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Determining How Calcium Affects Exosome Secretion in A549 Cells

Exosomes have been identified as possible markers for early detection and a promising research avenue for intervention in diseases like cancer. They are considered a possible way that cancer spreads throughout the body. The exploration into the effects of Ca2+ (Calcium) on exosome secretion in A549 cells could give some insight into the overall traits of exosomes, how they are possibly used in the spread of diseases like cancer and if exosome secretion can be manipulated. This experiment aimed to discover what Ca2+ levels affect exosome secretion and if an increase in exosome secretion is proportional to the increase in concentration. I hypothesized that increased amounts of Ca2+, above typical cytosolic levels, would increase the amount of fusion events and therefore the overall amount of exosomes in the sample.

In order to test the hypothesis, A549 cells were transfected with a fluorescent tag and introduced to various levels of calcium in a microscope plate. Using total internal reflection (TIRF) microscopy, the tagged CD63 protein was monitored, which is involved in fusion, and several videos of each cell were acquired to record the total fusion events in each sample. In my experiment, fusion increased but not significantly. The test images would only have about one, occasionally two, more fusion events than the control images treated with just Ca2+. Therefore, the experiment model may need to be changed to increase fusion. One possible change could be the amount of ionomycin used or the way it is introduced into the solution with the Ca2+.