To this end, in two mutated PA proteins, PA-L1(named also PrAg-L1) and PA-L2, the natural furin recognition site was replaced by sequences susceptible to cleavage by MMP-2 (gelatinase A) and MMP-9 (gelatinase B) that are reported to be related to invasion and metastasis in various human cancers [473,474,475,476]. Here, MMP2 is linked to cancer.