The elucidation of molecular alterations that occur during human breast cancer progression may contribute to the development of preventative strategies. Using in situ hybridizations on a cohort of 94 biopsy lesions, quantitatively increased cyclin D mRNA expression levels were observed in only 18% of benign lesions, which confer no or slightly increased breast cancer risk, and 18% of premalignant atypical ductal hyperplasias, which confer a four to fivefold increase in breast cancer risk. The transition to carcinoma was accompanied by frequent cyclin D mRNA overexpression in 76% of low-grade ductal carcinomas in situ, 87% of higher grade comedo ductal carcinomas in situ and 83% of infiltrating ductal breast carcinomas. The data identify a molecular event that may separate benign and premalignant human breast lesions from any form of breast carcinoma.

The function of prothymosin a has been investigated by using four different antisense oligodeoxyribonucleotides directed at selected regions of its mRNA. In every case, when synchronized human myeloma cells were released from stationary phase by incubation in fresh medium containing antisense oligomers, cell division was prevented or inhibited; sense oligomers and random antisense oligomers had no effect. A detailed analysis of synchronized cell populations indicated that sense-treated and untreated cells divided m17 hr after growth initiation, whereas cells incubated with antisense oligomer 183, a 16-mer targeted 5 bases downstream of the initiation codon, entered mitosis approximately one cell division late. The failure to divide correlated directly with a deficit in prothymosin a and with the continued presence of intact intracellular antisense oligomers over a period ofat least 24 hr. Because antisense oligomers had no effect either on the timing of the induction of prothymosin a mRNA upon growth stimulation or on mRNA levels seen throughout the cell cycle, we concluded that antisense DNA caused specific hybrid arrest of translation. Our data suggest that prothymosin a is required for cell division. However, there is no evidence that prothymosin a directly regulates mitosis.The function of prothymosin a is debatable. Evidence from this and other laboratories suggests that the protein is neither a precursor of thymosin a,, a putative thymic hormone, nor a secreted thymic hormone itself (1-3). Instead, several observations support a role in cell proliferation: (i) Prothymosin a mRNA and protein are present in virtually all mammalian tissues, and a homologous protein has been detected in yeast (1,(4)(5)(6)(7)(8); these findings are consistent with an activity essential to most cells. (ii) The amounts of prothymosin a and its mRNA are roughly proportional to the proliferative activity of the tissue from which they are isolated (1,4,7). (iii) Prothymosin a mRNA is induced in normal human lymphocytes and in serum-starved NIH 3T3 cells upon growth stimulation with mitogens or serum, respectively (1).Using COS cells transfected with the human prothymosin a gene, we have recently shown that prothymosin a is a nuclear protein. We have also found that chimeric proteins composed of all or part of prothymosin a fused with (3-galactosidase are targeted to the nucleus only when the basic amino acids at the carboxyl terminus of prothymosin a are included (9). The presence of a nuclear localization signal indicates a function carried out, at least in part, in the nucleus; the precise nature of that function is unknown.In the present study, we have directly evaluated the relationship between prothymosin a and cell division. Using antisense oligomers to inhibit accumulation ofprothymosin a in a synchronized population of myeloma cells, we have established that cells deficient in prothymosin a cannot divide, that the inhibition is reversible, and that degradation of intracellular antisense oligomers accompanies resumpti...

Autotaxin, a potent human tumor cell motility-stimulating exophosphodiesterase, was isolated and cloned from the human teratocarcinoma cell line NTera2D1. The deduced amino acid sequence for the teratocarcinoma autotaxin has 94% identity to the melanoma-derived protein, 90% identity to rat brain phosphodiesterase I/nucleotide pyrophosphatase (PD-I alpha), and 44% identity to the plasma cell membrane marker PC-I. Utilizing polymerase chain reaction screening of the CEPH YAC library, we localized the autotaxin gene to human chromosome 8q23-24. Northern blot analysis of relative mRNA from multiple human tissues revealed that autotaxin mRNA steady state expression is most abundant in brain, placenta, ovary, and small intestine.

We previously compared the structure and motility suppressive capacity of nm23-H1 by transfection of wild type and site-directed mutant forms into breast carcinoma cells. Wild type nm23-H1 and an nm23-H1 S44A (serine 44 to alanine) mutant suppressed motility, whereas the nm23-H1 P96S , nm23-H1 S120G , and to a lesser extent, nm23-H1 S120A mutant forms failed to do so. In the present study wild type and mutant recombinant Nm23-H1 proteins have been produced, purified, and assayed for phosphorylation and phosphotransfer activities. We report the first association of Nm23-H1 mutations lacking motility suppressive capacity with decreased in vitro activity in histidine-dependent protein phosphotransferase assays. Nm23-H1 P96S , a Drosophila developmental mutation homolog, exhibited normal autophosphorylation and nucleoside-diphosphate kinase (NDPK) characteristics but deficient phosphotransfer activity in three histidine protein kinase assays, using succinic thiokinase, Nm23-H2, and GST-Nm23-H1 as substrates. Nm23-H1 S120G , found in advanced human neuroblastomas, exhibited deficient activity in several histidine-dependent protein phosphotransfer reactions, including histidine autophosphorylation, downstream phosphorylation on serines, and slightly decreased histidine protein kinase activity; significant NDPK activity was observed. The Nm23-H1 S120A mutant was deficient in only histidine-dependent serine autophosphorylation. Nm23-H1 and Nm23-H1 S44A exhibited normal activity in all assays conducted. Based on this correlation, we hypothesize that a histidine-dependent protein phosphotransfer activity of Nm23-H1 may be responsible for its biological suppressive effects.