Carbonic Anhydrase IX Promotes Myeloid-Derived Suppressor Cell Mobilization and Establishment of a Metastatic Niche by Stimulating G-CSF Production

Abstract

The mobilization of bone marrow-derived cells (BMDC) to distant tissues before the arrival of disseminated tumor cells has been shown preclinically to facilitate metastasis through the establishment of metastatic niches. Primary tumor hypoxia has been demonstrated to play a pivotal role in the production of chemokines and cytokines responsible for the mobilization of these BMDCs, especially in breast cancer. Carbonic anhydrase IX (CAIX, CA9) expression is highly upregulated in hypoxic breast cancer cells through the action of hypoxia-inducible factor-1 (HIF1). Preclinical evidence has demonstrated that CAIX is required for breast tumor growth and metastasis; however, the mechanism by which CAIX exerts its prometastatic function is not well understood. Here, we show that CAIX is indispensable for the production of granulocyte colony-stimulating factor (G-CSF) by hypoxic breast cancer cells and tumors in an orthotopic model. Furthermore, we demonstrate that tumor-expressed CAIX is required for the G-CSF-driven mobilization of granulocytic myeloid-derived suppressor cells (MDSC) to the breast cancer lung metastatic niche. We also determined that CAIX expression is required for the activation of NF-kB in hypoxic breast cancer cells and constitutive activation of the NF-kB pathway in CAIX-depleted cells restored G-CSF secretion. Together, these findings identify a novel hypoxia-induced CAIX-NF-kB-G-CSF cellular signaling axis culminating in the mobilization of granulocytic MDSCs to the breast cancer lung metastatic niche. Cancer Res; 75(6); 996-1008.Ó2015 AACR.

Cancer Tills the Premetastatic Field: Mechanistic Basis and Clinical Implications

“…For hepatocellular carcinomas, hypoxia and TGF-β induce LOXL2 in the primary tumor and in patient sera, thereby increasing tissue stiffness and promoting cancer cell adhesion and metastasis (61). As an indirect mechanism, hypoxia-induced expression of carbonic anhydrase IX in breast cancer cells leads to the secretion of G-CSF, which mobilizes granulocytic MDSCs to pre-metastatic lungs and promotes metastasis (62). The effects of other types of stresses in the primary tumors, such as nutrient deprivation, on the establishment of a pre-metastatic niche are yet to be identified.…”

“…A thorough list of these factors and their effects on pre-metastatic niche has been summarized (8). More recent work has shown that factors secreted by hypoxic tumor cells, including LOX, LOXL2, and G-CSF, direct a pro-metastatic niche reprogramming (60–62). LOXL2 has also been shown to collaborate with E47 to induce EMT and increase the secretion of GM-CSF to recruit BMDCs to pre-metastatic lungs (26).…”

Cross‐Talk Between Hypoxia and the Tumour via Exosomes

“…The bicarbonate goes back into the cell through bicarbonate transporters and balances the intracellular pH as alkaline, which is favourable for the cell's survival. The protons acidify the extracellular space, thus facilitating the tumour's migratory and invasive behaviour [45][46][47]. CAIX expression and activity also facilitates the production of Granulocytecolony stimulating factor (G-CSF),which is in turn required for the transportation of granulocytic Myeloid-derived Suppressor Cells (MDSC) to the metastatic niche-an environment that promotes metastasis.…”

“…CAIX expression is also required to stimulate NF-κB activity and G-CSF production mediated through hypoxia. The hypoxia-mediated NF-κB activity is triggered by a decrease in the pH level of the culture as well as hypoxia-induced glycolytic activity in the cancer cells [46,[48][49][50]. The hypoxic areas of tumours usually have lower levels of extracellular pH due to increased metabolic activity [45].…”

The changing paradigm of tumour response to irradiation

“…7 Potential roles of such cells may include enhancing vascular recovery as well as modulating immune reactivity or possibly enhancing metastasis. 8,9 High levels of neutrophils in the circulation and the tumour have also been associated with poor treatment outcome in cancers following irradiation. [10][11][12] In this article, I will review some of the old literature concerning tumour response to radiation treatment and relate this to current concepts about the role of the microenvironment in tumour response to radiation treatment.…”