Inhibition of estrogen stimulated mitogenesis by 3-phenylacetylamino-2,6-piperidinedione and its para-hydroxy analog

Transcriptional inhibition of the estrogen response element by antiestrogenic piperidinediones correlates with intercalation into DNA measured by energy calculations

The energy of interaction of antiestrogenic ligands bound to DNA derived from molecular modeling was compared to the capacity of the ligands to directly inhibit the transcriptional activity of an estrogen responsive gene. 3-Phenylacetylamino-2,6-piperidinedione (A10) and related compounds were intercalated into a partially unwound DNA site in a canonical estrogen response element (ERE). The piperidinedione/ERE complexes were subjected to energy minimization and the strength of interaction of the ligands with the DNA was measured. The ability of the ligands to inhibit transactivation was assessed using a reporter gene constructed with the ERE of the vitellogenin gene promoter (ERE(v)-tk-Luc) transiently transfected into the human estrogen receptor-positive MCF-7 breast cancer cell line. The results demonstrate a direct correlation between the calculated energetic fit of the compounds in the ERE and inhibition of ERE(v) transactivation. The order of potency of the compounds to suppress estrogen-dependent reporter gene activity was identical to that previously shown for inhibiting the growth of MCF-7 cells. To our knowledge, these results provide the first direct experimental evidence that the predicted fit of a class of compounds into a defined DNA binding site correlates with the ability of the compounds to modulate specific gene functions regulated at that site.

Low water-soluble uremic toxins

The uremic syndrome is the result of the retention of solutes, which under normal conditions are cleared by the healthy kidneys. Uremic retention products are arbitrarily subdivided according to their molecular weight. Low-molecular-weight molecules are characterized by a molecular weight below 500 D. The purpose of the present publication is to review the main water soluble, nonprotein bound uremic retention solutes, together with their main toxic effects. We will consecutively discuss creatinine, glomerulopressin, the guanidines, the methylamines, myo-inositol, oxalate, phenylacetyl-glutamine, phosphate, the polyamines, pseudouridine, the purines, the trihalomethanes, and urea per se.

Synthesis, spectroscopic characterization, stability assessment and DNA-binding of new 2,6-piperidinedione derivatives

This work reports on structural characterization of new antineoplaston (ANP) representatives, namely 3-(benzoylamino)-2,6-piperidinedione (BPD), 3-(4-methoxybenzoylamino)-2,6-piperidinedione (MPD) and 3-(p-nitrobenzoylamino)-2,6-piperidinedione (NPD). These compounds were prepared by reacting N-(4-substituted benzoyl)-glutamines with N-hydroxysuccinimide to afford the corresponding esters, which were heated to produce the corresponding 2,6-piperidinedione (PD) compounds. Non-destructive analytical procedures such as 1H NMR and NIR analyses confirmed the postulated chemical structures of these PD compounds. HPLC chromatograms at an ambient temperature or from solutions preheated at 30, 40 or 60 degrees C displayed only a single peak for each compound. Combination of heat with pH modification had virtually no effect on the obtained peaks, thus attesting to the stability and purity of these compounds. MS analysis displayed molecular mass ions indicative of BPD, MPD and NPD at m/z 233.4, 263.2 and 278.3, respectively. The fragmentation patterns using MS/MS analyses conformed to the structural and molecular formulae of the prepared compounds. Furthermore, preliminary biological assessments showed the capacity of these compounds to bind to the DNA. NPD, but not BMP or MPD, had a superior affinity to the DNA than the prototype ANP-A10.

Novel piperidinedione analogs as inhibitors of breast cancer cell growth

We previously reported the utility of antineoplaston-A10 (3-phenylacetylamino-2,6-piperidinedione) as an endogenous cancer protector and immune modulator in breast cancer patients (Cancer Lett., 2000, 157, 57). In this study, four new piperidinedione A10 analogs were synthesized and tested for their antimitotic activity on a human breast cancer cell line against the prototype A10 and the antibreast cancer drug tamoxifen. Moreover, the DNA binding capacity of such compounds was evaluated against A10, (E)-3-(4-Nitrocinnamoylamino)-2,6-piperidinedione "3B" and (E)-3-(4-hydroxycinnamoylamino)-2,6-piperidinedione "3D" were several-fold more potent antiproliferative agents than A10 and tamoxifen. They also had significantly higher capacity to bind DNA than A10. Conversely, (E)-3-(cinnamoylamino)-2,6-piperidinedione "3A" and (E)-3-(4-methoxycinnamoylamino)-2,6-piperidinedione) "3C" had weaker biological profiles than the lead compound A10. Detailed synthetic, spectroscopic, and biological data are reported.

Autocrine stimulation of human mammary carcinoma cell proliferation by human growth hormone

Here we have investigated the role of autocrine production of human growth hormone (hGH) in the proliferation of mammary carcinoma cells (MCF-7) in vitro. MCF-7 cells were stably transfected with an expression plasmid encoding the hGH gene, and these cells (designated MCF-hGH) synthesized hGH in the cell and secreted hGH to the medium. For control purposes, a MCF cell line was generated (MCF-MUT) in which the start codon of the hGH gene was disabled, and these cells transcribed the hGH gene without translation to hGH protein. The MCF-hGH cell number increased at a rate significantly greater than that of MCF-MUT under serum-free conditions. Autocrine hGH also synergized with 10% serum and insulin-like growth factor-1 but not 17-beta-estradiol to increase cell number. The increased proliferation of MCF-hGH cells in both serum-free and serum-containing media could be completely abrogated by the use of the nonreceptor dimerizing hGH antagonist, hGH-G120R. Increased mitogenesis as a consequence of autocrine production of hGH was prevented by inhibition of either the p38 MAPK or p42/44 MAPK pathways. MCF-hGH cells also possessed a higher level of STAT5 (but not STATs 1 and 3) mediated transcriptional activation in both serum-free and serum-containing conditions than MCF-MUT cells. Thus we conclude that hGH can act in an autocrine/paracrine manner in human mammary carcinoma cells to promote cell proliferation and transcriptional activation.

Additive effect of mifepristone and tamoxifen on apoptotic pathways in MCF-7 human breast cancer cells

MCF-7 cells growing in culture were used to study the mechanism of the antiproliferative activity of the antiprogestin mifepristone, as compared with the antiestrogen 4-hydroxytamoxifen or the combination of both. These steroid antagonists induced a significant time- and dose-dependent cell growth inhibition (cytotoxicity). This inhibition of cell survival was associated with a significant increase in DNA fragmentation (apoptosis), downregulation of bcl2, and induction of TGFbeta1 protein. Abrogation of the mifepristone- and/or 4-hydroxytamoxifen-induced cytotoxicity by TGFbeta1 neutralizing antibody confirms the correlation between induction of active TGFbeta1 and subsequent cell death. The effect of a combination of mifepristone and 4-hydroxytamoxifen on cell growth inhibition, on the increase in DNA fragmentation, bcl2 downregulation, and induction of TGFbeta1 protein was additive and significantly different (P < 0.05) from the effect of monotherapy. A translocation of protein kinase C (PKC) activity from the soluble to the particulate and/or nuclear fraction appeared to be also additive in cells treated with a combination of both 4-hydroxytamoxifen and mifepristone. These results suggest that the mechanism of the additive antiproliferative activity of mifepristone and tamoxifen could be explained at least in part by an additive induction of apoptosis in both estrogen and progesterone receptor positive MCF-7 breast cancer cells. A bcl2 downregulation, the PKC transduction pathway, and TGFbeta1 expression seem to be involved in this additive mechanism of action. Our data further suggest that a combination of an antiprogestin with tamoxifen may be more effective than tamoxifen monotherapy in the management of human breast cancer.

Design and synthesis of potent antitumor 5,4'-diaminoflavone derivatives based on metabolic considerations

Recently, we reported that 5,4'-diaminoflavone (1) exhibits potent and specific growth-inhibitory activity against the estrogen receptor (ER)-positive human breast cancer cell line MCF-7. However, when compound 1 was incubated with S-9 mix, its metabolites were observed. Moreover, addition of S-9 mix to the medium caused the drastic decrease in activity of compound 1. Since the 6-, 8-, and 3'-positions were considered to be metabolized oxidatively in vivo from MO calculations, a series of 5,4'-diaminoflavone derivatives substituted at such putative metabolic positions with various functional groups were synthesized aiming at the metabolically stable derivatives. Among them, 5,4'-diamino-6,8,3'-trifluoroflavone (14d) exhibited strong growth-inhibitory activity against MCF-7 cells even in the presence of S-9 mix. Moreover, orally administered compound 14d completely suppressed the growth of MCF-7 inoculated into nude mice, and the effect was more potent than that of compound 1. In addition to ER-positive breast cancer cells, compound 14d exhibited growth-inhibitory activity against a panel of human cancer cell lines including a part of ER-negative breast, endometrial, ovarian, and liver cancers. From these results, fluorine introduction to the putative metabolic positions of compound 1 was elucidated to be effective in the enhancement of the in vivo antitumor activity, probably due to the block of the metabolic deactivation.

Design of novel antiestrogens

The physicochemical principle of "die and coin" complementarity proffered by Pauling and Delbruck and exemplified in Watson and Crick DNA was used to design new antineoplastic compounds. In search of an explanation for why certain molecules and not others are present in nature, biologically active small molecules were discovered to exhibit complementarity when inserted into cavities between base pairs in DNA. Ligands in the steroid/thyroid hormone/vitamin D family fit particularly well into the site 5'-dTdG-3'.5'-dCdA-3'. Degree of fit of various candidate compounds in the manner of a given hormone correlated with degree of hormonal activity. Hormone antagonists fit into the same site but in a different manner than the agonists. Computer graphics and energy calculations confirmed salient observations including the remarkable complementarity of estradiol and DNA. Using the above criteria, a new candidate antiestrogen, para-hydroxyphenyl-acetylamino-2,6-piperidinedione was successfully designed. Taken as a whole, these results coupled with recent independent findings raise the possibility that the mode of action of certain hormones and hormone antagonists may involve direct insertion into DNA mediated by classical protein receptors and other transcription factors.

Antiestrogenic piperidinediones designed prospectively using computer graphics and energy calculations of DNA-ligand complexes

Drug design technology based upon DNA stereochemistry and now supplemented by computer modeling was used to design a novel compound to inhibit estrogen-induced tumor cell growth. A known compound 3-phenylacetylamino-2,6-piperidinedione (PP) was accommodated in partially unwound DNA in a manner consistent with criteria for antiestrogens. Examination of the PP-DNA complex revealed that substitution of a hydroxyl group at the para position (p-OH-PP) would provide a stereospecific hydrogen bond and a substantial increase in fit as assessed by energy calculations. The antiestrogen tamoxifen could also be accomodated within the site; analogous substitution of a hydroxyl at the 4 position resulted in a better fitting molecule. 4-Hydroxytamoxifen is a more potent antiestrogen than tamoxifen. Synthesis and subsequent evaluation of p-OH-PP as an inhibitor of estrogen stimulated MCF-7 (E3) human breast cancer cell growth demonstrated that p-OH-PP was more active than both PP and its hydrolysis product phenylacetylglutamine. As predicted, the order of fit into DNA correlated with the relative ability to inhibit estrogen-induced growth of tumor cells suggesting that the evolving drug design technology will be valuable in developing new drugs for breast cancer.