We have sequenced the genomes of 110 small cell lung cancers (SCLC), one of the deadliest human cancers. In nearly all the tumours analysed we found bi-allelic inactivation of TP53 and RB1, sometimes by complex genomic rearrangements. Two tumours with wild-type RB1 had evidence of chromothripsis leading to overexpression of cyclin D1 (encoded by the CCND1 gene), revealing an alternative mechanism of Rb1 deregulation. Thus, loss of the tumour suppressors TP53 and RB1 is obligatory in SCLC. We discovered somatic genomic rearrangements of TP73 that create an oncogenic version of this gene, TP73Δex2/3. In rare cases, SCLC tumours exhibited kinase gene mutations, providing a possible therapeutic opportunity for individual patients. Finally, we observed inactivating mutations in NOTCH family genes in 25% of human SCLC. Accordingly, activation of Notch signalling in a pre-clinical SCLC mouse model strikingly reduced the number of tumours and extended the survival of the mutant mice. Furthermore, neuroendocrine gene expression was abrogated by Notch activity in SCLC cells. This first comprehensive study of somatic genome alterations in SCLC uncovers several key biological processes and identifies candidate therapeutic targets in this highly lethal form of cancer.

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Comprehensive genomic profiles of small cell lung cancer

RAS Proteins and Their Regulators in Human Disease.

Mitogen-activated protein kinase (MAPK) cascades are key signalling pathways that regulate a wide variety of cellular processes, including proliferation, differentiation, apoptosis and stress responses. The MAPK pathway includes three main kinases, MAPK kinase kinase, MAPK kinase and MAPK, which activate and phosphorylate downstream proteins. The extracellular signal-regulated kinases ERK1 and ERK2 are evolutionarily conserved, ubiquitous serine-threonine kinases that regulate cellular signalling under both normal and pathological conditions. ERK expression is critical for development and their hyperactivation plays a major role in cancer development and progression. The Ras/Raf/MAPK (MEK)/ERK pathway is the most important signalling cascade among all MAPK signal transduction pathways, and plays a crucial role in the survival and development of tumour cells. The present review discusses recent studies on Ras and ERK pathway members. With respect to processes downstream of ERK activation, the role of ERK in tumour proliferation, invasion and metastasis is highlighted, and the role of the ERK/MAPK signalling pathway in tumour extracellular matrix degradation and tumour angiogenesis is emphasised.

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ERK/MAPK signalling pathway and tumorigenesis.

High-throughput genomic analyses may improve outcomes in patients with advanced cancers. MOSCATO 01 is a prospective clinical trial evaluating the clinical benefit of this approach. Nucleic acids were extracted from fresh-frozen tumor biopsies and analyzed by array comparative genomic hybridization, next-generation sequencing, and RNA sequencing. The primary objective was to evaluate clinical benefit as measured by the percentage of patients presenting progression-free survival (PFS) on matched therapy (PFS2) 1.3-fold longer than the PFS on prior therapy (PFS1). A total of 1,035 adult patients were included, and a biopsy was performed in 948. An actionable molecular alteration was identified in 411 of 843 patients with a molecular portrait. A total of 199 patients were treated with a targeted therapy matched to a genomic alteration. The PFS2/PFS1 ratio was >1.3 in 33% of the patients (63/193). Objective responses were observed in 22 of 194 patients (11%; 95% CI, 7%-17%), and median overall survival was 11.9 months (95% CI, 9.5-14.3 months).Significance: This study suggests that high-throughput genomics could improve outcomes in a subset of patients with hard-to-treat cancers. Although these results are encouraging, only 7% of the successfully screened patients benefited from this approach. Randomized trials are needed to validate this hypothesis and to quantify the magnitude of benefit. Expanding drug access could increase the percentage of patients who benefit. Cancer Discov; 7(6); 586-95. ©2017 AACR.See related commentary by Schram and Hyman, p. 552This article is highlighted in the In This Issue feature, p. 539.

https://cancerdiscovery.aacrjournals.org/content/candisc/early/2017/03/26/2159-8290.CD-16-1396.full.pdf

High-throughput genomics and clinical outcome in hard-to-treat advanced cancers: Results of the MOSCATO 01 trial

The endoplasmic reticulum (ER) is a membranous intracellular organelle and the first compartment of the secretory pathway As such, the ER contributes to the production and folding of approximately one-third of cellular proteins, and is thus inextricably linked to the maintenance of cellular homeostasis and the fine balance between health and disease Specific ER stress signalling pathways, collectively known as the unfolded protein response (UPR), are required for maintaining ER homeostasis The UPR is triggered when ER protein folding capacity is overwhelmed by cellular demand and the UPR initially aims to restore ER homeostasis and normal cellular functions However, if this fails, then the UPR triggers cell death In this review, we provide a UPR signalling-centric view of ER functions, from the ER's discovery to the latest advancements in the understanding of ER and UPR biology Our review provides a synthesis of intracellular ER signalling revolving around proteostasis and the UPR, its impact on other organelles and cellular behaviour, its multifaceted and dynamic response to stress and its role in physiology, before finally exploring the potential exploitation of this knowledge to tackle unresolved biological questions and address unmet biomedical needs Thus, we provide an integrated and global view of existing literature on ER signalling pathways and their use for therapeutic purposes

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Endoplasmic Reticulum Stress signalling - from basic mechanisms to clinical applications

The identification of mutationally activated BRAF in many cancers altered our conception of the part played by the RAF family of protein kinases in oncogenesis In this Review, we describe the development of BRAF inhibitors and the results that have emerged from their analysis in both the laboratory and the clinic We discuss the spectrum of RAF mutations in human cancer and the complex interplay between the tissue of origin and the response to RAF inhibition Finally, we enumerate mechanisms of resistance to BRAF inhibition that have been characterized and postulate how strategies of RAF pathway inhibition may be extended in scope to benefit not only the thousands of patients who are diagnosed annually with BRAF-mutated metastatic melanoma but also the larger patient population with malignancies harbouring mutationally activated RAF genes that are ineffectively treated with the current generation of BRAF kinase inhibitors

/pdf/targeting-raf-kinases-for-cancer-therapy-braf-mutated-1p7smlst3b.pdf

Targeting RAF kinases for cancer therapy: BRAF-mutated melanoma and beyond

Malignant melanoma is frequently driven by mutational activation of v-raf murine sarcoma viral oncogene homolog B1 (BRAF) accompanied by silencing of the phosphatase and tensin homology (PTEN) tumor suppressor. Despite the implied importance of PI3K signaling in PTENNull melanomas, mutational activation of the gene encoding the catalytic subunit of PI3Kα (PIK3CA), is rarely detected. Since PTEN has both PI3-lipid phosphatase–dependent and –independent tumor suppressor activities, we investigated the contribution of PI3K signaling to BRAFV600E-induced melanomagenesis using mouse models, cultured melanoma cells, and PI3K pathway–targeted inhibitors. These experiments revealed that mutationally activated PIK3CAH1047R cooperates with BRAFV600E for melanomagenesis in mice. Moreover, pharmacological inhibition of PI3Ks prevented growth of BRAFV600E/PTENNull melanomas in vivo and in tissue culture. Combined inhibition of BRAFV600E and PI3K had more potent effects on the regression of established BRAFV600E/PTENNull melanomas and cultured melanoma cells than individual blockade of either pathway. Surprisingly, growth of BRAFV600E/PIK3CAH1047R melanomas was dependent on the protein kinase AKT; however, AKT inhibition had no effect on growth of BRAFV600E/PTENNull melanomas. These data indicate that PTEN silencing contributes a PI3K-dependent, but AKT-independent, function in melanomagenesis. Our findings enhance our knowledge of how BRAFV600E and PI3K signaling cooperate in melanomagenesis and provide preclinical validation for combined pathway–targeted inhibition of PI3K and BRAFV600E in the therapeutic management of BRAFV600E/PTENNull melanomas.

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Differential AKT dependency displayed by mouse models of BRAFV600E-initiated melanoma

Phosphatidylinositide 3′ (PI3′)-lipid signaling cooperates with oncogenic BRAFV600E to promote melanomagenesis. Sustained PI3′-lipid production commonly occurs via silencing of the PI3′-lipid phosphatase PTEN or, less commonly, through mutational activation of PIK3CA, encoding the 110-kDa catalytic subunit of PI3′-kinase-α (PI3Kα). To define the PI3K catalytic isoform dependency of BRAF-mutated melanoma, we used pharmacologic, isoform-selective PI3K inhibitors in conjunction with melanoma-derived cell lines and genetically engineered mouse (GEM) models. Although BRAFV600E/PIK3CAH1047R melanomas were sensitive to the antiproliferative effects of selective PI3Kα blockade, inhibition of BRAFV600E/PTENNull melanoma proliferation required combined blockade of PI3Kα, PI3Kδ, and PI3Kγ, and was insensitive to PI3Kβ blockade. In GEM models, isoform-selective PI3K inhibition elicited cytostatic effects, but significantly potentiated melanoma regression in response to BRAFV600E pathway–targeted inhibition. Interestingly, PI3K inhibition forestalled the onset of MEK inhibitor resistance in two independent GEM models of BRAFV600E-driven melanoma. These results suggest that combination therapy with PI3K inhibitors may be a useful strategy to extend the duration of clinical response of patients with BRAF-mutated melanoma to BRAFV600E pathway–targeted therapies.

Significance: Although BRAFV600E pathway–targeted therapies elicit melanoma regression, the onset of drug resistance limits the durability of response. Here, we show that combined treatment with PI3K inhibitors significantly forestalled the onset of MEK1/2 inhibitor–resistant disease in BRAF-mutated GEM melanoma models. These results provide a conceptual framework for the combined deployment of BRAFV600E plus PI3K pathway–targeted inhibitors in the treatment of a subset of patients with BRAF-mutated melanoma.

https://cancerdiscovery.aacrjournals.org/content/candisc/5/2/143.full.pdf

PI3'-Kinase Inhibition Forestalls the Onset of MEK1/2 Inhibitor Resistance in BRAF-Mutated Melanoma

Malignant conversion of BRAF- or NRAS-mutated melanocytes into melanoma cells can be promoted by PI3'-lipid signaling. However, the mechanism by which PI3'-lipid signaling cooperates with mutationally activated BRAF or NRAS has not been adequately explored. Using human NRAS- or BRAF-mutated melanoma cells that co-express mutationally activated PIK3CA, we explored the contribution of PI3'-lipid signaling to cell proliferation. Despite mutational activation of PIK3CA, melanoma cells were more sensitive to the biochemical and antiproliferative effects of broader spectrum PI3K inhibitors than to an α-selective PI3K inhibitor. Combined pharmacological inhibition of MEK1/2 and PI3K signaling elicited more potent antiproliferative effects and greater inhibition of the cell division cycle compared to single-agent inhibition of either pathway alone. Analysis of signaling downstream of MEK1/2 or PI3K revealed that these pathways cooperate to regulate cell proliferation through mTORC1-mediated effects on ribosomal protein S6 and 4E-BP1 phosphorylation in an AKT-dependent manner. Although PI3K inhibition resulted in cytostatic effects on xenografted NRASQ61H /PIK3CAH1047R melanoma, combined inhibition of MEK1/2 plus PI3K elicited significant melanoma regression. This study provides insights as to how mutationally activated PIK3CA acts in concert with MEK1/2 signaling to cooperatively regulate mTORC1/2 to sustain PIK3CA-mutated melanoma proliferation.

PIK3CA-mutated melanoma cells rely on cooperative signaling through mTORC1/2 for sustained proliferation.

An enzyme previously implicated in gene regulation has now been found to have a role in cancer progression, potentiating an intracellular signalling pathway that is driven by a mutated K-Ras protein. See Letter p.283
 SMYD3 is a largely cytoplasmic lysine methyltransferase that is overexpressed in several human tumours. This paper reports that SMYD3 is required for Ras-induced tumour development in mouse models. The enzyme methylates MAP3K2, which inhibits binding of a phosphatase and potentiates the Ras/Raf signalling pathway. These results reveal an unexpected role for lysine methylation in a kinase signalling pathway and establish SMYD3 as a potential therapeutic target.

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Marian M. Deuker

Papers

Targeting RAF kinases for cancer therapy: BRAF-mutated melanoma and beyond

Differential AKT dependency displayed by mouse models of BRAFV600E-initiated melanoma

PI3'-Kinase Inhibition Forestalls the Onset of MEK1/2 Inhibitor Resistance in BRAF-Mutated Melanoma

PIK3CA-mutated melanoma cells rely on cooperative signaling through mTORC1/2 for sustained proliferation.

Cancer biology: Enzyme meets a surprise target.