 Fibroblasts – a type of cell that synthesizes the extracellular matrix and collagen and is involved in wound healing – that have been transformed by the polyomavirus possess higher tyrosine activity in the cellular matrix.Furthermore, tyrosine kinase activity has been determined to be correlated to cellular transformation.It has also been demonstrated that phosphorylation of a middle-T antigen on tyrosine is also associated with cell transformation, a change that is similar to cellular growth or reproduction.