Targeting carbonic anhydrase IX depletes breast cancer stem cells within the hypoxic niche

Abstract

The sub-population of tumor cells termed 'cancer stem cells' (CSCs) possess the capability to generate tumors, undergo epithelialmesenchymal transition (EMT) and are implicated in metastasis, making treatments to specifically target CSCs an attractive therapeutic strategy. Tumor hypoxia plays a key role in regulating EMT and cancer stem cell function. Carbonic anhydrase IX (CAIX) is a hypoxia-inducible protein that regulates cellular pH to promote cancer cell survival and invasion in hypoxic microenvironments and is a biomarker of poor prognosis for breast cancer metastasis and survival. Here, we demonstrate that inhibition of CAIX expression or activity with novel small-molecule inhibitors in breast cancer cell lines, or in primary metastatic breast cancer cells, results in the inhibition of breast CSC expansion in hypoxia. We identify the mTORC1 axis as a critical pathway downstream of CAIX in the regulation of cancer stem cell function. CAIX is also required for expression of EMT markers and regulators, as well as drivers of 'stemness', such as Notch1 and Jagged1 in isolated CSCs. In addition, treatment of mice bearing orthotopic breast tumors with CAIX-specific small-molecule inhibitors results in significant depletion of CSCs within these tumors. Furthermore, combination treatment with paclitaxel results in enhanced tumor growth delay and eradication of lung metastases. These data demonstrate that CAIX is a critical mediator of the expansion of breast CSCs in hypoxic niches by sustaining the mesenchymal and 'stemness' phenotypes of these cells, making CAIX an important therapeutic target for selectively depleting breast CSCs.

Reprogramming during epithelial to mesenchymal transition under the control of TGFβ

“…Treatment of mice with a CAIX inhibitor, suppressed CSCs and combination therapy with paclitaxel and the CAIX inhibitor potently blocked metastasis in these mice. 143 The concept that EMT links to cancer stemness could potentially offer novel possibilities for improved prognostics and therapeutic intervention for human breast cancer. A recent study addressing the phenotype of circulating tumor cells in the blood of breast cancer patients revealed a diverse cohort of cells exhibiting both epithelial and mesenchymal features.…”

“…142 The hypoxia-inducible protein carbonic anhydrase IX (CAIX) contributes to changes in local pH induced by hypoxia. 143 CAIX can promote breast CSC proliferation by activation of mTORC1 signaling leading to EMT and high expression of Jagged1 and Notch1. Treatment of mice with a CAIX inhibitor, suppressed CSCs and combination therapy with paclitaxel and the CAIX inhibitor potently blocked metastasis in these mice.…”

Trimeric Radiofluorinated Sulfonamide Derivatives to Achieve In Vivo Selectivity for Carbonic Anhydrase IX–Targeted PET Imaging

“…The latter process facilitates cell migration and invasion and potentiates metastatic activity in primary lesions (8,9). Recently, CA-IX has been shown to mediate growth and expansion of breast cancer stem cells within hypoxic niches (10). Clinically, the expression of CA-IX is negatively correlated with patient prognosis and survival (11).…”

Carbonic anhydrase IX correlates with survival and is a potential therapeutic target for neuroblastoma

“…breast cancer 13 , prostate cancer 14 , gastric cancer 15 , oral squamous cell cancer 16 , leads to an increased malignancy with an increased metastatic rate and treatment resistance with a poor prognosis. In breast cancer, CAIX is vital for growth and metastasis of hypoxic tumors, and has been shown to be a specific and targetable biomarker for metastasis 13,17 . In neuroblastoma, CAIX has previously been shown to be up-regulated in patients with adverse clinicopathological and biological factors, e.g.…”