胃癌组织ATP生物荧光肿瘤体外药物敏感试验

目的研究胃癌组织体外对化疗药物的敏感性,以筛选出敏感性较强的化疗药物。方法收集33例新鲜人胃癌标本,采用ATP生物荧光肿瘤体外药敏检测技术（ATP-TCA）,分别检测其对11种临床常用化疗药物的敏感性。结果 33份胃癌标本中,31份标本成功进行ATP-TCA检测,可评估率为93.9%。胃癌组织体外对化疗药物敏感性存在明显差异,敏感性自高到低依次为紫杉醇（PTX）、多西紫杉醇（DOC）、氟脲嘧啶（5-Fu）、顺铂（DDP）、丝裂霉素（MMC）、奥沙利铂（L-OHP）、阿霉素（ADM）、表阿霉素（EPI）、长春地辛（VDS）、长春新碱（VCR）和足叶乙甙（Vp-16）等。结论胃癌组织对化疗药物的敏感程度相对较低,且存在明显个体异质性。ATP-TCA可为胃癌选择合适的化疗药物,为临床合理用药提供参考。     

人脑胶质瘤ERCC2 mRNA表达与化疗药物敏感性的关系

背景与目的:以往细胞株的研究提示,核苷酸切除修复系统中的重要因子ERCC2表达与BCNU耐药相关,然而在人脑胶质瘤是否同样如此,还没有明确资料。本研究将对人脑胶质瘤临床标本进行体外药敏试验,并分析其与ERCC2表达的关系。方法:在人脑胶质瘤手术时收集新诊断的原发性胶质瘤新鲜标本61例,采用MTT法进行体外药敏试验,测定脑瘤常用化疗药DDP、BCNU、VCR和VM26的敏感性。并对收集的肿瘤标本采用实时定量RT-PCR方法检测ERCC2mRNA的表达,然后对二者结果进行相关性分析。结果:体外药物敏感性检测中,49例样本获得成功检测,成功率达到80%。体外药敏结果在49例样本中差别较大。四种化疗药物DDP、BCNU、VCR和VM26在血浆峰浓度下的肿瘤生长抑制率(IR)分别为(37.8±2.6)%、(29.7±3.1)%、(31.3±2.7)%和(40.7±2.7)%。49例肿瘤标本的ERCC2mRNA相对表达范围较广,为0.01￣10.50。相关性分析显示ERCC2表达同BCNU敏感性负相关(Spearman相关系数为-0.373,P=0.004),而与DDP、VCR以及VM26的敏感性没有统计学意义。结论:人脑胶质瘤组织中ERCC2mRNA表达与BCNU敏感性相关,但与DDP、VCR和VM26的体外敏感性无关。     

脑胶质瘤化疗药物敏感性的临床研究

背景与目的 :脑胶质瘤是一个需要多学科综合治疗的恶性脑部疾病,国内外学者都在积极探索更加有效的综合治疗方法。本文探讨脑胶质瘤细胞在体外对化疗药物的敏感性,为临床有效治疗胶质瘤提供实验依据。方法:应用四甲基偶氮唑盐比色法(methyl thiazolyl tetrazolium,MTT)对胶质瘤化疗的7种常用药物体外敏感性进行检测。结果:总体化疗药物敏感性BCNU﹥VM-26、TMZ﹥DDP﹥CBP﹥VP-16﹥VCR;低级别胶质瘤(WHO分级Ⅰ、Ⅱ级)化疗药物敏感性BCNU﹥TMZ﹥VM-26、DDP﹥CBP、VCR﹥VP-16;高级别胶质瘤(WHO分级Ⅲ、Ⅳ级)化疗药物敏感性BCNU、VM-26﹥TMZ、DDP﹥VP-16﹥CBP﹥VCR。结论:体外药敏试验对排除无效药物、筛选敏感药物对脑胶质瘤进行个体化的化疗,提高临床化疗效果,具有重要意义。     

恶性肿瘤患者化疗敏感性筛选的临床意义

目的 研究不同种类的恶性肿瘤患者对22种化疗药物的敏感性,筛选敏感性化疗药物,为临床化疗用药提供参考。方法 182例患者的恶性肿瘤细胞分别用22种化疗药物作用24～48h,药物依据临床血浆高峰浓度（PPC）配制;采用MTT法检测肿瘤细胞抑制率,评价药物敏感性。结果 在药物浓度1.0PPC和细胞浓度3～5×105／ml的测试条件下,7种不同化疗药物对40例恶性神经胶质瘤细胞的抑制率均不同,其中BCNU、TMZ、VM26的抑制率较高,7种药物的敏感率由高到低依次为BCNU＞TMZ＞DDP＞VM26＞VCR＞CBP＞VP16;13种化疗药物对59例卵巢癌细胞的抑制率不同,其敏感率由高到低依次为L OHP＞TPT＞TAX＞ADM＞TXT＞GEM＞CBP＞CTX＞IFO＞LBP＞DDP＞PYM＞EADM;6 种化疗药物对19例骨及软组织肿瘤细胞的抑制率相近,MTX和TAX的抑制率达到40％以上,药物敏感率由高到低依次为ADM＞MTX＞IFO＞DDP＞TAX＞DTIC;8种药物对64例头颈部肿瘤细胞的抑制率不同,药物敏感率由高到低依次为PYM＞CTX＞BLM＞DDP＞5 FU＞VP16＞VCR＞TAX。结论 肿瘤患者对化疗药物的敏感性存在明显的个体差异,同一种药物对不同恶性肿瘤细胞作用的抑制率均不同,不同药物的敏感率在不同肿瘤中的比例均不同。化疗前对不同恶性肿瘤患者进行个体化疗敏感性筛选是必要的,可以有效避免盲目用药,减少毒副作用,提高疗效和生存质量。     

MDR1和GST-π在骨软组织肉瘤中的表达及其与化疗耐药的关系

目的 探讨多药耐药基因1（MDR1）和谷胱苷肽-S-转移酶-π（GST-π）在骨软组织肉瘤组织中的表达及其与化疗耐药的关系。方法应用荧光定量PCR（FQ-PCR）和流式细胞术（FCM）,分别在mRNA水平和蛋白水平检测MDR1和GST-π的表达;以四甲基偶氮唑盐法（MTT）法检测瘤组织对阿霉素（ADM）、顺铂（DDP）、5-氟脲嘧啶（5-Fu）、丝裂霉素C（MMC）、氮烯咪胺（DTIC）、长春新碱（VCR）和氨甲喋呤（MTX）的敏感性。结果 患者瘤组织对ADM、DDP、5-Fu、MMC、lyric、VCR和MTX的不敏感率分别为41．18％、17．65％、47．06％、50．00％、76．47％、61．76％和52．94％。瘤组织中P-gp和GST-π相对荧光强度的表达分别为1．54和为2．58。X^2分析显示,P-gp的表达与ADM耐药、GST-π的表达与ADM、DDP、MMC耐药均呈正相关（P〈0．05）。MDR1和GST-π的表达与患者年龄、性别、病理类型、肿瘤大小均无关（P〉0．05）。GST-π在术前化疗患者的瘤组织中表达升高,且术前表达升高者,术后复发率高于术前GST-π表达水平较低者（P〈0．05）。结论 骨软组织肉瘤患者的MDR1、GST-π表达及化疗敏感性存在个体差异;化疗引起GST-π表达上调;原发GST-π高表达是骨软组织肉瘤耐药的主要机制,并与患者预后不良有关。     

乳腺癌的TECIA法药敏试验及其临床应用价值

目的探讨组织培养-终点染色计算机图像分析（TECIA）法体外肿瘤药敏试验对乳腺癌化疗的临床应用价值。方法选取2005年9月至2008年9月本院手术的46例乳腺癌标本,采用TECIA法进行化疗药物敏感性的体外检测。所测药物为乳腺癌常用化疗药物紫杉醇（PTX）、诺维本（NVB）、多柔比星（ADM）、氨甲喋呤（MTX）、5-氟脲嘧啶（5-FU）、顺铂（DDP）及联合化疗TA（PTX＋ADM）、NP（NVB＋DDP）、CAF（CTX＋ADM＋5-FU）、CMF（CTx＋MTX＋5-FU）方案。化疗药物敏感性差异的比较,采用多个样本率的χ^2检验。结果46例乳腺癌对化疗药物的敏感性为：PTX60．9％（28／46）、NVB58．7％（27／46）、ADM56．5％（27／46）、MTX37．0％（17／46）、5-FU 34．8％（16／46）、DDP26．1％（12／46）;PTX、NVB、ADM、MTX之间及5-FU和DDP之间比较,敏感率差异均无统计学意义（χ^2=6．724,P=0．081;χ^2=0．821,P=0．365）,PTX、NVB比5-FU、DDP的敏感率高,其差异有统计学意义（P〈0．003）;TA、NP、CAF和CMF方案的敏感率分别为71．7％（33／46）、67．4％（31／46）、45．7%（21／46）、39．1％（18／46）,但TA与NP方案、CAF与CMF方案比较,差异无统计学意义（P〉0．007）;TA和NP方案比CAF和CMF方案的敏感率高,其差异有统计学意义（P〈0．007）。PTX、NVB及含有此类药物的联合化疗方案的敏感性较高,化疗药物敏感性存在个体差异。结论TECIA法体外肿瘤药敏试验在乳腺癌的化疗用药方面具有指导意义。     

胃癌组织ATP生物荧光肿瘤体外药物敏感试验

目的研究胃癌组织体外对化疗药物的敏感性,以筛选出敏感性较强的化疗药物。方法收集33例新鲜人胃癌标本,采用ATP生物荧光肿瘤体外药敏检测技术(ATP-TCA),分别检测其对11种临床常用化疗药物的敏感性。结果 33份胃癌标本中,31份标本成功进行ATP-TCA检测,可评估率为93.9%。胃癌组织体外对化疗药物敏感性存在明显差异,敏感性自高到低依次为紫杉醇(PTX)、多西紫杉醇(DOC)、氟脲嘧啶(5-Fu)、顺铂(DDP)、丝裂霉素(MMC)、奥沙利铂(L-OHP)、阿霉素(ADM)、表阿霉素(EPI)、长春地辛(VDS)、长春新碱(VCR)和足叶乙甙(Vp-16)等。结论胃癌组织对化疗药物的敏感程度相对较低,且存在明显个体异质性。ATP-TCA可为胃癌选择合适的化疗药物,为临床合理用药提供参考。     

耐药基因检测及体外药敏试验在卵巢癌个体化治疗中的价值

目的 探讨卵巢癌耐药基因表达与体外药敏试验及临床生物学行为的关系.方法 采用流式细胞术和MTT法对60例卵巢癌患者分别检测组织中的COX-2、CX43、P-gp基因表达和对常用化疗药物的敏感性,并对其临床近期疗效关系进行分析.结果 COX-2表达在顺铂(DDP)耐药组高于DDP敏感组,差异有统计学意义(P=0.01).CX43表达在DDP耐药组低于DDP敏感组,差异有统计学意义(P=0.005).P-gp表达在对依托泊苷(VP16)耐药组高于VP16敏感组,差异有统计学意义(P=0.009).CX43表达在对紫杉醇(Taxol)耐药组低于Taxol敏感组.差异有统计学意义(P=0.001).COX-2高表达、CX43低表达、P-gp高表达的癌组织对化疗药物的敏感性低于COX-2低表达、CX43高表达、P-gP低表达者.5-Fu、CBP、VCR、PYM、EPI、GEM的敏感性与COX-2、CX43、P-gp表达高低无显著相关性.结论 卵巢癌组织中COX-2与P-gp高表达、CX43低表达与部分化疗药物的体外药敏试验敏感性有关.耐药基因相关蛋白COX-2、P-gp、CX43的检测,结合肿瘤药敏试验结果选择敏感化疗方案能提高化疗疗效.从而使卵巢癌治疗个体化.     

脑胶质瘤中miR-181b的表达及临床意义

背景与目的：miR-181b在多种肿瘤中表达异常,并参与调节多种抗肿瘤药物的敏感性。研究发现miR-181b在胶质瘤中具有起类似抑癌基因的作用．可作为胶质瘤的独立预后指标。本研究旨在进一步探讨恶性胶质瘤中miR-181b表达的临床意义及miR-181b对替莫唑胺化疗敏感性的影响。方法：收集不同病理级别胶质瘤标本,以荧光定量PCR法检测其中miR-181b的表达,分析其与胶质瘤病理分级及患者预后的关系：利用CCK-8细胞毒性实验检测患者恶性胶质瘤细胞对替莫唑胺的敏感性。并分析其与miR-181b表达的关系。结果：miR-181b在胶质瘤组织中的表达显著低于正常脑组织伊〈0．051．miR-181b的表达水平分别为：正常脑组织3．69±0．477,WH0I级2．56±0．354．WHOⅡ级0．81±0．222．WHOⅢ级0．42±0．130．WH0 Ⅳ级0．21±0．067。miR-181b表达低的患者中位生存期为370±37天．而miR-181b表达高的患者中位生存期为493±60天（P〈0．05）。在高级别胶质瘤中,miR-181b的表达与替莫唑胺的敏感性呈正相关（r=-0．576,P〈0．001）。结论：miR-181b在胶质瘤中的表达与胶质瘤的病理级别呈负相关．而与脑胶质瘤患者预后呈正相关．与高级别胶质瘤对替莫唑胺的敏感性呈正相关．     

肝癌体外药物敏感性试验

目的 通过测定肝癌对阿霉素（ADM）、顺铂（DDP）、氟尿嘧啶（FU）、长春新碱（VCR）、丝裂霉素C（MMC）及噻替哌（TSPA）的体外药物敏感性，为肝癌化疗用药提供参考依据。方法 采用滤纸支持组织块培养－MTT终点－计算机图像分析体外药物敏感性试验法。结果 在1倍血浆峰浓度（1 PPC）时作用最强的药物为MMC，其抑制率中位数（MIR）为26．5％，其次是ADM为13．0％，DDP、TSPA、5－FU和VCR为4．0－8．5％。在5倍血浆峰浓度（5PPC）时作用最强的药物亦为MMC，其MIR为92．0％，次为ADM、DDP和TSPA为41－50％，5－FU和VCR为16．0－17．0％，DDP和TSPA在5PPC的MIR比在1PPC时大5．0和5．8倍以上，MMC、ADM帮VCR则大2－3．5倍，5－FU只增大1倍左右。结论 结果提示MMC对肝癌抑制作用较强，DDP和TSPA剂量增加与疗效提高可能有较大的关系。天然来源的药物ADM、MMC和VCR之间，无论在1PPC或5PPC水平，其相关系数均较大（r=0.5539-0.7208)，表明部分肝癌具有多药耐药性。     

人脑胶质瘤原代细胞培养及体外药物敏感度的实验

目的 探索人脑胶质瘤细胞原代培养的方法,研究不同胶质瘤患者对抗肿瘤药物的敏感度。　方法 采用组织块培养法对39例人脑胶质瘤细胞进行原代培养,用MTT法检测胶质瘤细胞对阿霉素(ADM)、顺铂(DDP)、长春新碱(VCR) 、威猛(teniposide,VM 26)和5 氟尿嘧啶(5 Fu) 5种化疗药物的敏感度,并对其结果进行分析。结果 脑胶质瘤细胞原代培养37例成功,2例失败,成功率94.9%;37例培养成功者药敏检测显示不同个体对不同抗肿瘤药物的抑制率存在明显差异,各药物的平均抑制率依次为VM 26>DDP>5 Fu>ADM>VCR,其敏感率分别为56.8%、51.4%、37.8%、24.3%和13.5%。 结论 体外胶质瘤细胞原代培养和MTT法检测化疗药物的敏感度是可行的,检测化疗药物敏感度对胶质瘤患者个体化的化疗具有一定价值。     

Empirical studies about quercetin increasing chemosensitivity on human lung adenocarcinoma cell line A549

Objective

The present study was designed to investigate whether quercetin exerts increasing chemosensitivity on human lung adenocarcinoma cells when quercetin combined with cisplatin (DDP) and vincristine (VCR) in vitro respectively and its possible antitumor mechanism. To provide experimental proof for clinical combination application.

Methods

Using intermittent administration of high dose VCR, human lung adenocarcinoma sensitive cell line (A549/S) was induced to VCRresistant human lung adenocarcinoma cell line (A549/VCR). MTT assay was adapted for examing the 50% inhibition (IC₅₀) value of DDP and VCR on A549/S and A549/VCR when quercetin combined with DDP and VCR respectively.

Results

IC₅₀ of DDP on A549/S and A549/VCR was 10.18 and 12.35 mg/L, and the IC₅₀ of VCR on the two cell lines was 1.21 and 12.77 mg/L, respectively. The resistance fold of A549/VCR on VCR and DDP was 10.55 and 1.21, respectively. When quercetin at concentration of 50, 100 and 200 μmol/L in combination with DDP and VCR respectively, the IC₅₀ of DDP and VCR on A549/S and A549/VCR were obvious decreased (P < 0.05–P < 0.01).

Conclusion

The experiment results suggested that quercetin could increase the chemosensitivity and partly revise the resistance of A549/VCR.     

Gamma-radiation sensitivity and risk of glioma

BACKGROUND: About 9% of human cancers are brain tumors, of which 90% are gliomas. gamma-Radiation has been identified as a risk factor for brain tumors. In a previous pilot study, we found that lymphocytes from patients with glioma were more sensitive to gamma-radiation than were lymphocytes from matched control subjects. In this larger case-control study, we compared the gamma-radiation sensitivity of lymphocytes from glioma patients with those from control subjects and investigated the association between mutagen sensitivity and the risk for developing glioma. METHODS: We used a mutagen sensitivity assay (an indirect measure of DNA repair activity) to assess chromosomal damage. We gamma-irradiated (1.5 Gy) short-term lymphocyte cultures from 219 case patients with glioma and from 238 healthy control subjects frequency matched by age and sex. After irradiation, cells were cultured for 4 hours, and then Colcemid was added for 1 hour to arrest cells in mitosis. Fifty metaphases were randomly selected for each sample and scored for chromatid breaks. All statistical tests were two-sided. RESULTS: We observed a statistically significantly higher frequency of chromatid breaks per cell from case patients with glioma (mean = 0.55; 95% confidence interval [CI] = 0.50 to 0.59) than from control subjects (mean = 0.44; 95% CI = 0.41 to 0.48) (P<.001). Using 0.40 (the median number of chromatid breaks per cell in control subjects) as the cut point for defining mutagen sensitivity and adjusting for age, sex, and smoking status, we found that mutagen sensitivity was statistically significantly associated with an increased risk for glioma (odds ratio = 2.09; 95% CI = 1.43 to 3.06). When the data were divided into tertiles, the relative risk for glioma increased from the lowest tertile to the highest tertile (trend test, P<.001). CONCLUSION: gamma-Radiation-induced mutagen sensitivity of lymphocytes may be associated with an increased risk for glioma, a result that supports our earlier preliminary findings.     

RNA干扰技术逆转神经胶质瘤细胞多药耐药性

目的 探讨利用RNA干扰（RNAi）技术逆转神经胶质瘤细胞多药耐药性。方法 根据多药耐药基因1（MDR1）的碱基序列设计并合成短发夹RNA（shRNA）,构建逆转录病毒质粒载体,用阳离子脂质体法体外转染BT325细胞株,以增强型绿色荧光蛋白（EGFP）表达作为对照。采用定量PCR、Northern blot检测转染前后MDR1 mRNA的表达,Western blot检测蛋白表达;使用CCK-8试剂盒对转染后的细胞进行化疗药物敏感性试验,评价RNAi对多药耐药性的逆转作用。结果 成功构建RNAi质粒载体。共转染实验组RT-PCR定量MDR1 mRNA相对表达水平均有所下降（P〈0．05）;Northern blot表明,转染48h细胞干扰最强;Western blot显示,siRNA各转染组P-糖蛋白（P-gp）的表达分别降低12．9％、30．3％和4．8％,在48h抑制最强;而药物敏感试验显示,转染siRNA后细胞对药物的敏感性明显增强。结论 RNAi能够明显抑制神经胶质瘤细胞系MDR1 mRNA和P-gp蛋白的表达,进而对多药耐药性发挥明显的逆转作用,为基因治疗提供了一种新的手段。     

Serum Levels of APRIL Increase in Patients with Glioma,Meningioma and Schwannoma

Objective: Brain tumors are of high mortality and morbidity for which there is still no cure. The TNF family cytokine,A Proliferation Inducing Ligand (APRIL), is shown to help proliferation and development of tumor cells. We assessedserum levels of APRIL in patients with glioma, meningioma and schwannoma in comparison to healthy individuals.Methods: Peripheral blood samples of 68 patients with brain tumors, divided into three groups of gliomas (n=25),meningiomas (n=30) and schwannomas (n=13), as well as 45 healthy individuals were obtained. Serum samples wereprepared and stored in -40°C until usage. Using a commercial ELISA method, APRIL concentration was measured ineach serum sample. The obtained data were then analyzed using SPSS software. Results: APRIL serum levels werehigher in all patients compared to the controls (P<0.001). Moreover, APRIL serum levels were higher in each of thetumor bearing groups (gliomas, meningiomas and schwannomas) in comparison to the controls (P<0.001, <0.001and =0.001, respectively). Comparing APRIL between the patients groups showed no significant difference. Age andgender showed no significant correlation with serum APRIL levels, although the age of patients in glioma group wassignificantly lower than controls (P=0.017). The serum APRIL levels in gliomas with histological grade showed nodifference, but in meningiomas, it was lower in tumors with higher grades (P= 0.011). Conclusion: Increased serumlevels of APRIL in patients with meningioma and schwannoma as well as glioma may indicate a common role of thiscytokine in brain tumors.     

DNA-PK inhibition by NU7441 sensitizes breast cancer cells to ionizing radiation and doxorubicin

DNA-dependent protein kinase (DNA-PK) plays a key role in the repair of DNA double-strand breaks (DSBs) that are probably the most deleterious form of DNA damage. Inhibition of DNA-PK has been considered as an attractive approach to decrease resistance to therapeutically induced DNA DSBs. Ionizing radiation (IR) and doxorubicin, which induce DSBs, are used in the treatment of breast cancer. We determined the cellular concentration of DNA-PK and other DSB-activated kinases: ATM and ATR and the effect of DNA-PK inhibition by NU7441 on DNA repair, cell cycle, and survival after IR or doxorubicin treatment in three human breast cancer cell lines (MCF-7, MDA-MB-231, and T47D) representing different breast cancer subtypes. T47D cells had the highest expression of DNA-PKcs, ATM, and ATR and the most rapid rate of DNA DSB repair. IR caused a 10- to 16-fold increase in DNA-PK activity and two to threefold induction of ATM in all 3 cell lines. NU7441 inhibited IR-induced DNA-PK activity in all cell lines with IC₅₀s in the range 0.17–0.25 μM. NU7441 retarded the repair of DSB and significantly increased the sensitivity of all cell lines to IR (4- to 12-fold) and doxorubicin (3- to 13-fold). The greatest sensitiziation by NU7441 was observed in MDA-MB-231 cells. NU7441 affected the cell cycle distribution in all studied cell lines; increasing accumulation of cells in G2/M phase after DNA damage. Our data indicate that DNA-PK might be an effective target for chemo- and radio-potentiation in breast cancer and suggest that further development of DNA-PK inhibitors for clinical use is warranted.     

Inhibition of the DNA-dependent protein kinase catalytic subunit radiosensitizes malignant glioma cells by inducing autophagy

DNA-dependent protein kinase (DNA-PK) plays a major role in the repair of DNA double-strand breaks induced by ionizing radiation (IR). Lack of DNA-PK causes defective DNA double-strand break repair and radiosensitization. In general, the cell death induced by IR is considered to be apoptotic. On the other hand, nonapoptotic cell death, autophagy, has recently attracted attention as a novel response of cancer cells to chemotherapy and IR. Autophagy is a protein degradation system characterized by a prominent formation of double-membrane vesicles in the cytoplasm. Little is known, however, regarding the relationship between DNA-PK and IR-induced autophagy. In the present study, we used human malignant glioma M059J and M059K cells to investigate the role of DNA-PK in IR-induced apoptotic and autophagic cell death. Low-dose IR induced massive autophagic cell death in M059J cells that lack the catalytic subunit of DNA-PK (DNA-PKcs). Most M059K cells, the counterpart of M059J cells in which DNA-PKcs are expressed at normal levels, survived, and proliferated although a small portion of the cells underwent apoptosis. Low-dose IR inhibited the phosphorylation of p70(S6K), a molecule downstream of the mammalian target of rapamycin associated with autophagy in M059J cells but not in M059K cells. The treatment of M059K cells with antisense oligonucleotides against DNA-PKcs caused radiation-induced autophagy and radiosensitized the cells. Furthermore, antisense oligonucleotides against DNA-PKcs radiosensitized other malignant glioma cell lines with DNA-PK activity, U373-MG and T98G, by inducing autophagy. The specific inhibition of DNA-PKcs may be promising as a new therapy to radiosensitize malignant glioma cells by inducing autophagy.     

DNA double-strand break repair,DNA-PK,and DNA ligases in two human squamous carcinoma cell lines with different radiosensitivity

Purpose: Variation in sensitivity to radiotherapy among tumors has been related to the capacity of cells to repair radiation-induced DNA double-strand breaks (DSBs). DNA-dependent protein kinase (DNA-PK) and DNA ligases may affect DNA dsb rejoining. This study was performed to compare rate of rejoining of radiation-induced DSBs, DNA-PK, and DNA ligase activities in two human squamous carcinoma cell lines with different sensitivity to ionizing radiation.Methods and Materials: Cell survival of two human squamous carcinoma cell lines, UM-SCC-1 and UM-SCC-14A, was determined by an in vitro clonogenic assay. DSB rejoining was studied using pulsed field gel electrophoresis (PFGE). DNA-PK activity was determined using BIOTRAK DNA-PK enzyme assay system (Amersham). DNA ligase activity in crude cell extracts was measured using [5′-³³P] Poly (dA)·(oligo (dT) as a substrate. Proteolytic degradation of proteins was analyzed by means of Western blotting.Results: Applying the commonly used linear-quadratic equation to describe cell survival, S = e^-αD-βD2, the two cell lines roughly have the same α value (∼0.40 Gy^-1) whereas the β value was considerably higher in UM-SCC-14A (0.067 Gy^-2 ± 0.007 Gy^-2 [SEM]) as compared to UM-SCC-1 (0.013 Gy^-2 ± 0.004 Gy^-2 [SEM]). Furthermore, UM-SCC-1 was more proficient in rejoining of X-ray-induced DSBs as compared to UM-SCC-14A as quantified by PFGE. The constitutive level of DNA-PK activity was 1.6 times higher in UM-SCC-1 as compared to UM-SCC-14A (p < 0.05). The constitutive level of DNA ligase activity was similar in the two cell lines.Conclusions: The results suggest that the proficiency in rejoining of DSBs is associated with DNA-PK activity but not with total DNA ligase activity.