Lack of reverse transformation after treatment of A 549 human alveolar carcinoma cells with thioproline.

Clonal growth in anchorage dependent (on plastic) and independent (in soft agar) conditions of A 549 cells from a human alveolar carcinoma by thiazolidine-4-carboxylic acid (thioproline) was determined in order to check whether this drug was able to induce reversion towards a normal phenotype of in vivo growth, as described by Gosalvez in HeLa cells. The colony formation on plastic, the ability to form three-dimensional clones in soft agar and cell division in mass culture, were inhibited at similar rates when the cells were grown in the presence of increasing concentrations of thioproline. The morphology of cell clones arising on plastic in the presence of thioproline did not differ from that of untreated cell clones. This indicated that thioproline was unable to provoke 'reverse' transformation of A 549 cells in vitro.