Differential Antitumor Effects of IgG and IgM Monoclonal Antibodies and Their Synthetic Complementarity-Determining Regions Directed to New Targets of B16F10-Nex2 Melanoma Cells

Malignant melanoma has increased incidence worldwide and causes most skin cancer-related deaths. A few cell surface antigens that can be targets of antitumor immunotherapy have been characterized in melanoma. This is an expanding field because of the ineffectiveness of conventional cancer therapy for the metastatic form of melanoma. in the present work, antimelanoma monoclonal antibodies (mAbs) were raised against B16F10 cells (subclone Nex4, grown in murine serum), with novel specificities and antitumor effects in vitro and in vivo. MAb A4 (IgG2ak) recognizes a surface antigen on B16F10-Nex2 cells identified as protocadherin beta(13). It is cytotoxic in vitro and in vivo to B16F10-Nex2 cells as well as in vitro to human melanoma cell lines. MAb A4M (IgM) strongly reacted with nuclei of permeabilized murine tumor cells, recognizing histone 1. Although it is not cytotoxic in vitro, similarly with mAb A4, mAb A4M significantly reduced the number of lung nodules in mice challenged intravenously with B16F10-Nex2 cells. the V(H) CDR3 peptide from mAb A4 and V(L) CDR1 and CDR2 from mAb A4M showed significant cytotoxic activities in vitro, leading tumor cells to apoptosis. A cyclic peptide representing A4 CDR H3 competed with mAb A4 for binding to melanoma cells. MAb A4M CDRs L1 and L2 in addition to the antitumor effect also inhibited angiogenesis of human umbilical vein endothelial cells in vitro. As shown in the present work, mAbs A4 and A4M and selected CDR peptides are strong candidates to be developed as drugs for antitumor therapy for invasive melanoma.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Graduate School, University of Texas at El PasoNational Institutes of HealthUniv Texas MD Anderson Canc Ctr, Dept Canc Biol, Houston, TX 77030 USAUniversidade Federal de São Paulo, Expt Oncol Unit, Dept Microbiol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Div Parasitol, Dept Microbiol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biophys, BR-04023062 São Paulo, BrazilUniv São Paulo, Dept Pharmacol, Inst Biomed Sci, São Paulo, BrazilUniv Texas El Paso, Dept Biol Sci, Border Biomed Res Ctr, El Paso, TX 79968 USAUniv São Paulo, Immunol Invest Inst, Dept Immunol, Natl Inst Sci & Technol,Inst Biomed Sci, São Paulo, BrazilUniv São Paulo, Fac Med, Lab Med Invest, São Paulo, BrazilUniv Parma, Dept Pathol & Lab Med, Microbiol Sect, I-43100 Parma, ItalyUniversidade Federal de São Paulo, Expt Oncol Unit, Dept Microbiol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Div Parasitol, Dept Microbiol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biophys, BR-04023062 São Paulo, BrazilNational Institutes of Health: 5G12RR008124Web of Scienc