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B. Helfrich



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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
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      P2.05-017 - Evaluation of the selective aurora B kinase inhibitor AZD1152 in SCLC lines with and without MYC family amplification. (ID 2877)

      09:30 - 09:30  |  Author(s): B. Helfrich

      • Abstract

      Background
      Background: Small cell lung cancer (SCLC) has an overall 5-year survival rate of < 5% despite initial response rates to first line chemotherapy of 70-90%. MYC family amplification occurs in 30% of SCLC and MYC amplified tumors have been shown to be dependent on aurora kinase B for their survival. Aurora B kinase (AURKB) is a chromosomal passenger protein that plays a critical role in mitosis by regulating chromosome alignment, accurate segregation, and cytokinesis during the mitotic stages. We evaluated the effects of the selective aurora B kinase inhibitor AZD1152-HQPA (active drug) in a panel of 15-SCLC lines.

      Methods
      Methods: Nine lines had MYC-family amplification (MYC-5 lines, MYCL1-2 lines, MYCN-2 lines) and 6-lines had no MYC-family amplification. Growth inhibition by AZD1152-HQPA was assessed by tetrazolium based assays. Apoptosis was determined using the DNA binding dyes YOPRO and propidium iodine (PI) and analysis by flow cytomery. The induction of polyploidy was evaluated by flow cytometry following PI staining of the DNA. The effect of AZD1152-HQPA on anchorage independent growth was determined by soft agar colony forming assays. Finally, we evaluated the in vivo efficacy of AZD1152 (prodrug) on SCLC xenografts in nude mice.

      Results
      Results: AZD1152-HQPA GI50 values for the 4 most sensitive SCLC lines were 11-30 nM and < 25% of untreated control growth was observed at 60 nM. Five lines had GI50 values of 30-60 nM but at 600 nM AZD1152-HQPA cell viability remained at 49-55% of untreated control growth. In the remaining 6-lines cell viability at 600 nM was 60-93% of control growth. Growth inhibition marginally correlated with MYC amplification (p=0.044) and was strongly correlated with MYC + MYCL1 + MYCN amplification (p=0.011). Apoptosis (20-28%) was induced by 30 nM AZD1152-HQPA at 24-48 hours in the most sensitive cell lines. Marked increases in DNA ploidy (8N) was observed after 24 hour exposure to AZD1152-HQPA (30nM) in the most sensitive cell lines and at 48 hours in the 5 intermediate lines and in 2 of the resistant lines. In vivo AZD1152 (i.p. 100 mg/kg/M-F for two weeks) induced tumor regression in nude mice implanted with a sensitive cell line. AZD1152 at 50mg/kg/day inhibited tumor growth; however these tumors began growing following treatment cessation. A resistant line was also implanted into nude mice and AZD1152 at 50 and 100 mg/kg/day caused tumor regression. Polyploidy was induced in this cell line at 48 hours post 30 nM AZD1152-HQPA. Anchorage independent growth in this resistant line was also completely inhibited by AZD1152-HQPA 25 nM. The doses of AZD1152-HQPA used in this study are within the range reported to be clinically achievable.

      Conclusion
      Conclusions: AZD1152-HQPA growth inhibition significantly correlated with MYC-family amplification in SCLC lines but some SCLC lines without MYC-family amplification were also inhibited. Additional biomarkers are needed to identify SCLC patients most likely to respond to AZD1152.

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    P3.05 - Poster Session 3 - Preclinical Models of Therapeutics/Imaging (ID 159)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P3.05-014 - Eribulin, a tublin targeted chemotherapeutic agent, inhibits the in vitro growth of small cell lung cancer cell lines. (ID 2304)

      09:30 - 09:30  |  Author(s): B. Helfrich

      • Abstract

      Background
      Background: New therapeutic strategies are urgently needed for small cell lung cancer (SCLC) which accounts for approximately 29,000 cases annually in the U.S. SCLC tumors have rapid doubling times and a propensity for early development of widespread metastatic disease. There have been no therapeutic advances in recent decades. The microtubule-targeting agent eribulin is a mechanistically-unique inhibitor of microtubule dynamics. Eribulin binds with high affinity to a maximum of 15 distinct beta-tubulin binding sites inhibiting microtubule growth by depolymerization and sequestration of tubulin into non-productive aggregates. Eribulin is currently FDA approved for the treatment of metastatic breast cancer patients with a demonstrated significant increase in overall survival in patients that are refractory or resistant to multiple chemotherapy agents. We investigated the effects of eribulin in a panel of 15-human SCLC lines.

      Methods
      Methods: Growth inhibition by eribulin was assessed by tetrazolium based assays at 5-days post treatment with varying drug concentrations and the growth inhibitory (GI50) was calculated. Erbulin induced cell cycle arrest was monitored following propidium iodine staining and analysis by FACS. Apoptosis was determined by using the DNA binding dyes YOPRO and PI and analysis by FACS.

      Results
      Results: Eribulin inhibited the growth of 13 of the cell lines. Four SCLC lines had GI50s of < 1 nM and 9-lines had eribulin GI50 values of 1-6 nM. These GI50 are similar to those reported in breast cancer cell lines. The eribulin IC50 value in the remaining 2-lines was > 100 nM. We are currently exploring clinical and gene expression differences that may explain the high sensitivity and resistance of different cell lines. A two to three-fold increase in the % cells in the G2/M phase of the cell cycle were observed following an 18-hour exposure to eribulin at concentrations of ≤ 5 nM in all cell lines growth inhibited by eribulin. Apoptosis assays are ongoing and in vitro studies of eribulin in combination with radiation are planned.

      Conclusion
      Conclusions: Erbulin inhibited the growth of SCLC lines and induced a significant G2/M arrest. Confirmation of growth inhibition of SCLC cell lines in an in vivo nude mouse model would support human studies in SCLC patients.