The naevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple developmental defects and cancer susceptibility, in particular to basal cell carcinomas (BCCs). Medulloblastomas, primitive neuroectodermal tumours (PNETs) arising in childhood, occur in about 3 ± 5% of NBCCS patients and a subset of PNETs was previously found with allelic imbalance at 9q22-q23, the region containing the gene for NBCCS (PTCH). We have analysed tumour DNA samples from 37 unrelated patients with sporadic PNETs and ®ve medulloblastoma cell lines for PTCH mutations using an exon-by-exon single strand conformation polymorphism assay. We found three missense mutations, which aect conserved residues in transmembrane domains of the gene product and in the extracellular loop implicated in binding sonic hedgehog, one 2 bp deletion and an exon skipping splice site mutation. Most mutations were associated with the absence of the wild-type allele and were found in tumours exhibiting loss of heterozygosity (LOH) at locī anking PTCH. The ®nding of LOH at 9q22-q23 in most mutated tumours while present in only three out of 26 tumours, in which a mutation was not identi®ed, implicates PTCH as the target gene in PNETs with LOH at 9q22-q23 and de®cient PTCH in the development of a subset of these tumours. Since all observed mutations were absent in the germ-line, a sporadic medulloblastoma developing as the ®rst symptom of NBCCS is likely to be a very uncommon event.

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Mutations in the TP53 tumor suppressor gene have been studied in different types of brain tumors. Little is known about this genetic event in human meningioma, a mostly benign tumor. To investigate the frequency of TP53 gene mutations in human tumors derived from meningeal tissues, paraffin-embedded tissues from 30 cases (including 2 malignant and 4 atypical meningiomas, as well as 2 hemangioblastomas and 3 hemangiopericytomas) were screened by immunohistochemistry. Polymerase chain reaction/single strand conformational polymorphism (PCR/SSCP) and direct DNA sequencing were thereafter performed in selected cases. Nuclear p53 staining was not seen in any of the 19 benign meningiomas tested, while atypical meningiomas, hemangioblastomas, and hemangiopericytomas displayed nuclear staining in a subpopulation of tumor cells in 4 out of 5, 2 out of 2, and 3 out of 3 cases, respectively. One malignant meningioma showed an intense nuclear staining and a band shift in SSCP. In this case, we identified a mutation in the TP53 gene at codon 161 changing GCC to ACC and resulting in an alteration of alanine to threonine in this position. Our results indicate that TP53 gene mutation may be considered as a marker for malignant transformation in meningioma. p53 immunoreactivity, even in the absence of detectable gene mutation, is also associated with atypia and does not appear in regular benign meningiomas.

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XTENs are unstructured, nonrepetitive protein polymers designed to prolong the in vivo half-life of pharmaceuticals by introducing a bulking effect similar to that of poly(ethylene glycol). While XTEN can be expressed as a recombinant fusion protein with bioactive proteins and peptides, therapeutic molecules of interest can also be chemically conjugated to XTEN. Such an approach permits precise control over the positioning, spacing, and valency of bioactive moieties along the length of XTEN. We have demonstrated the attachment of T-20, an anti-retroviral peptide indicated for the treatment of HIV-1 patients with multidrug resistance, to XTEN. By reacting maleimide-functionalized T-20 with cysteine-containing XTENs and varying the number and positioning of cysteines in the XTENs, a library of different peptide–polymer combinations were produced. The T-20-XTEN conjugates were tested using an in vitro antiviral assay and were found to be effective in inhibiting HIV-1 entry and preventing cell death, with the copy number and spacing of the T-20 peptides influencing antiviral activity. The peptide–XTEN conjugates were also discovered to have enhanced solubilities in comparison with the native T-20 peptide. The pharmacokinetic profile of the most active T-20-XTEN conjugate was measured in rats, and it was found to exhibit an elimination half-life of 55.7 ± 17.7 h, almost 20 times longer than the reported half-life for T-20 dosed in rats. As the conjugation of T-20 to XTEN greatly improved the in vivo half-life and solubility of the peptide, the XTEN platform has been demonstrated to be a versatile tool for improving the properties of drugs and enabling the development of a class of next-generation therapeutics.