183P - CAIX negatively modulates inflammatory and anti-tumor immune responses

Background

In cancer, inflammation frequently coexists with hypoxia within the tumor microenvironment (TME), often creating an immunosuppressive environment. This hostile milieu is further exacerbated by acidosis, which collectively further hinders effective anti-tumor immune responses. Carbonic anhydrase IX (CAIX) is a well-established hypoxia marker that plays a key role in the pH regulation and adaptation of tumor cells to hypoxia resulting in tumor progression. The CAIX activity contributes to the formation of an acidic environment, which can suppress the function of cytotoxic T cells and other immune cells. While primarily induced by HIF1α under hypoxic conditions, CAIX expression can also be triggered in an inflammatory milieu by IL6 or the COX-2/PGE2 pathway. The goal of this study is to determine the role of CAIX in the regulation of inflammatory and anti-tumor immune responses.

Methods

CAIX+ and CAIX-silenced HT1080 cells were cultured in the presence of a conditioned (inflammatory) medium obtained from MUF spheroids (MUF-CM) under normoxic or hypoxic conditions. RNA samples were analyzed by Clariom, followed by unsupervised clustering. Gene Set Expression Analysis (GSEA) was used to analyze the gene expression. The relation between CAIX level and gene sets identified by GSEA was also analyzed in TCGA SARComa samples and pancreatic cancer (PC).

Results

We found that MUF-CM can upregulate CAIX expression in fibrosarcoma and PC cells even under normoxia. Our analysis revealed that suppression of CAIX leads to upregulation of hallmarks of IFN-α, IFN-γ, and inflammatory response. In silico analysis of TCGA SARC samples confirmed the relationship between lower CAIX expression and higher expression of IFN-α, IFN-γ and inflammation response gene sets, which predicted better overall survival. Moreover, the immune gene sets associated with immune activation and expression of HLA-antigens negatively correlated with CAIX.

Conclusions

Understanding the complex interplay between hypoxia, CAIX, and inflammation is crucial for developing effective cancer treatments. Given the central role of CAIX in this intricate relationship, targeting the function of this enzyme may represent a new opportunity to create a favorable milieu for anti-tumor immune response in the TME.

Legal entity responsible for the study

The authors.

Funding

The Slovak Research and Development Agency 20-0480.

Disclosure

All authors have declared no conflicts of interest.