Phagocytosis in Metastatic Melanoma Cells: Is it a Part of Autophagy?

FakunleMary Fakunle
Advisor - Ralph Sorensen

Metastatic cancer cells, as opposed to primary cancer cells, have to ability to undergo autophagy, and phagocytosis as a means for survival. Due to the aggressive environment in which these cells live, metastatic cells have the ability to phagocyte both dead and live cells, to eliminate threatening immune responses, and for a source of nutrients. The processes, which both involve the degradation of materials, are initiated under conditions of nutrient deprivation. Autophagy involves the degradation of a cell’s own cytoplasmic organelle, and phagocytosis is the process of degrading extracellular particles. Both processes involve the fusion of an innate membrane bound vacuole with a lysosome, before the degradation can occur. The similarities between the processes and their recruitment by metastatic cancer cells suggest that the processes are related. B16-F10, mouse melanoma cells were exposed to three compounds to see how phagocytosis would be affected, compared to control cells. For each, Phagocytic Index (Percent of cells with beads x Total beads phagocyted) was measured and compared. 3-methyladenine (3-MA), a specific inhibitor of autophagy, was used in an assay at 20mM and 2mM concentrations. The results showed that phagocytosis was inhibited by both concentrations, but Phagocytic Index was significantly reduced by the 20mM concentration after 258 min, compared to the control (tcalc= 6.42, df= 2, P2t= 0.023). Rapamycin, a complex macrolide antibiotic, which works by inhibiting mammalian target of rapamycin (mTOR) enhances autophagy in various cells, and a 20µM concentration was used to induce phagocytosis in B16-F10 cells. The results showed that the compound did increase phagocytosis of the fluorescent beads, although the increase was not significant (tcalc= -2.98, df= 3, P2t= 0.058). A 10mM concentration of Azide, an inhibitor of oxidative phosphorylation, was used, and the results showed that there was a decrease in the phagocytic index of the cells exposed to Azide after 240 min (Phago Index = 1.12), compared to the control cells after 240min (Phago Index = 40.42). Statistical analysis was done using Paired t-Test.