Excess hepsin proteolytic activity limits oncogenic signaling and induces ER stress and autophagy in prostate cancer cells

Abstract

The serine protease hepsin is frequently overexpressed in human prostate cancer (PCa) and is associated with matrix degradation and PCa progression in mice. Curiously, low expression of hepsin is associated with poor survival in different cancer types, and transgenic overexpression of hepsin leads to loss of viability in various cancer cell lines. Here, by comparing isogenic transfectants of the PCa cell line PC-3 providing inducible overexpression of wild-type hepsin (HPN) vs. the protease-deficient mutant HPN S353A , we were able to attribute hepsin-mediated tumor-adverse effects to its excess proteolytic activity. A stem-like expression signature of surface markers and adhesion molecules, Notch intracellular domain release, and increased pericellular protease activity were associated with low expression levels of wild-type hepsin, but were partially lost in response to overexpression. Instead, overexpression of wild-type hepsin, but not of HPN S353A , induced relocalization of the protein to the cytoplasm, and increased autophagic flux in vitro as well as LC3B punctae frequency in tumor xenografts. Confocal microscopy revealed colocalization of wild-type hepsin with both LC3B punctae as well as with the autophagy cargo receptor p62/SQSTM1. Overexpression of wild type, but not protease-deficient hepsin induced expression and nuclear presence of CHOP, indicating activation of the unfolded protein response and ER-associated protein degradation (ERAD). Whereas inhibitors of ER stress and secretory protein trafficking slightly increased viability, combined inhibition of the ubiquitin-proteasome degradation pathway (by bortezomib) with either ER stress (by salubrinal) or autophagy (by bafilomycin A1) revealed a significant decrease of viability during overexpression of wild-type hepsin in PC-3 cells. Our results demonstrate that a precise control of Hepsin proteolytic activity is critical for PCa cell fate and suggest, that the interference with ERAD could be a promising therapeutic option, leading to induction of proteotoxicity in hepsin-overexpressing tumors.

L1CAM, CA9, KLK6, HPN, and ALDH1A1 as Potential Serum Markers in Primary and Metastatic Colorectal Cancer Screening

“…Nonetheless, the generated data displayed the involvement of HPN in the metastatic progression of CRC. One of the plausible explanations was that overexpression of HPN was associated with matrix degradation (invasion and metastasis initiator), similar to that of prostate cancer [ 86 ]. Another assumption was that HPN was strongly associated with pathogenesis and early carcinogenesis of CRC, since it caused disorganization of the basement membrane and promoted primary prostate cancer progression and metastasis to liver, lung, and bone [ 87 ].…”

<p>Hepsin Promotes Epithelial–Mesenchymal Transition and Cell Invasion Through the miR-222/PPP2R2A/AKT Axis in Prostate Cancer</p>

“… 41 Willbold et al demonstrated that the proteolytic activity of hepsin is related to ER stress and autophagy in prostate cancer cells. 8 An inhibitor of hepsin was reported to block prostate cancer bone metastasis. 9 Here, we show that hepsin is overexpressed in prostate cancer and that hepsin knockdown inhibits cell invasion and EMT in prostate cancer.…”

“… 4 Hepsin is frequently overexpressed in PC 5 , 6 and correlated positively with aggressiveness. 7 The functions of hepsin in malignant biological behaviors, including autophagy, 8 bone metastasis 9 and tumor growth, 10 of PC have been well studied. Hepsin is also involved in the diagnosis and prognosis of PC.…”

Hepsin: a multifunctional transmembrane serine protease in pathobiology

“…To date, a number of hepsin-mediated mechanisms have been proposed in cancer. These include pro-HGF and promacrophage stimulating protein activation to enhance Met and RON signaling, respectively [42,54,56,118]; activation of metalloproteinases to promote matrix protein degradation [119,120]; activation of other cell surface proteases, which in turn enhance receptor-mediated signaling [39,121]; depletion of HAI-1 that blocks the cancer-promoting activity of other cell surface proteases [56,122,123]; direct cleavage of matrix proteins and cell surface receptors [62,124,125]; induction of ER stress and the unfolded protein response [126]; and deregulation of cell cycle and apoptotic signaling [127]. More detailed discussions regarding hepsin and associated mechanisms in cancer are covered in recent comprehensive reviews [34,37,38].…”