ABSTRACT
Using differential-display RT-PCR analysis between androgen-dependent LNCaP-FGC and androgen-independent LNCaP-LNO human prostate-cancer cells, we have identified a gene not previously described as being expressed in prostate. The gene is more highly expressed in androgen-independent than in androgen-dependent LNCaP prostate-cancer cells. Sequence analysis showed that the gene has already been cloned as a transcript present in embryonic brain, with unknown functions. Expression of the gene was found not to be restricted to the prostate, and not regulated by androgens in androgen-independent prostate-cancer cells. In concert with the cell-culture system, Northern-blot analysis of gene expression in vivo, using a panel of human prostate-cancer xenografts, demonstrated that the gene is more highly expressed in androgen-independent than in androgen-dependent prostate-cancer xenografts. The gene could be mapped on human chromosome 8q11. The 8q arm is known to be frequently amplified during prostate-cancer progression and harbors several proto-oncogenes potentially involved in cancer development. Since expression of the gene is positively correlated with prostate-cancer progression and its 8q11 chromosomal localization, we hypothesize that the gene may be involved in the development and progression of prostate cancer.
Subject(s)
Carcinoma/genetics , Chromosomes, Human, Pair 8/genetics , Gene Expression Regulation, Neoplastic , Genes, Neoplasm , Prostatic Neoplasms/genetics , Animals , Base Sequence , Blotting, Northern , Chromosome Mapping , Disease Progression , Humans , Male , Mice , Mice, Nude , Molecular Sequence Data , Neoplasm Transplantation , Neoplasms, Hormone-Dependent/genetics , RNA, Messenger/biosynthesis , Tumor Cells, CulturedABSTRACT
Helicobacter pylori NCTC 11637 lipopolysaccharide (LPS) expresses the human blood group antigen Lewis x (Le(x)) in a polymeric form. Le(x) is beta-D-galactose-(1-4)-[alpha-L-fucose-(1-3)]-beta-D-acetylglucosamine. Schematically the LPS structure is (Le(x))n-core-lipid A. In this report, we show that Le(x) expression is not a stable trait but that LPS displays a high frequency (0.2 to 0.5%) of phase variation, resulting in the presence of several LPS variants in one bacterial cell population. One type of phase variation implied the loss of alpha1,3-linked fucose, resulting in variants that expressed nonsubstituted polylactosamines (also called the i antigen), i.e., Le(x) minus fucose; LPS: (lactosamine)n-core-lipid A. The switch of Le(x) to i antigen was reversible. A second group of variants arose by loss of polymeric main chain which resulted in expression of monomeric Le(y); LPS: (Le(y))-core-lipid A. A third group of variants arose by acquisition of alpha1,2-linked fucose which hence expressed Le(x) plus Le(y); LPS: (Le(y))(Le(x))n-core-lipid A. The second and third group of variants switched back to the parental phenotype [(Le(x))-core-lipid A] in lower frequencies. Part of the variation can be ascribed to altered expression levels of glycosyltransferase levels as assessed by assaying the activities of galactosyl-, fucosyl-, and N-acetylglucosaminyltransferases. Clearly phase variation increases the heterogeneity of H. pylori, and this process may be involved in generating the very closely related yet genetically slightly different strains that have been isolated from one patient.
