Aggregated b-amyloid (Ab) peptides are neurotoxic and cause neuronal death both in vitro and in vivo. Although the formation of a b-sheet structure is usual required to form aggregates, the relationship between neurotoxicity and the Ab sequence remains unclear. To explore the correlation between Ab sequence, secondary structure, aggregative ability, and neurotoxicity, we utilized both full-length and fragment-truncated Ab peptides. Using a combination of spectroscopic and cellular techniques, we demonstrated that neurotoxicity and aggregative ability are correlated while the relationship between these characteristics and secondary structure is not significant. The hydrophobic C-terminus, particularly the amino acids of 17-21, 25-35, and 41-42, is the main region responsible for neurotoxicity and aggregation. Deleting residues 17-21, 25-35 or 41-42 significantly reduced the toxicity. On the other hand, truncation of the peptides at either residues 22-24 or residues 36-40 had little effect on toxicity and aggregative ability. While the N-terminal residues 1-16 may not play a major role in neurotoxicity and aggregation, a lack of N-terminal fragment Ab peptide, (e.g. Ab17-35), does not display the neurotoxicity of either full-length or 17-21, 25-35 truncated Ab peptides.

Transgenic mice, which selectively express the WAP-HBX transgene in mammary gland epithelial cells (ME-cells), were established in order to elucidate the consequences of HBX gene expression on organ differentiation, cell death program and tumor development. Transgene expression was demonstrable by RT-PCR, Northern and Western blot analysis during pregnancy, lactation and after weaning. HBX synthesis neither affect mammary gland differentiation nor apoptosis in ME-cells. Although breast cancer formation was rare in WAP-HBX animals (o1%), WAP-HBX p53 þ /À hybrid animals developed breast tumors at an increased rate (12/85) after a latency period of 8-18 months. We also show here for the first time that HBX can immortalize ME-cells generated from mammary gland tissue segments in a p53-independent fashion. HBX causes cyclin D1 gene overexpression during early pregnancy, and this is maintained in ME-cells isolated either from mammary gland or from breast tumors. Intranuclear cyclin D1 accumulation also occurs in the absence of external growth factors and the BrdU incorporation rate remains high under serum starvation conditions. Finally, both cyclin D1 induction and HBX mitotic activity are dependent on p38 and c-Jun N-terminal kinase, but not on MEK-1 kinase activity.

As one of the virulence factors of Bacillus anthracis, lethal toxin (LT) induces various pathogenic responses including the suppression of the coagulation system. In this study, we observed that LT markedly increased the circulating soluble P-selectin (sP-sel) levels and microparticle (MP) count in wild-type but not P-selectin (P-sel, Selp¡/¡ ) knockout mice. Because sP-sel induces a hypercoagulable state through PSGL-1 pathway to generate tissue factorpositive MPs, we hypothesized that the increase in plasma sP-sel levels can be a self-rescue response in hosts against the LT-mediated suppression of the coagulation system. In agreement with our hypothesis, our results indicated that compared with wild-type mice, Selp ¡/¡ and Selplg ¡/¡ mice were more sensitive to LT. In addition, the recombinant sP-sel treatment markedly ameliorated LT-mediated pathogenesis and reduced mortality. As a result, elicitation of circulating sP-sel is potentially a self-rescue response, which is beneficial to host recovery from an LT-induced hypocoagulation state. These results suggest that the administration of sP-sel is likely to be useful in the development of a new strategy to treat anthrax. KEYWORDSanthrax lethal toxin; hemostasis; microparticle; Soluble P-selectin; P-selectin ligand 1

Microarray studies revealed that as a first hit the SV40 T/t antigen causes deregulation of 462 genes in mammary gland cells (ME cells) of WAP-SVT/t transgenic animals. The majority of deregulated genes are cell proliferation specific and Rb-E2F dependent, causing ME cell proliferation and gland hyperplasia but not breast cancer formation. In the breast tumor cells a further 207 genes are differentially expressed, most of them belonging to the cell communication category. In tissue culture breast tumor cells frequently switch off WAP-SVT/t transgene expression and regain the morphology and growth characteristics of normal ME cells, although the tumor-revertant cells are aneuploid and only 114 genes regain the expression level of normal ME cells. The profile of retransformants shows that only 38 deregulated genes are tumor-specific, and that none of them is considered to be a typical breast cancer gene.

We report here for the ®rst time, that the SV40 small tantigen inhibits mammary gland dierentiation during mid-pregnancy and that about 10% of multiparous WAP-SVt transgenic animals develop breast tumors with latencies ranging from 10 ± 17 months. Cyclin D1 is deregulated and over expressed in the small t-antigen positive mammary gland epithelial cells (ME-cells) and in the breast tumor cells. SV40 small t-antigen immortalized ME-cells (t-ME-cells) exhibit a strong intranuclear cyclin D1 staining, also in the absence of external growth factors and the cells continue to divide for several days without serum. In addition, the expression rate of cyclin E and p21Waf1 but not of p53 is increased. Coimmunoprecipitation experiments revealed that p21Waf1 is mainly associated with the cyclin D/CDK4 but not with the cyclin E/CDK2 complex. WAP-SVT transgenic animals exhibit an almost regular mammary gland development until late pregnancy but the majority of the ME-cells are eliminated by apoptosis during the early lactation period. Tumor formation is delayed and less ecient than in T/tantigen positive animals. Sequestration of p53 and pRb by the N-terminal truncated T-antigen molecules (T1-antigen and T2-antigen) does not aect mammary gland dierentiation and the transgenic animals (WAP-SVBstBam) do not develop breast tumors. Oncogene (2001) 20, 2325 ± 2332.

We recently established transgenic animals (WAP-SV-T/ t) carrying the early coding region of Simian Virus 40 (SV40) under the transcriptional control of the whey acidic milk protein promoter (WAP), which restricts the expression of the transgene to mammary gland epithelial cells (ME-cells). SV40 T/t-antigen synthesis causes premature mammary gland involution during late pregnancy by inducing apoptosis and leads to development of mammary tumors after the ®rst lactation period in both p53 positive (WAP-SV-T/t) and p53 negative double transgenic animals (WAP-SV-T/t.p537/7). The high apoptotic rate persists in all of the T/t-antigen positive breast tumor cells, as well as in established MEtissue culture cell lines. ME-cells which spontaneously switch o the expression of the WAP-SV-T/t transgene do not undergo apoptosis. However, these cells again exhibit an extensive DNA fragmentation when SV40 T/ t-antigen synthesis is reintroduced, which indicates that it is the expression of T/t antigen which is the critical factor for induction of apoptosis. In addition, we isolated several ME-cell lines from di erent breast tumors which have spontaneously lost the T/t-antigen yet remain maximally transformed. Strikingly, these cells contain a missense mutation of the p53 gene at codon 242 (p53 242 ), which substitutes alanine for glycine. This mutation increases p53 stability and it reduces the transactivating function of p53, albeit without a ecting the ability of the protein to interact with the DNA. This indicates that p53 missense mutations are selected for in breast tumors initially expressing T/t-antigen. Therefore, the p53 242 mutation is su cient to maintain the transformed state after the ME-cells have switched o the WAP-SV-T/t transgene. Interestingly, the p53 minus state per se is not su cient to induce ME-cell transformation since homozygous null mice for the p53 gene (p537/7) fail to develop breast cancer.

To see if sodium arsenite enhances the clastogenicity and the mutagenicity of DNA crosslinking agents, Chinese hamster ovary (CHO) cells and human skin fibroblasts were exposed to cis-diamminedichloroplatinum (II) (cis-Pt(II)) or 8-methoxypsoralen (8-MOP) plus long-wave ultraviolet light (UVA) and then to sodium arsenite. The results indicate that the clastogenicity of cis-Pt(II) and 8-MOP plus UVA are enhanced by the post-treatment with sodium arsenite. Chromatid breaks and exchanges are predominantly increased in doubly treated cells. Furthermore, the mutagenicity of cis-Pt(II) at the hypoxanthine-guanine phosphoribosyl transferase locus is also potentiated by sodium arsenite in CHO cells.

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