Telomerase activation by genomic rearrangements in high-risk neuroblastoma.

Neuroblastoma is a malignant paediatric tumour of the sympathetic nervous system. Roughly half of these tumours regress spontaneously or are cured by limited therapy. By contrast, high-risk neuroblastomas have an unfavourable clinical course despite intensive multimodal treatment, and their molecular basis has remained largely elusive. Here we have performed whole-genome sequencing of 56 neuroblastomas (high-risk, n = 39; low-risk, n = 17) and discovered recurrent genomic rearrangements affecting a chromosomal region at 5p15.33 proximal of the telomerase reverse transcriptase gene (TERT). These rearrangements occurred only in high-risk neuroblastomas (12/39, 31%) in a mutually exclusive fashion with MYCN amplifications and ATRX mutations, which are known genetic events in this tumour type. In an extended case series (n = 217), TERT rearrangements defined a subgroup of high-risk tumours with particularly poor outcome. Despite a large structural diversity of these rearrangements, they all induced massive transcriptional upregulation of TERT. In the remaining high-risk tumours, TERT expression was also elevated in MYCN-amplified tumours, whereas alternative lengthening of telomeres was present in neuroblastomas without TERT or MYCN alterations, suggesting that telomere lengthening represents a central mechanism defining this subtype. The 5p15.33 rearrangements juxtapose the TERT coding sequence to strong enhancer elements, resulting in massive chromatin remodelling and DNA methylation of the affected region. Supporting a functional role of TERT, neuroblastoma cell lines bearing rearrangements or amplified MYCN exhibited both upregulated TERT expression and enzymatic telomerase activity. In summary, our findings show that remodelling of the genomic context abrogates transcriptional silencing of TERT in high-risk neuroblastoma and places telomerase activation in the centre of transformation in a large fraction of these tumours.

Targeting gain of function and resistance mutations in Abl and KIT by hybrid compound design.

Mutations in the catalytic domain at the gatekeeper position represent the most prominent drug-resistant variants of kinases and significantly impair the efficacy of targeted cancer therapies. Understanding the mechanisms of drug resistance at the molecular and atomic levels will aid in the design and development of inhibitors that have the potential to overcome these resistance mutations. Herein, by introducing adaptive elements into the inhibitor core structure, we undertake the structure-based development of type II hybrid inhibitors to overcome gatekeeper drug-resistant mutations in cSrc-T338M, as well as clinically relevant tyrosine kinase KIT-T670I and Abl-T315I variants, as essential targets in gastrointestinal stromal tumors (GISTs) and chronic myelogenous leukemia (CML). Using protein X-ray crystallography, we confirm the anticipated binding mode in cSrc, which proved to be essential for overcoming the respective resistances. More importantly, the novel compounds effectively inhibit clinically relevant gatekeeper mutants of KIT and Abl in biochemical and cellular studies.

A framework for identification of actionable cancer genome dependencies in small cell lung cancer.

Small cell lung cancer (SCLC) accounts for about 15% of all lung cancers. The prognosis of SCLC patients is devastating and no biologically targeted therapeutics are active in this tumor type. To develop a framework for development of specific SCLC-targeted drugs we conducted a combined genomic and pharmacological vulnerability screen in SCLC cell lines. We show that SCLC cell lines capture the genomic landscape of primary SCLC tumors and provide genetic predictors for activity of clinically relevant inhibitors by screening 267 compounds across 44 of these cell lines. We show Aurora kinase inhibitors are effective in SCLC cell lines bearing MYC amplification, which occur in 3-7% of SCLC patients. In MYC-amplified SCLC cells Aurora kinase inhibition associates with G2/M-arrest, inactivation of PI3-kinase (PI3K) signaling, and induction of apoptosis. Aurora dependency in SCLC primarily involved Aurora B, required its kinase activity, and was independent of depletion of cytoplasmic levels of MYC. Our study suggests that a fraction of SCLC patients may benefit from therapeutic inhibition of Aurora B. Thus, thorough chemical and genomic exploration of SCLC cell lines may provide starting points for further development of rational targeted therapeutic intervention in this deadly tumor type.

Integrative genome analyses identify key somatic driver mutations of small-cell lung cancer.

Small-cell lung cancer (SCLC) is an aggressive lung tumor subtype with poor prognosis. We sequenced 29 SCLC exomes, 2 genomes and 15 transcriptomes and found an extremely high mutation rate of 7.4±1 protein-changing mutations per million base pairs. Therefore, we conducted integrated analyses of the various data sets to identify pathogenetically relevant mutated genes. In all cases, we found evidence for inactivation of TP53 and RB1 and identified recurrent mutations in the CREBBP, EP300 and MLL genes that encode histone modifiers. Furthermore, we observed mutations in PTEN, SLIT2 and EPHA7, as well as focal amplifications of the FGFR1 tyrosine kinase gene. Finally, we detected many of the alterations found in humans in SCLC tumors from Tp53 and Rb1 double knockout mice. Our study implicates histone modification as a major feature of SCLC, reveals potentially therapeutically tractable genomic alterations and provides a generalizable framework for the identification of biologically relevant genes in the context of high mutational background.

ALK mutations conferring differential resistance to structurally diverse ALK inhibitors.

PURPOSE: EML4-ALK fusions define a subset of lung cancers that can be effectively treated with anaplastic lymphoma kinase (ALK) inhibitors. Unfortunately, the duration of response is heterogeneous and acquired resistance limits their ultimate efficacy. Thus, a better understanding of resistance mechanisms will help to enhance tumor control in EML4-ALK-positive tumors. EXPERIMENTAL DESIGN: By applying orthogonal functional mutagenesis screening approaches, we screened for mutations inducing resistance to the aminopyridine PF02341066 (crizotinib) and/or the diaminopyrimidine TAE684. RESULTS: Here, we show that the resistance mutation, L1196M, as well as other crizotinib resistance mutations (F1174L and G1269S), are highly sensitive to the structurally unrelated ALK inhibitor TAE684. In addition, we identified two novel EML4-ALK resistance mutations (L1198P and D1203N), which unlike previously reported mutations, induced resistance to both ALK inhibitors. An independent resistance screen in ALK-mutant neuroblastoma cells yielded the same L1198P resistance mutation but defined two additional mutations conferring resistance to TAE684 but not to PF02341066. CONCLUSIONS: Our results show that different ALK resistance mutations as well as different ALK inhibitors impact the therapeutic efficacy in the setting of EML4-ALK fusions and ALK mutations.

Mutations in the DDR2 kinase gene identify a novel therapeutic target in squamous cell lung cancer.

UNLABELLED: While genomically targeted therapies have improved outcomes for patients with lung adenocarcinoma, little is known about the genomic alterations which drive squamous cell lung cancer. Sanger sequencing of the tyrosine kinome identified mutations in the DDR2 kinase gene in 3.8% of squamous cell lung cancers and cell lines. Squamous lung cancer cell lines harboring DDR2 mutations were selectively killed by knock-down of DDR2 by RNAi or by treatment with the multi-targeted kinase inhibitor dasatinib. Tumors established from a DDR2 mutant cell line were sensitive to dasatinib in xenograft models. Expression of mutated DDR2 led to cellular transformation which was blocked by dasatinib. A squamous cell lung cancer patient with a response to dasatinib and erlotinib treatment harbored a DDR2 kinase domain mutation. These data suggest that gain-of-function mutations in DDR2 are important oncogenic events and are amenable to therapy with dasatinib. As dasatinib is already approved for use, these findings could be rapidly translated into clinical trials. SIGNIFICANCE: DDR2 mutations are present in 4% of lung SCCs, and DDR2 mutations are associated with sensitivity to dasatinib. These findings provide a rationale for designing clinical trials with the FDA-approved drug dasatinib in patients with lung SCCs.

Synthesis and biological evaluation of 7-substituted-1-(3-bromophenylamino)isoquinoline-4-carbonitriles as inhibitors of myosin light chain kinase and epidermal growth factor receptor.

Here we present the synthesis and biological activity of a series of 7-substituted-1-(3-bromophenylamino)isoquinoline-4-carbonitriles as inhibitors of myosin light chain kinase (MLCK) and the epidermal growth factor receptor kinase (EGFR). The inhibitory effect of these molecules was found to be dependent on the nature of the substituents at the 7-position of the isoquinoline scaffold.

Frequent and focal FGFR1 amplification associates with therapeutically tractable FGFR1 dependency in squamous cell lung cancer.

Lung cancer remains one of the leading causes of cancer-related death in developed countries. Although lung adenocarcinomas with EGFR mutations or EML4-ALK fusions respond to treatment by epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) inhibition, respectively, squamous cell lung cancer currently lacks therapeutically exploitable genetic alterations. We conducted a systematic search in a set of 232 lung cancer specimens for genetic alterations that were therapeutically amenable and then performed high-resolution gene copy number analyses. We identified frequent and focal fibroblast growth factor receptor 1 (FGFR1) amplification in squamous cell lung cancer (n = 155), but not in other lung cancer subtypes, and, by fluorescence in situ hybridization, confirmed the presence of FGFR1 amplifications in an independent cohort of squamous cell lung cancer samples (22% of cases). Using cell-based screening with the FGFR inhibitor PD173074 in a large (n = 83) panel of lung cancer cell lines, we demonstrated that this compound inhibited growth and induced apoptosis specifically in those lung cancer cells carrying amplified FGFR1. We validated the FGFR1 dependence of FGFR1-amplified cell lines by FGFR1 knockdown and by ectopic expression of an FGFR1-resistant allele (FGFR1(V561M)), which rescued FGFR1-amplified cells from PD173074-mediated cytotoxicity. Finally, we showed that inhibition of FGFR1 with a small molecule led to significant tumor shrinkage in vivo. Thus, focal FGFR1 amplification is common in squamous cell lung cancer and associated with tumor growth and survival, suggesting that FGFR inhibitors may be a viable therapeutic option in this cohort of patients.

Synthesis and biological evaluation of 4-anilinoquinolines as potent inhibitors of epidermal growth factor receptor.

The mutant receptor tyrosine kinase EGFR is a validated and therapeutically amenable target for genotypically selected lung cancer patients. Here we present the synthesis and biological evaluation of a series of 6- and 7-substituted 4-anilinoquinolines as potent type I inhibitors of clinically relevant mutant variants of EGFR. Quinolines 3a and 3e were found to be highly active kinase inhibitors in biochemical assays and were further investigated for their biological effect on EGFR-dependent Ba/F3 cells and non-small cell lung cancer (NSCLC) cell lines.

Analysis of compound synergy in high-throughput cellular screens by population-based lifetime modeling.

Despite the successful introduction of potent anti-cancer therapeutics, most of these drugs lead to only modest tumor-shrinkage or transient responses, followed by re-growth of tumors. Combining different compounds has resulted in enhanced tumor control and prolonged survival. However, methods querying the efficacy of such combinations have been hampered by limited scalability, analytical resolution, statistical feasibility, or a combination thereof. We have developed a theoretical framework modeling cellular viability as a stochastic lifetime process to determine synergistic compound combinations from high-throughput cellular screens. We apply our method to data derived from chemical perturbations of 65 cancer cell lines with two inhibitors. Our analysis revealed synergy for the combination of both compounds in subsets of cell lines. By contrast, in cell lines in which inhibition of one of both targets was sufficient to induce cell death, no synergy was detected, compatible with the topology of the oncogenically activated signaling network. In summary, we provide a tool for the measurement of synergy strength for combination perturbation experiments that might help define pathway topologies and direct clinical trials.

Chemogenomic profiling provides insights into the limited activity of irreversible EGFR Inhibitors in tumor cells expressing the T790M EGFR resistance mutation.

Reversible epidermal growth factor receptor (EGFR) inhibitors are the first class of small molecules to improve progression-free survival of patients with EGFR-mutated lung cancers. Second-generation EGFR inhibitors introduced to overcome acquired resistance by the T790M resistance mutation of EGFR have thus far shown limited clinical activity in patients with T790M-mutant tumors. In this study, we systematically analyzed the determinants of the activity and selectivity of the second-generation EGFR inhibitors. A focused library of irreversible as well as structurally corresponding reversible EGFR-inhibitors was synthesized for chemogenomic profiling involving over 79 genetically defined NSCLC and 19 EGFR-dependent cell lines. Overall, our results show that the growth-inhibitory potency of all irreversible inhibitors against the EGFR(T790M) resistance mutation was limited by reduced target inhibition, linked to decreased binding velocity to the mutant kinase. Combined treatment of T790M-mutant tumor cells with BIBW-2992 and the phosphoinositide-3-kinase/mammalian target of rapamycin inhibitor PI-103 led to synergistic induction of apoptosis. Our findings offer a mechanistic explanation for the limited efficacy of irreversible EGFR inhibitors in EGFR(T790M) gatekeeper-mutant tumors, and they prompt combination treatment strategies involving inhibitors that target signaling downstream of the EGFR.

Identifying genotype-dependent efficacy of single and combined PI3K- and MAPK-pathway inhibition in cancer.

In cancer, genetically activated proto-oncogenes often induce "upstream" dependency on the activity of the mutant oncoprotein. Therapeutic inhibition of these activated oncoproteins can induce massive apoptosis of tumor cells, leading to sometimes dramatic tumor regressions in patients. The PI3K and MAPK signaling pathways are central regulators of oncogenic transformation and tumor maintenance. We hypothesized that upstream dependency engages either one of these pathways preferentially to induce "downstream" dependency. Therefore, we analyzed whether downstream pathway dependency segregates by genetic aberrations upstream in lung cancer cell lines. Here, we show by systematically linking drug response to genomic aberrations in non-small-cell lung cancer, as well as in cell lines of other tumor types and in a series of in vivo cancer models, that tumors with genetically activated receptor tyrosine kinases depend on PI3K signaling, whereas tumors with mutations in the RAS/RAF axis depend on MAPK signaling. However, efficacy of downstream pathway inhibition was limited by release of negative feedback loops on the reciprocal pathway. By contrast, combined blockade of both pathways was able to overcome the reciprocal pathway activation induced by inhibitor-mediated release of negative feedback loops and resulted in a significant increase in apoptosis and tumor shrinkage. Thus, by using a systematic chemo-genomics approach, we identify genetic lesions connected to PI3K and MAPK pathway activation and provide a rationale for combined inhibition of both pathways. Our findings may have implications for patient stratification in clinical trials.

Predicting drug susceptibility of non-small cell lung cancers based on genetic lesions.

Somatic genetic alterations in cancers have been linked with response to targeted therapeutics by creation of specific dependency on activated oncogenic signaling pathways. However, no tools currently exist to systematically connect such genetic lesions to therapeutic vulnerability. We have therefore developed a genomics approach to identify lesions associated with therapeutically relevant oncogene dependency. Using integrated genomic profiling, we have demonstrated that the genomes of a large panel of human non-small cell lung cancer (NSCLC) cell lines are highly representative of those of primary NSCLC tumors. Using cell-based compound screening coupled with diverse computational approaches to integrate orthogonal genomic and biochemical data sets, we identified molecular and genomic predictors of therapeutic response to clinically relevant compounds. Using this approach, we showed that v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations confer enhanced Hsp90 dependency and validated this finding in mice with KRAS-driven lung adenocarcinoma, as these mice exhibited dramatic tumor regression when treated with an Hsp90 inhibitor. In addition, we found that cells with copy number enhancement of v-abl Abelson murine leukemia viral oncogene homolog 2 (ABL2) and ephrin receptor kinase and v-src sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog (avian) (SRC) kinase family genes were exquisitely sensitive to treatment with the SRC/ABL inhibitor dasatinib, both in vitro and when it xenografted into mice. Thus, genomically annotated cell-line collections may help translate cancer genomics information into clinical practice by defining critical pathway dependencies amenable to therapeutic inhibition.

PTEN loss contributes to erlotinib resistance in EGFR-mutant lung cancer by activation of Akt and EGFR.

Clinical resistance to epidermal growth factor receptor (EGFR) inhibition in lung cancer has been linked to the emergence of the EGFR T790M resistance mutation or amplification of MET. Additional mechanisms contributing to EGFR inhibitor resistance remain elusive. By applying combined analyses of gene expression, copy number, and biochemical analyses of EGFR inhibitor responsiveness, we identified homozygous loss of PTEN to segregate EGFR-dependent and EGFR-independent cells. We show that in EGFR-dependent cells, PTEN loss partially uncouples mutant EGFR from downstream signaling and activates EGFR, thereby contributing to erlotinib resistance. The clinical relevance of our findings is supported by the observation of PTEN loss in 1 out of 24 primary EGFR-mutant non-small cell lung cancer (NSCLC) tumors. These results suggest a novel resistance mechanism in EGFR-mutant NSCLC involving PTEN loss.