Besides the established fact of various protein/protein interactions of the members of the uPA system, the genes encoding them are likely regulated in a concerted manner in tumor growth and metastasis, for example, by the hypoxia-dependent transcription factor HIF1α as shown for uPAR und PAI-1 [31] and by CD44 as reported for uPA and uPAR [32]. Here, HIF1A is linked to neoplasm.