Glioblastoma Cells Respond Directionally to L1CAM Protein Ectodomain
Authors: Stubbolo Alexander Ian , Plusch Kyle , Bernheimer Camryn , Galileo Deni S. 
Published: June 2021

Glioblastoma Multiforme (GBM) is the most common form of brain cancer and is also the most malignant. Part of what makes this cancer so insidious is the invariable tendency for tumors to regrow and kill patients after tumor removal. Currently, there is no definitive treatment for such cases, nor is there a consensus on the cause. It is our hypothesis that a major reason is the expression and release of L1CAM (L1), a neural cell adhesion protein, by GBM cells. Previously, our lab has used Super Scratch assays to show that L1 increases motility and proliferation in glioblastoma cells. However, until now, there has not been research into a possible attractive chemotactic effect of L1 on glioblastoma cells to guide their motility. In this study, we investigated the possibility of the released L1 ectodomain (L1ecto) guiding glioblastoma cells up a concentration gradient of L1ecto released by neighboring cells, and the ability of patterned immobilized L1ecto to stimulate GBM cell motility. This was done in vitro by modifying existing scratch assay protocols to examine not only the velocity of GBM cells, but also the preferential direction of their movement toward other GBM cells either releasing, or not releasing, L1ecto. The results of these experiments showed a significant chemotactic effect of released L1ecto. Responding cells moved significantly faster and directionally toward cells releasing L1ecto compared to their motility toward cells not releasing L1ecto. This suggests cells were responding to a gradient of L1ecto originating from the L1ecto releasing cells. These experiments suggest a possible leader‐follower relationship between L1 releasing and responding GBM cells during brain tumor invasion into surrounding tissue. To test this, we also studied a possible chemotactic relationship in vivo by injecting a mixture of fluorescently labelled red L1 positive and green L1 negative glioblastoma cells into the optic tectum of chick embryos. The embryos developed for ten days, after which the brain was dissected, sectioned with a vibratome, and then optically sectioned using a confocal microscope. 3D models then were rendered to examine the invasion pathways of the cancerous cells. Results thus far suggest a strong “leader‐follower” relationship between L1ecto releasing cells and non‐L1 producing cells. We conclude that 1) released L1ecto can form a soluble gradient that can be detected by GBM cells and guide their direction and stimulate their velocity; 2) immobilized L1ecto also can stimulate and guide GBM cell motility in vitro; and 3) GBM cells releasing L1ecto in brain appear to be able to influence other GBM cells to follow them.Support or Funding InformationWe thank the University of Delaware's Summer Scholars Program, Undergraduate Research Program, Dept. of Biological Sciences Undergraduate Research Fund, ASBMB, and graduate student Reetika Dutt.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.