| Background: Insulin like growth factor I receptor (IGF- I R) is a tyrosine kinase transmembrance receptor, which consists of a b heterodimers( a2 b2). It presents in a wide variety of cell types and mediates mosts of the effects of the IGF- I and IGF- II in vivo.In general, the IGF system plays an important role of acute anabolic effects on protein and carbohydrate metabolism, as well as long term effects on cell replication and differentiation. Also, it is essential for fetal development. Reports shown that the deletion of the IGF- I receptor can lead to extreme growth retardation and lethality.On the other hand, overexpressed and consistently activated IGF- I receptor is known to generate a transformed phenotype in various cell types. Evidence has been proved that the overexpressed IGF- I receptor plays a crucial role in many types of tumor cell in different ways, such as, mediating mitogenesis, maintaining a transformed phenotype and protecting it from apoptosis. But the regulation mechanism of this receptor remains unclear. So, the in-depth researches on the regulation of this receptor may provide us new area of cancer diagnosis and treatment. Objective: To study on the expression of IGF- I R with the stimulation of exogenous rIGF- I and serum depravation in A549 cells and lymphocytes, and to discuss their significance in the tumor progression. Material and Methods: The human lung adenocarcinoma cell lineA549 was purchased from Cell Bank of Chinese Academic of Science (CBCAS, shanghai) and the peripheral blood lymphocytes (PBL) were obtained from health individuals. During the research, the A549 cell was routinely cultured in RPMI 1640 medium supplement with 10% fetal calf serum (PCS), and the lymphocyte was cultured with RPMI 1640 medium supplement with 4% human "AB" serum. The cells were seeded at a density of 106-107(cells/well) in 6-well cell culture plate,and the total volume was 3 ml. After the cell cultured for 24 hours, the culture medium was replaced by serum free medium and then continued to culture for 12 hours.In research part one, to identify the optimal time for rIGF- I to exert its action, rIGF- I was added to the above culture medium with the fmial concentration of 20 ng/ml. After 0, 2, 4, 8 and 16 h, cell was harvested and the RNA was obtained using Tripure RNA isolation kit. Then the isolated RNA was amplified by RT-PCR methods with the one-step access RT-PCR kit. And the transcriptional level of IGF- I R was quantified according to the ratio of the densities of IGF- I R and internal control gene asparagines synthetase (AS). We also studied the impact of serum deprivation by comparing the transcriptional level of IGF- I R on the cells which were cultured in the medium with or without serum. In the second part of our research, we studied the influence of different concentration of IGF- I on the expression of its receptor. rIGF- I was added to the culture medium with the fmial concentration of 0, 5, 20, 80 and 160 ng/ml. Then, the cells were harvested after the cells were cultured for 8 hours, and the levels of IGF- I receptor mRNA were measured as above according to the optimal time. Results: 1. After the culture medium was replaced by the serum freemedium, the expression of IGF- I receptor can be up-regulated to 2 times to its basal level in A549 cell and 4 times in lymphocyte. 2. 20 ng/ml of rIGF- I can down-regulate the transcriptional level of IGF-I receptor in lymphocytes within 8 hours. 3. There were no differences between the IGF-1 receptor mRNA levels of A549 cells with or without 20 ng/ml rIGF- I in 16 hours. 4. A549 cell and lymphocyte shown different responses to the stimulation of different rIGF- I concentration. The transcriptional level of IGF- I receptor of lymphocyte can be down-regulated by rIGF- I . The eminent effect would appear in lymphocyte when the rIGF- I concentration was up to 20 ng/ml, while in A549 cell, there was no effect can be observed, even when the concentration of rIGF- I was up to 320 ng...
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