Impaired SNX9 Expression in Immune Cells during Chronic Inflammation: Prognostic and Diagnostic Implications

Abstract

Chronic inflammation is associated with immunosuppression and downregulated expression of the TCR CD247. In searching for new biomarkers that could validate the impaired host immune status under chronic inflammatory conditions, we discovered that sorting nexin 9 (SNX9), a protein that participates in early stages of clathrin-mediated endocytosis, is downregulated as well under such conditions. SNX9 expression was affected earlier than CD247 by the generated harmful environment, suggesting that it is a potential marker sensing the generated immunosuppressive condition. We found that myeloid-derived suppressor cells, which are elevated in the course of chronic inflammation, are responsible for the observed SNX9 reduced expression. Moreover, SNX9 downregulation is reversible, as its expression levels return to normal and immune functions are restored when the inflammatory response and/or myeloid-derived suppressor cells are neutralized. SNX9 downregulation was detected in numerous mouse models for pathologies characterized by chronic inflammation such as chronic infection (Leishmania donovani), cancer (melanoma and colorectal carcinoma), and an autoimmune disease (rheumatoid arthritis). Interestingly, reduced levels of SNX9 were also observed in blood samples from colorectal cancer patients, emphasizing the feasibility of its use as a diagnostic and prognostic biomarker sensing the host’s immune status and inflammatory stage. Our new discovery of SNX9 as being regulated by chronic inflammation and its association with immunosuppression, in addition to the CD247 regulation under such conditions, show the global impact of chronic inflammation and the generated immune environment on different cellular pathways in a diverse spectrum of diseases.

Endocytosis, Metastasis and Beyond: Multiple Facets of SNX9

“…Not surprisingly, SNX9 is linked to many human diseases, including Lowe syndrome [61], chronic inflammation [62,63], and cancer [20,52]. Interestingly, these links relate mostly to alterations in its expression levels rather than point mutations that impair its function.…”

Quantitative Flow Cytometry: Concerns and Recommendations in Clinic and Research

“…These beads are particles labeled with a mixture of fluorochromes at different fluorescent intensity levels (23). In addition, rainbow beads allow setting a fixed output value (target MFI) for each fluorescent channel (3,33,34). In addition, rainbow beads allow setting a fixed output value (target MFI) for each fluorescent channel (3,33,34).…”

“…Moreover, following initial set-up, the FC must be routinely monitored, as it has a great impact on the validity of the results. Even when the system is calibrated, FC output tend to vary due to differences in the cytometers' configuration and adjustment (33).…”

“…The beads can be used for a variety of FC calibrations; starting with quality control for FC performance and laser stability, as previously recommended by EuroFlow and ICSH/ICCS (1,3,29,30). In addition, rainbow beads allow setting a fixed output value (target MFI) for each fluorescent channel (3,33,34). The target MFI is set prior to each experiment, ensuring that the reading is done in the correct and standardized settings that are more accurate than using the same PMT settings through different experiments.…”

“…In addition, specialized micro particles with capture antibodies that bind antibodies in a homogenous mode combined with low auto-fluorescence values are commercially available. These in turn, can be used as calibrators for each fluorescent channel enabling proper adjustment of compensation in more controlled and homogenous system (33).…”