Systematic Review Biomarkers For reprint orders,please contact:reprints@futuremedicine.com in Medicine Relationship between microvessel density and cancer stem cells in tumor angiogenesis:a meta-analysis Aim:Several studies have shown that cancer stem cells (CSCs)promote tumor Jiaojiao Lan1,Jun Lit.2 angiogenesis and are involved in tumor growth.A meta-analysis was conducted to Xinxin Ju',Yang Zhou', evaluate the association between cancer stem cell markers expression and microvessel Yan Qi,Yan Ren',Hong Zou', density (MVD).Methods:Relevant literature was identified from diverse databases. Lianghai Wang',Man Li The Stata 12.0 and Review Manager 5.3 software were used to performed meta- Lijuan Pang*.1 Department of Pathology Key analysis.Results:Sixteen studies investigating the correlation between CSCs and Laboratory for Xinjiang Endemic Ethnic tumor angiogenesis were included in a total of 1409 cases.The result showed that Diseases (Ministry of Education),Shihezi positive CSC markers expression were associated with increased MVD count in human University School of Medicine,Shihezi, tumors and CSC-transplanted mouse tumor models(p<0.0001).Conclusion:CSCs may Xinjiang,China be associated with angiogenesis during the growth and development of tumors. 2Department of Ultrasonic Medicine, The First Affiliated Hospital,Shihezi University School of Medicine,Shihezi, First draft submitted:29 January 2016;Accepted for publication:6 June 2016; Xinjiang,China Published online:14 July 2016 *Author for correspondence: Tel.:+8613677565458 Keywords:cancer stem cells.meta-analysis.microvessel density.tumor angiogenesis Fax+869932057136 0cean123456@163.c0m Authors contributed equally Tumors may arise from a small subset of nant role in neovascularization during tumor cancer cells that are capable of self-renewal,growth. unlimited proliferation and tumorigenic- CSCs represent a small subpopulation of ity;such cells are termed cancer stem cells cells withinatumor that express surface mark- (CSCs)[j.CSCs have been identified and ers such as CD133 [o],nestin ABCG2 [2 isolated from tumors and tumor-derived cell and ALDHI [3].A common marker of angio- lines,including melanoma [2l and brain [3],genesis,micro-vessel density(MVD)[41,has breast [4]and lung cancers [51.It is widely been utilized for the quantification of intratu- accepted that angiogenesis is involved in moral angiogenesis in tumor tissue in recent the growth and hematogenous spread of years.Several vascular endothelial cell mark- tumors []Cancer invasion and metastasis ers,such as CD31 [is]and CD34 [6],may be involves multiple complex steps and involves used for the detection of MVD.We speculate a variety of molecules.Angiogenesis,which that CSCs may be involved in angiogenesis enables the supply of blood and nutrients for during tumor growth.Therefore,the present tumor growth,is an important step in can- meta-analysis was performed to investigate cer invasion and metastasis [6.71.According the relationship between CSCs and angio- to the CSC hypothesis,CSCs play a critical genesis by assessing MVD,which may be role in maintaining the capacity for malig- utilized as a clinical parameter for predicting nant proliferation,invasion,metastasis and prognosis during tumor therapy. recurrence of the tumor [8).CSCs may induce cancer metastasis through multiple pathways Materials methods and support tumor progression by promot- Search strategy study selection Future ing angiogenesis [91.Therefore,accumulating We searched MEDLINE using PubMed, evidence indicates that CSCs play a predomi- Medicine paort of CNKI (China National Knowledge Infra- 10.2217/bmm-2016-0026 2016 Future Medicine Ltd Biomark.Med.(Epub ahead of print) 5SN1752-0363
Biomark. Med. (Epub ahead of print) ISSN 1752-0363 part of Systematic Review 10.2217/bmm-2016-0026 © 2016 Future Medicine Ltd Biomark. Med. Systematic Review 2016/07/22 10 8 2016 Aim: Several studies have shown that cancer stem cells (CSCs) promote tumor angiogenesis and are involved in tumor growth. A meta-analysis was conducted to evaluate the association between cancer stem cell markers expression and microvessel density (MVD). Methods: Relevant literature was identified from diverse databases. The Stata 12.0 and Review Manager 5.3 software were used to performed metaanalysis. Results: Sixteen studies investigating the correlation between CSCs and tumor angiogenesis were included in a total of 1409 cases. The result showed that positive CSC markers expression were associated with increased MVD count in human tumors and CSC-transplanted mouse tumor models (p < 0.0001). Conclusion: CSCs may be associated with angiogenesis during the growth and development of tumors. First draft submitted: 29 January 2016; Accepted for publication: 6 June 2016; Published online: 14 July 2016 Keywords: cancer stem cells • meta-analysis • microvessel density • tumor angiogenesis Tumors may arise from a small subset of cancer cells that are capable of self-renewal, unlimited proliferation and tumorigenicity; such cells are termed cancer stem cells (CSCs) [1]. CSCs have been identified and isolated from tumors and tumor-derived cell lines, including melanoma [2] and brain [3], breast [4] and lung cancers [5]. It is widely accepted that angiogenesis is involved in the growth and hematogenous spread of tumors [1]. Cancer invasion and metastasis involves multiple complex steps and involves a variety of molecules. Angiogenesis, which enables the supply of blood and nutrients for tumor growth, is an important step in cancer invasion and metastasis [6,7]. According to the CSC hypothesis, CSCs play a critical role in maintaining the capacity for malignant proliferation, invasion, metastasis and recurrence of the tumor [8]. CSCs may induce cancer metastasis through multiple pathways and support tumor progression by promoting angiogenesis [9]. Therefore, accumulating evidence indicates that CSCs play a predominant role in neovascularization during tumor growth. CSCs represent a small subpopulation of cells within a tumor that express surface markers such as CD133 [10], nestin [11], ABCG2 [12] and ALDH1 [13]. A common marker of angiogenesis, micro-vessel density (MVD) [14], has been utilized for the quantification of intratumoral angiogenesis in tumor tissue in recent years. Several vascular endothelial cell markers, such as CD31 [15] and CD34 [16], may be used for the detection of MVD. We speculate that CSCs may be involved in angiogenesis during tumor growth. Therefore, the present meta-analysis was performed to investigate the relationship between CSCs and angiogenesis by assessing MVD, which may be utilized as a clinical parameter for predicting prognosis during tumor therapy. Materials & methods Search strategy & study selection We searched MEDLINE using PubMed, CNKI (China National Knowledge InfraRelationship between microvessel density and cancer stem cells in tumor angiogenesis: a meta-analysis Jiaojiao Lan‡,1 , Jun Li‡,2, Xinxin Ju1 , Yang Zhou1 , Yan Qi1 , Yan Ren1 , Hong Zou1 , Lianghai Wang1 , Man Li1 & Lijuan Pang*,1 1 Department of Pathology & Key Laboratory for Xinjiang Endemic & Ethnic Diseases (Ministry of Education), Shihezi University School of Medicine, Shihezi, Xinjiang, China 2 Department of Ultrasonic Medicine, The First Affiliated Hospital, Shihezi University School of Medicine, Shihezi, Xinjiang, China *Author for correspondence: Tel.: +86 136 7756 5458 Fax: +86 993 205 7136 ocean123456@163.com ‡ Authors contributed equally For reprint orders, please contact: reprints@futuremedicine.com
Systematic Review Lan,Li,Ju et al. structure)and the Wan-fang database for relevant animal models of transplanted tumors:author,year, studies as of 4 May 2016,without language restric- model of tumor,type of transplanted animal,the tions.The search strategy used text terms such as 'can-number of transplanted animals,number of injected cer stem cells (CSCs)','stem cell','cancer,'tumor,tumor cells or stem cells,time and mean and standard 'angiogenesis,'vascularization'and 'microvessel den-deviation value of MVD(Table 2).If data from any of sity (MVD)'in PubMed.Eligible articles and relevant the above categories were not reported in the literature, review articles were also manually reviewed.Studies items were regarded as'not applicable.' eligible for inclusion in this meta-analysis satisfied the following criteria:case-control studies assessing the Statistical methods analysis relationship between the expression of CSC markers Statistical analyses of included studies were performed and pathological features of tumors;articles describing by comparing MVD value between the groups that the association between the expression of CSC mark-was positive and negative expression for CSC mark- ers and MVD count;literature reporting data with the ers in human tumor tissues.In addition,we measured mean or standard deviation of MVD as the statisti-the MVD count on animal models of transplanted cal indicator;and studies focusing on the evaluation of tumors between the experimental group and control CSC marker expression in tumor tissue using immu- group.The MVD counts were regarded as continuous nohistochemistry.In addition,with regard to duplicate variables,using mean and standard deviation. studies,only the most recent or most informative was The meta-analysis was performed using STATA included in the present meta-analysis.Two review- 12.0 and Review manager 5.3software.Standard ers (JIL and LIP)independently determined study mean difference (SMD)with a corresponding 95% eligibility.Disagreements were resolved by consensus. confidence interval (CI)was calculated.Meanwhile, odds ratios(ORs)with 95%CI were used to evaluate Data extraction quality assessment the correlation between CSC marker expression and We extracted information regarding the author,year,clinicopathological characteristics.For each analysis, sample number,type of tumor,CSC vascular endo-an OR>1 implied higher levels of expression of CSC thelial markers and the mean and standard deviation markers in the indicated group.The Z test was used value of MVD in human tumor tissues(Table 1).The for evaluating the statistical significance of SMD.The following relevant data were extracted with regard to Cochran's Q-statistic [7]and I2 [s]test were used for Table 1.Main characteristics and results of the eligible studies in human tumor tissues. Study (year) Cancers CSCs Vascular MVD of the high expression/ MVD of the low expression/ Ref. markers endothelial positive of CSC markers negative of CSC markers antibodies N M SD N M SD Feng Li(2011) Lung cancer CD133/ CD34 33 85.4 31.7 112 55.3 24.5 [2o ABCG2+ Jun Dong(2011)Brain tumor ABCG2 CD34 24 31 19.20 68 13 12.09 [21 Huaming Wang Brain tumor CD133 CD34 68 23.57 7.16 4.67 1.53 [22 (2011) Lingjun Kong Brain tumor CD133/ CD34 39 52.5 20.0 11 26.6 13.7 [23) (2012) Nestin Qing Li(2012) Lung cancer CD133/ CD34 14 22.64 5.123 36 19.75 5.872 [24 ALDH1A1 Shiwu Wu(2012)Lung cancer CD133 CD34 149 29.4 9.8 156 15.0 7.2 [25 Liang Pan(2013)Brain tumor CD133 CD34 37 38.76 13.87 9 20.22 5.26 [26 Yungin Huang Breast CD133 CD34 63 22.0 8.3 42 18.0 6.4 [271 (2013) cancer Yiming Song Breast CD133/ CD34 31 28.78 10.55 110 26.92 9.02 [28] (2015) cancer ALDH1 Zhengquan Han Breast CD133 CD34 158 22.1 6.3 167 19.1 6.3 [29 (2015) cancer CSC:Cancer stem cell;M:Mean;MVD:Microvessel density;N:Number;SD:Standard deviation. 10.2217/bmm-2016-0026 Biomark.Med.(Epub ahead of print) future science groupg
10.2217/bmm-2016-0026 Biomark. Med. (Epub ahead of print) future science group Systematic Review Lan, Li, Ju et al. structure) and the Wan-fang database for relevant studies as of 4 May 2016, without language restrictions. The search strategy used text terms such as ‘cancer stem cells (CSCs)’, ‘stem cell’, ‘cancer’, ‘tumor’, ‘angiogenesis’, ‘vascularization’ and ‘microvessel density (MVD)’ in PubMed. Eligible articles and relevant review articles were also manually reviewed. Studies eligible for inclusion in this meta-analysis satisfied the following criteria: case–control studies assessing the relationship between the expression of CSC markers and pathological features of tumors; articles describing the association between the expression of CSC markers and MVD count; literature reporting data with the mean or standard deviation of MVD as the statistical indicator; and studies focusing on the evaluation of CSC marker expression in tumor tissue using immunohistochemistry. In addition, with regard to duplicate studies, only the most recent or most informative was included in the present meta-analysis. Two reviewers (JJL and LJP) independently determined study eligibility. Disagreements were resolved by consensus. Data extraction & quality assessment We extracted information regarding the author, year, sample number, type of tumor, CSC vascular endothelial markers and the mean and standard deviation value of MVD in human tumor tissues (Table 1). The following relevant data were extracted with regard to animal models of transplanted tumors: author, year, model of tumor, type of transplanted animal, the number of transplanted animals, number of injected tumor cells or stem cells, time and mean and standard deviation value of MVD (Table 2). If data from any of the above categories were not reported in the literature, items were regarded as ‘not applicable.’ Statistical methods & analysis Statistical analyses of included studies were performed by comparing MVD value between the groups that was positive and negative expression for CSC markers in human tumor tissues. In addition, we measured the MVD count on animal models of transplanted tumors between the experimental group and control group. The MVD counts were regarded as continuous variables, using mean and standard deviation. The meta-analysis was performed using STATA 12.0 and Review manager 5.3software. Standard mean difference (SMD) with a corresponding 95% confidence interval (CI) was calculated. Meanwhile, odds ratios (ORs) with 95% CI were used to evaluate the correlation between CSC marker expression and clinicopathological characteristics. For each analysis, an OR >1 implied higher levels of expression of CSC markers in the indicated group. The Z test was used for evaluating the statistical significance of SMD. The Cochran’s Q-statistic [17] and I2 [18] test were used for Table 1. Main characteristics and results of the eligible studies in human tumor tissues. Study (year) Cancers CSCs markers Vascular endothelial antibodies MVD of the high expression/ positive of CSC markers MVD of the low expression/ negative of CSC markers Ref. N M SD N M SD Feng Li (2011) Lung cancer CD133+/ ABCG2+ CD34 33 85.4 31.7 112 55.3 24.5 [20] Jun Dong (2011) Brain tumor ABCG2 CD34 24 31 19.20 68 13 12.09 [21] Huaming Wang (2011) Brain tumor CD133 CD34 68 23.57 7.16 3 4.67 1.53 [22] Lingjun Kong (2012) Brain tumor CD133/ Nestin CD34 39 52.5 20.0 11 26.6 13.7 [23] Qing Li (2012) Lung cancer CD133/ ALDH1A1 CD34 14 22.64 5.123 36 19.75 5.872 [24] Shiwu Wu (2012) Lung cancer CD133 CD34 149 29.4 9.8 156 15.0 7.2 [25] Liang Pan (2013) Brain tumor CD133 CD34 37 38.76 13.87 9 20.22 5.26 [26] Yunqin Huang (2013) Breast cancer CD133 CD34 63 22.0 8.3 42 18.0 6.4 [27] Yiming Song (2015) Breast cancer CD133/ ALDH1 CD34 31 28.78 10.55 110 26.92 9.02 [28] Zhengquan Han (2015) Breast cancer CD133 CD34 158 22.1 6.3 167 19.1 6.3 [29] CSC: Cancer stem cell; M: Mean; MVD: Microvessel density; N: Number; SD: Standard deviation
Relationship between microvessel density cancer stem cells in tumor angiogenesis Systematic Review Table 2.Main characteristics and results of the eligible studies in mice transplanted tumor model. Study(year) Tumors Animals Cells(n)Time MVD of CSCs groups MVD of tumor cell groups Ref. N M SD v SD Dawei Kong(2008)Brain tumor BALB/cnu/nu ND 28d 5 58.413.3 5.9 1.5 [30 mice Weiqi Nian(2009) Lung cancer C57BL/6mice1×105 21d6 56.874.83 6 43.52 4.91 3 Feng Jin(2011) Brain tumor Nude mice 5000 21d5 34.865.29 22.94 6.72 132 XuHe(2010) Breastcancer BALB/c mice1×10728d8 13.671.538 5.33 1.42 [33 Hao Song(2012) Hepatoma Wistar mouse 1x 105 21 w 10 8.464.6910 1.57 0.86 [34 Lin Lin (2015) Cervical cancer SPF mice 1×10518d5 10.50.85 5 5 0.65 [351 d:Day;M:Mean;MVD:Microvessel density;N:Number;ND:No data:SD:Standard deviation;w:Week. estimating potential heterogeneity between studies.If effects model was applied;otherwise,the fixed effects the Q-statistic showed a p-value<0.05 or I2>50%model was used.We additionally performed subgroup indicating significant heterogeneity,the random analyses to explore potential sources of heterogeneity. PubMed,CNKI and Wan-fang database search as of 1 May 2016 Articles identified through electronic database search(n=202) Studies were excluded due to: Reviews,commentaries,meta-analysis:53 Not related to research topics:98 Potential articles screened:51 Studies were excluded due to: No acquired data:28 No suitable control:7 16 articles included in meta-analysis 10 studies available for meta-analysis 6 studies for meta-analysis in in human tumor tissues mice-transplanted tumor model Figure 1.Flow chart showing the study selection procedure;16 articles were included in this meta-analysis. ifuture science group www.futuremedicine.com 10.2217/bmm-2016-0026
future science group www.futuremedicine.com 10.2217/bmm-2016-0026 Relationship between microvessel density & cancer stem cells in tumor angiogenesis Systematic Review estimating potential heterogeneity between studies. If the Q-statistic showed a p-value < 0.05 or I2 > 50% indicating significant heterogeneity, the random effects model was applied; otherwise, the fixed effects model was used. We additionally performed subgroup analyses to explore potential sources of heterogeneity. Table 2. Main characteristics and results of the eligible studies in mice transplanted tumor model. Study (year) Tumors Animals Cells (n) Time MVD of CSCs groups MVD of tumor cell groups Ref. N M SD N M SD Dawei Kong (2008) Brain tumor BALB/cnu/nu mice ND 28 d 5 58.4 13.3 5 5.9 1.5 [30] Weiqi Nian (2009) Lung cancer C57BL/6 mice 1 × 106 21 d 6 56.87 4.83 6 43.52 4.91 [31] Feng Jin (2011) Brain tumor Nude mice 5000 21 d 5 34.86 5.29 5 22.94 6.72 [32] Xu He (2010) Breastcancer BALB/c mice 1 × 107 28 d 8 13.67 1.53 8 5.33 1.42 [33] Hao Song (2012) Hepatoma Wistar mouse 1 × 106 21 w 10 8.46 4.69 10 1.57 0.86 [34] Lin Lin (2015) Cervical cancer SPF mice 1 × 106 18 d 5 10.5 0.85 5 5 0.65 [35] d: Day; M: Mean; MVD: Microvessel density; N: Number; ND: No data; SD: Standard deviation; w: Week. Figure 1. Flow chart showing the study selection procedure; 16 articles were included in this meta-analysis. PubMed, CNKI and Wan-fang database search as of 1 May 2016 Articles identied through electronic database search (n = 202) Studies were excluded due to: • Reviews, commentaries, meta-analysis: 53 • Not related to research topics: 98 Studies were excluded due to: • No acquired data: 28 • No suitable control: 7 Potential articles screened: 51 16 articles included in meta-analysis 10 studies available for meta-analysis in human tumor tissues 6 studies for meta-analysis in mice-transplanted tumor model
Systematic Review Lan,Li,Ju et al. Study ID SMD(95%CI) Weight(%) Zhengquan Han(2015) 0.48(0.26,0.70) 11.93 Yiming Song (2015) 0.20(-0.20,0.60) 11.06 Yungin Huang(2013) 0.53(0.13,0.92) 11.07 Liang Pan (2013) 1.45(0.67,2.24) 8.47 Shiwu Wu (2012) 1.68(1.42,1.94) 11.76 Qing Li (2012) 0.51(-0.12,1.13) 9.59 Lingjun Kong (2012) 1.37(0.65,2.10) 8.92 Huaming Wang (2011) 2.68(1.44,3.92) 5.79 Jun Dong (2011) 1.26(0.76,1.76) 10.43 Feng Li (2011) 1.15(0.73,1.56) 10.99 Overall (I-squared =88.7%,p=0.000) 1.04(0.63,1.45) 100.00 Note:Weights are from random effects analysis -3.92 0 3.92 Figure 2.Meta-analysis of ten studies evaluating the association between CSC marker expression and MVD in human tumors. CSC:Cancer stem cell;MVD:Microvessel density;SMD:Standardized mean difference. Publication bias was evaluated using the funnel plot Characteristics of the included studies with Begg's bias test 91. The main characteristics of ten eligible studies [2o-291 describing the association between CSCs and MVD in Results human tumor tissues are summarized in Table 1.Addi- A total of 202 studies for CSCs and MVD were iden- tionally,Table 2 shows the characteristics ofsix included tified from a primary literature search of electronic studies [30-35]reporting the relationship between CSCs databases PubMed,CNKI and the Wan-fang database and MVD in tumor transplantation animal models. (Figure 1).After manually screening the titles,abstracts Finally,a total of 1331 cases from ten studies of MVD and key data,151 reviews,commentaries,meta-analy- in human tumor tissues and a total of 78 cases from ses or studies that were not relevant to the present anal- six studies of MVD in tumor transplantation animal ysis were excluded.Of 51 studies selected for detailed models were included.These tem studies in which evaluation:28 studies were excluded;these consisted CSC marker expression was analyzed by immunohis- of 16 studies that did not report MVD values,six stud- tochemistry were included and the Weidner method ies lacking statistical analyses,two studies that lacked was used to calculate MVD. data describing the relationship between MVD and CSC marker expression,four studies were detected by Correlation between the expression of CSCs immunofluorescence staining;seven additional studies markers MVD in human tumor tissues were excluded as they lacked a suitable control group.The characteristics of the ten selected studies that were The final meta-analysis included ten studies for MVD reporting the relationship between CSC markers and and CSC markers in human tumor tissues and six MVD in tumor tissue(Figure 2).The expression of studies for MVD and CSCs in tumor transplantation CSC markers was associated with MVD count;high animal models. levels of expression of CSC markers indicated increased 10.2217/bmm-2016-0026 Biomark.Med.(Epub ahead of print) future science group
10.2217/bmm-2016-0026 Biomark. Med. (Epub ahead of print) future science group Systematic Review Lan, Li, Ju et al. Publication bias was evaluated using the funnel plot with Begg’s bias test [19]. Results A total of 202 studies for CSCs and MVD were identified from a primary literature search of electronic databases PubMed, CNKI and the Wan-fang database (Figure 1). After manually screening the titles, abstracts and key data, 151 reviews, commentaries, meta-analyses or studies that were not relevant to the present analysis were excluded. Of 51 studies selected for detailed evaluation: 28 studies were excluded; these consisted of 16 studies that did not report MVD values, six studies lacking statistical analyses, two studies that lacked data describing the relationship between MVD and CSC marker expression, four studies were detected by immunofluorescence staining; seven additional studies were excluded as they lacked a suitable control group. The final meta-analysis included ten studies for MVD and CSC markers in human tumor tissues and six studies for MVD and CSCs in tumor transplantation animal models. Characteristics of the included studies The main characteristics of ten eligible studies [20–29] describing the association between CSCs and MVD in human tumor tissues are summarized in Table 1. Additionally, Table 2 shows the characteristics of six included studies [30–35] reporting the relationship between CSCs and MVD in tumor transplantation animal models. Finally, a total of 1331 cases from ten studies of MVD in human tumor tissues and a total of 78 cases from six studies of MVD in tumor transplantation animal models were included. These tem studies in which CSC marker expression was analyzed by immunohistochemistry were included and the Weidner method was used to calculate MVD. Correlation between the expression of CSCs markers & MVD in human tumor tissues The characteristics of the ten selected studies that were reporting the relationship between CSC markers and MVD in tumor tissue (Figure 2). The expression of CSC markers was associated with MVD count; high levels of expression of CSC markers indicated increased Figure 2. Meta-analysis of ten studies evaluating the association between CSC marker expression and MVD in human tumors. CSC: Cancer stem cell; MVD: Microvessel density; SMD: Standardized mean difference. Zhengquan Han (2015) Yiming Song (2015) Yunqin Huang (2013) Liang Pan (2013) Shiwu Wu (2012) Qing Li (2012) Lingjun Kong (2012) Huaming Wang (2011) Jun Dong (2011) Feng Li (2011) Overall (I-squared = 88.7%, p = 0.000) Note: Weights are from random effects analysis Study ID SMD (95% CI) Weight (%) 0.48 (0.26, 0.70) 0.20 (-0.20, 0.60) 0.53 (0.13, 0.92) 1.45 (0.67, 2.24) 1.68 (1.42, 1.94) 0.51 (-0.12, 1.13) 1.37 (0.65, 2.10) 2.68 (1.44, 3.92) 1.26 (0.76, 1.76) 1.15 (0.73, 1.56) 1.04 (0.63, 1.45) 11.93 11.06 11.07 8.47 11.76 9.59 8.92 5.79 10.43 10.99 100.00 -3.92 0 3.92
Relationship between microvessel density cancer stem cells in tumor angiogenesis Systematic Review MVD count.Pooled meta-analysis showed that,com-effect)indicated that the MVD count in the CSC pared with low expression of CSC markers,high groups was higher than in the tumor cell groups.The CSCs marker expression correlates with high MVD difference between the groups was statistically signifi- count(SMD=1.04,95%CI=0.63-1.45,Z=4.99,cant(SMD=3.69,95%CI-2.195.19,Z-4.83, p<0.0001).Meta-analysis of random effect model p<0.0001). indicated significant heterogeneity between the groups with high and low expression of CSC markers in MVD Subgroup analyses of MVD of human tumor count (X2 79.99,p 0.0001,I2=88.7%>50%;tissues tumor type random effect). In order to investigate the relationship between angio- genesis and tumor type,we determined the MVD count Correlation of expression of CSC markers with of tumor tissues according to tumor type.The CSC MVD in tumor transplantation animal models markers and MVD of tumor tissues varied according The characteristics of the six selected studies describing to the specific type of tumor (Figure 4).The subgroup the relationship between CSCs and MVD in tumor analysis was performed on four studies investigating transplantation animal models are shown (Figure 3).In the association between CSC marker expression and order to elucidate the association between CSCs and MVD count in brain tumor tissue.High CSC marker angiogenesis,data for in vivo models were required.In expression was significantly associated with high MVD the present meta-analysis,studies of five tumor types count(SMD-1.50,95%CI-1.05-1.94,Z=6.55, were included:brain tumor,hepatoma and cancers of p<0.0001).No significant heterogeneity was observed the lung,breast and cervix. between the studies (X2=4.34,p 0.227 >0.05, It is considered that CSCs possess stronger angio-I2=30.8%).Three studies analyzing the association genic capability than well-differentiated tumor between CSC marker expression and MVD count in cells.Meta-analysis using the random effect model breast cancer were included.The difference between (X2=17.31,p =0.004,I2=71.1%>50%;random high and low CSC marker expression was statisti- Study ID SMD (95%CI) Weight(%) Lin Lin (2015) 7.27(3.50,11.04) 9.76 Hao Song(2012) 2.04(0.94,3.15) 22.53 Feng Jin (2011) 1.97(0.40,3.54) 20.01 XuHe(2010) 5.65(3.34,7.96) 15.92 Weigi Nian (2009) 2.74(1.00,4.47） 19.09 Dawei Kong (2008) 5.55(2.56.8.53) 12.69 Overall (I-squared 71.1%,p =0.004) 3.69(2.19,5.19) 100.00 Note:Weights are from random effects analysis -11 0 11 Figure 3.Meta-analysis of six studies evaluating the association between CSCs and MVD in tumor transplantation animal models. CSC:Cancer stem cell;MVD:Microvessel density;SMD:Standardized mean difference. future science group www.futuremedicine.com 10.2217/bmm-2016-0026
www.futuremedicine.com 10.2217/bmm-2016-0026 Figure 3. Meta-analysis of six studies evaluating the association between CSCs and MVD in tumor transplantation animal models. CSC: Cancer stem cell; MVD: Microvessel density; SMD: Standardized mean difference. Lin Lin (2015) Hao Song (2012) Feng Jin (2011) Xu He (2010) Weiqi Nian (2009) Dawei Kong (2008) Overall (I-squared = 71.1%, p = 0.004) Note: Weights are from random effects analysis 7.27 (3.50, 11.04) 2.04 (0.94, 3.15) 1.97 (0.40, 3.54) 5.65 (3.34, 7.96) 2.74 (1.00, 4.47) 5.55 (2.56, 8.53) 3.69 (2.19, 5.19) 9.76 22.53 20.01 15.92 19.09 12.69 100.00 Study ID SMD (95% CI) -11 0 11 Weight (%) future science group Relationship between microvessel density & cancer stem cells in tumor angiogenesis Systematic Review MVD count. Pooled meta-analysis showed that, compared with low expression of CSC markers, high CSCs marker expression correlates with high MVD count (SMD = 1.04, 95% CI = 0.63∼1.45, Z = 4.99, p < 0.0001). Meta-analysis of random effect model indicated significant heterogeneity between the groups with high and low expression of CSC markers in MVD count (X2 = 79.99, p < 0.0001, I2 = 88.7% > 50%; random effect). Correlation of expression of CSC markers with MVD in tumor transplantation animal models The characteristics of the six selected studies describing the relationship between CSCs and MVD in tumor transplantation animal models are shown (Figure 3). In order to elucidate the association between CSCs and angiogenesis, data for in vivo models were required. In the present meta-analysis, studies of five tumor types were included: brain tumor, hepatoma and cancers of the lung, breast and cervix. It is considered that CSCs possess stronger angiogenic capability than well-differentiated tumor cells. Meta-analysis using the random effect model (X2 = 17.31, p = 0.004, I2 = 71.1% > 50%; random effect) indicated that the MVD count in the CSC groups was higher than in the tumor cell groups. The difference between the groups was statistically significant (SMD = 3.69, 95% CI = 2.19∼5.19, Z = 4.83, p < 0.0001). Subgroup analyses of MVD of human tumor tissues & tumor type In order to investigate the relationship between angiogenesis and tumor type, we determined the MVD count of tumor tissues according to tumor type. The CSC markers and MVD of tumor tissues varied according to the specific type of tumor (Figure 4). The subgroup analysis was performed on four studies investigating the association between CSC marker expression and MVD count in brain tumor tissue. High CSC marker expression was significantly associated with high MVD count (SMD = 1.50, 95% CI = 1.05∼1.94, Z = 6.55, p < 0.0001). No significant heterogeneity was observed between the studies (X2 = 4.34, p = 0.227 > 0.05, I2 = 30.8%). Three studies analyzing the association between CSC marker expression and MVD count in breast cancer were included. The difference between high and low CSC marker expression was statisti-