PSMB5 and pterygium: In order to examine whether the same applies to pterygium fibroblasts, cells were irradiated with UVB after pre-incubation with src kinase inhibitor PP2 [51], at radiation doses 0–50 mJ/cm2, and the expression of PSMB5 and Nrf2 at the mRNA level was examined using RT-PCR (Fig. 7).