Panoply™ Human L1CAM Knockdown Stable Cell Line

Here, researchers investigated the role of the neuronal cell adhesion molecule L1 cell adhesion molecule (L1CAM) in retinoblastoma (RB), the most common childhood intraocular malignancy. L1CAM is differentially expressed in multiple human cancers and is considered a promising therapeutic target. They observed differential expression patterns of L1CAM in RB cell lines and patient samples. Two proteases involved in L1CAM ectodomain shedding (ADAM10 and ADAM17) were also differentially expressed in the RB cell lines studied and confirmed their involvement in L1CAM processing in RB cells. The researchers also identified ezrin, galectin-3, and fibroblast growth factor basic as target genes of L1CAM signaling in RB cells. Lentiviral knockdown of L1CAM induced apoptosis in RB cells and reduced cell viability, proliferation, growth, and colony formation, while L1CAM-overexpressing RB cells exhibited the opposite effects. Chicken chorioallantoic membrane assays demonstrated that L1CAM depletion reduced the tumorigenicity and migratory potential of RB cells in vivo. Furthermore, L1CAM depletion reduced viability and tumor growth in etoposide-resistant RB cell lines after etoposide treatment in vitro and in vivo. Therefore, L1CAM and its processing sheddase are potential new targets for future RB therapeutics.

To investigate whether L1CAM affects tumor growth in RB cells, the researchers used a CAM assay as an in vivo model. L1CAM-knockdown RB355 and WERI-Rb1 cells, as well as control cells, were inoculated into the CAM of 10-day-old chick embryos. Imaging of CAM tumors formed by inoculated RB cells and quantification of tumor weight and size revealed that tumors formed by L1CAM-knockdown RB cells were significantly smaller than those formed by control cells (Figure 1A, C), with reduced tumor weight and size (Figure 1B, C). The number of developing tumors did not change significantly. Following injection of GFP-labeled RB355 and WERI-Rb1 cells into the CAM vein, L1CAM-knockdown RB cells extravasated from the CAM vessels (Figure 1D). However, real-time PCR analysis of human GAPDH in lower CAM punches revealed that their migration rate was significantly lower than that of the corresponding control cells (Figure 1E, F). These results indicate that loss of L1CAM expression leads to reduced tumorigenicity and migration potential in vivo.

Figure 1. Effects of stable, lentiviral L1CAM knockdown on tumor formation and tumor cell migration of RB cells in vivo. (Dräger O, et al., 2022)