Expression Of ING4 And HIF-1a In Human Brain Astrocytoma

Background and ObjectivesAstrocytoma is a common highly malignant neuroepithelial tissue tumor in central nervous system and its prognosis is poor because of being uncompletely resected by surgical operation.With the development of tumor molecular biology, it is increasingly recognized that the formation of tumors related to many factors, such as the normal cell cycle uncontroled, tumor angiogenesis, the tolerance of the tumor hypoxia environment, as well as the loss of cell contact inhibition and so on. Oncogene activation and anti-oncogene inactivation play a key role in tumor formation and a variety of cytokines involved in this process. Inhibitor of growth 4(ING4) is discovered as a member of the growth inhibitor family in recent years, which may play very important roles in regulating cell cycle progression, promoting apoptosis, inhibiting angiogenesis and restoring cell-cell contact inhibition so it is an important tumor growth inhibitory factor. The expression activity of HIF-1a can be enhanced by the general hypoxia environment inside tumor. HIF-la can promote tumor proliferation and invasion by promoting tumor angiogenesis, relieving the state of tumor hypoxia and balancing oxygen demand of tumor cells. The abnormal expression of ING4 and HIF-1a are closed associated with the biological behavior of malignant tumors. Studies have found that ING4 can reduce expression of IL-8 by inhibiting the activity of HIF-1a, thereby interfere formation of tumor blood vessel. The specific mechanism is not entirely clear in this process. In order to explore the development and progression of astrocytoma, we examine the expression of ING4 and HIF-1a by means of immunohistochemistry and RT-PCR so that we can discuss the relationship between pathology classification and their correlations. In turn, we can guide clinical practice and provide a new way of diagnosis and treatment of astrocytoma.Materials and MethodsThe specimens of forty-five astrocytoma are obtained by surgical resection from January to September 2009 in Department of Neurosurgery, the Second Affiliated Hospital of Zhengzhou University. All cases are primary cases without preoperative radiotherapy and chemotherapy. Part of the specimens are fixed in 10%neutral formalin and embedded by paraffin.The other part of the specimens are quickly placed in liquid nitrogen tank, then are reserved in -80℃refrigerator. According to the WHO classification of central nervous system tumors in 2000, gradeⅠ-Ⅱspecimens of 24 cases were the low-malignant group and gradeⅢ～Ⅳof 21 cases were the high-malignant group. While non-tumour brain tissues of 11 cases were set to the control group. Non-tumour brain tissues were taken from brain trauma, cerebral hemorrhage patients who are decompressed in skull during surgical procedure. The protein and mRNA expression of ING4 and HIF-1a are respectively detected by immunohistochemistry and RT-PCR in non-tumour brain tissues of 11 cases and astrocytoma specimens of 45 cases. SPSS 13.0 statistical software was used, and significant level is a=0.05.Results1. Immunohistochemistry Results:ING4 protein were detected in all non-tumour brain tissues(100%)which is significantly higher than positive expression rate in astrocytomas (42.2%), and the positive expression rate(58.3%) inⅠ～Ⅱgroup was higher than inⅢ-Ⅳgroup(23.8%). By statistical analysis, there were significant differences (P<0.05). HIF-1a protein expression was not found in all non-tumour brain tissues(0) which is significantly lower than positive expression rate in astrocytomas (71.1%), and the positive expression rate of HIF-la inⅠⅡgroup(54.2%)was lower than inⅢ～Ⅳgroup(90.5%). The differences were significant by statistical analysis (P< 0.05).2.RT-PCR Results:In the non-tumour brain tissue, astrocytoma,Ⅰ～Ⅱgroup andⅢ～Ⅳgroup, the expression volume of ING4 mRNA was 1.19±0.22,0.62±0.34, 0.78±0.27 and 0.43±0.32 respectively. The differences were significant between non-tumour brain tissue and astrocytoma, as well asⅠ～Ⅱgroup andⅢ～Ⅳgroup (P<0.05) by statistical analysis. In the non-tumour brain tissue, astrocytoma,Ⅰ～Ⅱgroup andⅢ～Ⅳgroup,the expression volumes of HIF-la mRNA was 0.26±0.16,0.70±0.33,0.46±0.23 and 0.98±0.15 respectively. There were significant differences between non-tumour brain tissue and astrocytoma, as well asⅠ～Ⅱgroup andⅢ～Ⅳgroup (P<0.05) by statistical analysis.3. Correlation analysis:ING4 gene mRNA was expressed in a high level and HIF-la expression tended to decrease in the low-grade astrocytoma samples. ING4 gene mRNA was expressed in a low level and HIF-1a expression tended to increase in the high-grade astrocytoma samples. Statistically, moderate negative correlation was showed between them, and correlation coefficient of Pearson was -0.553 (P< 0.05).Conclusions1. ING4 expression reduces or misses in astrocytoma. The higher pathological grade is, the lower ING4 expresses. The expression activity of HIF-1a is increased in astrocytoma. The higher malignant degree of astrocytoma is, the higher ING4 expresses.2. Negative correlation was showed between the expression of ING4 and HIF-1a in astrocytoma. The decline of ING4 expression and increase of HIF-1a activity are not isolated. ING4 maybe play a role in anti-tumor by inhibiting the activity of HIF-la.