Radioresistant Cell Line Research Articles

The reversibility of cancer radioresistance: a novel potential way to identify factors contributing to tumor radioresistance.

To understand the molecular mechanisms responsible for radioresistance in cancer cells, we previously established clinically relevant radioresistant (CRR) cell lines from several human cancer cell lines. These CRR cells proliferate even under exposure to 2Gy/day of X-rays for more than 30days, which is a standard protocol for tumor radiotherapy. CRR cells received 2Gy/day of X-rays to maintain their radioresistance (maintenance irradiation; MI). Interestingly, CRR cells that did not receive MI for more than a year lost their radioresistance, indicating that radiation-induced radioresistance is reversible. We designated these CRR-NoIR cells. Karyotyping of the parental and CRR cells revealed that the chromosomal composition of CRR cells is quite different from that of the parental cells. However, CRR and CRR-NoIR cells were more similar compared with the parental cells because CRR cells repair X-ray-induced DNA damage with higher fidelity. To identify the factor(s) involved in tumor radioresistance, previously published studies including ours have compared radioresistant cells to parental cells. In this review, we conclude that a comparison between CRR and CRR-NoIR cells, rather than parental cells, is the best way to identify factors involved in tumor radioresistance.

MiR-7-5p/KLF4 signaling inhibits stemness and radioresistance in colorectal cancer

Resistance to radiotherapy remains a major unmet clinical obstacle in the treatment of locally advanced rectal cancer. Cancer stem cells (CSCs) are considered to mediate tumor development and radioresistance. However, the role of CSCs in regulating resistance to radiotherapy in colorectal cancer (CRC) remains largely unknown. We established two radioresistant CRC cell lines, HCT116-R and RKO-R, using fractionated irradiation. Analysis using miRNA sequencing and quantitative real-time PCR confirmed lower levels of miR-7-5p in both of the radioresistant cells compared to their parental cells. Subsequently, we validated that miR-7-5p expression was decreased in cancerous tissues from radiotherapy-resistant rectal cancer patients. The Cancer Genome Atlas (TCGA) database analyses revealed that low miR-7-5p expression was significantly correlated with poor prognosis in CRC patients. Overexpression of miR-7-5p led to a rescue of radioresistance and an increase in radiation-induced apoptosis, and attenuated the stem cell-like properties in HCT116-R and RKO-R cells. Conversely, knocking down miR-7-5p in parental HCT116 and RKO cells suppressed the sensitivity to radiation treatment and enhance cancer cell stemness. Stemness-associated transcription factor KLF4 was demonstrated as a target of miR-7-5p. Rescue experiments revealed that miR-7-5p/KLF4 axis could induce radiosensitivity by regulating CSCs in colorectal cancer cells. Furthermore, we used CRC tumor tissues which exhibited resistance to neoadjuvant radiotherapy to establish a patient-derived xenograft (PDX) mouse model. Tail vein injection of magnetic nanoparticles carrying miR-7-5p mimics into the PDX mice significantly inhibited tumor growth with or without irradiation treatment in vivo. Our current studies not only demonstrate an anti-cancer function of miR-7-5p in regulating CSC properties and radiosensitivity in colorectal cancer, but also provide a novel potential strategy for delaying or reverse radiation resistance in preoperative radiotherapy of CRC patients.

MiR-139 Affects Radioresistance in Esophageal Cancer by Targeting the PDK1/AKT/Cyclin D1 Signaling Pathway.

We explored the mechanism by which miR-139 modulates radioresistance of esophageal cancer (EC). The radioresistant cell line KYSE150R was obtained from the parental KYSE150 cell line by fractionated irradiation (15×2 Gy; total dose of 30 Gy). The cell cycle was assessed by flow cytometry. A gene profiling study was conducted to detect the expression of genes related to the radioresistance of EC. In the KYSE150R line, flow cytometry revealed increased number of G1-phase cells and decreased number of G2-phase cells; the expression of miR-139 increased. Knockdown of miR-139 decreased radioresistance and changed the distribution of cell cycle phases in KYSE150R cells. Western blotting showed that miR-139 knockdown increased the expression levels of cyclin D1, p-AKT, and PDK1. However, PDK1 inhibitor GSK2334470 reversed this effect for p-AKT and cyclin D1 expression. A luciferase reporter assay indicated that miR-139 directly bound to the PDK1 mRNA 3'-UTR. Analysis of the clinical data from 110 patients with EC showed an association of miR-139 expression with the TNM stage and the effect of therapy. MiR-139 expression significantly correlated with EC and progression-free survival. In conclusion, miR-139 enhances the radiosensitivity of EC by regulating the cell cycle through the PDK1/Akt/Cyclin D1 signaling pathway.

Prognostic risk analysis related to radioresistance genes in colorectal cancer.

Radiotherapy (RT) is one of the most important treatments for patients with colorectal cancer (CRC). Radioresistance is the crucial cause of poor therapeutic outcomes in colorectal cancer. However, the underlying mechanism of radioresistance in colorectal cancer is still poorly defined. Herein we established a radioresistant colorectal cancer cell line and performed transcriptomics analyses to search for the underlying genes that contribute to radioresistance and investigate its association with the prognosis of CRC patients. The radioresistant cell line was developed from the parental HCT116 cell by a stepwise increased dose of irradiation. Differential gene analysis was performed using cellular transcriptome data to identify genes associated with radioresistance, from which extracellular matrix (ECM) and cell adhesion-related genes were screened. Survival data from a CRC cohort in the TCGA database were used for further model gene screening and validation. The correlation between the risk score model and tumor microenvironment, clinical phenotype, drug treatment sensitivity, and tumor mutation status were also investigated. A total of 493 different expression genes were identified from the radioresistant and wild-type cell line, of which 94 genes were associated with ECM and cell adhesion-related genes. The five model genes TNFRSF13C, CD36, ANGPTL4, LAMB3, and SERPINA1 were identified for CRC radioresistance via screening using the best model. A ROC curve indicated that the AUC of the resulting prognostic model (based on the 5-gene risk score and other clinical parameters, including age, sex, and tumor stages) was 0.79, 0.77, and 0.78 at 1, 2, and 3 years, respectively. The calibration curve showed high agreement between the risk score prediction and actual survival probability. The immune microenvironment, drug treatment sensitivity, and tumor mutation status significantly differed between the high- and low-risk groups. The risk score model built with five radioresistance genes in this study, including TNFRSF13C, CD36, ANGPTL4, LAMB3, and SERPINA1, showed favorable performance in prognosis prediction after radiotherapy for CRC.

FOXM1-Mediated Regulation of Reactive Oxygen Species and Radioresistance in Oral Squamous Cell Carcinoma Cells

Radioresistance is a major obstacle to the successful treatment of oral squamous cell carcinoma (OSCC). To help overcome this issue, we have developed clinically relevant radioresistant (CRR) cell lines generated by irradiating parental cells over time, which are useful for OSCC research. In the present study, we conducted gene expression analysis using CRR cells and their parental lines to investigate the regulation of radioresistance in OSCC cells. Based on gene expression changes over time in CRR cells and parental lines subjected to irradiation, forkhead box M1 (FOXM1) was selected for further analysis in terms of its expression in OSCC cell lines, including CRR cell lines and clinical specimens. We suppressed or upregulated the expression of FOXM1 in OSCC cell lines, including CRR cell lines, and examined radiosensitivity, DNA damage, and cell viability under various conditions. The molecular network regulating radiotolerance was also investigated, especially the redox pathway, and the radiosensitizing effect of FOXM1 inhibitors was examined as a potential therapeutic application. We found that FOXM1 was not expressed in normal human keratinocytes but was expressed in several OSCC cell lines. The expression of FOXM1 was upregulated in CRR cells compared with that detected in the parental cell lines. In a xenograft model and clinical specimens, FOXM1 expression was upregulated in cells that survived irradiation. FOXM1-specific small interfering RNA (siRNA) treatment increased radiosensitivity, whereas FOXM1 overexpression decreased radiosensitivity, and DNA damage was altered significantly under both conditions, as well as the levels of redox-related molecules and reactive oxygen species production. Treatment with the FOXM1 inhibitor thiostrepton had a radiosensitizing effect and overcame radiotolerance in CRR cells. According to these results, the FOXM1-mediated regulation of reactive oxygen species could be a novel therapeutic target for the treatment of radioresistant OSCC; thus, treatment strategies targeting this axis might overcome radioresistance in this disease.

HSP90B1-mediated plasma membrane localization of GLUT1 promotes radioresistance of glioblastomas.

Ionizing radiation is a popular and effective treatment option for glioblastoma (GBM). However, resistance to radiation therapy inevitably occurs during treatment. It is urgent to investigate the mechanisms of radioresistance in GBM and to find ways to improve radiosensitivity. Here, we found that heat shock protein 90 beta family member 1 (HSP90B1) was significantly upregulated in radioresistant GBM cell lines. More importantly, HSP90B1 promoted the localization of glucose transporter type 1, a key rate-limiting factor of glycolysis, on the plasma membrane, which in turn enhanced glycolytic activity and subsequently tumor growth and radioresistance of GBM cells. These findings imply that targeting HSP90B1 may effectively improve the efficacy of radiotherapy for GBM patients, a potential new approach to the treatment of glioblastoma.

LTF Induces Radioresistance by Promoting Autophagy and Forms an AMPK/SP2/NEAT1/miR-214-5p Feedback Loop in Lung Squamous Cell Carcinoma.

Radiotherapy is the most predominant treatment strategy for lung squamous cell carcinoma (LUSC) patients, but radioresistance is the major obstacle to therapy effectiveness. The mechanisms and regulators of LUSC radioresistance remain unclear. Here, lactotransferrin (LTF) is found to be significantly upregulated in radioresistant LUSC cell lines (H226R and H1703R) and clinical samples and promotes radioresistance of LUSC both in vitro and in vivo. Comprehensive enrichment analyses suggested that LTF potentially modulates autophagy in LUSC. Interestingly, the level of autophagy was raised in the radioresistant cells, and suppression of autophagy sensitized LUSC to irradiation. Functional experiments showed that LTF deficiency inhibits cellular autophagy through the AMPK pathway, ultimately leading to radiosensitization. Mechanistically, LTF can directly interact with AMPK to facilitate its phosphorylation and activate autophagy signaling. Moreover, NEAT1 functions as a ceRNA that targets miR-214-5p resulting in an increased LTF expression. Intriguingly, SP2, a transcription factor regulated by AMPK, induced NEAT1 expression by directly binding to its promoter region and thus forming a LTF/AMPK/SP2/NEAT1/miR-214-5p feedback loop. Our work reveals for the first time that LTF induces radioresistance by promoting autophagy and enhancing its self-expression via forming a positive feedback loop, suggesting that LTF is an appealing radiosensitization target for treating LUSC.

MiR-4443 promotes radiation resistance of esophageal squamous cell carcinoma via targeting PTPRJ

BackgroundRadiotherapy is one of the main treatments for esophageal squamous cell carcinoma (ESCC), but its efficacy is limited by radioresistance. MicroRNAs play a crucial role in posttranscriptional regulation, which is linked to the cancer response to radiation.MethodsWe successfully established a radioresistant cell line model by using fractionated irradiation. qRT-PCR was adopted to detect the expression of miR-4443 in human normal esophageal cell lines, tumor cells, and radioresistant cells. Next, CCK-8, colony formation, apoptosis, and cell cycle assays were used to assess the biological effect of miR-4443. Weighted gene coexpression network analysis (WGCNA) was performed to identify potential radiosensitivity-related genes. Additionally, we predicted the probable targets of the miRNA using bioinformatic methods and confirmed them using Western blot.ResultsmiR-4443 was significantly upregulated in radioresistant ESCC cells. Enhancement of miR-4443 further decreased the radiosensitivity of ESCC cells, while inhibition of miR-4443 increased the radiosensitivity of ESCC cells. Notably, miR-4443 modulated radiosensitivity by influencing DNA damage repair, apoptosis, and G2 cycle arrest. By using WGCNA and experimental validation, we identified PTPRJ as a key target for miRNA-4443 to regulate radiosensitivity. The effects of miR-4443 overexpression or inhibition could be reversed by increasing or decreasing PTPRJ expression.ConclusionIn this study, miR-4443 is found to promote radiotherapy resistance in ESCC cells by regulating PTPRJ expression, which provides a new perspective and clue to alleviate radioresistance.

YTHDF3 mediates HNF1α regulation of cervical cancer radio-resistance by promoting RAD51D translation in an m6A-dependent manner.

Radiotherapy, as an important primary treatment, has effectively improved the survival of patients with cervical cancer (CC). Some patients, however, do not benefit optimally from radiotherapy because of radio-resistance. Therefore, identifying radio-resistance biomarkers and unravelling the underlying mechanisms is of critical importance for these patients. In the present study, we found significant upregulation of hepatocyte nuclear factor 1-alpha (HNF1α) expression in radio-resistant cervical cancer tissues and cell lines. Depletion of HNF1α reduced and overexpression of HNF1α promoted the resistance of CC cells to irradiation invitro and invivo. HNF1α positively regulated DNA repair protein RAD51 homologue 4 (RAD51D) at the protein level but not at the mRNA level. Mechanistically, upregulation of HNF1α enhanced YTH domain-containing family protein 3 (YTHDF3) transcription, which in turn promoted RAD51D mRNA N6 -methyladenosine (m6A) modification. YTHDF3 mediates HNF1α regulation of cervical cancer radio-resistance by promoting RAD51D translation in an m6A-dependent manner. The HFN1α/YTHDF3/RAD51D regulatory axis was found to play a critical role in conferring radio-resistance of CC cells. In conclusion, dysregulation of the HFN1α/YTHDF3/RAD51D axis may promote the radio-resistance of CC cells. Blocking this pathway may provide therapeutic benefits against CC radio-resistance.

AZGP1 Up-Regulation is a Potential Target for Andrographolide Reversing Radioresistance of Colorectal Cancer.

Radiation resistance is a challenge that limits the therapeutic benefit of colorectal cancer (CRC) treatment, but the mechanism underlying CRC radiation resistance remains unclear. Andrographolide shows a broad-spectrum anti-tumor effect in various malignancies, including CRC, its effect and how it functions in CRC initiation, and radiation have not been established. This study aimed to explore the mechanism of CRC radiation resistance and the potential mechanisms of andrographolide on CRC radiation. Two acquired radioresistant cell lines were established and high throughput sequencing was employed to screen out the differentially expressed genes. The expression of AZGP1, which was upregulated in the acquired radioresistant tissues, was verified by microarray data recomputing. The common targets of andrographolide, CRC initiation, and radiation resistance were obtained, and the corresponding functional enrichment and pathway analysis were performed. The interaction between AZGP1 and andrographolide was investigated using molecular docking. AZGP1 was upregulated in both the radioresistant cell model and microarray data. Moreover, AZGP1 was upregulated in cancerous colorectal tissue and displayed a tendency toward elevated expression in patients with an unfavorable prognosis. AZGP1 was identified as the common target of andrographolide, colorectal cancer initiation, and radiotherapy resistance. Ultimately, the protein structure of AZGP1 proved to be closely intertwined with the crystal texture of andrographolide. AZGP1 is recognized as a crucial factor for both CRC initiation and radioresistance. Andrographolide may affect the radioresistance of CRC via the targeting of AZGP1. Thus, the combination of andrographolide and AZGP1 intervention might be a promising strategy for improving the treatment benefit of CRC radiotherapy.

Discovery of a Novel Driver of Radioresistance in Pancreatic Cancer (PC) Using Genome-Wide RNA-Seq

<h3>Purpose/Objective(s)</h3> Discovery of genetic drivers of radioresistance in PC is critical for developing novel therapeutic strategies to combine with radiation in this radioresistant disease. In this study, we used genome-wide RNA-seq to identify genes upregulated in radioresistant (RR) generated PC cell lines and discovered the Inhibitor of DNA Binding 1 (ID1) gene as a promising radiosensitizing target. <h3>Materials/Methods</h3> RR PC cell lines MIA PaCa-2 and PANC-1 were generated by delivering daily ionizing irradiation (IR) (2 Gy/day) <i>in vitro</i> over two weeks (total 20 Gy) followed by standard clonogenic assays to calculate the dose enhancement ratio (DER) following one week from the end of IR. Parental and RR cell lines were submitted for RNA-seq analysis to identify differentially expressed genes. The Limma R package was used to calculate differential expression among genes. Log2 fold change values were calculated for each sample compared to control. Genes with an absolute fold change > 1 were considered significant. Knockdown of target genes via small interfering RNA (siRNA) was confirmed through immunoblotting. Luciferase expressing RR PANC-1 and MIA PaCa-2 with or without shRNA stable knockdown of ID1 were implanted orthotopically in the pancreas of athymic nude mice, and tumors were treated with external beam radiation using a Small Animal Radiation Research Platform to a dose of 20 Gy in 5 daily fractions. Tumor growth was measured weekly via bioluminescence. <h3>Results</h3> Following exposure to two weeks of 2 Gy daily IR <i>in vitro</i>, the two PC cell lines showed significantly greater clonogenic cell survival than parental cell lines (DER 0.4 and 0.5), indicating enhanced RR in these cells. RNA-seq analysis comparing parental and RR cell lines found upregulated seven genes (TNS4, ZDHHC8P1, APLNR, AQP3, SPP1, ID1, ID2) and seven genes downregulated (PTX3, ITGB2, EPS8L1, ALDH1L2, KCNT2, ARHGAP9, IFI16) in both RR cell lines. Western blotting confirmed either increased or decreased expression of these 14 genes in the RR cell lines compared to their parental. siRNA knockdown of each of the seven most significant upregulated genes in the RR MIA PaCa-2 and PANC-1 cells revealed ID1 as the most potent radiosensitizer in the RR cell lines (DER 1.5 and 1.6, respectively). ID1 protein expression was higher in 6 different human PC cell lines than both non-malignant pancreatic and intestinal cell lines. Orthotopic RR tumors with stable knockdown of ID1 showed significantly decreased tumor growth following <i>in vivo IR</i> than the wild-type ID1 tumors (2.5-fold decrease, p<0.001). After the last dose of IR, expression of the DNA damage marker yH2aX in tumors was significantly higher in the ID1 knockdown tumors compared to controls indicating reduced DNA repair in tumors deficient in ID1. <h3>Conclusion</h3> Our analysis indicates a novel role of ID1 in PC radioresistance. Targeting ID1 prior to IR is a promising strategy to overcome the RR of PC, and pre-clinical studies using ID1 inhibitors are ongoing.

Alternating Radiation Fractionations Overcome Radioresistance in Patient-Derived Glioblastoma Cells

<h3>Purpose/Objective(s)</h3> Historically, radiotherapy fractions for Glioblastoma (GBM) are delivered in equal doses over a given number of days, though this regimen has not changed in the past century and does not accommodate for the development of radioresistance. Using mathematical oncological simulations, we propose that ramping up dose can overcome radioresistance in patient-derived xenograft (PDX) GBM cells more sufficiently than the same dose delivered in equal fractions. <h3>Materials/Methods</h3> We generated a radiation-sensitive (JX14P) and -resistant (JX14P-RT) PDX GBM cell line by implanting primary tumors into the flank of athymic nude mice. To achieve radioresistance, we treated these mice with 6 fractions of 2 Gy of radiation over 14 days. In silico simulations utilizing the radiosensitivity parameters based on the linear-quadratic model and JX14P and JX14P-RT doubling time, suggested a total regimen of 16 Gy, with an average of 4 Gy/fx, delivered in fractions of 1 Gy, 3 Gy, 5 Gy, or 7 Gy (Ramp-Up, "RU") would result in a smaller surviving fraction than the equivalent total dose of 4 Gy, 4 Gy, 4 Gy, 4 Gy (Equal Dosing, "ED") in JX14P and JX14PRT. The equivalent opposite regimen of 7 Gy, 5 Gy, 3 Gy, and 1 Gy (Ramp-Down, "RD") was also investigated. 5000 cells were plated in DMEM-F12 media with B27 supplement and 20 ng/ml EGF and FGF and irradiated every three days. Viability was determined using CellTiterGlo, nine days after the final dose of radiation. This experiment was done in triplicates. Statistical analysis of viability between the different regimens was assessed using a two-way ANOVA with a multiple comparisons Tukey test. <h3>Results</h3> Our preliminary results indicate that delivering a total dose of 16 Gy, alternating radiation fractionations every three days of 1 Gy, 3 Gy, 5 Gy, or 7 Gy, enhances cytotoxicity in both radiation-sensitive and radiation-resistant PDX models when compared to no treatment and fractions of equal dose (4 Gy) delivered in the same manner (Cell line vs luminescence, <i>P</i><0.0001). <h3>Conclusion</h3> This data suggests RU and RD dosing is superior to ED in the radiosensitive cell lines ED (<i>P</i><0.0001). However, in the radioresistant cell lines, only RU was superior to ED (<i>P</i><0.0001). We are also exploring the effects of this novel treatment regimen in our radiation-sensitive and -resistant PDX GBM cell lines when co-cultured with different starting proportions. This is the first known experiment where two regimens with the same average dose per fraction and total dose results in vastly different cytotoxicity.

Targeted Proteomic Analysis of Small GTPases in Radioresistant Breast Cancer Cells.

Radiation therapy benefits more than 50% of all cancer patients and cures 40% of them, where ionizing radiation (IR) deposits energy to cells and tissues, thereby eliciting DNA damage and resulting in cell death. Small GTPases are a superfamily of proteins that play critical roles in cell signaling. Several small GTPases, including RAC1, RHOB, and RALA, were previously shown to modulate radioresistance in cancer cells. However, there is no systematic proteomic study on small GTPases that regulate radioresistance in cancer cells. Herein, we applied a high-throughput scheduled multiple-reaction monitoring (MRM) method, along with the use of synthetic stable isotope-labeled (SIL) peptides, to identify differentially expressed small GTPase proteins in two pairs of breast cancer cell lines, MDA-MB-231 and MCF7, and their corresponding radioresistant cell lines. We identified 7 commonly altered small GTPase proteins with over 1.5-fold changes in the two pairs of cell lines. We also discovered ARFRP1 as a novel regulator of radioresistance, where its downregulation promotes radioresistance in breast cancer cells. Together, this represents the first comprehensive investigation about the differential expression of the small GTPase proteome associated with the development of radioresistance in breast cancer cells. Our work also uncovered ARFRP1 as a new target for enhancing radiation sensitivity in breast cancer.

An oncolytic virus as a promising candidate for the treatment of radioresistant oral squamous cell carcinoma

We evaluated the usefulness of an oncolytic virus (Suratadenoturev; OBP-301) against radioresistant oral squamous cell carcinoma. We confirmed the expression of human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor in cell lines. Also, we examined the potential presence in a patient who has received existing therapy that is amenable to treatment with OBP-301. We evaluated: (1) the antitumor effects of OBP-301 alone and in combination with radiotherapy on radioresistant cell lines, (2) the molecular mechanism underlying the radiosensitizing effect and cell death increased by the combination therapy, and (3) the antitumor effect of the combination therapy invivo using xenograft models (a radioresistant cell line-derived xenograft in mouse and a patient-derived xenograft). Human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor were expressed in all cell lines. OBP-301 decreased the proliferative activity of these cell lines in a concentration-dependent manner, and significantly enhanced the antitumor effect of irradiation. Phosphorylated STAT3 and its downstream molecules, which correlated with apoptosis and autophagy, showed significant changes in expression after treatment with OBP-301. The combination therapy exerted a significant antitumor effect versus radiotherapy alone in both xenograft models. Combination of OBP-301 with radiotherapy exerts a synergistic effect and may represent a promising treatment for radioresistant oral squamous cell carcinoma.

FN1 promotes prognosis and radioresistance in head and neck squamous cell carcinoma: From radioresistant HNSCC cell line to integrated bioinformatics methods.

Background: Radioresistance in head and neck squamous cell carcinoma (HNSCC) patients means response failure to current treatment. In order to screen radioresistant biomarkers and mechanisms associated with HNSCC, differentially expressed genes (DEGs) associated with radioresistance in HNSCC were investigated. Methods: The HNSCC cell line with radioresistance, Hep2-R, was established and detected the radiosensitivity using MTT, colony formation assay and flow cytometry analysis. Clariom™ D chip was applied to compare DEGs between Hep2 and Hep2-R groups and build the differential gene expression profiles associated with radioresistance in HNSCC. Bioinformatic analysis were used to find biological functions and pathways that related to radioresistance in HNSCC, including cell adhesion, cytochrome P450 and drug metabolism. Gene Expression Omnibus (GEO) datasets were selected to verify DEGs between HNSCC radioresistant cells and tissues. The representation of DEGs were validated between HNSCC patients with complete response and post-operative radiation therapy failure. In addition, we evaluated the clinical prognosis of DEGs using The Cancer Genome Atlas (TCGA) database. Results: 2,360 DEGs (|Fold Change|>1.5, p < 0.05) were identified between Hep2 and Hep2-R, including 1,144 upregulated DEGs and 1,216 downregulated DEGs. They were further verified by HNSCC radioresistant cells and tissues in GEO. 13 radioresistant DEGs showed same difference in expression level between cells and tissues. By comparing 13 DEGs with HNSCC patients, upregulations of FN1, SOX4 and ETV5 were found identical with above results. Only FN1 was a prognostic indicator of HNSCC in TCGA. Conclusion: FN1 is the potential novel biomarker for predicting poor prognosis and radioresistance in HNSCC patients. Overexpression of FN1 plays an important role in the tumorigenesis, prognosis and radioresistance of HNSCC.

MicroRNA-613 Enhances Nasopharyngeal Carcinoma Cell Radiosensitivity via the DNA Methyltransferase 3B/Tissue Inhibitor of Matrix Metalloproteinase-3/Signal Transducer and Activator of Transcription-1/Forkhead Box O-1 Axis.

Nasopharyngeal carcinoma (NPC) is a common malignancy of the nasopharynx, and radioresistant represents the main obstacle in NPC treatment. Malignant transformation of normal cells is driven by genetic and epigenetic changes, which are primarily manifested as changes in miRNA levels and DNA methylation status. microRNA (miR)-613 plays an inhibitory role in several types of cancer. Herein, the current study sought to explore the roles of miR-613 in NPC cell radiosensitivity. miR-613 expression patterns in NPC tissues were detected, and its correlation with clinical indexes was analyzed. NP-69 and C666-1 cell lines were selected for cellular experimentation. Radioresistant cell line C666-1R was obtained by fractionated radiation. Cell viability, survival fraction, and apoptosis were detected by CCK-8, colony formation assay, and flow cytometry. The binding relation between miR-613 and DNMT3B was verified by dual-luciferase and RIP assays. miR-613 was lowly expressed in NPC tissues and cells, with lower expression levels in C666-1R than C666-1, and further correlated with lymph node metastasis, tumor size, and tumor metastasis. miR-613 overexpression reduced C666-1R cell viability and survival fraction and increased apoptosis, while C666-1 cells with silencing miR-613 presented the opposite trends. miR-613 targeted DNMT3B. miR-613 and DNMT3B overexpression led to enhanced C666-1R cell viability and survival fraction and decreased apoptosis. miR-613 reduced TIMP3 methylation and elevated TIMP3 protein level by inhibiting DNMT3B. miR-613 enhanced NPC radiosensitivity by inhibiting the DNMT3B/TIMP3/STAT1/FOXO1 pathway. Collectively, miR-613 inhibited DNMT3B, reduced TIMP3 methylation, and increased TIMP3 protein level, thus inhibiting the STAT1/FOXO1 pathway and enhancing the radiosensitivity of NPC cells.

CircPUM1 Knockdown Confers Radiosensitivity in Oral Squamous Cell Carcinoma by Regulating the miR-580/STAT3 Pathway.

Background: CircPUM1 acts as an oncogene in a variety of tumors, and there is no related research on oral squamous cell carcinoma. This study aimed to evaluate the clinical significance of CircPUM1 in oral squamous cell carcinoma radiotherapy. Methods: Radio-resistant cell lines were established by increasing the X-ray dose. Analysis of CircPUM1 expression in oral squamous cell carcinoma was carried out using bioinformatics tools. Cell proliferation was analyzed with CCK-8 and colony formation. Protein and gene expressions were detected by Western blotting and qPCR. RNA interference inhibits endogenous gene expression. A luciferase reporter system and immunoprecipitation were used to validate the target of CircPUM1. Result: CircPUM1 was highly expressed in OSCC. The higher the expression level of CircPUM1 in OSCC, the worse the clinical features and prognosis. Knockdown of CircPUM1 enhances the sensitivity of OSCC cells to X-rays, and expression of exogenous CircPUM1 makes OSCC cells acquire radiation resistance. The absence of CircPUM1 blocked the cells in the G0/G1 phase and triggered apoptosis. The prediction of mir-580-binding site, luciferase reporter system, and immunoprecipitation confirmed that mir-580 is the binding site of CircPUM1. In addition, STAT3 was predicted and confirmed as the binding site of mir-580. Overexpression of STAT3 partially attenuated the radiosensitivity of OSCC cells to knockdown of CircPUM1. Conclusion: CircPUM1 has the oncogene expression profile in oral squamous cell carcinoma; patients with high expression of CircPUM1 have less benefit from radiotherapy and need more frequent follow-up. In addition, CircPUM1 may be a potential therapeutic target for oral squamous cell carcinoma. The CircPUM1/mir-580/STAT3 axis has a certain effect on the radiosensitivity of OSCC. These results suggest that patients with low expression of CircPUM1 may gain more benefits.

Characterization of the mechanism of Scutellaria baicalensis on reversing radio-resistance in colorectal cancer

Scutellaria baicalensis (SB) has been shown to improve the therapeutic effects of colorectal cancer (CRC) and perform well for reversing radio-resistance in different cancers. However, its potential function and mechanism related to radio-resistance in CRC has not been explored. A radio-resistant human CRC cell line (HCT116R) was applied. A network pharmacological analysis was performed to reveal the potential mechanism of SB for reversing radio-resistance in CRC, and computational pathological analysis was applied to indicate the clinicopathological significance of the key targets. Then, our hypothesis was further verified by molecular docking. The network pharmacology analysis showed that wogonin is the key compound of SB for reversing the radio-resistance of CRC. A Kyoto Encyclopedia of Genes and Genomes analysis showed that the genes for SB that reverse radio-resistance in CRC are mainly involved in steroid hormone biosynthesis. An enrichment analysis pointed out that Sulfotransferase family 2B member 1 (SULT2B1) is a potentially vital gene. SULT2B1 was demonstrated as being highly expressed in CRC and upregulated in radio-resistant rectal tissues or cell lines. A CCK-8 and clone formation test showed that the viability and clone formation ability of HCT116R were significantly decreased by wogonin combined with radiotherapy, compared to radiotherapy alone. By contrast, flow cytometry revealed that the apoptosis of HCT116R was significantly increased when wogonin treatment combined with radiotherapy, compared with radiotherapy alone. Molecular docking verification indicated that SULT2B1 and wogonin have a good binding ability. Taken together, SULT2B1 may be the potential drug target in treating radio-resistant CRC. Wogonin may be the core compound of SB for reversing radio-resistance in CRC by targeting SULT2B1.

The effect of chromosome abnormalities on expression of SnoRNA in radioresistant and radiosensitive cell lines after irradiation.

In this paper, we have studied the role of chromosomal abnormalities in the expression of small nucleolar RNAs (snoRNAs) of radioresistant (K562) and radiosensitive (HL-60) leukemia cell line. Cells were exposed to an X-ray dose of 4 Gy. SnoRNA expression was investigated using NGS sequencing. The distribution of expressed snoRNAs on chromosomes has been found to be different for two cell lines. The most significant differences in the expression of snoRNAs were found in the K562 cell line based on the analysis of the dynamics of log2fc values. The type of clustering, the number and type of snoRNAs slightly differed in the chromosomes with trisomy and monosomy and had a pronounced difference in pairs with marker chromosomes in both cell lines. In this study, we have demonstrated that chromosomal abnormalities alter the expression of snoRNA after irradiation. Trisomies and monosomies do not have such a noticeable effect on the expression of snoRNAs as the presence of marker chromosomes.

Specific Targeting of Antiapoptotic Bcl-2 Proteins as a Radiosensitizing Approach in Solid Tumors.

Avoidance of therapy-induced apoptosis is a hallmark of acquired resistance towards radiotherapy. Thus, breaking resistance still challenges modern cancer therapy. The Bcl-2 protein family is known for its regulatory role in apoptosis signaling, making Bcl-2, Mcl-1 and Bcl-xL promising targets. This study evaluates the effects of highly specific inhibitors for Bcl-xL (WEHI-539), Bcl-2 (ABT-199) and Mcl-1 (S63845) as radiosensitizers. Covering a broad spectrum of solid tumors, Non-Small-Cell Lung Cancer (NSCLC), Head and Neck Squamous Cell Carcinoma (HNSCC) and synovial sarcoma cell lines were exposed to fractionated radiation as standard therapy with or without Bcl-2 protein inhibition. Protein expression was detected by Western blot and cell death was assessed by flow cytometry measuring apoptosis. In contrast to NSCLC, a high level of Bcl-xL and its upregulation during radiotherapy indicated radioresistance in HNSCC and synovial sarcoma. Radioresistant cell lines across all entities benefited synergistically from combined therapy with Bcl-xL inhibition and fractionated radiation. In NSCLC cell lines, Mcl-1 inhibition significantly augmented radiotherapy independent of the expression level. Our data suggest that among antiapoptotic Bcl-2 proteins, targeting Bcl-xL may break resistance to radiation in HNSCC, synovial sarcoma and NSCLC in vitro. In NSCLC, Mcl-1 might be a promising target that needs further investigation.