Deposition of fibronectin in the course of reverse transformation of Chinese hamster ovary cells by cyclic AMP.

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Abstract
The Chinese hamster ovary (CHO) cell, like other transformed cells, has lost the fibronectin deposit around its membrane. Treatment with cyclic[c]AMP derivatives restores the typical fibroblastic deposit of fibronectin. Thus, the reverse transformation process induced by cAMP in the CHO cell restores this important property and other morphological, biochemical and growth behavioral characteristics of the normal fibroblastic state. The fibronectin deposit occurs significantly later in time than do other characteristics of the reverse transformation reaction and may therefore reflect a metabolic action that requires other cAMP effects to precede it. The restoration of fibronectin deposition in response to cAMP derivatives is also exhibited by vole cells transformed by avian sarcoma virus, but it is not by HeLa cells. Addition of Colcemid, which disrupts microtubules, to CHO cells containing a fibronectin deposit induced by cAMP derivatives causes little or no erosion of the deposit, but cytochalasin B, which disrupts 5-nm microfilaments, eliminates it completely. Thus, various features of the action of cAMP derivatives on CHO and related cells require integrity of the cellular microfibrils-in some cases microtubules only, in some cases 5-nm microfilaments only and in some cases both classes of fibrils.