A new high frequency polymorphism in the HER-2/neu oncogene in normal tissue and breast tumors

A single nucleotide polymorphism in the transmembrane domain coding region of HER-2 is associated with development and malignant phenotype of gastric cancer

Alterations of the HER-2 (erbB-2/neu) proto-oncogene have been associated with carcinogenesis and poor prognosis of certain cancers. A single nucleotide polymorphism (Ile/Val, A/G) in the transmembrane domain was reported to be associated with a risk of breast cancer. In our study, we examined the association between the HER-2 polymorphism and gastric carcinoma. The Ile/Ile, Ile/Val and Val/Val genotypes were found in 146 (68.9%), 56 (26.4%) and 10 (4.7%) of 212 gastric cancer patients and in 234 (81.5%), 48 (16.7%) and 5 (1.8%) of 287 control subjects, respectively. The Ile/Val or Val/Val genotype was significantly more frequent in patients than in controls (p = 0.005 and 0.033, respectively). The OR of Val/Val genotype then revealed a significantly enhanced risk of 3.25 (95% CI 1.09-9.70) compared to Ile/Ile genotype; heterozygous Ile/Val genotype showed an intermediate risk of 1.97 (1.27-3.06). In patients, carcinomas of advanced stage were significantly more frequent in patients with Ile/Val or Val/Val genotype than those with Ile/Ile genotype (p < 0.001). The logistic regression analysis for tumor invasion, lymph node metastasis and distant metastasis revealed that lymph node metastasis was most closely associated with the HER-2 genotype. These results suggest that this nucleotide polymorphism in the transmembrane domain-coding region of HER-2 could be associated with development of gastric carcinoma and may serve as a predictor of risk for a malignant phenotype of gastric cancer. The association of HER-2 genotype with clinicopathologic characteristics of gastric cancer was also suggested, which has to be confirmed with a larger sample size.

Suppression of Neu-induced mammary tumor growth in cyclin D1 deficient mice is compensated for by cyclin E

Amplification and/or overexpression of the receptor tyrosine kinase HER2/Neu and the cell cycle regulatory gene cyclin D1 are frequently associated with human breast cancer. We studied the functional significance of cyclin D1 in Neu-induced mammary oncogenesis by developing mice overexpressing either wild-type or mutant Neu in a cyclin D1 deficient background. The absence of cyclin D1 suppresses mammary tumor formation induced by the wild-type or activated mutant form of Neu, which promote multi- and single-step progression of tumorigenesis, respectively. These data indicate that cyclin D1 is preferentially required for Neu-mediated signal transduction pathways in mammary oncogenesis. Significantly, 35% of mutant Neu/cyclin D1(-/-) mice regained mammary tumor potential due to compensation by cyclin E. Thus, shared targets of cyclins D1 and E are important in modulating Neu function in mammary tumorigenesis. Our results imply that the combinatorial inhibition of cyclins D1 and E might be useful in the treatment of malignancies induced by Neu.

Well-differentiated villoglandular adenocarcinoma of the uterine cervix: oncogene/tumor suppressor gene alterations and human papillomavirus genotyping

Twelve well-differentiated villoglandular adenocarcinomas (WDVAs) of the uterine cervix were retrospectively analyzed for the presence and specific genotype of human papillomavirus (HPV), tumor suppressor loss (p53, MCC, APC, BRCA1), cancer gene mutation (K-ras-2, exons 1 and 2, p53 exons 5 to 8), and oncogene amplification (c-erbB-2/HER-2/neu, int-2). Tissue for genetic evaluation was obtained by microdissection, using 4-micron-thick histology sections of archival, formalin-fixed, paraffin-embedded specimens. Genotyping involved nucleic acid amplification and DNA sequencing with gene-specific oligonucleotides and L1 region consensus primers for common strains of HPV. Point mutation and HPV strain determination were accomplished by DNA sequence analysis. Tumor suppressor gene loss and oncogene amplification were performed by allelic imbalance analysis in informative subjects based on DNA sequence and microsatellite-length polymorphisms. HPV was present in all tumors and consisted of type 16 (n = 5, 42%) and type 18 (n = 7, 58%) strains, which have been closely associated with cervical neoplasia. K-ras-2 and p53 genes did not manifest point mutational damage. There was no evidence of oncogene amplification or tumor suppressor gene loss. The presence of HPV in all 12 tumors supports the role of HPV infection in the molecular pathogenesis of this uncommon neoplasm. The absence of associated oncogene or tumor suppressor gene damage is consistent with indolent biological behavior and the favorable prognosis of this unusual tumor.

Multiplex genotype determination at a large number of gene loci

To facilitate large-scale genotype analysis, an efficient PCR-based multiplex approach has been developed. For simultaneously amplifying the target sequences at a large number of genetic loci, locus-specific primers containing 5' universal tails are used. Attaching the universal tails to the target sequences in the initial PCR steps allows replacement of all specific primers with a pair of primers identical to the universal tails and converts the multiplex amplification into "uniplex." Simultaneous amplification of 26 genetic loci with this approach is described. The multiplex amplification can be coupled with genotype determination. By incorporating a single-base mismatch between a primer and the template into the target sequences, a polymorphic site can be converted into a desirable restriction fragment length polymorphism when it is necessary. In this way, the allelic PCR products for the polymorphic loci can be discriminated by gel electrophoresis after restriction enzyme digestion. In this study, 32 loci were typed in such a multiplex way.