Butyrate activates the monocarboxylate transporter MCT4 expression in breast cancer cells and enhances the antitumor activity of 3-bromopyruvate.

Most malignant tumors exhibit the Warburg effect, which consists in increased glycolysis rates with production of lactate, even in the presence of oxygen. Monocarboxylate transporters (MCTs), maintain these glycolytic rates, by mediating the influx and/or efflux of lactate and are overexpressed in several cancer cell types. The lactate and pyruvate analogue 3-bromopyruvate (3-BP) is an inhibitor of the energy metabolism, which has been proposed as a specific antitumor agent. In the present study, we aimed at determining the effect of 3-BP in breast cancer cells and evaluated the putative role of MCTs on this effect. Our results showed that the three breast cancer cell lines used presented different sensitivities to 3-BP: ZR-75-1 ER (+)>MCF-7 ER (+)>SK-BR-3 ER (-). We also demonstrated that 3-BP reduced lactate production, induced cell morphological alterations and increased apoptosis. The effect of 3-BP appears to be cytotoxic rather than cytostatic, as a continued decrease in cell viability was observed after removal of 3-BP. We showed that pre-incubation with butyrate enhanced significantly 3-BP cytotoxicity, especially in the most resistant breast cancer cell line, SK-BR-3. We observed that butyrate treatment induced localization of MCT1 in the plasma membrane as well as overexpression of MCT4 and its chaperone CD147. Our results thus indicate that butyrate pre-treatment potentiates the effect of 3-BP, most probably by increasing the rates of 3-BP transport through MCT1/4. This study supports the potential use of butyrate as adjuvant of 3-BP in the treatment of breast cancer resistant cells, namely ER (-).

Artelastin is a cytotoxic prenylated flavone that disturbs microtubules and interferes with DNA replication in MCF-7 human breast cancer cells.

Artelastin, a novel prenylated flavone, previously isolated from the wood bark of Artocarpus elasticus, was evaluated for its capacity to inhibit the growth of fifty-two human tumor cell lines, representing nine different tumor types. A pronounced dose-dependent growth inhibitory effect was detected in all the cell lines, with GI50 values ranging from 0.8-20.8 microM. Studies to elucidate the basis of the growth inhibitory activity of artelastin were performed in the MCF-7 human breast cancer cell line (GI50 = 6.0 microM). We show that artelastin exerts a biphasic effect in the DNA synthesis of MCF-7 cells, a stimulatory effect at low concentrations (below GI50) for short times of exposition (6 h and 24 h), and an inhibitory effect at high concentrations (above GI50). Remarkably, treated cells that have DNA synthesis affected could be viable and metabolically active. Furthermore, artelastin acts as a cytotoxic rather than a cytostatic compound. Massive cytoplasmatic vacuoles were detected in cells after artelastin treatment. Together with these morphological alterations, cells show the presence of abnormal nuclear morphologies, and occasionally nuclear condensation, which were identified as apoptotic by TUNEL assay. Moreover, artelastin was shown to disturb the microtubule network while no effect was observed on the kinetochores. Flow cytometry analysis of cells treated with artelastin reveal an accumulation in S phase that interferes with the cell cycle progression. Additionally, according to BrdU patterns, studies with synchronized cells at G0 and at G1/S transition also suggest that artelastin delays DNA replication since progression of cells trough S-phase is perturbed.

Cytotoxic activity of lupane-type triterpenes from Glochidion sphaerogynum and Glochidion eriocarpum two of which induce apoptosis.

Six known lupanes lupenone ( 1), 3- epi-lupeol ( 2), glochidone ( 4), glochidonol ( 5), glochidiol ( 6) and lup-20(29)-ene-1beta,3beta-diol ( 7) were isolated from the roots and stem wood of Glochidion eriocarpum and three, 5, 6 and lup-20(29)ene-3alpha,23-diol ( 3), were isolated from the roots and stem wood of Glochidion sphaerogynum. Compounds were identified by (1)H- and (13)C-NMR techniques. Triterpenes 2 - 7 were tested against the growth of three human tumor cell lines, MCF-7, NCI-H-460 and SF-268. Lupanes 3, 5, and 6 exhibited strong inhibitory effects against all three; thus GI (50) values for 3 were 12.7 +/- 3.7, 17.9 +/- 1.1 and 17.9 +/- 0.5, for 5 9.0 +/- 3.7, 4.9 +/- 0.2 and 9.8 +/- 0.5, and for 6 6.63 +/- 0.7, 7.5 +/- 0.5 and 9.7 +/- 0.3.3. Epilupeol was less active, with GI (50) values of 75.6 +/- 11.7, 86.1 +/- 12.4 and 80.9 +/- 2.6 while 7 was moderately active only against MCF-7 (GI (50) = 79.2 +/- 2.4). Additional studies indicated that triterpenes 5 and 6 exerted their antiproliferative activity through the involvement of apoptosis while triterpene 3 did not.

Bioactive diterpenoids, a new jatrophane and two ent-abietanes, and other constituents from Euphorbia pubescens.

A new jatrophane diterpene, pubescenol (1), known ent-abietane lactones, helioscopinolide A (2) and B (3), and taraxerone, 24-methylenecycloartanol, and vanillin have been isolated from Euphorbia pubescens. Diterpenes 1-3 and previously described pubescene D (4) were shown to be moderate inhibitors of the growth of MCF-7, NCI-H460, and SF-268 human tumor cell lines, whereas compounds 2 and 3 also exhibited significant antibacterial activity against Staphylococcus aureus.

Euphopubescenol and euphopubescene, two new jatrophane polyesters, and lathyrane-type diterpenes from Euphorbia pubescens.

The structures of euphopubescenol and euphopubescene, two new macrocyclic jatrophane diterpene polyesters, isolated from the whole dried plant of Euphorbia pubescens, were established as 5alpha,8alpha,15beta-triacetoxy-3alpha-benzoyloxy -4alpha-hydroxy -9,14-dioxo-13beta H-jatropha-6(17),11 E-diene ( 1) and 3beta,7beta,8beta,9alpha,14alpha,15beta-hexaacetoxy-2beta H-jatropha-5 E,11 E-diene ( 2) by 1D- and 2D-NMR (COSY, HMQC, HMBC and NOESY), IR, EI-MS and EI-FTICR-MS. Two known lathyrane derivatives, jolkinol A ( 3) and jolkinol A ( 4), whose (13)C-NMR spectra were assigned, were also isolated. Compounds 1 - 3 have been evaluated for their ability to inhibit the in vitro growth of three human tumour cell lines representing different tumour types, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer). They inhibited both MCF-7 and NCI-H460 cell lines, with GI50 values ranging between 40.9 microM and 95.3 microM, but were found to be ineffective as growth inhibitors of the SF-268 cell line.

Three new jatrophane-type diterpenes from Euphorbia pubescens.

Three new macrocyclic jatrophane diterpene polyesters, named pubescenes A ( 1), B ( 2), and C ( 3), and the known compounds indole-3-aldehyde and scopoletin have been isolated and characterised from the whole dried plant of Euphorbia pubescens. The structures of the new compounds were established by spectroscopic means including 2D-NMR techniques such as COSY, HMQC, HMBC and NOESY experiments. Compounds 1 - 3 were evaluated for their in vitro effect on the growth of three human cancer cell lines MCF-7 (breast), NCI-H460 (lung) and SF-268 (CNS) as well as for their capacity to interfere with the proliferation of human peripheral blood lymphocytes. They exhibited a moderate growth inhibitory effect on the cancer cell line NCI-H460. No effect was observed on the mitogenic response of human lymphocytes to PHA.

Effect of abietane diterpenes from Plectranthus grandidentatus on the growth of human cancer cell lines.

Five known abietane diterpenes, fatty acid esters of 7alpha-acyloxy-6beta-hydroxyroyleanone (1), grandidone A (2), 7alpha-acetoxy-6beta-hydroxyroyleanone (3), 6beta,7alpha-dihydroxyroyleanone (4), and coleon U (5), isolated from Plectranthus grandidentatus Gürke, were evaluated for their in vitro antiproliferative activity against five human cancer cell lines MCF-7, NCI-H460, SF-268, TK-10, and UACC-62. Coleon U (5) exhibited the strongest effect among all the assayed compounds. The abietane 3 revealed also a strong inhibitory effect while diterpenes 2 and 4 inhibited only slightly the growth of all cancer cell lines.