Analysis of a murine anti-ganglioside GD2 monoclonal antibody expressing both IgG2a and IgG3 isotypes: monoclonality, apoptosis triggering, and activation of cellular cytotoxicity on human melanoma cells

Development of a dinutuximab delivery system using silk foams for GD2 targeted neuroblastoma cell death

Neuroblastoma is the most common extracranial solid tumor of childhood and is associated with poor survival in high risk patients. Recently, dinutuximab (DNX) has emerged as an effective immunotherapy to treat patients with high risk neuroblastoma. DNX works through the induction of cell lysis via complement-dependent cytotoxicity (CDC) or antibody dependent cellular cytotoxicity (ADCC). However, one third of patients who undergo DNX treatment exhibit tumor relapse and the therapy is dose limited by side effects such as severe pain. To overcome delivery challenges of DNX, including large size and dose limiting side effects, we fabricated a delivery system capable of sustained local delivery of bioactive DNX utilizing silk fibroin. We evaluated the impact of silk properties (MW, crystallinity, and concentration) on release properties and confirmed the bioactivity of the release product. Additionally, we observed that the effectiveness of CDC induction by DNX could be correlated to the GD2 expression level of the target cells, with both the intravenous DNX formulation and the released DNX. Collectively, these data highlights a strategy to overcome delivery challenges and potentially improve therapeutic efficacy in cells expressing heterogenous levels of GD2.

Anti-proliferative and pro-apoptotic activity of GD2 ganglioside-specific monoclonal antibody 3F8 in human melanoma cells

The beneficial clinical effects of immunotherapy with GD2-specific monoclonal antibodies (mAbs) in melanoma and neuroblastoma patients have stimulated interest in characterizing the mechanisms underlying their antitumor effects. Previous studies have shown that GD2-specific mAbs mediate complement- and cell-dependent cytotoxicity and induce caspase-dependent apoptosis of tumor cells. In this study, we showed that GD2-specific mAb 3F8, which is undergoing clinical evaluation, inhibited the in vitro growth and induced apoptosis of melanoma cells. This effect was dose- and time-dependent, mediated by the interaction of mAb 3F8 combining site with GD2 ganglioside, associated with GD2 expression level on the cell surface, mAb internalization and increase of GD2 containing endosomes triggered by mAb 3F8. The induction of apoptosis by mAb 3F8 was mediated by caspase 3-, 7-, and 8-dependent pathways, downregulation of the anti-apoptotic molecules survivin and cytochrome c, and caspase 9 independent-AIF release from mitochondria. In addition, analyses of signaling pathway components demonstrated that mAb 3F8 strongly inhibited AKT and FAK activation and increased cleaved PARP expression. These results indicated that multiple mechanisms played a role in the antitumor activity of mAb 3F8 in melanoma cells. This information should provide a mechanistic basis for the optimization of the rational design of immunotherapeutic strategies in the mAb-based treatment of GD2 positive tumors.

Reduction of spontaneous metastases through induction of carbohydrate cross-reactive apoptotic antibodies

The selective targeting of tumor-associated carbohydrate Ags by the induction of serum Abs that trigger apoptosis of tumor cells as a means to reduce circulating tumor cells and micrometastases would be an advantage in cancer vaccine development. Some plant lectins like Griffonia simplicifolia lectin I and wheat germ agglutinin mediate the apoptosis of tumor cells. We investigated the possibility of using these lectins as templates to select peptide mimotopes of tumor-associated carbohydrate Ags as immunogens to generate cross-reactive Abs capable of mediating apoptosis of tumor cells. In this study, we show that immunization with a mimotope selected based on its reactivity with Griffonia simplicifolia lectin I and wheat germ agglutinin induced serum IgM Abs in mice that mediated the apoptosis of murine 4T1 and human MCF7 cell lines in vitro, paralleling the apoptotic activity of the lectins. Vaccine-induced anti-carbohydrate Abs reduced the outgrowth of micrometastases in the 4T1 spontaneous tumor model, significantly increasing survival time of tumor-bearing animals. This finding parallels suggestions that carbohydrate-reactive IgM with apoptotic activity may have merit in the adjuvant setting if the right carbohydrate-associated targets are identified.