Development of a polyclonal antibody with defined specificity against synthetic peptides from the N-myc oncoprotein using multiple antigen peptide and hemocyanin conjugation methods

Abstract

Background/Purpose: The importance of determining N-myc oncoprotein rather than genomic N- myc amplification has been emphasized in neuroblastoma, especially in an international project to register biological risk factors in all neuroblastomas. A method to raise a specific polyclonal antibody against the N-myc oncoprotein in large quantities was sought using the synthetic antigen peptide and the multiple antigen peptide (MAP) method. Methods: Two sets of peptides, HGRGPPTAGSTAQSPG and GVAPPRPGGROTSGGDH, conserved in the N-myc oncoprotein were synthesized. The hemocyanin-conjugated peptides and the lysine core-conjugated (multiple antigen peptide method) peptides were injected into rabbits with adjuvant. IgG fractions precipitated from the sera were purified on an affinity column coupled with these peptides, and the potency and specificity of the purified IgGs were examined by immunoblotting and immunohistochemistry in small cell lung cancer cell lines with known positivity-negativity of amplification and expression of N- myc, c- myc, and L- myc. Results: Peptides conjugated to the lysine core raised more potent antibodies than those conjugated to hemocyanin. Purified IgG against GVAPPRPGGRQTSGGDH reacted positively with an N- myc-amplified lung cancer cell line, but not with N- myc-unamplified and c- myc/L- myc-amplified cell lines on either immunoblotting or immunostaining. This IgG strongly stained the nuclei of cells in a series of surgical specimens and cell lines of neuroblastoma with N- myc amplification. Conclusion: A polyclonal antibody specific for a synthetic peptide from the N-myc oncoprotein was thus obtained and will find wide international use.