Tamoxifen Upregulates Collagenase Gene Expression in Human Dermal Fibroblasts

Tamoxifen is a known inhibitor of fibroblast transforming growth factor beta biosynthesis and wound scar formation. Tamoxifen is also known to be an estrogen antagonist and protein kinase C (PKC) inhibitor. Cells treated with tamoxifen and other PKC/calmodulin inhibitors depolymerize their membrane focal adhesion complexes and cytoskeletal protein structures. These effects result in substrate detachment, cell shape rounding, and upregulation of collagenase synthesis and extracellular matrix degradation. The purpose of our study was to test the hypothesis that tamoxifen treatment of human foreskin fibroblasts results in alteration of cytoskeletal protein organization, cell detachment and rounding, and increased collagenase synthesis similar to known PKC/calmodulin inhibitors such as H-7.

We characterized the effects of PKC/calmodulin inhibitors tamoxifen and H-7 on human dermal fibroblast morphology, cytoskeletal protein organization, and collagenase gene expression in monolayer culture and within collagen gels.

We found that fibroblasts responded to tamoxifen by initiation of actin filament depolymerization followed by alteration from spindle to spheroidal shapes. This change in cell shape led to increased collagenase synthesis in cells treated with either tamoxifen or H-7 compared with controls. There was also a 23% increase of hydroxyproline release from tamoxifen-treated fibroblast-populated collagen matrices.

Tamoxifen may reduce scarring by inhibiting fibroblast PKC/calmodulin activity, which down-regulates pro-fibrotic transforming growth factor beta signaling and upregulates collagenase production. These effects mimic those of the known PKC/calmodulin inhibitor H-7. Overall, these findings suggest that tamoxifen and its analogues are promising agents for clinical investigation as small molecule regulators of fibrosis and scarring disorders.