Expression analysis of cystatin C and M in laser-capture microdissectioned human breast cancer cells--a preliminary study

Cathepsins B and L, implicated in the progression of malignant tumors, are regulated by a family of endogenous inhibitors referred to as the cystatins. Cystatin M was identified by differential display as down-regulated gene in metastatic breast cancer cells. However, this finding has yet to be confirmed in clinical breast cancer specimens. Our objective is to examine the expression levels of cystatins C, M, and cathepsins B and L mRNA in breast cancer cells isolated by laser capture microdissection. The mRNA and protein levels of cathepsin B, L, and cystatin C and M in breast cancer specimens were determined utilizing laser capture microdissection/RT-PCR, Western blotting, and immunohistochemical methods. Expression levels of either cystatin M or C were not significantly different between lymph node-positive and -negative breast carcinomas. Increased expression levels of both cystatin M and C correlated significantly with larger tumor size. Cystatin M mRNA was detected by in situ hybridization in both primary and metastatic breast cancer cells. Our findings are at variance with a previous report proposing a metastasis suppressive function for cystatin M. Therefore, additional studies in a larger series with adequate follow-up are necessary to elucidate the biologic significance of cystatin M expression in breast cancer metastasis.     

Cell culture model predicts human disease: Altered expression of junction proteins and matrix metalloproteinases in cervical dysplasia

Background

LAT1/4F2hc heterodimeric complex is a major route for the transport of large neutral essential amino acids through the plasma membrane. Although it has been shown that LAT1/4F2hc is highly expressed in a variety of human tumors including gliomas, and LAT1 over-expression is associated with glioma grade and poor prognosis of glioma patients, the precise tissue location of LAT1/4F2hc in gliomas and the precise role of LAT1/4F2hc in glioma biological features remain unclear.

Methods

In the current study, the expressions of LAT1, 4F2hc, CD34 and Ki-67 were investigated by immunohistochemistry in 62 cases of human brain glioma; LAT1/4F2hc expression level, Ki-67 labeling index (Ki-67 LI) and microvessel density (MVD) were measured semi-quantitatively; and the correlation of LAT1/4F2hc expression with histopathological features, Ki-67 LI and MVD in gliomas was further analyzed.

Results

The results showed that both LAT1 and 4F2hc were expressed in all examined specimens. LAT1 but 4F2hc expression levels significantly correlated with the pathological grade and both expression levels significantly correlated with Ki-67 LI of gliomas. We also demonstrated that both LAT1 and 4F2hc immunoreactivity were observed in tumor cells as well as vascular endothelia; furthermore, the LAT1 expression level was markedly associated with glioma MVD as well.

Conclusion

LAT1/4F2hc over-expression is closely correlates with the malignant phenotype and proliferation of gliomas, and LAT1 was associates with glioma angiogenesis. LAT1/4F2hc, especially LAT1, may become a novel potential molecular target for glioma biological therapy.     

Invasion suppressor cystatin E/M (CST6): high-level cell type-specific expression in normal brain and epigenetic silencing in gliomas

DNA hypermethylation-mediated gene silencing is a frequent and early contributor to aberrant cell growth and invasion in cancer. Malignant gliomas are the most common primary brain tumors in adults and the second most common tumor in children. Morbidity and mortality are high in glioma patients because tumors are resistant to treatment and are highly invasive into surrounding brain tissue rendering complete surgical resection impossible. Invasiveness is regulated by the interplay between secreted proteases (eg, cathepsins) and their endogenous inhibitors (cystatins). In our previous studies we identified cystatin E/M (CST6) as a frequent target of epigenetic silencing in glioma. Cystatin E/M is a potent inhibitor of cathepsin B, which is frequently overexpressed in glioma. Here, we study the expression of cystatin E/M in normal brain and show that it is highly and moderately expressed in oligodendrocytes and astrocytes, respectively, but not in neurons. Consistent with this, the CST6 promoter is hypomethylated in all normal samples using methylation-specific PCR, bisulfite genomic sequencing, and pyrosequencing. In contrast, 78% of 28 primary brain tumors demonstrated reduced/absent cystatin E/M expression using a tissue microarray and this reduced expression correlated with CST6 promoter hypermethylation. Interestingly, CST6 was expressed in neural stem cells (NSC) and markedly induced upon differentiation, whereas a glioma tumor initiating cell (TIC) line was completely blocked for CST6 expression by promoter methylation. Analysis of primary pediatric brain tumor-derived lines also showed CST6 downregulation and methylation in nearly 100% of 12 cases. Finally, ectopic expression of cystatin E/M in glioma lines reduced cell motility and invasion. These results demonstrate that epigenetic silencing of CST6 is frequent in adult and pediatric brain tumors and occurs in TICs, which are thought to give rise to the tumor. CST6 methylation may therefore represent a novel prognostic marker and therapeutic target specifically altered in TICs.     

Loss of DCC expression in astrocytomas: relation to p53 abnormalities, cell kinetics, and survival

AIMS: Although frequent reduction or loss of DCC (deleted in colorectal carcinomas) has been demonstrated in gliomas, the association with cell kinetics and survival is still unclear. METHODS: A total of 119 astrocytomas, comprising 39 grade IV, 36 grade III, and 44 low grade tumours, were immunohistochemically investigated, along with 26 normal adult brain samples and two fetal brains. The results were compared with p53 abnormalities, Ki-67 labelling index (LI), mitotic index (MI), apoptotic index (AI), and survival. RESULTS: In normal adult and fetal brain tissues, DCC expression was detected in mature and terminally differentiated neuronal cells but not glial elements. In astrocytomas, whereas DCC expression was still clearly shown with low grade malignancy, DCC scores were significantly decreased in high histological grade malignancy, along with an increase in cell kinetics determined by AI, MI, and Ki-67 LI values. In addition, p53 LI values were significantly increased, although a direct link between DCC scores and p53 LI values was not evident. Univariate analysis revealed that high DCC scores and low p53 LI values were closely related to a favourable outcome for astrocytoma, although only the AI was an independent prognostic factor. CONCLUSIONS: The loss of DCC expression may be closely related to changes in cell kinetics and tumour phenotype in astrocytomas, independent of p53 abnormalities.     

Prognostic significance of expressions of cell-cycle regulatory proteins in gastrointestinal stromal tumor and the relevance of the risk grade

Gastrointestinal stromal tumors (GISTs) have a wide spectrum of biologic behavior ranging from benign to malignant. Risk grading based on tumor size and mitotic counts has been proposed in an effort to predict the adverse outcome of GIST in the literature so far. Recent molecular studies have reported the prognostic values of several parameters, including alteration of cell-cycle regulators. The aim of this study was to elucidate the prognostic values of risk grade and alterations of cell-cycle-related proteins, including Ki-67, cyclin A, cyclin B1, cyclin D1, cyclin E, p16, p21, p27, p53, cdc2, and cdk2, in addition to the conventional factors. Eighty cases of primary c-kit-positive GISTs were classified into 2 cases of very-low-risk grade, 20 cases of low-risk grade, 25 cases of intermediate-risk grade, and 33 cases of high-risk grade. The risk grade was correlated with the presence of metastases and/or recurrence. A high level of Ki-67 and cyclin A expression was correlated with risk grade (P = .0027 and .0441, respectively). Overexpression of G2-M regulators, such as cyclin A, cyclin B1, and cdc2, was associated with the Ki-67 labeling index (LI) (P = .0007, .0475, and .0040, respectively). According to univariate analysis, tumor grade (high risk), tumor size (> or =5 cm), mitotic counts (> or =5/50 high-power fields), Ki-67 LI (> or =4.92%), cyclin A LI (> or =1.61%), and cdc2 LI (> or =1.25%) were all found to be significantly associated with a shorter period of disease-free survival (P = .0001, .0270, .0004, .0001, .0001, and .0011, respectively). According to multivariate analysis, both high Ki-67 LI and high-risk grade were found to be significantly associated with a shorter period of disease-free survival (P = .0083 and .0246, respectively). In conclusion, our results strongly support the hypothesis that Ki-67 LI and risk grade are useful for predicting the aggressive biologic behavior of GISTs. Furthermore, alteration of G2-M regulators, such as cyclin A, cyclin B1, and cdc2, is also a useful marker for predicting aggressive behavior and play an important role, at least in part, in the cell proliferation of GIST.     

Prognostic significance of p27 and Ki-67 expression in mucoepidermoid carcinoma of the intraoral minor salivary gland.

p27 and Ki-67, a universal cyclin-dependent kinase inhibitor and a proliferative cell marker, respectively, have been useful in predicting clinical aggressiveness in various human tumors. We studied clinicopathologic significance of these molecules in mucoepidermoid carcinoma of the intraoral minor salivary gland. Expression of p27 and Ki-67 was assessed immunohistochemically in primary mucoepidermoid carcinomas from 31 patients without distant metastasis at surgery. Correlation each of p27 and Ki-67 expression was analyzed with various clinicopathologic parameters including age, sex, primary tumor site, tumor size, nodal metastasis, clinical stage, and histologic grade. The latter was evaluated using a point-scoring scheme of Auclair et al. that consists of five histologic factors (intracystic component, neural invasion, necrosis, mitosis, and anaplasia). p27 expression was correlated inversely with histologic grade (P =.007), but with none of other factors. When the correlation of p27 expression was further examined with each of the histologic factors, it was correlated significantly with intracystic component, but not with neural invasion, necrosis, mitosis, or anaplasia. Ki-67 expression was correlated significantly with histologic grade only in the clinicopathologic factors (P <.0001), and in the histologic factors, with necrosis, mitosis, and anaplasia. Multivariate prognostic analyses were performed to identify independent risk factors for both disease-free and overall survivals. Large tumor size (P =.031, relative risk = 5.5) and low p27 expression (P =.012, relative risk = 5.2) were risk factors for worse disease-free survival. Low p27 expression (P =.015, relative risk = 15.2) was selected as a risk factor for worse overall survival. Other factors including age, sex, tumor site, nodal status, clinical stage, histologic grade, and Ki-67 did not emerge as independent risk factors in either prognostic analysis. These data suggest that p27 may be useful in estimating prognosis of the patients who have mucoepidermoid carcinoma of the intraoral minor salivary gland.     

Expression of cysteine proteinases cathepsins B and K and of cysteine proteinase inhibitor cystatin C in giant cell tumor of tendon sheath.

The expression of cysteine proteinases cathepsins B and K and of the endogenous inhibitor of cysteine proteinases, cystatin C, was investigated in tissue specimens of patients with giant cell tumor of tendon sheath (GCTTS). Expression of both enzymes was examined by immunohistochemistry in tissue specimens of 14 patients with GCTTS. Applying double-labeling techniques, the coexpression of cathepsin B and its major endogenous inhibitor cystatin C was additionally studied. Cells expressing the respective proteins were further characterized with the macrophage markers HAM56 and anti-CD68 (clone PG-M1). Cathepsin B could be detected in numerous HAM56-positive mononuclear cells (MC), but only in very few giant cells (GC). In contrast, cathepsin K was predominantly identified in GC that were also strongly immunoreactive for cystatin C and CD68. Coexpression of cathepsin B and cystatin C occurred only in a few MC. The strong expression of both cathepsin B and K suggests that in GCTTS, bone erosion might be mediated not only by pressure of the proliferative tissue, but also by matrix-degrading cysteine proteinases. Because previous studies showed that osteoclasts express high levels of CD68, cathepsin K, and cystatin C but not of cathepsin B, our study contributes to the view that GC of GCTTS and osteoclasts are closely associated.     

Correlation of enhanced cell turnover with prognosis of gastrointestinal stromal tumors of the stomach: relevance of cellularity and p27kip1

The aim of the present study was to determine whether expression of molecules associated with cell cycle regulation and apoptosis might reflect tumor grade and patients' prognosis of gastrointestinal stromal tumor (GIST). Forty-nine cases of gastric GIST were divided into three grades; low, intermediate, and high risk. Ki-67, cyclin A, cyclin D1, cyclin E, p16(Ink4), p21(Waf1), p27(Kip1), cyclin-dependent kinase (cdk)2, cdk4 and single-strand DNA (ssDNA) were immunohistochemically stained and assessed. Ki-67, ssDNA, cyclin A and cdk2 had higher labeling indices (LI) in high-risk than in low-risk cases. Cyclin E expression was greater in the intermediate- than in the low-risk grade. On Kaplan-Meier analysis, tumor size, necrosis, cellularity, Ki-67, ssDNA, and cyclin A LI were significantly correlated with disease-free survival. Necrosis, cellularity, and Ki-67 LI were significant as prognostic factors on univariate, and Ki-67 LI on multivariate Cox hazard tests. Within the high-risk grade, high cellularity and low p27(Kip1) subgroups had the worst prognosis. The histological grade is related to cell turnover, assessed in terms of Ki-67, ssDNA, cyclin A, cyclin E, and cdk2 levels. Ki-67, ssDNA, and cyclin A are useful for prediction of prognosis, with cellularity and p27(Kip1) expression as further prognostic factors in high-risk cases.     

星形细胞瘤预后相关的临床与病理多因素分析

目的拟找出与各级星形细胞瘤的预后相关的因素.方法收集解放军总医院病理科1987～1996年间归档的颅内各级星形细胞瘤,选择其中经手术全切、术后正规放疗且资料基本齐全的120例(其中94例有随访资料).同时选取尸检正常脑组织、脱髓鞘病变组织共20份作为对照.应用免疫组织化学方法检测石蜡标本中Ki-67、血管内皮生长因子(VEGF)、TRT蛋白的表达,用Ⅳ型胶原标记微血管,并用原位杂交方法检测TRTmRNA和端粒酶RNA的表达,对所得的各项指标进行统计分析.结果(1)Ki-67在肿瘤和脱髓鞘病变呈多少不等的阳性,不同级别及与非肿瘤组织之间差异有显著性.多元回归分析显示该指标是预后的独立危险因素之一,以8.5%为分界点两条生存曲线间时序分析差异有显著性(P＜0.01).(2)微血管密度Ⅰ、Ⅱ级与正常脑组织胶质细胞之间的微血管密度差异无显著性,而Ⅲ、Ⅳ级微血管数均显著增多(P＜0.01),坏死组织中微血管平均数较Ⅲ、Ⅳ级更为增多,VEGF的表达与微血管密度呈显著性相关(P＜0.01).(3)端粒酶反转录酶蛋白在正常胶质细胞中呈阴性,在增生病例和Ⅰ、Ⅱ、Ⅲ、Ⅳ级肿瘤病变中呈现阳性率和阳性强度递增的现象,它与分级和预后相关(P＜0.01);端粒酶反转录酶mRNA和端粒酶BNA的表达明显低于TRT蛋白水平的表达,但与TRT蛋白显著相关(P＜0.01).结论用Cox-回归模型进行多因素分析,筛选出了对人星形细胞瘤预后有密切关系的6个指标病理分级是最重要的预后因子,其次为Ki-67阳性率、年龄、术前等待时间(或称出现症状到第一次手术时间),而肿瘤组织微囊变和VEGF的表达则为保护因素.     

Modification of cystatin C activity by bacterial proteinases and neutrophil elastase in periodontitis.

AIM: To study the interaction between the human cysteine proteinase inhibitor, cystatin C, and proteinases of periodontitis associated bacteria. METHODS: Gingival crevicular fluid samples were collected from discrete periodontitis sites and their cystatin C content was estimated by enzyme linked immunosorbent assay (ELISA). The interaction between cystatin C and proteolytic enzymes from cultured strains of the gingival bacteria Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans was studied by measuring inhibition of enzyme activity against peptidyl substrates, by detection of break down patterns of solid phase coupled and soluble cystatin C, and by N-terminal sequence analysis of cystatin C products resulting from the interactions. RESULTS: Gingival crevicular fluid contained cystatin C at a concentration of approximately 15 nM. Cystatin C did not inhibit the principal thiol stimulated proteinase activity of P gingivalis. Instead, strains of P gingivalis and P intermedia, but not A actinomycetemcomitans, released cystatin C modifying proteinases. Extracts of five P gingivalis and five P intermedia strains all hydrolysed bonds in the N-terminal region of cystatin C at physiological pH values. The modified cystatin C resulting from incubation with one P gingivalis strain was isolated and found to lack the eight most N-terminal residues. The affinity of the modified inhibitor for cathepsin B was 20-fold lower (Ki 5 nM) than that of full length cystatin C. A 50 kDa thiol stimulated proteinase, gingipain R, was isolated from P gingivalis and shown to be responsible for the Arg8-bond hydrolysis in cystatin C. The cathepsin B inhibitory activity of cystatin C incubated with gingival crevicular fluid was rapidly abolished after Val10-bond cleavage by elastase from exudate neutrophils, but cleavage at the gingipain specific Arg8-bond was also demonstrated. CONCLUSIONS: The physiological control of cathepsin B activity is impeded in periodontitis, owing to the release of proteinases from infecting P gingivalis and neutrophils, with a contribution to the tissue destruction seen in periodontitis as a probable consequence.     

Correlation between grade and prognosis in metastatic gastroenteropancreatic neuroendocrine tumors

Three-tiered grading systems (low, intermediate, and high grade) have been proposed for neuroendocrine tumors. These classifications have not been rigorously evaluated in neuroendocrine malignancies of the digestive tract. We performed a retrospective chart analysis of 83 patients with metastatic gastroenteropancreatic neuroendocrine tumors, correlating tumor grade with overall survival. We also analyzed available biopsy specimens (on 40 patients), examining hematoxylin and eosin stains for mitotic rate and immunostaining for measurement of the Ki-67 index. Tumor grades were assigned based on the mitotic rate and the Ki-67 index, and the prognostic validity of each grading method was assessed. A highly significant correlation existed between the reported tumor grade and overall survival. Five-year survival rates for patients with low-, intermediate-, and high-grade tumors were 87%, 38%, and 0%, respectively. On biopsy specimen analysis, both mitotic rates and Ki-67 indexes correlated strongly with overall survival. We conclude that a 3-tiered grading classification for gastroenteropancreatic neuroendocrine tumors correlates with survival in the metastatic setting. Both mitotic rates and Ki-67 indexes are inversely associated with survival and can be analyzed independently for assignment of grade.     

Gene deletion of cystatin C aggravates brain damage following focal ischemia but mitigates the neuronal injury after global ischemia in the mouse

Cystatin C is distributed in all human tissues and fluids with a particular abundance in the cerebrospinal fluid. Cystatin C is a strong endogenous inhibitor of lysosomal cysteine proteases, such as cathepsin B, L, H and S, that are involved in various biological processes such as degradation of cellular proteins and regulation of enzymes, as well as in pathological processes. Pharmacological inhibition of cathepsins has been shown to reduce neuronal damage after brain ischemia, suggesting that cystatin C is an endogenous neuroprotectant. Cystatin C has also amyloidogenic properties and is co-localized with beta-amyloid in degenerated neurons in Alzheimer's disease, suggesting a role in neuronal degeneration. To test the hypothesis that endogenous cystatin C is neuroprotective during brain ischemia, global and focal brain ischemia was induced in mice with the cystatin C gene knocked out. Following focal ischemia, larger brain infarcts were found in cystatin C knockout mice, probably due to a reduced inhibition of the cathepsins during ischemia. In contrast, brain damage after global ischemia was diminished in cystatin C knockout mice, suggesting that cystatin C has an aggravating effect on selective neuronal damage after global ischemia.     

Overexpression of cyclin A and cyclin B1 proteins in astrocytomas

BACKGROUND: Cyclins are proteins that are expressed during the progression of a normal cell through the cell cycle. In a number of cancers, overexpression of cyclin A and cyclin B1 proteins has been reported, and in some instances the levels of expression correlated well with the grades of malignancy. The expression of cyclin A and cyclin B1 proteins in astrocytoma may be linked to the histologic grade or proliferative activities. OBJECTIVE: To study the expression of cyclin A and cyclin B1 proteins in astrocytomas and correlate the labeling indices (LIs) of cyclin A and cyclin B1 with histologic grade and Ki-67 LI. DESIGN: The surgical biopsy specimens from 65 adults with astrocytomas were reviewed and divided into grades based on the World Health Organization system. The paraffin sections were immunostained using primary antibodies against Ki-67, cyclin A, and cyclin B1. The LIs of these astrocytomas for the 3 different antibodies were determined by computerized image analysis. RESULTS: The cyclin A LI showed good correlation with astrocytoma grade and Ki-67 LI. Both the nuclear and cytoplasmic cyclin B LIs correlated well with the tumor grade but showed poor correlation with Ki-67 LI. CONCLUSIONS: This study suggests that although both cyclin A and B protein expression are related to the grade of malignancy in astrocytomas, cyclin A levels more generally reflect the proliferative state of these tumors. We also provide indirect evidence that cyclin B1 is associated with the aberrant progression through the G2-M phase checkpoint in astrocytomas.     

p53,Ki-67及E-钙黏蛋白在三阴性乳腺癌中的表达及预后

目的:探讨p53,Ki-67及E-钙黏蛋白(E-cadherin)在三阴性乳腺癌(triple negative breast cancer,TNBC)组织中的表达及预后的关系.方法:采用免疫组织化学法检测52例TNBC和52例非三阴性乳腺癌(non-triple-negative breast cancer,NTNBC)组织中p53,Ki-67及E-cadherin表达情况,观察3个指标与TNBC患者临床病理学特征及预后的关系.结果:TNBC组织中p53,Ki-67及E-cadherin的阳性表达率分别为67.3％,80.8％,26.9％;而在NTNBC组织中为44.2％,61.5％,48.1％(均P＜0.05).在TNBC组织中,p53表达阳性与肿瘤大小、TNM分期及组织学分级有关(均P＜0.05);Ki-67表达阳性与TNM分期、淋巴结转移有关(均P＜0.05);E-cadherin表达阳性与肿瘤大小、TNM分期、淋巴结转移有关(均P＜0.05).在TNBC患者中,p53,Ki-67及E-cadherin表达阳性者与阴性者总体生存率(overall survival,OS)的差异均有统计学意义(P＜0.05).Cox回归分析多因素显示:淋巴结转移、p53、Ki-67及E-cadherin表达是影响TNBC患者总体生存率的独立预后因素(均P＜0.05).结论:TNBC组织中,p53、Ki-67高表达,其表达阳性者预后差,E-cadherin低表达,其表达阳性者预后良好.联合检测p53、Ki-67及E-cadherin表达可为TNBC患者的治疗提供新靶点.     

Expression of topoisomerase II and Ki-67 in cervical carcinoma--clinicopathological study using immunohistochemistry

AIM: To study the correlation between the expression of topoisomerase II and Ki-67 antigen and disease outcome in cervical squamous cell carcinomas. EXPERIMENTAL DESIGN: Forty-nine cervical carcinomas, 10 cases of high-grade cervical intraepithelial neoplasia (CIN II-III) and 5 control cervices were stained by monoclonal antibodies for topoisomerase II and Ki-67 (MIB-1 clone). Nuclear counts were correlated with patient age, tumor stage, histological grade and survival. RESULTS: Thirteen patients died of disease, 35 remained free of disease, and one patient was lost to follow up. Ki-67 counts were higher in CIN lesions, when compared to both invasive carcinomas and control cervices. Topoisomerase II counts were comparable for CIN and invasive tumors. No immunoreactivity for topoisomerase was detected in control cases. Neither stage nor grade was associated with nuclear counts using either marker. In multivariate survival analysis, stage (p=0.001), grade (p=0.03) and older patient age (p=0.02) predicted poor survival. Ki-67 counts predicted survival with borderline significance (p=0.07), while topoisomerase II counts were not related to survival. CONCLUSION: Ki-67 and topoisomerase II counts do not appear to have a significant role in the prediction of survival in cervical squamous cell carcinoma.     

胶质瘤miR-218与细胞周期蛋白依赖性激酶6表达的相互关系及其对肿瘤细胞增殖和凋亡的影响

目的 探讨胶质瘤细胞中miR-218及细胞周期蛋白依赖性激酶6(CDK6)表达变化的相互关系及其对肿瘤细胞增殖及凋亡的影响.方法 采用组织微阵列、锁定寡核苷酸探针原位杂交及免疫组织化学(ABC法)方法,检测60例不同级别胶质瘤组织标本及10例对照脑组织中miR-218、CDK6及Ki-67抗原的表达状况,并分析三者之间的相互关系;胶质母细胞瘤细胞系(U87MG)分别被转染阴性对照序列(对照组)及miR-218 mimics(mimics组),采用即时定量聚合酶链反应(qRT-PCR)及免疫细胞化学方法 分别检测两组细胞中的miR-218水平及CDK6和Ki-67表达变化,用单细胞凝胶电泳检测凋亡细胞.结果 对照组、Ⅰ～Ⅱ级、Ⅲ级和Ⅳ级胶质瘤组miR-218阳性标记指数(LI,%)分别为22.45±0.59、4.00±1.07、1.87±1.06、0.94±0.78,四组间差异均有统计学意义(P<0.05);各组CDK6 LI分别为7.25±1.20、16.71±0.80、24.43±0.62、32.05±0.43,对照组与各胶质瘤组间及Ⅳ级组与Ⅰ～Ⅱ级组间差异有统计学意义(P<0.01);各组Ki-67阳性细胞密度分别为0.00±0.00、9.30±3.48、31.15±9.44、60.15±13.60[(±s)/0.05 mm2],各组间差异均有统计学意义(P<0.01);miR-218 LI与CDK6 LI及Ki-67阳性细胞密度间均呈显著性负相关(r=-0.480,-0.534,P<0.01),后两者间呈显著性正相关(r=0.530,P<0.01).mimics组的miR-218水平明显高于对照组,其CDK6及Ki-67 LI(14.74±1.19、30.88±3.31)均明显低于对照组(79.06±2.07、64.94±3.96,P<0.01),而凋亡指数(68.44±7.05)明显高于对照组(13.04±0.97),以上各指标两组间差异均有统计学意义(P<0.01).结论 miR-218表达水平是评价胶质瘤良恶性程度的重要参考指标;其表达异常减少可导致胶质瘤细胞CDK6表达及增殖活性增强;补充外源性miR-218可有效下调恶性胶质瘤细胞CDK6表达、抑制其增殖和促进其凋亡,故在恶性胶质瘤基因治疗中具有重要的潜在应用价值.

Abstract：

Objectives To investigate the relationship between the expression of miR-218 and CDK6 in glioma cells, and their biological impacts on the tumor cell proliferation and apoptosis. MethodsExpression levels of miR-218 as well as CDK6 and Ki-67 proteins were analyzed in 60 cases of gliomas with various grades and 10 control brain tissue samples by tissue microarray, locked oligonucleotide probe in situ hybridization and immunohistochemistry. Glioblastoma multiform cell line (U87MG) was transfected with miR-218 mimics (mimics group) and a control sequence (control group), followed by qRT-PCR detection of miR-218 and immunocytochemical stain of CDK6 and Ki-67, respectively. Single cell gel electrophoresis was used to detect the presence of apoptotic cell. Results The miR-218 labeling indexes (LI) were statistically different (P<0.05) among all groups including control (22.45±0.59) and various glioma groups (grades Ⅰ-Ⅱ 4.00±1.07, grade Ⅲ 1.87±1.06 and grade Ⅳ 0.94±0.78, respectively). The CDK6 LI of the four groups was 7.25±1.20, 16.71±0.80, 24.43±0.62 and 32.05±0.43, respectively. Significant differences existed between the control group and the glioma groups, and between grade Ⅳ and grades Ⅰ-Ⅱ glioma groups (P<0.01). Ki-67 positive cell densities of the above four groups (0.00±0.00, 9.30±3.48, 31.15±9.44 and 60.15±13.60) were significantly different from one and another (P<0.01). The expression of miR-218 negatively correlated with CDK-6 LI (r=-0.480, P<0.01) and Ki-67 positive cell density (r=-0.534, P<0.01), while the latter two positively correlated with each other (r=0.530, P<0.01). U87MG transfection experiment showed that the miR-218 level of the mimics group was significantly higher than that of the control group (P<0.01). CDK6 and Ki-67 LI of the mimics group (14.74±1.19 and 30.88±3.31) were significantly lower than those of the control group (79.06±2.07 and 64.94±3.96, P<0.01), whilst its apoptotic index (AI) (68.44±7.05) was significantly higher than that of the control group (13.04±0.97, P<0.01). Conclusions The expression level of miR-218 is an important reference indicator for the assessment of the grade of gliomas. An aberrant decrease of its expression may lead to an increase of the CDK6 expression and proliferative activity of giloma cells. Introducing exogenous miR-218 may effectively down-regulate the CDK6 expression, inhibit cell proliferation and induce apoptosis of malignant giloma cells. These findings imply that miR-218 may serve as a therapeutic agent against malignant glioma.