FGF5 and neoplasm: Importantly, for the fibroblast growth factor (FGF)-5 and several splicetopes derived from the tumor differentiation antigen gp100mel, in vitro proteasome splicing reactions were also found to mimic the in vivo splicing reactions (Ebstein et al., 2016; Warren et al., 2006), suggesting that in vitro PCPS reactions may be a useful tool to discover new spliced epitopes generated from tumor antigens of interest.