奥沙利铂调控PI3K/Akt信号通路抑制脑胶质瘤细胞株U87生长的作用研究

目的：研究奥沙利铂（Oxaliplatin,Ox）调控PI3K/Akt信号通路抑制脑胶质瘤细胞株U87生长的作用。方法：培养U87脑胶质瘤细胞,分别利用0、20、40、80 μg/ml的奥沙利铂处理U87细胞24、36、48、72 h,利用MTT检测各处理组细胞增殖情况;利用流式细胞仪检测40 μg/ml的奥沙利铂处理48 h对U87细胞周期及细胞凋亡的影响;Western blot检测40 μg/ml 的奥沙利铂处理48 h对U87细胞凋亡相关蛋白及PI3K/Akt信号通路蛋白表达的影响。结果：奥沙利铂处理抑制U87细胞增殖,与0 μmol/L处理相比,差异显著（P<0.01）,40 μg/ml的奥沙利铂处理48 h差异最显著。40 μg/ml的奥沙利铂处理48 h后,U87细胞周期被阻滞在S期,U87细胞凋亡显著增加（P<0.01）,抑凋亡因子Bcl-2蛋白表达明显下降,促凋亡因子Bax、Cleaved-caspase3蛋白表达明显升高（P<0.01）,PI3K及p-Akt的表达量明显降低（P<0.01）,Akt表达量无明显差异（P>0.05）。结论：奥沙利铂可能通过抑制PI3K/Akt信号通路抑制U87细胞增殖,阻滞细胞周期,促进细胞凋亡。     

ARHI基因抑制U937白血病细胞株生长并诱导其G_2/M期阻滞及凋亡

目的:探讨抑癌基因ARHI在急性髓细胞白血病中的表达情况,同时探索其对U937细胞生长的影响。方法:RT-PCR方法检测急性髓细胞白血病细胞株、人胚肾细胞293FT、白血病原代细胞以及健康志愿者血细胞中ARHI mRNA的表达情况。构建高表达ARHI的MSCV-IRES-GFP-ARHI质粒转染U937细胞,MTT法连续8 d检测细胞活性绘制生长曲线。新鲜培养基重悬U937细胞24 h后,采用流式细胞术检测细胞周期以及细胞凋亡。结果:293FT细胞、健康志愿者血细胞中均检测到ARHI mRNA表达,而白血病细胞株以及白血病患者原代细胞中未检测到该基因的表达。生长曲线显示高表达ARHI基因的U937(U937-ARHI)细胞在第6~8天细胞活力低于对照(U937-GFP)组。高表达ARHI的U937细胞G2/M期细胞比例及细胞凋亡率均高于对照组(P0.05)。结论:ARHI在急性髓系白血病细胞中的表达减低;高表达ARHI基因能抑制U937细胞生长、阻滞其细胞周期在G2/M期并促进细胞凋亡。     

抑制Hedgehog信号通路对脑胶质瘤U87细胞增殖及凋亡的影响

目的研究Hedgehog(Hh)信号通路阻断剂环王巴明对脑胶质瘤U87细胞增殖及凋亡的影响。方法体外培养U87细胞,以10、50、100μmol/L的环王巴明作用24h,MTT法检测环王巴明对U87细胞增殖的影响,流式细胞技术检测环王巴明对U87细胞凋亡的影响,RT-PCR检测环王巴明对U87细胞Gli-1 mRNA表达的变化,Western blot检测环王巴明对U87细胞Gli-1蛋白表达的变化。结果 MTT检测结果表明10μmol/L环王巴明组(85.11±2.61)%、50μmol/L环王巴明组(76.81±3.13)%和100μmol/L环王巴明组(69.20±4.11)%细胞活性较空白对照组(99.87±0.21)%降低(P0.05);流氏细胞技术检测结果表明10μmol/L环王巴明组(15.22±0.21)%、50μmol/L环王巴明组(24.87±0.24)%和100μmol/L环王巴明组(31.36±0.26)%细胞总凋亡率较空白对照组(2.66±0.28)%升高(P0.05);RT-PCR检测结果表明10μmol/L环王巴明组(0.68±0.06)%、50μmol/L环王巴明组(0.48±0.06)%和100μmol/L环王巴明组(0.30±0.06)%Gli-1mRNA表达水平较空白对照组(0.92±0.11)%降低(P0.05);Western blot检测结果表明10μmol/L环王巴明组(0.78±0.06)%、50μmol/L环王巴明组(0.58±0.05)%和100μmol/L环王巴明组(0.40±0.04)%Gli-1蛋白表达水平较空白对照组(0.94±0.11)%降低(P0.05)。结论Hedgehog信号通路阻断剂环王巴明可以抑制脑胶质瘤U87细胞增殖、诱导U87细胞凋亡,其作用机制可能与下调GLi-1表达有关。     

MACC1基因在脑胶质瘤中的表达及其对U87细胞凋亡和增殖的影响

目的 探讨MACC1基因与脑胶质瘤的相关性及其表达改变对胶质瘤U87细胞凋亡和增殖能力的影响.方法 荧光定量PCR检测45例脑胶质瘤及相应癌旁组织MACC1基因的表达;设计并合成MACC1基因特异性的siRNA,转染U87细胞;Western blot检测转染后MACCI蛋白的表达;双标流式细胞法检测细胞凋亡;MTT法...     

MACC1表达沉默对胶质瘤细胞U87增殖凋亡的影响

目的探讨MACC1基因表达沉默对脑胶质瘤细胞U87增殖凋亡的影响。方法应用RT-PCR和Western blot检测55例不同病理级别胶质瘤标本MACC1表达;转染MACC1siRNA到U87细胞沉默MACC1基因表达,Western blot检测MACC1,Bcl-2/Bax,caspase-3,c-Met蛋白的表达;MTT法检测细胞生长增殖能力;流式细胞术检测细胞周期及凋亡情况。结果MACC1基因在胶质瘤标本组织表达随病理级别升高而增多;MACC1表达沉默后U87生长增殖能力明显下降,细胞周期阻滞于G0/G1期,细胞凋亡显著增加,MACC1蛋白表达明显下降,Bcl-2/Bax比值降低,caspase-3表达上调,c-Met表达下降。结论下调MACC1表达可促进胶质瘤细胞凋亡,抑制肿瘤细胞增殖,MACC1可能成为胶质瘤基因治疗的新靶点。     

抑癌基因PTEN诱导人脑胶质瘤SHG—44细胞凋亡

目的 研究外源性PTEN基因对人脑胶质瘤细胞系SHG－44凋亡的影响,探讨PTEN基因抑制肿瘤细胞增殖的机制。方法 以携有人PTEN基因的真核表达载体体外转染SHG－44细胞,筛选阳性转染的细胞克隆并扩增培养。以原位杂交和免疫组化染色法检测PTEN基因的表达。采用透射电镜、流式细胞仪和核DNA琼脂糖凝胶电泳,检测转染PTEN基因后SHG－44胶质细胞的凋亡。观察导入入PTEN基因对SHG－44细胞裸鼠致瘤能力的影响。结果 获得PTEN基因稳定转染的胶质瘤细胞SHG－44,并检测到PTEN基因和蛋白的表达。透射电镜下可见转染PTEN基因后细胞核染色质浓缩边集、胞浆浓缩、核碎裂及凋亡小体形成等典型的凋亡表面。流式细胞仪显示,细胞周期从G1期到S期发生抑制,并在G1期峰前出现1个明显的凋亡峰（12．9％）。细胞核DNA琼脂糖凝胶电泳显示凋亡细胞特朋的梯状条带。转染空载体及未转染的SHG－44细胞未见的凋亡表现。转染PTEN基因后,SHG－44细胞对裸鼠瘤能力明显降低。结论 将外源必PTEN基因导入SHG－44肿瘤细胞后,可诱导细胞凋亡,这可能是PTEN基因抑制肿瘤细胞增殖的重要机制之一。     

金雀异黄素对胶质瘤细胞株U251MG凋亡的影响

目的 研究金雀异黄素(Genistein)对人胶质瘤U251MG细胞凋亡的影响及机制.方法 碘化丙啶(propidium iodide,PI)和Annexin V-FITC双染色的流式细胞分析方法检测凋亡,并通过流式细胞仪和免疫细胞化学染色检测Bcl-2、bax蛋白的表达.结果 Genistein在25 μg/ml和50 μg/ml作用48 h后,早期凋亡率均较对照组明显增加(P<0.01),并呈剂量依赖性.Bcl-2蛋白表达较对照组明显下降(P<0.01),而bax蛋白则较对照组明显增加(P<0.01),呈剂量依赖性.结论 Genistein可诱导胶质瘤U251MG细胞凋亡,其机制可能与其上调bax蛋白以及下调Bcl-2蛋白的表达有关.     

针对B7-H1的siRNA对脑胶质瘤U87细胞增殖和凋亡的影响

目的:利用针对B7-H1的siRNA在脑胶质瘤U87细胞中下调B7-H1的表达,研究B7-H1的表达下调对U87细胞增殖和凋亡的影响。方法:根据人B7-H1的mRNA序列设计并合成两对针对B7-H1的siRNA,于转染前一天将U87细胞接种于10 cm细胞培养皿中,以转染时细胞融合度为50%-80%为宜,分别用250μl OPTI-MEM稀释15μl siRNA与15μl转染试剂Lipofectamine 2000,将两者混匀室温静置20 min后,滴入细胞培养皿中。转染60或72 h后利用流式细胞术检测B7-H1在细胞表面的表达情况,利用荧光定量PCR和Western Blot分别检测B7-H1的mRNA和蛋白质水平,并用MTT和流式细胞术检测B7-H1表达下调后,U87细胞增殖和凋亡的改变。结果:与阴性对照组相比,两对针对B7-H1的siRNA均可有效下调U87细胞中B7-H1的表达,流式细胞术结果显示与阴性对照组相比,B7-H1阳性表达率由53.2%分别下调至26.7%和20.6%;MTT结果显示B7-H1表达下调后U87细胞的增殖被显著抑制,培养第5天吸光度值由0.58±0.02分别下降至0.451±0.02及0.342±0.016;流式细胞术结果显示B7-H1表达下调后U87细胞凋亡明显,早期凋亡率由0.1%分别增加至12.8%及13.2%。结论:B7-H1的表达下调可有效抑制脑胶质瘤U87细胞的增殖,并促进细胞凋亡,提示B7-H1可能作为脑胶质瘤基因治疗的一个潜在靶点。     

二氯乙酸盐DCA对神经胶质瘤细胞U87影响的体外研究

目的研究二氯乙酸盐(dichloroacetate,DCA)对神经胶质瘤细胞U87的生物学行为的影响及可能机制,探讨DCA与脑恶性肿瘤治疗之间的关系。方法神经胶质瘤细胞U87在DCA的干预下,通过MTT实验检测细胞生长能力,平板克隆形成实验检测细胞增殖能力,Western blotting检测caspase-3、bcl-2、bax、AC-tubulin的表达变化,荧光共聚焦实验进行AC-tubulin检测分析。结果 DCA对于U87细胞生长具有明显的抑制作用,抑制胶质瘤细胞克隆能力,进而抑制细胞增殖,促进U87细胞的凋亡,并且使AC-tubulin的表达明显增高,DCA使U87细胞阻滞在G0/G1期。结论 DCA抑制并杀伤胶质瘤细胞,在胶质瘤的未来治疗过程中,很可能成为治疗一类新药物。     

17-AAG阻滞HCT-15细胞周期并诱导其凋亡

目的:观察17-AAG对人结直肠癌HCT-15细胞株凋亡和周期及相关分子机制的影响。方法:体外培养HCT-15细胞,分别给予不同剂量的17-AAG及不同作用时间,采用四甲基偶氮唑盐微量酶反应比色法(MTT法)检测细胞的活力;Annexin V-FITC/PI双标记流式细胞术检测细胞凋亡;流式细胞术检测细胞周期的变化;RTPCR和Western blotting法检测凋亡和周期相关因子的表达水平。结果:1.25~20 mg/L浓度的17-AAG作用24 h和48 h后对HCT-15细胞有显著抑制作用,且有明显的时间、剂量依赖性;0.425、0.85和1.7 mg/L浓度的17-AAG作用48 h后,各组细胞发生G1期阻滞及明显凋亡,STAT3 mRNA和蛋白的表达水平明显下降,凋亡和周期相关因子cyclin D1 mRNA和蛋白表达水平下调,Cyt C、caspase 9及caspase 3 mRNA和蛋白表达水平上调。结论:17-AAG对人结直肠癌细胞的活力具有明显抑制作用,使细胞周期发生G1期阻滞和细胞凋亡。17-AAG可能通过阻断STAT3通路下调cyclin D1而发生G1期阻滞;17-AAG可能通过阻断STAT3通路启动线粒体凋亡通路来诱导细胞凋亡。     

Kaurene diterpene induces apoptosis in U87 human malignant glioblastoma cells by suppression of anti-apoptotic signals and activation of cysteine proteases

Gliomas are the most common and malignant primary brain tumors in humans. Studies have shown that classes of kaurene diterpene have anti-tumor activity related to their ability to induce apoptosis. We investigated the response of the human glioblastoma cell line U87 to treatment with ent-kaur-16-en-19-oic acid (kaurenoic acid, KA). We analyzed cell survival and the induction of apoptosis using flow cytometry and annexin V staining. Additionally, the expression of anti-apoptotic (c-FLIP and miR-21) and apoptotic (Fas, caspase-3 and caspase-8) genes was analyzed by relative quantification (real-time PCR) of mRNA levels in U87 cells that were either untreated or treated with KA (30, 50, or 70 µM) for 24, 48, and 72 h. U87 cells treated with KA demonstrated reduced viability, and an increase in annexin V- and annexin V/PI-positive cells was observed. The percentage of apoptotic cells was 9% for control cells, 26% for cells submitted to 48 h of treatment with 50 µM KA, and 31% for cells submitted to 48 h of treatment with 70 µM KA. Similarly, in U87 cells treated with KA for 48 h, we observed an increase in the expression of apoptotic genes (caspase-8, -3) and a decrease in the expression of anti-apoptotic genes (miR-21 and c-FLIP). KA possesses several interesting properties and induces apoptosis through a unique mechanism. Further experiments will be necessary to determine if KA may be used as a lead compound for the development of new chemotherapeutic drugs for the treatment of primary brain tumors.     

唑来膦酸抑制U937细胞增殖及诱导凋亡

目的:研究唑来膦酸(ZOL)对人类急性髓系白血病细胞U937的增殖抑制及促凋亡作用。方法:CCK-8法检测不同时间ZOL对U937细胞的生长抑制率;流式细胞术检测ZOL对U937细胞周期的影响;Annexin V-PI法及Hoechst 33342法检测ZOL作用前后细胞凋亡情况变化,JC-1检测ZOL对U937细胞线粒体膜电位变化的影响;克隆形成实验检测U937细胞克隆形成能力;Western blot法检测ZOL对U937细胞周期和凋亡相关蛋白的变化。结果:CCK-8结果显示ZOL可以抑制U937细胞的活力,并呈时间-剂量依赖性;Annexin V-PI及Hoechst33342结果显示ZOL可以促进U937细胞凋亡,且呈时间-剂量依赖性;JC-1结果显示ZOL可以明显降低U937细胞线粒体膜电位;PI法证实ZOL将U937细胞周期阻滞在S期,克隆形成实验证实0.2 mmol/L ZOL可以完全抑制U937细胞的克隆形成能力;Western blot结果显示ZOL作用于U937细胞48 h后细胞周期相关蛋白p21表达显著增强,促凋亡蛋白Bax表达增强,抑凋亡蛋白Bcl-2表达明显减弱。结论:ZOL抑制U937细胞的增殖和克隆形成主要是由于抑制了细胞周期相关蛋白表达,同时ZOL可以促进U937细胞凋亡,这种作用主要是通过调节线粒体凋亡途径相关蛋白来实现的。     

土荆皮乙酸促进喉癌细胞系HEp-2凋亡

目的本文观察土荆皮乙酸(PAB)对人喉表皮样癌细胞系2(HEp-2)的增殖和凋亡的影响。方法细胞分组及处理:以0、0.5、1、2、4、8和16μmol/L的PAB分别处理细胞24、48和72 h;MTT法检测细胞活性;流式细胞仪检测细胞凋亡;Western blot和qPCR检测细胞Bcl-2、Bax和caspase-3蛋白及mRNA表达;免疫组化检测细胞PARP和c-PARP蛋白的表达。结果 PAB呈时间-浓度依赖性抑制HEp-2增殖。与对照组比较,4和8μmol/L PAB组HEp-2细胞凋亡率均显著升高(P<0.01);4和8μmol/L PAB组HEp-2细胞的Bcl-2和PARP表达均显著下降(P<0.05);Bax、caspase-3和c-PARP的表达均显著升高(P<0.05)。结论 PAB可激活线粒体凋亡途径,诱导HEp-2细胞凋亡。     

Saturated free fatty acid, palmitic acid, induces apoptosis in fetal hepatocytes in culture

To investigate the effects of saturated free fatty acid, palmitic acid (PA), on hepatocytes, we administered PA to rat hepatocytes. We demonstrated that PA inhibited the cell growth as a dose- and time-dependent manner in rat hepatocytes. PA-induced morphological changes including swelling, membrane dissolution and formation of debris, and apoptosis with appearance of sub-G1 fraction determined by cell cycle analysis after treatment for 4 days. The level of Bcl-2 was slightly decreased, in contrast, the level of Bax elevated markedly, which resulted in a significant decrease of Bcl-2/Bax ratio after PA treatment on HepG2 cells. These findings demonstrated that PA induces cell death on hepatocytes, perhaps via mitochondria-mediated apoptosis. Furthermore, the present study indicates that PA's cell toxicity may play important roles in the transition from steatosis to steatohepatitis in human especially with obesity.     

5-Aminolevulinic acid-based photodynamic therapy suppressed survival factors and activated proteases for apoptosis in human glioblastoma U87MG cells

Glioblastoma is the most common astrocytic brain tumor in humans. Current therapies for this malignancy are mostly ineffective. Photodynamic therapy (PDT), an exciting treatment strategy based on activation of a photosensitizer, has not yet been extensively explored for treating glioblastoma. We used 5-aminolevulinic acid (5-ALA) as a photosensitizer for PDT to induce apoptosis in human malignant glioblastoma U87MG cells and to understand the underlying molecular mechanisms. Trypan blue dye exclusion test showed a decrease in cell viability after exposure to increasing doses of 5-ALA for 4h followed by PDT with a broad spectrum blue light (400-550 nm) at a dose of 18J/cm(2) for 1h and then incubation at 37 degrees C for 4h. Following 0.5 and 1mM 5-ALA-based PDT (5-ALA-PDT), Wright staining and ApopTag assay showed occurrence of apoptosis morphologically and biochemically, respectively. After 5-ALA-PDT, down regulation of nuclear factor kappa B (NFkappaB) and baculovirus inhibitor-of-apoptosis repeat containing-3 (BIRC-3) protein indicated inhibition of survival signals. Besides, 5-ALA-PDT caused increase in Bax:Bcl-2 ratio and mitochondrial release of cytochrome c and apoptosis-inducing factor (AIF). Activation of calpain, caspase-9, and caspase-3 occurred in course of apoptosis. Calpain and caspase-3 activities cleaved alpha-spectrin at specific sites generating 145kD spectrin breakdown product (SBDP) and 120kD SBDP, respectively. The results suggested that 5-ALA-PDT induced apoptosis in U87MG cells by suppression of survival signals and activation of proteolytic pathways. Thus, 5-ALA-PDT can be an effective strategy for inducing apoptosis in glioblastoma.     

蓝萼香茶菜乙素对AGZY细胞周期及凋亡的影响

目的:研究蓝萼香茶菜乙素对AGZY细胞周期及细胞凋亡的影响。方法:MTT法测定蓝萼香茶菜乙素对AGZY的细胞毒作用;PI染色、流式细胞术观察蓝萼香茶菜乙素对AGZY细胞周期及细胞凋亡的影响。结果:蓝萼香茶菜乙素对AGZY细胞的IC50为0.11mmol/L,且随着蓝萼香茶菜乙素剂量增加对AGZY细胞抑制作用增强;蓝萼香茶菜乙素可以降低AGZY细胞G2/M期细胞数量,阻止细胞分裂。结论:蓝萼香茶菜乙素可阻滞AGZY细胞的生长,阻滞细胞进入G2/M期,并诱导AGZY细胞凋亡。     

组蛋白去乙酰化酶抑制剂与细胞周期和凋亡关系的研究进展

表观遗传学是目前遗传学研究的热点。组蛋白乙酰化修饰是一种重要的表观遗传学调控方式,参与调控染色质构象变化和转录表达过程,组蛋白乙酰化状态紊乱与肿瘤的发生发展关系密切。研究发现,组蛋白去乙酰化酶抑制剂(histone deacetylase in-hibitor,HDACi)可以纠正肿瘤细胞异常的乙酰化状态,诱导肿瘤细胞发生细胞周期停滞和凋亡,逆转肿瘤细胞恶性表型。1组蛋白乙酰化酶(histone acetyltransferase,HAT)和组蛋白去乙酰化酶(histone deacetylase,HDAC)真核生物染色体的基本单位是核小体,核小体的核心是由4种组蛋白(H2A、H2B、H3和H4)各2…     

姜黄素类似物B67诱导细胞凋亡和G2/M期 阻滞增强对鼻咽癌辐射抗拒细胞的抑制作用

目的: 研究姜黄素类似物B67对鼻咽癌(NPC)辐射抗拒细胞(CNE-2R)活性和增殖的作用,及其对细胞周期和凋亡的影响。方法: 采用MTT和平板克隆形成实验检测B67对CNE-2R细胞及其母细胞CNE-2活性和增殖的抑制作用,采用荧光显微镜和流式细胞仪观测凋亡细胞的形态学变化、细胞凋亡百分率、细胞周期分布和线粒体膜电位的改变,采用裸鼠皮下成瘤实验检验B67作用于CNE-2R细胞后的成瘤性。 结果: B67作用于NPC细胞24、48和72 h后,MTT检测细胞活性的IC₅₀分别为3.96、2.59和0.89 μmol/L(CNE-2R)以及8.84、3.55和1.10 μmol/L(CNE-2),B67作用48 h后平板克隆形成实验检测NPC细胞增殖的IC₅₀分别为0.55 μmol/L(CNE-2R)和0.73 μmol/L(CNE-2),B67作用24 h后NPC细胞的G₂/M期比例的上升分别为5.32%上升到40.01%(CNE-2R)和9.07%上升到15.73%(CNE-2),B67作用48 h后NPC细胞凋亡率的改变分别为5.49%上升到38.06%(CNE-2R)和4.99%上升到35.74%(CNE-2),B67作用48 h后NPC细胞线粒体膜电位的下降分别为66.76%(CNE-2R)和72.09%(NE-2),B67作用24 h后NPC细胞在裸鼠皮下的成瘤率分别为0%(CNE-2R)以及低浓度组100%、高浓度组0%(CNE-2)。 结论: 姜黄素类似物B67可较特异地诱导CNE-2R细胞G₂/M期阻滞和促进细胞凋亡和线粒体膜电位的改变,引起裸鼠皮下成瘤性的差异,以增强其对鼻咽癌辐射抗拒细胞的抑制作用。     

Juniperus communis extract induces cell cycle arrest and apoptosis of colorectal adenocarcinoma in vitro and in vivo

Juniperus communis (JCo) is a well-known traditional Chinese medicinal plant that has been used to treat wounds, fever, swelling, and rheumatism. However, the mechanism underlying the anticancer effect of JCo extract on colorectal cancer (CRC) has not yet been elucidated. This study investigated the anticancer effects of JCo extract in vitro and in vivo as well as the precise molecular mechanisms. Cell viability was evaluated using the MTT assay. Cell cycle distribution was examined by flow cytometry analysis, and cell apoptosis was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Protein expression was analyzed using western blotting. The in vivo activity of the JCo extract was evaluated using a xenograft BALB/c mouse model. The tumors and organs were examined through hematoxylin-eosin (HE) staining and immunohistochemistry. The results showed that JCo extract exhibited higher cytotoxicity against CRC cells than against normal cells and showed synergistic effects when combined with 5-fluorouracil. JCo extract induced cell cycle arrest at the G₀/G₁ phase via regulation of p53/p21 and CDK4/cyclin D1 and induced cell apoptosis via the extrinsic (FasL/Fas/caspase-8) and intrinsic (Bax/Bcl-2/caspase-9) apoptotic pathways. In vivo studies revealed that JCo extract suppressed tumor growth through the inhibition of proliferation and induction of apoptosis. In addition, there was no obvious change in body weight or histological morphology of normal organs after treatment. JCo extract suppressed CRC progression by inducing cell cycle arrest and apoptosis in vitro and in vivo, suggesting the potential application of JCo extract in the treatment of CRC.