| Summary: | 碩士 === 國立陽明大學 === 藥理學研究所 === 88 === Thymosin b-4 (Tb-4) is a small (4.9 kDa) and highly conserved acidic polypeptide originally isolated from calf thymus. Tb-4 interacts with monomeric G-actin and serves as a major actin-sequestering protein that inhibits actin polymerization and the formation of microfilaments. Since the dynamic changes in the polymerization state of actin are crucial for cell proliferation, differentiation and migration, may therefore play important roles in these events. Interestingly, recent studies have shown that Tb family (Tb-10) overexpression is a general event in human carcinogenesis.
To examine the effects of Tb-4 overexpression on the in vitro and in vivo phenotypic changes of tumor cells, human cervical carcinoma (HeLa) cells were stably transfected with a plasmid carrying sense Tb-4 cDNA. Two transfectants, designated respectively as S1 and S2 obtained after G418 selection, were subjected to further analyses. Overexpression of Tb-4 gene and its effect on the formation of stress fibers in S1 and S2 cells were demonstrated respectively by Northern hybridization and rhodamine-phalloidin staining. MTT assays showed that S1 and S2 cells grew faster than HeLa cells in regular media and they also survived longer than their parental cells in either low serum or serum-free media. Reduction in contact inhibition of these mutants was shown by a 2-fold increase in their saturation densities. Moreover, these mutant cells were less susceptible to cisplatin and doxorubicin but more susceptible to taxol than their parental cells. Interestingly, nodules with metastatic capability formed more rapidly from S1 and S2 cells than HeLa cells when implanted subcutaneously into nude mice.
Take together, our data suggest that overexpression of Tb-4 gene in HeLa cells not only changes their in vitro growth properties but also increases their in vivo malignancy.
|
|---|
