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K.D. Westover



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    P3.02 - Biology/Pathology (ID 620)

    • Event: WCLC 2017
    • Type: Poster Session with Presenters Present
    • Track: Biology/Pathology
    • Presentations: 1
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      P3.02-066 - Wild-Type KRAS Mediates Growth Inhibition and Resistance to MEK Inhibitors through Dimerization with Mutant KRAS in Lung Adenocarcinoma (ID 8807)

      09:30 - 09:30  |  Author(s): K.D. Westover

      • Abstract
      • Slides

      Background:
      Mutations in KRAS are the most frequent RAS alterations in human cancers and the prevalent driver event in lung adenocarcinoma (LUAD). There are no effective targeted therapies for KRAS-driven LUAD and chemotherapy remains the standard of care. Small-molecule inhibitors of the MAPK pathway, one of the prominent downstream KRAS mediators, show minimal clinical activity either as single agents or in combination with chemotherapy. Recently, wild-type KRAS (KRAS[WT]) was shown to enhance tumor fitness in KRAS mutant AML and CRC cell lines while concomitantly increasing sensitivity to MEK inhibition. We hypothesized that dimerization between KRAS proteins could be a key regulator for lung adenocarcinoma biology and determinant of treatment response.

      Method:
      To study the role of wild-type KRAS in the context of KRAS-driven cancer cells, we used genetically inducible models of KRAS loss of heterozigosity (LOH). We developed an isogenic KRAS[MUT] inducible system that lacks endogenous HRas/NRas but harbors conditional CRE[ERT2]-controlled KRas[lox] alleles. Furthermore, we reconstituted KRAS[WT] and dimerization-deficient KRAS[D154Q] in KRAS-driven murine and human LUAD cell lines lacking the wild-type KRAS allele and evaluated the in vitro and in vivo impact on tumor progression and response to MEK inhibition.

      Result:
      KRAS[WT] decreased in vitro and in vivo fitness of human and murine KRAS mutant LUAD tumor cells. However, this phenotype was reverted upon MEK inhibition, with KRAS LOH cells being more sensitive than KRAS[WT ]expressing cells. Interestingly, both effects were dependent on wild-type/mutant KRAS dimerization and not observed with the dimerization-deficient KRAS[D154Q]. We provide a mechanistic model of the ambivalent function of KRAS[WT], linking its tumor suppressor function with increased MEK inhibitor resistance through dimerization with mutant KRAS.

      Conclusion:
      • KRAS[WT] affects cellular fitness in KRAS-driven LUAD • KRAS[WT] impairs response to MEK inhibitors in KRAS-driven LUAD • KRAS[WT] inhibitory effect is dependent on dimerization with mutant KRAS • Impaired wild-type/mutant KRAS dimerization restores sensitivity to MEK inhibitors in vivo

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    P3.08 - Locally Advanced Nsclc (ID 724)

    • Event: WCLC 2017
    • Type: Poster Session with Presenters Present
    • Track: Locally Advanced NSCLC
    • Presentations: 1
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      P3.08-004 - Phase I/II Trial of Nab-Paclitaxel or Paclitaxel Plus Carboplatin with Concurrent Radiation for Inoperable Stage IIIA/B NSCLC (ID 10220)

      09:30 - 09:30  |  Author(s): K.D. Westover

      • Abstract
      • Slides

      Background:
      To determine the overall survival of Nab-Paclitaxel (Nab) or Paclitaxel (P) plus Carboplatin (C) with concurrent radiation therapy (RT) followed by consolidative chemotherapy (CT) with Nab-C or PC for patients (pts) with Stage IIIA/B Non-small cell lung cancer (NSCLC) when compared to historical controls and to assess for the safety of each regimen to guide further investigation

      Method:
      This phase I/II trial randomized 98 pts (6 pts phase I; 92 pts phase II). 75 pts were eligible for analysis on the phase II portion. For the phase I portion, weekly 50mg/m[2] of Nab and C AUC 2 was administered with concurrent thoracic RT (60-66 Gy) followed by CT comprising 100mg/m[2] Nab on days 1,8,15 (of a 21 day cycle) and C AUC 6 on day 1 for 2 cycles. For the randomized phase II portion, patients received either arm A) weekly 50mg/m[2] P and C AUC 2 or arm B) weekly 40mg/m[2] of Nab and C AUC 2 with concurrent RT followed by consolidative 200mg/m[2] P and C AUC 6 every three weeks for 2 cycles or 100mg/m[2] Nab on days 1,8,15 (of a 21 day cycle) and C AUC 6 on day 1 for 2 cycles. The primary end point was 2-year overall survival of 50% or greater.

      Result:
      Median follow up was 14.3 months. 2 patients experienced dose-limiting toxicities on the phase I portion as defined per protocol (grade 3 febrile neutropenia and grade 4 thrombocytopenia) leading to a dose reduction of concurrent Nab from 50mg/m[2 ]to 40mg/m[2] for the phase II portion. On the Phase II portion, Grade 3+ esophagitis was 3 and 2 pts, Grade 3+ pneumonitis was 3 and 5 pts and Grade 4+ hematological adverse events was 3 and 8 pts on A and B arms respectively. The 1- and 2-year overall survival rates for arm A and B were 80.6% (95%CI 63.4-90.3) and 69.2% (51.2-81.7); and 72.5% (48.4-86.8) and 56.5% (33.7-74.1) respectively. The 1- and 2-year progression free survival were 57.5% (38.7-72.5) and 46.1% (29.2-61.5); and 45.5% (24.7-64.3) and 20.7% (6.5-40.3) for arm A and B respectively.

      Conclusion:
      For pts with locally advanced Stage IIIA/B NSCLC, both arms A and B provided 2-year overall survival rates greater than 50%. The addition of Nab to chemoradiation was overall well tolerated, prompting potential interest going forward. Further analyses of quality of life measurements are currently underway. This project was supported by Celgene. Clinical Trial information: NCT01757288

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