Detection of N-glycolyl GM3 ganglioside in neuroectodermal tumors by immunohistochemistry: an attractive vaccine target for aggressive pediatric cancer

Abstract

The N-glycolylated ganglioside NeuGc-GM3 has been described in solid tumors such as breast carcinoma, nonsmall cell lung cancer, and melanoma, but is usually not detected in normal human cells. Our aim was to evaluate the presence of NeuGc-GM3 in pediatric neuroectodermal tumors by immunohistochemistry. Twenty-seven archival cases of neuroblastoma and Ewing sarcoma family of tumors (ESFT) were analyzed. Formalin-fixed, paraffin-embedded tumor samples were cut into 5 μm sections. The monoclonal antibody 14F7, a mouse IgG1 that specifically recognizes NeuGc-GM3, and a peroxidase-labeled polymer conjugated to secondary antibodies were used. Presence of NeuGc-GM3 was evident in 23 of 27 cases (85%), with an average of about 70% of positive tumors cells. Immunoreactivity was moderate to intense in most tumors, showing a diffuse cytoplasmic and membranous staining, although cases of ESFT demonstrated a fine granular cytoplasmic pattern. No significant differences were observed between neuroblastoma with and without NMYC oncogene amplification, suggesting that expression of NeuGc-GM3 is preserved in more aggressive cancers. Until now, the expression of N-glycolylated gangliosides in pediatric neuroectodermal tumors has not been investigated. The present study evidenced the expression of NeuGc-GM3 in a high proportion of neuroectodermal tumors, suggesting its potential utility as a specific target of immunotherapy.

Figure 1

Immunohistochemical detection of NeuGc-GM3 ganglioside in neuroectodermal tumors. (a) Neuroblastoma (NMYC-amplified). (b) Ewing sarcoma family of tumors (ESFT). (c) Negative isotype control staining (mouse IgG1) in neuroblastoma. (d) No expression in nontumoral neural tissue. Original magnification 400X (a, b and c), 100X (d), 1,000X (insets).

Figure 2

Expression of NeuGc-GM3 ganglioside and Ki-67 protein in NMYC-amplified and -nonamplified neuroblastoma. NeuGc-GM3 (open bars) was assessed with the immunoreactive score (IRS) and the percent of Ki-67 positive cells (closed bars) was used as a proliferation index. Data represent mean ± SEM. *P < 0.02 (t test)