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Updated: Jun 24, 2026
Experimental Melanoma Immunotherapy Model Using Tumor Vaccination with a Hematopoietic Cytokine
Published on: February 24, 2023
The melanoma specific 9.2.27PE immunotoxin efficiently kills melanoma cells in vitro
Karianne Risberg1, Øystein Fodstad, Yvonne Andersson
1Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Rikshospitalet University Hospital, Oslo, Norway.
Abstract:
Malignant melanomas are generally drug resistant and have a very poor prognosis. We have studied the effects of a chemical conjugate of pseudomonas exotoxin A (PE) and the antibody 9.2.27, which recognizes the high molecular weight melanoma associated antigen (HMW-MAA) expressed in most malignant melanomas and melanoma cell lines. We demonstrate that the 9.2.27PE immunotoxin (IT) induces cell death in malignant melanoma cells through protein synthesis inhibition followed by some morphological and biochemical features of apoptosis, like rounding up of cells, chromatin condensation and inactivation of PARP. Unlike previous results with the 425.3PE IT in breast cancer cells, we detected no depolarization of the mitochondrial membrane after 9.2.27PE IT treatment. This is likely due to the lack of strong activation of caspase-8 and caspase-3. The lack of depolarization suggests that cytochrome c, a molecule that triggers activation of caspase-3, was retained within the mitochondria. In addition, the protein level of the antiapoptotic Bcl-2 did not decrease in contrast to other antiapoptotic molecules belonging to the inhibitor of apoptosis and the Bcl-2 family. This suggests that Bcl-2 may play a role in maintaining the mitochondrial membrane integrity in the 9.2.27PE-treated cells. Nevertheless, 9.2.27PE IT efficiently killed malignant melanoma cells that can be ascribed to inhibition of protein synthesis followed by some morphological and biochemical features of apoptosis.
Insights
This study shows that the 9.2.27PE immunotoxin effectively kills drug-resistant malignant melanoma cells by inhibiting protein synthesis and inducing apoptosis. The immunotoxin targets the high molecular weight melanoma-associated antigen (HMW-MAA).
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Malignant melanomas are characterized by drug resistance and poor prognosis.
- Targeted therapies are crucial for improving outcomes in melanoma treatment.
Purpose of the Study:
- To investigate the efficacy and mechanism of action of the 9.2.27PE immunotoxin against malignant melanoma cells.
- To evaluate the role of apoptosis and mitochondrial pathways in the immunotoxin's cell-killing activity.
Main Methods:
- Conjugation of Pseudomonas exotoxin A (PE) with the 9.2.27 antibody targeting HMW-MAA.
- Treatment of malignant melanoma cells with the 9.2.27PE immunotoxin (IT).
- Assessment of cell death, protein synthesis inhibition, apoptosis markers (PARP inactivation, chromatin condensation), mitochondrial membrane potential, caspase activation, and Bcl-2 family protein levels.
Main Results:
- The 9.2.27PE IT induced significant cell death in malignant melanoma cells.
- Cell death occurred via protein synthesis inhibition and apoptosis, characterized by morphological and biochemical changes.
- Mitochondrial membrane depolarization and strong activation of caspase-8 and caspase-3 were not observed.
- Cytochrome c was retained within mitochondria, and the anti-apoptotic Bcl-2 protein levels remained stable.
Conclusions:
- The 9.2.27PE immunotoxin is a promising agent for treating malignant melanoma by inducing apoptosis through protein synthesis inhibition.
- Bcl-2 may contribute to maintaining mitochondrial membrane integrity during treatment.
- The immunotoxin demonstrates efficient killing of melanoma cells, suggesting therapeutic potential.
