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Although targeted therapies often elicit profound initial patient responses, these effects are transient due to residual disease leading to acquired resistance. How tumors transition between drug responsiveness, tolerance and resistance, especially in the absence of preexisting subclones, remains unclear. In epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma cells, we demonstrate that residual disease and acquired resistance in response to EGFR inhibitors requires Aurora kinase A (AURKA) activity. Nongenetic resistance through the activation of AURKA by its coactivator TPX2 emerges in response to chronic EGFR inhibition where it mitigates drug-induced apoptosis. Aurora kinase inhibitors suppress this adaptive survival program, increasing the magnitude and duration of EGFR inhibitor response in preclinical models. Treatment-induced activation of AURKA is associated with resistance to EGFR inhibitors in vitro, in vivo and in most individuals with EGFR-mutant lung adenocarcinoma. These findings delineate a molecular path whereby drug resistance emerges from drug-tolerant cells and unveils a synthetic lethal strategy for enhancing responses to EGFR inhibitors by suppressing AURKA-driven residual disease and acquired resistance.

Trever Bivona and colleagues use an in vivo lung cancer metastasis model to show that the transcriptional repressor Capicua (CIC) suppresses invasion and metastasis. CIC inactivation leads to upregulation of ETV4 and MMP24, which is necessary and sufficient for metastasis. Metastasis is the leading cause of death in people with lung cancer, yet the molecular effectors underlying tumor dissemination remain poorly defined. Through the development of an in vivo spontaneous lung cancer metastasis model, we show that the developmentally regulated transcriptional repressor Capicua (CIC) suppresses invasion and metastasis. Inactivation of CIC relieves repression of its effector ETV4 , driving ETV4-mediated upregulation of MMP24, which is necessary and sufficient for metastasis. Loss of CIC, or an increase in levels of its effectors ETV4 and MMP24, is a biomarker of tumor progression and worse outcomes in people with lung and/or gastric cancer. Our findings reveal CIC as a conserved metastasis suppressor, highlighting new anti-metastatic strategies that could potentially improve patient outcomes.

Circulating tumour DNA (ctDNA) analysis facilitates studies of tumour heterogeneity. Here we employ CAPP-Seq ctDNA analysis to study resistance mechanisms in 43 non-small cell lung cancer (NSCLC) patients treated with the third-generation epidermal growth factor receptor (EGFR) inhibitor rociletinib. We observe multiple resistance mechanisms in 46% of patients after treatment with first-line inhibitors, indicating frequent intra-patient heterogeneity. Rociletinib resistance recurrently involves MET , EGFR , PIK3CA , ERRB2 , KRAS and RB1 . We describe a novel EGFR L798I mutation and find that EGFR C797S, which arises in ∼33% of patients after osimertinib treatment, occurs in <3% after rociletinib. Increased MET copy number is the most frequent rociletinib resistance mechanism in this cohort and patients with multiple pre-existing mechanisms (T790M and MET ) experience inferior responses. Similarly, rociletinib-resistant xenografts develop MET amplification that can be overcome with the MET inhibitor crizotinib. These results underscore the importance of tumour heterogeneity in NSCLC and the utility of ctDNA-based resistance mechanism assessment. EGFR -mutant non-small cell lung cancer is routinely treated with EGFR inhibitors, although resistance inevitably develops. Here, the authors sequence circulating tumour DNA and show that resistance to the third-generation inhibitor rociletinib is heterogeneous and recurrently involves somatic alterations of MET , EGFR , PIK3CA , ERRB2 , and KRAS .

Nature Communications 7: Article number: 11815 (2016); Published 10 June 2016; Updated 14 November 2016 Previous work by Del Re et al. describing the emergence of KRAS mutations following treatment of non-small cell lung cancer patients with EGFR tyrosine kinase inhibitors was inadvertently omitted from the reference list of this Article and should have been cited as follows.

The immune stimulation induced by short interfering RNAs (siRNAs) has been reported to be quieted or abrogated by methoxy or fluoro modifications of the 2′ position of the ribose sugar. However, variables such as the type of modification, nucleotide preference, and strand bias have not been systematically evaluated. Here, we report the results of a screen of several modified siRNAs via a human peripheral blood monocyte cytokine induction assay. Unlike corresponding modifications of guanosine, cytidine, or uridine, 2′-fluoro modification of adenosine significantly reduced cytokine induction while retaining siRNA knockdown activity. The results of this study suggest adenosine as an optimal target for modification.

Endogenous and exogenous short interfering RNAs (siRNAs) require a 5′-phosphate for loading into Ago2 and cleavage of the target mRNA. We applied a synthetic 5′-phosphate to siRNA guide strands to evaluate if phosphorylation in vivo is rate limiting for maximal siRNA knockdown and duration. We report, for the first time, an in vivo evaluation of siRNAs with a synthetic 5′-phosphate compared to their unphosphorylated versions. siRNAs that contained a 5′-phosphate had the same activity in vivo compared with unphosphorylated siRNAs, indicating phosphorylation of an siRNA is not a rate limiting step in vivo .