The Critical Role of Hypoxic Microenvironment and Epigenetic Deregulation in Esophageal Cancer Radioresistance

Correlation of microscopic tumor extension with tumor microenvironment in esophageal cancer patients

OBJECTIVE

In the era of image-guided adaptive radiotherapy, definition of the clinical target volume (CTV) is a challenge in various solid tumors, including esophageal cancer (EC). Many tumor microenvironmental factors, e.g., tumor cell proliferation or cancer stem cells, are hypothesized to be involved in microscopic tumor extension (MTE). Therefore, this study assessed the expression of FAK, ILK, CD44, HIF-1α, and Ki67 in EC patients after neoadjuvant radiochemotherapy followed by tumor resection (NRCHT+R) and correlated these markers with the MTE.

METHODS

Formalin-fixed paraffin-embedded tumor resection specimens of ten EC patients were analyzed using multiplex immunofluorescence staining. Since gold fiducial markers had been endoscopically implanted at the proximal and distal tumor borders prior to NRCHT+R, correlation of the markers with the MTE was feasible.

RESULTS

In tumor resection specimens of EC patients, the overall percentages of FAK+, CD44+, HIF-1α+, and Ki67+ cells were higher in tumor nests than in the tumor stroma, with the outcome for Ki67+ cells reaching statistical significance (p < 0.001). Conversely, expression of ILK+ cells was higher in tumor stroma, albeit not statistically significantly. In three patients, MTE beyond the fiducial markers was found, reaching up to 31 mm.

CONCLUSION

Our findings indicate that the overall expression of FAK, HIF-1α, Ki67, and CD44 was higher in tumor nests, whereas that of ILK was higher in tumor stroma. Differences in the TME between patients with residual tumor cells in the original CTV compared to those without were not found. Thus, there is insufficient evidence that the TME influences the required CTV margin on an individual patient basis.

TRIAL REGISTRATION NUMBER AND DATE

BO-EK-148042017 and BO-EK-177042022 on 20.06.2022, DRKS00011886, https://drks.de/search/de/trial/DRKS00011886 .

Hypoxia-induced factor-1α promotes radioresistance of esophageal cancer cells by transcriptionally activating LINC01116 and suppressing miR-3612 under hypoxia

Esophageal cancer (EC) is a challenging tumor to treat with radiotherapy, often exhibiting resistance to this treatment modality. To explore the factors influencing radioresistance, we focused on the role of hypoxia-induced factor-1α (HIF-1α), and its interaction with the long noncoding RNA long intergenic nonprotein coding RNA 1116 (LINC01116). We analyzed the LINC01116 expression in EC and EC cell lines/human normal esophageal epithelial cell line (Het-1A). LINC01116 was silenced/overexpressed in EC109/KYSE30 cells under hypoxia, followed by radioresistance assessment. We measured HIF-1α levels in hypoxic EC cells and further validated the binding of HIF-1α with LINC01116, analyzing their interaction in EC cells. We then performed experiments in EC109 cells by transfection them with sh-HIF-1α/oe-LINC01116 to verify the effects. Additonally, we analyzed the localization of LINC01116 and its binding with miR-3612, followed by a combined experiment performed to validate the results. Our findings indicated that LINC01116 was highly expressed in EC and further elevated in hypoxic EC cells. LINC01116 was expressed at a high level in EC, which was further elevated in EC cells under hypoxic conditions. Knockdown of LINC01116 triggered EC cell apoptosis, thus suppressing radioresistance. Further investigation revealed that HIF-1α transcriptionally activated LINC01116 expression under hypoxia, and silencing HIF-1α lowered EC cell radioresistance by downregulating LINC01116. Under hypoxic conditions, LINC01116 could function as a sponge for miR-3612 and inhibit its expression. This interaction between LINC01116 and miR-3612 played a crucial role in mediating radioresistance in EC cells. Briefly, under hypoxic conditions, HIF-1α facilitates radioresistance of EC cells by transcriptionally activating LINC01116 expression and downregulating miR-3612.

Hypoxic tumor cell-derived small extracellular vesicle miR-152-3p promotes cervical cancer radioresistance through KLF15 protein

BACKGROUND

Radiotherapy is widely used in treating cervical cancer patients, however, radioresistance unavoidably occurs and seriously affects the treatment effect. It is well known that hypoxia plays an important role in promoting radioresistance in tumor microenvironment, yet our understanding of the effect of small extracellular vesicles miRNA on cervical cancer radiosensitivity in hypoxic environment is still limited.

METHODS

Small extracellular vesicles extracted from hypoxic and normoxic cultured cervical cancer cells were evaluated for their effects on radioresistance. miR-152-3p was found to be a potential effector in hypoxia-derived extracellular vesicles by searching the GEO database. Its downstream substrate was confirmed by double luciferase report, which was KLF15. The role of miR-152-3p and KLF15 in regulating cervical cancer radioresistance was detected by cell activity assays. The findings were confirmed in vivo by animal models. The expression of miR-152-3p was quantified by qRT-PCR and its prognostic significance was evaluated.

RESULTS

Hypoxic environment promoted the secretion of small extracellular vesicles, and reduced the apoptosis and DNA damage caused by radiation, accompanied by increased expression of small extracellular vesicles miR-152-3p from hypoxic cervical cancer cells. Furthermore, small extracellular vesicles miR-152-3p promoted Hela xenograft growth and reduced the radiosensitivity vivo. Mechanism studies revealed that KLF15 protein was the downstream target of miR-152-3p in regulating radioresistance.

CONCLUSION

Our findings suggest that small extracellular vesicles miR-152-3p affects the therapeutic effect of radiotherapy and holds potential as a biomarker or therapeutic target for cervical cancer prognosis and improving radiotherapy.

Epigenetics as a determinant of radiation response in cancer

Radiation therapy is a cornerstone of modern cancer treatment. Treatment is based on depositing focal radiation to the tumor to inhibit cell growth, proliferation and metastasis, and to promote the death of cancer cells. In addition, radiation also affects non-tumor cells in the tumor microenvironmental (TME). Radiation resistance of the tumor cells is the most common cause of treatment failure, allowing survival of cancer cell and subsequent tumor growing. Molecular radioresistance comprises genetic and epigenetic characteristics inherent in cancer cells, or characteristics acquired after exposure to radiation. Furthermore, cancer stem cells (CSCs) and non-tumor cells into the TME as stromal and immune cells have a role in promoting and maintaining radioresistant tumor phenotypes. Different regulatory molecules and pathways distinctive of radiation resistance include DNA repair, survival signaling and cell death pathways. Epigenetic mechanisms are one of the most relevant events that occur after radiotherapy to regulate the expression and function of key genes and proteins in the differential radiation-response. This article reviews recent data on the main molecular mechanisms and signaling pathways related to the biological response to radiotherapy in cancer; highlighting the epigenetic control exerted by DNA methylation, histone marks, chromatin remodeling and m6A RNA methylation on gene expression and activation of signaling pathways related to radiation therapy response.

Circ_0001686 knockdown suppresses tumorigenesis and enhances radiosensitivity in esophagus cancer through regulating miR-876-5p/SPIN1 axis

BACKGROUND

Abnormal expression of circular RNAs (circRNAs) plays an important role in tumorigenesis and radiosensitivity of many cancers. Nevertheless, it is not clear whether circ_0001686 is associated with the development and radiosensitivity of esophagus cancer.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression levels of circ_0001686, microRNA-876-5p (miR-876-5p) and spindlin 1 (SPIN1). Counting Kit-8 (CCK-8) assay, EdU assay, flow cytometry and transwell assay were applied to evaluate cell viability, cell proliferation, cell apoptosis and cell invasion capacities. Radiosensitivity was monitored by colony formation assay. The target relationship between miR-876-5p and circ_0001686 or SPIN1 was identified by dual-luciferase reporter assay. The protein level of SPIN1 was measured by western blot assay. Xenograft tumor models were used to analyze the influence of circ_0001686 on radiosensitivity and tumor growth in vivo.

RESULTS

The expression levels of circ_0001686 and SPIN1 were increased, while miR-876-5p was decreased in esophagus cancer tissues and cells. Interference of circ_0001686 constrained cell proliferation and invasion, but promoted cell apoptosis and radiosensitivity. Additionally, miR-876-5p was the target of circ_0001686 and miR-876-5p inhibition effectively ameliorated the impacts of circ_0001686 deficiency on tumorigenesis and radiosensitivity. Moreover, SPIN1 was a direct target of miR-876-5p and SPIN1 overexpression partially overturned the effects of miR-876-5p transfection on tumor progression and radiosensitivity. Importantly, circ_0001686 could sponge miR-876-5p to regulate SPIN1 expression. In addition, circ_0001686 silencing also constrained tumor growth and increased radiosensitivity in vivo.

CONCLUSION

Circ_0001686 contributed to the progression and radioresistance of esophagus cancer cells via regulating SPIN1 expression by targeting miR-876-5p, providing a new therapeutic target for improving the prognosis of esophagus cancer patients.

Long noncoding RNA CBR3-AS1 mediates tumorigenesis and radiosensitivity of non-small cell lung cancer through redox and DNA repair by CBR3-AS1 /miR-409-3p/SOD1 axis

The long noncoding RNA CBR3-AS1 has important functions in various cancers. However, the biological functions of CBR3-AS1 in non-small cell lung cancer (NSCLC) remain unclear. This study aimed to investigate the roles and molecular mechanisms of CBR3-AS1 in NSCLC tumorigenesis and radiosensitivity. Here, we demonstrate CBR3-AS1 overexpression in NSCLC tissue compared with adjacent normal tissue. CBR3-AS1 downregulation reduced proliferation, invasion, and migration; inhibited cell cycle progression; and promoted apoptosis of NSCLC cells. CBR3-AS1 also promoted tumor growth in vivo. CBR3-AS1 may regulate the expression and functions of the miR-409-3p target gene SOD1. CBR3-AS1 expression was negatively correlated with radiosensitivity. CBR3-AS1 downregulation decreased post-irradiation SOD1 expression, increased γH2AX formation, raised levels of reactive oxygen species, and promoted apoptosis. Our results suggest that CBR3-AS1 functions as an oncogene through the CBR3-AS1/miR-409-3p/SOD1 pathway, and may represent a new therapeutic target, especially to regulate radiosensitivity in NSCLC.

Methionine oxidation of CLK4 promotes the metabolic switch and redox homeostasis in esophageal carcinoma via inhibiting MITF selective autophagy

BACKGROUND

Metabolic reprogramming and redox homeostasis contribute to esophageal squamous cell carcinoma (ESCC). CDC-like kinase 4 (CLK4) is a dual-specificity kinase that can phosphorylate substrates' tyrosine or serine/threonine residue. However, the role and mechanism of CLK4 in ESCC remain unknown.

METHODS

CLK4 expression was analysed using publicly available datasets and confirmed in ESCC tissues and cell lines. The biological roles of CLK4 were studied with gain and loss-of-function experiments. Mass spectrometry was employed to examine the effects of CLK4 on metabolic profiling. In vitro kinase assay, co-immunoprecipitation, glutathione S-transferase pulldown, chromatin immunoprecipitation and luciferase reporter were used to elucidate the relationship among CLK4, microphthalmia-associated transcription factor (MITF), COP1 and ZRANB1.

RESULTS

CLK4 down-regulation was observed in ESCC cell lines and clinical samples and associated with the methylation of its promoter. Low levels of CLK4 promoted ESCC development by affecting the purine synthesis pathway and nicotinamide adenine dinucleotide phosphate (NADPH)/nicotinamide adenine dinucleotide phosphate (NADP+ ) ratio. Interestingly, CLK4 inhibited ESCC development by blocking MITF-enhanced de novo purine synthesis and redox balance. Mechanistically, wild type CLK4 (WT-CLK4) but not kinase-dead CLK4-K189R mutant phosphorylated MITF at Y360. This modification promoted its interaction with E3 ligase COP1 and its K63-linked ubiquitination at K308/K372, leading to sequestosome 1 recognition and autophagic degradation. However, the deubiquitinase ZRANB1 rescued MITF ubiquitination and degradation. In turn, MITF bound to E- rather than M-boxes in CLK4 promoter and transcriptionally down-regulated its expression in ESCC. Clinically, the negative correlations were observed between CLK4, MITF, and purine metabolic markers, which predicts a poor clinical outcome of ESCC patients. Notably, CLK4 itself was a redox-sensitive kinase, and its methionine oxidation at M307 impaired kinase activity, enhanced mitochondria length and inhibited lipid peroxidation, contributing to ESCC.

CONCLUSIONS

Our data highlight the potential role of CLK4 in modulating redox status and nucleotide metabolism, suggesting potential therapeutic targets in ESCC treatment.

Curcumin Administered in Combination with Glu-GNPs Induces Radiosensitivity in Transplanted Tumor MDA-MB-231-luc Cells in Nude Mice

Curcumin is a type of plant polyphenol extracted from Curcuma longa L. rhizome, which demonstrates antitumor activity in breast cancer cells in vitro. To investigate the combined effect and possible mechanism of curcumin and glucose-gold nanoparticles (Glu-GNPs), the radiosensitivity of breast carcinoma xenografts was assessed in nude mice. MDA-MB-231 cells labeled with firefly luciferase were inoculated into the mammary fatty pads of nude mice to establish a transplantation tumor model of human breast cancer. The tumor-bearing mice were treated with different drugs (curcumin, Glu-GNPs, and cisplatin) for 3 weeks prior to radiotherapy. The body weights and tumor volumes of the mice were measured in regular intervals. Tumor bioluminescence intensity was determined in real-time using an in vivo bioluminescence imaging system to monitor tumor growth. Transplanted tumor tissue samples were taken for hematoxylin and eosin (HE) staining, and the expression of VEGF, HSP90, HIF-1α, and MMP9 was evaluated via reverse transcription-quantitative PCR or immunohistochemistry. The results revealed that the breast tumor-bearing nude mouse model was successfully established, as evidenced by a stable expression of luciferase. Curcumin inhibited the growth of tumors without causing significant weight loss in mice. Furthermore, additive inhibition was demonstrated when curcumin was administered in combination with Glu-GNPs and irradiation. Tumor bioluminescence intensity was decreased in the model group following curcumin, Glu-GNPs, and irradiation treatment. HE staining demonstrated that transplanted tumors were malignant, with necrotic tissue exhibited centrally. It was concluded that curcumin administered in combination with Glu-GNPs and X-ray irradiation could reduce the protein expression of VEGF, HSP90, HIF-1α, and MMP9 in tumor tissue when compared with the model group. Curcumin and Glu-GNPs administered with X-ray irradiation significantly inhibited tumor growth and induced radiosensitivity, which may be associated with the inhibition of angiogenesis in tumor tissue.

RNA-Binding Proteins CLK1 and POP7 as Biomarkers for Diagnosis and Prognosis of Esophageal Squamous Cell Carcinoma

The abnormality of RNA-binding proteins (RBPs) is closely related to the tumorigenesis and development of esophageal squamous cell carcinoma (ESCC), and has been an area of interest for research recently. In this study, 162 tumors and 11 normal samples are obtained from The Cancer Genome Atlas database, among which 218 differentially expressed RBPs are screened. Finally, a prognostic model including seven RBPs (CLK1, DDX39A, EEF2, ELAC1, NKRF, POP7, and SMN1) is established. Further analysis reveals that the overall survival (OS) rate of the high-risk group is lower than that of the low-risk group. The area under the receiver operating characteristic (ROC) curve (AUC) of the training group and testing group is significant (AUCs of 3 years are 0.815 and 0.694, respectively, AUCs of 5 years are 0.737 and 0.725, respectively). In addition, a comprehensive analysis of seven identified RBPs shows that most RBPs are related to OS in patients with ESCC, among which EEF2 and ELCA1 are differentially expressed at the protein level of ESCC and control tissues. CLK1 and POP7 expressions in esophageal cancer tumor samples are undertaken using the tissue microarray, and show that CLK1 mRNA levels are relatively lower, and POP7 mRNA levels are higher compared with non-cancerous esophageal tissues. Survival analysis reveals that a higher expression of CLK1 predicts a significant worse prognosis, and a lower expression of POP7 predicts a worse prognosis in esophageal cancer. These results suggest that CLK1 may promote tumor progression, and POP7 may hinder the development of esophageal cancer. In addition, gene set enrichment analysis reveals that abnormal biological processes related to ribosomes and abnormalities in classic tumor signaling pathways such as TGF-β are important driving forces for the occurrence and development of ESCC. Our results provide new insights into the pathogenesis of ESCC, and seven RBPs have potential application value in the clinical prognosis prediction of ESCC.

Identification of prognostic hypoxia-related genes signature on the tumor microenvironment in esophageal cancer

BACKGROUND

Hypoxia is a crucial factor in the development of esophageal cancer. The relationship between hypoxia and immune status in the esophageal cancer microenvironment is becoming increasingly important in clinical practice. This study aims to clarify and investigate the possible connection between immunotherapy and hypoxia in esophageal cancer.

METHODS

The Cancer Genome Atlas databases are used to find two types of esophageal cancer cases. Cox regressions analyses are used to screen genes for hypoxia-related traits. After that, the genetic signature is validated by survival analysis and the construction of ROC curves. GSEA is used to compare differences in enrichment in the two groups and is followed by the CIBERSORT tool to investigate a potentially relevant correlation between immune cells and gene signatures.

RESULTS

We found that the esophageal adenocarcinoma hypoxia model contains 3 genes (PGK1, PGM1, SLC2A3), and the esophageal squamous cell carcinoma hypoxia model contains 2 genes (EGFR, ATF3). The findings demonstrated that the survival rate of patients in the high-risk group is lower than in the lower-risk group. Furthermore, we find that three kinds of immune cells (memory activated CD4+ T cells, activated mast cells, and M2 macrophages) have a marked infiltration in the tissues of patients in the high-risk group. Moreover, we find that PD-L1 and CD244 are highly expressed in high-risk groups.

CONCLUSIONS

Our data demonstrate that oxygen deprivation is correlated with prognosis and the incidence of immune cell infiltration in patients with both types of esophageal cancer, which provides an immunological perspective for the development of personalized therapy.

Key radioresistance regulation models and marker genes identified by integrated transcriptome analysis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy that is endemic to China and Southeast Asia. Radiotherapy is the usual treatment, however, radioresistance remains a major reason for failure. This study aimed to find key radioresistance regulation models and marker genes of NPC and clarify the mechanism of NPC radioresistance by RNA sequencing and bioinformatics analysis of the differences in gene expression profiles between radioresistant and radiosensitive NPC tissues. A total of 21 NPC biopsy specimens with different radiosensitivity were analyzed by RNA sequencing. Differentially expressed genes in RNA sequencing data were identified using R software. The differentially expressed gene data derived from RNA sequencing as well as prior knowledge in the form of pathway databases were integrated to find sub‐networks of related genes. The data of RNA sequencing with the GSE48501 data from the GEO database were combined to further search for more reliable genes associated with radioresistance of NPC. Survival analyses using the Kaplan–Meier method based on the expression of the genes were conducted to facilitate the understanding of the clinical significance of the differentially expressed genes. RT‐qPCR was performed to validate the expression levels of the differentially expressed genes. We identified 1182 differentially expressed genes between radioresistant and radiosensitive NPC tissue samples. Compared to the radiosensitive group, 22 genes were significantly upregulated and 1160 genes were downregulated in the radioresistant group. In addition, 10 major NPC radiation resistance network models were identified through integration analysis with known NPC radiation resistance‐associated genes and mechanisms. Furthermore, we identified three core genes, DOCK4, MCM9, and POPDC3 among 12 common downregulated genes in the two datasets, which were validated by RT‐qPCR. The findings of this study provide new clues for clarifying the mechanism of NPC radioresistance, and further experimental studies of these core genes are warranted.

High Expression of Citron Kinase Contributes to the Development of Esophageal Squamous Cell Carcinoma

Objective

This study aimed to investigate the role and potential regulatory mechanism of citron kinase (CIT) in esophageal squamous cell carcinoma (ESCC).

Methods

Citron kinase (CIT) expression in ESCC tissues was analyzed based on the microarray dataset GSE20347, and CIT expression in ESCC cell lines was analyzed. Eca-109 cells were lentivirally transfected with shRNA-CIT (LV-shCIT) to knock down CIT, followed by investigation of cell proliferation and apoptosis. Nude mouse xenograft experiments were performed to evaluate the tumorigenicity of CIT-knockdown Eca-109 cells. Microarray analysis of Eca-109 cells transfected with LV-shCIT or LV-shNC and subsequent Ingenuity Pathway Analysis (IPA) were performed to identify CIT-related differentially expressed genes (DEGs) and signaling pathways. Furthermore, the expression of key DEGs was validated using the clinical samples of ESCC.

Results

Citron kinase (CIT) was highly expressed in ESCC tissues and cell lines. Knockdown of CIT suppressed Eca-109 cell proliferation and promoted apoptosis in vitro. Moreover, CIT knockdown significantly reduced tumorigenicity of Eca-109 cells in vivo. Microarray and IPA analysis showed that signaling by the Rho family GTPases pathway was significantly activated, and CIT intrinsically interacted with the protein kinase AMP-activated catalytic subunit alpha 1 (PRKAA1), sequestosome 1 (SQSTM1), and interleukin 6 (IL6). Notably, the expression levels of PRKAA1 and SQSTM1 were upregulated in ESCC tissues, while the IL6 expression was downregulated.

Conclusion

Our findings confirm that CIT functions as an oncogene in ESCC. CIT may contribute to ESCC development by upregulating PRKAA1 and SQSTM1 as well as downregulating IL6. Citron kinase may serve as a promising therapeutic target for ESCC.

A Mesoscale Computational Model for Microvascular Oxygen Transfer

We address a mathematical model for oxygen transfer in the microcirculation. The model includes blood flow and hematocrit transport coupled with the interstitial flow, oxygen transport in the blood and the tissue, including capillary-tissue exchange effects. Moreover, the model is suited to handle arbitrarily complex vascular geometries. The purpose of this study is the validation of the model with respect to classical solutions and the further demonstration of its adequacy to describe the heterogeneity of oxygenation in the tissue microenvironment. Finally, we discuss the importance of these effects in the treatment of cancer using radiotherapy.

Multifunctional Graphdiyne-Cerium Oxide Nanozymes Facilitate MicroRNA Delivery and Attenuate Tumor Hypoxia for Highly Efficient Radiotherapy of Esophageal Cancer

Radioresistance is an important challenge for clinical treatments. The main causes of radioresistance include hypoxia in the tumor microenvironment, the antioxidant system within cancer cells, and the upregulation of DNA repair proteins. Here, a multiple radiosensitization strategy of high-Z-element-based radiation enhancement is designed, attenuating hypoxia and microRNA therapy. The novel 2D graphdiyne (GDY) can firmly anchor and disperse CeO₂ nanoparticles to form GDY-CeO₂ nanocomposites, which exhibit superior catalase-mimic activity in decomposing H₂ O₂ to O₂ to significantly alleviate tumor hypoxia, promote radiation-induced DNA damage, and ultimately inhibit tumor growth in vivo. The miR181a-2-3p (miR181a) serum levels in patients are predictive of the response to preoperative radiotherapy in locally advanced esophageal squamous cell carcinoma (ESCC) and facilitate personalized treatment. Moreover, miR181a can act as a radiosensitizer by directly targeting RAD17 and regulating the Chk2 pathway. Subsequently, the GDY-CeO₂ nanocomposites with miR181a are conjugated with the iRGD-grafted polyoxyethylene glycol (short for nano-miR181a), which can increase the stability, efficiently deliver miR181a to tumor, and exhibit low toxicity. Notably, nano-miR181a can overcome radioresistance and enhance therapeutic efficacy both in a subcutaneous tumor model and human-patient-derived xenograft models. Overall, this GDY-CeO₂ nanozyme and miR181a-based multisensitized radiotherapy strategy provides a promising therapeutic approach for ESCC.

FAT3 Mutation Is Associated With Tumor Mutation Burden and Poor Prognosis in Esophageal Cancer

Objective

To explore the mutated genes in esophageal cancer (ESCA), and evaluate its relationship with tumor mutation burden (TMB) and prognosis of ESCA, and analyze the advantages of FAT3 as a potential prognostic marker in ESCA.

Methods

The somatic mutation landscape was analyzed according to ESCA samples from the TCGA and ICGC database. The differences of TMB between mutant type and wild type of frequently mutated genes were compared by Mann-Whitney U test. The association of gene mutations with prognosis was analyzed by Kaplan-Meier method. The relative abundance of 22 tumor-infiltrating lymphocyte subsets in ESCA was calculated by CIBERSORT algorithm.

Results

FAT3 was a high frequency mutation in both TCGA and ICGC samples from the somatic mutation landscape. Then, the mutation type of FAT3 had significantly higher TMB in patients with ESCA compared the wild type (P<0.05). Meanwhile, the prognosis of FAT3 mutation type was significantly worse in patients with ESCA(P<0.05), and the FAT3 mutation status might be an independent factor for prognosis of patients with ESCA (HR: 1.262-5.922, P=0.011). The GSEA analysis revealed the potential mechanism of FAT3 mutation on the occurrence and development of ESCA. Finally, naive B cells were significantly enriched in FAT3 mutation samples of the ESCA microenvironment (P<0.05).

Conclusions

FAT3 mutation is related to TMB and poor prognosis in ESCA. FAT3 mutation may be a prognostic marker of ESCA, and reveal the potential mechanism of FAT3 mutation on ESCA.

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.

Hypoxic tumour cell-derived exosomal miR-340-5p promotes radioresistance of oesophageal squamous cell carcinoma via KLF10

Background

Radiotherapy resistance is a major obstacle in the treatment of oesophageal squamous cell carcinoma (OSCC). Hypoxia is a critical cause of radioresistance. However, the communication between hypoxic cells and aerobic cells via exosomes during the transfer of radiation resistance remains unclear.

Methods

Exo-miR-340-5p levels were analysed by RNA-seq and qRT-PCR. We co-cultured OSCC cells with isolated normoxic and hypoxic exosomes to study their impact on radiosensitivity. We used a specific exo-miR-340-5p mimic and knock-down retrovirus to explore the role of this miRNA in the transfer of radioresistance from hypoxic to normoxic cells. Dual-luciferase reporter and RIP assays were used to verify KLF10 as a putative target of miR-340-5p. Several in vitro assays were conducted and xenograft models were established to investigate the effect of exo-miR-340-5p on OSCC radiosensitivity. The plasma exo-miR-340-5p levels in OSCC patients were analysed to study the clinical value of this parameter.

Results

Hypoxic exosomes alleviated radiation-induced apoptosis and accelerated DNA damage repair. miR-340-5p was highly expressed in hypoxic exosomes and was transferred into normoxic cells, where it induced radioresistance. Overexpression of miR-340-5p in normoxic OSCC cells mimicked the radioresistance of cells co-cultured with hypoxic exosomes. Knockdown of miR-340-5p in hypoxic exosomes reversed the radioresistance effect, indicating that exo-miR-340-5p is critical for hypoxic EV-transferred radioresistance. KLF10 was identified as the direct target of miR-340-5p. Moreover, metformin was found to increase the expression of KLF10 and enhance the radiosensitivity of OSCC. Higher levels of miR-340-5p in the plasma exosomes from OSCC patients are related to a poorer radiotherapy response and prognosis.

Conclusions

Hypoxic tumour cell-derived exosomal miR-340-5p confers radioresistance in OSCC by targeting KLF10/UVRAG, suggesting that miR-340-5p could be a potential biomarker and therapeutic target for the enhancement of radiosensitivity in OSCC. Metformin can increase KLF10 expression, which ameliorates the radioresistance induced by exo-miR-340-5p transfer. Therefore, metformin could be further investigated as a therapeutic option for the treatment of OSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01834-9.

Metabolic Regulation of Epigenetic Modifications and Cell Differentiation in Cancer

Simple Summary

Cancer cells change their metabolism to support a chaotic and uncontrolled growth. In addition to meeting the metabolic needs of the cell, these changes in metabolism also affect the patterns of gene activation, changing the identity of cancer cells. As a consequence, cancer cells become more aggressive and more resistant to treatments. In this article, we present a review of the literature on the interactions between metabolism and cell identity, and we explore the mechanisms by which metabolic changes affect gene regulation. This is important because recent therapies under active investigation target both metabolism and gene regulation. The interactions of these new therapies with existing chemotherapies are not known and need to be investigated.

Abstract

Metabolic reprogramming is a hallmark of cancer, with consistent rewiring of glucose, glutamine, and mitochondrial metabolism. While these metabolic alterations are adequate to meet the metabolic needs of cell growth and proliferation, the changes in critical metabolites have also consequences for the regulation of the cell differentiation state. Cancer evolution is characterized by progression towards a poorly differentiated, stem-like phenotype, and epigenetic modulation of the chromatin structure is an important prerequisite for the maintenance of an undifferentiated state by repression of lineage-specific genes. Epigenetic modifiers depend on intermediates of cellular metabolism both as substrates and as co-factors. Therefore, the metabolic reprogramming that occurs in cancer likely plays an important role in the process of the de-differentiation characteristic of the neoplastic process. Here, we review the epigenetic consequences of metabolic reprogramming in cancer, with particular focus on the role of mitochondrial intermediates and hypoxia in the regulation of cellular de-differentiation. We also discuss therapeutic implications.

Patient-derived organoids as individual patient models for chemoradiation response prediction in gastrointestinal malignancies

Chemoradiotherapy (CRT) is an important treatment modality for specific gastrointestinal (GI) cancers, as it has been shown to improve clinical outcomes. Recent developments in the neoadjuvant setting such as wait-and-see strategies for rectal as well as for esophageal cancers have even proven that CRT might be an effective organ-sparing treatment. However, due to molecular heterogeneity, only a subset of patients will show a complete response to CRT, which addresses the need for an individualized treatment approach. In recent years, the demand for more physiologically relevant predictive in vitro models has fostered the development of patient-derived tumor organoids. In this review, we describe the current treatment options for patients with GI cancers who are treated with (neo)adjuvant CRT. Furthermore, we provide an in-depth discussion of the organoid technology in the context of predicting CRT response for GI cancers as well as possible challenges for clinical implementation.

Understanding the Mechanisms by Which Epigenetic Modifiers Avert Therapy Resistance in Cancer

The development of resistance to anti-cancer therapeutics remains one of the core issues preventing the improvement of survival rates in cancer. Therapy resistance can arise in a multitude of ways, including the accumulation of epigenetic alterations in cancer cells. By remodeling DNA methylation patterns or modifying histone proteins during oncogenesis, cancer cells reorient their epigenomic landscapes in order to aggressively resist anti-cancer therapy. To combat these chemoresistant effects, epigenetic modifiers such as DNA hypomethylating agents, histone deacetylase inhibitors, histone demethylase inhibitors, along with others have been used. While these modifiers have achieved moderate success when used either alone or in combination with one another, the most positive outcomes were achieved when they were used in conjunction with conventional anti-cancer therapies. Epigenome modifying drugs have succeeded in sensitizing cancer cells to anti-cancer therapy via a variety of mechanisms: disrupting pro-survival/anti-apoptotic signaling, restoring cell cycle control and preventing DNA damage repair, suppressing immune system evasion, regulating altered metabolism, disengaging pro-survival microenvironmental interactions and increasing protein expression for targeted therapies. In this review, we explore different mechanisms by which epigenetic modifiers induce sensitivity to anti-cancer therapies and encourage the further identification of the specific genes involved with sensitization to facilitate development of clinical trials.