Combined treatment with cisplatin and sirolimus to enhance cell death in human mesothelioma.
OBJECTIVE
Although platinum-based chemotherapy is widely used in malignant pleural mesothelioma, its modest therapeutic effect warrants identification of enhancing agents. As with many cancers, the phosphatidylinositol 3-kinase/Akt pathway is often activated in malignant pleural mesothelioma and has been implicated in the tumor's aggressiveness. Sirolimus is a well-established inhibitor of the mammalian target of rapamycin. We sought to determine whether combination treatment with sirolimus and cisplatin would enhance cell death in malignant pleural mesothelioma.


METHODS
Human malignant pleural mesothelioma cell lines were incubated with sirolimus or cisplatin alone or in combination and assayed for cell viability. To characterize phosphorylation status after treatment, Akt and downstream proteins of mammalian target of rapamycin pathway, p70 S6 kinase and 4E-BP1, were analyzed by Western blot. Effect of combination treatment was also analyzed with extreme drug resistance assay in 12 human malignant pleural mesothelioma tumors with varying resistance to cisplatin.


RESULTS
Individual malignant pleural mesothelioma cell lines exhibited a range of sensitivities to each drug without correlation with subtype. Sirolimus and cisplatin significantly (P = .029) increased cell death versus either drug alone in 4 cell lines. Combined treatment caused dephosphorylation of Akt, 4E-BP1, and p70 S6 kinase. Cell proliferation was significantly decreased in tumors subjected to sirolimus and cisplatin versus cisplatin or sirolimus alone.


CONCLUSIONS
Sirolimus appears to enhance the cytotoxicity of cisplatin in malignant pleural mesothelioma cell lines through the mammalian target of rapamycin pathway. These results provide a basis for the clinical evaluation of combined sirolimus and cisplatin chemotherapy in malignant pleural mesothelioma.
Novel Therapeutics Laboratory, Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass. 02115, USA.
Mor-Li
ML
Hartman
John Matthew
JM
Esposito
Beow Yong
BY
Yeap
David John
DJ
Sugarbaker
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008654:Mesothelioma / Q000378:metabolism / Q000473:pathology*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010997:Pleural Neoplasms / Q000378:metabolism / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D013997:Time Factors
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D002945:Cisplatin; D020123:Sirolimus