The phylogenetic relationship of possible progenitors of the cultivated peanut.

The cultivated peanut (Arachis hypogaea L.) is an allotetraploid composed of A and B genomes. The phylogenetic relationship among the cultivated peanut, wild diploid, and tetraploid species in the section Arachis was studied based on sequence comparison of stearoyl-ACP desaturase and oleoyl-PC desaturase. The topology of the trees for both fatty acid desaturases displayed two clusters; one cluster with A genome diploid species and the other with B genome diploid species. The two homeologous genes obtained for each of the two fatty acid desaturases from the tetraploid species A. hypogaea and A. monticola were separated into the A and B genome clusters, respectively. The gene phylogenetic trees showed that A. hypogaea is more closely related to the diploid species A. duranensis and A. ipaensis than to the wild tetraploid species A. monticola, suggesting that A. monticola is not a progenitor of the cultivated peanut. In addition, for the stearoyl-ACP desaturase, the A. duranensis sequence was identical with one of the sequences of A. hypogaea and the A. ipaensis sequence was identical with the other. These results support the hypothesis that A. duranensis and A. ipaensis are the most likely diploid progenitors of the cultivated tetraploid A. hypogaea.

Differential transcriptional activation of peroxisome proliferator-activated receptor gamma by omega-3 and omega-6 fatty acids in MCF-7 cells.

While the role of dietary fats in breast cancer remains controversial, the recent cloning of peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear hormone receptor, from human breast cancer cells lines provides a potential molecular link. Several fatty acids from four classes of dietary fats were tested for their ability to mediate the transcriptional activity of PPARgamma in MCF-7 and MDA-MB-231 cells using growth media with minimal serum. Whereas omega-3 fatty acids inhibit transactivation of PPARgamma to levels below control, omega-6, monounsaturated and saturated fatty acids stimulate the activity of the transcriptional reporter. These studies indicate that individual fatty acids differentially regulate the transcriptional activity of PPARgamma by selectively acting as agonists or antagonists. Furthermore, the transcriptional activation of PPARgamma correlates with cell proliferation in MCF-7 cells. Understanding the effects of individual fats on breast cancer cells and PPARgamma transactivation could provide important new insights into the epidemiology of breast cancer and the role of dietary fat.

MCF-7 and T47D human breast cancer cells contain a functional peroxisomal response.

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors that regulate transcription of target genes. Since attempts have been made to correlate the ingestion of high-fat diets, itself a peroxisome proliferator, with the occurrence of breast cancer, we set about to determine if human breast cancer cells contained a functional PPAR. In this report we demonstrate the presence of an mRNA in two breast cancer cell lines (MCF-7 and T47D) which is specifically recognized by a mouse PPARgamma2 probe. Furthermore, in gel shift assays a consensus PPAR response element (PPRE) was specifically bound by nuclear extracts from MCF-7 cells and was further retarded by antibodies raised to mouse PPARgamma. Finally, when transfected with a PPRE-luciferase transcriptional reporter construct, transcription was increased in response to activators of PPAR and its dimmeric partner the retinoic acid X receptor (RXR). These data indicate that peroxisomal proliferators are capable of mediating transcription in human breast cells and suggest the possibility of a physiological role in the breast.