Studies of low basal Jun N-terminal kinase (JNK) activity in non-stressed cells led us to identify a JNK inhibitor that was purified and identified as glutathione S-transferase

Many of these human cell lines have been widely used in the thyroid cancer field for the past 20 yr and are not only redundant, but not of thyroid origin. These results emphasize the importance of cell line integrity, and provide the short tandem repeat profiles for a panel of thyroid cancer cell lines that can be used as a reference for comparison of cell lines from other laboratories.

Nanoparticle-based materials, such as drug delivery vehicles and diagnostic probes, currently under evaluation in oncology clinical trials are largely not tumor selective. To be clinically successful, the next generation of nanoparticle agents should be tumor selective, nontoxic, and exhibit favorable targeting and clearance profiles. Developing probes meeting these criteria is challenging, requiring comprehensive in vivo evaluations. Here, we describe our full characterization of an approximately 7-nm diameter multimodal silica nanoparticle, exhibiting what we believe to be a unique combination of structural, optical, and biological properties. This ultrasmall cancer-selective silica particle was recently approved for a first-in-human clinical trial. Optimized for efficient renal clearance, it concurrently achieved specific tumor targeting. Dye-encapsulating particles, surface functionalized with cyclic arginine-glycine-aspartic acid peptide ligands and radioiodine, exhibited high-affinity/avidity binding, favorable tumor-to-blood residence time ratios, and enhanced tumor-selective accumulation in α v β 3 integrin-expressing melanoma xenografts in mice. Further, the sensitive, real-time detection and imaging of lymphatic drainage patterns, particle clearance rates, nodal metastases, and differential tumor burden in a large-animal model of melanoma highlighted the distinct potential advantage of this multimodal platform for staging metastatic disease in the clinical setting.

Sprouty was genetically identified as an antagonist of fibroblast growth factor signaling during tracheal branching in Drosophila. In this study, we provide a functional characterization of mammalian Sprouty1 and Sprouty2. Sprouty1 and Sprouty2 inhibited events downstream of multiple receptor tyrosine kinases and regulated both cell proliferation and differentiation. Using NIH3T3 cell lines conditionally expressing Sprouty1 or Sprouty2, we found that these proteins specifically inhibit the Ras/Raf/MAP kinase pathway by preventing Ras activation. In contrast, activation of the phosphatidylinositol 3-kinase pathway was not affected by Sprouty1 or Sprouty2. We further showed that Sprouty1 and Sprouty2 do no prevent the formation of a SNT⅐Grb2⅐Sos complex upon fibroblast growth factor stimulation, yet block Ras activation. Taken together, these results establish mammalian Sprouty proteins as important negative regulators of growth factor signaling and suggest that Sprouty proteins act downstream of the Grb2⅐Sos complex to selectively uncouple growth factor signals from Ras activation and the MAP Kinase pathway.Normal development requires precise spatial and temporal regulation of signal transduction pathways involved in cell growth and differentiation. Negative control of growth factor response is achieved both by restriction of the incoming signal itself and induction of counter regulatory mechanisms affecting the propagation of the signal. The expression of many inhibitors are induced by the pathway they eventually antagonize, providing the potential for a tight autoregulation (for a review, see Ref. 1). Recently, sprouty (spry) was identified by genetic studies as such an inhibitor (2).Spry was originally described as an antagonist of Breathless FGF 1 receptor signaling during tracheal branching in Drosophila Loss of function mutations of spry led to excessive FGF signaling and ectopic branching, whereas engineered overexpression of spry blocked the branching (2). As other groups reported genetic interactions between spry and several different receptor tyrosine kinases (RTK) in multiple contexts, it became clear that spry was a general inhibitor of RTK signaling during Drosophila development (3-6). Through a data base search, three human genes were identified with sequence similarity to Drosophila spry (2) and a fourth family member was described in the mouse (7). Mammalian spry genes are expressed in highly restricted patterns in the embryo during early development and in many adult tissues (7-9). In most tissues, the different family members appear to be co-regulated and their expression shows a close correlation with known sites of FGF signaling. Mammalian Spry proteins may be key regulators of several developmental processes, including lung branching morphogenesis, midbrain and anterior hindbrain patterning, and limb chondrocyte differentiation (8 -10).Genetic and biochemical analysis performed by Casci et al. (3) suggested that Drosophila Spry negatively regulates the Ras pathway, but the molecular mechani...

Breast cancer 1, early onset (BRCA1) expression is often reduced in sporadic breast tumors, even in the absence of BRCA1 genetic modifications, but the molecular basis for this is unknown. In this study, we identified homeobox A9 (HOXA9) as a gene frequently downregulated in human breast cancers and tumor cell lines and noted that reduced HOXA9 transcript levels associated with tumor aggression, metastasis, and patient mortality. Experiments revealed that loss of HOXA9 promoted mammary epithelial cell growth and survival and perturbed tissue morphogenesis. Restoring HOXA9 expression repressed growth and survival and inhibited the malignant phenotype of breast cancer cells in culture and in a xenograft mouse model. Molecular studies showed that HOXA9 restricted breast tumor behavior by directly modulating the expression of BRCA1. Indeed, ectopic expression of wild-type BRCA1 phenocopied the tumor suppressor function of HOXA9, and reducing BRCA1 levels or function inhibited the antitumor activity of HOXA9. Consistently, HOXA9 expression correlated with BRCA1 in clinical specimens and with tumor aggression in patients lacking estrogen receptor/progesterone receptor expression in their breast tissue. These findings indicate that HOXA9 restricts breast tumor aggression by modulating expression of the tumor suppressor gene BRCA1, which we believe provides an explanation for the loss of BRCA1 expression in sporadic breast tumors in the absence of BRCA1 genetic modifications.