Apoptosis-inducing therapeuticals promote ectodomain shedding of hypoxia-regulated carbonic anhydrase IX


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Michal Pastorek1,Ivana Vidlickova2,Miriam Zatovicova2,Silvia Pastorekova2
1Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Brno, Czech Republic,2Department of Molecular Medicine, Institute of Virology, Biomedical Research Center, Slovak Academy of Sciences, Dubravska cesta 9, 845 05, Bratislava, Slovak Republic



Carbonic anhydrase IX (CA IX) is a hypoxia-regulated transmembrane protein, implicated in cell adhesion, EMT, and tumour invasiveness, and is therefore strongly associated with cancer progression. It was previously found that shedding and release of CA IX ectodomain (ECD) into plasma of cancer patients can signify prognosis and is considered a marker for therapy success. In this work, we have investigated shedding of CA IX ECD in tumour cells undergoing apoptosis in response to cycloheximide and doxorubicin treatment.


Using flow cytometry and cell sorting, we have correlated the extent of apoptosis with the presence of cell surface CA IX in CGL3 cell line characterized by both positive and negative CA IX subpopulations, and then determined level of shed ECD by ELISA.


We have observed lower percentage of apoptotic cells in CA IX positive subpopulation after cycloheximide treatment. However, CA IX level of cycloheximide and doxorubicin-treated cells decreased during apoptotic death, suggesting an increased ECD shedding, that was not averted by inhibitors of apoptosis but decreased after metalloproteinase inhibition.


These findings supported the view that prevention of CA IX ECD shedding may contribute to better cancer cell survival.