Epidermal growth factor receptor (EGFR) and its ligands (EGF and TGFalpha) are over-expressed in a variety of tumors. Immunization EGF-carrier protein inhibits tumor growth through abrogating binding of EGF to EGFR. Here, a chimeric protein of EGF and TGFalpha (E5T) was genetically fused to Staphylococcal enterotoxin A (SEA), a bacterial superantigenic protein which promotes humoral B cell response through enhancement of Ag-specific CD4 T cells activity. The resulted fusion proteins were expressed in Escherichia coli and purified though metal chelating affinity chromatography. Immunization of E5T-mSEA fusion protein in mice induced production of high titers antibodies, which recognize both EGF and TGFalpha. Anti- E5T-mSEA serum at dilution of 1:10 significantly inhibited growth of A431 cell lines but had little effect on 293T cell lines.
Amino Acid Sequence ; Animals ; Cancer Vaccines ; biosynthesis ; immunology ; Cell Line, Tumor ; Enterotoxins ; biosynthesis ; genetics ; Epidermal Growth Factor ; biosynthesis ; genetics ; Escherichia coli ; genetics ; metabolism ; Humans ; Immunization ; Mice ; Mice, Inbred C57BL ; Molecular Sequence Data ; Random Allocation ; Receptor, Epidermal Growth Factor ; antagonists & inhibitors ; immunology ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology ; Transforming Growth Factor alpha ; biosynthesis ; genetics

Objective:To evaluate the antitumor activity of recombinant SEA for therapy of B16 melanoma established in C57BL/6 mice. Methods:C57BL/6 mice with melanoma were treated with the purified rSEA. The tumors were isolated and weighted. Results:Tumor growth was apparently inhibited by rSEA at high, middle, and low doses intraperitone-ally, whose inhibition ratio were 79.3% , 75.6 % and 73. 8% respectively. rSEA treatment in situ could inhibit tumor growth more effectively(90.6% ). Further study showed that numerous CD8+ and CD4+ T cell were infiltrated in tumor tissues, which were consistent with tumor growth inhibition induced by rSEA. Conclusions: rSEA could inhibit tumor growth effectively, especially the treatment in situ. This study paves the way for tumor immunotherapy with targeted SEA.