Time-lapse microcinematography of the effect of thiazolidine carboxylic acid (thioproline) upon tissue cultures.

This work deals with the effect of thiazolidine-4-carboxylic acid (thioproline) upon several in vitro established human cell lines. Times-lapse microcinematography is used to study the action of thioproline on HeLa cells, employing high doses during a short time, and continuous exposure to medium and small doses. The effect of thioproline in mixed cultures of HeLa cells and human lymphoblasts is described. Special attention is paid to the observed cell cycle phase specificity, and to the phenomenon described as reverse transformation that has been associated to the drug. Marked differences is the sensitivity to thioproline are observed for the different types of in vitro established cell lines. The effect is always produced during the G1 and S phases of the cell cycle. Cell changes are produced only after contacting with one another, and the biochemical reactions which are proper of cell contact inhibition of growth and/or genotypic reverse transformation were never observed, so that the mechanism of action of the drug has to be revised. From a morphodynamic point of view, thioproline is an interesting drug because it produces peculiar effects which differ markedly from those produced by the other cancer chemotherapy agents. Thioproline could prove to be useful for cancer chemotherapy if used in combination with other drugs, knowing that it is a low activity phase specific antineoplastic drug and not a drug producing reverse transformation.