Inhibition of PACE4, a proprotein convertase that is overexpressed in prostate cancer, has been shown to block cancer progression in an androgen-independent manner. However, the basis for its overexpression and its growth-inhibitory effects are mitigated and uncertain.

Here, we report that PACE4 pre-mRNA undergoes DNA methylation–sensitive alternative splicing of its terminal exon 3′ untranslated region, generating an oncogenic, C-terminally modified isoform (PACE4-altCT).

We found this isoform to be strongly expressed in prostate cancer cells, where it displayed an enhanced autoactivating process and a distinct intracellular routing that prevented its extracellular secretion.

Together, these events led to a dramatic increase in processing of the progrowth differentiation factor pro-GDF15 as the first PACE4 substrate to be identified in prostate cancer. We detected robust expression of PACE4-altCT in other cancer types, suggesting that an oncogenic switch for this proenzyme may offer a therapeutic target not only in advanced prostate cancer but perhaps also more broadly in human cancer.

 

Source: Cancer Research (AACR Journal)