The aggressive , poorly differentiated PtC group was specifically characterized by marked upregulation of several genes related to cell proliferation such as cell division cycle 2 ( CDC 2 ) , CDC 7 , kinesin like 5 , ubiquitin conjugating enzyme E2C , and topoisomerase IIalpha , and by upregulation of genes encoding extracellular matrix proteins such as seprase , extracellular matrix protein 1 , and several collagens . ^^^