The main objective of this project is to determine the mechanism of the recruitment and production of MDSC’s (myeloid-derived suppressor cells) in 4T1 breast cancer cells. Scientists to this day still do not what are producing these MDSC’s in humans. MDSC’s help cancer cells by debilitating the immune system. A protein that could possibly stop the MDSC recruitment is CXCR4, which is a chemokine receptor. MDSC’s have an important role in the immune responses in cancer. In this investigation, we set out to determine whether CXCR4 was present in 4T1 cancer cells and if it plays a role in recruitment of MDSC’s. In order to see if CXCR4 had a presence in the 4T1 cancer cells, a western blot, a flow cytometer, and a cell sorter were used.