Frank S. David

Activating mutations of the noonan syndrome-associated SHP2/PTPN11 gene in human solid tumors and adult acute myelogenous leukemia.

The SH2 domain-containing protein-tyrosine phosphatase PTPN11 (Shp2) is required for normal development and is an essential component of signaling pathways initiated by growth factors, cytokines, and extracellular matrix. In many of these pathways, Shp2 acts upstream of Ras. About 50% of patients with Noonan syndrome have germ-line PTPN11 gain of function mutations. Associations between Noonan syndrome and an increased risk of some malignancies, notably leukemia and neuroblastoma, have been reported, and recent data indicate that somatic PTPN11 mutations occur in children with sporadic juvenile myelomonocytic leukemia, myelodysplasic syndrome, B-cell acute lymphoblastic leukemia, and acute myelogenous leukemia (AML). Juvenile myelomonocytic leukemia patients without PTPN11 mutations have either homozygotic NF-1 deletion or activating RAS mutations. Given the role of Shp2 in Ras activation and the frequent mutation of RAS in human tumors, these data raise the possibility that PTPN11 mutations play a broader role in cancer. We asked whether PTPN11 mutations occur in other malignancies in which activating RAS mutations occur at low but significant frequency. Sequencing of PTPN11 from 13 different human neoplasms including breast, lung, gastric, and neuroblastoma tumors and adult AML and acute lymphoblastic leukemia revealed 11 missense mutations. Five are known mutations predicted to result in an activated form of Shp2, whereas six are new mutations. Biochemical analysis confirmed that several of the new mutations result in increased Shp2 activity. Our data demonstrate that mutations in PTPN11 occur at low frequency in several human cancers, especially neuroblastoma and AML, and suggest that Shp2 may be a novel target for antineoplastic therapy.

PTPN11 (Shp2) mutations in LEOPARD syndrome have dominant negative, not activating, effects

Multiple lentigines/LEOPARD syndrome (LS) is a rare, autosomal dominant disorder characterized by Lentigines, Electrocardiogram abnormalities, Ocular hypertelorism, Pulmonic valvular stenosis, Abnormalities of genitalia, Retardation of growth, and Deafness. Like the more common Noonan syndrome (NS), LS is caused by germ line missense mutations in PTPN11, encoding the protein-tyrosine phosphatase Shp2. Enzymologic, structural, cell biological, and mouse genetic studies indicate that NS is caused by gain-of-function PTPN11 mutations. Because NS and LS share several features, LS has been viewed as an NS variant. We examined a panel of LS mutants, including the two most common alleles. Surprisingly, we found that in marked contrast to NS, LS mutants are catalytically defective and act as dominant negative mutations that interfere with growth factor/Erk-mitogen-activated protein kinasemediated signaling. Molecular modeling and biochemical studies suggest that LS mutations contort the Shp2 catalytic domain and result in open, inactive forms of Shp2. Our results establish that the pathogenesis of LS and NS is distinct and suggest that these disorders should be distinguished by mutational analysis rather than clinical presentation.

Ten Recommendations for Closing the Credibility Gap in Reporting Industry-Sponsored Clinical Research: A Joint Journal and Pharmaceutical Industry Perspective

The credibility of industry-sponsored clinical research has suffered in recent years, undercut by reports of selective or biased disclosure of research results, ghostwriting and guest authorship, and inaccurate or incomplete reporting of potential conflicts of interest.1,2 In response, many pharmaceutical companies have integrated best practices and recommendations from groups such as the International Committee of Medical Journal Editors (ICMJE), the Good Publication Practice guidelines, the Committee on Publication Ethics, the EQUATOR (Enhancing the QUAlity and Transparency Of health Resources) Network, and the Medical Publishing Insights and Practices (MPIP) initiative into their internal policies and standard operating procedures.3-10 However, a credibility gap remains: some observers, including some journal editors and academic reviewers, maintain a persistent negative view of industry-sponsored studies.11 Given industrys pivotal role in the development of new therapies, further improvements in research conduct and disclosure are needed across the industry-investigator-editor enterprise to restore confidence in industry-sponsored biomedical research. In 2008, the MPIP was founded by members of the pharmaceutical industry and the International Society for Medical Publication Professionals to elevate trust, transparency, and integrity in publishing industry–sponsored studies through education and creation of a discussion forum among industry research sponsors and biomedical journals.12,13 In 2010, the MPIP convened a roundtable of 23 journal editors and industry representatives (see the “Acknowledgments” section for a list of MPIP participants) to characterize the persistent and perceived credibility gap in industry-sponsored research and identify approaches to resolve it. Attendees agreed that there have been important improvements in the conduct and reporting of industry-sponsored studies during the past 5 years, but several opportunities remain for additional improvement. Attendees reached consensus on a top 10 list of recommendations (Table), intended to serve as a call to action for all stakeholders—authors, journal editors, research sponsors, and others—to enhance the quality and transparency of industry-sponsored clinical research reporting. Although framed in the context of industry sponsorship, many of these recommendations would enhance the credibility of clinical research publications in general, regardless of the funding source. TABLE Top 10 Recommendations for Closing the Credibility Gap in Reporting Industry-Sponsored Clinical Research

Integrins interact with focal adhesions through multiple distinct pathways.

Integrin signaling involves oligomerization and a transmembrane conformational change induced by receptor occupancy. Previous work has shown that subsets of focal adhesion‐associated proteins are recruited to integrins as a result of clustering, ligand binding, or both. However, it is unclear whether these discrete subsets reflect the differential binding of cytoplasmic proteins to the integrin or whether a single protein or set of proteins binds the integrin and is differentially activated by receptor occupancy or clustering. To address this question, we made mutations of the β1 integrin cytoplasmic domain in the context of a single subunit chimera and studied their activation of various known integrin‐mediated signaling pathways. We show here that the indirect association of the integrin with actin is distinct from its interactions with both preformed focal adhesions and FAK. Therefore, multiple independent signaling pathways exist from the integrin to the focal adhesion, which may reflect the association of independent factors with the integrin β1 cytoplasmic domain. J. Cell. Physiol. 181:74–82, 1999.

Regulation of Kidney Development by Shp2: An Unbiased Stereological Analysis

Genes that regulate renal branching morphogenesis are likely to indirectly regulate nephron endowment, but few have been validated to do so in vivo. PTPN11, which encodes the nonreceptor protein tyrosine phosphatase Shp2, acts downstream of receptor tyrosine kinases to modulate the Ras‐MAPK pathway and has been implicated in branching morphogenesis in vitro and in invertebrates, and is therefore a candidate in vivo regulator of nephron number. In this work, heterozygous null mutant Shp2+/− mice at postnatal days 30–35 were compared with their wild‐type (WT) littermates using unbiased stereology to determine if, indeed, the former had decreased nephron number due to their 50% decrease in gene/protein dosage. Although there was a trend toward decreases in total glomerular (nephron) number and kidney volume in Shp2+/− mice compared with WT, neither difference was statistically significant (11310 vs. 12198 glomeruli, P = 0.22; 62.8 mm3 vs. 66.0 mm3 renal volume; P = 0.40). We conclude that loss of 50% gene/protein dosage of PTPN11/Shp2 is insufficient to affect glomerular (and thereby nephron) number in mouse kidneys in vivo. Anat Rec, 2010.

Integrin receptor signaling: The propagation of an α-helix model

Abstract Upon ligand binding to integrin receptors, a transmembrane conformation change occurs, which is required for the engagement of the actin cytoskeleton. Integrin receptor latency clearly involves the proximal portion of the α and β cytoplasmic domains. Several experiments suggest that these two regions, which are highly conserved among integrins, may be associated, and this association is the structural basis for latency. We propose that ligand binding leads to a disruption of this association, which allows for the folding of the proximal β cytoplasmic domain. Thus, in this model, the α chain association keeps the β unfolded, and ligand binding leads to the propagation of an α helix from the transmembrane domain through the proximal β cytoplasmic domain, leading to signal transduction.

Assessing the potential clinical impact of reciprocal drug approval legislation on access to novel therapeutics in the USA: a cohort study

Objective To quantify the potential effect of reciprocal approval legislation on access to clinically impactful therapeutics in the USA. Design A cohort study. Setting New therapeutics approved by the Food and Drug Administration (FDA), European Medicines Agency (EMA) and/or Health Canada between 2000 and 2010. Main outcome measures Characteristics of new therapeutics approved by the EMA and/or Health Canada before the FDA, including mechanistic novelty, likely clinical impact, size of the affected population and FDA review outcome. Results From 2001 to 2010, 282 drugs were approved in the USA, Europe or Canada, including 172 (61%) first approved in the USA, 24 (9%) never approved in the USA, and 86 (30%) approved in the USA after Europe and/or Canada. Of the 110 new drugs approved in Europe and/or Canada before the USA, 37 (34%) had a novel mechanisms of action compared with drugs already approved by the FDA, but only 10 (9%) were for conditions lacking alternate available therapies in the USA at the time of ex-US approval—of which the majority (9/10; 90%) were indicated for rare diseases. 12 of the 37 agents with novel mechanisms of action approved first in Europe and/or Canada (32%) had their initial FDA submissions rejected for safety reasons—including 2 drugs that were ultimately withdrawn from the market in Europe due to safety concerns. Conclusions If enacted, reciprocal approval legislation would most likely benefit only a small number of US patients receiving treatment for rare diseases, and the benefit may be somewhat mitigated by an increased exposure to harms.

Maximizing the value of diagnostics in Alzheimer's disease drug development

This article examines strategic issues faced by pharmaceutical companies relating to the development of biomarkers and diagnostics for Alzheimers disease.

Post-Ligand Binding Events: Outside-In Signaling Through the Integrins

Though first identified based on their interaction with extracellular matrix (ECM) molecules, integrins clearly function as more than simply mechanical linkages between cells and the ECM. The earliest molecular biological inquiries into integrin function, in which many of the different a and 13 subunits were cloned and characterized, revealed that large numbers of different heterodimers are capable of recognizing the same ligand. This observation alone suggests that either there is a large amount of redundancy in the integrin family or different integrins which bind the same ligand can be distinguished on the basis of the intracellular signals they generate.

Creating value with financially adaptive clinical trials

This article discusses the opportunities and challenges in the application of financially adaptive clinical trials, which combine key aspects of adaptive trial design and financial analytics.