Survey of Radiosensitizing Agents (Synthesized Chemicals and Gene Therapeutic Agents) Since 2000

Radiotherapy has played an important role in treatment of tumor patientssince it appeared about 80 years ago, and has been an indispensable part of the management of about50% of tumors (especially 60% - 70% of malignant tumors). Currently, radiotherapy is used in simpleand palliative therapy, adjuvant therapy after or before surgery, simultaneous radio-chemotherapy,combined BRM (biological response modifier) therapy, ets. Radiosensitizing agents enhance theradiation effects on tumor cells so as to have better responses in radiotherapy. Tumor intrinsicradiosensitivity is affected by the hy-poxic level in solid tumor, the ability of the cells torepair the radiation-induced DNA damage, the number of cells which have a clonogenic capability toreestablish uncontrolled cell growth, the amount of dividing cells, and the distribution of cellsthroughout the cell cycle. Consequently , it is necessary and useful to add one or moreradiosensitizing agents in radiotherapy to increase the radio-sensitivity of tumor cells.

Survey on Natural Radiosensitizing Agents Since 2000

Actually, radiation alone is not enough to kill tumor cells efficientlybecause of the radioresistance of tumor cells. It is well known that tumors from the samehistolog-ical origin and of the same development stage are extremely heterogeneous in theirsensitivity to radiotherapy. One of the most resistant factors to radiation is that tumor cells arecommonly hypoxic. The study on radiosensitizing agents is one of the most interesting issues intumor radiotherapeutics. These radiosensitizing agents can be classified into three main categories:natural products, synthesized chemicals and gene therapeutic agents according to their origins andtherapeutic techniques. Many radiosensitizing agents have some side-effects when they are active;so, it is important and significant to do our best to find more radiosensitizing agents with higherefficiency and lower side-effects. On the other hand, the tumor cells are easy to become resistantto older radiosensitizing agents; hence, it is urgent to develop newer radiosensitizing agents forclinics. Natural products come from plants, animals and other living beings. When serving asradiosensitizing agents in tumor radiotherapy, they are more attractive and predominant than generaldrugs. The reasons include a great resource ( especially in China) , multifunctional regulation,higher effectiveness and safer clinical effects.

3-45 Radiosensitizing Effect of Functionalized Gold Nanoparticles on Human Hepatoma HepG2 Cells

Radiotherapy along with surgery and chemotherapy are the major therapeutic strategies for cancer treatment.The central goal of radiotherapy is to deliver a therapeutic dose to the tumor as much as possible whilst sparing thesurrounding normal tissues. Side effects are often observed in radiotherapy using conventional X-rays. Radiosensitizers,enhancing the radiation effects on tumors via increasing the dose specifically to the tumor tissues, canimprove the modality of radiotherapy against tumors.

A review of therapeutic agents for breast cancer with potentially radiosensitizing properties

Breast cancer is the most frequently diagnosed malignant tumor in women worldwide and the leading cause of cancer death.Radiotherapy for breast cancer is readily accepted and widely used in clinical practice.Potential limitations with radiotherapy include treatment resistance,side effects,and complications caused by high doses of irradiation.The search has been on to locate an efficacious radiosensitizer.This review summarizes six currently approved pharmaceuticals that have also been investigated for off-label use as radiosensitizers in breast cancer.

Targeting the organelle for radiosensitization in cancer radiotherapy

Radiotherapy is a well-established cytotoxic therapy for local solid cancers, utilizing high-energy ionizing radiation to destroy cancer cells. However, this method has several limitations, including low radiation energy deposition, severe damage to surrounding normal cells, and high tumor resistance to radiation. Among various radiotherapy methods, boron neutron capture therapy (BNCT) has emerged as a principal approach to improve the therapeutic ratio of malignancies and reduce lethality to surrounding normal tissue, but it remains deficient in terms of insufficient boron accumulation as well as short retention time, which limits the curative effect. Recently, a series of radiosensitizers that can selectively accumulate in specific organelles of cancer cells have been developed to precisely target radiotherapy, thereby reducing side effects of normal tissue damage, overcoming radioresistance, and improving radiosensitivity. In this review, we mainly focus on the field of nanomedicine-based cancer radiotherapy and discuss the organelle-targeted radiosensitizers, specifically including nucleus, mitochondria, endoplasmic reticulum and lysosomes. Furthermore, the organelle-targeted boron carriers used in BNCT are particularly presented. Through demonstrating recent developments in organelle-targeted radiosensitization, we hope to provide insight into the design of organelle-targeted radiosensitizers for clinical cancer treatment.

TOPK Inhibition Enhances the Sensitivity of Colorectal Cancer Cells to Radiotherapy by Reducing the DNA Damage Response

Objective Abnormal expression of T-lymphokine-activated killer cell-originated protein kinase(TOPK)was reported to be closely related to the resistance of prostate cancer to radiotherapy and to targeted drug resistance in lung cancer.However,the role of TOPK inhibition in enhancing radiosensitivity of colorectal cancer(CRC)cells is unclear.This study aimed to evaluate the radiosensitization of TOPK knockdown in CRC cells.Methods The expression of TOPK was detected in CRC tissues by immunohistochemistry,and the effect of TOPK knockdown was detected in CRC cells by Western blotting.CCK-8 and clonogenic assays were used to detect the growth and clonogenic ability of CRC cells after TOPK knockdown combined with radiotherapy in CRC cells.Furthermore,proteomic analysis showed that the phosphorylation of TOPK downstream proteins changed after radiotherapy.DNA damage was detected by the comet assay.Changes in the DNA damage response signaling pathway were analyzed by Western blotting,and apoptosis was detected by flow cytometry.Results The expression of TOPK was significantly greater in CRC tissues at grades 2–4 than in those at grade 1.After irradiation,CRC cells with genetically silenced TOPK had shorter comet tails and reduced expression levels of DNA damage response-associated proteins,including phospho-cyclin-dependent kinase 1(p-CDK1),phospho-ataxia telangiectasia-mutated(p-ATM),poly ADP-ribose polymerase(PARP),and meiotic recombination 11 homolog 1(MRE11).Conclusions TOPK was overexpressed in patients with moderately to poorly differentiated CRC.Moreover,TOPK knockdown significantly enhanced the radiosensitivity of CRC cells by reducing the DNA damage response.

MiR-450b-5p enhances the radiosensitivity of HR^(+) and HER2^(−) breast cancer by targeting CDK6

Background:The sensitivity of breast cancer cells to radiation is a key cause of locoregional recurrence after postoperative radiotherapy.Several studies have reported that microRNAs(miRNAs)are involved in the radiosensitivity of human breast cancer cells.One miRNA microarray study showed that miR-450b-5p was overexpressed 13.3-fold in patients with estrogen receptor–positive(ER^(+))and human epidermal growth factor receptor 2–negative(HER2−)breast cancer and no local relapse compared with local relapse patients.However,its underlying mechanism of action remains unknown.Methods:The predicted target mRNAs of miR-450b-5p were screened using the TargetScan,miRDB,and miRWalk databases.Western blotting,quantitative polymerase chain reaction,and dual-luciferase reporter assays explored the association between cyclindependent kinase 6(CDK6)and miR-450b-5p.The cell counting kit-8 assay and flow cytometry detected the proliferation of transfected MCF7 cells.Colony formation and xenograft tumors detected the radiosensitivity of the transfected MCF7 cells.Results:Bioinformatics analysis,Western blotting,quantitative polymerase chain reaction,and dual-luciferase reporter assays demonstrated that CDK6 was the target gene of miR-450b-5p.Furthermore,in vitro and in vivo experiments showed that miR-450b-5p inhibited MCF7 cell proliferation and cell cycle progression,increased the sensitizer enhancement ratio,and decreased the volume of xenograft tumors after irradiation by regulating CDK6.Conclusions:This study demonstrates that miR-450b-5p enhances the radiosensitivity of hormone receptor–positive(HR^(+))and HER2−breast cancer cells and elucidates its mechanism.miR-450b-5p may be considered a therapeutic target in HR^(+)and HER2−breast cancer treated with radiotherapy.

Advancements in understanding mechanisms of hepatocellular carcinoma radiosensitivity:A comprehensive review

Primary liver cancer is a significant health problem worldwide.Hepatocellular carcinoma(HCC)is the main pathological type of primary liver cancer,accounting for 75%-85%of cases.In recent years,radiotherapy has become an emerging treatment for HCC and is effective for various stages of HCC.However,radiosensitivity of liver cancer cells has a significant effect on the efficacy of radiotherapy and is regulated by various factors.How to increase radiosensitivity and improve the therapeutic effects of radiotherapy require further exploration.This review summarizes the recent research progress on the mechanisms affecting sensitivity to radiotherapy,including epigenetics,transportation and metabolism,regulated cell death pathways,the microenvironment,and redox status,as well as the effect of nanoparticles on the radiosensitivity of liver cancer.It is expected to provide more effective strategies and methods for clinical treatment of liver cancer by radiotherapy.

Significance of the Expression of CyclinD1 and Ki67 Antigen in Nasopharyngeal Carcinoma

Objective: To detect the expression of cyclinD1 and Ki67 in nasopharyngeal carcinoma (NPC) and their correlation with the biological behaviors and prognosis. Methods: 56 cases of biopsy specimens of NPC which had been embedded with para?n in 1996 in our hospital were collected and immunostained with cyclinD1 and Ki67 monoclonal antibodies by means of the streptavidin peroxides method. The patients were followed up periodically, and then their biological behaviors and prognosis were statistically analyzed. Results: The percentage of cyclinD1 and Ki67 positive cells in the NPC specimens ranged from 0–54% and 0–31% respectively. The staining was nuclear. Of the 56 cases, 30 cases (56.6%) highly expressed cyclinD1 or Ki67 HPI and 26 cases (46.4%) lowly expressed cyclinD1, while only 16 cases (28.6%) showed Ki67 HPI (high proliferated index) and 40 cases (71.4%) showed Ki67 LPI (low proliferated index). Patients who lowly expressed cyclinD1 or highly expressed Ki67 had a higher radiosensitivity and a better prognosis. Conclusion: CyclinD1 and Ki67 immunohistochemical staining is considered to be useful, not only as an independent factor of radiosensitivity and prognosis respectively, but also as a means of determining the optimum treatment for each individual patient with NPC.

Comparative study on radiosensitivity of various tumor cells and human normal liver cells

AIM:To investigate the radiation response of various human tumor cells and normal liver cells. METHODS: Cell lines of human hepatoma cells (SMMC-7721), liver cells (L02), melanoma cells (A375) and cervical tumor (HeLa) were irradiated with 60Co γ-rays. Cell survive was documented by a colony assay. Chromatid breaks were measured by counting the number of chromatid breaks and isochromatid breaks immediately after prematurely chromosome condensed by Calyculin-A. RESULTS: Linear quadratic survival curve was observed in all of four cell lines, and dose-dependent increase in radiation-induced chromatid and isochromatid breaks were observed in GB2B phase. Among these four cell lines, A375 was most sensitive to radiation, while, L02 had the lowest radiosensitivity. For normal liver cells, chromatid breaks were easy to be repaired, isochromatid breaks were difficult to be repaired. CONCLUSION: The results suggest that the y-rays induced chromatid breaks can be possibly used as a good predictor of radiosensitivity, also, unrejoined isochromatid breaks probably tightly related with cell cancerization.

Brucea javanica oil emulsion improves the effect of radiotherapy on esophageal cancer cells by inhibiting cyclin D1-CDK4/6 axis

BACKGROUND Esophageal cancer is one of the most common cancers around the world, and it has high incidence and mortality rates. The conventional therapy for esophageal cancer is radiotherapy, although its effect is highly limited by the resistance of esophageal cancer cells. Thus, strong radiosensitizers can be very crucial during radiotherapy against esophageal cancer. Brucea javanica oil emulsion (BJOE) is a widely used drug against various cancers, such as liver, colon, and ovarian cancer. However, its anti-cancer effect and mechanism and the use of BJOE as a radiosensitizer have not been explored in esophageal cancer. AIM To evaluate the anti-cancer effect and mechanism of BJOE and explore the potential use of BJOE as a radiosensitizer during radiotherapy. METHODS The inhibitory effect of BJOE and its enhancement function with radiation on cell viability were examined with the calculated half-maximal effective concentration and half-maximal lethal concentration. The influence of BJOE on cell migration and invasion were measured with EC109 and JAR cells by wound-healing and transwell assay. Clonogenesis and apoptotic rate, which was measured by Hoechst staining, were investigated to confirm its enhancement function with radiation. To investigate the molecular pathway underlying the effect of BJOE, the expressions of several apoptosis- and cycle-related proteins was detected by western blotting.cell lines more than normal cell lines, and it markedly reduced migration and invasion in esophageal cancer cells (EC109 and JAR). Moreover, it promoted cell apoptosis and enhanced the effect of radiotherapy against esophageal cancerous cells. In the viability test, the values of half-maximal effective concentration and half-maximal lethal concentration were reduced. Compared to the control, only around 1/5 colonies formed when using BJOE and radiation together in the clonogenic assay. The apoptotic rate in EC109 was obviously promoted when BJOE was added during radiotherapy. Our study suggests that the expression of the apoptosis-proteins Bax and p21 were increased, while the expression of Bcl-2 was stable. Further detection of downstream proteins revealed that the expression of cyclin D1 and cyclin-dependent kinase 4/6 were significantly decreased. CONCLUSION BJOE has a strong anti-cancer effect on esophageal cancer and can be used as a radiosensitizer to promote apoptosis in cancerous esophageal cells via the cyclin D1-cyclin-dependent kinase 4/6 axis.

Biomarkers for enhancing the radiosensitivity of nasopharyngeal carcinoma

Nasopharyngeal carcinoma(NPC) is a common head and neck malignancy. The incidence of NPC is higher in Southern China and Southeast Asia compared with Western countries. Given its high radiosensitivity, the standard treatment for NPC is radiotherapy. However, radioresistance remains a serious obstacle to successful treatment. Radioresistance can cause local recurrence and distant metastases in some patients after treatment by radiation. Thus, special emphasis has been given to the discovery of effective radiosensitizers. This review aims to discuss the biomarkers, classified according to the main mechanisms of radiosensitization, which can enhance the sensitivity of NPC cells to ionizing radiation.

Autophagy inhibition by chloroquine sensitizes HT-29 colorectal cancer cells to concurrent chemoradiation

AIM:To investigate whether the inhibition of autophagy by chloroquine(CQ)sensitizes rectal tumors to radiation therapy(RT)or concurrent chemoradiation(chemoRT).METHODS:In vitro,HCT-116 and HT-29 colorectal cancer(CRC)cell lines were treated as following:(1)PBS;(2)CQ;(3)5-fluorouracil(5-FU);(4)RT;(5)CQ and RT;(6)5-FU and RT;(7)CQ and 5-FU;and(8)5-FU and CQ and RT.Each group was then exposed to various doses of radiation(0-8 Gy)depending on the experiment.Cell viability and proliferative capacity were measured by3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)and clonogenic assays.Clonogenic survivalcurves were constructed and compared across treatment groups.Autophagy status was determined by assessing the LC3-Ⅱto LC3-Ⅰratio on western blot analysis,autophagosome formation on electron microscopy and identification of a perinuclear punctate pattern with GFPlabeled LC3 on fluorescence microscopy.Cell cycle arrest and cell death were evaluated by FACS and AnnexinⅤanalysis.All experiments were performed in triplicate and statistical analysis was performed by the student’s t test to compare means between treatment groups.RESULTS:RT(2-8 Gy)induced autophagy in HCT-116and HT-29 CRC cell lines at 4 and 6 h post-radiation,respectively,as measured by increasing LC3-Ⅱto LC3-Ⅰratio on western blot.Additionally,electron microscopy demonstrated autophagy induction in HT-29 cells24 h following irradiation at a dose of 8 Gy.Drug treatment with 5-FU(25μmol/L)induced autophagy and the combination of 5-FU and RT demonstrated synergism in autophagy induction.CQ(10μmol/L)alone and in combination with RT effectively inhibited autophagy and sensitized both HCT-116 and HT-29 cells to treatment with radiation(8 Gy;P<0.001 and 0.00001,respectively).Significant decrease in clonogenic survival was seen only in the HT-29 cell line,when CQ was combined with RT at doses of 2 and 8 Gy(P<0.5 and P=0.05,respectively).There were no differences in cell cycle progression or Annexin V staining upon CQ addition to RT.CONCLUSION:Autophagy inhibition by CQ increases CRC cell sensitivity to concurrent treatment with 5-FU and RT in vitro,suggesting that addition of CQ to chemoRT improves CRC treatment response.

β-elemene enhances the radiosensitivity of gastric cancer cells by inhibiting Pak1 activation

AIM:To explore the potential of β-elemene as a radiosensitizer for gastric cancer cells and the underlying mechanisms.METHODS:SGC7901,MKN45,MKN28,N87,and AGS human gastric cancer cell lines were used to screen for radioresistant gastric cancer cell lines. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium(MTT) assay was used to determine the effects of β-elemene and IPA-3 on cell viability in MKN45 and SGC7901 gastric cancer cell lines. A clonogenic survival assay and annexin V-FITC/PI apoptosis detection assay were used to evaluate cellular radiosensitivity and radiation-induced cell death,respectively. A proteomic method,isobaric tags for relative and absolute quantitation(i TRAQ),was employed to screen the proteins regulated by β-elemene pretreatment prior to ionizing radiation(IR) in SGC7901 gastric cancer cell line. IPA-3 was used as a specific small molecule inhibitor of p21-activated protein kinase 1(Pak1) to target Pak1 signaling. Protein levels of PAK1IP1(p21-activated protein kinase-interacting protein 1),total Pak1(t-Pak1),phospho-Pak1(T423),phospho-ERK1/2( Thr202/Tyr204),and cleaved caspase-3(17 k Da) were assessed by western blotting.RESULTS:MKN45 and SGC7901 gastric cancer cell lines were relatively more resistant to IR. β-elemene pretreatment decreased clonogenic survival following IR in MKN45 and SGC7901 gastric cancer cell lines. Additionally,β-elemene pretreatment prior to IR increased radiation-induced cell death compared with IR alone in MKN45(10.4% ± 0.9% vs 34.8% ± 2.8%,P < 0.05) and SGC7901(11.6% ± 0.9% vs 46.7% ± 5.2%,P < 0.05) human gastric cancer cell lines,respectively,consistent with the level of cleaved caspase-3(17 k Da). Through i TRAQ analysis and western blot validation,we found that β-elemene upregulated PAK1IP1 and downregulated phospho-Pak1(T423) and phosphoERK1/2 in SGC7901 gastric cancer cells. IR increased the level of phospho-Pak1(T423). Pretreatment with β-elemene decreased radiation-induced Pak1 and ERK1/2 phosphorylation. Inhibition of Pak1 using IPA-3 decreased clonogenic survival following IR. In addition,IPA-3 increased radiation-induced cell death in MKN45(13.4% ± 0.3% vs 26.6% ± 1.0%,P < 0.05) and SGC7901(16.0% ± 0.6% vs 37.3% ± 1.7%,P < 0.05) gastric cancer cell lines,respectively,consistent with the level of cleaved caspase-3(17 k Da). Western blotting showed that IPA-3 decreased radiation-induced Pak1 and ERK1/2 phosphorylation.CONCLUSION:This is the first demonstration that β-elemene enhances radiosensitivity of gastric cancer cells,and that the mechanism involves inhibition of Pak1 signaling.

Antitumor effects and radiosensitization of cytosine deaminase and thymidine kinase fusion suicide gene on colorectal carcinoma cells

AIM: To investigate the killing effect and radiosensitization of double suicide gene mediated by adenovirus on colorectal carcinoma cells. METHODS: Colorectal carcinoma cell line SW480 was transfected with adenovirus expression vector containing cytosine deaminase (CD) and thymidine kinase (TK) fusion gene. The expression of CD-TK fusion gene was detected by reverse transcriptase-polymerase chain reaction. The toxic effect of ganciclovir (GCV) and 5-fluorocytosine (5-FC) on infected cells was determined by MTT assay. The radiosensitization of double suicide gene was evaluated by clonogenic assay. RESULTS: After prodrugs were used, the survival rate of colorectal carcinoma cells was markedly decreased. When GCV and 5-FC were used in combination, the cytotoxicity and bystander effect were markedly superior to a single prodrug (X2 = 30.371, P<0.01). Both GCV and 5-FC could sensitize colorectal carcinoma cells to the toxic effect of radiation, and greater radiosensitization was achieved when both prodrug were used in combination. CONCLUSION: CD-TK double suicide gene can kill and radiosensitize colorectal carcinoma cells.

Radiosensitivity of human colon cancer cell enhanced by immunoliposomal docetaxel

AIM:To enhance the radiosensitivity of human colon cancer cells by docetaxel. METHODS: Immunoliposomal docetaxel was prepared by coupling monoclonal antibody against carcinoembryonic antigen to cyanuric chloride at the PEG terminus of liposome. LoVo adenocarcinoma cell line was treated with immunoliposomal docetaxel or/and irradiation. MTT colorimetric assay was used to estimate cytotoxicity of immunoliposomal docetaxel and radiotoxicity. Cell cycle redistribution and apoptosis were determined with flow cytometry. Survivin expression in LoVo cells was verified by immunohistochemistry. D801 morphologic analysis system was used to semi-quantify immunohistochemical staining of survivin. RESULTS: Cytotoxicity was induced by immunoliposomal docetaxel alone in a dose-dependent manner. Immunoliposomal docetaxel yielded a cytotoxicity effect at a low dose of 2 nmol/L. With a single dose irradiation, the relative surviving fraction of LoVo cells showed a dose-dependent response, but there were no significant changes as radiation delivered from 4 to 8 Gy. Compared with liposomal docetaxel or single dose irradiation, strongly radiopotentiating effects of immunoliposomal docetaxel on LoVo cells were observed. A low dose of immunoliposomal docetaxel could yield sufficient radiosensitivity. Immunoliposomal docetaxel were achieved both specificity of the conjugated antibody and drug radiosensitization. Combined with radiation, immunoliposomal docetaxel significantly increased the percentage of G2/M cells and induced apoptosis, but significantly decreased the percentage of cells in G2/G1 and S phase by comparison with liposomal docetaxel. Immunohistochemical analysis showed that the brown stained survivin was mainly in cytoplasm of LoVo cells. Semi-quantitative analysis of the survivin immunostaining showed that the expression of survivin in LoVo cells under irradiation with immunoliposomal docetaxel was significantly decreased. CONCLUSION: Immunoliposomal docetaxel is strongly effective for target radiosensitation in LoVo colon carcinoma cells, and may offer the potential to improve local radiotherapy.

Anti-miRNA-221 sensitizes human colorectal carcinoma cells to radiation by upregulating PTEN

AIM:To investigate the regulative effect of miRNA(miR)-221 on colorectal carcinoma(CRC)cell radiosensitivity and the underlying mechanisms.METHODS:A human CRC-derived cell line was cultured conventionally and exposed to different doses of X-rays(0,2,4,6 and 8 Gy).The total RNA and protein of the cells were extracted 24 h after irradiation,and the alteration of miR-221 and phosphatase and tensin homolog deleted on chromosome 10(PTEN)gene mRNA expression was detected by real-time reverse transcriptase polymerase chain reaction(PCR).The protein alteration of PTEN in the cells was detected by Western blotting.Caco2 cells were pretreated with or without anti-PTEN-siRNA prior to the addition of premiR-221 or anti-miR-221 using Lipofectamine 2000.Colony formation assay and flow cytometry analysis were used to measure the surviving cell fraction and the sensitizing enhancement ratio after irradiation.Ad-ditionally,PTEN 3′-untranslated region fragment was PCR amplified and inserted into a luciferase reporter plasmid.The luciferase reporter plasmid construct was then transfected into CRC cells together with premiR-221 or anti-miR-221,and the luciferase activity in the transfected cells was detected.RESULTS:The X-ray radiation dose had a significant effect on the expression of miR-221 and PTEN protein in human Caco2 cells in a dose-dependent manner.The miR-221 expression level improved gradually with the increase in irradiation dose,while the PTEN protein expression level reduced gradually.miR-221 expression was significantly reduced in the anti-miR-221 group compared with the pre-miR-221 and negative control groups(P<0.01).Anti-miR-221 upregulated expression of PTEN protein and enhanced the radiosensitivity of Caco2 cells(P<0.01).Moreover,the inhibitory effect was dramatically abolished by pretreatment with anti-PTEN-siRNA,suggesting that the enhancement of radiosensitivity was indeed mediated by PTEN.A significant increase of luciferase activity was detected in CRC cells that were cotransfected with the luciferase reporter plasmid construct and anti-miR-221(P<0.01).CONCLUSION:Anti-miR-221 can enhance the radiosensitivity of CRC cells by upregulating PTEN.

Endoplasmic reticulum stress sensitizes human esophageal cancer cell to radiation

AIM:To investigate the role of endoplasmic reticulum(ER) stress in cancer radiotherapy and its molecular mechanism.METHODS:Tunicamycin(TM) was applied to induce ER stress in human esophageal cancer cell line EC109,and the radiosensitization effects were detected by acute cell death and clonogenic survival assay.Cell cycle arrest induced by TM was determined by flow cytometric analysis after the cellular DNA content was labeled with propidium iodide.Apoptosis of EC109 cells induced by TM was detected by annexin V staining and Western blotting of caspase-3 and its substrate poly ADP-ribose polymerase.Autophagic response was determined by acridine orange(AO) staining and Western blotting of microtubule-associated protein-1 light chain-3(LC3) and autophagy related gene 5(ATG5).In order to test the biological function of autophagy,specific inhibitor or Beclin-1 knockdown was used to inhibit autophagy,and its effect on cell apoptosis was thus detected.Additionally,involvement of the phosphatidylinositol-3 kinase(PI3K)/Akt/mammalian target of the rapamycin(mTOR) pathway was also detected by Western blotting.Finally,male nude mice inoculated subcutaneously with EC109 cells were used to confirm cell model observations.RESULTS:Our results showed that TM treatment enhanced cell death and reduced the colony survival fraction induced by ionizing radiation(IR),which suggested an obvious radiosensitization effect of TM.Moreover,TM and IR combination treatment led to a significant increase of G2/M phase and apoptotic cells,compared with IR alone.We also observed an increase of AO positive cells,and the protein level of LC3-II and ATG5 was induced by TM treatment,which suggested an autophagic response in EC109 cells.However,inhibition of autophagy by using a chemical inhibitor or Beclin-1 silencing led to increased cell apoptosis and decreased cell viability,which suggested a cytoprotective role of autophagy in stressed EC109 cells.Furthermore,TM treatment also activated mTORC1,and in turn reduced Akt phosphorylation,which suggested the PI3K/Akt/mTOR signal pathway was involved in the TM-induced autophagic response in EC109 cells.Tumor xenograft results also showed synergistic retarded tumor growth by TM treatment and IR,as well as the involvement of the PI3K/Akt/mTOR pathway.CONCLUSION:Our data showed that TM treatment sensitized human esophageal cancer cells to radiation via apoptosis and autophagy both in vitro and in vivo.

Prediction value of radiosensitivity of hepatocarcinoma cells for apoptosis and micronucleus assay

AIM： To investigate the prediction value of radiosensitivity of hepatocarcinoma cells for apoptosis and rnicronucleus assay. METHODS： Clonogenic assay, flow cytometry, and CB micronuclei assay were used to survey the cell survival rate, radiation-induced apoptosis and rnicronucleus frequency of hepatocarcinorna cell lines SMMC-7721, HL-7702, and HepG2 after being irradiated by X-ray at the dosage ranging 0-8 Gy. RESULTS： After irradiation, there was a dose-effect relationship between rnicronucleus frequency and radiation dosage among the three cell lines （P〈0.05）. A positive relationship was observed between apoptosis and radiation dosage among the three cell lines. The HepG2 cells had a significant correlation （P〈0.05） but apoptosis incidence had a negative relationship with rnicronucleus frequency. There was a positive relationship between apoptosis and radiation dosage and the correlation between 5MMC-7721 and HL-7702 cell lines had a significant difference （P〈0.01）. After irradiation, a negative relationship between cell survival rate and radiation dosages was found among the three cell lines （P〈0.01）. There was a positive relationship between cell survival rate and rnicronucleus frequency （P〈0.01）. No correlation was observed between apoptosis and cell survival rate. CONCLUSION： The radiosensiUvity of hepatocarcinoma cells can be reflected by apoptosis and rnicronuclei. Detection of apoptosis and rnicronuclei could enhance the accuracy for predicting radiosensitivity.

Effect of silencing Bcl-2 expression by small interfering RNA on radiosensitivity of gastric cancer BGC823 cells

Objective:To explore the influence of silencing Bcl-2 expression by small interfering RNA（siRNA） on Bcl-2 protein expression,cell apoptosis rale and radiosensilivity of gastric cancer BCC823 cells.Methods:siRNA segment for Bcl-2 gene was designed and synthesized,then was induced into gastric cancer BGC 823 cells by liposome transfection.Bcl-2 protein expression was detected by Western Blotting.After X radiation,flow cytometry and clone forming assay were used to determine the effects of RNA interference on BGC823 cell apoptosis rate and radiosensitivity. Result:After the transfection of Bcl-2 siRNA,the positive expression rate of Bcl-2 protein in BGC823 cells was（35.45±2.35）%.Compared with the control group and negative siRNA transfection group,the rate was significantly decreased（P【0.01）.The apoptosis rate of BGC823-RNAi cell was（10.81±0.91）%,which was significantly higher than the control group and negative siRNA transfection group（P【0.01）.After 48h X radiation,the apoptosis rate of BGC823-RNAi was（28.91±1.40）%,which was significantly higher than the control group and the group without radiation （P【0.01）.During clone forming assay D0,D4 and SF2 values in Bcl-2 siRNA1 transfection group were all lower than those in the control group.The radiosensitivity ratio was 1.28（the ratio of D0） and 1.60（the ratio of D4）.Conclusions:Specific siRNA of Bcl-2 gene can effectively inhibit the expression of Bcl-2 gene,enhance the radiosensitivity and apoptosis of gastric cancer BGC823 cells,having good clinical application perspective.