Expression Of PKB, PTEN And C-kit In Neurofibroma And Clinical Pathological Significance

Background and objectiveSolitary neurofibroma is a local solitary tumor without other characters of NF1, Few patients may have more than one neurofibroma. Solitary neurofibroma is a kind of benign tumor composed of perineurium cells and fibroblasts mainly. Recently the detailed pathogenesis of tumor is still obscure.Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder of nervous system. In 1987, Barker found the NF1 gene, which is the pathogenic gene of NF1, and located it in 17q^11.2. The NF1 gene has high mutation rate, and now, about 200 kinds of mutation have been found. Neurofibromin, the protein encoded by NF1, negatively regulates p21 ras activity by accelerating the conversion of ras-GTP to ras-GDP, so the NF1 gene can prevent the signal of karyokinesis from ras thought neurofibromin and control effectively the inordinate hyperplasia of cells. Now, it has been thought that the pathogenesis of NF1 is the mutation of NF1 gene influences the ordinary expression of neurofibromin, disturbs the signal transmit of ras pathway and effects the development of NF1. But the pathogenesis of tumor is still obscure.With the rapid development of molecular biology, the study of cell signal pathway has been major part of the pathogenesis study of tumor. In the study field of tumor pathogenesis, the phosphoinositide 3-kinase/protein kinase B (PI3K/PKB) cell signal pathway is a new one of cell signal pathways and has been the study focus gradually from 1980, and scientists have found that some factors of the pathway express abnormally in many malignancies. As the direct target protein, PKB becomes phosphorylated PKB after activation, and has many functions such as accelerating cell proliferation, preventing cell apoptosis, promoting the compound of protein and hepatin, adjusting cell cycle and so on. Phosphatase and tensin homolog deleted on chromosome ten (PTEN) gene is one of tumor suppressor genes and the functional absence of it is related to pathogenesis of tumor. It can let the lipid outcome of PI3K become dephosphorylation, and hold the cell up growth and survival. Proto-oncogeng protein c-kit coded by proto-oncogene c-kit is the receptor of stem cell factor (SCF). The integration of c-kit and SCF can act PI3K direct rapidly, and boost the cell signal conduction. In order to illuminate the pathogenesis of NF1 and solitary neurofibroma, we collect the neurofibroma tissue samples of NF1 and solitary neurofibroma, compared with normal skin tissues, evaluate the expression of p-PKB, PTEN and c-kit in the tissue samples and their dependability by means of SP immunohistochemistry method, which will help understand their effects on NF1 and solitary neurofibroma, offer valuable dates for the study of pathogenesis of NF1 and solitary neurofibroma, in the same time, and offer new target for the bioremediation of neurofibroma.Materials and methods1. NF1 neurofibromas and solitary neurofibroma were stained with usual HE.2. Immunohistochemistry (Streptomycin avidin-biotin-peroxidase complex, SP) method was used in this study to detect the protein expressions of p-PKB, PTEN and c-kit in paraffin specimens from 26 patients with NF1, 20 patients with solitary neurofibroma and 11 cases of normal skin as compare, and analyze the differences and relationships among the expressions of p-PKB, PTEN and c-kit in NF1, solitary neurofibroma and normal skin.3. The datas was analyzed by SPSS13.0 software package. Differences among groups were analyzed by using analysis of the Chi-squared test and FISH exact probability. The correlation analysis was analyzed by Spearman Correlation. The level of significant difference wasα=0.05, andα=0.0167 after x² division, P< 0.05 were deemed significant. Results1. The results of staining with usual HE: NF1 neurofibroma tissues and solitary neurofibroma tissues were similar in morphosis, composition, arrangement and general degree of hyperplasy of cells. They were all seen that shuttle cells ranged like striation or swirl. So it is sure that these paraffin specimens are from patients with NF1 and solitary neurofibroma.2. The masculine grains of p-PKB were mainly distributed in the cytoplasm of tumor cells. The normal skin tissue showed weak positive staining for p-PKB. The positive rate of p-PKB was 9.09% (1/11) in normal skin, 55.00% (11/20) in Solitary neurofibroma and 53.85% (14/26) in NF1 respectively. There were significant differences between solitary neurofibroma (or NF1) and normal skin (P< 0.0167). There was not significant difference between Solitary neurofibroma and NF1(P>0.0167).3. The masculine expression of PTEN could be found in the cytoplasm of skin cells mainly and parts of karyon. There was higher expression rate of PTEN in normal skin. It was 100% (11/11), and descended in solitary neurofibroma and NF1. They were 40.00% (8/20) and 42.31% (11/26). There were significant differences between solitary neurofibroma (or NF1) and normal skin (P<0.0167). There was not significant difference between solitary neurofibroma and NF1 (P>0.0167).4. The masculine grains of c-kit were mainly localized in the cytoplasm of tumor cells and small quantities of that were in the cell membrane. The low positive staining for c-kit was showed in normal skin tissue. The positive rates of c-kit were 9.09% (1/11) in normal skin, 60.00% (12/20) in solitary neurofibroma and 65.38% (17/26) in NF1 respectively. There were significant differences between solitary neurofibroma (or NF1) and normal skin (P<0.0167). There was not significant difference between solitary neurofibroma and NF1 (P>0.0167).5. In NF1 correlative analysis showed the expression of p-PKB had a positive relationship with the expression of c-kit (r=0.462, P<0.05) and had a negative relationship with the expression of PTEN (r=-0.456, P<0.05). In solitary neurofibroma correlative analysis showed the expression of p-PKB had a positive relationship with the expression of c-kit (r=0.698, P<0.05) and had a negative relationship with the expression of PTEN (r=-0.492, P<0.05).Conclusions1. There is lower expression of p-PKB protein in normal skin, but the expression rate rise in solitary neurofibroma and NF1 tissues, which indicate that the action of p-PKB is boosted up, it accelerates cell proliferation and apoptosis that controlled by PI3K/PKB pathway, the cell proliferates without control. So p-PKB may take part in the pathogenesis of solitary neurofibroma and NFL2. The higher expression of PTEN is found in normal skin, and then it declines in solitary neurofibroma and NF1 tissues, which indicate that the abnormal PTEN protein weaks function, so the proliferation and apoptosis of cells are accelerated. PTEN may play important role in the pathogenesis of solitary neurofibroma and NF1.3. There is lower expression of c-kit protein in normal skin, but the expression rate rise in solitary neurofibroma and NF1 tissues, which indicate that the action of c-kit may take part in the pathogenesis of solitary neurofibroma and NF1.4. In solitary neurofibroma and NF1 tissues, the expressions of p-PKB and c-kit positively correlate with each other and the expressions of p-PKB and PTEN negatively correlate, which indicate that p-PKB and c-kit can cooperate, and p-PKB and PTEN can resist each other in the pathogeny of solitary neurofibroma and NF1. With weakening function of PTEN and enhanced function of c-kit, the action of p-PKB is stronger; they influence the pathogenesis of solitary neurofibroma and NF1 corporately.5. The expressions of p-PKB, PTEN and c-kit in NF1 are assembly same as in solitary neurofibroma, which indicate that p-PKB, PTEN and c-kit maybe have no relation to occurrences of solitary neurofibroma and NF1, but to the developments of solitary neurofibroma and NF1. The uncommon signal conduction of c-kit and PI3K/PKB pathway result in the abnormal cell proliferation and apoptosis, which maybe the same way for the developments of solitary neurofibroma and NFL...