BSBM-13 MELANOMA CELLS PRODUCE A SUSPENSION SUB-POPULATION THAT DRASTICALLY DISRUPTS THE BLOOD-BRAIN BARRIER ENDOTHELIUM

Melanoma metastasizes to the brain with high propensity. Brain metastasis requires cancer cells to breach the blood-brain barrier (BBB) endothelium, which forms the first line of defence against blood-borne pathogens. An increasing number of molecules are discussed in BBB disruption, and their importance varies across melanoma and endothelial cell lines. This diversity in literature proposes that cancer cells of the same cancer type employ different modes of metastasis. This study shows an example of the difference in migration capabilities of adherent melanoma cells and a suspension sub-population. We used Electric Cell-substrate Impedance Sensing (ECIS) to assess changes in human brain endothelial barrier function upon adding human melanoma lines. Several melanoma lines induced brain endothelial barrier disruption within the first few hours of addition. Intriguingly, the suspension population of melanoma cells disrupted the endothelial barrier faster and more drastically than the adherent counterpart. Time-lapse imaging revealed that the suspension population used a transcellular route of invasion compared to the paracellular route used by the adherent cells. Confocal microscopy supported this, showing clear differences in the physical interaction of the suspension subtype with the brain endothelium, compared to the adherent cells. Flow cytometry and NanoString technology allowed characterization of the melanoma lines, showing that the suspension subtype protein composition differs from their adherent counterpart. We hypothesize that melanoma cells may produce specific subtypes that are more invasive, which can accelerate migration through the brain endothelium. We stress the importance of investigating the composition of melanoma cells and their bi-products when researching cancer metastasis. Once successfully within the brain parenchyma, these cancer cells are effectively separated from the peripheral adaptive immune system, designed to detect and eliminate them. Therefore, preventing cancer cell migration into the brain is an attractive consideration, as they are considerably more targetable whilst still in the blood.