A comparison of cAMP phosphodiesterases in normal, malignant, and somatic cell hybrids.

Hybrids (PCM) between a malignant mouse lymphoma suspension cell line (P388F-36) and a normal Chinese hamster fibroblastic cell line (Ch23) have already been isolated in this laboratory. Investigations were carried out on the cAMP phospodiesterases of the parents and two of these hybrids--PCM2 and PCM3. PCM3 shows a rather unusual growth characteristic in that a considerable proportion of the cells exist at any one time either in suspension or only loosely attached to the substratum, the remaining cell population existing in a monolayer form. It was found that each cell line exhibited multiple forms of the enzyme with varying affinities for cAMP. Both parents, although different, contained high-, low-, and extra-high apparent Km forms of the enzyme. The hybrids exhibited characteristics of both parental systems but were different from each other. Neither hybrid exhibited a high-Km enzyme, but both exhibited two low-Km forms. There was also a slight variation between monolayer and suspension cells of PCM3 hybrid. An attempt has been made to explain these phenomena with respect to hybridization and the growth characteristics of the cells.