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 andfluorescence 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.

Role of glioma stem cells in promoting tumor chemo- and radioresistance: A systematic review of potential targeted treatments

BACKGROUND Gliomas pose a significant challenge to effective treatment despite advancements in chemotherapy and radiotherapy.Glioma stem cells(GSCs),a subset within tumors,contribute to resistance,tumor heterogeneity,and plasticity.Recent studies reveal GSCs’role in therapeutic resistance,driven by DNA repair mechanisms and dynamic transitions between cellular states.Resistance mechanisms can involve different cellular pathways,most of which have been recently reported in the literature.Despite progress,targeted therapeutic approaches lack consensus due to GSCs’high plasticity.AIM To analyze targeted therapies against GSC-mediated resistance to radio-and chemotherapy in gliomas,focusing on underlying mechanisms.METHODS A systematic search was conducted across major medical databases(PubMed,Embase,and Cochrane Library)up to September 30,2023.The search strategy utilized relevant Medical Subject Heading terms and keywords related to including“glioma stem cells”,“radiotherapy”,“chemotherapy”,“resistance”,and“targeted therapies”.Studies included in this review were publications focusing on targeted therapies against the molecular mechanism of GSC-mediated re-sistance to radiotherapy resistance(RTR).RESULTS In a comprehensive review of 66 studies on stem cell therapies for SCI,452 papers were initially identified,with 203 chosen for full-text analysis.Among them,201 were deemed eligible after excluding 168 for various reasons.The temporal breakdown of studies illustrates this trend:2005-2010(33.3%),2011-2015(36.4%),and 2016-2022(30.3%).Key GSC models,particularly U87(33.3%),U251(15.2%),and T98G(15.2%),emerge as significant in research,reflecting their representativeness of glioma characteristics.Pathway analysis indicates a focus on phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin(mTOR)(27.3%)and Notch(12.1%)pathways,suggesting their crucial roles in resistance development.Targeted molecules with mTOR(18.2%),CHK1/2(15.2%),and ATP binding cassette G2(12.1%)as frequent targets underscore their importance in overcoming GSC-mediated resistance.Various therapeutic agents,notably RNA inhibitor/short hairpin RNA(27.3%),inhibitors(e.g.,LY294002,NVP-BEZ235)(24.2%),and monoclonal antibodies(e.g.,cetuximab)(9.1%),demonstrate versatility in targeted therapies.among 20 studies(60.6%),the most common effect on the chemotherapy resistance response is a reduction in temozolomide resistance(51.5%),followed by reductions in carmustine resistance(9.1%)and doxorubicin resistance(3.0%),while resistance to RTR is reduced in 42.4%of studies.CONCLUSION GSCs play a complex role in mediating radioresistance and chemoresistance,emphasizing the necessity for precision therapies that consider the heterogeneity within the GSC population and the dynamic tumor microenvironment to enhance outcomes for glioblastoma patients.

Hypoxia-induced Autophagy Contributes to Radioresistance via c-Jun-mediated Beclin1 Expression in Lung Cancer Cells

Reduced radiosensitivity of lung cancer cells represents a pivotal obstacle in clinical oncol- ogy. The hypoxia-inducible factor （HIF）-lα plays a crucial role in radiosensitivity, but the detailed mechanisms remain elusive. A relationship has been suggested to exist between hypoxia and autophagy recently. In the current study, we studied the effect of hypoxia-induced autophagy on radioresistance in lung cancer cell lines. A549 and H1299 cells were cultured under normoxia or hypoxia, followed by ir- radiation at dosage ranging from 0 to 8 Gy. Clonogenic assay was performed to calculate surviving frac- tion. EGFP-LC3 plasmid was stably transfected into cells to monitor autopbagic processes. Western blotting was used to evaluate the protein expression levels of HIF-lα, c-Jun, phosphorylated c-Jun, Be- clin 1, LC3 and p62. The mRNA levels of Beclin 1 were detected by qRT-PCR. We found that under hypoxia, both A549 and H1299 cells were radio-resistant compared with normoxia. Hypoxia-induced elevated HIF-1α protein expression preferentially triggered autophagy, accompanied by LC3 induction, EGFP-LC3 puncta and p62 degradation. In the meantime, HIF-1α increased downstream c-Jun phos- phorylation, which in turn upregulated Beclin 1 mRNA and protein expression. The upregulation of Be- clin 1 expression, instead of HIF-1α, could be blocked by SP600125 （a specific inhibitor of c-Jun NH2- terminal kinase）, followed by suppression of autophagy. Under hypoxia, combined treatment of irradia- tion and chloroquine （a potent autophagy inhibitor） significantly decreased the survival potential of lung cancer cells in vitro and in vivo. In conclusion, hypoxia-induced autophagy through evaluating Beclinl expression may be considered as a target to reverse the radioresistance in cancer cells.

Overexpression of nuclear β-catenin in rectal adenocarcinoma is associated with radioresistance

AIM:To investigate the association between nuclearβ-catenin overexpression in rectal adenocarcinoma and radioresistance.METHODS:A retrospective analysis was conducted.The analysis involved 136 patients with locally advanced rectal adenocarcinoma who underwent shortcourse preoperative radiotherapy and radical resection.The expression ofβ-catenin in both pretreatment biopsy specimens and resected primary tumor tissues was examined by immunohistochemistry.The correlation ofβ-catenin expression with radioresistance was evaluated using the tumor regression grading(TRG)system.The relationship betweenβ-catenin expression and clinicopathological characteristics was also analyzed.Univariate and logistic multivariate regression analyses were adopted to determine the independent factors of radioresistance.RESULTS:Nuclearβ-catenin overexpression was more evident in radioresistant rectal adenocarcinoma than in radiosensitive rectal adenocarcinoma(57.6%vs 16.7%,P<0.001).Nuclearβ-catenin was overexpressed in favor of poor TRG(≤2),whereas membraneβ-catenin was expressed in favor of good TRG(≥3).Nuclearβ-catenin expression in tumor cell differentiation(P=0.018),lymph node metastasis(P=0.022),and TRG(P<0.001)showed significant differences.Univariate analyses demonstrated that radioresistance is associated with nuclearβ-catenin overexpression(P<0.001).In addition,logistic multivariate regression analysis indicated that only three factors,namely,tumor size(P<0.001),tumor cell differentiation(P<0.001),and nuclearβ-catenin overexpression(P<0.001),are associated with radioresistance.By using radioresistance as a prediction target,nuclearβ-catenin-based prediction alone achieved 83%accuracy,65%sensitivity,and88%specificity.CONCLUSION:Nuclearβ-catenin overexpression may be a valuable candidate to predict the response of rectal adenocarcinoma to preoperative radiotherapy.

Mechanisms of radioresistance in hepatocellular carcinoma

Hepatocellular carcinoma(HCC), one of the most common cancers in the world, is characterized by poor prognosis and recurrence after resection. Its prevalence is highest in developing countries, particularly where there is high incidence of hepatitis B virus infection. Several curative treatments are available for early stage HCC; however, these options are not available for advanced disease. New techniques allowing the specific delivery of high-dose radiotherapy enable their use in the treatment of HCC, which has been avoided in the past due to low hepatic tolerance for radiation. This presents a new challenge—the development of resistance to radiotherapy and subsequent disease recurrence. Recently, the mechanisms controlling radioresistance have begun to be elucidated. Understanding the molecular basis of radioresistance is key to developing new strategies with better treatment response and increased patient survival.

Constitutive Overexpression of Bcl-2, Survivin and ER Stress Chaperone GRP-78 Confers Intrinsic Radioresistance in Human Hepatocellular Carcinoma Cells: Insight into the Mechanistic Pathways Involved

We present evidence here that abundantly expressed b-catenin-triggered NF-kB-dependent upregulation of inducible nitric oxide synthase(iNOS) found in hepatoma Mahlavu cells (RT-resistant variant designated as RR-Mal), but not in Hep 3B cells (RT-sensitive variant designated as RS-3B) is a key element contribrting to the radioresisitance through the activation of two prominent radioprotective pathways. First, high iNOS expression found in RR-Mal, but not in RS-3B cells was found to perturb calcium homeostasis that triggered ER stress response leading to the overproduction of ER chaperone GRP-78 via robust generation of cleaved ATF-6a (50 kDa) subunits and their nuclear translocation. Meanwhile, both abundantly expressed NF-κB and COX-2 found in RR-Mal cells could also provoke an increased production of PGE2 resulting in robust production of Bcl-2. Interestingly, when RR-Mal cells were treated with PDTC (a NF-κB inhibitor) or celecoxib (a COX-2 inhibitor), a concentration-dependent downregulation of Bcl-2 could be demonstrated implying that Bcl-2 overexpression was indeed mediated through NF-κB/Cox-2/PGE2 pathway. Importantly, we also unveiled that siRNA-mediated silencing of survivin in RR-Mal cells could result in a concomitant downregulation of GRP-78 due to a severe inhibition of ATF-6a (50 kDa) expression. Taken together, our data demonstrate that constitutively overexpressed b-catenin/NF-κB/iNOS and NF-κB/COX-2/PGE2 pathways that overproducing GRP-78, survivin and Bcl-2 expressions are responsible for radioresistance acquisition in RR-Mal cells. Thus, both pathways could be served as potential targets for overcoming radioresistance.

3-59 Mechanism on X-ray Irradiation Suppressing Radioresistance in Non-small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) accounts for 85% of lung cancer, which is the leading cause of death in lung cancer patient. Routine treatment of NSCLC cannot effectively change the survival rate of patients, one important reason is the increased radioresistance of tumor cells after conventional radiotherapy.

Radioresistance of MnSOD and its relation with Bcl-2 and p53 mRNA expression

The molecular mechanisms of radioresistance of manganese ssuperoxide dismutase (MnSOD) was investigated in thisstudy. We assayed cell necrocis and apoptosis induced by ionizing radiation. Furthermore, the possible roles of oncogenes bc1-2and p53 mRNA expression in MnSOD gene-transfected cells were for investigated. me results showed that 10 Gy X-ray could induce the expression of bc1-2 mRNA and suppress p53 mRNA expression in sense MnSOD transfected cells, whereas Bc1-2 mRNAexpression did not change and p53 mRNA expression increased in antisense MnSOD transfected cells. It is suggested that Bc1-2 isrequired for the radioresistance of MnSOD and the status of p53 play a role in radiation-induced cell death.

Two distinct subpopulations of marginal zone B cells exhibit differential antibody-producing capacities and radioresistance

Marginal zone(MZ)B cells,which are splenic innate-like B cells that rapidly secrete antibodies(Abs)against blood-borne pathogens,are composed of heterogeneous subpopulations.Here,we showed that MZ B cells can be divided into two distinct subpopulations according to their CD80 expression levels.CD80^(high)MZ B cells exhibited greater Ab-producing,proliferative,and IL-10-secreting capacities than did CD80^(low)MZ B cells.Notably,CD80^(high)MZ B cells survived 2-Gy whole-body irradiation,whereas CD80^(low)MZ B cells were depleted by irradiation and then repleted with one month after irradiation.Depletion of CD80^(low)MZ B cells led to accelerated development of type II collagen(CII)-induced arthritis upon immunization with bovine CII.CD80^(high)MZ B cells exhibited higher expression of genes involved in proliferation,plasma cell differentiation,and the antioxidant response.CD80^(high)MZ B cells expressed more autoreactive B cell receptors(BCRs)that recognized double-stranded DNA or CII,expressed more immunoglobulin heavy chain sequences with shorter complementarity-determining region 3 sequences,and included more clonotypes with no N-nucleotides or with B-1a BCR sequences than CD80^(low)MZ B cells.Adoptive transfer experiments showed that CD21^(+)CD23^(+)transitional 2 MZ precursors preferentially generated CD80^(low)MZ B cells and that a proportion of CD80^(low)MZ B cells were converted into CD80^(high)MZ B cells;in contrast,CD80^(high)MZ B cells stably remained CD80^(high)MZ B cells.In summary,MZ B cells can be divided into two subpopulations according to their CD80 expression levels,Ab-producing capacity,radioresistance,and autoreactivity,and these findings may suggest a hierarchical composition of MZ B cells with differential stability and BCR specificity.

Regulator of G protein signaling 20 contributes to radioresistance of non-small cell lung cancer cells by suppressing pyroptosis

Objective:To investigate the potential role of the regulator of G protein signaling 20(RGS20)in radioresistance of non-small cell lung cancer(NSCLC).Methods:A total of 35 lung adenocarcinoma(LUAD)patients from The Cancer Genome Atlas(TCGA),who un-derwent radiotherapy,were enrolled and divided into radiosensitive(n=16)and radioresistant(n=19)groups based on clinical prognosis.The expression and prognosis of RGS20 were analyzed by Gene Expression Profiling Interactive Analysis(GEPIA)database.A radioresistant cell line(A549R)was constructed by irradiating A549 cells with 6 Gy X-rays for 10 fractions.Cell survival was measured by colony formation assay.The regulatory effect of RGS20 on pyroptosis were verified by LDH release and Western blot assay,and the underlying mech-anism was investigated by transfecting RGS20 siRNA and applying a GSDMD inhibitor.Results:A total of 2,181 differentially expressed genes(DEGs)were identified by analyzing the data of radio-sensitive and radioresistant individuals from the TCGA-LUAD dataset.These DEGs were enriched in G alpha(z)signalling events analyzed by Reactome database.RGS20 exhibited significant upregulation among the DEGs,and its higher expression predicted poor prognosis in LUAD patients.In vitro,the expression of RGS20 protein was increased by irradiation in A549 cells,whereas it remained at much high levels in A549R cells regardless of irradiation.After irradiation,the expressions of pyroptosis-related proteins were significantly increased in A549 cells(P<0.05),with no significant changes were observed in A549R cells.Treatment with LDC7559 significantly reduced LDH release(P<0.01)and improved the survival rate of irradiated A549 cells(P<0.01).Furthermore,knockdown of RGS20 gene in A549R cells significantly increased LDH release(P<0.001)and enhanced radiosensitivity(P<0.01),while LDC7559 administration reversed LDH release(P<0.01)and radiation-induced cell death increased by siRGS20(P<0.05).Meantime,the increased expression level of GSDMD-NT was observed in A549 and A549R cells transfected with siRGS20(P<0.05).Conclusion:RGS20 contributes to the radioresistance of NSCLC cells,which might be a potential target for NSCLC radiotherapy.

RIG-I immunotherapy overcomes radioresistance in p53-positive malignant melanoma

Radiotherapy induces DNA damage,resulting in cell cycle arrest and activation of cell-intrinsic death pathways.However,the radioresistance of some tumour entities such as malignant melanoma limits its clinical application.The innate immune sensing receptor retinoic acid-inducible gene I(RIG-I)is ubiquitously expressed and upon activation triggers an immunogenic form of cell death in a variety of tumour cell types including melanoma.To date,the potential of RIG-I ligands to overcome radioresistance of tumour cells has not been investigated.Here,we demonstrate that RIG-I activation enhanced the extent and immunogenicity of irradiation-induced tumour cell death in human and murine melanoma cells in vitro and improved survival in the murine B16 melanoma model in vivo.Transcriptome analysis pointed to a central role for p53,which was confirmed using p53^(-/-)B16 cells.In vivo,the additional effect of RIG-I in combination with irradiation on tumour growth was absent in mice carrying p53^(-/-)B16 tumours,while the antitumoural response to RIG-I stimulation alone was maintained.Our results identify p53 as a pivotal checkpoint that is triggered by RIG-I resulting in enhanced irradiation-induced tumour cell death.Thus,the combined administration of RIG-I ligands and radiotherapy is a promising approach to treating radioresistant tumours with a functional p53 pathway,such as melanoma.

Transcriptional pausing induced by ionizing radiation enables the acquisition of radioresistance in nasopharyngeal carcinoma

Lesions on the DNA template can impact transcription via distinct regulatory pathways.Ionizing radiation(IR)as the mainstay modality for many malignancies elicits most of the cytotoxicity by inducing a variety of DNA damages in the genome.How the IR treatment alters the transcription cycle and whether it contributes to the development of radioresistance remain poorly understood.Here,we report an increase in the paused RNA polymerase II(RNAPII),as indicated by the phosphorylation at serine 5 residue of its C-terminal domain,in recurrent nasopharyngeal carcinoma(NPC)patient samples after IR treatment and cultured NPC cells developing IR resistance.Reducing the pool of paused RNAPII by either inhibiting TFIIH-associated CDK7 or stimulating the positive transcription elongation factor b,a CDK9-CycT1 heterodimer,attenuates IR resistance of NPC cells.Interestingly,the poly(ADP-ribosyl)ation of CycT1,which disrupts its phase separation,is elevated in the IR-resistant cells.Mutation of the major poly(ADP-ribosyl)ation sites of CycT1 decreases RNAPII pausing and restores IR sensitivity.Genome-wide chromatin immunoprecipitation followed by sequencing analyses reveal that several genes involved in radiation response and cell cycle control are subject to the regulation imposed by the paused RNAPII.Particularly,we identify the NIMA-related kinase NEK7 under such regulation as a new radioresistancefactor,whose downregulation results in the increased chromosome instability,enabling the development of IR resistance.Overall,our results highlight a novel link between the alteration in the transcription cycle and the acquisition of IR resistance,opening up new opportunities to increase the efficacy of radiotherapy and thwart radioresistance in NpC.

PI3K/AKT/mTOR pathway,hypoxia,and glucose metabolism:Potential targets to overcome radioresistance in small cell lung cancer

Small cell lung cancer(SCLC)is a highly aggressive tumor type for which limited therapeutic progress has been made.Platinum-based chemotherapy with or without thoracic radiotherapy remains the backbone of treatment,but most patients with SCLC acquire therapeutic resistance.Given the need for more effective therapies,better elucidation of the molecular pathogenesis of SCLC is imperative.The phosphoinositide 3-kinase(PI3K)/protein kinase B(AKT)/mammalian target of rapamycin(mTOR)pathway is frequently activated in SCLC and strongly associated with resistance to ionizing radiation in many solid tumors.This pathway is an important regulator of cancer cell glucose metabolism,and its activation probably effects radioresistance by influencing bioenergetic processes in SCLC.Glucose metabolism has three main branches-aerobic glycolysis,oxidative phosphorylation,and the pentose phosphate pathway-involved in radioresistance.The interaction between the PI3K/AKT/mTOR pathway and glucose metabolism is largely mediated by hypoxia-inducible factor 1(HIF-1)signaling.The PI3K/AKT/mTOR pathway also influences glucose metabolism through other mechanisms to participate in radioresistance,including inhibiting the ubiquitination of rate-limiting enzymes of the pentose phosphate pathway.This review summarizes our understanding of links among the PI3K/AKT/mTOR pathway,hypoxia,and glucose metabolism in SCLC radioresistance and highlights promising research directions to promote cancer cell death and improve the clinical outcome of patients with this devastating disease.

Polarization of tumor-associated macrophages by TLR7/8 conjugated radiosensitive peptide hydrogel for overcoming tumor radioresistance

Radioresistance reduces the antitumor efficiency of radiotherapy and further restricts its clinical application,which is mainly caused by the aggravation of immunosuppressive tumor microenvironment(ITM).Especially tumor-associated macrophages(TAMs)usually display the tumor-promoting M2 phenotype during high-dose fractional radiotherapy mediating radiotherapy resistance.Herein,the toll like receptor agonist TLR7/8a was conjugated with radiosensitive peptide hydrogel(Smac-TLR7/8 hydrogel)to regulate TAMs repolarization from M2 type into M1 type,thus modulating the ITM and overcoming the radioresistance.The Smac-TLR7/8 hydrogel was fabricated through self-assembly with nanofibrous morphology,porous structure and excellent biocompatibility.Uponγ-ray radiation,Smac-TLR7/8 hydrogel effectively polarized the macrophages into M1 type.Notably,combined with radiotherapy,TAMs repolarization regulated by Smac-TLR7/8 hydrogel could increase tumor necrosis factor secretion,activate antitumor immune response and effectively inhibit tumor growth.Moreover,TAMs repolarization rebuilt the ITM and elicited the immunogenic phenotypes in solid tumors,thus enhanced the PD1-blockade efficacy through increasing tumor infiltrating lymphocytes(TILs)and decreasing Treg cells in two different immune activity tumor mice models.Overall,this study substantiated that recruiting and repolarization of TAMs were critical in eliciting antitumor immune response and overcoming radioresistance,thus improving the efficacy of radiotherapy and immunotherapy.

Ring-like nucleoid does not play a key role in radioresistance of Deinococcus radiodurans

The conclusion based on transmission electron microscopy, "the tightly packed ring-like nucleoid of the Deinococcus radiodurans R1 is a key to radioresistance", has instigated lots of debates. In this study, according to the previous research of PprI’s crucial role in radioresistance of D. radiodurans, we have attempted to examine and compare the nucleoid morphology differences among wild-type D. ra-diodurans R1 strain, pprI function-deficient mutant (YR1), and pprI function-complementary strains (YR1001, YR1002, and YR1004) before and after exposure to ionizing irradiation. Fluorescence mi-croscopy images indicate: (1) the majority of nucleoid structures in radioresistant strain R1 cells ex-hibit the tightly packed ring-like morphology, while the pprI function-deficient mutant YR1 cells carrying predominate ring-like structure represent high sensitivity to irradiation; (2) as an extreme radioresistant strain similar to wild-type R1, pprI completely function-complementary strain YR1001 almost displays the loose and irregular nucleoid morphologies. On the other hand, another radioresistant pprI partly function-complementary strain YR1002’s nucleiods exhibit about 60% ring-like structure; (3) a PprI C-terminal deletion strain YR1004 consisting of approximately 60% of ring-like nucleoid is very sensi-tive to radiation. Therefore, our present experiments do not support the conclusion that the ring-like nucleoid of D. radiodurans does play a key role in radioresistance.

HIF-1 signaling: A key orchestrator of cancer radioresistance

Hypoxia is a big roadblock for cancer radiotherapy,in which the hypoxia-inducible factor(HIF-1)creates a microenvironment and cancer cells’intrinsic signaling networks conferring radioresistance to cancers.HIF-1 is a heterodimeric transcription factor HIF-1α/HIF-1β,that regulates the transcription of a broad range of downstream genes possessing an E-box-like hypoxia response element(HRE).The expression of HIF-1αis oxygensensitive while HIF-1βis constitutively expressed.In addition to hypoxia,ionizing radiation can also induce the expression of HIF-1α.The HIF-1 modulates a set of signaling pathways to cause profound effects on the response of cancer to radiotherapy,including radiation-induced DNA damage response(DDR),vasculogenesis and glucose metabolism reprograming,epithelial mesenchymal transition(EMT),etc.In this review,our aim is to summarize the current knowledge about the role and the related signal pathways of HIF-1 in association with the resistance of cancers to radiotherapy.Targeting HIF-1 and its signal pathways is a promising strategy for sensitization of cancers to radiotherapy.

HBXIP contributes to radioresistance through NF-κB-mediated expression of XIAP in breast cancer

Objective:Hepatitis B X-interacting protein(HBXIP)plays an important role in breast tumorigenesis,tumor growth and metastasis,but its functional contribution in radioresistance remains poorly understood.As radiotherapy served as an essential adjuvant treatment,uncovering the role of HBXIP as well as its downstream molecular XIAP in radioresistance could benefit for the development of individual therapy strategy.Methods:Immunohistochemistry of 42 breast cancer tissue samples and Western blot analysis of proteins from MCF-7 and MDA-MB-231 cells exposed to fractioned doses(γ-rays)were used to identify the expression of HBXIP/XIAP in breast cancer.To verify the radioresistance effects and potential mechanism,the cells were treated with designed pCMV and siRNA of targeting genes,and then measured with MTT assay,clonogenic survival assay and flow cytometry.Furthermore,a subcutaneous xenotransplanted tumor model of breast cancer was established in nude mice to validate the radioresistization effect of HBXIP in vivo.Results:HBXIP and XIAP expression levels in breast cancer tissues were positively correlated with chemoradiotherapy resistance of breast cancer.Overexpression of HBXIP could desensitize MCF-7 and MDA-MB-231 cells to irradiation by inhibiting radiation-induced cell apoptosis,and knockdown of HBXIP in these cells had the converse response.Moreover,up-regulation of HBXIP resulted in the increase of XIAP and NF-κB levels in vitro and in vivo,while down-regulation of HBXIP led to the opposite effects.In addition,inhibition of XIAP and NF-κB abrogated the HBXIP overexpression induced radioresistization and increased cell apoptosis(25.8%augment for siRNA XIAP and 28.1%for NF-κB in MDA-MB-231 cells;25.4%augment for siRNA XIAP and 27.2%for NF–κB in MCF-7 cells).Conclusions:HBXIP enhances radioresistance of human breast cancer cells via upregulating XIAP,and targeting the HBXIP–NF–κB-XIAP pathway may be a potentially effective strategy to enhance the efficacy of radiotherapy for human breast cancer.

Identification of a three-gene prognostic signature for radioresistant esophageal squamous cell carcinoma

BACKGROUND Esophageal squamous cell carcinoma(ESCC)is causing a high mortality rate due to the lack of efficient early prognosis markers and suitable therapeutic regimens.The prognostic role of genes responsible for the acquisition of radioresistance in ESCC has not been fully elucidated.AIM To establish a prognostic model by studying gene expression patterns pertinent to radioresistance in ESCC patients.METHODS Datasets were obtained from the Gene Expression Omnibus and The Cancer Genome Atlas databases.The edgeR,a Bioconductor package,was used to analyze mRNA expression between different groups.We screened genes specifically responsible for radioresistance to estimate overall survival.Pearson correlation analysis was performed to confirm whether the expression of those genes correlated with each other.Genes contributing to radioresistance and overall survival were assessed by the multivariate Cox regression model through the calculation ofβi and risk score using the following formula:∑^(n)_(i=1)βi×PSI.RESULTS We identified three prognostic mRNAs(cathepsin S[CTSS],cluster of differentiation 180[CD180],and SLP adapter and CSK-interacting membrane protein[SCIMP])indicative of radioresistance.The expression of the three identified mRNAs was related to each other(r>0.70 and P<0.05).As to 1-year and 3-year overall survival prediction,the area under the time-dependent receiver operating characteristic curve of the signature consisting of the three mRNAs was 0.716 and 0.841,respectively.When stratifying patients based on the risk score derived from the signature,the high-risk group exhibited a higher death risk and shorter survival time than the low-risk group(P<0.0001).Overall survival of the low-risk patients was significantly better than that of the highrisk patients(P=0.018).CONCLUSION We have developed a novel three-gene prognostic signature consisting of CTSS,CD180,and SCIMO for ESCC,which may facilitate the prediction of early prognosis of this malignancy.

Cholesterol metabolism and tumor radiotherapy

Cholesterol is a lipid that is an essential component of the membrane structure in mammals.Cholesterol homeostasis regulates vital activities of individual cells and governs the overall function of the mammalian body.Cholesterol is mainly obtained through the biosynthesis of endogenous cholesterol and the intake of exogenous cholesterol.Cholesterol metabolism in tumor cells is abnormally active,and cholesterol and its metabolites(precursors and derivatives)play important roles in cancer proliferation,survival,invasion,metastasis,and the resistance to radiation.Preclinical studies have indicated that blocking cholesterol synthesis and uptake can reduce tumor progression and improve the response to anticancer treatment.Therapeutic strategies that target cholesterol synthesis,reduce plasma cholesterol levels,and prevent cholesterol esterification represent promising ways to improve the clinical outcome of cancer patients.

Targeting fatty acid synthase sensitizes human nasopharyngeal carcinoma cells to radiationvia downregulating frizzled class receptor 10

Objective:Our aim was to test the hypothesis that fatty acid synthase(FASN)expression contributes to radioresistance of nasopharyngeal carcinoma(NPC)cells and that inhibiting FASN enhances radiosensitivity.Methods:Targeting FASN using epigallocatechin gallate(EGCG)or RNA interference in NPC cell lines that overexpress endogenous FASN was performed to determine their effects on cellular response to radiationin vitro using MTT and colony formation assays,andin vivo using xenograft animal models.Western blot,immunohistochemistry,real-time PCR arrays,and real-time RT-PCR were used to determine the relationship between FASN and frizzled class receptor 10(FZD10)expression.FZD10 knockdown and overexpression were used to determine its role in mediating FASN function in cellular response to radiation.Immunohistochemical staining was used to determine FASN and FZD10 expressions in human NPC tissues,followed by analysis of their association with the overall survival of patients.Results:FASN knockdown or inhibition significantly enhanced radiosensitivity of NPC cells,bothin vitro andin vivo.There was a positive association between FASN and FZD10 expression in NPC cell lines grown as monolayers or xenografts,as well as human tissues.FASN knockdown reduced FZD10 expression,and rescue of FZD10 expression abolished FASN knockdown-induced enhancement of radiosensitivity.FASN and FZD10 were both negatively associated with overall survival of NPC patients.Conclusions:FASN contributes to radioresistance,possiblyvia FZD10 in NPC cells.Both FZD10 and FASN expressions were associated with poor outcomes of NPC patients.EGCG may sensitize radioresistance by inhibiting FASN and may possibly be developed as a radiosensitizer for better treatment of NPCs.