Tropomyosin isoform switching from larger isoforms (Tm1, Tm2, Tm3, Tm6) to smaller isoforms (Tm4, Tm5) was a transformation-induced change correlated with tumorigenicity in human fibroblasts.
We identified six tropomyosin (Tm) isoforms in diploid human fibroblasts. We used computerized microdensitometry of 2-dimensional protein profiles to measure the relative rates of synthesis and abundance of the individual Tm isoforms and actin, the two major structural constituents of microfilaments. In carcinogen-transformed human fibroblasts (HuT-14), the rates of synthesis of three Tm isoforms (Tm1, Tm2, and Tm6) were greatly decreased relative to normal diploid parental fibroblasts and to actin. In contrast, related nontumorigenic HuT fibroblasts which are "immortalized" and anchorage independent exhibited both slight down-regulation of Tm1 and Tm6 and 3.5-fold up-regulation of Tm3. Thus, Tm isoform switching from the predominance of the larger more avid Tm isoforms (Tm1, Tm2, Tm3, and Tm6) to the smaller, less avid Tm isoforms (Tm4 and Tm5) in microfilaments was a transformation-induced change correlated with tumorigenicity in human fibroblasts.
Leavitt et al. (Tue,) conducted a other in Tumorigenicity in human fibroblasts. Carcinogen transformation vs. Normal diploid parental fibroblasts and nontumorigenic immortalized fibroblasts was evaluated on Relative rates of synthesis and abundance of individual Tm isoforms and actin. Tropomyosin isoform switching from larger isoforms (Tm1, Tm2, Tm3, Tm6) to smaller isoforms (Tm4, Tm5) was a transformation-induced change correlated with tumorigenicity in human fibroblasts.
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