Carbonic anhydrase 9 confers resistance to ferroptosis/apoptosis in malignant mesothelioma under hypoxia

Abstract

Hypoxia and acidity provide microenvironment for selection under evolutionary pressure and proliferation in cancer cells. Carbonic anhydrases (CAs) are a superfamily of metalloenzymes present in all life kingdoms, equilibrating the reactions among CO2, bicarbonate and H+. CA9, a membrane-associated α-CA, has been a drug target for various cancers. Whereas iron is essential not only for cancer cells but also for all the lives on earth, little is known on the association among hypoxia, iron metabolism, extracellular acidity and redox regulation. Malignant mesothelioma (MM), an aggressive tumor with poor prognosis, is an intriguing model in that asbestos-associated pathogenesis includes excess iron environment during carcinogenesis. Re-analysis of rat asbestos-induced MM model revealed an inverse association between high CA9 expression and survival. Here we used human MMs to identify the molecular events surrounding CA9 from the viewpoint of iron metabolism. CA9 expression was significantly higher in MM cells than in MeT-5A mesothelial cells, which was further amplified under hypoxia (1%O2) with increased catalytic Fe(II). CA9 suppression by inhibitors (S4 and U104) decreased viability and migration of MM cells, accompanied by overexpression of TFRC, IREB1/2 and FPN1(SLC40A1) and by downregulation of FTH/FTL. This expressional pattern was similar to that of erastin-induced ferroptosis in the same cells. Furthermore, we observed mitochondrial fission and enhanced autophagy with increased catalytic Fe(II) in both mitochondria and lysosomes after CA9 inhibition, accompanied by increased peroxides, mitochondrial O2− and lipid peroxidation. The eventual cell death was significantly inhibited by deferoxamine, ferrostatin-1 and Z-VAD-FMK, suggesting a mixed cell death of ferroptosis and apoptosis. Therefore, CA9 plays a role in equilibrating among hypoxia, iron metabolism and redox regulation in MM cells.

Ferroptosis at the crossroads of infection, aging and cancer

“…miRNA is also associated with ferroptosis 79 . We recently found that carbonic anhydrase 9 confers ferroptosis resistance to mesothelioma cells 80 . Ferroptosis is a fundamental process for understanding carcinogenesis and tumor biology because all living creatures on Earth depend heavily on iron to survive.…”

<p>Ferroptosis in Carcinoma: Regulatory Mechanisms and New Method for Cancer Therapy</p>

“…CA9, a membrane-associated α-CA (carbonic anhydrase), is upregulated in the formation of malignant mesothelioma. Inhibition of CA9 induced the ferroptosis and apoptosis of cancer cells by increasing catalytic Fe 2+ in lysosomes and mitochondria and lipid peroxidation 35. However, the regulatory hub and network connecting ferroptosis and apoptosis are still unknown.…”

Preclinical Evaluation of Ureidosulfamate Carbonic Anhydrase IX/XII Inhibitors in the Treatment of Cancers

“…In particular, therapies to target the treatment-resistant populations associated with hypoxic niches are much sought after. Some CAIX/XII-selective compounds based on the sulfamate or benzenesulfonamide scaffold inhibit proliferation and increase apoptosis of different cancer cells in normoxic conditions [18,45] or more prominent under hypoxic conditions [15,17,32,46]. The increased apoptosis is associated with a reduced expression of CAIX, suggesting that apoptosis is induced in high CAIX expressing cells.…”