ASCL1-ERK1/2 Axis: ASCL1 restrains ERK1/2 via the dual specificity phosphatase DUSP6 to promote survival of a subset of neuroendocrine lung cancers.

The transcription factor achaete-scute complex homolog 1 (ASCL1) is a lineage oncogene that is central for the growth and survival of small cell lung cancers (SCLC) and neuroendocrine non-small cell lung cancers (NSCLC-NE) that express it. Targeting ASCL1, or its downstream pathways, remains a challenge. However, a potential clue to overcoming this challenage has been information that SCLC and NSCLC-NE that express ASCL1 exhibit extremely low ERK1/2 activity, and efforts to increase ERK1/2 activity lead to inhibition of SCLC growth and surival. Of course, this is in dramatic contrast to the majority of NSCLCs where high activity of the ERK pathway plays a major role in cancer pathogenesis. A major knowledge gap is defining the mechanism(s) underlying the low ERK1/2 activity in SCLC, determining if ERK1/2 activity and ASCL1 function are inter-related, and if manipulating ERK1/2 activity provides a new therapeutic strategy for SCLC. We first found that expression of ERK signaling and ASCL1 have an inverse relationship in NE lung cancers: knocking down ASCL1 in SCLCs and NE-NSCLCs increased active ERK1/2, while inhibition of residual SCLC/NSCLC-NE ERK1/2 activity with a MEK inhibitor increased ASCL1 expression. To determine the effects of ERK activity on expression of other genes, we obtained RNA-seq from ASCL1-expressing lung tumor cells treated with an ERK pathway MEK inhibitor and identified down-regulated genes (such as SPRY4, ETV5, DUSP6, SPRED1) that potentially could influence SCLC/NSCLC-NE tumor cell survival. This led us to discover that genes regulated by MEK inhibition suppress ERK activation and CHIP-seq demonstrated these are bound by ASCL1. In addition, SPRY4, DUSP6, SPRED1 are known suppressors of the ERK1/2 pathway, while ETV5 regulates DUSP6. Survival of NE lung tumors was inhibited by activation of ERK1/2 and a subset of ASCL1-high NE lung tumors expressed DUSP6. Because the dual specificity phosphatase 6 (DUSP6) is an ERK1/2-selective phosphatase that inactivates these kinases and has a pharmacologic inhibitor, we focused mechanistic studies on DUSP6. These studies showed: Inhibition of DUSP6 increased active ERK1/2, which accumulated in the nucleus; pharmacologic and genetic inhibition of DUSP6 affected proliferation and survival of ASCL1-high NE lung cancers; and that knockout of DUSP6 "cured" some SCLCs while in others resistance rapidly developed indicating a bypass mechanism was activated. Thus, our findings fill this knowledge gap and indicate that combined expression of ASCL1, DUSP6 and low phospho-ERK1/2 identify some neuroendocrine lung cancers for which DUSP6 may be a therapeutic target.

Ablation of EWS-FLI1 by USP9X inhibition suppresses cancer cell growth in Ewing sarcoma.

The neomorphic transcription factor EWS-FLI1 is a key driver of Ewing sarcoma. Ablation of EWS-FLI1 may present a promising therapeutic strategy for this malignancy. Here we found that the deubiquitinase, ubiquitin specific peptidase 9 X-linked (USP9X) stabilizes EWS-FLI1 protein expression in Ewing sarcoma. We show that USP9X binds the ETS domain of EWS-FLI1 in Ewing sarcoma cells and deubiquitinates EWS-FLI1 and that USP9X and EWS-FLI1 protein expression is correlated in clinical Ewing sarcoma specimens. We found that treatment of Ewing sarcoma cells with the USP9X inhibitor WP1130 mediates rapid EWS-FLI1 degradation in vitro and in vivo which coincides with reduced growth of Ewing sarcoma cells and tumors. Our results suggest that USP9X might be a potential therapeutic target to mediate EWS-FLI1 depletion in Ewing sarcoma.

Global chromatin landscapes identify candidate noncoding modifiers of cardiac rhythm.

Comprehensive cis-regulatory landscapes are essential for accurate enhancer prediction and disease variant mapping. Although cis-regulatory element (CRE) resources exist for most tissues and organs, many rare - yet functionally important - cell types remain overlooked. Despite representing only a small fraction of the heart's cellular biomass, the cardiac conduction system (CCS) unfailingly coordinates every life-sustaining heartbeat. To globally profile the mouse CCS cis-regulatory landscape, we genetically tagged CCS component-specific nuclei for comprehensive assay for transposase-accessible chromatin-sequencing (ATAC-Seq) analysis. Thus, we established a global CCS-enriched CRE database, referred to as CCS-ATAC, as a key resource for studying CCS-wide and component-specific regulatory functions. Using transcription factor (TF) motifs to construct CCS component-specific gene regulatory networks (GRNs), we identified and independently confirmed several specific TF sub-networks. Highlighting the functional importance of CCS-ATAC, we also validated numerous CCS-enriched enhancer elements and suggested gene targets based on CCS single-cell RNA-Seq data. Furthermore, we leveraged CCS-ATAC to improve annotation of existing human variants related to cardiac rhythm and nominated a potential enhancer-target pair that was dysregulated by a specific SNP. Collectively, our results established a CCS-regulatory compendium, identified novel CCS enhancer elements, and illuminated potential functional associations between human genomic variants and CCS component-specific CREs.

Integrative epigenomic analyses of small cell lung cancer cells demonstrates the clinical translational relevance of gene body methylation.

DNA methylation is a key regulator of gene expression and a clinical therapeutic predictor. We examined global DNA methylation beyond the generally used promoter areas in human small cell lung cancer (SCLC) and find that gene body methylation is a robust positive predictor of gene expression. Combining promoter and gene body methylation better predicts gene expression than promoter methylation alone including genes involved in the neuroendocrine classification of SCLC and the expression of therapeutically relevant genes including MGMT, SLFN11, and DLL3. Importantly, for super-enhancer (SE) covered genes such as NEUROD1 or MYC, using H3K27ac and NEUROD1, ASCL1, and POU2F3 ChIP-seq data, we show that genic methylation is inversely proportional to expression, thus providing a new approach to identify potential SE regulated genes involved in SCLC pathogenesis. To advance SCLC transitional research, these data are integrated into our web portal (https://discover.nci.nih.gov/SclcCellMinerCDB/) for open and easy access to basic and clinical investigators.

Inhibition of Karyopherin ß1-Mediated Nuclear Import Disrupts Oncogenic Lineage-Defining Transcription Factor Activity in Small Cell Lung Cancer.

Genomic studies support the classification of small cell lung cancer (SCLC) into subtypes based on the expression of lineage-defining transcription factors ASCL1 and NEUROD1, which together are expressed in ∼86% of SCLC. ASCL1 and NEUROD1 activate SCLC oncogene expression, drive distinct transcriptional programs, and maintain the in vitro growth and oncogenic properties of ASCL1 or NEUROD1-expressing SCLC. ASCL1 is also required for tumor formation in SCLC mouse models. A strategy to inhibit the activity of these oncogenic drivers may therefore provide both a targeted therapy for the predominant SCLC subtypes and a tool to investigate the underlying lineage plasticity of established SCLC tumors. However, there are no known agents that inhibit ASCL1 or NEUROD1 function. In this study, we identify a novel strategy to pharmacologically target ASCL1 and NEUROD1 activity in SCLC by exploiting the nuclear localization required for the function of these transcription factors. Karyopherin ß1 (KPNB1) was identified as a nuclear import receptor for both ASCL1 and NEUROD1 in SCLC, and inhibition of KPNB1 led to impaired ASCL1 and NEUROD1 nuclear accumulation and transcriptional activity. Pharmacologic targeting of KPNB1 preferentially disrupted the growth of ASCL1+ and NEUROD1+ SCLC cells in vitro and suppressed ASCL1+ tumor growth in vivo, an effect mediated by a combination of impaired ASCL1 downstream target expression, cell-cycle activity, and proteostasis. These findings broaden the support for targeting nuclear transport as an anticancer therapeutic strategy and have implications for targeting lineage-transcription factors in tumors beyond SCLC. SIGNIFICANCE: The identification of KPNB1 as a nuclear import receptor for lineage-defining transcription factors in SCLC reveals a viable therapeutic strategy for cancer treatment.

Elimination of Radiation-Induced Senescence in the Brain Tumor Microenvironment Attenuates Glioblastoma Recurrence.

Glioblastomas (GBM) are routinely treated with ionizing radiation (IR) but inevitably recur and develop therapy resistance. During treatment, the tissue surrounding tumors is also irradiated. IR potently induces senescence, and senescent stromal cells can promote the growth of neighboring tumor cells by secreting factors that create a senescence-associated secretory phenotype (SASP). Here, we carried out transcriptomic and tumorigenicity analyses in irradiated mouse brains to elucidate how radiotherapy-induced senescence of non-neoplastic brain cells promotes tumor growth. Following cranial irradiation, widespread senescence in the brain occurred, with the astrocytic population being particularly susceptible. Irradiated brains showed an altered transcriptomic profile characterized by upregulation of CDKN1A (p21), a key enforcer of senescence, and several SASP factors, including HGF, the ligand of the receptor tyrosine kinase (RTK) Met. Preirradiation of mouse brains increased Met-driven growth and invasiveness of orthotopically implanted glioma cells. Importantly, irradiated p21-/- mouse brains did not exhibit senescence and consequently failed to promote tumor growth. Senescent astrocytes secreted HGF to activate Met in glioma cells and to promote their migration and invasion in vitro, which could be blocked by HGF-neutralizing antibodies or the Met inhibitor crizotinib. Crizotinib also slowed the growth of glioma cells implanted in preirradiated brains. Treatment with the senolytic drug ABT-263 (navitoclax) selectively killed senescent astrocytes in vivo, significantly attenuating growth of glioma cells implanted in preirradiated brains. These results indicate that SASP factors in the irradiated tumor microenvironment drive GBM growth via RTK activation, underscoring the potential utility of adjuvant senolytic therapy for preventing GBM recurrence after radiotherapy. SIGNIFICANCE: This study uncovers mechanisms by which radiotherapy can promote GBM recurrence by inducing senescence in non-neoplastic brain cells, suggesting that senolytic therapy can blunt recurrent GBM growth and aggressiveness.

ASCL1, NKX2-1, and PROX1 co-regulate subtype-specific genes in small-cell lung cancer.

Lineage-defining transcription factors (LTFs) play key roles in small-cell lung cancer (SCLC) pathophysiology. Delineating the LTF-regulated genes operative in SCLC could provide a road map to identify SCLC dependencies. We integrated chromatin landscape and transcriptome analyses of patient-derived SCLC preclinical models to identify super-enhancers (SEs) and their associated genes in the ASCL1-, NEUROD1-, and POU2F3-high SCLC subtypes. We find SE signatures predict LTF-based classification of SCLC, and the SE-associated genes are enriched with those defined as common essential genes in DepMap. In addition, in ASCL1-high SCLC, we show ASCL1 complexes with NKX2-1 and PROX1 to co-regulate genes functioning in NOTCH signaling, catecholamine biosynthesis, and cell-cycle processes. Depletion of ASCL1 demonstrates it is a key dependency factor in preclinical SCLC models and directly regulates multiple DepMap-defined essential genes. We provide LTF/SE-based subtype-specific gene sets for SCLC for further therapeutic investigation.

Lentiviral-Driven Discovery of Cancer Drug Resistance Mutations.

Identifying resistance mutations in a drug target provides crucial information. Lentiviral transduction creates multiple types of mutations due to the error-prone nature of the HIV-1 reverse transcriptase (RT). Here we optimized and leveraged this property to identify drug resistance mutations, developing a technique we term LentiMutate. This technique was validated by identifying clinically relevant EGFR resistance mutations, then applied to two additional clinical anticancer drugs: imatinib, a BCR-ABL inhibitor, and AMG 510, a KRAS G12C inhibitor. Novel deletions in BCR-ABL1 conferred resistance to imatinib. In KRAS-G12C or wild-type KRAS, point mutations in the AMG 510 binding pocket or oncogenic non-G12C mutations conferred resistance to AMG 510. LentiMutate should prove highly valuable for clinical and preclinical cancer-drug development. SIGNIFICANCE: LentiMutate can evaluate a drug's on-target activity and can nominate resistance mutations before they occur in patients, which could accelerate and refine drug development to increase the survival of patients with cancer.

An in vivo functional genomics screen of nuclear receptors and their co-regulators identifies FOXA1 as an essential gene in lung tumorigenesis.

Using a mini-library of 1062 lentiviral shRNAs targeting 40 nuclear hormone receptors and 70 of their co-regulators, we searched for potential therapeutic targets that would be important during in vivo tumor growth using a parallel in vitro and in vivo shRNA screening strategy in the non-small cell lung cancer (NSCLC) line NCI-H1819. We identified 21 genes essential for in vitro growth, and nine genes specifically required for tumor survival in vivo, but not in vitro: NCOR2, FOXA1, HDAC1, RXRA, RORB, RARB, MTA2, ETV4, and NR1H2. We focused on FOXA1, since it lies within the most frequently amplified genomic region in lung adenocarcinomas. We found that 14q-amplification in NSCLC cell lines was a biomarker for FOXA1 dependency for both in vivo xenograft growth and colony formation, but not mass culture growth in vitro. FOXA1 knockdown identified genes involved in electron transport among the most differentially regulated, indicating FOXA1 loss may lead to a decrease in cellular respiration. In support of this, FOXA1 amplification was correlated with increased sensitivity to the complex I inhibitor phenformin. Integrative ChipSeq analyses reveal that FOXA1 functions in this genetic context may be at least partially independent of NKX2-1. Our findings are consistent with a neomorphic function for amplified FOXA1, driving an oncogenic transcriptional program. These data provide new insight into the functional consequences of FOXA1 amplification in lung adenocarcinomas, and identify new transcriptional networks for exploration of therapeutic vulnerabilities in this patient population.

Mithramycin suppresses DNA damage repair via targeting androgen receptor in prostate cancer.

The dependency of prostate cancer (PCa) growth on androgen receptor (AR) signaling has been harnessed to develop first-line therapies for high-risk localized and metastatic PCa treatment. However, the occurrence of aberrant expression, mutated or splice variants of AR confers resistance to androgen ablation therapy (ADT), radiotherapy or chemotherapy in AR-positive PCa. Therapeutic strategies that effectively inhibit the expression and/or transcriptional activity of full-length AR, mutated AR and AR splice variants have remained elusive. In this study, we report that mithramycin (MTM), an antineoplastic antibiotic, suppresses cell proliferation and exhibits dual inhibitory effects on expression and transcriptional activity of AR and AR splice variants. MTM blocks AR recruitment to its genomic targets by occupying AR enhancers and causes downregulation of AR target genes, which includes key DNA repair factors in DNA damage repair (DDR). We show that MTM significantly impairs DDR and enhances the effectiveness of ionizing radiation or the radiomimetic agent Bleomycin in PCa. Thus, the combination of MTM treatment with RT or radiomimetic agents, such as bleomycin, may present a novel effective therapeutic strategy for patients with high-risk, clinically localized PCa.

ASCL1 regulates neurodevelopmental transcription factors and cell cycle genes in brain tumors of glioma mouse models.

Glioblastomas (GBMs) are incurable brain tumors with a high degree of cellular heterogeneity and genetic mutations. Transcription factors that normally regulate neural progenitors and glial development are aberrantly coexpressed in GBM, conferring cancer stem-like properties to drive tumor progression and therapeutic resistance. However, the functional role of individual transcription factors in GBMs in vivo remains elusive. Here, we demonstrate that the basic-helix-loop-helix transcription factor ASCL1 regulates transcriptional targets that are central to GBM development, including neural stem cell and glial transcription factors, oncogenic signaling molecules, chromatin modifying genes, and cell cycle and mitotic genes. We also show that the loss of ASCL1 significantly reduces the proliferation of GBMs induced in the brain of a genetically relevant glioma mouse model, resulting in extended survival times. RNA-seq analysis of mouse GBM tumors reveal that the loss of ASCL1 is associated with downregulation of cell cycle genes, illustrating an important role for ASCL1 in controlling the proliferation of GBM.

Positive autofeedback regulation of Ptf1a transcription generates the levels of PTF1A required to generate itch circuit neurons.

Peripheral somatosensory input is modulated in the dorsal spinal cord by a network of excitatory and inhibitory interneurons. PTF1A is a transcription factor essential in dorsal neural tube progenitors for specification of these inhibitory neurons. Thus, mechanisms regulating Ptf1a expression are key for generating neuronal circuits underlying somatosensory behaviors. Mutations targeted to distinct cis-regulatory elements for Ptf1a in mice, tested the in vivo contribution of each element individually and in combination. Mutations in an autoregulatory enhancer resulted in reduced levels of PTF1A, and reduced numbers of specific dorsal spinal cord inhibitory neurons, particularly those expressing Pdyn and Gal Although these mutants survive postnatally, at ∼3-5 wk they elicit a severe scratching phenotype. Behaviorally, the mutants have increased sensitivity to itch, but acute sensitivity to other sensory stimuli such as mechanical or thermal pain is unaffected. We demonstrate a requirement for positive transcriptional autoregulatory feedback to attain the level of the neuronal specification factor PTF1A necessary for generating correctly balanced neuronal circuits.

RUVBL1/RUVBL2 ATPase Activity Drives PAQosome Maturation, DNA Replication and Radioresistance in Lung Cancer.

RUVBL1 and RUVBL2 (collectively RUVBL1/2) are essential AAA+ ATPases that function as co-chaperones and have been implicated in cancer. Here we investigated the molecular and phenotypic role of RUVBL1/2 ATPase activity in non-small cell lung cancer (NSCLC). We find that RUVBL1/2 are overexpressed in NSCLC patient tumors, with high expression associated with poor survival. Utilizing a specific inhibitor of RUVBL1/2 ATPase activity, we show that RUVBL1/2 ATPase activity is necessary for the maturation or dissociation of the PAQosome, a large RUVBL1/2-dependent multiprotein complex. We also show that RUVBL1/2 have roles in DNA replication, as inhibition of its ATPase activity can cause S-phase arrest, which culminates in cancer cell death via replication catastrophe. While in vivo pharmacological inhibition of RUVBL1/2 results in modest antitumor activity, it synergizes with radiation in NSCLC, but not normal cells, an attractive property for future preclinical development.

PPARγ-K107 SUMOylation regulates insulin sensitivity but not adiposity in mice.

The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) is a master regulator of adipocyte differentiation and is the target for the insulin-sensitizing thiazolidinedione (TZD) drugs used to treat type 2 diabetes. In cell-based in vitro studies, the transcriptional activity of PPARγ is inhibited by covalent attachment of small ubiquitin-related modifier (SUMOylation) at K107 in its N terminus. However, whether this posttranslational modification is relevant in vivo remains unclear. Here, using mice homozygous for a mutation (K107R) that prevents SUMOylation at this position, we demonstrate that PPARγ is SUMOylated at K107 in white adipose tissue. We further show that in the context of diet-induced obesity PPARγ-K107R-mutant mice have enhanced insulin sensitivity without the corresponding increase in adiposity that typically accompanies PPARγ activation by TZDs. Accordingly, the PPARγ-K107R mutation was weaker than TZD treatment in stimulating adipocyte differentiation in vitro. Moreover, we found that both the basal and TZD-dependent transcriptomes of inguinal and epididymal white adipose tissue depots were markedly altered in the K107R-mutant mice. We conclude that PPARγ SUMOylation at K107 is physiologically relevant and may serve as a pharmacologic target for uncoupling PPARγ's beneficial insulin-sensitizing effect from its adverse effect of weight gain.

Grade progression in urothelial carcinoma can occur with high or low mutational homology: a first-step toward tumor-specific care in initial low-grade bladder cancer.

PURPOSE: Low-grade (LG) urothelial carcinomas of the bladder (UCB) are common malignancies that are costly to surveil and rarely progress to life threatening, high-grade (HG) malignancies. It is unknown if the progression of LG to HG is a result of second primary tumors or transformation of existing LG tumors. We examined tumor genetics in patients with grade progression in urothelial carcinoma and compared to patients with no progression. RESULTS: Five patients were identified with progression. Median time from initial LG diagnosis to HG diagnosis in those experiencing progression was 19 months. Progression with both high and low mutational homology was identified. Gene alterations associated with tumor grade progression in initial low grade tumors include FBN3, CIT and HECTD4. MATERIALS AND METHODS: An institutional cancer database at a tertiary referral center in the United States identified patients who progressed from LG to HG UCB. Histologic re-review was performed by a genitourinary pathologist. Whole exome sequencing with correction for germline mutations by buffy coat subtraction was performed. Mutations were assessed between LG tumors and subsequent same-patient HG tumors and for LG patients who did not progress. Individual genes were assessed as potential predictors of risk for progression. CONCLUSIONS: Tumor grade progression occurred with both high mutational homology and low mutational homology, which may represent both true tumor progression and de-novo growth. Validation of the identified tumor genes that appeared associated with progression may provide a clinically valuable tool to providers managing patients with LG urothelial carcinomas.

Intrinsic DNA binding properties demonstrated for lineage-specifying basic helix-loop-helix transcription factors.

During development, transcription factors select distinct gene programs, providing the necessary regulatory complexity for temporal and tissue-specific gene expression. How related factors retain specificity, especially when they recognize the same DNA motifs, is not understood. We address this paradox using basic helix-loop-helix (bHLH) transcription factors ASCL1, ASCL2, and MYOD1, crucial mediators of lineage specification. In vivo, these factors recognize the same DNA motifs, yet bind largely different genomic sites and regulate distinct transcriptional programs. This suggests that their ability to identify regulatory targets is defined either by the cellular environment of the partially defined lineages in which they are endogenously expressed, or by intrinsic properties of the factors themselves. To distinguish between these mechanisms, we directly compared the chromatin binding properties of this subset of bHLH factors when ectopically expressed in embryonic stem cells, presenting them with a common chromatin landscape and cellular components. We find that these factors retain distinct binding sites; thus, specificity of binding is an intrinsic property not requiring a restricted landscape or lineage-specific cofactors. Although the ASCL factors and MYOD1 have some distinct DNA motif preference, it is not sufficient to explain the extent of the differential binding. All three factors can bind inaccessible chromatin and induce changes in chromatin accessibility and H3K27ac. A reiterated pattern of DNA binding motifs is uniquely enriched in inaccessible chromatin at sites bound by these bHLH factors. These combined properties define a subclass of lineage-specific bHLH factors and provide context for their central roles in development and disease.

FoxA transcription factor Fork head maintains the intestinal stem/progenitor cell identities in Drosophila.

Understanding how somatic stem cells respond to tissue needs is important, since aberrant somatic stem cell behaviors may lead to tissue degeneration or tumorigenesis. Here, from an in vivo RNAi screen targeting transcription factors that regulate intestinal regeneration, we uncovered a requirement for the Drosophila FoxA transcription factor Fork head (Fkh) in the maintenance of intestinal stem/progenitor cell identities. FoxA/Fkh maintains the expressions of stem/progenitor cell markers and is required for stem cell proliferation during intestinal homeostasis and regeneration. Furthermore, FoxA/Fkh prevents the intestinal stem/progenitor cells from precocious differentiation into the Enterocyte lineage, likely in cooperation with the transcription factor bHLH/Daughterless (Da). In addition, loss of FoxA/Fkh suppresses the intestinal tumorigenesis caused by Notch pathway inactivation. To reveal the gene program underlying stem/progenitor cell identities, we profiled the genome-wide chromatin binding sites of transcription factors Fkh and Da, and interestingly, around half of Fkh binding regions are shared by Da, further suggesting their collaborative roles. Finally, we identified the genes associated with their shared binding regions. This comprehensive gene list may contain stem/progenitor maintenance factors functioning downstream of Fkh and Da, and would be helpful for future gene discoveries in the Drosophila intestinal stem cell lineage.

Repression by PRDM13 is critical for generating precision in neuronal identity.

The mechanisms that activate some genes while silencing others are critical to ensure precision in lineage specification as multipotent progenitors become restricted in cell fate. During neurodevelopment, these mechanisms are required to generate the diversity of neuronal subtypes found in the nervous system. Here we report interactions between basic helix-loop-helix (bHLH) transcriptional activators and the transcriptional repressor PRDM13 that are critical for specifying dorsal spinal cord neurons. PRDM13 inhibits gene expression programs for excitatory neuronal lineages in the dorsal neural tube. Strikingly, PRDM13 also ensures a battery of ventral neural tube specification genes such as Olig1, Olig2 and Prdm12 are excluded dorsally. PRDM13 does this via recruitment to chromatin by multiple neural bHLH factors to restrict gene expression in specific neuronal lineages. Together these findings highlight the function of PRDM13 in repressing the activity of bHLH transcriptional activators that together are required to achieve precise neuronal specification during mouse development.

Taxane-Platin-Resistant Lung Cancers Co-develop Hypersensitivity to JumonjiC Demethylase Inhibitors.

Although non-small cell lung cancer (NSCLC) patients benefit from standard taxane-platin chemotherapy, many relapse, developing drug resistance. We established preclinical taxane-platin-chemoresistance models and identified a 35-gene resistance signature, which was associated with poor recurrence-free survival in neoadjuvant-treated NSCLC patients and included upregulation of the JumonjiC lysine demethylase KDM3B. In fact, multi-drug-resistant cells progressively increased the expression of many JumonjiC demethylases, had altered histone methylation, and, importantly, showed hypersensitivity to JumonjiC inhibitors in vitro and in vivo. Increasing taxane-platin resistance in progressive cell line series was accompanied by progressive sensitization to JIB-04 and GSK-J4. These JumonjiC inhibitors partly reversed deregulated transcriptional programs, prevented the emergence of drug-tolerant colonies from chemo-naive cells, and synergized with standard chemotherapy in vitro and in vivo. Our findings reveal JumonjiC inhibitors as promising therapies for targeting taxane-platin-chemoresistant NSCLCs.

Biomarker Accessible and Chemically Addressable Mechanistic Subtypes of BRAF Melanoma.

Genomic diversity among melanoma tumors limits durable control with conventional and targeted therapies. Nevertheless, pathologic activation of the ERK1/2 pathway is a linchpin tumorigenic mechanism associated with the majority of primary and recurrent disease. Therefore, we sought to identify therapeutic targets that are selectively required for tumorigenicity in the presence of pathologic ERK1/2 signaling. By integration of multigenome chemical and genetic screens, recurrent architectural variants in melanoma tumor genomes, and patient outcome data, we identified two mechanistic subtypes of BRAFV600 melanoma that inform new cancer cell biology and offer new therapeutic opportunities. Subtype membership defines sensitivity to clinical MEK inhibitors versus TBK1/IKBKε inhibitors. Importantly, subtype membership can be predicted using a robust quantitative five-feature genetic biomarker. This biomarker, and the mechanistic relationships linked to it, can identify a cohort of best responders to clinical MEK inhibitors and identify a cohort of TBK1/IKBKε inhibitor-sensitive disease among nonresponders to current targeted therapy.Significance: This study identified two mechanistic subtypes of melanoma: (1) the best responders to clinical BRAF/MEK inhibitors (25%) and (2) nonresponders due to primary resistance mechanisms (9.9%). We identified robust biomarkers that can detect these subtypes in patient samples and predict clinical outcome. TBK1/IKBKε inhibitors were selectively toxic to drug-resistant melanoma. Cancer Discov; 7(8); 832-51. ©2017 AACR.See related commentary by Jenkins and Barbie, p. 799This article is highlighted in the In This Issue feature, p. 783.