Exploration of Nuclear Receptor Activity and siRNA-Derived Phenotypes as Therapeutics in Non-Small Cell Lung Cancer

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2015-04-10

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Carstens, Ryan Murray

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Abstract

Nuclear hormone receptors are master regulators of diverse cellular functions implicated in tumor pathogenesis and as oncogenic drivers of many human cancers. To better understand what role these important receptors might be playing in lung cancer, three interconnected studies were initiated to assess nuclear receptor function, expression, and drugability within the lung cancer context. First, a "technology development" project was undertaken to produce and troubleshoot a CLIA-certifiable, high-throughput biomarker platform capable of mRNA expression signature assessment from FFPE specimens. The platform was used to assess NR/CoReg expression levels across a 500+ sample FFPE dataset. Categorical NR/CoReg downregulation upon tumor progression as well as survival benefits for patients retaining a non-pathological NR/CoReg expression pattern were discovered. Second, a panel of 110 NR ligands was screened across a 100-member cell line panel representative of all clinically-relevant facets of lung and breast cancers to pharmacologically interrogate these receptors as novel lung cancer targets. Following completion of this screening effort, three classes of ligands targeting the estrogen, glucocorticoid, and vitamin D receptors (ER, GR, and VDR respectively) that exert anti-proliferative phenotypes on specific subsets of the lung cancer cell lines were identified. Of particular note, several of these agents are routinely used in current clinical practice (particularly dexamethasone) and represent excellent candidates for rapid clinical translation of these findings. Finally, an RNAi-based systematic functional interrogation of NR/CoReg function was undertaken in a 100+ member cell line panel representative of all clinically-relevant facets of lung and breast cancers. A reproducible classification of lung and breast cancers was defined based on their holistic functional states as represented by the RNAi dataset. Each of these "clades" of cancer cell lines was demonstrated to be specifically targetable by unique siRNA reagents capable of inducing growth attenuation or amplification in only that clade of cell lines. Further investigation into the mechanisms of action of these siRNA reagents unexpectedly revealed that the phenotypes were largely mediated by miRNA-like seed sequence based effects rather than target-directed siRNA total complementarity silencing. Following this discovery, efforts were undertaken and subsequently completed to identify the "true" targets of these clade-specific siRNAs.

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