As with DPP4, FAP, APN, and ADAM17, increased expression of MMP2/9 in TME is often associated with the development and progression of cancer [33,34,35], and both MMPs have the ability to cleave many different targets (extracellular matrix, cytokines, growth factors, chemokines, and cytokine/growth factor receptors) that in turn modulate key signalling pathways involved in cell growth, migration, invasion, and angiogenesis [33,36,37] (Figure 1). The gene discussed is DPP4; the disease is cancer.