Author of

• 11515

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  P2.05 - Poster Session 2 - Preclinical Models of Therapeutics/Imaging (ID 158)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Biology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11526

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    P2.05-011 - Characterisation of chemo-resistant syngeneic orthotopic rat pre-clinical models of mesothelioma. (ID 1718)

    09:30 - 09:30  |  Author(s): C. Weir
    • Abstract

    Background
    Malignant mesothelioma is an aggressive cancer with a low response to current therapies and consequently a poor prognosis. There is an urgent need to identify novel and more effective treatments to improve survival and quality of life for patients with mesothelioma. While a number of novel therapeutic agents have recently been examined in clinical trials, to date none of these has resulted in changes to standard management. This is due in part to a lack of robustness and relevance of the pre-clinical models used to assess new treatments. Therefore validated and biologically relevant pre-clinical models that demonstrate the clinical behaviour and drug sensitivity of mesothelioma, as well as typical resistance mechanisms, are necessary to improve the discovery of new treatments. Here we describe the generation and evaluation of chemotherapy resistant pre-clinical models of mesothelioma derived from the previously utilized syngeneic II-45 rat mesothelioma model.

    Methods
    Cell lines resistant to the current standard of care agents: cisplatin, pemetrexed gemcitabine, vinorelbine, and cisplatin and pemetrexed in combination, were generated by 15 rounds of exposure to the respective agent. Normal rat mesothelial cells (4/4 RM.4), the parental II-45 and the 5 resulting chemo-resistant mesothelioma cell lines were characterised for resistance to these and other agents. Tumours arising from syngeneic pleural engraftment of these cell lines were assessed by size, morphology, immunohistochemical markers of human malignancy, chromosomal changes and expression of genes involved in drug resistance and metabolism. Engrafted rats were assessed for survival, and circulating haematological, cytokine and biomarker profiles were generated and compared.

    Results
    Five different II-45 cell lines with approximately 2-fold resistance to the chemotherapeutic agent they were repeatedly exposed to, were established (cisplatin, p < 0.05; pemetrexed, gemcitabine, vinorelbine, p < 0.001). Cross resistance to other classes of anti-cancer agents also developed indicating potential multi-drug resistant phenotypes. Tumours derived from both the parental and chemo-resistant cell lines were immunohistochemically indistinct from human mesothelioma with positive labeling for WT1, calretinin, HBME-1, cytokeratin and popoplanin and negative labeling for two carcinoma related markers TTF-1 and CD15. Homozygous deletion of p16[INK4A]/p14[ARF], and increased expression of several members of the ATP-binding cassette transporter superfamily and Androgen receptor (AR) were demonstrated, consistent with findings in human mesothelioma. Corresponding with biomarkers studies in human disease, increased levels of osteopontin (p < 0.01), mesothelin (p < 0.01), vascular endothelial growth factor (p < 0.001) and neutrophil to lymphocyte ratio were identified relative to control bloods. Further, the acquisition of chemo-resistance resulted in changes to tumour morphology with tumours ranging from essentially epithelioid in the gemcitabine resistant tumours to entirely sarcomatoid in the combination (cisplatin and pemetrexed) resistant tumours. Overall survival was also affected by the acquisition of resistance with rats with pemetrexed resistant tumours having decreased survival.

    Conclusion
    These models display many features corresponding with the human disease, and thus provide powerful and robust pre-clinical platforms for in vivo mesothelioma studies.