Somatic mutations in the BRCA1 gene in Chinese sporadic breast and ovarian cancer.

Inherited mutations in the BRCA1 gene confer increased susceptibility to breast and ovarian cancer. Its role in sporadic carcinogenesis is not well defined. Somatic mutations in breast cancers have not been reported and to date there are only three reports of somatic mutations in sporadic ovarian cancers. To investigate the contribution of BRCA1 mutations to sporadic breast and ovarian cancer in the Chinese population, we analysed 62 samples from Chinese women using the protein truncation test. There were 40 cases of breast cancer under age 50 and 22 cases of ovarian cancer, all unselected for family history. There was no age selection for the ovarian cancers. We found two somatic BRCA1 mutations in exon 11, one in a breast cancer and the other in an ovarian cancer, both of which result in truncated proteins. Our results indicate that somatic BRCA1 mutations, like somatic mutations in the BRCA2 gene, though very rare, can be found in both breast and ovarian cancers and support a tumor suppressor function for BRCA1 in sporadic tumors.

Comparative analysis of Epstein-Barr virus gene polymorphisms in nasal T/NK-cell lymphomas and normal nasal tissues: implications on virus strain selection in malignancy.

Whether particular Epstein-Barr virus (EBV) strains are preferentially selected in malignant diseases remains controversial. Assessment of the importance of strain variation in the pathogenicity of EBV has been hampered principally by the lack of accurate data on the prevalence of virus variants in the normal population. To clarify this issue, a detailed comparative analysis of the EBV genomes contained in normal nasal and nasopharyngeal mucosal tissues and in nasal T/NK-cell lymphoma, which originates at these anatomic sites, was carried out by PCR amplification across the 30-bp deletion and the 33-bp repeat loci in the LMP1 gene and the type-specific polymorphic loci in the EBNA2 and EBNA3C genes and by sequence analysis of the 3' C-terminal region of the LMP1 gene. Whilst the majority of EBV strains in either normal or tumour tissues were type 1 viruses with similar numbers of LMP1 repeats, a marked predominance of LMP1 deletion (del-LMP1) over non-deleted/wild-type LMP1 (wt-LMP1) variants was observed in nasal T/NK-cell lymphoma. Although del-LMP1 variants were also prevalent in the normal carriers of our population, wt-LMP1 was detected at a significantly higher frequency in normal vs. tumour tissues (p = 0.036). More critically, wt-LMP1 variants were found frequently in mixed infection with del-LMP1 variants in the normal carriers. Sequence analysis identified 2 major del-LMP1 (and several wt-LMP1) variants containing signatory nucleotide changes in relation to the prototype B95-8 sequence in both normal and neoplastic nasal tissues. Together, our data provide strong evidence for a selection mechanism for del-LMP1 over the wt-LMP1 variants in tumours.

Comparative biomembrane permeation of tacrine using Yucatan minipigs and domestic pigs as the animal model.

Tacrine (THA), a centrally acting acetylcholine-esterase inhibitor, is presently administered perorally for the treatment of Alzheimer's disease (AD). However, its low bioavailablity (i.e., 17%) and short half-life (2-4 h) demand the search for alternative routes of administration. The primary objective of this study was to assess the potential of absorptive mucosae and skin as routes for improving the systemic delivery of THA. The Yucatan minipig, which has been used increasingly in biomedical research as a useful model for humans, and the domestic pig, which is available at low cost, were evaluated for their suitability as animal model. Permeation kinetics of THA across various absorptive mucosae (nasal, buccal, sublingual, and rectal) of both species of swine were studied in the hydrodynamically well-calibrated Valia-Chien permeation cells. For comparison, permeation through various intestinal segments (duodenum, jejunum, and ileum) was also measured. Results indicated that both species display similar permeation characteristics. However, the data obtained for the domestic pigs shows lower intra- and inter-animal variabilities than that of the Yucatan minipigs. The nasal mucosa was found to have the highest permeability, while the buccal mucosa had the lowest among the absorptive mucosae. The intrinsic permeabilities and diffusivity of THA across the four absorptive mucosae were not significantly different between species but lower than that for the intestinal segments for both species. Using dorsal skin as the model, the skin permeation of THA was also investigated and the results indicated that the domestic swine has a significantly higher skin permeability than the Yucatan minipig, with more than a 2-fold difference in intrinsic permeabilities. The intrinsic permeability, partition coefficient, and diffusivity for domestic pig skin are very similar to that for human cadaver skin. Considering the potential of bypassing the hepatic "first-pass" elimination, the absorptive mucosae may be useful routes for systemic delivery of THA to achieve improved bioavailability. With additional advantages of lower variability, ease of membrane excision, good accessibility, and lower cost, it is concluded that the domestic swine is a better animal model than the Yucatan minipig for preclinical studies on the systemic delivery of tacrine.

Presence of strA-strB gene within a streptomycin-resistance operon in a clinical isolate of Shigella flexneri.

Three aminoglycoside-modifying enzymes (AMEs) were produced by a clinical isolate of Shigella flexneri which was resistant to gentamicin, tobramycin, netilmicin, kanamycin, sisomicin and streptomycin: acetyltransferase (AAC) (3)-II-type, and phosphotransferase (APH) (3")- and (6)-type enzymes. The aminoglycoside-resistance genes were located on a 75-Kb plasmid. Two genes, strA-HK and strB-HK, in a transcriptional unit were found to code for streptomycin-resistance. The genetic organization and sequence of this transcriptional unit were identical to those of strA and strB in plasmid RSF1010. strA-HK and strB-HK when expressed separately produced functional enzymes. Our substrate profile study on the crude extracts of StrA-HK and StrB-HK proteins confirmed that StrA-HK was an APH(3")-type and showed that StrB-HK was a member of the APH(6) family.