Introduction: Complement plays an important role in the immune response to pathogens and inflammation, and necrosis (a poor prognostic indicator in medulloblastomas) is a well-known initiator of the cascade. We investigated the role of C3 activated by necrosis in proliferation of medulloblastoma cells.
Methods: Immunohistochemistry (IHC) using iC3b antibody and H&E staining on adjacent sections of medulloblastoma specimens was performed. Western blot (WB) was performed on multiple cell lines for C3a receptor (C3aR) to demonstrate expression of this receptor protein. Knockdown assays using siRNA for C3aR were performed and growth curves were attained. WBs were performed on these assays to demonstrate knockdown of C3aR.
Results: IHC and H&E stains on adjacent sections displayed activated complement corresponding to necrotic areas. C3aR was demonstrated on WB of the Daoy, D283, and D341 cell lines, signifying that the protein is displayed on the cell surface. Proliferation assays of Daoy cells with knockdown siRNA vs. control siRNA revealed statistically significant reduction in proliferation of 35.7% at 72 hours (p=.001). WB of these cell populations showed a mean of 55% knockdown of C3aR.
Conclusions: Medulloblastoma cells express C3aR and respond to necrosis-induced activation of C3a by proliferating. siRNA-mediated knockdown of C3aR inhibits proliferation of these cells. C3aR may be a promising therapeutic target for medulloblastoma treatment.
Patient Care: The identification of complement cascade molecules in the proliferation of meulloblastoma cells may have significant prognostic and therapeutic ramifications. Further research is warranted to better characterize the role of C3 in medulloblastoma.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) describe the relationship between complement activation in tumor necrosis and the proliferation of medulloblastoma cells, and 2) discuss, in small groups, the possibilities of the “double-edged sword” in using various management modalities which may cause necrosis in these tumors, and therefore, contribute to the proliferation in vivo, that we have demonstrated in vitro.