Human-Specific Elimination of Epithelial Siglec-XII Suppresses the Risk of CRC Initiation and Progression [ENDPOINT]
Human-specific changes in specific Siglecs is one of the reasons put forth as molecular mechanisms that could explain human proneness to developing cancers. The SIGLEC12 gene, which encodes the Siglec-XII protein mainly found on epithelial cells, has a fixed homozygous missense mutation in a critical arginine renders unable to recognize its natural ligand. Additionally, the gene harbors a polymorphic frameshift mutation that eliminates expression of the full-length protein in most humans. We hypothesized that dysfunctional Siglec-XII is involved in cancer progression in humans' epithelia. Here we report that the transgenic conditional expression of human Siglec-XII in mouse intestinal epithelia increased the number and size of cancers in a model of colitis-associated colorectal carcinoma (AOM/DSS). RNA sequencing of the colons at baseline and after AOM/DSS challenge derived a gene signature comprised of the differentially expressed genes (DEGs) between controls (Villin1-Cre-ER(T2)) and Siglec-XII-expressing mice, showing that upregulated DEGs in Siglec-XII mice were enriched for diverse bioenergetic processes. Overall design: To investigate the impact of the expression of human SIGLEC12 in the development of mouse colon tumors, we developed a knock-in mouse model that allows the conditional expression of human SIGLEC12 only in the villi and crypts of the small and large intestine (SIGLEC12-Villin1-Cre-ERT). SIGLEC12 knock-in (SIGLEC12-Villin1-Cre-ERT) and control (Villin-Cre-RT) mice received 5 days treatment (10 mg/ml) with tamoxifen, to induce SIGLEC12 expression, followed by an intraperitoneal injection (10 mg/kg body weight) of azoxymethane (AOM) followed by 5 days of dextran sodium sulfate salt (DSS) treatment (2.0%) and 14 days of recovery. This cycle was repeated three times. After the fourth DSS cycle (87 days), mice were sacrificed, and colon tumors were harvested. We then performed gene expression profiling analysis using data obtained from RNA-seq of three mice for each condition.