Down-regulation of collagen XII in transformed mesenchymal cells

Collagen XII is a complex multidomain protein associated with the surface of interstitial collagen fibrils. This protein is produced in large amounts by fibroblasts cultivated in vitro. However, it is completely absent from cells transformed by the oncogene v-myc or v-src and from cells derived from a methylcholanthrene-induced fibrosarcoma. Since all these cells lack any mRNA for collagen, XII, it seems likely that the synthesis is blocked at the transcriptional level. Experiments with a temperature-sensitive mutant of Rous sarcoma virus demonstrated that a single oncogene product is sufficient to inhibit the synthesis. A reduction in the expression of collagen XII might have profound effects on the stability of the extracellular matrix of transformed cells.