title: Anti-melanoma activity of the 9.2.27PE immunotoxin in dacarbazine resistant cells.
abstract: We have earlier shown that the 9.2.27 Pseudomonas Exotoxin A (PE) immunotoxin (IT) efficiently kills melanoma cells through inhibition of protein synthesis followed by some morphologic and biochemical features of apoptosis, a different cell killing mechanism than the one caused by Dacarbazine (DTIC), a chemotherapeutic drug used to treat malignant melanoma. To examine whether induced DTIC resistance also is a determining factor for the effectiveness of 9.2.27PE IT, we developed a DTIC resistant subline, FEMX-200DR, from the DTIC sensitive cell line FEMX. The cell variants were treated with 9.2.27PE, an IT binding to the high molecular weight-melanoma associated antigen (HMW-MAA) expressed on most malignant melanoma cells. The IT was equally effective in killing the FEMX-200DR and the FEMX cells, and the cell death was primarily caused by inhibition of protein synthesis. The DNA repair enzyme and apoptotic marker PARP, a substrate of caspase-3, was inactivated, although we observed only a minor activation of caspase-3 and caspase-8, intracellular proteases involved in apoptosis. In addition to being DTIC resistant, the FEMX-200DR cells were also more resistant to apoptosis than the parent cells as a 3 times higher concentration of the apoptotic inducer Staurosporine was needed to obtain IC50. Furthermore, in early passage malignant melanoma cell lines established from lymph node metastases, the 9.2.27PE caused a time-dependent and dose-dependent decrease in cell viability independent of their DTIC sensitivity. These findings show that the 9.2.27PE IT efficiently can cause cell death in malignant melanoma cells independent of their level of resistance to apoptosis and DTIC.
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet, The Norwegian Radium Hospital, University in Oslo, Norway. Karianne.Risberg@rr-research.no
authors.forename: Karianne
authors.initials: K
authors.lastname: Risberg
authors.forename: Oystein
authors.initials: O
authors.lastname: Fodstad
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Andersson
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D003606:Dacarbazine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000276:immunology; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000922:Immunotoxins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology*; D008545:Melanoma / Q000235:genetics / Q000276:immunology / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018906:Antineoplastic Agents, Alkylating; D001427:Bacterial Toxins; D000922:Immunotoxins; D003606:Dacarbazine; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases