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Y. Saunthararajah

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    ORAL 42 - Drug Resistance (ID 160)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      ORAL42.01 - ALK-Rearranged NSCLC Adaptive Cell Plasticity with Early Onset TGFb2 Mediated Precision Drug Escape through PRC-2 Epigenetic Reprogramming (ID 3111)

      18:30 - 20:00  |  Author(s): Y. Saunthararajah

      • Abstract
      • Slides

      ALK-tyrosine kinase inhibitor (ALKi) is currently the standard precision therapy for advanced ALK(2p23)-rearranged (ALK+) non-small cell lung cancer (NSCLC), often with impressive primary responses. Nonetheless, acquired clinical resistance even in excellent/complete responders still develops ultimately with time; thus hampering long term benefits. Classic tumor rebiopsy studies that deciphered drug-resistance mechanisms focused on the “late phase” resistance at time of clinical progression in treated ALK+ NSCLC. These studies identified diverse pattern of drug-resistance mechanisms, including numerous non-dominant secondary drug-resistant ALK kinase mutations (e.g. C1156Y and L1196M), bypass signaling pathways (e.g. EGFR, KIT signaling), ALK gene amplification, and overexpression of microenvironmental factors (e.g. EGF, TGF-α, HGF). The mechanisms underlying the initial and early emergence of drug-resistance under precision therapy are poorly understood.

      EML4-ALK(+) H3122 and patient-derived ALKi acquired resistant biopsied-lung tumor tissue cells were used to investigate drug-escape mechanisms. Stem cell transcription factors QPCR array and RNA-sequencing profiling were performed on H3122 cells under ALKi up to day 14, compared with untreated and drug-washout controls. MTS cell viability assays using ALKis, in vitro and in vivo tissues QPCR assays, as well as in vivo xenograft IHC analyses were also performed. Patient-derived bronchoscopic biopsied NSCLC tissues (Ma0083) during ALKi resistance was procured and propagated in cell culture in accordance with approved institutional protocols.

      We identified that H3122 cells displayed cell plasticity and can escape ALKi’s (TAE-684, crizotinib) remarkably early after precision therapy initiation, with augmented prosurvival signaling via upregulated autocrine TGFβ2 signaling, but not TGFβ1 or β3, as early as day 14 post-treatment. We validated using both in vitro and in vivo models the upregulated cascade of tumoral TGFβ2-HOXB3-mitochondrial priming during adaptive drug-escape. The early onset drug-resistant cells were marked by reversible autocrine TGFβ2-mediated transcriptome reprogramming with reversibly enhanced EMT-ness and cancer stemness. Moreover, RNA-seq findings strongly suggest a “reverse Warburg” cell state during adaptive drug-escape. The adaptive cellular plasticity was verified also in patient-derived bronchoscopic biopsied NSCLC tissues (Ma0083) with ALKi resistance. Interestingly, inhibiting mitochondrial priming using dual BCL-2/BCL-xL BH3-mimetics ABT-263 was effective to suppress early drug-escape, but not with the BCL-2-specific agent ABT-199, suggesting BCL-xL is a key target. Importantly, we also identified upregulated HOXB3 expression correlated with the early adaptive drug-resistance cell state, emerged through dynamic remodeling of EZH2/UTX in the polycomb repressive complex-2 (PRC-2). Deregulated EZH2/UTX epigenetic balance impacted the poised chromatin state of HOXB3 promoter H3K27me3/H3K4me3 histone marks. Early drug-escape cell state was correlated with suppressed EZH2 expression, at mRNA and also protein levels, in both in vitro and in vivo models. Finally, our results showed that specific EZH2 inhibitor GSK126 promoted ALKi drug-resistance, while UTX inhibitor GSK-J4 eradicated ALKi adaptive drug-resistance.

      Our study findings provide novel insights into the initial emergence and evolution of ALK precision drug-resistance and highlighted the significance of understanding the role of adaptive tumor cell plasticity in the early drug-escape process with important therapeutic implications. Therapeutic modulation of the coordinated EZH2/UTX balance in the PRC-2 complex can profoundly impact ALKi drug treatment outcome.

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