Radioresistant Cells Research Articles

Epigenetic Targeting to Overcome Radioresistance in Head and Neck Cancer.

(1) Background: The sensitivity of head and neck squamous cell carcinoma (HNSCC) to ionizing radiation, among others, is determined by the number of cells with high clonogenic potential and stem-like features. These cellular characteristics are dynamically regulated in response to treatment and may lead to an enrichment of radioresistant cells with a cancer stem cell (CSC) phenotype. Epigenetic mechanisms, particularly DNA and histone methylation, are key regulators of gene-specific transcription and cellular plasticity. Therefore, we hypothesized that specific epigenetic targeting may prevent irradiation-induced plasticity and may sensitize HNSCC cells to radiotherapy. (2) Methods: We compared the DNA methylome and intracellular concentrations of tricarboxylic acid cycle metabolites in radioresistant FaDu and Cal33 cell lines with their parental controls, as well as aldehyde dehydrogenase (ALDH)-positive CSCs with negative controls. Moreover, we conducted a screen of a chemical library targeting enzymes involved in epigenetic regulation in combination with irradiation and analyzed the clonogenic potential, sphere formation, and DNA repair capacity to identify compounds with both radiosensitizing and CSC-targeting potential. (3) Results: We identified the histone demethylase inhibitor GSK-J1, which targets UTX (KDM6A) and JMJD3 (KDM6B), leading to increased H3K27 trimethylation, heterochromatin formation, and gene silencing. The clonogenic survival assay after siRNA-mediated knock-down of both genes radiosensitized Cal33 and SAS cell lines. Moreover, high KDM6A expression in tissue sections of patients with HNSCC was associated with improved locoregional control after primary (n = 137) and post-operative (n = 187) radio/chemotherapy. Conversely, high KDM6B expression was a prognostic factor for reduced overall survival. (4) Conclusions: Within this study, we investigated cellular and molecular mechanisms underlying irradiation-induced cellular plasticity, a key inducer of radioresistance, with a focus on epigenetic alterations. We identified UTX (KDM6A) as a putative prognostic and therapeutic target for HNSCC patients treated with radiotherapy.

PITPNC1 Suppress CD8+ T cell immune function and promote radioresistance in rectal cancer by modulating FASN/CD155

BackgroundRadioresistance is a primary factor contributing to the failure of rectal cancer treatment. Immune suppression plays a significant role in the development of radioresistance. We have investigated the potential role of phosphatidylinositol transfer protein cytoplasmic 1 (PITPNC1) in regulating immune suppression associated with radioresistance.MethodsTo elucidate the mechanisms by which PITPNC1 influences radioresistance, we established HT29, SW480, and MC38 radioresistant cell lines. The relationship between radioresistance and changes in the proportion of immune cells was verified through subcutaneous tumor models and flow cytometry. Changes in the expression levels of PITPNC1, FASN, and CD155 were determined using immunohistochemistry and western blotting techniques. The interplay between these proteins was investigated using immunofluorescence co-localization and immunoprecipitation assays. Additionally, siRNA and lentivirus-mediated gene knockdown or overexpression, as well as co-culture of tumor cells with PBMCs or CD8+ T cells and establishment of stable transgenic cell lines in vivo, were employed to validate the impact of the PITPNC1/FASN/CD155 pathway on CD8+ T cell immune function.ResultsUnder irradiation, the apoptosis rate and expression of apoptosis-related proteins in radioresistant colorectal cancer cell lines were significantly decreased, while the cell proliferation rate increased. In radioresistant tumor-bearing mice, the proportion of CD8+ T cells and IFN-γ production within immune cells decreased. Immunohistochemical analysis of human and animal tissue specimens resistant to radiotherapy showed a significant increase in the expression levels of PITPNC1, FASN, and CD155. Gene knockdown and rescue experiments demonstrated that PITPNC1 can regulate the expression of CD155 on the surface of tumor cells through FASN. In addition, co-culture experiments and in vivo tumor-bearing experiments have shown that silencing PITPNC1 can inhibit FASN/CD155, enhance CD8+ T cell immune function, promote colorectal cancer cell death, and ultimately reduce radioresistance in tumor-bearing models.ConclusionsPITPNC1 regulates the expression of CD155 through FASN, inhibits CD8+ T cell immune function, and promotes radioresistance in rectal cancer.

HJURP is recruited to double-strand break sites and facilitates DNA repair by promoting chromatin reorganization.

HJURP is overexpressed in several cancer types and strongly correlates with patient survival. However, the mechanistic basis underlying the association of HJURP with cancer aggressiveness is not well understood. HJURP promotes the loading of the histone H3 variant, CENP-A, at the centromeric chromatin, epigenetically defining the centromeres and supporting proper chromosome segregation. In addition, HJURP is associated with DNA repair but its function in this process is still scarcely explored. Here, we demonstrate that HJURP is recruited to DSBs through a mechanism requiring chromatin PARylation and promotes epigenetic alterations that favor the execution of DNA repair. Incorporation of HJURP at DSBs promotes turnover of H3K9me3 and HP1, facilitating DNA damage signaling and DSB repair. Moreover, HJURP overexpression in glioma cell lines also affected global structure of heterochromatin independently of DNA damage induction, promoting genome-wide reorganization and assisting DNA damage response. HJURP overexpression therefore extensively alters DNA damage signaling and DSB repair, and also increases radioresistance of glioma cells. Importantly, HJURP expression levels in tumors are also associated with poor response of patients to radiation. Thus, our results enlarge the understanding of HJURP involvement in DNA repair and highlight it as a promising target for the development of adjuvant therapies that sensitize tumor cells to irradiation.

TRIP13 Enhances Radioresistance of Lung Adenocarcinoma Cells through the Homologous Recombination Pathway

Radiation therapy is one of the most common treatments for non-small cell lung cancer (NSCLC). However, the insensitivity of some tumor cells to radiation is one of the major reasons for the poor efficacy of radiotherapy and the poor prognosis of patients, and exploring the underlying mechanisms behind radioresistance is the key to solving this clinical challenge. This study aimed to identify the molecules associated with radioresistance in lung adenocarcinoma (LUAD), identified thyroid hormone receptor interactor 13 (TRIP13) as the main target initially, and explored whether TRIP13 is related to radioresistance in LUAD and the specific mechanism, with the aim of providing theoretical basis and potential targets for the combination therapy of LUAD patients receiving radiotherapy in the clinic. Three datasets, GSE18842, GSE19188 and GSE33532, were selected from the Gene Expression Omnibus (GEO) database and screened for differentially expressed genes (|log FC|>1.5, P<0.05) in each of the three datasets using the R 4.1.3 software, and then Venn diagram was used to find out the differentially expressed genes common to the three datasets. The screened differential genes were then subjected to protein-protein interaction (PPI) analysis and module analysis with the help of STRING online tool and Cytoscape software, and survival prognosis analysis was performed for each gene with the help of Kaplan-Meier Plotter database, and the TRIP13 gene was identified as the main molecule for subsequent studies. Subsequently, the human LUAD cell line H292 was irradiated with multiple X-rays using a sub-lethal dose irradiation method to construct a radioresistant cell line, H292DR. The radioresistance of H292DR cells was verified using cell counting kit-8 (CCK-8) assay and clone formation assay. The expression levels of TRIP13 in H292 and H292DR cells were measured by Western blot. Small interfering RNA (siRNA) was used to silence the expression of TRIP13 in H292DR cells and Western blot assay was performed. The clone formation ability and migration ability of H292DR cells were observed after TRIP13 silencing, followed by the detection of changes in the expression levels of proteins closely related to homologous recombination, such as ataxia telangiectasia mutated (ATM) protein. Screening of multiple GEO datasets, validation of external datasets and survival analysis revealed that TRIP13 was highly expressed in LUAD and was associated with poor prognosis in LUAD patients who had received radiation therapy. And the results of gene set enrichment analysis (GSEA) of TRIP13 suggested that TRIP13 might be closely associated with LUAD radioresistance by promoting homologous recombination repair after radiation therapy. Experimentally, TRIP13 expression was found to be upregulated in H292DR, and silencing of TRIP13 was able to increase the sensitivity of H292DR cells to radiation. TRIP13 is associated with poor prognosis in LUAD patients treated with radiation, possibly by promoting a homologous recombination repair pathway to mediate resistance of LUAD cells to radiation.

SIRT7 sustains tumor development and radioresistance by repressing endoplasmic reticulum stress-induced apoptosis in cutaneous melanoma

Cutaneous melanoma is one of the most malignant human tumors and possesses strong resistance to radiotherapy. However, the mechanisms contribute to such radioresistance of melanoma is unclear. In this study, SIRT7 is identified to be higher-expressed in melanoma and positively correlated with melanoma staging. Under ionizing radiation (IR)-treatment condition, loss of SIRT7 compromised the survivability of melanoma cells showed by decreased proliferation, colony formation, migration, but enhancing apoptosis. Transcriptomic sequencing analysis indicated the apoptosis induced after SIRT7 knockdown is tightly related with the induction of endoplasmic reticulum stress (ER stress) by IR treatment. Loss of SIRT7 enhanced EIF2α acetylation and activated its phosphorylation to induce the expression of ER stress proteins including DDIT3, XBP1 and GRP78, among which DDIT3 is responsible for apoptosis induction. SIRT7 depletion enriched ER stress-activated transcription factor ATF4 at the promoter region of DDIT3 gene to transactivate its expression and induces apoptotic cascade in both mock- and IR-treatment conditions. Consistently, SIRT7 is highly upregulated in radioresistant melanoma cell strain and still modulates the ER-stress responsive genes to maintain the homeostasis of melanoma. Collectively, SIRT7 negatively regulates ER stress-activated apoptosis to enhance the survivability of melanoma cells in both non-IR- and IR-treatment conditions. Our study highlights the role of SIRT7 in repressing ER stress and the following apoptosis to sustain tumor development and mediate radioresistance in melanoma, which may suggest a novel intervention target for melanoma therapy.

Hypoxia Modulates Radiosensitivity and Response to Different Radiation Qualities in A549 Non-Small Cell Lung Cancer (NSCLC) Cells.

Hypoxia-induced radioresistance reduces the efficacy of radiotherapy for solid malignancies, including non-small cell lung cancer (NSCLC). Cellular hypoxia can confer radioresistance through cellular and tumor micro-environment adaptations. Until recently, studies evaluating radioresistance secondary to hypoxia were designed to maintain cellular hypoxia only before and during irradiation, while any handling of post-irradiated cells was carried out in standard oxic conditions due to the unavailability of hypoxia workstations. This limited the possibility of simulating in vivo or clinical conditions in vitro. The presence of molecular oxygen is more important for the radiotoxicity of low-linear energy transfer (LET) radiation (e.g., X-rays) than that of high-LET carbon (12C) ions. The mechanisms responsible for 12C ions' potential to overcome hypoxia-induced radioresistance are currently not fully understood. Therefore, the radioresistance of hypoxic A549 NSCLC cells following exposure to X-rays or 12C ions was investigated along with cell cycle progression and gene expression by maintaining hypoxia before, during and after irradiation. A549 cells were incubated under normoxia (20% O2) or hypoxia (1% O2) for 48 h and then irradiated with X-rays (200 kV) or 12C ions (35 MeV/n, LET ~75 keV/µm). Cell survival was evaluated using colony-forming ability (CFA) assays immediately or 24 h after irradiation (late plating). DNA double-strand breaks (DSBs) were analyzed using γH2AX immunofluorescence microscopy. Cell cycle progression was determined by flow cytometry of 4',6-diamidino-2-phenylindole-stained cells. The global transcription profile post-irradiation was evaluated by RNA sequencing. When hypoxia was maintained before, during and after irradiation, hypoxia-induced radioresistance was observed only in late plating CFA experiments. The killing efficiency of 12C ions was much higher than that of X-rays. Cell survival under hypoxia was affected more strongly by the timepoint of plating in the case of X-rays compared to 12C ions. Cell cycle arrest following irradiation under hypoxia was less pronounced but more prolonged. DSB induction and resolution following irradiation were not significantly different under normoxia and hypoxia. Gene expression response to irradiation primarily comprised cell cycle regulation for both radiation qualities and oxygen conditions. Several PI3K target genes involved in cell migration and cell motility were differentially upregulated in hypoxic cells. Hypoxia-induced radioresistance may be linked to altered cell cycle response to irradiation and PI3K-mediated changes in cell motility and migration in A549 cells rather than less DNA damage or faster repair.

AMPK-mediated CD47 H3K4 methylation promotes phagocytosis evasion of glioma stem cells post-radiotherapy

Radiotherapy alters the tumor microenvironment and reprograms cellular metabolism. Transition of tumor cell phenotypes contributes to post-radiotherapy tumor recurrence. Low radiosensitivity of glioma stem cells is one of the reasons for radiotherapy failure. Here, we found that radiotherapy resulted in a higher proportion of infiltration of inflammatory macrophages in glioma non-stem cell grafts compared with that in glioma stem cell-transplanted tumors in a mouse model, where immunosuppressive macrophages dominated in the tumor microenvironment. In radioresistant glioma stem cells, ionizing radiation upregulated CD47 expression by AMP-activated protein kinase (AMPK), resulting in the inhibition of phagocytosis and the promotion of M2-like polarization in macrophages. Ionizing radiation promoted H3K4 methylation on CD47 promotor by downregulating KDM5A. Hyper-phosphorylated retinoblastoma protein RB maintained its dissociation status with KDM5A following AMPK activation, which inhibited the demethylated function of KDM5A. In contrast, in radiosensitive glioma non-stem cells, RB S807/S811 hypo-phosphorylation contributed to the binding of RB with KDM5A, which suppressed H3K4 methylation on CD47 promotor. In addition, ionizing radiation promoted H3K27 acetylation on CD47 promotor by HDAC7 in glioma stem cells. These data suggested that glioma stem cells reprogrammed the tumor immune microenvironment by epigenetic editing to escape macrophage phagocytosis after ionizing radiation. Targeting CD47 might be a potential strategy to sensitize glioblastoma to radiotherapy.

Germline specific genes increase DNA double-strand break repair and radioresistance in lung adenocarcinoma cells

In principle, germline cells possess the capability to transmit a nearly unaltered set of genetic material to infinite future generations, whereas somatic cells are limited by strict growth constraints necessary to assure an organism’s physical structure and eventual mortality. As the potential to replicate indefinitely is a key feature of cancer, we hypothesized that the activation of a “germline program” in somatic cells can contribute to oncogenesis. Our group recently described over one thousand germline specific genes that can be ectopically expressed in cancer, yet how germline specific processes contribute to the malignant properties of cancer is poorly understood. We here show that the expression of germ cell/cancer (GC) genes correlates with malignancy in lung adenocarcinoma (LUAD). We found that LUAD cells expressing more GC genes can repair DNA double strand breaks more rapidly, show higher rates of proliferation and are more resistant to ionizing radiation, compared to LUAD cells that express fewer GC genes. In particular, we identified the HORMA domain protein regulator TRIP13 to be predominantly responsible for this malignant phenotype, and that TRIP13 inhibition or expression levels affect the response to ionizing radiation and subsequent DNA repair. Our results demonstrate that GC genes are viable targets in oncology, as they induce increased radiation resistance and increased propagation in cancer cells. Because their expression is normally restricted to germline cells, we anticipate that GC gene directed therapeutic options will effectively target cancer, with limited side effects besides (temporary) infertility.

Biomimetic Nanoplatform for Dual-Targeted Clearance of Activated and Senescent Cancer-Associated Fibroblasts to Improve Radiation Resistance in Breast Cancer.

Radiation resistance in breast cancer resulting in residual lesions or recurrence is a significant cause to radiotherapy failure. Cancer-associated fibroblasts (CAFs) and radiotherapy-induced senescent CAFs can further lead to radiation resistance and tumor immunosuppressive microenvironment. Here, an engineering cancer-cell-biomimetic nanoplatform is constructed for dual-targeted clearance of CAFs as well as senescent CAFs. The nanoplatform is prepared by 4T1 cell membrane vesicles chimerized with FAP single-chain fragment variable as the biomimetic shell for targeting of CAFs and senescent CAFs, and PLGA nanoparticles (NPs) co-encapsulated with nintedanib and ABT-263 as the core for clearance of CAFs and senescent CAFs, which are noted as FAP-CAR-CM@PLGA-AB NPs. It is evidenced that FAP-CAR-CM@PLGA-AB NPs directly suppressed the tumor-promoting effect of senescent CAFs. It also exhibits prolonged blood circulation and enhanced tumor accumulation, dual-cleared CAFs and senescent CAFs, improved radiation resistance in both acquired and patient-derived radioresistant tumor cells, and effective antitumor effect with the tumor suppression rate of 86.7%. In addition, FAP-CAR-CM@PLGA-AB NPs reverse the tumor immunosuppressive microenvironment and enhance systemic antitumor immunity. The biomimetic system for dual-targeted clearance of CAFs and senescent CAFs provides a potential strategy for enhancing the radio-sensitization of breast cancer.

DbCRAF: a curated knowledgebase for regulation of radiation response in human cancer.

Radiation therapy (RT) is one of the primary treatment modalities of cancer, with 40-60% of cancer patients benefiting from RT during their treatment course. The intrinsic radiosensitivity or acquired radioresistance of tumor cells would affect the response to RT and clinical outcomes in patients. Thus, mining the regulatory mechanisms in tumor radiosensitivity or radioresistance that have been verified by biological experiments and computational analysis methods will enhance the overall understanding of RT. Here, we describe a comprehensive database dbCRAF (http://dbCRAF.xialab.info/) to document and annotate the factors (1,677 genes, 49 proteins and 612 radiosensitizers) linked with radiation response, including radiosensitivity, radioresistance in cancer cells and prognosis in cancer patients receiving RT. On the one hand, dbCRAF enables researchers to directly access knowledge for regulation of radiation response in human cancer buried in the vast literature. On the other hand, dbCRAF provides four flexible modules to analyze and visualize the functional relationship between these factors and clinical outcome, KEGG pathway and target genes. In conclusion, dbCRAF serves as a valuable resource for elucidating the regulatory mechanisms of radiation response in human cancers as well as for the improvement of RT options.

The extracellular matrix component perlecan/HSPG2 regulates radioresistance in prostate cancer cells.

Radiotherapy of prostate cancer (PC) can lead to the acquisition of radioresistance through molecular mechanisms that involve, in part, cell adhesion-mediated signaling. To define these mechanisms, we employed a DU145 PC model to conduct a comparative mass spectrometry-based proteomic analysis of the purified integrin nexus, i.e., the cell-matrix junction where integrins bridge assembled extracellular matrix (matrisome components) to adhesion signaling complexes (adhesome components). When parental and radioresistant cells were compared, the expression of integrins was not changed, but cell radioresistance was associated with extensive matrix remodeling and changes in the complement of adhesion signaling proteins. Out of 72 proteins differentially expressed in the parental and radioresistant cells, four proteins were selected for functional validation based on their correlation with biochemical recurrence-free survival. Perlecan/heparan sulfate proteoglycan 2 (HSPG2) and lysyl-like oxidase-like 2 (LOXL2) were upregulated, while sushi repeat-containing protein X-linked (SRPX) and laminin subunit beta 3 (LAMB3) were downregulated in radioresistant DU145 cells. Knockdown of perlecan/HSPG2 sensitized radioresistant DU145 RR cells to irradiation while the sensitivity of DU145 parental cells did not change, indicating a potential role for perlecan/HSPG2 and its associated proteins in suppressing tumor radioresistance. Validation in androgen-sensitive parental and radioresistant LNCaP cells further supported perlecan/HSPG2 as a regulator of cell radiosensitivity. These findings extend our understanding of the interplay between extracellular matrix remodeling and PC radioresistance and signpost perlecan/HSPG2 as a potential therapeutic target and biomarker for PC.

The mir-199b-5p encapsulated in adipocyte-derived exosomes mediates radioresistance of colorectal cancer cells by targeting JAG1

Radiotherapy is a key treatment option for colorectal cancer, but its efficacy varies among patients. Our previous studies suggested that adipose tissue may confer the radioresistance of several abdominal tumors, such as pancreatic cancer, biliary cancer, and others. In the present work, the effects of adipocytes in regulating the radiosensitivity of colorectal cancer are explored for the first time. It was found that colony formation was increased and radiation-induced apoptosis decreased in colorectal cancer cells HCT8 and HCT116 co-cultured with adipocytes, which verified the mediation of adipocyte-driven radioresistance in colorectal cancer in vitro. Next, the colorectal cancer cells were incubated with adipocyte-derived exosomes, and a perceptible reduction in radiosensitivity was detected. Furthermore, to investigate the possible mechanisms involved, the exosomes were isolated, the encapsulated microRNAs were extracted and analyzed by small RNA sequencing. Based on bioinformatics analysis and qRT-PCR verification, miR-199b-5p was chosen for functional annotation. It was shown that miR-199b-5p expression was significantly upregulated after 6 Gy irradiation, and overexpressed miR-199b-5p significantly suppressed the radiosensitivity of HCT8 and HCT116 cells. In addition, jagged canonical Notch ligand 1(JAG1) was identified as the target gene of miR-199b-5p by using bioinformatics prediction and dual luciferase reporter gene assay. It was demonstrated that JAG1 conferred the radioresistance of colorectal cancer cells both in vivo and in vitro. Taken together, the present study demonstrates that adipocytes trigger the radioresistance of colorectal cancer cells, probably by targeting JAG1 through an adipocyte-derived exosomal miR-199b-5p.

NRF2 promotes radiation resistance by cooperating with TOPBP1 to activate the ATR-CHK1 signaling pathway.

Background: Radiation resistance is the main limitation of the application of radiotherapy. Ionizing radiation (IR) kills cancer cells mainly by causing DNA damage, particularly double-strand breaks (DSBs). Radioresistant cancer cells have developed the robust capability of DNA damage repair to survive IR. Nuclear factor erythroid 2-related factor 2 (NRF2) has been correlated with radiation resistance. We previously reported a novel function of NRF2 as an ATR activator in response to DSBs. However, little is known about the mechanism that how NRF2 regulates DNA damage repair and radiation resistance. Methods: The TCGA database and tissue microarray were used to analyze the correlation between NRF2 and the prognosis of lung cancer patients. The radioresistant lung cancer cells were constructed, and the role of NRF2 in radiation resistance was explored by in vivo and in vitro experiments. Immunoprecipitation, immunofluorescence and extraction of chromatin fractions were used to explore the underlying mechanisms. Results: In this study, the TCGA database and clinical lung cancer samples showed that high expression of NRF2 was associated with poor prognosis in lung cancer patients. We established radioresistant lung cancer cells expressing NRF2 at high levels, which showed increased antioxidant and DNA repair abilities. In addition, we found that NRF2 can be involved in the DNA damage response independently of its antioxidant function. Mechanistically, we demonstrated that NRF2 promoted the phosphorylation of replication protein A 32 (RPA32), and DNA topoisomerase 2-binding protein 1 (TOPBP1) was recruited to DSB sites in an NRF2-dependent manner. Conclusion: This study explored the novel role of NRF2 in promoting radiation resistance by cooperating with RPA32 and TOPBP1 to activate the ATR-CHK1 signaling pathway. In addition, the findings of this study not only provide novel insights into the molecular mechanisms underlying the radiation resistance of lung cancer cells but also validate NRF2 as a potential target for radiotherapy.

Влияние ионизирующего излучения на активность антиоксидантных ферментов штамма Escherichia coli «ПЛ-6» при многократном облучении

The article presents the analysis of enzymatic activity of Escherichia coli “PL-6” cells following multiple gamma irradiation with increasing doses. For irradiation the stationary gamma ray unit “Researcher” (Co-60) with the dose rate of 36.7 Gy/min was used. Radiation doses to the bacterial cells increased from 3.5 to 10 kGy in 0.5 kGy increment, and from 10 to 30 kGy in 5 kGy increment. Unirradiated suspended bacterial cells were used as control. The irradiated cells enzymatic activity was estimated with the spectrophotometric method on the "MultiSkan Go" device (Thermo Fisher Scientific, Finland). The results of the study demonstrate the increase in the E. coli ”PL-6” cells radioresistance caused by gamma irradiation of the cells with gradually increased doses. Exposure of the bacteria to a higher gamma radiation dose caused decrease in the number of viable cells from 10Е+9 CFU/ml in the control culture sample to 10Е+2 CFU/ml after irradiation at a dose of 30 kGy. The most radiation-resistant cells were selected from cells undergone successive multiple irradiation with constantly increasing dose of ionizing radiation. The enzymes of the antioxidant system in irradiated cells exhibit increased specific activity as compared to the enzymes in control, unirradiated, cells. The activity of enzymes increases with an increase in the radiation dose. Catalase activity increased after multiple irradiation by 5 times and peroxidase activity increased by 4 times. To compare the results in the groups, the Student's t-test was applied at p&lt;0.05.

Novel radiation and targeted therapy combinations for improving rectal cancer outcomes.

Neoadjuvant radiotherapy (RT) is commonly used as standard treatment for rectal cancer. However, response rates are variable and survival outcomes remain poor, highlighting the need to develop new therapeutic strategies. Research is focused on identifying novel methods for sensitising rectal tumours to RT to enhance responses and improve patient outcomes. This can be achieved through harnessing tumour promoting effects of radiation or preventing development of radio-resistance in cancer cells. Many of the approaches being investigated involve targeting the recently published new dimensions of cancer hallmarks. This review article will discuss key radiation and targeted therapy combination strategies being investigated in the rectal cancer setting, with a focus on exploitation of mechanisms which target the hallmarks of cancer.

β-Elemene promotes ferroptosis and reverses radioresistance in gastric cancer by inhibiting the OTUB1-GPX4 interaction.

β-Elemene, derived from Curcuma zedoaria (Wenyujin), is clinically recognized for inducing apoptosis, inhibiting cell cycle progression, and reversing chemotherapy resistance in various cancers. However, its effects on radioresistant gastric cancer (GC) remain unclear. In this study, radioresistant GC cell lines (MKN45/IR and AGS/IR) were established via multiple low-dose radiations. The impact of β-elemene on radiosensitivity was assessed using CCK-8 and clonogenic assays, with ferroptosis markers such as ROS, MDA, and Fe2+ levels measured. Additionally, the influence of β-elemene on GPX4 and its interaction with OTUB1 was examined through qRT-PCR, Western blot, immunofluorescence, co-immunoprecipitation, and in vivo studies. Our findings indicate that β-elemene reverses radioresistance in GC cells and significantly inhibits cell growth when combined with radiotherapy. β-Elemene treatment elevated ROS, MDA, and Fe2+ levels, enhancing ferroptosis, which was confirmed by Ferrostatin-1 and Deferoxamine inhibition studies. Mechanistic analysis revealed that β-elemene disrupts the OTUB1-GPX4 interaction, leading to increased GPX4 ubiquitination and degradation, thus promoting ferroptosis. In vivo studies further demonstrated that β-elemene combined with radiotherapy significantly suppressed tumor growth compared to radiotherapy alone. These results suggest that β-elemene effectively modulates radioresistance in GC by targeting the GPX4 pathway and inducing ferroptosis. This highlights its potential as a therapeutic adjunct in radiotherapy for resistant GC cases.

Role of lncRNA LUCAT1 in Promoting Radioresistance of Lung Cancer Cells through Sponging with miR-199a-5p

Role of lncRNA LUCAT1 in Promoting Radioresistance of Lung Cancer Cells through Sponging with miR-199a-5p

LncRNA HOTAIR promotes DNA damage repair and radioresistance by targeting ATR in colorectal cancer.

Long non-coding RNAs (lncRNAs) have been implicated in cancer progression and drug resistance development. Moreover, there is evidence that lncRNA HOX transcript antisense intergenic RNA (HOTAIR) is involved in colorectal cancer (CRC) progression. The present study aimed to examine the functional role of lncRNA HOTAIR in conferring radiotherapy resistance in CRC cells, as well as the underlying mechanism. The relative expression levels of HOTAIR were examined in 70 pairs of CRC tumor and para-cancerous tissues, as well as in radiosensitive and radioresistant samples. The correlations between HOTAIR expression levels and clinical features of patients with CRC were assessed using the Chi-square test. Functional assays such as cell proliferation, colony formation and apoptosis assays were conducted to determine the radiosensitivity in CRC cells with HOTAIR silencing after treatment with different doses of radiation. RNA pull-down assay and fluorescence in situ hybridization (FISH) were used to determine the interaction between HOTAIR and DNA damage response mediator ataxia-telangiectasia mutated- and Rad3-related (ATR). HOTAIR was significantly upregulated in CRC tumor tissues, especially in radioresistant tumor samples. The elevated expression of HOTAIR was correlated with more advanced histological grades, distance metastasis and the poor prognosis in patients with CRC. Silencing HOTAIR suppressed the proliferation and promoted apoptosis and radiosensitivity in CRC cells. HOTAIR knockdown also inhibited the tumorigenesis of CRC cells and enhanced the sensitivity to radiotherapy in a mouse xenograft model. Moreover, the data showed that HOTAIR could interact with ATR to regulate the DNA damage repair signaling pathway. Silencing HOTAIR impaired the ATR-ATR interacting protein (ATRIP) complex and signaling in cell cycle progression. Collectively, the present results indicate that lncRNA HOTAIR facilitates the DNA damage response pathway and promotes radioresistance in CRC cells by targeting ATR.

TRAF4 regulates ubiquitination-modulated survivin turnover and confers radioresistance.

Nasopharyngeal carcinoma (NPC) is the most common cancer originating in the nasopharynx. Despite continuous improvement in treatment strategies, recurrence or persistence of cancer after radiotherapy is still inevitable, highlighting the need to identify therapeutic resistance factors and develop effective methods for NPC treatment. Herein, we found that TRAF4 is overexpressed in NPC cells and tissues. Knockdown TRAF4 significantly increased the radiosensitivity of NPC cells, possibly by inhibiting the Akt/Wee1/CDK1 axis, thereby suppressing survivin phosphorylation and promoting its degradation by FBXL7. TRAF4 is positively correlated with p-Akt and survivin in NPC tissues. High protein levels of TRAF4 were observed in acquired radioresistant NPC cells, and knockdown of TRAF4 overcomes radioresistant in vitro and the xenograft mouse model. Altogether, our study highlights the TRAF4-survivin axis as a potential therapeutic target for radiosensitization in NPC.

Enhancement of cytotoxic effects with ALA-PDT on treatment of radioresistant cancer cells.

Radiation therapy is a lower invasive local treatment than surgery and is selected as a primary treatment for solid tumors. However, when some cancer cells obtain radiotherapy tolerance, cytotoxicity of radiotherapy for cancer cells is attenuated. Photodynamic therapy (PDT) is a non-invasive cancer therapy combined with photosensitizers and laser irradiation with an appropriate wavelength. PDT is carried out for recurrent esophageal cancer patients after radiation chemotherapy and is an effective treatment for radiation-resistant tumors. However, it is not clear why PDT is effective against radioresistant cancers. In this study, we attempted to clear this mechanism using X-ray resistant cancer cells. X-ray resistant cells produce high amounts of mitochondria-derived ROS, which enhanced nuclear translocation of NF-κB, resulting in increased NO production. Moreover, the expression of PEPT1 that imports 5-aminolevulinic acid, the precursor of photosensitizers, was upregulated in X-ray resistant cancer cells. This was accompanied by an increase in intracellular 5-aminolevulinic acid-derived porphyrin accumulation, resulting in enhancement of PDT-induced cytotoxicity. Therefore, effective accumulation of photosensitizers induced by ROS and NO may achieve PDT after radiation therapy and PDT could be a promising treatment for radioresistant cancer cells.