Acute myeloid leukemia (AML) is characterized by uncontrolled proliferation of abnormal immature bone marrow progenitor cells (“blasts”). AML blasts reside in the bone marrow microenvironment via adhesion molecules such as CXCR-4 and VLA-4, which confer protection from chemotherapy in AML. L-selectin is a surface receptor utilized by leukocytes (white blood cells) for rolling on the endothelial lining of blood vessels and adhesion to sites of inflammation. CXCR-4 is a chemokine receptor for stromal derived factor (SDF-1, CXCL12) produced by bone marrow stromal cells. VLA4 is an α4β1 integrin that mediates adhesion to alternatively spliced fibronectin and cellular vascular cell adhesion molecule 1 (VCAM1). Previous studies in our laboratory and others suggested that expression of CXCR-4 and VLA-4 is associated with prognosis in AML, and L-selectin expression increases with older age in AML patients. The hypothesis of my project is that L-selectin expression level is associated with chemotherapy resistance in AML. We performed experiments on blasts with high vs. low L-selectin surface expression as measured by flow cytometry assessment of mean fluorescence intensity (MFI). We allowed the AML blasts to be attached to plates coated with PSGL-1, an L-selectin ligand, or bovine serum albumin (BSA), a control protein. Then blasts were treated with cytarabine (Ara-C), one of the most active chemotherapy drugs in AML, for 72 hours. Data were collected by manual counting of viable cells, Cell-Titer Glo luminescent viability assay, and flow cytometry for Annexin V, as a measure of apoptosis. Our data showed that PSGL-1 binding protected AML blasts from chemotherapy in 4/15 (27%) of the samples, which had higher L-selectin (p = 0.05), lower VLA-4 expression (p = 0.10) and higher CXCR-4 (p=0.11) surface expression. Therefore, these results suggest that differences in expression and function of L-selectin, CXCR-4 and VLA-4 are associated with chemotherapy sensitivity in AML blasts.