The hypoxia-sensor carbonic anhydrase IX affects macrophage metabolism, but is not a suitable biomarker for human cardiovascular disease.

Hypoxia is prevalent in atherosclerotic plaques, promoting plaque aggravation and subsequent cardiovascular disease (CVD). Transmembrane protein carbonic anhydrase IX (CAIX) is hypoxia-induced and can be shed into the circulation as soluble CAIX (sCAIX). As plaque macrophages are hypoxic, we hypothesized a role for CAIX in macrophage function, and as biomarker of hypoxic plaque burden and CVD. As tumor patients with probable CVD are treated with CAIX inhibitors, this study will shed light on their safety profile. CAIX co-localized with macrophages (CD68) and hypoxia (pimonidazole), and correlated with lipid core size and pro-inflammatory iNOS+ macrophages in unstable human carotid artery plaques. Although elevated pH and reduced lactate levels in culture medium of CAIX knock-out (CAIXko) macrophages confirmed its role as pH-regulator, only spare respiratory capacity of CAIXko macrophages was reduced. Proliferation, apoptosis, lipid uptake and expression of pro- and anti-inflammatory genes were not altered. Plasma sCAIX levels and plaque-resident CAIX were below the detection threshold in 50 and 90% of asymptomatic and symptomatic cases, respectively, while detectable levels did not associate with primary or secondary events, or intraplaque hemorrhage. Initial findings show that CAIX deficiency interferes with macrophage metabolism. Despite a correlation with inflammatory macrophages, plaque-resident and sCAIX expression levels are too low to serve as biomarkers of future CVD.

High serum carbonic anhydrase IX predicts shorter survival in head and neck cancer.

OBJECTIVES: The objective of the study was to investigate prognostic and predictive value of pretreatment soluble carbonic anhydrase IX (CA IX) blood serum concentration in patients with locally advanced head and neck cancer. BACKGROUND: Increased expression of CA IX in tumor tissues has been associated with treatment resistance and worth prognosis. Soluble form of CA IX, released from tumor cells, is detectable in blood serum and could be a convenient predictive factor of treatment effectiveness that would enable treatment individualization. METHODS: The prospective study evaluated 48 patients with locally advanced squamous cell carcinomas of head and neck, treated by radiotherapy or chemo-radiotherapy. Pretreatment soluble CA IX serum concentrations were examined using enzyme-linked immunosorbent assay. RESULTS: Soluble CA IX serum concentration failed to predict radiotherapy effectiveness in the studied patient population (p = 0.26). However, high CA IX serum concentrations have been associated with shorter overall survival (p = 0.035) CONCLUSION: High pretreatment CA IX serum concentration is a negative prognostic factor in locally advanced head and neck cancer patients (Tab. 1, Fig. 2, Ref. 23).

Carbonic anhydrase IX as an anticancer therapy target: preclinical evaluation of internalizing monoclonal antibody directed to catalytic domain.

Carbonic anhydrase IX (CA IX) is a suitable target for various anticancer strategies. It is a cell surface protein that is present in human tumors, but not in the corresponding normal tissues. Expression of CA IX is induced by hypoxia and correlates with cancer prognosis in many tumor types. Moreover, CA IX is functionally implicated in cancer progression as a pro-survival factor protecting cancer cells against hypoxia and acidosis via its capability to regulate pH and cell adhesion. Cancer-related distribution of CA IX allows for targeting cancer cells by antibodies binding to its extracellular domain, whereas functional involvement of CA IX opens the possibility to hit cancer cells by blocking their adaptation to physiologic stresses via inhibition of CA IX enzyme activity. The latter strategy is recently receiving considerable attention and great efforts are made to produce CA IX-selective inhibitor derivatives with anticancer effects. On the other hand, targeting CA IX-expressing cells by immunotherapy has reached clinical trials and is close to application in treatment of renal cell carcinoma patients. Nevertheless, development and characterization of new CA IX-specific antibodies is still ongoing. Here we describe a mouse monoclonal antibody VII/20 directed to catalytic domain of CA IX. We show that upon binding to CA IX, the VII/20 MAb undergoes efficient receptor-mediated internalization, which is a process regulating abundance and signaling of cell surface proteins and has considerable impact on immunotherapy. We evaluated biological properties of the MAb and demonstrated its capacity to elicit anti-cancer effect in mouse xenograft model of colorectal carcinoma. Thus, the VII/20 MAb might serve as a tool for preclinical studies of immunotherapeutic strategies against non-RCC tumors. These have not been explored so far and include broad spectrum of cancer types, treatment of which might benefit from CA IX-mediated targeting.