Two Saporin-Containing Immunotoxins Specific for CD20 and CD22 Show Different Behavior in Killing Lymphoma Cells

• Published in: Toxins Vol. 9; no. 6; p. 182
• Main Authors: Polito, Letizia, Mercatelli, Daniele, Bortolotti, Massimo, Maiello, Stefania, Djemil, Alice, Battelli, Maria, Bolognesi, Andrea
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 30.05.2017; MDPI AG
• Subjects: Antigens, CD20 - immunology; Antineoplastic Agents - chemistry; Antineoplastic Agents - immunology; Apoptosis - drug effects; B-lymphoma; Catalase - pharmacology; CD20; CD22; Cell Line; Cell Survival - drug effects; Humans; immunotherapy; immunotoxin; Immunotoxins - chemistry; Immunotoxins - pharmacology; Jurkat Cells; Lymphoma - drug therapy; Ribosome Inactivating Proteins, Type 1 - chemistry; Ribosome Inactivating Proteins, Type 1 - pharmacology; ribosome-inactivating proteins; saporin-S6; Sialic Acid Binding Ig-like Lectin 2 - immunology; CD20; saporin-S6; B-lymphoma; immunotherapy; immunotoxin; ribosome-inactivating proteins; CD22
• ISSN: 2072-6651; 2072-6651
• DOI: 10.3390/toxins9060182

Immunotoxins (ITs) are hybrid proteins combining the binding specificity of antibodies with the cytocidal properties of toxins. They represent a promising approach to lymphoma therapy. The cytotoxicity of two immunotoxins obtained by chemical conjugation of the plant toxin saporin-S6 with the anti-CD20 chimeric antibody rituximab and the anti-CD22 murine antibody OM124 were evaluated on the CD20-/CD22-positive cell line Raji. Both ITs showed strong cytotoxicity for Raji cells, but the anti-CD22 IT was two logs more efficient in killing, probably because of its faster internalization. The anti-CD22 IT gave slower but greater caspase activation than the anti-CD20 IT. The cytotoxic effect of both immunotoxins can be partially prevented by either the pan-caspase inhibitor Z-VAD or the necroptosis inhibitor necrostatin-1. Oxidative stress seems to be involved in the cell killing activity of anti-CD20 IT, as demonstrated by the protective role of the H2O2 scavenger catalase, but not in that of anti-CD22 IT. Moreover, the IT toxicity can be augmented by the contemporary administration of other chemotherapeutic drugs, such as PS-341, MG-132, and fludarabine. These results contribute to the understanding of the immunotoxin mechanism of action that is required for their clinical use, either alone or in combination with other drugs.