Cell-Surface PCNA Is Co-Expressed with Biomarkers of Stemness and Immunosuppression in Glioblastoma

Background/Objectives: Glioblastoma (GBM) is a lethal form of primary brain tumor. There has been minimal improvement in overall GBM survival in recent years. To increase survival in patients with GBM, it is important to study novel GBM molecular antigens to form the basis of better diagnostics, prognostic measures, and therapeutic advancements. Our goal is to find more robust GBM-specific antigenic biomarkers to eventually improve GBM outcomes. Here, we initiated an investigation into cell-surface PCNA (csPCNA), a potential GBM biomarker and antigenic target. Methods: We utilized flow cytometry, imaging flow cytometry, and cell-surface Western blot to identify the expression of csPCNA on GBM cell lines (LN-229, LN-18) and a primary patient-derived tumor specimen. We then employed flow cytometry to study the associative co-expression of csPCNA with other biomarkers of GBM stem cells (CD44, CD49f) and GBM immunosuppression (PD-L1, TGFβRII). Results: We elucidated that LN-229, LN-18, and the primary GBM patient cells express csPCNA. We found that csPCNA is co-expressed with CD44, CD49f, PD-L1, and TGFβRII on the primary patient-derived GBM specimen. Conclusions: Our findings that csPCNA is expressed in GBM and is co-expressed with stem cell and immunosuppressive biomarkers indicate that csPCNA may be a potentially useful clinical–pathological biomarker for GBM stemness and immunosuppression.