Expression And Significance Of TIP30, VEGF And CD34 In Brain Astrocytomas

Objective: Astrocytoma is the most common human brain tumor, accounting for about 35.26%~60.96% of all brain tumors in our country. The biological behavior of astrocytoma is quite special. All the astrocytomas, whether well differentiated or poor differentiated show invasive growth pattern. Though multimodality treatment (including surgical resection chemotherapy, and radiotherapy, etc) have been widely used, the outcome of the patients with astrocytoma are still not good enough because of local recurrence and invasive growth.Recently, neovascularization became the hot spot in research of the invasive growth of astrocytoma. TIP30, also called HTATIP2 (HIV-1 Tat interactive protein 2), was a transcriptional cofactor with 242 amino acid residues. As a tumor metastasis suppressor gene, it has potential effect in inhibiting angiopoiesis. TIP30 is a gene with Ser/Thr protein kinase activity, that could bind to the largest RNA polymeraseⅡsubunit and phosphorylate the heptapeptide repeats of the C-terminal domain of its. Thus it can regulate the expression of genes involved in angiogenesis on the specially physiological and pathological manner. TIP30 could inhibit the transcription of a series of proangiogenic factors such as VEGF and induce the expression of a series of antiangiogenic factors such as BAI1 at the same time. Thus it played an important role in inhibiting the invasive outgrowth of tumor cells by inhibiting angiopoiesis. Vascular endothelial growth factor (VEGF) induce angiogenesis through promoting the proliferation of vascular endothelial cells. It was one of the proangiogenic factors with the highest effect and specificity and has close relation to the invasion of tumor. Research showed that TIP30 could suppress the transcription of VEGF. Microvessel density (MVD) is quite useful parameter in the evaluation of angiogenesis. Up to now, several vascular endothelial cell markers such as CD31, CD34 and CD105 were used for MVD. CD34 was found at first in stem hematopoietic cell and were commonly expressed in normal and tumor vascular endothelial cells. It was found that the expression of TIP30 was decreased in many human tumors such as melanoma, breast carcinoma, colorectal carcinoma as well as hepatocarcinoma. Up to now, no study on the expression and significance of TIP30 in astrocytoma was seen.To further explore the possible mechanism of the invasive growth of astrocytomas from the point of angiogenesis, the expression of TIP30, VEGF and CD34 and their significance in astrocytoma were studied.Method: Archival paraffin embedded tissue blocks of astrocytoma with original clinical and pathological records as well as normal brain tissue from the Department of Pathology, the Second Hospital, Hebei Medical University in the period from Dec, 2005 to Jan, 2007 were included in this study. All the slides of the cases included in this study were reviewed by two experienced pathologists according to 2000 WHO criterion and the diagnosis confirmed. Among the 71 cases of astrocytomas, 25 cases were gradeⅡ, 23 cases were gradeⅢ, and the other 23 cases were gradeⅣ. Nineteen cases of normal brain tissue from the patients with brain accidents were used as control.The expression of TIP30, VEGF and CD34 was immunohistochemically studied in 71 cases of astrocytoma of different grades and 19 cases of normal brain tissue with ElivisionTM plus two-step method. The possible relationship among TIP30, VEGF and CD34 expression and pathological features in astrocytomas were analyzed.The experimental data were statistically analyzed with SPSS 11.0 edition.Results:1 Expression of TIP30 in brain astrocytoma and normal brain tissuePositive expression of TIP30 could be seen in cytoplasm of neuroglial cells and neurons of the 19 normal brain tissues. Among the 71 cases of astrocytoma, 24 cases showed positive expression of TIP30. The positive expression rate of TIP30 in astrocytoma was 33.80% (24/71), and it was significantly lower than that in normal brain tissue (χ2=26.32, P<0.01). Positive expression rate of TIP30 in astrocytoma of different grades was 52% for gradeⅡ, 34.78% for gradeⅢand 13.04% for gradeⅣ respectively. The positive expression of TIP30 in astrocytoma was decreased as the tumor grade increased (χ2=29.44, P<0.05). The positive expression rate of TIP30 in high grade(Ⅲ+Ⅳ) of astrocytoma was found significantly lower than that in low grade(Ⅱ) (χ2=5.71, P<0.05).2 Expression of VEGF in brain astrocytoma and normal brain tissueThe positive expression rate of VEGF in 19 cases of normal brain tissue was only 15.79% (3/19), while the positive expression of VEGF astrocytoma reached 88.73% (63/71), which was significant higher than that in normal brain tissue(χ2=40.78, P<0.05). The positive expression rates of VEGF in astrocytoma were increased as the pathological grade increased. The positive expression rate was respectively 72%, 95.65% and 100% for gradeⅡ, gradeⅢand gradeⅣastrocytoma. Significant differences in the positive expression rate of VEGF were found among astrocytomas of different grades according to statistic analysis (χ2=11.01, P<0.05). The positive expression rates of VEGF in gradeⅢand gradeⅣwere significant higher than that in gradeⅡ(χ2=4.83, P<0.05 andχ2=7.54, P<0.05). While no significant difference in the expression of VEGF was seen between gradeⅢand gradeⅣ(χ2=1.02, P>0.05).3 MVD in brain astrocytoma and normal brain tissueMicrovessel density (MVD) by CD34 was counted in normal brain tissue and astrocytoma. The mean MVD value in normal brain tissue was 10.41±3.81, while the mean MVD value in astrocytoma was 31.89±18.28. Significant differences were found between the two groups mentioned above (t=5.07, P<0.05). As the pathological grade of the astrocytoma increased, MVD increased accordingly. The mean MVD in Grade II, III and IV group was 11.41±8.58, 17.45±9.7 and 26.61±13.34 respectively. Significant differences of MVD were found among astrocytomas of different grades (F=101.35, P<0.05). Further statistic analysis showed that MVD in gradeⅢand gradeⅣwere all higher than that in gradeⅡ(q=3.59, P<0.05 and q=9.05, P<0.05). MVD in gradeⅣwas higher than that in gradeⅢ(q=5.33, P<0.05).4 Relationship among the expression of TIP30, VEGF and CD34 in astrocytomaAmong 24 TIP30 positive expression astrocytoma cases, 21 cases showed VEGF positive expression, 3 cases showed VEGF negtive expression. Among 47 TIP30 negtive expression astrocytoma cases, 42 cases showed VEGF positive expression, 5 cases showed VEGF negtive expression. According to the experimental data, statistical analysis showed that there was negative correlation between the expression of TIP30 and VEGF in astrocytoma(r=0.428, P<0.05).CD34-MVD in 24 TIP30 positive expression astrocytoma cases was 19.15±8.74; CD34-MVD in 47 TIP30 negtive expression astrocytoma cases was 20.15±10.22. There was no correlation between TIP30 and CD34-MVD in astrocytoma(r=0.065, P>0.05).CD34-MVD in 63 VEGF positive expression astrocytoma cases was 21.06±9.87; CD34-MVD in 8 VEGF negtive expression astrocytoma cases was 11.45±6.12. Positive correlation was found between VEGF and CD34-MVD in astrocytoma according to the experimental results(r=0.684, P<0.01). And it has statistical significance.Conclusions:1 The positive expression rate of TIP30 in astrocytoma was significantly lower than that in normal brain tissue. And the positive expression rate of TIP30 was significantly decreased as the pathological grade of the astrocytoma increased, suggesting that TIP30 may be involved in the tumorigenesis and progression of astrocytoma.2 The positive expression of VEGF and MVD in astrocytoma is significantly higher than that in normal brain tissue. As the pathological grades increased, the positive expression and MVD value in astrocytoma increased accordingly. Thus, high VEGF expression and MVD angiogenesis may be contributing factors to the invasive growth of astrocytoma.3 The expression of TIP30 and VEGF was negatively correlated in astrocytoma.