Ectodomain shedding of the hypoxia-induced carbonic anhydrase IX is a metalloprotease-dependent process regulated by TACE/ADAM17

Abstract

Carbonic anhydrase IX (CA IX) is a transmembrane protein whose expression is strongly induced by hypoxia in a broad spectrum of human tumours. It is a highly active enzyme functionally involved in both pH control and cell adhesion. Its presence in tumours usually indicates poor prognosis. Ectodomain of CA IX is detectable in the culture medium and body fluids of cancer patients, but the mechanism of its shedding has not been thoroughly investigated. Here, we analysed several cell lines with natural and ectopic expression of CA IX to show that its ectodomain release is sensitive to metalloprotease inhibitor batimastat (BB-94) and that hypoxia maintains the normal rate of basal shedding, thus leading to concomitant increase in cell-associated and extracellular CA IX levels. Using CHO-M2 cells defective in shedding, we demonstrated that the basal CA IX ectodomain release does not require a functional TNFa-converting enzyme (TACE/ADAM17), whereas the activation of CA IX shedding by both phorbol-12-myristate-13-acetate and pervanadate is TACE-dependent. Our results suggest that the cleavage of CA IX ectodomain is a regulated process that responds to physiological factors and signal transduction stimuli and may therefore contribute to adaptive changes in the protein composition of tumour cells and their microenvironment.

High levels of carbonic anhydrase IX in tumour tissue and plasma are biomarkers of poor prognostic in patients with non-small cell lung cancer

“…Although our observations were inconsistent with the proposal that hypoxia and HIF-1 are the sole regulators of CAIX expression and thus shedding (Zatovicova et al, 2005), one cannot exclude that shedding occurs at hypoxic metastatic sites. Although the precise molecular mechanism of regulated CAIX shedding remains to be clarified, previous studies showed that dysregulation of HIF-1a could be caused by mutation in the von Hippel-Lindau (VHL) tumour suppressor gene or activation of the epidermal growth factor receptor (EGFR) (Semenza, 2003).…”

Angiogenesis- and Hypoxia-Associated Proteins as Early Indicators of the Outcome in Patients with Metastatic Breast Cancer Given First-Line Bevacizumab-Based Therapy

“…CA9 expression in tumor and stromal tissue can be considered as a marker of hypoxia (14). Ectodomain shedding of CA9 mainly occurs by hypoxic cancer cells and leads to an increase in circulating levels (39). Therefore, the use of circulating CA9 may provide a noninvasive means of assessing tumor hypoxia.…”

Carbonic anhydrase IX (CA9) modulates tumor-associated cell migration and invasion

“…At least 13 human CA isoenzymes that exhibit catalytic activity are distributed in various human organs, tissues and subcellular compartments, playing an important role in essential cellular processes such as pHe and pHi regulation, secretion of electrolytes, respiration and biosynthetic reactions that require CO 2 and HCO 3 -as substrates (e.g. lipogenesis, gluconeogenesis and ureagenesis) (Thiry et al, 2006;Zatovicova et al, 2005). CA9, the only transmembrane CA isoenzyme with an extracellular active site and an NH 2 -terminal proteoglycan-like region, is also implicated in cell adhesion as well as in acid-base balancing and intercellular communication (Robertson et al, 2004;Svastova et al, 2003).…”