Dimitar Jakimov

Growth Effects of Some Platinum(II) Complexes with Sulfur-Containing Carrier Ligands on MCF7 Human Breast Cancer Cell Line upon Simultaneous Administration with Taxol

The platinum (II)complexes, cis-[PtCl2(CH3SCH2CH2SCH3)] (Pt1), cis-[PtCl2(dmso)2] (dmso is dimethylsulfoxide; Pt2) and cis-[PtCl2(NH3)2] (cisplatin), and taxol (T) have been tested at different equimolar concentrations. Cells were exposed to complexes for 2 h and left to recover in fresh medium for 24, 48 or 72 h. Growth inhibition was measured by tetrazolium WST1 assay Analyses of the cell cycle, and apoptosis were performed by flow cytometry, at the same exposure times. The IC50 value of each platinum(II) complex as well as combination index (CI; platinum(II) complex + taxol) for various cytotoxicity levels were determined by median effects analysis. MCF7 cells were found to be sensitive to both Pt1 and Pt2 complexe These cisplatin analogues influenced the cell growth more effectively as compared to cisplatin. Cytotoxic effect was concentration and time-dependent. Profound growth inhibitory effect was observed for Pt1 complex, across all its concentrations at all recovery periods. A plateau effect was achieved three days after treatment at Pt1 concentrations ≤ 1 μM. Pt2, however, decreased MCF7 cells survival only for the first 24 h ranging between 50-55%. Pt2 cytotoxicity sharply decreased thereafter, approaching 2 h - treatment cytotoxicity level. The median IC50 values for Pt1 and Pt2 were similar (0.337 and 0.3051 μM, respectively) but only for the first 24 h. The IC50 values for Pt1 strongly depend on the recovery period. On simultaneos exposure of cells to taxol and platinum(II) complexes no consistent effect was found. The Cls for combinations of taxol with Pt1 or Pt2 revealed cytotoxic effects that were in most Cases synergistic (Pt1) or less than addtiive (Pt2). Flow cytometry analysis has shown that each platinum(II) complex induced apoptosis in MCF7 cells. The level of apoptosis correlated with cytotoxicity level for the range concentrations. Both cisplatin analogues, at IC50 concentrations, increased the number of MCF7 cells in G0G1 phase of cell cycle. Pt2-treated cells remained arrested in G0G1 phase up to 72 h after treatment. Combination of Pt2 and taxol caused further arrest of cells in G0G1 phase (24 h) in parallel with strong decrement of G2M phase cells.

17(E)-picolinylidene androstane derivatives as potential inhibitors of prostate cancer cell growth: antiproliferative activity and molecular docking studies.

We report a rapid and efficient synthesis of A-ring modified 17α-picolyl and 17(E)-picolinylidene androstane derivatives from dehydroepiandrosterone. Compounds were validated spectroscopically and structurally characterized by X-ray crystallography. Virtual screening by molecular docking against clinical targets of steroidal anticancer drugs (ERα, AR, Aromatase and CYP17A1) suggests that 17(E)-picolinylidene, but not 17α-picolyl androstanes could specifically interact with CYP17A1 (17α-hydroxylase) with similar geometry and affinity as Abiraterone, a 17-pyridinyl androstane drug clinically used in the treatment of prostate cancer. In addition, several 17(E)-picolinylidene androstanes demonstrated selective antiproliferative activity against PC3 prostate cancer cells, which correlates with Abiraterone antiproliferative activity and predicted CYP17A1 binding affinities. Based on these preliminary results, 17(E)-picolinylidene androstane derivatives could be a promising starting point for the development of new compounds for the treatment of prostate cancer.

Synthesis and anticancer cell potential of steroidal 16,17-seco-16,17a-dinitriles: Identification of a selective inhibitor of hormone-independent breast cancer cells

We report the synthesis of steroidal 16,17-seco-16,17a-dinitriles and investigate their antitumor cell properties. Compounds were evaluated for anticancer potential by in vitro antiproliferation studies, molecular docking and virtual screening. Several compounds inhibit the growth of breast and prostate cancer cell lines (MCF-7, MDA-MB-231 and PC3), and/or cervical cancer cells (HeLa). Supporting this, molecular docking predicts that steroidal 16,17-seco-16,17a-dinitriles could bind with high affinity to multiple molecular targets of breast and prostate cancer treatment (aromatase, estrogen receptor α, androgen receptor and 17α-hydroxylase) facilitated by D-seco flexibility and nitrile-mediated contacts. Thus, 16,17-seco-16,17a-dinitriles may be useful for the design of inhibitors of multiple steroidogenesis pathways. Strikingly, 10, a 1,4-dien-3-on derivative, displayed selective submicromolar antiproliferative activity against hormone-dependent (MCF-7) and -independent (MDA-MB-231) breast cancer cells (IC50 0.52, 0.11μM, respectively). Ligand-based 3D similarity searches suggest AKR1C, 17β-HSD and/or 3β-HSD subfamilies as responsible for this antiproliferative activity, while fast molecular docking identified AKR1C and ERβ as potential binders-both targets in the treatment of hormone-independent breast cancers.

Synthesis, structural analysis and antiproliferative activity of some novel D-homo lactone androstane derivatives

An efficient synthesis of several A,B-modified D-homo lactone androstane derivatives is reported. The synthetic scheme shows the transformation of 17-oxa-D-homoandrost-5-en-16-on-3β-yl acetate 1 into the 5α-hydroxy-17-oxa-D-homoandrostane-6,16-dion-3β-yl acetate (4). After the dehydration of 4, the newly synthesized 6-keto-androst-4-ene-3β-yl acetate derivative 5 was oximinated to give the 6-hydroximino derivative 6, which was converted to A,B-condensed isoxazole derivatives 7 and 8. Compound 4 was also converted (via 6(E)- and 6(Z)-hydroximino derivatives 9 and 10) to the B-seco-cyano derivative 11 under a Beckmann fragmentation, while compound 5 was transformed to the 4β,5β-epoxy derivative 12. Structures were confirmed by IR, 1H NMR, 13C NMR, and HRMS, and for 7 and 8 by X-ray crystallography. All compounds were tested in vitro on six malignant cell lines (MCF-7, MDA-MB-231, PC-3, HeLa, HT-29, K562) and one non-tumor MRC-5 cell line. Significant antiproliferative activity was observed for specific compounds against prostate (PC-3), cervical (HeLa) and colon (HT-29) cancer cells, while no compounds showed antiproliferative activity to non-cancerous control cells (MRC-5). Interestingly, 1–8 displayed selective antiproliferative activity against estrogen-independent (ER−, MDA-MB-231) breast cancer cells over estrogen-dependent (ER+, MCF-7) breast cancer cells.

Selective antitumour activity and ERα molecular docking studies of newly synthesized D-homo fused steroidal tetrazoles

Here we report a convenient “click” synthesis for D-homo fused steroidal tetrazoles 11–14 from androstane and estratriene 16,17-seco-16-nitrile-17-mesyloxy derivatives 5–8, via intramolecular 1,3-dipolar cycloaddition from in situ generated 16,17-seco-17-azido-16-nitriles 5a–8a. Products were validated by 1H/13C-NMR, IR, HRMS, and structurally characterized by X-ray crystallography and computational methods. Compounds were evaluated as potential anti-proliferative agents against a panel of human cancer cell lines. D-Homo fused steroidal tetrazoles 13 and 14 appear to have specific, selective anti-proliferative effects against estrogen receptor positive (ER+) breast adenocarcinoma cells, which correlate with binding energies calculated from molecular docking to the estrogen receptor α-ligand binding domain (ERα-LBD). Moreover, molecular docking suggests that D-ring fused steroidal tetrazoles 13 and 14 could bind to ERα-LBD in a manner similar to known anti-estrogenic compounds. Addition of a D-homo fused tetrazole group appears to structurally mimic the hydrogen bonding potential of β-estradiol, suggesting their general utility in designing novel steroidal tetrazole derivatives as anti-estrogens or inhibitors of steroidogenic enzymes.

Synthesis, X-ray structural analysis, and cytotoxic activity of some new androstane d-homo lactone derivatives

A series of d-homo lactones 4–10 from dehydroepiandrosterone 1 via 16-hydroximino derivatives 2 and 3 were synthesized. The d-homo lactone 4 was transformed by the Oppenauer oxidation to obtain compound 5. The (Z)-2-hydroxymethylene-4-en-3-one compound 6, was obtained through reaction of 4-en-3-one compound 5 with ethyl formate and sodium hydride. The epoxides 8 and 9 were prepared from compound 7 by oxidation with m-chloroperbenzoic acid. Compound 10 was obtained by treating epoxides 8 and 9 with chromium(VI)-oxide. The structure of compounds 6 and 10 were confirmed by X-ray structural analysis. These derivatives were screened for antitumor activity against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER−, MDA-MB-231, prostate cancer AR−, PC-3), and one human non-tumor cell line, MRC-5. Compounds 4, 7, 8, and 10 exhibited significant antitumor activity against MDA-MB-231 cells, while compound 5 showed strong cytotoxicity against MDA-MB-231. No compounds displayed toxicity against MRC-5 cells.

Synthesis, structural analysis and antitumor activity of novel 17α-picolyl and 17(E)-picolinylidene A-modified androstane derivatives

The heterocyclic ring at C-17 position of the androstane compounds plays an important role in biological activity. The aim of the present study was to synthesize and evaluate potential antitumor activity of different A-modified 17α-picolyl and 17(E)-picolinylidene androstane derivatives. In several synthetic steps, novel derivatives bearing the hydroximino, nitrile or lactame functions in A-ring were synthesized and characterized according to the spectral data, by mass analysis as well as XRD analysis (compounds 6, 13 and 15). The structurally most promising compounds 6, 11-17 were investigated as antitumor agents. The in vitro antiproliferative activity was evaluated against six human cancer cell lines: estrogen receptor negative (ER-) breast adenocarcinoma (MDA-MB-231); estrogen receptor positive (ER+) breast adenocarcinoma (MCF-7); prostate cancer (PC-3); human cervical carcinoma (HeLa); lung adenocarcinoma (A549) and colon adenocarcinoma (HT-29) using MTT assay. The results of the 48h incubation time in vitro tests showed that compound 15 was the most effective against PC-3 (IC50 6.6μM), compound 17 against MCF-7 (IC50 7.9μM) cells, while compound 16 exhibited strong antiproliferative effect against both, MCF-7 (IC50 1.7μM) and PC-3 (IC50 8.7μM) cancer cells. It was also found that compounds 16 and 17 induced apoptosis in MCF-7 cells (dicyano derivative 17 stronger then dioxime 16 and reference formestane), with no distinct changes in the cell cycle of MCF-7 cells.

Androstane derivatives induce apoptotic death in MDA-MB-231 breast cancer cells.

Biological investigation was conducted to study in vitro antiproliferative and pro-apoptotic potential of selected 17α-picolyl and 17(E)-picolinylidene androstane derivatives. The antiproliferative impact was examined on six human tumor cell lines, including two types of breast (MCF-7 and MDA-MB-231), prostate (PC3), cervical (HeLa), colon (HT 29) and lung cancer (A549), as well as one normal fetal lung fibroblasts cell line (MRC-5). All derivatives selectively decreased proliferation of estrogen receptor negative MDA-MB-231 breast cancer cells after 48 h and 72 h treatment and compounds showed time-dependent activity. We used this cell line to investigate cell cycle modulation and apoptotic cell death induction by flow cytometry, expression of apoptotic proteins by Western blot and apoptotic morphology by visual observation. Tested androstane derivatives affected the cell cycle distribution and induced apoptosis and necrosis. Compounds had different and specific mode of action, depending on derivative type and exposure time. Some compounds induced significant apoptosis measured by Annexin V test compared to reference compound formestane. Higher expression of pro-apoptotic BAX, downregulation of anti-apoptotic Bcl-2 and cleavage of PARP protein were confirmed in almost all treated samples, but the lack of caspase-3 activation suggested the induction of apoptosis in caspase-independent manner. More cells with apoptotic morphology were observed in samples after prolonged treatment. Structure-activity relationship analysis was performed to find correlations between the structure variations of investigated derivatives and observed biological effects. Results of this study showed that some of the investigated androstane derivatives have good biomedical potential and could be candidates for anticancer drug development.

Structural analysis and antitumor activity of androstane D-seco-mesyloxy derivatives

The study of the influence of steroidal compounds on tumor cell cultures, cell growth, induction of apoptosis and/or cell cycle changes, is a common way of discovering potential therapeutics for treating people suffering from hormone-dependent problems and diseases. Because of the very high mortality rate associated with this class of disease, therapeutics for treating different types of cancers are among the most important. This work presents the synthesis of two stereoisomeric 16,17-secoandrostane mesyloxy derivatives and their 17-hydroxy precursors. Compounds were structurally analyzed by X-ray crystallography, and their antiproliferative activity, influence on the cell cycle and potential to induce apoptosis were investigated.

In vitro evaluation of cytotoxic and mutagenic activity of avarol

The cytotoxicity of avarol, a main secondary metabolite of the Mediterranean sponge Dysidea avara, was in vitro screened by MTT assay against four human tumour cell lines. The colon HT-29 tumour cells practically showed to be the only sensitive ones towards this organic compound. No toxicity was found against the fetal lung fibroblast MRC-5 cells at the concentrations tested. In comparison with doxorubicin, used as a positive control, avarol actually exhibited at least 588-fold less toxicity towards normal MRC-5 cells. Finally, comet assay indicated that DNA fragmentation was almost fivefold higher upon the treatment with doxorubicin, compared to avarol. The obtained results have actually confirmed that avarol scaffold may contribute to development of new cytostatics inspired by nature.