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Glioblastoma multiforme (GBM) is the most common form of primary brain cancer and carries a dreadful five-year survival rate of 9%. Current treatment options include surgery, chemotherapy, and radiation. Recently, there has been a move to pursue immunotherapy options to improve patient outcomes. These therapies often depend on the identification of molecular markers that are distinctive to the tumor cells. Some markers, such as HER2/Neu and EGFR, are overexpressed on a significant percentage of GBM tumors and are used as targets for immunotherapies. However, to address GBM tumors that do not overexpress HER2/Neu and EGFR, our lab set out to identify novel markers on GBM as future candidates for Natural Killer (NK) cell-mediated immunotherapy. Previously, our lab demonstrated that Lectin-like Transcript-1 (LLT1), membrane-bound Proliferating Cell Nuclear Antigen (PCNA), NKp44 Ligand (NKp44L) and CS1 (CD319) are targets of NK cell-mediated killing of various cancers. Based on these prior studies, we examined their expression on the well-known GBM cell lines LN-229 and LN-18 by flow cytometry using PE-labeled antibodies specific for each marker. PCNA was the lone marker identified to be highly expressed on both LN-229 and LN-18 cells. Based on our results, we concluded that cell surface PCNA is an ideal candidate for NK cell-mediated immunotherapy for GBM. Currently, we are evaluating blocking inhibitory signals to NK cells from the PCNA-NKp44 interaction to target GBM for NK-mediated killing. Recent findings demonstrating the ability to transiently open the blood-brain barrier further increase the feasibility of targeting GBM by NK cells in the future. Supported by funding from the Osteopathic Scholars in Cancer Research Program grant from the Cancer Prevention and Research Institute of Texas (RP170301) and UNTHSC Intramural grants.