Novel C-type lectins profile as immunosuppression players and potential biomarkers in cancer patients

Lectins are immunoregulatory receptors that in cancer sustain immunosuppressive mechanisms. So far, little is known about lectins and their role in glioblastoma (GBM) immunosuppression circuits. Here, we aimed to identify the lectins profile relevant in GBM and investigate their potential as immune biomarkers. Differential co-expression analysis was performed on RNA-seq data on three datasets (TCGA, CGGA, GTEx). Patients’ clusters were identified with Fuzzy C-means algorithm based on hub lectins and survival analysis was performed. Network-analysis consistently identified in both datasets a novel C-type lectins cluster in GBM (ASGR2, CLEC12A, CLEC7A and CLEC4A) and Siglec7, Siglec9 and galectin9 already described in GBM immunosuppression and poor prognosis. The combined expression of the two strongest hub lectins, ASGR2 and CLEC12A, was able to discriminate two patients’ groups and those with high lectins expression levels displayed the worse prognosis (p=0.03). The lectins clinical relevance was further increased when combined with high levels of Siglec7, Siglec9, galectin9 (p=0.02), suggesting that lectin co-expression might be relevant in the immunosuppression circuits in GBM. We then validated the novel identified C-type lectins in GBM patients by Flow-Cytometry (FC) (16 GBM patients matched-tumor and liquid biopsies). Our results showed that all four C-type lectins were heterogeneously expressed by tumor infiltrating myeloid cells. ASGR2 and CLEC7A were restricted to tumor infiltrating myeloid cells and undetectable in peripheral blood displaying a specific distribution pattern: ASGR2 was higher on infiltrating macrophages (MDM) vs microglia (MG), while CLEC7A was higher on MG vs infiltrating myeloid-derived suppressor cells (MDSC) (p<0.05). CLEC4A and CLEC12A had a broad distribution in both infiltrating and circulating myeloid cells, particularly those of monocytic origin. Interestingly, this pattern of C-type lectins expression in circulating myeloid subsets (CLEC12A+ and CLEC4A+, while ASGR2- and CLEC7A-) was also validated on PBMCs of oncologic patients (44) with different tumor histotypes (Breast cancer, HNSCC, NSCLC). We are currently validating CLEC12A and CLEC4A as prognostic biomarkers. In conclusion, we identified a lectins profile relevant for GBM patient prognosis, that suggests an intricate network of interactions between distinct lectins and cells and we characterized for the first time the expression of C-type lectins on infiltrating and circulating myeloid cells in GBM and in cancer patients. ASGR2 expression may be induced in a pathological tissue and may contribute to macrophages-mediated immunosuppression. CLEC4A and CLEC12A may be exploited as potential circulating biomarkers in oncologic patients.