Retinoblastoma Solutions, University Health Network, Toronto, Ontario, Canada.

We have analyzed RNA from retinoblastoma patients and unaffected carriers with various RB1 gene mutations to determine the patterns of missplicing and associations with phenotypic expression. Most sequence alterations in or in the neighborhood of conserved splice signals that we tested resulted in simple exon skipping (15 mutations) or intron inclusion (new acceptor AG-sites, four mutations) as expected. Two mutations resulted in skipping of a neighboring exon (exon 11), a complex pattern indicating competition for correct lariat formation. We observed no activation of a cryptic splice site but found that a recurrent missense mutation in exon 7 creates a new splice site (two families). RT-PCR analysis enabled us to confirm the presence and to characterize the transcriptional consequences of gross insertions and deletions in the RB1 gene in six patients, including two patients with mutational mosaicism. We also used RT-PCR analysis to search for unknown mutations in 15 patients and identified three oncogenic point mutations deep in introns. Two of these mutations are recurrent thus indicating that, despite the vast extent of the introns of the RB1 gene, few bases are effective targets for oncogenic mutations. When analyzing associations between phenotypic expression (16 families) and mutational consequences we observed no link to the presence or absence of a premature termination codon in the mutant transcript. However, the location of a mutation relative to the splice sequence has a strong and consistent influence on phenotypic expression. Copyright 2008 Wiley-Liss, Inc.

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Unità Operativa di Ematologia Medicine, Cosenza, Italy.

INTRODUCTION: The fusion protein between the platelet-derived growth factor receptor alpha (PDGFRalpha, P) gene and the Fip1-like1 (FIP1L1, F) may be identified in 14 to 60% of HES and it indicates a clonal hypereosinophilic syndrome called F/P-positive CEL. We herein report a case of F/P-positive CEL with retro-orbital localization, who was successfully treated with imatinib. CASE REPORT: A 53-year-old male presented an absolute eosinophil count of 25,000/mm(3), anemia (Hb 10.2 g/dl) and a moderate increase in the platelet count (571,000/mm(3)). A clinical examination revealed left exophthalm, associated with diffuse hypoesthesia and diplopia. A CT scan of orbits showed a lesion located in the lachrymal fossa of the left orbit with intra- and extra-conical extension. Molecular analysis excluded the presence of bcr/abl transcript while a F/P fusion tyrosine kinase signal was documented. Imatinib mesylate (IM) was started and, after 7 days of treatment eosinophil count significantly declined along with a dramatic reduction of the left exophthalm. IM dosage was increased up to 300 mg/day. The drug was well tolerated with an initial modest haematological toxicity. The left exophthalm, as well as hypoesthesia and diplopia, disappeared after IM therapy. MRI showed a clear reduction of the intra- and extra-conical growth process. BM molecular signal of the F/P fusion gene resulted undetectable after 4 weeks of treatment. CONCLUSION: In our case, the diagnosis of FIPIL1-PDGFRA-positive CEL and IM therapy has allowed the patient to experience an excellent clinical therapeutic result, avoiding surgical treatment of the retro-orbital mass.

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Department of Neurosurgery, Nagoya University School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan.

PURPOSE: Methylation of the O(6)-methyguanine-DNA methyltransferase (MGMT) gene promoter in gliomas has been reported to be a useful predictor of the responsiveness to temozolomide (TMZ). In our previous experiments, we observed that IFN-beta sensitized TMZ-resistant glioma cells with the unmethylated MGMT promoter and that the mechanism of action was possibly due to attenuation of MGMT expression via induction of TP53. In this study, (1) we explored the synergistic effect of IFN-beta and TMZ in the animal model, and (2) clarified the role of IFN-beta induced TP53 in the human MGMT promoter. METHODS: (1) Nude mice with either subcutaneous T98 (TMZ-resistant) or U251SP (TMZ-sensitive) tumor were treated with IFN-beta/TMZ for 5 consecutive days. (2) The MGMT promoter activity was assayed by a luciferase reporter system in Saos2 (p53-null) cells transduced with a p53-adenoviral vector, and T98 glioma cells treated with IFN-beta. RESULTS: (1) A combination of IFN-beta/TMZ had significant synergistic antitumor activity on the growth of both T98 and U251SP tumors. (2) MGMT promoter activity was suppressed by either adenovirally transduced p53 or IFN-beta. CONCLUSIONS: It would be appealing to consider a prospective clinical trial in which genetic markers are used for personalized drug selection, eliciting other forms of treatment or inhibition of MGMT for those with MGMT expression. In this context, IFN-beta inactivates MGMT via p53 gene induction and enhances the therapeutic efficacy to TMZ.

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Department of Molecular and Medical Genetics, University of Toronto, Toronto, Canada.

The transition from the benign retinal tumor retinoma to its malignant counterpart retinoblastoma is accompanied by the loss of expression of the p75(NTR) neurotrophin receptor. This change in expression is mimicked in the TAg-RB murine model of retinoblastoma, where early tumors retain expression of p75(NTR) and advanced tumors lack it. We sought to determine the functional effect on tumor development of absence of p75(NTR) from the onset of TAg-RB tumor initiation. TAg-RB mice were crossed with either p75(NTR) exon 3 (E3KO) or exon 4 knockout (E4KO) mice to produce TAg-RB offspring that lacked one or both normal p75(NTR) alleles. The average tumor area per eye as a percentage of retinal area was measured. TAg-RB/E3KO (TAg-RB(E3KO)) and heterozygous mice showed no significant difference in tumor area compared to the TAg-RB control mice at any time point studied. However, TAg-RB/E4KO (TAg-RB(E4KO)) and heterozygous mice displayed a significantly larger tumor area than the TAg-RB control mice. Furthermore, adenoviral-mediated expression of p75(NTR) in a p75(NTR)-deficient human retinoblastoma cell line resulted in increased apoptosis. Our results confirm that p75(NTR) suppresses progression of both human and TAg-RB murine retinoblastoma, and holds promise as a target for future therapy of the disease. (c) 2008 Wiley-Liss, Inc.

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The New York Eye Cancer Center, 115 East 61st Street, New York, NY 10065, USA.

AIM: To evaluate 18-fluoro-2-deoxyglucose (FDG) whole-body positron emission tomography/computed radiographic tomography (PET/CT) for lymph node and metastatic staging of patients with conjunctival melanoma. METHODS: Fourteen patients with T3 (n = 13) and T4 (n = 1) conjunctival melanoma (as defined in Chapter 42 of the AJCC staging manual) were staged for metastatic disease with PET/CT imaging with fusion. The patients had lymph node and clinical staging evaluations before PET/CT imaging. PET/CT images were studied for the presence and distribution of metastatic conjunctival melanoma (determined by standardised uptake values) and later confirmed by biopsy. MRI imaging was performed if abnormalities were noted on PET/CT images. RESULTS: Fourteen patients with conjunctival melanoma underwent PET/CT imaging. Seven were newly diagnosed (presurgical screening), and seven had undergone prior treatment (follow-up group). Only one patient with conjunctival melanoma (7.1%) was found to have metastatic disease on PET/CT imaging. Abnormal foci were found in the liver, lung, peritoneal cavity, lumbar spine as well as a supraclavicular node (T4N1M4). All liver function tests were normal. The mean length of follow-up after PET/CT imaging was 13 months (range 4-30 months). CONCLUSIONS: PET/CT imaging did not reveal any regional or systemic metastasis among 14 patients with advanced, diffuse and multifocal disease.

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