In vitro evaluation of newly developed chalcone analogues in human cancer cells.

PURPOSE: Among flavonoids, chalcones have been identified as interesting compounds having chemopreventive and antitumor properties. We studied a panel of newly developed chalcone analogues (S1-S10) using MDA-MB 231 and MCF-7 ADRr breast cancer cells and the T-leukemic Jurkat cell line. Quercetin was used as the reference compound. METHODS: Antiproliferative activity was evaluated by cell counts performed after 72 h of exposure to the drugs. DNA analysis and redox activity were evaluated using flow cytometry. Apoptosis was assessed by morphological analysis, using YOYO-1 as DNA dye; p-glycoprotein function was ascertained by quantitating the efflux of rhodamine 123. RESULTS: All cells were sensitive to chalcone analogues yielding IC50 in micromolar concentrations with the following order regardless of the multidrug resistance (MDR) status: S1 > S2 > quercetin. S1 and S2, the most active compounds, were selected to evaluate their effect on the cell cycle, apoptosis, redox activity, and modulation of the p-glycoprotein function. No significant perturbation in cell cycle was seen with concentration up to 1 microM after 24 h. After 72 h a slight increase in G2/M block and DNA fragmentation occurred at 10 microM. Morphological analysis of apoptosis showed that chalcone analogues induced apoptosis to a higher extent than quercetin. Redox analysis demonstrated that all substances were able to increase intracellular thiol levels, which returned to baseline value after 24 h for all drugs except quercetin. Production of reactive oxygen species was essentially unaffected by all compounds. Finally, in MDR-positive MCF-7 ADRr cells chalcone analogues were unable to modulate p-glycoprotein function while quercetin was able to. CONCLUSIONS: Newly developed S1 and S2 chalcones have a different but higher antitumor activity than quercetin and could be considered as potential new anticancer drugs.

Anti-tumour activity of a panel of taxanes toward a cellular model of human cervical cancer.

Using a model of human cervical cancer (ME-180 cells), the anti-tumour activity of paclitaxel was compared to that of docetaxel and IDN5109, a newly developed taxane. The growth inhibition effect of taxanes was assessed after 3 days of exposure. DNA analysis, the taxane-dependent modulation of the expression of the alpha and beta subunits of tubulin and DNA fragmentation were assessed by flow cytometry. The presence of apoptosis was confirmed by morphological analysis using a laser scan cytometer. For the evaluation of "in vivo" anti-tumour activity, taxanes were administered to nude mice intravenously once daily, according to a q3/4d x 4 schedule. Docetaxel, IDN5109 and paclitaxel obtained "in vitro" IC(50) values of 0.86, 1.4 and 2.4 nM, respectively. DNA analysis demonstrated a transient block at the G(2)/M phase of the cell cycle only after 12 h of culture in the presence of taxanes and an increase of nuclear fragmentation suggestive for apoptosis after additional 12 and 60 h of exposure. Morphological analysis confirmed the presence of apoptosis. Taxanes induced a down-modulation of the alpha subunit of tubulin in the G(0/1) phase of the cell cycle, and an overexpression of the beta subunit in the G(2)/M phase. A strong anti-tumour activity was obtained "in vivo" for nude mice xenografted using ME-180 cells (T/C=0% for all drugs). These data indicate that the three taxanes are strongly active both "in vitro" and "in vivo" toward ME-180 cells. Clinical studies are now needed to ascertain if the higher anti-tumour activity observed "in vitro" using docetaxel and IDN5109 yields a better clinical response in advanced cervical carcinoma with respect to paclitaxel.

Antagonistic effect of the combination gemcitabine/topotecan in ovarian cancer cells.

The in vitro interaction between the new antimetabolite gemcitabine (GEM) and topotecan (TPT) was analyzed in A2780 ovarian cancer cells. The growth inhibitory effect was assessed after 3 days of drug exposure. GEM and TPT obtained in vitro IC50 values of 2.1 +/- 0.9 and 33.7 +/- 10.2 nM, respectively. The interaction between GEM and TPT was evaluated by exposing cancer cells at increasing doses of GEM (0.1, 1, and 10 nM) and TPT (1, 10, 100, and 1000 nM). Analysis of data about the interaction between GEM and TPT was performed by applying the isobole method. An antagonistic effect was noticed when GEM was combined with TPT in the tested concentration range. DNA analysis was also performed and showed an augmentation of cells blocked in the G2/M phase during TPT exposure, while an increase of blocked cells in the G0/1, phase was observed after GEM treatment. This latter effect was predominant when the two drugs were used in combination. We also investigated the effect of sequential exposure to drugs, pretreating A2780 cells for 24 h with TPT and then for 48 h with GEM, and, conversely, pretreating A2780 cells with GEM for 24 h and thereafter with TPT for 48 h. Both these combined sequential treatments showed an antagonist effect of the drugs' combination. Long-term growth inhibition effect was established by clonogenic assay performed after 10 days of culture after drug treatment. Also these data confirmed the antagonistic effect between GEM and TPT in A2780 ovarian cancer cells.

Biological evaluation on different human cancer cell lines of novel colchicine analogs.

Three new 7-0-substituted deacetamidothiocolchicine derivatives have been evaluated for their antitumor activity against various human tumor cell lines, some of which express the multidrug resistance (MDR) phenotype, for their impact on the cell cycle and their binding to tubulin. Colchicine and thiocolchicine were used as reference compounds. Thiocolchicine was the most active agent on MDR-negative cells in terms of growth inhibition, whereas for multidrug-resistant cells, thiocolchicone was the most active compound (IC50 = 14 nM). As indicated by statistical analysis, a perfect agreement for the potency order (IC50 values) of the compounds between all the MDR-negative cancer cells (k = 1.00), a poor agreement between MDR-positive and MDR-negative cancer lines, and a moderate agreement (k = 0.50) between the two resistant cancer cells MCF-7 ADRr and CEM VBL were observed. To gain further insight into the mechanism of the antitumor activity of colchicinoids, the most active compounds, colchicone and thiocolchicone, were selected to evaluate their effect on cell cycle, apoptosis, and tubulin interaction. The highest recruitment activity into the G21/M phase of the cell cycle was detected in thiocolchicone-treated breast cancer cells. Interestingly, after 72 h of culture, when the cell cycle block subsided, a consistent amount of DNA fragmentation, a hallmark of apoptosis, was evident. Morphological analysis of MCF-7 ADRr cells confirmed this hypothesis and revealed that thiocolchicone was able to induce apoptosis in this MDR-bearing model. We also demonstrated, using flow cytometry, that thiocolchicone interacts with alpha- and beta-tubulin, thereby affecting the expression of both subunits.

Tamoxifen induces oxidative stress and apoptosis in oestrogen receptor-negative human cancer cell lines.

Recent data have demonstrated that the anti-oestrogen tamoxifen (TAM) is able to facilitate apoptosis in cancer cells not expressing oestrogen receptor (ER). In an attempt to identify the biochemical pathway for this phenomenon, we investigated the role of TAM as an oxidative stress agent. In two ER-negative human cancer cell lines, namely T-leukaemic Jurkat and ovarian A2780 cancer cells, we have demonstrated that TAM is able to generate oxidative stress, thereby causing thiol depletion and activation of the transcriptional factor NF-kappaB. As described for other oxidative agents, TAM was able to induce either cell proliferation or apoptosis depending on the dose. When used at the lowest dose tested (0.1 microM), a slight proliferative effect of TAM was noticed in terms of cell counts and DNA synthesis rate, whereas at higher doses (10 microM) a consistent occurrence of apoptosis was detected. Importantly, the induction of apoptosis by TAM is not linked to down-regulation or functional inactivation by phosphorylation of the antiapoptotic bcl-2 protein.

Anti-proliferative activity of a new class of taxanes (14beta-hydroxy-10-deacetylbaccatin III derivatives) on multidrug-resistance-positive human cancer cells.

Paclitaxel, docetaxel and a series of new analogs synthesized from 14beta-hydroxy-10-deacetylbaccatin III (14-OH-DAB), a natural diterpene closely related to the core synthon of the 2 above prototypes, were tested in vitro for their growth-inhibitory activity on different human cancer cell lines, including some expressing the classic multidrug-resistant (MDR) phenotype (MCF-7 ADRr and CEM VBLr). The 14-OH-DAB derivatives showed enhanced anti-proliferative activity as compared to the parent compounds on the MDR-positive cancer cell lines. Particularly, IDN 5109 showed a 25- to 30-fold higher activity than paclitaxel. The fold change in activity between paclitaxel and analogs (IC50 paclitaxel/IC50 analogs) on the MDR-positive cell lines was calculated and a significant correlation observed. As far as the MDR-negative MDA-MB 231 cells are concerned, docetaxel and IDN 5109 exhibited a more potent activity than paclitaxel. On the basis of the data obtained on cell growth inhibition, we selected the most active compounds to study their effect on the cell cycle. Cell cycle analysis showed that all of the compounds tested were able to induce cell cycle block at G2/M in a concentration-dependent manner. The amount of cell block, measured as a G1/G2 ratio, was correlated significantly (p < 0.001) with apoptosis, as evaluated in the sub-G1 region (% of DNA fragmentation), thereby suggesting that the G2/M-blocked cells underwent apoptosis. To confirm the occurrence of apoptosis in this system, DNA gel agarose electrophoresis was performed and showed the typical ladder pattern.

Polymethylmethacrylate-antiblastic drug compounds: an in vitro study assessing the cytotoxic effect in cancer cell lines--a new method for local chemotherapy of bone metastasis.

An in vitro study was performed assessing the pharmacologic properties of polymethylmethacrylate (PMMA)-antiblastic agent (doxorubicin and cisplatinum) mixtures in normal and neoplastic cell lines cultures. The study's aim was to analyze the polymerization capacity of PMMA in the presence of doxorubicin and cisplatinum, the release of drug from the mixture, the kinetics of release, and the effect of the released drugs in normal and neoplastic cell cultures. Our data show that even at high concentrations neither doxorubicin nor cisplatinum inhibit the polymerization of PMMA. Moreover, mixtures in vitro can release the antiblastic drug which maintains its pharmacologic activity on sensitive neoplastic cells. Therefore, the PMMA-antiblastic drug mixtures, along with current anti-cancer therapy (systemic chemotherapy and radiation therapy), may provide better local control of the metastatic lesion and of some bone tumors.

Growth inhibitory effect of diheptyl diselenide on various human cancer cell lines.

We tested the antiproliferative effects of Diheptyl Diselenide (DHDSe) on several different human cancer cell lines. Cells derived from human cancer (CG5), colon cancer (WIDR), laryngeal cancer (Hep-2), ovarian cancer (OV 166, OV 1225) and IM-9 lymphoblastoid cells were used. In all cell lines DHDSe inhibited cell growth in a dose dependent manner. At the highest concentration tested, an inhibition of cell proliferation ranging from 48% to 75% compared with control cells was observed. Our results show that DHDSe exerts a direct antiproliferative effect on human cancer cells in vitro and suggest that it may represent the parent compound of a new group of anticancer agents.

Growth inhibitory effect of LH-RH analogs on human breast cancer cells.

The antiproliferative effect of two LH-RH agonists (Pro 9-LH-RH ethylamide and D Ser(t BU)6 Aza Gly 10-LH-RH, ICI 118630) on the human breast cancer cell line CG5 is reported. Although ineffective when used alone, both analogs inhibited in a dose-dependent fashion the growth stimulatory effect of estradiol. LH-RH analogs did not influence the growth inhibitory effect of tamoxifen and medroxyprogesterone acetate. Likewise, these compounds neither modified basal estrogen and progesterone receptor levels nor prevented estrogen-induced increase of progesterone receptor. A marked antiproliferative effect of the analogs was also seen in cells stimulated with other mitogens, such as insulin and epidermal growth factor.

An antiestrogenic action of interferons in human breast cancer cells.

The antiproliferative and antiestrogenic effects of human interferon on estrogen-dependent CG-5 human breast cancer cells in vitro are reported. Fibroblast beta - interferon as well as recombinant alpha - and gamma -interferon inhibited proliferation of CG-5 cells in a dose and time - dependent fashion. In addition, they completely suppressed the two-fold increase in cell number induced by estradiol and showed an additive antiproliferative effect when used in combination with the antiestrogen tamoxifen. These antiestrogenic effects of interferons were accompanied by a reduced receptor binding of estradiol to the cells.