways and is regulated by angiogenic factors such as vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF). Modulating these circuits may represent a promising strategy to treat ocular neovascular diseases. Lipid mediators derived from membrane lipids are abundantly present in most tissues and exert a wide range of biological functions by regulating various signaling pathways. In particular, glycerophospholipids, sphingolipids, and polyunsaturated fatty acids exert potent pro-angiogenic or anti-angiogenic effects, according to the findings of numerous preclinical and clinical studies. In this review, we summarize the current knowledge regarding the regulation of ocular neovascularization by lipid mediators and their metabolites. A better understanding of the effects of lipid signaling in neovascularization may provide novel therapeutic strategies to treat ocular neovascular diseases and other human disorders.

Tumor microenvironment and epithelial mesenchymal transition as targets to overcome tumor multidrug resistance

It is well established that multifactorial drug resistance hinders successful cancer treatment. Tumor cell interactions with the tumor microenvironment (TME) are crucial in epithelial-mesenchymal transition (EMT) and multidrug resistance (MDR). TME-induced factors secreted by cancer cells and cancer-associated fibroblasts (CAFs) create an inflammatory microenvironment by recruiting immune cells. CD11b+/Gr-1+ myeloid-derived suppressor cells (MDSCs) and inflammatory tumor associated macrophages (TAMs) are main immune cell types which further enhance chronic inflammation. Chronic inflammation nurtures tumor-initiating/cancer stem-like cells (CSCs), induces both EMT and MDR leading to tumor relapses. Pro-thrombotic microenvironment created by inflammatory cytokines and chemokines from TAMs, MDSCs and CAFs is also involved in EMT and MDR. MDSCs are the most common mediators of immunosuppression and are also involved in resistance to targeted therapies, e.g. BRAF inhibitors and oncolytic viruses-based therapies. Expansion of both cancer and stroma cells causes hypoxia by hypoxia-inducible transcription factors (e.g. HIF-1α) resulting in drug resistance. TME factors induce the expression of transcriptional EMT factors, MDR and metabolic adaptation of cancer cells. Promoters of several ATP-binding cassette (ABC) transporter genes contain binding sites for canonical EMT transcription factors, e.g. ZEB, TWIST and SNAIL. Changes in glycolysis, oxidative phosphorylation and autophagy during EMT also promote MDR. Conclusively, EMT signaling simultaneously increases MDR. Owing to the multifactorial nature of MDR, targeting one mechanism seems to be non-sufficient to overcome resistance. Targeting inflammatory processes by immune modulatory compounds such as mTOR inhibitors, demethylating agents, low-dosed histone deacetylase inhibitors may decrease MDR. Targeting EMT and metabolic adaptation by small molecular inhibitors might also reverse MDR. In this review, we summarize evidence for TME components as causative factors of EMT and anticancer drug resistance.

Increased expression of YTHDF1 and HNRNPA2B1 as potent biomarkers for melanoma: a systematic analysis

Background

The incidence and mortality of melanoma is increasing around the world. To deeply explain the mechanism insight into it, we conducted a systematic analysis to examine the levels of regulatory genes of the common RNA epigenetic modification-N6-methyladenosine (m⁶A) in patients with melanoma compared by the healthy.

Methods

We analyzed the expression of m⁶A Eraser, Writer, and Reader genes based on publicly available datasets on Oncomine and validated the results with a gene expression omnibus dataset. Hub genes were identified with Cytohubba and the frequency of copy number alterations was analyzed with the cBioPortal tool.

Results

The results revealed the up-regulation of YTHDF1 and HNRNPA2B1 in melanoma. Combining the two genes improved the efficacy in diagnosing melanoma by about 10% compared to each gene alone. Hub genes identified with four analysis methods were compared and the overlapping genes were selected. These genes were enriched in several gene ontology terms. Genes related to p53-signaling consisted of CDK2, CDK1, RRM2, CCNB1, and CHEK1. All five genes were positively correlated with either YTHDF1 or HNRNPA2B1, suggesting that both genes may affect m⁶A modification by the five genes, further up-regulating their expression and facilitate their roles in inhibiting p53 to suppress tumorigenesis. We also observed major mutations in YTHDF1 and HNRNPA2B1 that led to their amplification in melanoma. Significant differences were observed in the clinical characteristics of patients with altered and unaltered m⁶A regulatory genes such as tumor stage and treatment response.

Conclusions

We, for the first time, identified a combination of m⁶A regulatory genes to diagnose melanoma. We also analyzed m⁶A-related genes more comprehensively based on systematic complete data. We found that YTHDF1 and HNRNPA2B1 were altered in melanoma and might influence the development of the disease through signaling pathways such as p53.

Hypoxia-induced GBE1 expression promotes tumor progression through metabolic reprogramming in lung adenocarcinoma

Hypoxia mediates a metabolic switch from oxidative phosphorylation to glycolysis and increases glycogen synthesis. We previously found that glycogen branching enzyme (GBE1) is downstream of the hypoxia-inducible factor-1 (HIF1) signaling pathway in lung adenocarcinoma (LUAD) cells; however, the molecular mechanism underlying HIF1 regulation of GBE1 expression remains unknown. Herein, the effect of GBE1 on tumor progression via changes in metabolic signaling under hypoxia in vitro and in vivo was evaluated, and GBE1-related genes from human specimens and data sets were analyzed. Hypoxia induced GBE1 upregulation in LUAD cells. GBE1-knockdown A549 cells showed impaired cell proliferation, clone formation, cell migration and invasion, angiogenesis, tumor growth, and metastasis. GBE1 mediated the metabolic reprogramming of LUAD cells. The expression of gluconeogenesis pathway molecules, especially fructose-1,6-bisphosphatase (FBP1), was markedly higher in shGBE1 A549 cells than it was in the control cells. FBP1 inhibited the tumor progression of LUAD. GBE1-mediated FBP1 suppression via promoter methylation enhanced HIF1α levels through NF-κB signaling. GBE1 may be a negative prognostic biomarker for LUAD patients. Altogether, hypoxia-induced HIF1α mediated GBE1 upregulation, suppressing FBP1 expression by promoter methylation via NF-κB signaling in LUAD cells. FBP1 blockade upregulated HIF1α, triggered the switch to anaerobic glycolysis, and enhanced glucose uptake. Therefore, targeting HIF1α/GBE1/NF-κB/FBP1 signaling may be a potential therapeutic strategy for LUAD.

Role of hyperoxic treatment in cancer

IMPACT STATEMENT

Tumor hypoxia promotes cancer cell aggressiveness, and is strongly associated with poor prognosis across multiple tumor types. The hypoxic microenvironments inside tumors also limit the effectiveness of radiotherapy, chemotherapy, and immunotherapy. Several approaches to eliminate hypoxic state in tumors have been proposed to delay cancer progression and improve therapeutic efficacies. This review will summarize current knowledge on hyperoxia, used alone or in combination with other therapeutic modalities, in cancer treatment. Molecular mechanisms and undesired side effects of hyperoxia will also be discussed.

Cell-mediated immune resistance in cancer

The genetic and epigenetic aberrations that underlie immune resistance lead to tumors that are refractory to clinically established and experimental immunotherapies, including monoclonal antibodies and T cell-based therapies. From various forms of cytotoxic T cells to small molecule inhibitors that revamp the tumor microenvironment, these therapies have demonstrated notable responses in cancer models and a resistant subset of cancer patients, used both alone and in combination. However, even current approaches, such as those targeting checkpoint molecules, tumor ligands, and involving gene-related therapies, present a challenge in non-responding patients. In this perspective, we discuss the most common mechanisms of immune resistance, including tumor heterogeneity, tumor ligand and major histocompatibility complex modulation, anti-apoptotic pathways, checkpoint inhibitory ligands, immunosuppressive cells and factors in the tumor microenvironment, and activation-induced cell death. In addition, we discuss the strategies designed to circumvent these resistance pathways to showcase the potential of emerging technologies in battling the rise of resistance.

Constitutive or Induced HIF-2 Addiction is Involved in Resistance to Anti-EGFR Treatment and Radiation Therapy in HNSCC

BACKGROUND

management of head and neck squamous cell carcinomas (HNSCC) include anti-Epidermal Growth Factor Receptor (EGFR) antibodies and radiotherapy, but resistance emerges in most patients. RAS mutations lead to primary resistance to EGFR blockade in metastatic colorectal cancer but are infrequent in HNSCC, suggesting that other mechanisms are implicated. Since hypoxia and Hypoxia Inducible Factor-1 (HIF-1) have been associated with treatment failure and tumor progression, we hypothesized that EGFR/mammalian Target Of Rapamycin (mTOR)/HIF-1 axis inhibition could radiosensitize HNSCC.

METHODS

We treated the radiosensitive Cal27 used as control, and radioresistant SQ20B and UD-SCC1 cells, in vivo and in vitro, with rapamycin and cetuximab before irradiation and evaluated tumor progression and clonogenic survival.

RESULTS

Rapamycin and cetuximab inhibited the mTOR/HIF-1α axis, and sensitized the SQ20B cell line to EGFR-inhibition. However, concomitant delivery of radiation to SQ20B xenografts increased tumor relapse frequency, despite effective HIF-1 inhibition. Treatment failure was associated with the induction of HIF-2α expression by cetuximab and radiotherapy. Strikingly, SQ20B and UD-SCC1 cells clonogenic survival dropped <30% after HIF-2α silencing, suggesting a HIF-2-dependent mechanism of oncogenic addiction.

CONCLUSIONS

altogether, our data suggest that resistance to EGFR inhibition combined with radiotherapy in HNSCC may depend on tumor HIF-2 expression and underline the urgent need to develop novel HIF-2 targeted treatments.

Yin Yang 1 facilitates hepatocellular carcinoma cell lipid metabolism and tumor progression by inhibiting PGC-1β-induced fatty acid oxidation

Lipid accumulation is a driving force in tumor development, as it provides tumor cells with both energy and the building blocks of phospholipids for construction of cell membranes. Aberrant homeostasis of lipid metabolism has been observed in various tumors; however, the molecular mechanism has not been fully elucidated.

Methods: Yin yang 1 (YY1) expression in hepatocellular carcinoma (HCC) was analyzed using clinical specimens, and its roles in HCC in lipid metabolism were examined using gain- and loss-of function experiments. The mechanism of YY1 regulation on peroxisome proliferator-activated receptor gamma coactivator-1β (PGC-1β) and its downstream genes medium-chain acyl-CoA dehydrogenase (MCAD) and long-chain acyl-CoA dehydrogenase (LCAD) were investigated using molecular biology and biochemical methods. The role of YY1/ PGC-1β axis in hepatocarcinogenesis was studied using xenograft experiment.

Results: This study showed that YY1 suppresses fatty acid β-oxidation, leading to increase of cellular triglyceride level and lipid accumulation in HCC cells, and subsequently induction of the tumorigenesis potential of HCC cells. Molecular mechanistic study revealed that YY1 blocks the expression of PGC-1β, an activator of fatty acid β-oxidation, by directly binding to its promoter; and thus downregulates PGC-1β/MCAD and PGC1-β/LCAD axis. Importantly, we revealed that YY1 inhibition on PGC-1β occurs irrespective of the expression of hypoxia-inducible factor-1α (HIF1-α), enabling it to promote lipid accumulation under both normoxic and hypoxic conditions.

Conclusion: Our study reveals the critical role of YY1/PGC-1β axis in HCC cell lipid metabolism, providing novel insight into the molecular mechanisms associated with tumor cell lipid metabolism, and a new perspective regarding the function of YY1 in tumor progression. Thus, our study provides evidences regarding the potential of YY1 as a target for lipid metabolism-based anti-tumor therapy.

Targeting Angiogenesis With Peptide Vaccines

Most cancer peptide vaccinations tested so far are capable of eliciting a strong immune response, but demonstrate poor clinical benefits. Since peptide vaccination is safe and well-tolerated, and several indications suggest that it has clear potential advantages over other modalities of treatment, it is important to investigate the reasons for these clinical failures. In this review, the current state of the art in targeting angiogenic proteins via peptide vaccines is presented, and the underlying reasons for both the successes and the failures are analyzed. The review highlights a number of areas critical for future success, including choice of target antigens, types of peptides used, delivery methods and use of proper adjuvants, and suggests ways to achieve better clinical results in the future.

CSCs in Breast Cancer-One Size Does Not Fit All: Therapeutic Advances in Targeting Heterogeneous Epithelial and Mesenchymal CSCs

Unlike other breast cancer subtypes, triple-negative breast cancer (TNBC) has no specific targets and is characterized as one of the most aggressive subtypes of breast cancer that disproportionately accounts for the majority of breast cancer-related deaths. Current conventional chemotherapeutics target the bulk tumor population, but not the cancer stem cells (CSCs) that are capable of initiating new tumors to cause disease relapse. Recent studies have identified distinct epithelial-like (E) ALDH⁺ CSCs, mesenchymal-like (M) CD44⁺/CD24^- CSCs, and hybrid E/M ALDH⁺/CD44⁺/CD24^- CSCs. These subtypes of CSCs exhibit differential signal pathway regulations, possess plasticity, and respond differently to treatment. As such, co-inhibition of different subtypes of CSCs is key to viable therapy. This review serves to highlight different pathway regulations in E and M CSCs in TNBC, and to further describe their role in disease progression. Potential inhibitors targeting E and/or M CSCs based on clinical trials are summarized for further investigation. Since future research needs to adopt suitable tumor models and take into account the divergence of E and M CSCs for the development of effective treatments, TNBC models for clinically translatable studies are further discussed.

Novel therapeutics: response and resistance in ovarian cancer

Here we review the latest pre-clinical and clinical developments for treatment of ovarian cancer, presented at the American Association of Cancer Research/Rivkin Center Ovarian Cancer Research Symposium held at the University of Washington in September 2018. Abstracts and presentations pertaining to the 'Novel Therapeutics' session were reviewed and are summarized here. The session featured a keynote presentation from Dr Ursula Matulonis, who summarized the current state of the art of treatment of ovarian cancer, including recent clinical trials incorporating the use of novel agents, including poly-ADP-ribose polymerase (PARP) inhibitors, other DNA-damaging agents, vascular endothelial growth factor receptor inhibitors, mirvetuximab soravtansine, and immune checkpoint blockade. Dr Jung-Min Lee then summarized the rationale and the results of early studies for targeting cell cycle checkpoint kinases for anti-cancer therapy. Eight submissions were selected for oral presentations, and 36 abstracts were presented as posters. The topics covered a range of clinical and pre-clinical strategies and biomarkers, including immunotherapy, mechanisms of chemotherapy, and PARP inhibitor resistance, DNA-damaging agents, and other novel therapeutic strategies. Key studies have highlighted that resistance to chemotherapy and PARP inhibitors remain a major challenge in therapy of ovarian cancer. Cancer stem cells represent an important mechanism of chemoresistance and strategies to target these cells may be a pathway to prevention of ovarian cancer relapse. Advancement of novel therapeutics targeting DNA damage, cell metabolism, and endoplasmic reticulum present some of the novel strategies in the pipeline. Emerging compelling pre-clinical data with novel antibody-drug conjugates targeting various surface receptors in ovarian cancer alone and in combination with immune checkpoint blockade generate a strong enthusiasm for rapid translation of these strategies to clinic.

HIF-1α is over-expressed in leukemic cells from TP53-disrupted patients and is a promising therapeutic target in chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL), the hypoxia-inducible factor 1 (HIF-1) regulates the response of tumor cells to hypoxia and their protective interactions with the leukemic microenvironment. In this study, we demonstrate that CLL cells from TP53-disrupted (TP53^dis) patients have constitutively higher expression levels of the α-subunit of HIF-1 (HIF-1α) and increased HIF-1 transcriptional activity compared to the wild-type counterpart. In the TP53^dis subset, HIF-1α upregulation is due to reduced expression of the HIF-1α ubiquitin ligase von Hippel-Lindau protein (pVHL). Hypoxia and stromal cells further enhance HIF-1α accumulation, independently of TP53 status. Hypoxia acts through the downmodulation of pVHL and the activation of the PI3K/AKT and RAS/ERK1-2 pathways, whereas stromal cells induce an increased activity of the RAS/ERK1-2, RHOA/RHOA kinase and PI3K/AKT pathways, without affecting pVHL expression. Interestingly, we observed that higher levels of HIF-1A mRNA correlate with a lower susceptibility of leukemic cells to spontaneous apoptosis, and associate with the fludarabine resistance that mainly characterizes TP53^dis tumor cells. The HIF-1α inhibitor BAY87-2243 exerts cytotoxic effects toward leukemic cells, regardless of the TP53 status, and has anti-tumor activity in Em-TCL1 mice. BAY87-2243 also overcomes the constitutive fludarabine resistance of TP53^dis leukemic cells and elicits a strongly synergistic cytotoxic effect in combination with ibrutinib, thus providing preclinical evidence to stimulate further investigation into use as a potential new drug in CLL.

The up-regulation of P62 levels is associated with resistance of sorafenib in hepatocarcinoma cells

BACKGROUND

Sorafenib is one of the most commonly used systemic therapies for hepatocellular carcinoma (HCC), but the acquired resistance towards sorafenib found in HCC patients usually led to failure of treatment and poor prognosis. Therefore, there is an urgent need to study the molecular mechanism caused by the acquired resistance. Previous studies demonstrated that P62 plays an important role in tumor cell resistance towards systemic therapies including chemotherapy and targeted therapy. However, the role of P62 in acquired resistance to sorafenib in HCC has not been clearly investigated.

MATERIALS AND METHODS

In this study we screened the most sensitive HCC cell lines towards sorafenib using CCK8. Then on this cell line, we analyzed the relationship between P62 expression level and the sensitivity towards sorafenib by western blot and CCK8. After knockdown and overexpression of P62 in HCC cells, cells were then treated with sorafenib. After that, we detect changes of sensitivity towards sorafenib. HCC samples were used to investigate the expression of P62 and their survival time.

RESULTS

Among four HCC cell lines in our lab, HepG2 cell line with the highest sensitivity to sorafenib was screened and selected. After treatment with sorafenib, the expression of P62 was significantly increased. In HCC cells, we found that significant up-regulation of P62 was correlated with the reduction of sorafenib sensitivity. In HCC samples, we found that the expression of P62 was associated with sorafenib resistance and a shorter survival time.

CONCLUSION

The up-regulation of P62 could reduce the sensitivity of HCC towards sorafenib. Thus, P62 could be therapeutic target to overcome sorafenib acquired resistance in the future.

Co-Delivery of Metformin Enhances the Antimultidrug Resistant Tumor Effect of Doxorubicin by Improving Hypoxic Tumor Microenvironment

Doxorubicin (DOX) is a first-line chemo drug for cancer therapy, yet it fails to treat multi-drug-resistant tumors. Hypoxia is a major causative factor leading to chemotherapy failure. Particularly, hypoxia up-regulates its responsive transcription factor-hypoxia-inducible factors (HIF)-to induce the overexpression of drug resistant genes. Metformin (MET) is recently found to cooperate with DOX against multiple tumors. As a mitochondrial inhibitor, MET could suppress tumor oxygen consumption, and thereby modulate the hypoxic tumor microenvironment. In this study, we used cationic liposomes to codeliver both DOX and MET for treating multi-drug-resistant breast cancer cells-MCF7/ADR. Faster release of MET enhanced the cytotoxicity of DOX through attenuating hypoxic stress both in vivo and in vitro. MET diminished the cellular oxygen consumption and inhibited HIF1α and P-glycoprotein (Pgp) expression in vitro. In addition, the dual-drug-loaded liposomes increased tumor targeting and intratumoral blood oxygen saturation, which suggested that the tumor reoxygenation effect of MET facilitated the exertion of its synergistic activity with DOX against MCF7/ADR xenografts. In general, our study represents a feasible strategy to boost the therapeutic effect in treating multi-drug-resistant cancer by improving the hypoxic tumor microenvironment.

Azo-based near-infrared fluorescent theranostic probe for tracking hypoxia-activated cancer chemotherapy in vivo

A novel azo-based near-infrared fluorescent therabostic probe activated by hypoxia is applied to real-time visualization of drug delivery in vivo.

Development of [131I]I-EOE-TPZ and [131I]I-EOE-TPZMO: Novel Tirapazamine (TPZ)-Based Radioiodinated Pharmaceuticals for Application in Theranostic Management of Hypoxia

Introduction: Benzotriazine-1,4-dioxides (BTDOs) such as tirapazamine (TPZ) and its derivatives act as radiosensitizers of hypoxic tissues. The benzotriazine-1-monoxide (BTMO) metabolite (SR 4317, TPZMO) of TPZ also has radiosensitizing properties, and via unknown mechanisms, is a potent enhancer of the radiosensitizing effects of TPZ. Unlike their 2-nitroimidazole radiosensitizer counterparts, radiolabeled benzotriazine oxides have not been used as radiopharmaceuticals for diagnostic imaging or molecular radiotherapy (MRT) of hypoxia. The radioiodination chemistry for preparing model radioiodinated BTDOs and BTMOs is now reported. Hypothesis: Radioiodinated 3-(2-iodoethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxide (I-EOE-TPZ), a novel bioisosteric analogue of TPZ, and 3-(2-iodoethoxyethyl)-amino-1,2,4-benzotriazine-1-oxide (I-EOE-TPZMO), its monoxide analogue, are candidates for in vivo and in vitro investigations of biochemical mechanisms in pathologies that develop hypoxic microenvironments. In theory, both radiotracers can be prepared from the same precursors. Methods: Radioiodination procedures were based on classical nucleophilic [¹³¹I]iodide substitution on Tos-EOE-TPZ (P1) and by [¹³¹I]iodide exchange on I-EOE-TPZ (P2). Reaction parameters, including temperature, reaction time, solvent and the influence of pivalic acid on products’ formation and the corresponding radiochemical yields (RCY) were investigated. Results: The [¹³¹I]iodide labeling reactions invariably led to the synthesis of both products, but with careful manipulation of conditions the preferred product could be recovered as the major product. Radioiodide exchange on P2 in ACN at 80 ± 5 °C for 30 min afforded the highest RCY, 89%, of [¹³¹I]I-EOE-TPZ, which upon solid phase purification on an alumina cartridge gave 60% yield of the product with over 97% of radiochemical purity. Similarly, radioiodide exchange on P2 in ACN at 50 ± 5 °C for 30 min with pivalic acid afforded the highest yield, 92%, of [¹³¹I]I-EOE-TPZMO exclusively with no trace of [¹³¹I]I-EOE-TPZ. In both cases, extended reaction times and/or elevated temperatures resulted in the formation of at least two additional radioactive reaction products. Conclusions: Radioiodination of P1 and P2 with [¹³¹I]iodide leads to the facile formation of [¹³¹I]I-EOE-TPZMO. At 80 °C and short reaction times, the facile reduction of the N-4-oxide moiety was minimized to afford acceptable radiochemical yields of [¹³¹I]I-EOE-TPZ from either precursor. Regeneration of [¹³¹I]I-EOE-TPZ from [¹³¹I]I-EOE-TPZMO is impractical after reaction work-up.

The critical role of microRNAs in stress response: Therapeutic prospect and limitation

Stress response refers to the systemic nonspecific response upon exposure to strong stimulation or chronic stress, such as severe trauma, shock, infection, burn, major surgery or improper environment, which disturb organisms and damage their physical and psychological health. However, the pathogenesis of stress induced disorder remains complicated and diverse under different stress exposure. Recently, studies have revealed a specific role of microRNAs (miRNAs) in regulating cellular function under different types of stress, suggesting a significant role in the treatment and prevention of stress-related diseases, such as stress ulcer, posttraumatic stress disorder, stress-induced cardiomyopathy and so on. This paper have reviewed the literature on microRNA related stress diseases in different databases including PubMed, Web of Science, and the MiRbase. It considers only peer-reviewed papers published in English between 2004 and 2018. This review summarizes new advances in principles and mechanisms of miRNAs regulating stress signalling pathway and the role of miRNAs in human stress diseases. This comprehensive review is to provide an integrated account of how different stresses affect miRNAs and how stress-miRNA pathways may, in turn, be linked with disease, which offers some potential strategies for stress disorder treatment. Furthermore, the limitation of current studies and challenges for clinical use are discussed.