Inhibition of P-glycoprotein activity and reversal of multidrug resistance in vitro by rosemary extract

The transmembrane transport pump P-glycoprotein (Pgp) causes the efflux of chemotherapeutic agents from cells and is believed to be an important mechanism in multidrug resistance (MDR) in mammary tumours. In the present study we demonstrate that an extract of the common dietary herb rosemary (Rosemarinus officinalis Labiatae), increases the intracellular accumulation of commonly used chemotherapeutic agents, including doxorubicin (DOX) and vinblastine (VIN), in drug-resistant MCF-7 human breast cancer cells which express Pgp. Rosemary extract (RE) inhibits the efflux of DOX and VIN, which are known to be substrates of Pgp, but does not affect accumulation or efflux of DOX in wild type MCF-7 cells, which lack Pgp. Treatment of drug-resistant cells with RE increases their sensitivity to DOX, which is consistent with an increased intracellular accumulation of the drug. RE blocks the binding of the VIN analogue azidopine to Pgp. Thus, it appears that RE directly inhibits Pgp activity by inhibiting the binding of drugs to Pgp.

Increased AP-1 activity in drug resistant human breast cancer MCF-7 cells

The expression, DNA binding, and transactivating activity of activator protein 1 (AP-1) was examined in a series of multidrug resistant (MDR) MCF-7 human breast cancer cells that have increasing levels of MDR1 gene expression. We observed an increase in the amount of both c-jun and c-fos mRNA in cells with 12-, 65-, or 200-fold higher resistance to adriamycin when compared to drug-sensitive MCF-7 wild type (WT) cells. Electrophoretic mobility shift assays (EMSA) demonstrated an increase in the DNA binding activity of an AP-1 complex in nuclear extracts from MDR MCF-7 cells when compared to extracts from WT cells. We observed a proportional increase in luciferase expression from a reporter vector containing consensus AP-1 binding sites in transiently transfected MDR cells when compared to WT cells, indicating that AP-1 mediated gene expression is increased in drug-resistant MCF-7 cells. Since the MDR1 promoter contains a putative AP-1 binding site, we used EMSA to examine AP-1 binding activity to an oligonucleotide probe that contained the relevant MDR1 promoter sequences (-123 to -108). Nuclear extracts from resistant MCF-7 cells displayed an increased level of DNA binding of Jun/Jun dimers to the probe, indicating that AP-1 was capable of binding to this promoter site. A luciferase reporter construct containing triplicate copies of the MDR1 promoter sequence was expressed at higher levels in transiently transfected MDR cells when compared to expression in WT cells. Co-transfection of WT cells with a c-jun expression vector and either of the AP-1 luciferase constructs demonstrated that c-jun could activate gene expression from both the consensus and the MDR1 AP-1 sites in a dose dependent manner. In addition, RT-PCR and western blot analysis showed that levels of MDR1 mRNA and Pgp were increased in c-jun transfected WT cells. Taken together, these data indicate that increased AP-1 activity may be an important mediator of MDR by regulating the expression of MDR1.

Increased UDP-glucuronosyltransferase activity and decreased prostate specific antigen production by biochanin A in prostate cancer cells

Our laboratory has characterized androgen metabolism in an androgen-responsive prostate cancer cell line (LNCaP) and showed that these cells accumulated intracellular testosterone primarily as glucuronidated metabolites. Using a cell-free assay with testosterone as substrate, we showed that LNCaP had UDP-glucuronosyltransferase (UDPGT) activity. Because dietary factors, such as flavonoids in soy products, may reduce the risk for hormone-dependent cancers, we studied the effects of flavonoids on testosterone-UDPGT activity. LNCaP cells were exposed to selected flavonoids for up to 6 days. The increase in UDPGT-specific activity was linear over this period. Of the compounds tested, biochanin A was the most potent, with increased activity at concentration range 0.5-50 microM. Activities were linear for time and protein and were unaffected by flavonoids added directly to the assay. Kinetics studies showed no change in Km for testosterone in the face of these large increases in specific activity. Cellular metabolism of testosterone reflected the increase in enzyme activity. Intact cells treated with biochanin A produced testosterone-glucuronide from testosterone at twice the rate of controls. The steroid form of the UDPGT transcript was expressed in LNCaP cells and was enhanced in biochanin A-treated LNCaP cells. Additionally, biochanin A markedly decreased prostate specific antigen (PSA) level against the effect of testosterone on PSA production. Biochanin A significantly decreased the testosterone-stimulated release of PSA, presumably because biochanin A increased UDPGT and increased the intracellular glucuronidation of testosterone. These studies suggest that the modulation of hormone metabolism by dietary factors may be important in the prevention and treatment of prostate cancer.

Differential gene expression in the amnion, chorion, and trophoblast of the human placenta

Human chorionic gonadotrophin (hCG), placental alkaline phosphatase (PLAP), and pregnancy-specific glycoprotein (PSG) are three major proteins produced by the trophoblast of the human placenta. Immunocytochemical studies suggest that PSG and hCG are also present in the human amnion. In this study, we examined whether amniotic and chorionic membranes were capable of expressing trophoblastic-specific genes. As previously reported, trophoblasts express high levels of hCG beta, hCG alpha, PLAP, and PSG. Both amnion and chorion were found to express PLAP and hCG beta mRNA. However, the hCG alpha transcript was expressed only by the amnion, but not by the chorion in the term placenta. Recent molecular cloning studies indicate that human PSGs are a group of closely related placental proteins that, together with the carcinoembryonic antigen family members, comprise a subfamily within the immunoglobulin superfamily. To demonstrate that amnion and chorion also express PSG transcripts, we employed ribonuclease protection analysis using probes specific to the 5' and 3' region of PSG mRNAs. Our data indicate that while amniotic as well as chorionic membrane expressed low levels of the PSG genes, only a certain subpopulation of PSG transcripts were expressed. Furthermore, the amnion and chorion demonstrated differences in PSG species expression from each other and from trophoblastic tissue. Thus, human amnion, chorion and trophoblast selectively express several placental genes.

Characterization of a major member of the rat pregnancy-specific glycoprotein family

The gene encoding the human pregnancy-specific glycoprotein (PSG) belongs to a gene subfamily, comprised of the carcinoembryonic antigen (CEA) and PSG subgroups, within the immunoglobulin superfamily. To study the functional roles of PSG during development in an animal model, we isolated and characterized a near full-length cDNA (rnCGM6) encoding a PSG-related protein from a rat placental cDNA library. rnCGM6 is 2,068 bp in length and contains an open reading frame that encodes a 475-amino-acid polypeptide with a predicted molecular mass of 53 kD. The 5' noncoding sequence is 173 nucleotides, and primer-extension experiments demonstrate that the transcriptional initiation site is located 22-24 nucleotides further upstream. The 3' noncoding sequence contains 470 nucleotides which is followed by a poly(A) tail. In contrast to human PSGs, which contain one immunoglobulin variable-like and two to three immunoglobulin constant-like protein domains, rnCGM6 contains three immunoglobulin variable-like domains and one immunoglobulin constant-like domain. rnCGM6 contains six potential N-linked glycosylation sites and, in its carboxyl-terminal domain, a tyrosine protein kinase phosphorylation site. The tyrosine phosphorylation site is conserved among all rat and human PSG members. rnCGM6 hybridized with a major 2.5-kb and two minor 3.0- and 3.5-kb mRNAs, all primarily expressed in the rat placenta. Ribonuclease protection analysis, using probes specific to the 5', middle, and 3' regions of rnCGM6, and the 5' region of a previously identified cDNA, rnCGM1, mainly yielded fully-protected fragments indicating relatively low sequence similarity among rat PSG-related proteins. Northern hybridization and ribonuclease protection assays also suggest that rnCGM6 may be the major PSG member in rat.

Isolation and characterization of a human amnion epithelial cell line that expresses the pregnancy-specific beta 1-glycoprotein gene

Human pregnancy-specific beta 1-glycoprotein (PSG) is a family of closely related glycoproteins of 72K, 64K, 62K, and 54K. Together with the carcinoembryonic antigen, they form new members of the immunoglobulin superfamily. To study the molecular mechanisms that regulate expression of the PSG gene, we established a human amnion cell line, HAA58OD-8C, immortalized with an origin-defective simian virus-40 (SV40) temperature-sensitive A58 mutant virus. HAA58OD-8C cells were temperature sensitive for maintenance of transformation and expressed genes encoding PSG and the alpha- and beta-subunits of hCG. At the permissive temperature (33 C; transformed phenotype), they expressed low levels of PSG, hCG alpha, and hCG beta mRNAs and synthesized low levels of a 48K PSG polypeptide. At the nonpermissive temperature (39.5 C), HAA58OD-8C cells exhibited a differentiated phenotype, expressed increased levels of PSG, hCG alpha, and hCG beta mRNAs, and produced high levels of PSG polypeptides of 72K and 48K. Sodium butyrate induced PSG mRNA expression, and in the presence of butyrate, HAA58OD-8C cells produced high amounts of PSG polypeptides of 72K, 62K, and 48K. Ribonuclease protection analysis indicated that similar PSG transcripts were expressed by HAA58OD-8C cells and human term placenta. However, these amnion cells expressed selectively a certain population of PSG transcripts. Our results show that this amnion cell line provides a suitable model for studies of PSG gene expression and regulation.

Cloning and expression of a new pregnancy-specific beta 1-glycoprotein member

Human pregnancy-specific beta 1-glycoproteins (PSGs) are a group of closely related placental glycoproteins and members of the immunoglobulin superfamily. To study possible functional roles of PSG, three type 1 cDNA clones which encode PSG in a N-A1-A2-B2-C domain arrangement have been characterized in this laboratory. Now, we report the cloning of a type II cDNA (PSG9) which is 1512 bp and encodes a PSG of 332 amino acids in a N-A1-B2-C domain arrangement. In vitro expression experiments demonstrate that PSG9 encodes a 36 kDa nonglycosylated protein which is processed to a glycosylated protein of 46 kDa. Ribonuclease protection analyses show that PSG mRNAs that share sequence similarity with the PSG9 transcript are expressed in both human placenta and placental fibroblasts.

Growth hormone parameters at four ages in intact and castrated male and female cattle

Plasma Growth hormone (GH) profiles, secretion rates (SR), metabolic clearance rates (MCR) of intravenously infused GH, and response to 0.0165, 0.067, and 0.267 microgram of growth hormone-releasing factor (GHRF)/kg body weight (bwt) were studied in intact and castrated male and female cattle (4 of each) at 5, 8, 12, and 15 mo of age. As cattle aged, overall GH levels in the plasma decreased (P less than .01), GH baseline concentrations declined (P less than .05), SR decreased (P less than .01), half-life of GH decreased (P less than .01), and the GH response to intravenous injections of GHRF declined (P less than .05). Bulls had elevated overall and baseline GH concentrations (P less than .05), greater amplitude and number of GH secretory periods (P less than .01), and greater SR (P less than .05) than steers, heifers, or ovariectomized heifers. Males had more frequent GH spikes and secretory periods of higher amplitudes, greater SR, and greater GH responses to 0.0165 microgram GHRF kg bwt (P less than .05) than females. Castration had no impact on the GH status of heifers. It is suggested that testosterone or its metabolites enhanced GH secretion in bulls.

Insulin-like growth factor-I concentrations in plasma of intact and castrated male and female cattle at four ages

The influence of age, sex and castration on plasma concentrations of insulin-like growth factor-I (IGF-I) and other metabolic hormones related to growth was studied in cattle. Plasma was sampled from bulls, steers, heifers, and ovariectomized heifers at 20-min intervals for 12 hr at 5, 8, 12, and 15 mo of age. Plasma samples from each animal taken during each 12-hr period were composited for analysis of IGF-I, testosterone, total estrogens, thyroxine, triiodothyronine, insulin, and glucose. The mean plasma IGF-I concentration in all cattle increased from 61.6 to 158.6 ng/ml as the animals aged (p less than .01). Over all ages, bulls had greater concentrations of IGF-I than steers, heifers, or ovariectomized heifers (P less than .01). Bulls also had higher concentrations of testosterone (P less than .01) and total estrogens (P less than .01). Triiodothyronine concentration was greater in ovariectomized heifers than in bulls (P less than .01) or steers (P less than .05). Females had higher concentrations of thyroxine than males (P less than .01). Concentrations of triiodothyronine in the cattle were greater (P less than .01) during the winter and early spring as compared with the summer. Concentrations of insulin and glucose were not influenced by sex or castration; however, insulin increased in all cattle with age (P less than .01). The mean increase in IGF-I concentration with age within each of the four groups was associated with an increase in concentration of plasma insulin but the differences due to sex were not related to differences in insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Linkage of two human pregnancy-specific beta 1-glycoprotein genes: one is associated with hydatidiform mole

A genomic clone containing two linked human pregnancy-specific beta 1-glycoprotein (PS beta G) genes has been isolated and characterized. The two genes are arranged in the same 5'----3' orientation; the 3' region (including the A2 and B-C exons) of the upstream gene, PSGGA, is linked to the 5' region (including the 5'/L and L/N exons) of PSGGB, the downstream gene. Depending upon the domains compared, PSGGA and PSGGB share 92-98% nucleotide and 86-95% amino acid sequence identity with PSG93, the most abundant PS beta G transcript. The 3' exon (B-C) of PSGGA contains four alternative splice sites and three polyadenylylation sites, which account for the 3' heterogeneity previously reported in the PS beta G family. Each of the predicted PSGGA-encoded proteins would have a different carboxyl terminus. PSGGB corresponds to the previously identified cDNA PSG6, which encodes proteins containing a 34-amino acid leader peptide and a 108-amino acid N domain, which is one amino acid shorter than the majority of PS beta G N domains. Additionally, the PSGGB-encoded proteins contain the cell-surface recognition tripeptide Arg-Gly-Asp, shared by several previously reported PS beta Gs as deduced from cDNA sequences. Northern blot hybridization performed with a PSGGB-specific oligonucleotide probe to the N domain revealed that PSGGB or a PSGGB-like gene encodes a major 1.7-kilobase mRNA in hydatidiform mole tissues and a major 2.0-kilobase mRNA in term placenta tissues. Moreover, the PSGGB-specific probe hybridized most strongly with mRNA from molar trophoblastic tissue, suggesting that the PSGGB-like species may be the gene preferentially expressed in gestational trophoblastic disease. Additionally, the sequence of a 2315-base-pair PS beta G cDNA (PSG95) that contains an N-A1-A2-B2-C domain arrangement is reported. The coding region of PSG95 is identical to the previously reported cDNA clones PSG1d and FL-NCA, but PSG95 contains an additional 518 and 523 base pairs in the 3' end as compared with PSG1d and FL-NCA, respectively.

Effects of sodium butyrate on the synthesis of human pregnancy-specific beta 1-glycoprotein

Human pregnancy-specific beta 1-glycoprotein (PS beta G) is a polymorphic placental protein which shows strong sequence similarity with the oncofetal protein, carcinoembryonic antigen. To better understand the role of PS beta G in pregnancy, we examined its synthesis and regulation in placental fibroblasts, which had been shown to express the PS beta G gene. The major placental PS beta G is a 72-kDa glycoprotein, while the major fibroblast PS beta G is a 62-kDa species. Administration of sodium butyrate to these fibroblasts slightly stimulated the synthesis of the 62-kDa species but markedly increased the production of two additional PS beta Gs of 72 and 48 kDa. The similarity between the PS beta Gs synthesized by butyrate-treated fibroblasts and human placenta was confirmed by cell-free protein synthesis. Poly(A)+ RNA from butyrate-treated fibroblasts and placenta directed the synthesis of two polypeptides of 48 and 36 kDa, which form the polypeptide backbone of the 72- and 48-kDa glycoproteins. Moreover, the predicted molecular weights of PS beta Gs encoded by the two types of PS beta G cDNA clones were 48,000 and 36,000. Most PS beta G cDNAs identified to date, including the three cDNAs (PSG16, PSG93, and PSG95) isolated in this laboratory, share strong sequence similarity at the 5' region (designated PSG-5') but differ in sequences at their 3' regions. The PSG-5', PSG93-specific, PSG16/PSG93-3', and PSG95-3' probes, which identify the majority of PS beta G mRNAs, hybridized with three PS beta G mRNAs of 2.3, 2.2, and 1.7 kilobases from placental fibroblasts. Butyrate increased the steady-state levels of all three mRNAs. Ribonuclease protection analysis showed that butyrate increased the PS beta G mRNAs containing the PSG-5' or PSG93-specific sequence to approximately 20% of human placental levels. However, unlike human term placenta, which predominantly expressed PS beta G mRNAs with 3'-sequences similar to PSG16/PSG93, the butyrate-treated fibroblasts expressed roughly equal levels of PS beta G mRNAs with the PSG16/PSG93-3' and PSG95-3' ends. All PS beta G cDNAs identified encode proteins with distinct carboxyl termini, suggesting that the composition of the 72-kDa species in placenta and butyrate-treated fibroblasts is likely to be different. Placental fibroblasts provide a unique model for the study of the mechanisms responsible for the differential expression of the PS beta G gene.

Effects of growth hormone-releasing factor and somatostatin on growth hormone secretion in hypophysial stalk-transected beef calves

The effects of growth hormone-releasing factor (GHRF) on growth hormone (GH) secretion were studied in beef calves after hypophysial stalk transection (HST). Peripheral GH concentration during surgery was elevated for 60 min after the initiation of anesthesia to 15 ng/ml, which was greater than plasma levels after HST and during the recovery period (0-30 hr mean, 3 ng/ml; P less than 0.05). Episodic GH secretion normally seen in sham-operated controls (SOC) was abolished after HST. Before HST, calves responded to 80% of the GHRF challenges, whereas after HST calves responded to every challenge of GHRF with an increase in plasma GH. A dose of 0.067 microgram human pancreatic (hp) hpGHRF(1-40)OH/kg body wt 3 days after HST increased plasma GH to 55 ng/ml from a control period mean of 5 ng/ml (P less than 0.04). On Day 8, HST calves received two injections of 0.067 microgram hpGHRF/kg body wt at 3-hr intervals, with feeding 70 min after the first injection. During two preinjection control periods, basal GH averaged less than 4 ng/ml and increased to 17 (P less than 0.02) and 9 (P less than 0.04) ng/ml immediately after the first and second injection of hpGHRF, but the response declined over the 8-day period after surgery. On Days 19 and 20, the HST calves were infused iv with 0.033 and 0.067 microgram somatostatin(SS)-14 (SRIH)/kg body wt, during which a pulse injection of 0.067 microgram hpGHRF/kg body wt was administered. GH increased to 9 and 5 ng/ml during the 0.033- and 0.067-microgram SRIH infusions after GHRF; no somatotropic rebound was observed after the SRIH was discontinued as was seen in the animals while the hypothalamic-hypophysial connections were intact. Five and six months after HST the responses to two analogs of rat hypothalamic GHRF were similar to those in SOC calves. These results indicate that HST calves responded to exogenous GHRF with an abrupt increase in plasma GH, but GH response to GHRF during SRIH infusion was greatly inhibited.

Growth hormone-releasing factor on growth hormone secretion in prepubertal calves

The effects of iv administration of growth hormone-releasing factor (GRF) on growth hormone (GH) release and on nitrogen metabolism were measured in prepubertal calves. Crossbred beef heifers (111 kg) were used in a Latin square design to test the effects of 0, 0.01, 0.033, 0.067, and 0.1 microgram human pancreatic (hp) GRF [hpGRF (1,40)OH]/kg body wt on plasma GH concentrations. When they were given doses of 0.067 and 0.1 microgram hpGRF/kg body wt, plasma GH increased (P less than 0.05) within 5-15 min, compared with injections of control buffer, and then returned to preinjection concentrations. The response to 0.067 microgram hpGRF/kg body wt every 3 hr for 42 hr was studied in five heifers (137 kg body wt). The animals responded to 50% of the GRF injections with an increase in plasma GH during every 6-hr period measured. Nitrogen retention, hormone concentrations, and weight gain were measured in five bull calves (90 kg body wt) administered 0 or 0.067 microgram Nle rat hypothalamic GRF (1,29)NH2/kg body wt every 4 hr for 10 days. Metabolic parameters were interpreted to indicate an anabolic response to GRF even though increases of 16% in nitrogen retention, 23% in plasma somatomedin C concentrations, and 36% in weight gain with pulsatile GRF treatment were variable and statistically similar to those of controls. These results indicate that GRF induces peak GH secretion within 15 min in prepubertal calves and that calves can respond to multiple injections of GRF with an increase in plasma GH.