cAMP effect on extracellular matrix synthesis in human breast cancer cells

The effect of a cAMP derivative (N6, O2-dibutyryl cyclic adenosine 3',5'-monophosphate: dBcAMP) on the cell cycle and on the synthesis of typical extracellular matrix (ECM) components, i.e. collagen and glycosaminoglycans (GAG), was studied in two hormone-responsive human breast cancer cell lines VHB-1 and MCF-7. The data showed that dBcAMP induced a decrease in the proportion of cells in S + G2 + M phases due to an increase of the non-cycling (G0 phase) cell number as revealed by the Ki-67 antigen immunocytochemical study. The collagen synthesis, estimated by [3H] proline incorporation into the cellular proteins followed by an enzymatic digestion with highly purified bacterial collagenase, was not modified by dBcAMP. In contrast, the GAG synthesis, analysed by [3H] glucosamine incorporation, was increased two-fold in the dBcAMP treated cells. As a comparison we also tested 4-hydroxy-Tamoxifen (4-OH-Tam) since it induces similar cell cycle perturbations as dBcAMP. However, we did not observe a stimulation of the GAG synthesis following 4-OH-Tam treatment. These data demonstrated that the increased GAG synthesis is due to cAMP and is not a consequence of perturbations in the cell cycle. We can therefore assume that the ECM modifications induced by dBcAMP may contribute to the growth inhibition of the hormone-responsive human breast cancer cells.