[Structural disorder of the endoplasmic sheath of microfilaments during neoplastic transformation]

Neoplastic transformation of cultured cells leads to a disorganization or loss of actin bundles. The platinum replica technique was used to study transformation-dependent changes of other structures of actin cytoskeleton, that is the active edge actin meshwork and endoplasmic microfilament sheath. Cultures of 3 normal and 10 neoplastic cell lines were used. While the structure of the active edge meshwork was found unaltered in transformed cells, the endoplasmic sheath was very sensitive to transformation. It appeared much looser than in normal cells, to become fragmented up to a complete loss in certain cases. The fine structure of the sheath in transformed cells was also changed. It was composed of short random microfilament fragments instead of long parallel microfilaments typical for normal cells. The degree of sheath alterations varied among different transformed cells lines. A certain correlation could be observed between sheath changes and other signs of neoplastic transformation.