Expression Of HIF-1α And HIF-2α In Renal Cell Carcinoma And Its Relationship With Angiogenesis

Background and Objective Renal cell carcinoma is the most frequentsubstantive tumor of kidney. According to statistics, the incidence of renal tumors rank the second place in urologic tumors, accounting for about 2% of adult cancer. Invasion and metastasis are two important biologic characters of malignant tumor, they are the same for renal cell carcinoma. Lacking of typical clinical symptom, about 1/4 of the patients with renal cell carcinoma had metastasis when they visited doctor. The treatment of renal cell carcinoma is not satisfactory now. Understanding of the pathogenesis of renal cell carcinoma deeply and explore the method of early diagnosis and treatment of the disease are very necessary. Studying the molecular mechanism about invasion and metastasis of renal cell carcinoma is helpful to design and look for a new way to resist invasion and metastasis and to improve the prognosis.The pathogenesis of renal cell carcinoma is a progression with many steps and phases in which many factors participate in. There exists hypoxian microenvironment in many entity tumors due to structural and functional abnormality of vessel and increased oxygen consumption caused by rapid proliferation of tumor cell in it. Under these circumstances, various cytokines, which can promote growth and metastasis of tumor, are induced to release, therefore, tumor resistance to radiotherapy and chemotherapy is induced. Recently, we believe that tissue can produce HIF in hypoxic conditions. HIF can regulate the expression of a variety of hypoxia related target genes, so that the body can take a series of hypoxia adaptation reaction. The activity of HIF play an important role in maintenance of tumor cell energy metabolism, promote angiogenesis and promote tumor growth and metastasis. HIF is not only overexpressioned in tumor cells and metastases cells but also induced the abnormal gene expression in tumor tissues, meanwhile it have an important influence to the growth and apoptosis of tumor cells.There are there subtypes expressed in body of hypoxia-inducible factor, HIF-1,HIF-2 and HIF-3.αsubmit is functional submit. HIF-1αis a wide exist of hypoxia-inducible factor, but its expression was lower. HIF-2αexpressed in the wider organization, its expression has a significant difference in different tissue. HIF-3αis a hypoxia inducible subtype which was discovered recently. the expression of HIF-3αwas higher in the heart,skeletal muscle and lung tissue, but lower in the liver and kidney tissues. Resent studies have demonstrated that overexpression of HIF-1αare positively associated with invasion, metastasis and patient prognosis in many tumors, include renal cell carcinoma. But to our knowledge, until now, only few data exist on the correlation of HIF-2αprotein expression with invasion, metastasis and patient prognosis in renal cell carcinoma. The purpose of this study was to detect the expression of HIF-1αand HIF-2αin renal cell carcinoma and find their relationship with tumor angiogenesis and metastasis, in order to finding the reliable molecular markers to assessment of renal cell carcinoma metastasis and prognosis, getting the new target of anti-tumor therapy.Materials and Methods 60 cases with RCC were selected who had performed operation in our hospital between July 2005 to May 2006, of which 41 male, 19 female. All the patient didn't received any form of radiotherapy, chemotherapy and immunotherapy. Of which 43 were renal clear cell carcinoma, 17 were renal granule cell carcinoma. There were lymph modes metastases in 11 cases, and no lymph nodes metastases 49 cases. UICC and AJCC stage I were in 31 cases, stage II in 17 cases, stage III in 9 cases, stage IV in 3 cases. Fuhrman grade 1 were in 19 cases, G₂ in 32 cases, G₃ in 9 cases. 15 cases of normal renal tissues were regard as control. All the tissues were fixed in 10% formalin and embedded in paraffin. 4 micrometers sections were made from representative blocks of each case. Immunohistochemical methods were used to detect the expression of HIF-1α,HIF-2αand CD34. the data were analyzed by software SPSS 10.0. The t-test ,chi-square test and Fisher's exact probabilities were used to process the data. The correlation among HIF-1α, HIF-2αand CD34 were analyzed by Spearman correlation.α=0.05 were considered as the significant test level.Results1. The expression of HIF-1αand HIF-2αwere not found in normal renal tissues. In renal cell carcinoma group positive rates of HIF-1αexpression was 61.7% (37/60). There were statistic difference between expressions of HIF-1αin renal cell carcinoma group and normal renal tissues group (P<0.01). The positive rates of HIF-2αin renal cell carcinoma group was 78.3% (47/60). There was statistic difference between expressions of HIF-1αin renal cell carcinoma group and normal renal tissues group (P<0.01).2. In renal cell carcinoma group positive rates of HIF-1αexpression and HIF-2αexpression were 61.7% (37/60) and 78.3% (47/60) respectively. There was statistic difference (x² =3.97, P<0.05).3. In the groups with and without lymph nodes metastases, the positive rates of HIF-1αexpression were 72.7% (8/11) and 59.2% (29/49). The difference between the two groups was no significant(x²=0.248, P>0.05). In the groups with and without lymph nodes metastases, the positive rates of HIF-2αexpression were 100% (11/11) and 53.1% (26/49). The difference between the two groups was significant (P=0.0025).4. The MVD in the HIF-2αpositive expression group (73.3±15.2) of renal cell carcinoma was significantly higher than that in HIF-2αnegative group (53.1±13.4). there was a positive correlation in them though Spearman analyze (r_s=0.545, P<0.01). The MVD in the HIF-1αpositive expression group and HIF-1αnegative group were 70.5±14.8, 66.4±20.1 respectively, no significant difference was observed between them. there was a positive correlation in them though Spearman analyze (r_s=0.181, P>0.05).5. In the groups of clear cell carcinoma and granule cell carcinoma, the positive rates of HIF-1αexpression were 69.8% (30/43) and 41.2% (7/17). The difference between the two groups was significant (x² =4.21, P<0.05). In the groups of clear cell carcinoma and granule cell carcinoma, the positive rates of HIF-2αexpression were 88.3% (38/43) and 52.9% (9/17). The difference between the two groups was significant (x² =7.04, P<0.05).6. The MVD in renal cell carcinoma tissue was 19.3±5.8, whereas in normal tissues was 19.3±5.8. A significant difference was observed in them (t=18.712, P<0.05) .The MVD in clear, granule renal carcinoma were 69.4±15.2, 67.7±21.3 respectively, no significant difference was observed between them (t=0.351, P>0.05) . The MVD in group with lymph nodes metastasis (85.1±17.1) was significant higher than the MVD in group without lymph nodes metastasis (65.3±14.8) (t=3.913, P<0.05).7. Spearman correlation analysis showed that HIF-1α(r_s=0.104,0.172, P>0.05) and HIF-2α(r_s=0.253,0.223, P>0.05) were not correlated with the Fuhrman grade and TNM stage of renal cell carcinoma. Conclusion1. The expression of HIF-1αand HIF-2αwere not found in normal renal tissues, but were high in renal cell carcinoma. The expression of HIF-2αin renal cell carcinomas was much higher than that of HIF-1α.2. There was a positive correlation between the expression of HIF-2αand MVD. HIF-2αplay a key role in the oncogenesis and progression of renal cell carcinoma.3. The expression of HIF-1αand HIF-2αwere not correlated with the Fuhrman grade and TNM stage of renal cell carcinoma.