Collagen synthesis by short-term explants of pediatric tumors

Collagens are a heterogeneous family of structural proteins synthesized by many cultured cells including tumor cells. The synthesis of these proteins by three human tumor types commonly encountered in children [neuroblastoma, rhabdomyosarcoma, and nephroblastoma (Wilms' tumor)] was investigated in short-term cultures of freshly excised tumor explants grown on extracellular matrices. Analysis of the incorporation of [3H]proline into collagenase-sensitive proteins indicated significant collagen production by several Wilms' tumors and rhabdomyosarcomas, while neuroblastomas did not synthesize this structural protein. All eight Wilms' tumor specimens analyzed secreted type IV procollagen. Interstitial types I and III collagens were also produced by these tumors, but in most cases, the alpha 1 (I): alpha 2 ratio was much higher than the 2:1 ratio expected for type I collagen, indicating a major change in the control of type I collagen production. Rhabdomyosarcomas were very heterogeneous with regard to collagen secretion and synthesized either a single collagen isotype (type III), several collagens including types I, III, and IV, or no detectable collagen. Our data represent a first quantitative and qualitative analysis of collagen synthesis by primary tumor cultures and reveal much more heterogeneity in collagen biosynthesis by these tumors than reported previously with established cell lines. They also indicate significant alterations in the expression of type I collagen genes in Wilms' tumors.