Glioblastoma multiforme (GBM) is an aggressive cancer characterized by extensive brain invasion. Matrix metalloproteinase (MMP)-9 plays a major role in this process. GBMs can be divided into two subtypes based on distinct clinical and molecular features. Primary GBMs arise de novo and frequently overexpress the epidermal growth factor receptor (EGFR) and its ligand-independent variant, EGFR variant III (EGFRvIII); secondary GBMs progress from a lower grade glioma and commonly harbor p53 mutations. Because EGFR signaling promotes MMP-9 expression and activation in other cancer cell types, we analyzed whether MMP-9 was associated with primary GBM subtype.Autopsies were performed on 20 GBM patients, and MMP expression was assessed by gelatin zymography in the tumor and the adjacent normal brain. EGFR, EGFRvIII, p53, and activated mitogen-activated protein kinase/extracellular signal-regulated kinase were assessed by immunohistochemistry, and associations between molecular phenotype and MMP-9 expression were analyzed.Latent MMP-9 was detected in 90% of tumors, and active MMP-9 was found in 50% of tumors. MMP-9 was not detected in any of the normal brain samples (P < 0.001). More importantly, primary GBMs were significantly more likely than secondary GBMs to contain active MMP-9 (69% of primary and 14% of secondary GBMs contained active MMP-9; P = 0.027). Active MMP-9 was observed in 73% of EGFR-overexpressing/wild-type p53-staining tumors but in only 20% of EGFR-negative/aberrant p53-staining tumors (P = 0.072). Active MMP-9 expression was even more strongly correlated with EGFRvIII expression, occurring in 83% of the EGFRvIII-immunopositive tumors but in none of the EGFRvIII-negative tumors (P = 0.0004). Extracellular signal-regulated kinase activation was also strongly correlated with EGFRvIII expression (P < 0.0001) and with MMP-9 activation (P = 0.003).These results identify a novel association between MMP-9 activation and primary GBM subtype and suggest that primary GBM patients, especially those whose tumors express EGFRvIII, may benefit from anti-MMP therapy.
Dendritic cells (DCs) are antigen-presenting cells that play a central role in the initiation and modulation of antitumor immune responses. In this pilot study, we investigated the ability of autologous DCs pulsed ex vivo with allogeneic major histocompatibility complex class I–matched glioblastoma peptides to stimulate host antitumor immune responses when injected as a vaccine. A patient with recurrent brainstem glioblastoma multiforme (GBM) received a series of three intradermal immunizations of antigen-pulsed DCs on an outpatient basis following surgical debulking of her posterior fossa tumor. Dendritic cell vaccination was well tolerated, and no clinical signs of autoimmunity or experimental allergic en-cephalomyelitis were detected. She developed a measurable cellular immune response against the allogeneic glioblastoma peptides used in her vaccine preparation, as demonstrated by in vitro T-cell proliferation assays. In addition, increased T-cell infiltration was noted within the intracranial tumor site in the biopsy sample obtained following DC vaccination. An objective clinical response, however, was not evident, and this patient eventually died 21 months after her disease was diagnosed. To our knowledge, this is the first patient with brain cancer ever to be treated with DC-based immunotherapy. This case illustrates that vaccination with DCs pulsed with acid-eluted glioblastoma peptides is feasible and can induce systemic antigen-specific immunity in a patient with recurrent GBM. Additional studies are necessary to determine the optimum DC doses and antigen loading conditions that may translate into clinical effectiveness and survival benefit for patients with brain tumors. Phase I trials for malignant glioma are currently underway.
