The importance of the EGF receptor (EGFR) signaling pathway in the development and progression of nonsmall cell lung carcinomas (NSCLC) is widely recognized. Gene sequencing studies revealed that a majority of tumors responding to EGFR kinase inhibitors harbor activating mutations in the EGFR kinase domain. This underscores the need for novel biomarkers and diagnostic imaging approaches to identify patients who may benefit from particular therapeutic agents and approaches with improved efficacy and safety profiles. To this goal, we developed 4-[(3-iodophenyl)amino]-7-{2-[2-{2-(2-[2-{2-([ 18 F]fluoroethoxy)-ethoxy}-ethoxy]-ethoxy)-ethoxy}-ethoxy]-quinazoline-6-yl-acrylamide ([ 18 F]F-PEG6-IPQA), a radiotracer with increased selectivity and irreversible binding to the active mutant L858R EGFR kinase. We show that PET with [ 18 F]F-PEG6-IPQA in tumor-bearing mice discriminates H3255 NSCLC xenografts expressing L858R mutant EGFR from H441 and PC14 xenografts expressing EGFR or H1975 xenografts with L858R/T790M dual mutation in EGFR kinase domain, which confers resistance to EGFR inhibitors (i.e., gefitinib). The T790M mutation precludes the [ 18 F]F-PEG6-IPQA from irreversible binding to EGFR. These results suggest that PET with [ 18 F]F-PEG6-IPQA could be used for the selection of NSCLC patients for individualized therapy with small molecular inhibitors of EGFR kinase that are currently used in the clinic and have a similar structure (i.e., iressa, gefitinib, and erlotinib).

Epigenetic modifications mediated by histone deacetylases (HDACs) play important roles in the mechanisms of different neurologic diseases and HDAC inhibitors (HDACIs) have shown promise in therapy. However, pharmacodynamic profiles of many HDACIs in the brain remain largely unknown due to the lack of validated methods for noninvasive imaging of HDACs expression-activity. In this study, dynamic PET/CT imaging was performed in 4 rhesus macaques using [18F]FAHA, a novel HDAC substrate, and [18F]fluoroacetate, the major radio-metabolite of [18F]FAHA, and fused with corresponding MR images of the brain. Quantification of [18F]FAHA accumulation in the brain was performed using a customized dual-tracer pharmacokinetic model. Immunohistochemical analyses of brain tissue revealed the heterogeneity of expression of individual HDACs in different brain structures and cell types and confirmed that PET/CT/MRI with [18F]FAHA reflects the level of expression-activity of HDAC class IIa enzymes. Furthermore, PET/CT/MRI with [18F]FAHA enabled non-invasive, quantitative assessment of pharmacodynamics of HDACs inhibitor SAHA in the brain.

Expression of the K1 gene of human herpesvirus 8 activates nuclear factor-B and induces lymph node hyperplasia and lymphomas in transgenic mice. To further delineate its role in cell survival, we determined whether K1 altered apoptosis of lymphoma cells. K1 protein is expressed in Kaposi sarcoma and primary effusion lymphoma. We retrovirally transfected BJAB lymphoma, THP-1, U937, and Kaposi sarcoma SLK cells to express K1 and a K1 mutant with the deleted immunoreceptor tyrosinebased activation motif (K1m). We challenged cells with an agonistic anti-Fas antibody, Fas ligand, irradiation, and tumor necrosis factor-related apoptosis-inducing ligand. K1 transfectants but not K1m transfectants exhibited reduced levels of apoptosis induced by the anti-Fas antibody but not apoptosis induced by the tumor necrosis factorrelated apoptosis-inducing ligand or irradiation. K1 expression resulted in reduced apoptosis rates as shown in several assays. K1 induced a modest reduction in levels of Fas-associated death domain protein, and procaspase 8 recruited to the death-inducing signaling complex. Finally, K1 transfectants cleaved procaspase 8 at significantly lower rates than did K1m transfectants. IntroductionHuman herpesvirus 8 (HHV-8) has a pathogenic role in primary effusion lymphoma (PEL), Kaposi sarcoma (KS), and perhaps some cases of Castleman disease. 1,2 One HHV-8 gene with transforming properties is K1. This gene is positionally homologous with transforming genes of Epstein-Barr virus. Indeed, K1 has transforming activity in rodent cells and in marmosets after K1 functionally replaces the STP gene in the herpesvirus saimiri genome. 3 Ubiquitous expression of K1 in transgenic mice induces lymphoproliferation, splenomegaly, and lymphomas. 4 Furthermore, K1 expression in mice induces signaling of nuclear factor-B activation, which is associated with enhanced vascular endothelial growth factor expression and downregulated interleukin-12 expression. Lymphocytes in K1 transgenic mice exhibit abnormal proliferation in response to antigens. Additionally, K1 expression induces activation-associated cytokine dysregulation, and the immunoreceptor tyrosine-based activation motif (ITAM) of K1 is constitutively phosphorylated, resulting in constitutive signaling. [3][4][5][6] Finally, K1 stimulates Lyn tyrosine kinase activity in lymphocytes and lymphoma cells of K1 transgenic mice in an ITAM-dependent manner. In other models, ITAM signaling activates Lyn and ZAP70 by binding these kinases and activating the ITAM. [7][8][9] Investigators have observed K1 expression in cases of Castleman disease and PEL. K1 RNA is present in PEL tissues and in PEL cell lines that can be up-regulated after treatment of cells with phorbol esters. 6,10 Some KS cells express K1 RNA in the absence of lytic gene Orf26 expression. 11 K1 is expressed in chronically infected cells and is up-regulated when cells enter the lytic phase of the virus life cycle. 10,12,13 Further characterization of K1 protein in tissues has been limited because of its highly v...

The long-term fate of stem cells after intramyocardial delivery is unknown. We used noninvasive, repetitive PET/CT imaging with [18F]FEAU to monitor the long-term (up to 5 months) spatial-temporal dynamics of MSCs retrovirally transduced with the sr39HSV1-tk gene (sr39HSV1-tk-MSC) and implanted intramyocardially in pigs with induced acute myocardial infarction. Repetitive [18F]FEAU PET/CT revealed a biphasic pattern of sr39HSV1-tk-MSC dynamics; cell proliferation peaked at 33–35 days after injection, in periinfarct regions and the major cardiac lymphatic vessels and lymph nodes. The sr39HSV1-tk-MSC–associated [18F]FEAU signals gradually decreased thereafter. Cardiac lymphography studies using PG-Gd-NIRF813 contrast for MRI and near-infrared fluorescence imaging showed rapid clearance of the contrast from the site of intramyocardial injection through the subepicardial lymphatic network into the lymphatic vessels and periaortic lymph nodes. Immunohistochemical analysis of cardiac tissue obtained at 35 and 150 days demonstrated several types of sr39HSV1-tk expressing cells, including fibro-myoblasts, lymphovascular cells, and microvascular and arterial endothelium. In summary, this study demonstrated the feasibility and sensitivity of [18F]FEAU PET/CT imaging for long-term, in-vivo monitoring (up to 5 months) of the fate of intramyocardially injected sr39HSV1-tk-MSC cells. Intramyocardially transplanted MSCs appear to integrate into the lymphatic endothelium and may help improve myocardial lymphatic system function after MI.

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