SAR study of tyrosine-chlorambucil hybrid regioisomers; synthesis and biological evaluation against breast cancer cell lines.

Amino acids were transformed and coupled to chlorambucil, a well-known chemotherapeutic agent, in an attempt to create new anticancer drugs with selectivity for breast cancer cells. Among the amino acids available, tyrosine was selected to act as an estrogenic ligand. It is hypothesized that tyrosine, which shows some structural similitude with estradiol, could possibly mimic the natural hormone and, subsequently, bind to the estrogen receptor. In this exploratory study, several tyrosine-drug conjugates have been designed. Thus, ortho-, meta- and para-tyrosine-chlorambucil analogs were synthesized in order to generate new anticancer drugs with structural diversity, more specifically in regards to the phenol group location. These new analogs were produced in good yield following efficient synthetic methodology. All the tyrosine-chlorambucil hybrids were more effective than the parent drug, chlorambucil. In vitro biological evaluation on estrogen receptor positive and estrogen receptor negative (ER(+) and ER(-)) breast cancer cell lines revealed an enhanced cytotoxic activity for compounds with the phenol function located at position meta. Molecular docking calculations were performed for the pure L-ortho, L-meta- and L-para-tyrosine phenolic regioisomers. The synthesis of all tyrosine-chlorambucil hybrid regioisomers and their biological activity are reported herein. Possible orientations within the targeted protein [estrogen receptor alpha (ERα)] are discussed in relation to the biological activity.

Design, synthesis and biological evaluation of estradiol-chlorambucil hybrids as anticancer agents.

A series of estradiol-chlorambucil hybrids was synthesized as anticancer drugs for site-directed chemotherapy of breast cancer. The novel compounds were synthesized in good yields through efficient modifications of estrone at position 16alpha of the steroid nucleus. The newly synthesized compounds were evaluated for their anticancer efficacy in different hormone-dependent and hormone-independent breast cancer cell lines. The novel hybrids showed significant in vitro anticancer activity when compared to chlorambucil. Structure-activity relationship (SAR) reveals the influence of the length of the spacer chain between carrier and drug molecule.

Synthesis of D- and L-tyrosine-chlorambucil analogs active against breast cancer cell lines.

A series of D- and L-tyrosine-chlorambucil analogs was synthesized as anticancer drugs for chemotherapy of breast cancer. The novel compounds were synthesized in good yields through efficient modifications of D- and L-tyrosine. The newly synthesized compounds were evaluated for their anticancer efficacy in different hormone-dependent and hormone-independent (ER+ and ER-) breast cancer cell lines. The novel analogs showed significant in vitro anticancer activity when compared to chlorambucil. Structure-activity relationship (SAR) reveals both, the influence of the length of the spacer chain and the stereochemistry of the tyrosine moiety. Interestingly, the D- and L-tyrosinol-chlorambucil derivatives with 10 carbon atoms spacer are selective towards MCF-7 (ER+) breast cancer cell line.

DNA interaction with novel antitumor estradiol-platinum(II) hybrid molecule: a comparative study with cisplatin drug.

Platinum(II)-based anticancer drugs are effective for the management and treatment of several types of cancer. Cis-diamminedichloroplatinum(II) (cisplatin) exerts its antitumor activity by binding to DNA via intrastrand cross-links to d(GpG) (dG = deoxyguanosine) and to d(ApG) (dA = deoxyadenosine), causing DNA bending and interfering with DNA replication and transcription. However, the exact binding modes of other platinum(II)-based antitumor drugs to DNA duplex and their mechanism of action have not been clearly investigated. The aim of this study was to examine the binding of a novel anticancer estradiol-platinum(II) hybrid molecule (CD-37) with calf-thymus DNA in vitro and to compare the results with those obtained with cisplatin drug. Solutions containing various CD-37 or cisplatin concentrations were reacted with DNA at physiological pH. Then, using Fourier transform infrared, ultraviolet-visible, and circular dichroism spectroscopic methods, it was possible to characterize the drug binding mode, the binding constant, and structural variations of DNA in aqueous solution. Spectroscopic evidence showed that cisplatin binds to guanine N7 site with minor perturbations of the backbone phosphate group with an overall binding constant of K(cisPt) = 5.73 (+/- 0.45) x 10(4) M(-1). CD-37 binds to DNA duplex via H-bonding network at low drug concentrations with minor perturbations of guanine N7 site at high drug content and with a binding constant of K(CD-37) = 1.0 (+/- 0.15) x 10(4) M(-1). DNA aggregation occurs at high drug concentration, while DNA remains in the B-family structure.

Synthesis and cytotoxic activity of benzopyran-based platinum(II) complexes.

A series of benzopyran-based platinum complexes of types 4 and 5 were synthesized as potential anticancer agents. The novel compounds were synthesized in several steps using simple and efficient chemistry. The newly synthesized compounds were evaluated for their biological efficacy and showed significant in vitro cytotoxic activity in different hormone-dependent and -independent breast cancer cell lines. Docking and other molecular modeling experiments were also performed for one of the potent compounds, 5f, which showed that both the possible enantiomeric forms (5f with 3R,4R and 5f with 3S,4S) of the molecule have comparable lowest energy (for 5f with 3R,4R, -31.953 kcal/mol and for 5f with 3S,4S, -31.944 kcal/mol). The 3D QSAR was examined for the derivatives of both enantiomeric forms and a novel relationship for the 3S,4S derivatives is discussed.

Synthesis of 17beta-estradiol-platinum(II) hybrid molecules showing cytotoxic activity on breast cancer cell lines.

The synthesis of a series of 17beta-estradiol-platinum(II) hybrid molecules is reported. The hybrids are made of a PEG linking chain of various length and a 2-(2'-aminoethyl)pyridine ligand. They are prepared from estrone in five chemical steps with an overall yield of 22%. The length of the PEG chain does not influence the solubility of the compounds as it remains relatively constant throughout the series. MTT assays showed that the derivative with the longest PEG chain showed the best activity against breast cancer cell lines (MCF-7 and MDA-MB-231). Molecular modeling study rationalized the results.

Improved synthesis of unique estradiol-linked platinum(II) complexes showing potent cytocidal activity and affinity for the estrogen receptor alpha and beta.

We have recently reported the synthesis of a platinum(II) complex, made of estradiol, the female sex hormone, and a cisplatin analog, an anticancer drug, linked together by an eleven carbon atoms chain. The novel estradiol-Pt(II) hybrid molecule was synthesized in nine chemical steps with 10% overall yield. This new compound has been tested in vitro on estrogen-dependent (MCF-7) and -independent (MDA-MD-231) (ER(+) and ER(-)) cell lines. Interestingly, the biological activity was quite significant, more potent than that of cisplatin, the compound currently used in chemotherapy. The estrogen receptor binding affinity (ERBA) of this compound was very similar to that of 17beta-estradiol (E(2)) on both estrogen receptors (ERs), alpha and beta. In order to further study this type of molecule, we have decided to synthesize several analogs with the same estrogenic scaffold but with various chain lengths separating the estradiol from the toxic part of the molecule. This was planned in order to study the effect of the length of the linking chain on the biological activity of the hybrids. Four E(2)-Pt(II) hybrid molecules having 6-14 carbon atoms linking chain have been synthesized using a new synthetic methodology. They are synthesized in only eight chemical steps with 21% overall yield. The 17beta-estradiol-linked platinum(II) complexes have been tested for their receptor binding affinity as well as for their cytocidal activity on several breast cancer cell lines. The synthesis and biological results are reported herein.

Exploring the synthesis and anticancer potential of L-tyrosine-platinum(II) hybrid molecules.

The search for new specific chemotherapeutic drugs designed to minimize the toxic side effects resulting from chemotherapy is still a subject of intense research. The objective of the current study was to design a non-steroidal-platinum(II) derivative that would target the estrogen receptor alpha (ERα) without triggering estrogenic cell proliferation. For this purpose, the amino acid L-tyrosine was modified and attached to a cisplatin analog. Hence, the L-tyrosine portion of the molecule could possibly act as a transporter to target the ERα protein and, by doing so concentrate the cytotoxic moiety to hormone-dependent breast cancer cells. Herein, we describe three different alternative methodologies that were used to make these new anticancer molecules. The L-tyrosine-Pt(II) hybrid 5b was made in four steps with 36% overall yield by the first method, in six steps with 11% overall yield by the second method and, in four steps with 23% overall yield by the third method. Preliminary biological activity on breast cancer cell lines indicated that the final hybrids (5a and 5b) were unfortunately inactive but their platinum(II) precursors (14a and 14b) showed activity similar to that of cisplatin.

Design of novel tyrosine-nitrogen mustard hybrid molecules active against uterine, ovarian and breast cancer cell lines.

L-para-Tyrosine was linked to ortho-hydroxyaniline, meta-hydroxyaniline and para-hydroxyaniline giving three distinct tyrosinamide molecules. The new extended amino acid derivatives were constructed to imitate, in part, the estradiol (E(2), the natural female sex hormone) nucleus. The resulting tyrosinamides were then linked to chlorambucil either directly, or via a 5 and 10 carbon atoms spacer chain. This was done in an attempt to target cancerous cells expressing the estrogen receptor alpha (ERα) and to obtain a more specific chemotherapeutic agent. The tyrosinamide-chlorambucil molecules were designed and synthesized in good yields, according to two different approaches. The novel compounds were evaluated for their anticancer efficacy in hormone-dependent and hormone-independent (ER+; MCF-7 and ER-; MDA-MB-231) breast cancer cell lines. Interestingly, the meta-hydroxyphenyl-tyrosinamide-chlorambucil derivatives were more active than the ortho- and para- analogs. The molecules bearing a 5 carbon atoms spacer were selected for additional biological study using a panel of female cancerous cells; breast (ZR-75-1, MDA-MB-436, MDA-MB-468), ovarian (OVCAR-3, A2780) and uterine (Ishikawa, HEC-1A). It was discovered that for breast cancer cells, the new compounds were up to 4.2 times more active than chlorambucil itself.

Synthesis, antiproliferative activity and estrogen receptor α affinity of novel estradiol-linked platinum(II) complex analogs to carboplatin and oxaliplatin. Potential vector complexes to target estrogen-dependent tissues.

In the course of efforts to develop 17ß-estradiol-linked to anticancer agents targeting estrogen-dependent tissue, we identified three estradiol-linked platinum(II) complex analogs to cisplatin (E-CDDP) derivatives namely: VP-128 (1), CD-38 (2) and JMP-39 (3) that exhibit potent in vitro and in vivo (for derivative VP-128) activity along with interaction with the estrogen receptor α (ERα). In this study, we prepared and biologically evaluated two novel classes of estradiol-linked platinum(II) complex analogs to carboplatin (E-CarboP, 1a-3a) and oxaliplatin (E-OxaP, 1b-3b). E-CarboP and E-OxaP were designed and based on the estradiol-linker scaffold of E-CDDP derivatives previously identified. Consequently, we assessed the importance of the nature of platinum(II) salt on the antiproliferative activity on MCF-7 and MDA-MB-231 human mammary carcinoma cell lines together with affinity for the ERα by replacing the dichloroplatinum(II) moiety by a cyclobutane-1,1-dicarboxylateplatinum(II) or an oxalateplatinum(II) moiety. Except for compound 3b which is inactive at the concentration tested, the antiproliferative activity of all compounds on both human mammary carcinomas cell lines are in micromolar range and are more active than carboplatin and oxaliplatin alone but less active that their E-CDDP counterparts (1-3). In addition, E-CarboP derivatives 1a-3a show very low affinity for ERα whereas E-OxaPs 1b and 2b show higher affinity for ERα than their parents E-CDDPs (1-2), suggesting that the nature of the platinum(II) salt involved in the vector complexes is extremely important to both retain significant antiproliferative activity and selectivity for the ERα and possibility to target estrogen-dependent tissues. Finally, E-OxaPs 1b and 2b are potentially promising alternatives vector complexes to target estrogen-dependent tissues.

VP-128, a novel oestradiol-platinum(II) hybrid with selective anti-tumour activity towards hormone-dependent breast cancer cells in vivo.

We have previously reported the synthesis of VP-128, a new 17beta-oestradiol (E(2))-linked platinum(II) hybrid with high affinity for oestrogen receptor alpha (ERalpha). In the present study, we have investigated the anti-tumour activity of VP-128 towards breast cancer cells in vitro and in vivo. We used human ERalpha-positive (MCF-7) and -negative (MDA-MB-468) cells as a model for treatment with increasing doses of VP-128, cisplatin or E(2) in vitro and for xenograft experiments in nude mice in vivo. Compared with cisplatin, VP-128 showed markedly improved in vitro and in vivo anti-tumour activity towards ERalpha-positive MCF-7 breast cancer cells, without increased systemic toxicity. In these caspase-3-deficient cells, treatment with VP-128 overcame weak cellular sensitivity to cisplatin in vitro and in vivo. In these cells, only the hybrid induced apoptosis in an ERalpha-dependent manner, inactivated both X-linked inhibitor of apoptosis protein and Akt, and induced selective nuclear accumulation of ERalpha and the expression of ER-regulated genes c-myc and tff1, which was blocked by ERalpha-specific antagonist ICI 282 780. In the case of ERalpha-negative MDA-MB-468 cells, VP-128, but not cisplatin, induced nuclear accumulation of apoptosis-inducing factor and inhibited c-myc expression. However, VP-128 did not show enhanced in vivo anti-tumour activity compared with cisplatin. These results reveal two different modes of action for VP-128 in ERalpha-positive and -negative breast cancer cells, and highlight the promising therapeutic value of this unique E(2)-platinum hybrid for selective targeting of hormone-dependent cancers.

Transfer RNA bindings to antitumor estradiol-platinum(II) hybrid and cisplatin.

The anticancer platinum (Pt) drugs exert their antitumor activity by direct or indirect Pt-DNA binding. It has been shown that Pt drugs can induce major DNA damage and minor RNA damage during cancer treatment. A recent report showed that a new anticancer estradiol-Pt(II) hybrid molecule (CD-37) binds DNA bases indirectly, while being more effective than cis-diaminedichloroplatinum(II) (cisplatin) against several types of cancer. In this report, we examine the bindings of CD-37 and cisplatin drugs with transfer RNA (tRNA) in vitro and compare the results to those of the corresponding Pt-DNA complexes. Solutions containing various CD-37 or cisplatin concentrations were reacted with tRNA at physiological pH. Using Fourier transform infrared (FTIR), UV-visible, and circular dichroism spectroscopic methods, the drug binding mode, the binding constant, and RNA structural variations are determined for Pt-tRNA complexes in aqueous solution. Structural analysis showed direct binding of cisplatin drug to guanine and adenine N7 sites, while both direct and indirect interactions of CD-37 with tRNA bases and the backbone phosphate group were observed. The overall binding constants estimated were K(CD-37) = 2.77 (+/-0.90) x 10(4) M(1) and K(cisplatin) = 1.72 (+/-0.50) x 10(4) M(1). Major aggregation of tRNA occurs at high CD-37 concentrations, while RNA remains in the A-family structure.

Synthesis of 17beta-estradiol platinum(II) complexes: biological evaluation on breast cancer cell lines.

The synthesis of a novel series of 17beta-estradiol-linked platinum(II) complexes is described. The new molecules are linked with an alkyl chain at position 16alpha of the steroid nucleus and bear a 16beta-hydroxymethyl side chain. They are made from estrone in five chemical steps with an overall yield exceeding 28%. The biological activity of these compounds was evaluated in vitro on estrogen dependent and independent (ER+ and ER-) human breast cancers. The derivatives incorporating a 2-(2'-aminoethyl)pyridine ligand displayed good activity against the cell lines particularly when the connecting arm is 10 carbon atoms long.

Biological evaluation of novel estrogen-platinum(II) hybrid molecules on uterine and ovarian cancers-molecular modeling studies.

We have recently reported the synthesis of a series of original 17beta-estradiol-linked platinum(II) hybrid molecules. The biological activity of these compounds was evaluated in vitro on estrogen dependent and independent (ER(+) and ER(-)) human uterine and ovarian cancers. The hybrid molecules present higher affinity than that of 17beta-estradiol for the estrogen receptor alpha (ERalpha). The cytotoxicity and the affinity of the hybrid molecules are explained using molecular modeling analysis. This study further confirms that the derivatives made of a 2-(2'-aminoethyl)pyridine ligand displayed superior activity against the cell lines particularly when the connecting arm is 8-10 carbon atoms long. Molecular modeling shows that a long side chain can facilitate the access of the platinum(II) moiety to DNA. The novel compounds also prove to be moderately cytotoxic against platinum resistant endometrial and ovarian cancer cell lines.