Saporin induces multiple death pathways in lymphoma cells with different intensity and timing as compared to ricin.

Abstract

Ribosome-inactivating protein (RIP)-containing immunotoxins are currently used in clinical trials as anti-tumour drugs, in particular against haematological malignancies. In cell killing-based therapies it is important to identify the death pathways induced by the cytotoxic agent. The purpose of this work was to compare the pathways of cell death induced by the RIP saporin with those carried out by ricin in the L540 human Hodgkin's lymphoma-derived cell line. Protein synthesis inhibition, activation of caspases, DNA fragmentation and loss of viability have been evaluated. The two toxins triggered a similar DNA fragmentation and cell death, at concentrations giving the same level of cell protein synthesis inhibition, although the inhibitory effect of ricin on protein synthesis was more rapid than that of saporin. Moreover, the intrinsic apoptotic pathway was equally activated by both toxins, whilst ricin activated the extrinsic caspase pathway and the effector caspase-3/7 more efficiently than saporin. The complete inhibition of caspases by Z-VAD was only partially effective in cell rescue which appeared to be time limited. Necrostatin-1, a new inhibitor of non-apoptotic death, rescued cells from death by RIPs, although the effect was also partial and temporary. Despite the high RIP doses used no necrosis was detectable by Annexin V/Propidium Iodide (PI) test. These results suggest that more than one death mechanism was elicited by both ricin and saporin, however, with different timing and strength. The perspective of modulating cell death of neoplastic lymphocytes through different pathways could add new opportunities to reduce side effects and develop combined synergic immuno-chemotherapy.

• Authors: Letizia Polito, Massimo Bortolotti, Valentina Farini, Maria Giulia Battelli, Luigi Barbieri, Andrea Bolognesi
• Journal: The international journal of biochemistry & cell biology (Int J Biochem Cell Biol) Vol. 41 Issue 5 Pg. 1055-61 (May 2009) ISSN: 1878-5875 [Electronic] Netherlands
• PMID: 18935973 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents, Phytogenic
• Caspase Inhibitors
• Ribosome Inactivating Proteins, Type 1
• Ricin
• Saporins
• Caspases

Topics

• Antineoplastic Agents, Phytogenic (pharmacology)
• Apoptosis (drug effects)
• Caspase Inhibitors
• Caspases (metabolism)
• Cell Death (drug effects)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Dose-Response Relationship, Drug
• Enzyme Activation (drug effects)
• Hodgkin Disease (drug therapy, pathology)
• Humans
• In Situ Nick-End Labeling
• Ribosome Inactivating Proteins, Type 1 (pharmacology)
• Ricin (pharmacology)
• Saporins