| Background: Transforming growth factor-β(TGF-β) is a number of polypeptide factors. So far, there are five subtypes that have been discovered, including TGF-β1, TGF-β2, and TGF-β3 in mammals. Among these subtypes, TGF-β1 has been paid more attention in human, which has different effects on different types of cells by inhibiting or promoting cell proliferation. TGF-βreceptors and Smads mediate and regulate the TGF-βsignaling from the membrane receptors to nuclei. Smads have been divided into three distinct groups: the receptor-activated Smads (R-Smads), the common-partner Smad (Co-Smad) and the inhibitory Smads (I-Smads). R-Smads, such as Smad2 and Smad3, Co-Smad——Smad4, and I-Smad, such as Smad7 are the key molecules in TGF-βsignaling. TGF-β/Smad signaling pathway plays an important role in maintaining the homeostasis of epidermis, and takes part in the epithelial tumor formation. More alterations in the TGF-βsignaling pathway might lead to tumorous hyperplasia due to elimination of growth inhibition by TGFβ1.In our previous study, we found altered expressions of TGF-βRs,R-Smads, Co-Smad and I-Smad in human cutaneous squamous cell carcinoma (SCC) in situ. Whether these alterations only exist in the tumor formation in vivo, or ascribe to the intrinsic featues of the tumor cells in squamous cell carcinoma is not clear. Whether established tumor cell line derived from cutaneous squamous carcinoma has or still maintains these alterations in TGF-β/Smad signaling remains unknown.Objective: To investigate the expressions of TGF-βRs, R-Smad, Co-Smad in squamous cell carcinoma cells——A431 cell line, and to observe the effects of TGF-β1 on cell proliferation and the expressions of TGF-βRs and related Smads in A431 cell lines, for an insight into the mechanism of aberrant TGF-βsignaling and tumorous hyperplasia in cutaneous SCC. Method: Reverse transcription (RT) and real-time polymerase chain reaction (PCR), and Western blotting were utilized to detect expression of TGFβR, R-Smad, Co-Smad mRNA and protein in A43 cell line and human immortalized keratinocytes HaCaT cell lines. Then RT-Real time PCR and MTT were utilized to assess the cell proliferation and expressions of TGF-βRs, R-Smad, Co-Smad and I-Smad mRNA in the cells mentioned above after TGF-β1 treatment.Results: RT-PCR and Western blotting revealed that expressions of TGF-βRI, TGF-βRII, Smad2, Smad3, Smad4 mRNA and protein were significantly down-regulated, in cutaneous SCC A431 cell line compared with HaCaT cell line. Real-time PCR showed that after incubation of TGF-β1, the expressions of TGF-βRs, R-Smad, Co-Smad in both cells were gradually down-regulated with the raised concentrations,but expression of Smad7 was just up-regulated. Compared with the control cells, the changes were more significant in A431 cell line. MTT assay showed that with raised concentrations of TGF-β1 and elongated treatments of TGF-β1, the cell proliferation was gradually inhibited by TGF-β1 in HaCaT cells, but not in A431 cells.Conclusion: Decreased expressions of TGF-βRs, R-Smad and Co-Smad existed in cultured human squamous carcinoma cells——A431 cell line. The decreased expressions of these molecules... |
PDF Full Text Request