Bortezomib sensitizes esophageal squamous cancer cells to radiotherapy by suppressing the expression of HIF-1α and apoptosis proteins

HDS screening with patient-derived primary cells guided individualized therapy for esophageal squamous cell carcinoma-in vivo and vitro

Objective

To analyze and evaluate the role of the High-throughput Drug Sensitivity (HDS) screening strategy in identifying highly sensitive drugs against esophageal squamous cell carcinoma (ESCC).

Methods

A total of 80 patients with progressive ESCC were randomly divided into the observation (40 cases) and the control groups (40 cases). In the observation group, primary ESCC cells were isolated from the tumor tissues with a gastroscope, and drug sensitivity screening was performed on cells derived from the 40 ESCC cases using the HDS method, followed by verification in a patient-derived tumor xenograft (PDX) mouse model. Finally, the differences in the therapeutic efficacy (levels of CEA, CYFRA21-1, SCCA after chemotherapy and the rates of overall survival, local progression, and distant metastasis at 12 months and 18 months time points after chemotherapy) were compared between the observation group (Screened drug-treated) and the control group (Paclitaxel combined with cisplatin regimen-treated).

Results

Forty ESCC patients were screened for nine different high-sensitive chemotherapeutics, with the majority showing sensitivity to Bortezomib. Experiments on animal models revealed that the tumor tissue mass of PDX mice treated with the HDS-screened drug was significantly lower than that of the Paclitaxel-treated mice (p < 0.05), and the therapeutic efficacy of the observation group was better than the control group (p < 0.05).

Conclusion

HDS screening technology can be beneficial in screening high-efficacy anticancer drugs for advanced-stage ESCC patients, thereby minimizing adverse drug toxicity in critically ill patients. Moreover, this study provides a new avenue for treating advanced ESCC patients with improved outcomes.

Thrombospondin-1 induction and VEGF reduction by proteasome inhibition

The present study focuses on investigating the expression of thrombospondin-1 (TSP-1), a natural inhibitor of neovascularization. Immunofluorescent staining was used to detect the expression of TSP-1 in rabbit corneal tissue with vascularization induced by limbectomy. TSP-1 was detected in healthy and Cultured Autologous Oral Mucosal Epithelial Cell Sheet (CAOMECS) grafted rabbit corneas. TSP-1 was not detected in diseased corneas. Rabbit and human primary oral mucosal and corneal epithelial cells were cultured and treated with proteasome inhibitor (PI) in vitro. Changes in the expression of TSP-1, HIF-1 alpha and 2 alpha, VEGF-A, and VEGF receptor were analyzed by Western blotting. Neovascularization developed in rabbits' corneas as early as 1 month after limbectomy and was stable for at least 3 months. HIF-1 alpha and VEGF-A expression was reduced in CAOMECS grafted corneas, as compared to sham corneas. While TSP-1 expression was decreased in injured corneas, it was expressed in CAOMECS grafted corneas, but still less expressed compared to healthy corneas. PI treatment, of human oral mucosal and corneal epithelial cells increased TSP-1 expression and reduced VEGF-A expression. The results showed that TSP-1 expression was lost in injured corneal surface and that CAOMECS grafting restored TSP-1 expression to certain extent. Proteasome inhibition treatment increased TSP-1 and decreased VEGF-A expression in human oral mucosal and corneal epithelial cells. The result suggests that corneal neovascularization could be managed with the inhibition of the proteasome after CAOMECS grafting and increase corneal transparency.

DNA repair pathways as a novel therapeutic strategy in esophageal cancer: A review study

Esophageal cancer (EC) is a common malignancy with a poor prognosis worldwide. There are two core pathways that repair double-strand breaks, homologous recombination (HR) and non-homologous end joining (NHEJ) and numerous proteins are recognized that affect the occurrence of HR and NHEJ. Altered DNA damage response (DDR) pathways are associated with cancer susceptibility and affect therapeutic response and resistance in cancers. DDR pathway alterations in EC are still poorly understood. Therefore, the identification of alterations in specific genes in DDR pathways may potentially result in novel treatments for resistant cancers, especially EC. In this review, we aimed to focus on different aspects of DNA damage and repair processes in EC. Also, we reviewed new therapeutic strategies via targeting DNA repair machinery components.

Effect of Glut-1 and HIF-1α double knockout by CRISPR/CAS9 on radiosensitivity in laryngeal carcinoma via the PI3K/Akt/mTOR pathway

Hypoxic resistance is the main obstacle to radiotherapy for laryngeal carcinoma. Our previous study indicated that hypoxia-inducible factor 1α (HIF-1α) and glucose transporter 1 (Glut-1) double knockout reduced tumour biological behaviour in laryngeal carcinoma cells. However, their radioresistance mechanism remains unclear. In this study, cell viability was determined by CCK8 assay. Glucose uptake capability was evaluated by measurement of ¹⁸ F-fluorodeoxyglucose radioactivity. A tumour xenograft model was established by subcutaneous injection of Tu212 cells. Tumour histopathology was determined by haematoxylin and eosin staining, immunohistochemical staining, and TUNEL assays. Signalling transduction was evaluated by Western blotting. We found that hypoxia induced radioresistance in Tu212 cells accompanied by increased glucose uptake capability and activation of the PI3K/Akt/mTOR pathway. Inhibition of PI3K/Akt/mTOR activity abolished hypoxia-induced radioresistance and glucose absorption. Mechanistic analysis revealed that hypoxia promoted higher expressions of HIF-1α and Glut-1. Moreover, the PI3K/Akt/mTOR pathway was a positive mediator of HIF-1α and/or Glut-1 in the presence of irradiation. HIF-1α and/or Glut-1 knockout significantly reduced cell viability, glucose uptake and PI3K/Akt/mTOR activity, all of which were induced by hypoxia in the presence of irradiation. In vivo analysis showed that knockout of HIF-1α and/or Glut-1 also inhibited tumour growth by promoting cell apoptosis, more robustly compared with the PI3K inhibitor wortmannin, particularly in tumours with knockout of both HIF-1α and Glut-1. HIF-1α and/or Glut-1 knockout also abrogated PI3K/Akt/mTOR signalling transduction in tumour tissues, in a manner similar to wortmannin. HIF-1α and/or Glut-1 knockout facilitated radiosensitivity in laryngeal carcinoma Tu212 cells by regulation of the PI3K/Akt/mTOR pathway.

Improving the synergistic combination of programmed death‐1/programmed death ligand‐1 blockade and radiotherapy by targeting the hypoxic tumour microenvironment

Immune checkpoint inhibition with PD‐1/PD‐L1 blockade is a promising area in the field of anti‐cancer therapy. Although clinical data have revealed success of PD‐1/PD‐L1 blockade as monotherapy or in combination with CTLA‐4 or chemotherapy, the combination with radiotherapy could further boost anti‐tumour immunity and enhance clinical outcomes due to the immunostimulatory effects of radiation. However, the synergistic combination of PD‐1/PD‐L1 blockade and radiotherapy can be challenged by the complex nature of the tumour microenvironment (TME), including the presence of tumour hypoxia. Hypoxia is a major barrier to the effectiveness of both radiotherapy and PD‐1/PD‐L1 blockade immunotherapy. Thus, targeting the hypoxic TME is an attractive strategy to enhance the efficacy of the combination. Addition of compounds that directly or indirectly reduce hypoxia, to the combination of PD‐1/PD‐L1 inhibitors and radiotherapy may optimize the success of the combination and improve therapeutic outcomes. In this review, we will discuss the synergistic combination of PD‐1/PD‐L1 blockade and radiotherapy and highlight the role of hypoxic TME in impeding the success of both therapies. In addition, we will address the potential approaches for targeting tumour hypoxia and how exploiting these strategies could benefit the combination of PD‐1/PD‐L1 blockade and radiotherapy.

Targeting Epithelial-to-Mesenchymal Transition in Radioresistance: Crosslinked Mechanisms and Strategies

Radiotherapy exerts a crucial role in curing cancer, however, its treatment efficiency is mostly limited due to the presence of radioresistance. Epithelial-to-mesenchymal transition (EMT) is a biological process that endows the cancer cells with invasive and metastatic properties, as well as radioresistance. Many potential mechanisms of EMT-related radioresistance being reported have broaden our cognition, and hint us the importance of an overall understanding of the relationship between EMT and radioresistance. This review focuses on the recent progresses involved in EMT-related mechanisms in regulating radioresistance, irradiation-mediated EMT program, and the intervention strategies to increase tumor radiosensitivity, in order to improve radiotherapy efficiency and clinical outcomes of cancer patients.

Targeting the Microenvironment in Esophageal Cancer

Esophageal cancer (EC) is the eighth most common type of cancer and the sixth leading cause of cancer-related deaths worldwide. At present, the clinical treatment for EC is based mainly on radical surgery, chemotherapy, and radiotherapy. However, due to the limited efficacy of conventional treatments and the serious adverse reactions, the outcome is still unsatisfactory (the 5-year survival rate for patients is less than 25%). Thus, it is extremely important and urgent to identify new therapeutic targets. The concept of tumor microenvironment (TME) has attracted increased attention since it was proposed. Recent studies have shown that TME is an important therapeutic target for EC. Microenvironment-targeting therapies such as immunotherapy and antiangiogenic therapy have played an indispensable role in prolonging survival and improving the prognosis of patients with EC. In addition, many new drugs and therapies that have been developed to target microenvironment may become treatment options in the future. We summarize the microenvironment of EC and the latest advances in microenvironment-targeting therapies in this review.

Interfering with Tumor Hypoxia for Radiotherapy Optimization

Hypoxia in solid tumors is an important predictor of treatment resistance and poor clinical outcome. The significance of hypoxia in the development of resistance to radiotherapy has been recognized for decades and the search for hypoxia-targeting, radiosensitizing agents continues. This review summarizes the main hypoxia-related processes relevant for radiotherapy on the subcellular, cellular and tissue level and discusses the significance of hypoxia in radiation oncology, especially with regard to the current shift towards hypofractionated treatment regimens. Furthermore, we discuss the strategies to interfere with hypoxia for radiotherapy optimization, and we highlight novel insights into the molecular pathways involved in hypoxia that might be utilized to increase the efficacy of radiotherapy.

Effects of a combined therapy of bortezomib and ionizing radiation on chondrosarcoma three-dimensional spheroid cultures

Chondrosarcomas represent a heterogeneous group of primary bone cancers that are characterized by hyaline cartilaginous neoplastic tissue and are predominantly resistant to radiation and chemotherapy. However, adjuvant radiotherapy is often recommended in inoperable cases or after incomplete resections. To improve the efficiency of treatment, the present study tested a combination therapy with ionizing radiation (IR) and the proteasome inhibitor bortezomib. Using a three-dimensional (3D) spheroid model, 0-20 Gy of IR was applied to chondrosarcoma cells and healthy human chondrocytes. Following combined treatment with IR and bortezomib, the cell cycle distribution, apoptotic induction, the survivin pathway, autophagy and DNA damage were evaluated. Both cell types exhibited a slight decrease in viability following increasing doses of IR; the chondrosarcoma cells demonstrated a significant dose-dependent increase in the expression levels of the DNA damage marker histone H2AX phosphorylation at serine 139 (γH2AX). The combination treatment with bortezomib significantly decreased the cell viability after 48 h compared with that in irradiated cells. High-dose IR induced a G2/M phase arrest, which was accompanied by a decrease in the number of cells at the G1 and S phase. Co-treatment with bortezomib changed the distribution of the cell cycle phases. The mRNA expression levels of the proapoptotic genes Bcl-2-associated X protein (Bax) and Bak were significantly increased by bortezomib treatment and combination therapy with IR. In addition, the combination therapy resulted in a synergistic decrease of the expression levels of survivin and its corresponding downstream pathway molecules, including heat shock protein 90, X-linked inhibitor of apoptosis protein, smad 2 and smad 3. Comparative analyses of γH2AX at 1 and 24 h post-IR revealed efficient DNA repair in human chondrosarcoma cells. Therefore, additional bortezomib treatment may only temporarily improve the radiation sensitivity of chondrosarcoma cells. However, the inhibition of the survivin pathway by the combined treatment with IR and bortezomib, observed in the present study, revealed a novel aspect in the tumor biology of chondrosarcoma 3D spheroid cultures and may represent a potential target for therapy.

Hypoxia-Induced Cancer Cell Responses Driving Radioresistance of Hypoxic Tumors: Approaches to Targeting and Radiosensitizing

Simple Summary

Some regions of aggressive malignancies experience hypoxia due to inadequate blood supply. Cancer cells adapting to hypoxic conditions somehow become more resistant to radiation exposure and this decreases the efficacy of radiotherapy toward hypoxic tumors. The present review article helps clarify two intriguing points: why hypoxia-adapted cancer cells turn out radioresistant and how they can be rendered more radiosensitive. The critical molecular targets associated with intratumoral hypoxia and various approaches are here discussed which may be used for sensitizing hypoxic tumors to radiotherapy.

Abstract

Within aggressive malignancies, there usually are the “hypoxic zones”—poorly vascularized regions where tumor cells undergo oxygen deficiency through inadequate blood supply. Besides, hypoxia may arise in tumors as a result of antiangiogenic therapy or transarterial embolization. Adapting to hypoxia, tumor cells acquire a hypoxia-resistant phenotype with the characteristic alterations in signaling, gene expression and metabolism. Both the lack of oxygen by itself and the hypoxia-responsive phenotypic modulations render tumor cells more radioresistant, so that hypoxic tumors are a serious challenge for radiotherapy. An understanding of causes of the radioresistance of hypoxic tumors would help to develop novel ways for overcoming this challenge. Molecular targets for and various approaches to radiosensitizing hypoxic tumors are considered in the present review. It is here analyzed how the hypoxia-induced cellular responses involving hypoxia-inducible factor-1, heat shock transcription factor 1, heat shock proteins, glucose-regulated proteins, epigenetic regulators, autophagy, energy metabolism reprogramming, epithelial–mesenchymal transition and exosome generation contribute to the radioresistance of hypoxic tumors or may be inhibited for attenuating this radioresistance. The pretreatments with a multitarget inhibition of the cancer cell adaptation to hypoxia seem to be a promising approach to sensitizing hypoxic carcinomas, gliomas, lymphomas, sarcomas to radiotherapy and, also, liver tumors to radioembolization.

The crosstalk between HIFs and mitochondrial dysfunctions in cancer development

Mitochondria are essential cellular organelles that are involved in regulating cellular energy, metabolism, survival, and proliferation. To some extent, cancer is a genetic and metabolic disease that is closely associated with mitochondrial dysfunction. Hypoxia-inducible factors (HIFs), which are major molecules that respond to hypoxia, play important roles in cancer development by participating in multiple processes, such as metabolism, proliferation, and angiogenesis. The Warburg phenomenon reflects a pseudo-hypoxic state that activates HIF-1α. In addition, a product of the Warburg effect, lactate, also induces HIF-1α. However, Warburg proposed that aerobic glycolysis occurs due to a defect in mitochondria. Moreover, both HIFs and mitochondrial dysfunction can lead to complex reprogramming of energy metabolism, including reduced mitochondrial oxidative metabolism, increased glucose uptake, and enhanced anaerobic glycolysis. Thus, there may be a connection between HIFs and mitochondrial dysfunction. In this review, we systematically discuss the crosstalk between HIFs and mitochondrial dysfunctions in cancer development. Above all, the stability and activity of HIFs are closely influenced by mitochondrial dysfunction related to tricarboxylic acid cycle, electron transport chain components, mitochondrial respiration, and mitochondrial-related proteins. Furthermore, activation of HIFs can lead to mitochondrial dysfunction by affecting multiple mitochondrial functions, including mitochondrial oxidative capacity, biogenesis, apoptosis, fission, and autophagy. In general, the regulation of tumorigenesis and development by HIFs and mitochondrial dysfunction are part of an extensive and cooperative network.

Therapeutic Strategies Against Cancer Stem Cells in Esophageal Carcinomas

Cancer stem cells (CSCs) in esophageal cancer have a key role in tumor initiation, progression and therapy resistance. Novel therapeutic strategies to target CSCs are being tested, however, more in-depth research is necessary. Eradication of CSCs can result in successful therapeutic approaches against esophageal cancer. Recent evidence suggests that targeting signaling pathways, miRNA expression profiles and other properties of CSCs are important strategies for cancer therapy. Wnt/β-catenin, Notch, Hedgehog, Hippo and other pathways play crucial roles in proliferation, differentiation, and self-renewal of stem cells as well as of CSCs. All of these pathways have been implicated in the regulation of esophageal CSCs and are potential therapeutic targets. Interference with these pathways or their components using small molecules could have therapeutic benefits. Similarly, miRNAs are able to regulate gene expression in esophageal CSCs, so targeting self-renewal pathways with miRNA could be utilized to as a potential therapeutic option. Moreover, hypoxia plays critical roles in esophageal cancer metabolism, stem cell proliferation, maintaining aggressiveness and in regulating the metastatic potential of cancer cells, therefore, targeting hypoxia factors could also provide effective therapeutic modalities against esophageal CSCs. To conclude, additional study of CSCs in esophageal carcinoma could open promising therapeutic options in esophageal carcinomas by targeting hyper-activated signaling pathways, manipulating miRNA expression and hypoxia mechanisms in esophageal CSCs.

Advances in Characterizing Recently-Identified Molecular Actions of Melatonin: Clinical Implications

Melatonin, N-acetyl-5-methoxy-tryptamine, was discovered to be a product of serotonin metabolism in the mammalian pineal gland where its synthesis is under control of the light:dark cycle. Besides its regulatory pathway involving ganglion cells in the retina, the neural connections between the eyes and the pineal gland include the master circadian clock, the suprachiasmatic nuclei, and the central and peripheral nervous systems. Since pineal melatonin is released into the blood and into the cerebrospinal fluid, it has access to every cell in an organism and it mediates system-wide effects. Subsequently, melatonin was found in several extrapineal organs and, more recently, perhaps in every cell of every organ. In contrast to the pinealocytes, non-pineal cells do not discharge melatonin into the blood; rather it is used locally in an intracrine, autocrine, or paracrine manner. Melatonin levels in non-pineal cells do not exhibit a circadian rhythm and do not depend on circulating melatonin concentrations although when animals are treated with exogenous melatonin it is taken up by presumably all cells. Mitochondria are the presumed site of melatonin synthesis in all cells; the enzymatic machinery for melatonin synthesis has been identified in mitochondria. The association of melatonin with mitochondria, because of its ability to inhibit oxidative stress, is very fortuitous since these organelles are a major site of damaging reactive oxygen species generation. In this review, some of the actions of non-pineal-derived melatonin are discussed in terms of cellular and subcellular physiology.

Genome-Wide Profiling of the Toxic Effect of Bortezomib on Human Esophageal Carcinoma Epithelial Cells

Objectives:

Bortezomib has been widely used to treat multiple myeloma and other hematological malignancies. However, not much is known about its effect on solid tumors. The aim of this study was to study the effect of Bortezomib on human esophageal cancer cell lines and investigate the potential target pathways.

Methods:

Two human esophageal cancer cell lines, TE-1 and KYSE-150, were used in this study. Cell viability, cell cycle distribution, and apoptosis after Bortezomib treatment was detected by Cell Counting Kit-8, flow cytometry, and Annexin V/propidium iodide staining, respectively. The genes targeted by Bortezomib were analyzed at the messenger RNA level by microarray chips and quantitative real-time polymerase chain reaction.

Results:

The proliferation of human esophageal cancer cell lines was inhibited by Bortezomib in a dose- and time-dependent manner. Bortezomib treatment led to G₂/M arrest and apoptosis. Microarray chips revealed multiple signaling pathways targeted by Bortezomib, including proteasome, endoplasmic reticulum, Wnt-, and calcium-mediated pathway. The expression patterns of 4 representative genes UBD, CUL3, HDAC6, and GADD45A were verified by quantitative real-time polymerase chain reaction and showed consistency with the microarray assay.

Conclusion:

Bortezomib could suppress cell viability, cause G₂/M arrest, and induce apoptosis in human esophageal cancer cells, with possible targets including UBD, CUL3, HDAC6, and GADD45A.

Natural product β-thujaplicin inhibits homologous recombination repair and sensitizes cancer cells to radiation therapy

Investigation of natural products is an attractive strategy to identify novel compounds for cancer prevention and treatment. Numerous studies have shown the efficacy and safety of natural products, and they have been widely used as alternative treatments for a wide range of illnesses, including cancers. However, it remains unknown whether natural products affect homologous recombination (HR)-mediated DNA repair and whether these compounds can be used as sensitizers with minimal toxicity to improve patients' responses to radiation therapy, a mainstay of treatment for many human cancers. In this study, in order to systematically identify natural products with an inhibitory effect on HR repair, we developed a high-throughput image-based HR repair screening assay and screened a chemical library containing natural products. Among the most interesting of the candidate compounds identified from the screen was β-thujaplicin, a bioactive compound isolated from the heart wood of plants in the Cupressaceae family, can significantly inhibit HR repair. We further demonstrated that β-thujaplicin inhibits HR repair by reducing the recruitment of a key HR repair protein, Rad51, to DNA double-strand breaks. More importantly, our results showed that β-thujaplicin can radiosensitize cancer cells. Additionally, β-thujaplicin sensitizes cancer cells to PARP inhibitor in different cancer cell lines. Collectively, our findings for the first time identify natural compound β-thujaplicin, which has a good biosafety profile, as a novel HR repair inhibitor with great potential to be translated into clinical applications as a sensitizer to DNA-damage-inducing treatment such as radiation and PARP inhibitor. In addition, our study provides proof of the principle that our robust high-throughput functional HR repair assay can be used for a large-scale screening system to identify novel natural products that regulate DNA repair and cellular responses to DNA damage-inducing treatments such as radiation therapy.