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  OA08 - Mesothelioma: Immunotherapy and microRNA for Diagnosis and Treatment (ID 907)

  • Event: WCLC 2018
  • Type: Oral Abstract Session
  • Track: Mesothelioma
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/24/2018, 15:15 - 16:45, Room 201 BD

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    OA08.06 - Tumour Suppressor MicroRNAs Modulate Drug Resistance by Targeting Anti-Apoptotic Pathways in Malignant Pleural Mesothelioma (MPM) (ID 13539)

    16:10 - 16:20  |  Author(s): Monica Phimmachanh
    • Abstract
    • Presentation
    • Slides

    Background
    

    Malignant Pleural mesothelioma (MPM) is an aggressive thoracic malignancy with limited treatment options. MPM has a poor prognosis, predominately due to its inherent drug resistance and its limited response to current therapies. Aberrant microRNA expression is a common event in neoplasms with many implicated in chemo-resistance, however their role in MPM drug resistance is largely unexplored.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    To investigate the role of microRNAs in MPM drug resistance, we generated MPM cell lines with acquired drug resistance to cisplatin, gemcitabine and vinorelbine by periodic treatment with the IC50 of each chemotherapeutic agent. Expression levels of mature microRNAs were compared between parental MPM cell lines and cell lines with acquired drug resistance using RT-qPCR. BCL2 is an anti-apoptotic gene and a known target of miR-15a/16-1 and miR-34a. To determine if microRNAs potentiate drug sensitization via a Bcl-2 mediated anti-apoptotic pathway, drug sensitivity assays were carried out following reverse-transfection with microRNA mimics and Bcl-2 siRNAs combined with cisplatin, gemcitabine and vinorelbine treatment. Following microRNA mimic transfection in 6-well plates, levels of apoptosis and necrosis were determined by PI and annexin V staining while Bcl-2 mRNA and protein expression was determined by RT-qPCR and Western blotting respectively.

    4c3880bb027f159e801041b1021e88e8 Result
    

    Expression of miR-15a/16-1 and miR-34a was downregulated in MPM cells with acquired resistance to cisplatin, gemcitabine and vinorelbine, compared to the parental counterpart. Transfection with mimics corresponding to miR-15a/16-1 were most effective in improving sensitivity to all chemotherapeutics tested in drug resistant cell lines. In parental cell lines, miR-15a/16-1 mimic induced sensitization was also observed but restoration of miR-34a and miR-34b was also capable of improving response to cisplatin and vinorelbine. Forced miR-15/16 and miR-34a expression also sensitized both parental and resistant cell lines to cisplatin, gemcitabine and vinorelbine via induction of apoptosis; their ability to increase levels of drug-induced apoptosis suggest they may sensitize cells to chemotherapeutics via an anti-apoptotic mechanism involving Bcl-2. miR-15a/16-1 and miR-34a transfection caused Bcl-2 mRNA and protein reduction, confirming their regulation of Bcl-2 in MPM. Furthermore, siRNA induced knockdown of Bcl-2 also induced a modest improvement in drug sensitivity.

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    Restoration of microRNA expression sensitized both drug resistant and parental cell lines to chemotherapeutic agents and increased levels of drug-induced apoptosis. Taken together, this data suggests that miR-15a/16-1 and miR-34a are involved in the acquired and intrinsic drug resistance phenotype of MPM cells in part by modulation of apoptotic mechanisms via targeting Bcl-2.

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