Mutations of the epidermal growth factor receptor (EGFR) gene have been identified in specimens from patients with non-small-cell lung cancer who have a response to anilinoquinazoline EGFR inhibitors. Despite the dramatic responses to such inhibitors, most patients ultimately have a relapse. The mechanism of the drug resistance is unknown. Here we report the case of a patient with EGFR-mutant, gefitinib-responsive, advanced non-small-cell lung cancer who had a relapse after two years of complete remission during treatment with gefitinib. The DNA sequence of the EGFR gene in his tumor biopsy specimen at relapse revealed the presence of a second point mutation, resulting in threonine-to-methionine amino acid change at position 790 of EGFR. Structural modeling and biochemical studies showed that this second mutation led to gefitinib resistance.

SummaryPsoriatic skin is characterized by microvascular hyperpermeability and angioproliferation, but the mechanisms responsible are unknown. We report here that the hyperplastic epidermis of psoriatic skin expresses strikingly increased amounts of vascular permeability factor (VPF; vascular endothelial growth factor), a selective endothelial cell mitogen that enhances microvascular permeability. Moreover, two VPF receptors, kdr and fit-l, are overexpressed by papillary dermal microvascular endothelial cells. Transforming growth factor ot (TGF-o 0, a cytokine that is also overexpressed in psoriatic epidermis, induced VPF gene expression by cultured epidermal keratinocytes. VPF secreted by TGF-c~-stimulated keratinocytes was bioactive, as demonstrated by its mitogenic effect on dermal microvascular endothelial cells in vitro. Together, these findings suggest that TGF-ot regulates VPF expression in psoriasis by an autocrine mechanism, leading to vascular hyperpermeability and angiogenesis. Similar mechanisms may operate in tumors and in healing skin wounds which also commonly express both VPF and TGF-ol. p! soriasis is a common, chronic skin disease characterized by recurrent erythematous skin plaques that exhibit epidermal hyperplasia, a variable inflammatory cell infiltrate, and abnormalities of the papillary dermal vasculature (1-4). Microvessels in the papillary dermis of psoriatic plaques are elongate, dilated, and hyperpermeable (5, 6) and more closely resemble postcapillary venules than the capillary loops of normal skin (7,8). Whereas vascular changes may precede inflammatory cell infiltration in developing psoriatic plaques, and may reappear before clinical relapse (9-11), there is increasing evidence that epidermal alterations precede capillary leakiness and vascular anomalies in the development of psoriatic skin lesions (12). Moreover, a previous study demonstrated that the angiogenic properties of psoriatic skin were associated with the epidermis, not the dermis (13).Vascular permeability factor (VPF) is a 32-42-kD glycosylated protein that is overexpressed by many human and animal tumors (14-17) and by the epidermis of healing wounds (18), conditions that, like psoriasis, are associated with enhanced microvascular permeability and angiogenesis. Two tyrosine kinase receptors for VPF, kdr and fit-l, are also overexpressed in the microvessels of tumors that overexpress VPF (19)(20)(21). In vivo, VPF enhances microvascular permeability with a potency some 50,000 times that of histamine and induces angiogenesis (22)(23)(24)(25). In vitro, VPF is a selective mitogen for cultured endothelial cells, hence its alternate name, vascular endothelial growth factor (26, 27). We hypothesized that a cytokine with these properties might play an important role in the pathogenesis of psoriasis.In this report, we demonstrate increased expression of VPF mRNA by the hyperplastic epidermis of lesional psoriatic skin and increased expression of two VPF receptors in psoriatic dermal microvessels. In vitro investigations showe...

Since first being described as such by Galen of Pergamum (130-200 ad), the thymus has remained an "organ of mystery" throughout the 2000-year history of medicine. The thymus reaches its maximum weight in puberty and subsequently undergoes involution, and thus is hardly an eye-catching structure on imaging studies performed in healthy adults. However, once there has been involvement of the thymus by a disease process, the gland demonstrates a variety of clinical and radiologic manifestations that require comprehensive understanding of each entity. Furthermore, it is important for radiologists to be familiar with the current World Health Organization histologic classification scheme for thymic epithelial tumors and to understand its clinical-pathologic, radiologic, and prognostic features.

PDZK1, a multi-PDZ domain containing adaptor protein, interacts with various membrane proteins, including the high density lipoprotein (HDL) receptor scavenger receptor class B type I (SR-BI). Here we show that PDZK1 controls in a tissue-specific and post-transcriptional fashion the expression of SR-BI in vivo. SR-BI protein expression in PDZK1 knock-out (KO) mice was reduced by 95% in the liver, 50% in the proximal intestine, and not affected in steroidogenic organs (adrenal, ovary, and testis). Thus, PDZK1 joins a growing list of adaptors that control tissue-specific activity of cell surface receptors. Hepatic expression of SR-BII, a minor splice variant with an alternative C-terminal cytoplasmic domain, was not affected in PDZK1 KO mice, suggesting that binding of PDZK1 to SR-BI is required for controlling hepatic SR-BI expression. The loss of hepatic SR-BI was the likely cause of the elevation in plasma total and HDL cholesterol and the increase in HDL particle size in PDZK1 KO mice, phenotypes similar to those observed in SR-BI KO mice. PDZK1 KO mice differed from SR-BI KO mice in that the ratio of unesterified to total plasma cholesterol was normal, females were fertile, and cholesteryl ester stores in steroidogenic organs were essentially unaffected. These differences may be due to nearly normal extrahepatic expression of SR-BI in PDZK1 KO mice. The PDZK1-dependent regulation of hepatic SR-BI and, thus, lipoprotein metabolism supports the proposal that this adaptor may represent a new target for therapeutic intervention in cardiovascular disease.

Key Points• Human hematopoietic cells develop within human iPSCderived teratomas in immunodeficient mice.• Co-transplantation of OP9 stromal cells along with human iPSCs increases hematopoietic specification within teratomas.

VPF/VEGF acts selectively on the vascular endothelium to enhance permeability, induce cell migration and division, and delay replicative senescence. To understand the changes in gene expression during endothelial senescence, we investigated genes that were differentially expressed in early vs. late passage (senescent) human dermal endothelial cells (HDMEC) using cDNA array hybridization. Early passage HDMEC cultured with or without VPF/VEGF overexpressed 9 and underexpressed 6 genes in comparison with their senescent counterparts. Thymosin beta-10 expression was modulated by VPF/VEGF and was strikingly down-regulated in senescent EC. The beta-thymosins are actin G-sequestering peptides that regulate actin dynamics and are overexpressed in neoplastic transformation. We have also identified senescent EC in the human aorta at sites overlying atherosclerotic plaques. These EC expressed senescence-associated neutral beta-galactosidase and, in contrast to adventitial microvessel endothelium, exhibited weak staining for thymosin beta-10. ISH performed on human malignant tumors revealed strong thymosin beta-10 expression in tumor blood vessels. This is the first report that Tbeta-10 expression is significantly reduced in senescent EC, that VPF/VEGF modulates thymosin beta-10 expression, and that EC can become senescent in vivo. The reduced expression of thymosin beta-10 may contribute to the senescent phenotype by reducing EC plasticity and thus impairing their response to migratory stimuli.

The epithelial anion channel CFTR interacts with multiple PDZ domain-containing proteins. Heterologous expression studies have demonstrated that the Na + /H + exchanger regulatory factors, NHERF1, NHERF2, and PDZK1 (NHERF3), modulate CFTR membrane retention, conductivity, and interactions with other transporters. To study their biological roles in vivo, we investigated CFTR-dependent duodenal HCO 3 -secretion in mouse models of Nherf1, Nherf2, and Pdzk1 loss of function. We found that Nherf1 ablation strongly reduced basal as well as forskolin-stimulated (FSK-stimulated) HCO 3 -secretory rates and blocked β 2 -adrenergic receptor (β 2 -AR) stimulation. Conversely, Nherf2 -/-mice displayed augmented FSK-stimulated HCO 3 -secretion. Furthermore, although lysophosphatidic acid (LPA) inhibited FSK-stimulated HCO 3 -secretion in WT mice, this effect was lost in Nherf2 -/-mice. Pdzk1 ablation reduced basal, but not FSK-stimulated, HCO 3 -secretion. In addition, laser microdissection and quantitative PCR revealed that the β 2 -AR and the type 2 LPA receptor were expressed together with CFTR in duodenal crypts and that colocalization of the β 2 -AR and CFTR was reduced in the Nherf1 -/-mice. These data suggest that the NHERF proteins differentially modulate duodenal HCO 3 -secretion: while NHERF1 is an obligatory linker for β 2 -AR stimulation of CFTR, NHERF2 confers inhibitory signals by coupling the LPA receptor to CFTR.

No abstract