Increased cytotoxicity of cisplatin in SK-MEL 28 melanoma cells upon down-regulation of melanoma inhibitor of apoptosis protein.
Malignant melanoma is a highly metastatic cutaneous cancer and typically refractory to chemotherapy. Deregulated apoptosis has been identified as a major cause of cancer drug resistance, and upregulated expression of the inhibitor of apoptosis protein melanom, an inhibitor of apoptosis (ML-IAP) is frequent in melanoma.



Based on the conclusion that ML-IAP expression contributes to a malignant phenotype, we down-regulated the ML-IAP mRNA using sequence optimized antisense oligonucleotides.



As measured by real-time PCR, oligonucleotides M706 and M711 inhibited ML-IAP mRNA expression by 47% and 52%, respectively in the highly metastatic and drug resistant SK-MEL28 cell line. Oligonucleotide M706, which was previously evaluated in G361 cells as the most efficient inhibitor of ML-IAP expression, was chosen to compare cell viability and drug sensitivity of these two melanoma cell lines with different p53 functionality. Protein expression was reduced by oligonucleotide M706 to 49% of the normal level and resulted in a dose-dependent specific reduction of cell viability with a maximum of 39% at 600 nM. Typical morphological changes showed that loss of viability was mainly due to cell death. In combination experiments, the use of oligonucleotide M706 resulted in a two-fold increase of cisplatin cytotoxicity at different concentrations of oligonucleotide and cisplatin (P<0.05). This is in line with our previous findings in G361 melanoma cell line, in which oligonucleotide M706 caused a 3-fold increase in cisplatin cytotoxicity.



Our data suggest the use of ML-IAP antisense oligonucleotides to overcome drug resistance in metastatic melanoma, in spite of its p53 status.
Mousavi-Shafaei
Parisa
P
Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
Ziaee
Abed-Ali
AA
Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
Zangemeister-Wittke
Uwe
U
Institute of Pharmacology, 
University of Bern, Bern, Switzerland.
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology* / Q000633:toxicity; D015536:Down-Regulation / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009841:Oligonucleotides / Q000494:pharmacology; D016372:RNA, Antisense / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C419866:BIRC7 protein, human; D051034:Inhibitor of Apoptosis Proteins; D009363:Neoplasm Proteins; D009841:Oligonucleotides; D016372:RNA, Antisense; D012333:RNA, Messenger; D002945:Cisplatin