No abstract

CM, Langston JW (1998a) Absence of mutations in the coding region of the alpha-synuclein gene in pathologically proven Parkinson's disease. Neurology 50:1136-1137 Chan P, Tanner CM, Jiang X, Langston JW (1998b) Failure to find the alpha-synuclein gene missense mutation (G209A) in 100 patients with younger onset Parkinson's disease. Neurology 50:513-514 Letters to the Editor

Hsp90 is an evolutionarily conserved and ubiquitously expressed molecular chaperone that mainly modulates, along with a group of co-chaperones, the general platform of protein folding and prevents the nonspecific aggregation of misfolded or unfolded proteins. In the voluminous Hsp90 clientele, a large variety of important regulatory proteins can be identified, including many whose deregulation may lead to cancer initiation and progression, such as the oncogenic clients pp60(v-src), Bcr-Abl, mutated p53, ErbB2 (Her-2), Akt, Flt3, HIF-1alpha and B-Raf. Therefore, inhibition of Hsp90 function offers the prospect of simultaneously disrupting multiple signaling pathways directly implicated in the development of malignant phenotypes. During the last few years, there has been a major focus on the development of Hsp90 specific inhibitors. This started with the discovery that certain natural products could specifically disrupt Hsp90 chaperone activities. The benzoquinone ansamycin antibiotic geldanamycin and its less toxic derivative 17-AAG have been shown to possess strong anti-proliferative and apoptotic activity in cancer cells, whereas 17-AAG has demonstrated potent anti-tumor activity in several human xenograft models, including breast, prostate and colon cancer. In an effort to overcome difficulties with drug toxicity and solubility, a number of novel bioengineered 17-AAG analogues, such as 17-DMAG and IPI-504, and small-molecule inhibitors, including purine and pyrazole derivatives, have emerged from rational drug design followed by high-throughput screening approaches. 17-AAG was the leader inhibitor to enter and successfully complete phase I clinical trials, thus demonstrating that Hsp90 constitutes a valid drug target for cancer therapy. This review includes information on the current model of ternary interactions between Hsp90, client proteins and a vast array of co-chaperones followed by a list of characteristic inhibitors and ongoing clinical trials reported thus far.

In the search for a tumour suppressor gene in the 3p21.3 region we isolated two genes, RBM5 and RBM6. Gene RBM5 maps to the region which is homozygously deleted in the small cell lung cancer cell line GLC20; RBM6 crosses the telomeric breakpoint of this deletion. Sequence comparison revealed that at the amino acid level both genes show 30% identity. They contain two zinc finger motifs, a bipartite nuclear signal and two RNA binding motifs, suggesting that the proteins for which RBM5 and RBM6 are coding have a DNA/RNA binding function and are located in the nucleus. Northern and Southern analysis did not reveal any abnormalities. By SSCP analysis of 16 lung cancer cell lines we found only in RBM5 a single presumably neutral mutation. By RT-PCR we demonstrated the existence of two alternative splice variants of RBM6, one including and one excluding exon 5, in both normal lung tissue and lung cancer cell lines. Exclusion of exon 5 results in a frameshift which would cause a truncated protein of 520 amino acids instead of 1123 amino acids. In normal lung tissue, the relative amount of the shorter transcript was much greater than that in the lung tumour cell lines, which raises the question whether some tumour suppressor function may be attributed to the derived shorter protein.

Genetic testing for cancer predisposition leads to the identification of a number of variants with uncertain significance. To some extent, variants of BRCA1/2 have been classified, in contrast to variants of other genes. CHEK2 is a typical example, in which a large number of variants of unknown clinical significance were identified and still remained unclassified. Herein, the CHEK2 variant assessment was performed through an in vivo, yeast-based, functional assay. In total, 120 germline CHEK2 missense variants, distributed along the protein sequence, and two large in-frame deletions were tested, originating from genetic test results in breast cancer families, or selected from the ClinVar database. Of these, 32 missense and two in-frame deletions behaved as non-functional, 73 as functional, and 15 as semi-functional, after comparing growth rates of each strain with positive and negative controls. The majority of non-functional variants were localized in the CHK2 kinase and forkheadassociated domains. In vivo results from the non-functional variants were in agreement with in silico predictions, and, where available, with strong breast cancer family history, to a great extent. The results of the largest, to date, yeast-based assay, evaluating CHEK2 variants, can complement and assist in the classification of rare CHEK2 variants with unclear clinical significance. K E Y W O R D S breast cancer, CHEK2 variants, functional assay, yeast Human Mutation. 2019;40:631-648.wileyonlinelibrary.com/journal/humu