Expression Of Vascular Endothelial Growth Factor-C And Its Receptor VEGFR-3 In Cervical Squamous Cell Carcinoma And Their Clinical Significance

BackgroundCervical carcinoma is one of the commonest malignant tumor in female reproductive system, and the squamous cell carcinoma is the commonest histological type.The prognosis of cervical squamous cell carcinoma is significantly related to invasion and metastases,and invasion of lymphatic vessels by tumor cells and subsequent development of lymph node metastases are major pathway of malignant tumor spread.It is well established that lymphangiogenesis,the formation of new lymphatic vessels,play an important role in metastases and progress of malignant tumors.Vascular endothelial growth factor-C(VEGF-C)is a member of the VEGF superfamily,and involves physiological and pathological lymhphangiogenesis via vascular endothelial growth factor receptor-3(VEGFR-3).VEGF-C play an important role in lymphatic metastasis.VEGFR-3 belongs to the VEGF tyrosine kinase receptor family.It is expressed predominantly in the endothelium of lymphatic vessels,and has been proposed to be a specific molecular marker for lymphatic endothelial cells.A positive correlation of VEGF-C protein levels with lymph node metastasis has been found in a variety of carcinomas including lung cancer,gastric cancer,cervical cancer,prostate cancer etc.Relatively little is known,however,about the relationship between VEGF-C expression and lymphangiogenesis and lymphatic metastasis in cervical invasive squamous cell carcinoma.We tested this hypothesis by immunohistochemically evaluating expressive levels of VEGF-C and its receptor VEGFR-3 in cervical invasive squamous cell carcinoma,cervical intraepithelial neoplasia(CIN)and normal cervical squamous epithelium.Materials and methodsAll specimens in present study had been collected from the pathology department of the Jinhua people hospital and Jinhua central hospital.Specimens of invasive cervical squamous cell carcinoma,CIN tissue were obtained from excision biopsy procedures or uterine excision. Normal cervical tissues were selected from specimen of uterine excision of patients with uterine leiomyoma.None of the patients with invasive cervical squamous cell carcinoma had received any preoperative therapy.The expression of VEGF-C and its receptor VEGFR-3 were immunohistochemically examined in selected samples of cervical lesions.All specimens were fixed in neutral 4%buffered formaldehyde.Invasive cervical squamous cell carcinoma(from 66 patients and CIN(from 20 patients)were diagnosed by two pathologists.Grading of invasive cervical squamous cell carcinoma was done according to procedure of FIGO.The two respective grading observers were blinded in scoring all slides for VEGF-C staining with respect to VEGFR-3.ImmunohistochemistryThe expression of VEGF-C and VEGFR-3 were performed immunohistochemically in paraffin-embedded specimens fixed in neutral 4%buffered formaldehyde.Histological slides, 4μm in thickness,were daparaffined in xylene.Slides were heated in 0.01 M citrate buffer for 10 min in a microwave oven,and endogenous peroxidase was blocked with methanol containing 3% hydrogen peroxide for 5 min.For immunohistochemical detection of VEGF-C and VEGFR-3, specimens were incubated with a polyclonal anti-VEGF-C(Lone:41181066),and polyclonal anti-VEFR-3(Clone:41090982)in a dilution of 1:200 overnight at 4℃.Visualization of bound antibodies was performed by using Envision two-step method.As chromogen,diaminobenzidine was used to develop visualization.As positive control,a specimen of lymph node was used.As appropriate negative controls,first antibodies were substituted by PBS buffer solution.QuantificationFor VEGF-C staining,only cells with completely darkly stained cytoplasmic were regarded as positive.The immunohistochemical results for VEGF-C protein were classified as follows:-,no staining or cytoplasmic staining less than 10%of total cells;+,cytoplasmic staining in 11-30%of total cells;++,cytoplasmic staining in 31-50%of total cells;+++;cytoplasmic staining in more than 50%.For the determination of intratumoral microvessel numbers,the most vascular areas within a section were selected and counted under a light microscope with a 100-fold magnification.The average numbers were recorded for each case.Result evaluation of VEGF-C expression and vessel counting was performed independently by two investigators.Statistical MethodsAll statistical calculations were carried out using SPSS 11.0 software.To evaluate whether the frequency of cells with the elevated levels of VEGF-C and VEGFR-3 positive microvessel numbers were increased during cervix carcinogenesis,x~2 test and T test were performed, respectively.The Spearman rank correlation coefficient was used to analyze the relation between VEGF-C and VEGFR-3.P values of less than 0.05 were regarded as statistically significance. ResultsThe positive expressive rate of VEGF-C was 75%in cervical invasive squamous cell carcinomas,while that of VEGF-C expression was 30%,41.7%,41.7%and 45%in normal cervical tissue,CINⅠ,CINⅡand carcinoma in situ,respectively.The difference between the invasive squamous cell carcinoma and the normal cervical tissue in VEGF-C expression was statistically significant(p＜0.01).The expression level of VEGF-C in cervical squamous carcinoma was positively correlated with the positive number of stromal lymphatic vessels stained by VEGFR-3.Enhanced expressions of VEGF-C in cervical squamous cancer cells and stromal VEGFR-3-positive lymphatic proliferation were both positively associated with poor clinical stages and regional lymph node metastasis.(Table 1 and 2).a The correlation of VEGF-C expression between normal cervical tissue and invasion cancer, X~2=9.741,P＜0.01;b The correlation of VEGF-C expression betweenⅠstage andⅢstage,X2 =10.213,p＜0.01;c The correlation of VEGF-C between lymphatic metastasis negative and lymphatic metastasis positive,X2=7.956,p＜0.01;d The correlation of VEGFR-3 positive vessels between normal cervical tissue and invasion cancer,t=4.976,P＜0.001;e The correlation of VEGFR-3 positive vessels betweenⅠstage andⅢstage,t=4.632,P＜0.001;f The correlation of VEGFR-3 positive vessels between lymphatic metastasis negative and lymphatic metastasis positive,t=9.723,p＜0.001;r=0.614 P=0.000Conclusions(1)The expressive level of VEGF-C protein was remarkably increased in cervical spuamous cell carcinoma,which suggested that VEGF-C protein expression should be involved in invasion of cervical squamous cell carcinoma.(2)The VEGFR-3 positive microvessel numbers in cervical spuamous cell carcinoma were increased significantly higher than normal cervical tissue and CIN lesions,which suggested that enhanced lymphangiogenesis should play an important role in invasion of cervical squamous cell carcinoma.(3)The enhanced expression of VEGF-C and VEGFR-3 positive microvessel numbers in cervical spuamous cell carcinoma were associated with FIGO stage and lymph node metastasis.(4)The up-regulation of VEGF-C protein was intimately related to VEGFR-3 positive microvessel numbers in cervical squamous cell.