Sun-Mi Kim

Publications (2)10.09 Total impact

• Article: Activation of IL-6R/JAK1/STAT3 Signaling Induces De Novo Resistance to Irreversible EGFR Inhibitors in Non-Small Cell Lung Cancer with T790M Resistance Mutation.

  Sun Mi Kim, Oh-Joon Kwon, Yun Kyoung Hong, Joo Hang Kim, Flavio Solca, Sang-Jun Ha, Ross A Soo, James G Christensen, Ji Hyun Lee, Byoung Chul Cho
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  ABSTRACT: The secondary T790M mutation in epidermal growth factor receptor (EGFR) is the major mechanism of acquired resistance to EGFR tyrosine kinase inhibitors (TKI) in non-small cell lung cancer (NSCLC). Although irreversible EGFR TKIs, such as afatinib or dacomitinib, have been introduced to overcome the acquired resistance, they showed a limited efficacy in NSCLC with T790M. Herein, we identified the novel de novo resistance mechanism to irreversible EGFR TKIs in H1975 and PC9-GR cells, which are NSCLC cells with EGFR T790M. Afatinib activated interleukin-6 receptor (IL-6R)/JAK1/STAT3 signaling via autocrine IL-6 secretion in both cells. Inhibition of IL-6R/JAK1/STAT3 signaling pathway increased the sensitivity to afatinib. Cancer cells showed stronger STAT3 activation and enhanced resistance to afatinib in the presence of MRC5 lung fibroblasts. Blockade of IL-6R/JAK1 significantly increased the sensitivity to afatinib through inhibition of afatinib-induced STAT3 activation augmented by the interaction with fibroblasts, suggesting a critical role of paracrine IL-6R/JAK1/STAT3 loop between fibroblasts and cancer cells in the development of drug resistance. The enhancement of afatinib sensitivity by inhibition of IL-6R/JAK1/STAT3 signaling was confirmed in in vivo PC9-GR xenograft model. Similar to afatinib, de novo resistance to dacomitinib in H1975 and PC9-GR cells was also mediated by dacomitinib-induced JAK1/STAT3 activation. Taken together, these findings suggest that IL-6R/JAK1/STAT3 signaling can be a potential therapeutic target to enhance the efficacy of irreversible EGFR TKIs in patients with EGFR T790M. Mol Cancer Ther; 11(10); 2254-64. ©2012 AACR.
  Molecular Cancer Therapeutics 08/2012; 11(10):2254-64. · 5.23 Impact Factor
• Article: Acquired resistance to cetuximab is mediated by increased PTEN instability and leads cross-resistance to gefitinib in HCC827 NSCLC cells.

  Sun Mi Kim, Ji Su Kim, Joo-Hang Kim, Chae-Ok Yun, Eun Mi Kim, Hyun Ki Kim, Flavio Solca, Soo-Young Choi, Byoung Chul Cho
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  ABSTRACT: EGFR inhibitors, including the small-molecule tyrosine kinase inhibitors such as gefitinib, and the monoclonal antibodies directed at the receptor such as cetuximab, have demonstrated promising effects in non-small cell lung cancer (NSCLC). In this study, we generated cetuximab-resistant cell lines (HCC827-CR) from HCC827 NSCLC cells to investigate acquired resistance mechanisms to cetuximab. In HCC827-CR cells, Akt was hyperactivated and its activity was persistent upon cetuximab treatment. Blockade of PI3K/Akt activity restored cetuximab sensitivity in HCC827-CR cells. Further investigation revealed that increased PTEN instability mediates constitutive Akt activation. By 1microM proteosomal inhibitor, MG-132, PTEN protein levels were restored and Akt activity was dramatically reduced. Overexpression of PTEN by transfection could not restore cetuximab sensitivity in HCC827-CR because overexpressed PTEN was degraded rapidly ( approximately 72h). The increased PTEN instability was confirmed by the treatment of HCC827-CR with a protein synthesis inhibitor, cycloheximide. In the presence of cycloheximide, overexpressed PTEN was degraded more rapidly ( approximately 12h) in HCC827-CR cells. Interestingly, HCC827-CR cells also revealed de novo resistance to gefitinib. Inhibition of PI3K/Akt signaling pathway restored sensitivity to gefitinib in HCC827-CR cells. Taken together, these data show that PTEN instability-mediated constitutive Akt activation is involved in acquired resistance mechanisms to cetuximab and also induces de novo resistance to gefitinib. Importantly, these findings suggest emergence of cross-resistance between two agents as a potential serious problem in the clinical setting.
  Cancer letters 05/2010; 296(2):150-9. · 4.86 Impact Factor