Shock Waves Enhance Expression of Glycosphingolipid Tumor Antigen on Renal Cell Carcinoma: Dynamics of Physically Unmasking Hidden Intracellular Markers Independent of Gene-Signaling Pathways

Abstract

Antigens associated with tumors have proven valuable in cancer immunotherapy. Their insufficient expression in the majority of tumors, however, limits their potential value as therapeutic markers. Aiming for a noninvasive approach applicable in clinical practice, we investigated the possibility of using focused shock waves to induce membrane expression of hidden intracellular tumor markers. Here, we studied the in vitro effect of a thousand focused shock waves at 16 MPa overpressure on the membrane expression of a cytosolic glycosphingolipid, monosialosyl-galactosyl-globoside (MSGG). Double-staining flow cytometry with propidium-iodide and monoclonal antibody RM1 revealed an immediate increase in MSGG expression on renal carcinoma cells (18% ± 0.5%) that reached its peak value (20.73% ± 0.4%) within one hour after the shock waves. The results of immunoelectron microscopy confirmed the incorporation of MSGG into newly formed cytosolic vesicles and their integration with the cell membrane. Based on the enzymatic nature of MSGG production that is not controlled directly by genes, the immediate upregulation of MSGG membrane expression implies that a chain of mechanochemical events affecting subcellular structures are responsible for the shock-wave-induced antigenic modification. Physically unmasking hidden tumor antigens and enhancing their expression by focused shock waves presents a potential noninvasive method of boosting tumor immunogenicity as a theranostic strategy in cancer immunotherapy.