The oncogenic properties of EWS/WT1 of desmoplastic small round cell tumors are unmasked by loss of p53 in murine embryonic fibroblasts.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is characterized by the presence of a fusion protein EWS/WT1, arising from the t (11;22) (p13;q12) translocation. Here we examine the oncogenic properties of two splice variants of EWS/WT1, EWS/WT1-KTS and EWS/WT1 + KTS. METHODS: We over-expressed both EWS/WT1 variants in murine embryonic fibroblasts (MEFs) of wild-type, p53+/- and p53-/- backgrounds and measured effects on cell-proliferation, anchorage-independent growth, clonogenicity after serum withdrawal, and sensitivity to cytotoxic drugs and gamma irradiation in comparison to control cells. We examined gene expression profiles in cells expressing EWS/WT1. Finally we validated our key findings in a small series of DSRCT. RESULTS: Neither isoform of EWS/WT1 was sufficient to transform wild-type MEFs however the oncogenic potential of both was unmasked by p53 loss. Expression of EWS/WT1 in MEFs lacking at least one allele of p53 enhanced cell-proliferation, clonogenic survival and anchorage-independent growth. EWS/WT1 expression in wild-type MEFs conferred resistance to cell-cycle arrest after irradiation and daunorubicin induced apoptosis. We show DSRCT commonly have nuclear localization of p53, and copy-number amplification of MDM2/MDMX. Expression of either isoform of EWS/WT1 induced characteristic mRNA expression profiles. Gene-set enrichment analysis demonstrated enrichment of WNT pathway signatures in MEFs expressing EWS/WT1 + KTS. Wnt-activation was validated in cell lines with over-expression of EWS/WT1 and in DSRCT. CONCLUSION: In conclusion, we show both isoforms of EWS/WT1 have oncogenic potential in MEFs with loss of p53. In addition we provide the first link between EWS/WT1 and Wnt-pathway signaling. These data provide novel insights into the function of the EWS/WT1 fusion protein which characterize DSRCT.

A phase I study of panobinostat in pediatric patients with refractory solid tumors, including CNS tumors.

PURPOSE: This was an open label, phase I (3 + 3 design), multi-centre study evaluating panobinostat in pediatric patients with refractory solid tumors. METHODS: Primary endpoints were to establish MTD, define and describe associated toxicities, including dose limiting toxicities (DLT) and to characterize its pharmacokinetics (PK). Secondary endpoints included assessing the anti-tumour activity of panobinostat, and its biologic activity, by measuring acetylation of histones in peripheral blood mononuclear cells. RESULTS: Nine patients were enrolled and treated with intravenous panobinostat at a dosing level of 15 mg/m2 which was tolerated. Six were evaluable for adverse events. Two (33%) patients experienced Grade 3-4 thrombocytopenia, 1 (17%) experienced Grade 3 anemia, and 2 (33%) experienced Grade 3 neutropenia. Grade 4 drug related pain occurred in 2 (33%) of the patients studied. Two (33%) patients experienced a Grade 2 QTcF change (0.478 ± 0.006 ms). One cardiac DLT (T wave changes) was reported. PK values for 15 mg/m2 (n = 9) dosing were: Tmax 0.8 h, Cmax 235.2 ng/mL, AUC0-t 346.8 h ng/mL and t1/2 7.3 h. Panobinostat significantly induced acetylation of histone H3 and H4 at all time points measured when compared to pre-treatment samples (p < 0.05). Pooled quantitative Western blot data confirmed that panobinostat significantly induced acetylation of histone H4 at 6 h (p < 0.01), 24 h (p < 0.01) and 28-70 h (p < 0.01) post dose. CONCLUSION: A significant biological effect of panobinostat, measured by acetylation status of histone H3 and H4, was achieved at a dose of 15 mg/m2. PK data and drug tolerability at 15 mg/m2 was similar to that previously published.

Methods for the analysis of histone H3 and H4 acetylation in blood.

LBH589 is one of the many histone deacetylase inhibitors (HDACi) that are currently in clinical trial. Despite their wide-spread use, there is little literature available describing the typical levels of histone acetylation in untreated peripheral blood, the treatment and storage of samples to retain optimal measurement of histone acetylation nor methods by which histone acetylation analysis may be monitored and measured during the course of a patient's treatment. In this study, we have used cord or peripheral blood as a source of human leukocytes, performed a comparative analysis of sample processing methods and developed a flow cytometric method suitable for monitoring histone acetylation in isolated lymphocytes and liquid tumors. Western blotting and immunohistochemistry techniques have also been addressed. We have tested these methods on blood samples collected from four patients treated with LBH589 as part of an Australian Children's Cancer Clinical Trial (CLBH589AAU03T) and show comparable results when comparing in vitro and in vivo data. This paper does not seek to correlate histone acetylation levels in peripheral blood with clinical outcome but describes methods of analysis that will be of interest to clinicians and scientists monitoring the effects of HDACi on histone acetylation in blood samples in clinical trials or in related research studies.

Alport retinopathy results from "severe" COL4A5 mutations and predicts early renal failure.

BACKGROUND AND OBJECTIVES: Previous studies of X-linked Alport syndrome demonstrated that "severe" COL4A5 mutations (large deletions and rearrangements, nonsense and frame-shift mutations, and glycine substitutions in the carboxy-terminal residues) were associated with early-onset renal failure, hearing loss, and lenticonus in affected male patients. This study examined whether severe mutations also resulted in the typical perimacular dot-and-fleck retinopathy. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Twenty unrelated families with X-linked Alport syndrome were studied for the causative mutation in the COL4A5 gene. Nineteen affected male and 22 affected female individuals aged at least 14 yr from these families were examined for clinical and, in particular, ophthalmologic features. RESULTS: Nineteen pathogenic mutations were identified in the COL4A5 gene in the 20 families using a thermal melt analyzer (HRM RotorGene 6000; Corbett) or direct sequencing of hair root or skin fibroblast cDNA. Fifteen mutations were classified severe and four as moderate. Severe mutations were associated with the central dot-and-fleck Alport retinopathy in male individuals (P = 0.0256) in addition to early-onset renal failure, hearing loss, and lenticonus (P = 0.0009, 0.009, and 0.009, respectively). Severe mutations did not correlate with clinical features in female individuals. CONCLUSIONS: Severe mutations in male individuals with X-linked Alport syndrome are associated with the perimacular dot-and-fleck retinopathy. Furthermore, the retinopathy indicates that male individuals are at increased risk for renal failure before the age of 30 (P = 0.0007).

The R229Q mutation in NPHS2 may predispose to proteinuria in thin-basement-membrane nephropathy.

Thin-basement-membrane nephropathy (TBMN) is characterized by persistent dysmorphic hematuria, and the presence of proteinuria is a risk factor for renal impairment. TBMN is often due to mutations in the COL4A3 and COL4A4 genes, and this study determined whether additional mutations in genes encoding other structures in the glomerular filtration barrier contributed to the development of proteinuria. Fifty-six unrelated individuals with TBMN including 18 (32%) with proteinuria > or = 300 mg/L and ten (18%) with proteinuria > or = 500 mg/L were studied. Deoxyribonucleic acid (DNA) was screened for NPHS2 mutations and variants (R138Q and P375L) using single-stranded conformational analysis (SSCA) and for the R229Q mutation by sequencing. DNA was also screened for ACTN4 mutations. R229Q was more common in patients with TBMN and proteinuria > or = 500 mg/L (p < 0.05), and a possible NPHS2 mutation (671G>A, R224H) was identified in one patient with proteinuria 700 mg/L. No other NPHS2 variants correlated with proteinuria, and no ACTN4 mutations were found. Individuals with TBMN and R229Q are carriers of the autosomal recessive forms of both Alport syndrome and familial focal segmental glomerulosclerosis (FSGS). The early demonstration of R229Q in individuals with TBMN may indicate those at increased risk of proteinuria and renal impairment.