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Figure S5,6. Effects of Nrf2 knockdown in different growth conditions

S1. Sequences of RNAi reagents S2. Data from siRNA screens S3. Genes decreased following Nrf2 KD and increased in KEAP1 mutant lung cancer cells S4. Data from CRISPR screens

Supplementary methods and figure legends

Mutations in KEAP1 and NFE2L2 (encoding the protein Nrf2) are prevalent in both adeno and squamous subtypes of non–small cell lung cancer, as well as additional tumor indications. The consequence of these mutations is stabilized Nrf2 and chronic induction of a battery of Nrf2 target genes. We show that knockdown of Nrf2 caused modest growth inhibition of cells growing in two-dimension, which was more pronounced in cell lines expressing mutant KEAP1. In contrast, Nrf2 knockdown caused almost complete regression of established KEAP1-mutant tumors in mice, with little effect on wild-type (WT) KEAP1 tumors. The strong dependency on Nrf2 could be recapitulated in certain anchorage-independent growth environments and was not prevented by excess extracellular glutathione. A CRISPR screen was used to investigate the mechanism(s) underlying this dependence. We identified alternative pathways critical for Nrf2-dependent growth in KEAP1-mutant cell lines, including the redox proteins thioredoxin and peroxiredoxin, as well as the growth factor receptors IGF1R and ERBB3. IGF1R inhibition was effective in KEAP1-mutant cells compared with WT, especially under conditions of anchorage-independent growth. These results point to addiction of KEAP1-mutant tumor cells to Nrf2 and suggest that inhibition of Nrf2 or discrete druggable Nrf2 target genes such as IGF1R could be an effective therapeutic strategy for disabling these tumors.Significance:This study identifies pathways activated by Nrf2 that are important for the proliferation and tumorigenicity of KEAP1-mutant non–small cell lung cancer.

Figure S1. Consequences of KEAP1 mutations on Nrf2 expression and ubiquitination Figure S2-4. Inducible knockdown of Nrf2 in KEAP1 mutant and WT cells and tumors

Figures S9-11. Effects of knocking down genes involved in oxidative stress

Mutations in KEAP1 and NFE2L2 (encoding the protein Nrf2) are prevalent in both adeno and squamous subtypes of non–small cell lung cancer, as well as additional tumor indications. The consequence of these mutations is stabilized Nrf2 and chronic induction of a battery of Nrf2 target genes. We show that knockdown of Nrf2 caused modest growth inhibition of cells growing in two-dimension, which was more pronounced in cell lines expressing mutant KEAP1. In contrast, Nrf2 knockdown caused almost complete regression of established KEAP1-mutant tumors in mice, with little effect on wild-type (WT) KEAP1 tumors. The strong dependency on Nrf2 could be recapitulated in certain anchorage-independent growth environments and was not prevented by excess extracellular glutathione. A CRISPR screen was used to investigate the mechanism(s) underlying this dependence. We identified alternative pathways critical for Nrf2-dependent growth in KEAP1-mutant cell lines, including the redox proteins thioredoxin and peroxiredoxin, as well as the growth factor receptors IGF1R and ERBB3. IGF1R inhibition was effective in KEAP1-mutant cells compared with WT, especially under conditions of anchorage-independent growth. These results point to addiction of KEAP1-mutant tumor cells to Nrf2 and suggest that inhibition of Nrf2 or discrete druggable Nrf2 target genes such as IGF1R could be an effective therapeutic strategy for disabling these tumors. Significance: This study identifies pathways activated by Nrf2 that are important for the proliferation and tumorigenicity of KEAP1-mutant non–small cell lung cancer.

The necroptotic cell death pathway is a key component of human pathogen defense that can become aberrantly derepressed during tissue homeostasis to contribute to multiple types of tissue damage and disease. While formation of the necrosome kinase signaling complex containing RIPK1, RIPK3, and MLKL has been extensively characterized, additional mechanisms of its regulation and effector functions likely remain to be discovered. We screened 19,883 mouse protein-coding genes by CRISPR/Cas9-mediated gene knockout for resistance to cytokine-induced necroptosis and identified 112 regulators and mediators of necroptosis, including 59 new candidate pathway components with minimal or no effect on cell growth in the absence of necroptosis induction. Among these, we further characterized the function of PTBP1, an RNA binding protein whose activity is required to maintain RIPK1 protein abundance by regulating alternative splice-site selection.

RAS mutations are highly prevalent in tumors, especially those of the lung, colon, skin and pancreas. The tissues in which these tumors arise are enriched for specific RAS isoform and codon preferences. For example, mutations in KRAS are prevalent in lung, colon and pancreas, while NRAS mutations are predominantly found in melanoma. Additionally, mutations in KRAS predominantly occur at the hotspot codons G12 or G13 and NRAS mutations predominantly occur at the hotspot codon Q61. Independent of the RAS isoform, the mutated codon and specifically the amino acid substitution at that codon contribute to distinct biochemical differences. We aim to address if different amino acid substitutions at hotspot codons induce differential transformation, i.e., KRAS G12C versus KRAS G12D. Further, we aim to address if different codons are disposed to differential transformation capabilities and if these are isoform specific, for example, if KRAS Q61 mutations are similar to KRAS G12 mutations and if KRAS Q61 mutations are similar to NRAS Q61 mutations. Additionally, we aim to characterize the transforming capacity of RAS alterations outside of hotspot codons. Hundreds of sporadic insertions and point mutations in RAS have been observed clinically, yet most of these alterations have not been experimentally investigated. To address these questions, we created a pooled library of 184 RAS (KRAS, NRAS and HRAS) alterations identified in 29,000 tumors from a panel of ~100,000 pan-cancer tumors. These alterations include missense, insertion and deletion mutations irrespective of the incidence in which they occur. The library contains the greatest representation of KRAS alterations, 104. Using this pooled library, we measured the relative proliferation effect of these RAS variants using Ba/F3 cells in a competition assay. In interleukin 3 (IL-3)-dependent murine pro B-cells, Ba/F3, expression of well-characterized RAS hotspot mutations led to IL-3-independent proliferation. Due to the robust Ba/F3 cellular transformation we observed upon expression of RAS variants, we sought to use this assay for the pooled-library screen. The Ba/F3 system enables us to interrogate the transformation capacity of the RAS alterations and to identify the relative strength of these mutations while assaying independent of tissue type. Citation Format: Amanda R. Moore, Jean-Philippe Fortin, Michael Costa, Marinella Callow, Benjamin Haley, Gerard Manning, Ethan S. Sokol, Shiva Malek. A pan-cancer RAS mutant library elucidates the transformation potential of RAS variants [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A46.

Background Genome-wide loss-of-function screens using the CRISPR/Cas9 system allow the efficient discovery of cancer cell vulnerabilities. While several studies have focused on correcting for DNA cleavage toxicity biases associated with copy number alterations, the effects of sgRNAs co-targeting multiple genomic loci in CRISPR screens have not been discussed. Results In this work, we analyze CRISPR essentiality screen data from 391 cancer cell lines to characterize biases induced by multi-target sgRNAs. We investigate two types of multi-targets: on-targets predicted through perfect sequence complementarity and off-targets predicted through sequence complementarity with up to two nucleotide mismatches. We find that the number of on-targets and off-targets both increase sgRNA activity in a cell line-specific manner and that existing additive models of gene knockout effects fail at capturing genetic interactions that may occur between co-targeted genes. We use synthetic lethality between paralog genes to show that genetic interactions can introduce biases in essentiality scores estimated from multi-target sgRNAs. We further show that single-mismatch tolerant sgRNAs can confound the analysis of gene essentiality and lead to incorrect co-essentiality functional networks. Lastly, we also find that single nucleotide polymorphisms located in protospacer regions can impair on-target activity as a result of mismatch tolerance. Conclusion We show the impact of multi-target effects on estimating cancer cell dependencies and the impact of off-target effects caused by mismatch tolerance in sgRNA-DNA binding. Electronic supplementary material The online version of this article (10.1186/s13059-019-1621-7) contains supplementary material, which is available to authorized users.

Genome-wide loss-of-function screens using the CRISPR/Cas9 system allow the efficient discovery of cancer cell vulnerabilities. While several studies have focused on correcting for DNA cleavage toxicity biases associated with copy number alterations, the effects of sgRNAs co-targeting multiple genomic loci in CRISPR screens have not been discussed yet. In this work, we analyze CRISPR essentiality screen data from 391 cancer cell lines to characterize biases induced by multi-target sgRNAs. We investigate two types of multi-targets: on-targets predicted through perfect sequence complementarity, and off-targets predicted through sequence complementarity with up to two nucleotide mismatches. We found that the number of on-targets and off-targets both increase sgRNA activity in a cell line-specific manner, and that existing additive models of gene knockout effects fail at capturing genetic interactions that may occur between co-targeted genes. We use synthetic lethality between paralog genes to show that genetic interactions can introduce biases in essentiality scores estimated from multi-target sgRNAs. We further show that single-mismatch tolerant sgRNAs can confound the analysis of gene essentiality and lead to incorrect co-essentiality functional networks.

LRP6, a co-receptor for the morphogen Wnt, aids endocytosis of anthrax complexes. Here we report that Dickkopf1 (DKK1) protein, a secreted LRP6 ligand and antagonist, is also a modulator of anthrax toxin sensitivity. shRNA-mediated gene silencing or TALEN-mediated gene knockout of DKK1 reduced sensitivity of cells to PA-dependent hybrid toxins. However, unlike the solely inhibitory effect on Wnt signaling, the effects of DKK1 overexpression on anthrax toxicity were bidirectional, depending on its endogenous expression and cell context. Fluorescence microscopy and biochemical analyses showed that DKK1 facilitates internalization of anthrax toxins and their receptors, an event mediated by DKK1-LRP6-Kremen2 complex. Monoclonal antibodies against DKK1 provided dose-dependent protection to macrophages from killing by anthrax lethal toxin (LT). Our discovery that DKK1 forms ternary structure with LRP6 and Kremen2 in promoting PA-mediated toxin internalization provides a paradigm for bacterial exploitation of mechanisms that host cells use to internalize signaling proteins.

In response to diverse stimuli, tumor cells can undergo a process resembling the epithelial-mesenchymal transition (EMT) observed during development. During this transition, epithelial-like tumor cells acquire mesenchymal-like physiologic features, become more motile and invasive, and acquire insensitivity to many therapeutic agents. While the importance of this phenomenon to cancer treatment and patient outcomes is well known, considerable heterogeneity exists across experimental models of EMT, and diverse mechanisms have been proposed to explain its various associated malignant phenotypes. Consequently, the extent to which these processes are shared uniformly across instances of EMT, as well as their relative importance in treatment contexts, remains unclear. We have used RNAseq, ATACseq, and parallelized high-throughput cell viability screening to identify differences in gene expression levels, chromatin accessibility, and drug sensitivity that correlate with EMT in a series of cell line models. By contrasting these changes across different genetic backgrounds and mechanisms of EMT induction, we are able to identify sets of elements in the transcribed and noncoding genome that are characteristic of different modes of EMT induction. Then, by comparing these candidate sets with observed differences in acquired drug sensitivity in the respective models, we were able to define a set of genetic elements whose biologic activity is likely to influence the efficacy of these compounds. Finally, we used a series of targeted CRISPR-based knockout screens to assess the relative importance of these elements to the viability of isogenic epithelial-like and mesenchymal-like cells, alone and in the presence of multiple therapeutic drugs. Using this approach, we were able to validate known mechanisms of acquired drug resistance and identify new candidate effectors. Notably, we identify multiple candidate noncoding elements containing CTCF binding sites that appear to meaningfully influence cell viability in a drug-specific manner, potentially implicating genome conformational changes in acquired therapeutic resistance. Citation Format: Russell O. Bainer, Catherine Wilson, Marinella Callow, Siyu Feng, Michael Costa, Colin Watanabe, Oleg Mayba, Eva Lin, Scott Martin, Bob Yauch, Richard Bourgon, Christiaan Klijn. Functional coding and noncoding drivers of EMT-mediated acquired drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 398.

The KDM5 family of histone demethylases catalyzes the demethylation of histone H3 on lysine 4 (H3K4) and is required for the survival of drug-tolerant persister cancer cells (DTPs). Here we report the discovery and characterization of the specific KDM5 inhibitor CPI-455. The crystal structure of KDM5A revealed the mechanism of inhibition of CPI-455 as well as the topological arrangements of protein domains that influence substrate binding. CPI-455 mediated KDM5 inhibition, elevated global levels of H3K4 trimethylation (H3K4me3) and decreased the number of DTPs in multiple cancer cell line models treated with standard chemotherapy or targeted agents. These findings show that pretreatment of cancer cells with a KDM5-specific inhibitor results in the ablation of a subpopulation of cancer cells that can serve as the founders for therapeutic relapse.