The same trend was also observed for arginylproline with significantly higher amounts in PXE cells (Figure 5c; patient/control ratio:1.5, p<0.0002) and lower levels in ABCC6-silenced cells (Figure 5c; siNK/siABCC6 ratio:0.7, p<0.0009). The gene discussed is ABCC6; the disease is pseudoxanthoma elasticum (inherited or acquired).