Self-assembly of an anion receptor with metal-dependent kinase inhibition and potent in vitro anti-cancer properties

One topical area of supramolecular chemistry is the binding of anionic species but despite the importance of anions in diverse cellular processes and for cancer development, anion receptors or 'binders' have received little attention as potential anti-cancer therapeutics. Here we report self-assembling trimetallic cryptands (e.g. [L₂(Metal)₃]⁶⁺ where Metal = Cu²⁺, Zn²⁺ or Mn²⁺) which can encapsulate a range of anions and which show metal-dependent differences in chemical and biological reactivities. In cell studies, both [L₂Cu₃]⁶⁺ and [L₂Zn₃]⁶⁺ complexes are highly toxic to a range of human cancer cell lines and they show significant metal-dependent selective activity towards cancer cells compared to healthy, non-cancerous cells (by up to 2000-fold). The addition of different anions to the complexes (e.g. PO₄³-, SO₄²- or PhOPO₃²-) further alters activity and selectivity allowing the activity to be modulated via a self-assembly process. The activity is attributed to the ability to either bind or hydrolyse phosphate esters and mechanistic studies show differential and selective inhibition of multiple kinases by both [L₂Cu₃]⁶⁺ and [L₂Zn₃]⁶⁺ complexes but via different mechanisms.

Fatty acid and sterol metabolism: potential antimicrobial targets in apicomplexan and trypanosomatid parasitic protozoa

Current treatments for diseases caused by apicomplexan and trypanosomatid parasites are inadequate due to toxicity, the development of drug resistance and an inability to eliminate all life cycle stages of these parasites from the host. New therapeutics agents are urgently required. It has recently been demonstrated that type II fatty acid biosynthesis occurs in the plastid of Plasmodium falciparum and Toxoplasma gondii and inhibitors of this pathway such as triclosan and thiolactomycin restrict their growth. Furthermore, Trypanosoma brucei has recently been demonstrated to use type II fatty acid biosynthesis for myristate synthesis and to be susceptible to thiolactomycin. As this pathway is absent from mammals, it may provide an excellent target for novel antimicrobial agents to combat these diverse parasites. Leishmania and Trypanosoma parasites produce ergosterol-related sterols by a biosynthetic pathway similar to that operating in pathogenic fungi and their growth is susceptible to sterol biosynthesis inhibitors. Thus, inhibition of squalene 2,3-epoxidase by terbinafine, 14alpha-methylsterol 14-demethylase by azole and triazole compounds and delta(24)-sterol methyl transferase by azasterols all cause a depletion of normal sterols and an accumulation of abnormal amounts of sterol precursors with cytostatic or cytoxic consequences. However, Leishmania parasites can survive with greatly altered sterol profiles induced by continuous treatment with low concentrations of some inhibitors and they also have some ability to utilise and metabolise host sterol. These properties may permit the parasites to evade treatment with sterol biosynthesis inhibitors in some clinical situations and need to be taken into account in the design of future drugs.

Mechanisms of hormonal prevention of breast cancer

Reproductive history is a consistent risk factor for human breast cancer. Epidemiological studies have repeatedly demonstrated that early age of first pregnancy is a strong protective factor against breast cancer and provides a physiologically operative model to achieve a practical mode of prevention. In rodents, the effects of full-term pregnancy can be mimicked by a three-week exposure to low doses of estrogen and progesterone. Neither hormone alone is sufficient to induce protection. The cellular and molecular mechanisms that underlie hormone-induced refractoriness are largely unresolved. Our recent studies have demonstrated that an early cellular response that is altered in hormone-treated mammary cells is the initial proliferative burst induced by the chemical carcinogen methylnitrosourea. The decrease in proliferation is also accompanied by a decrease in the ability of estrogen receptor-positive cells to proliferate. RNA expression of several mammary cell-cycle-related genes is not altered in hormone-treated mice; however, immunohistochemical assays demonstrate that the protein level and nuclear compartmentalization of the p53 tumor suppressor gene are markedly upregulated as a consequence of hormone treatment. These results support the hypothesis that hormone stimulation, at a critical period in mammary development, results in cells with persistent changes in the intracellular regulatory loops governing proliferation and response to DNA damage. A corollary to this hypothesis is that the genes affected by estrogen and progesterone are independent of alveolar differentiation-specific genes. Suppressive subtractive hybridization-PCR methods have identified several genes that are differentially expressed as a consequence of prior estrogen and progesterone treatment. Future experiments are aimed at determining the mechanisms of hormone-induced upregulation of p53 protein expression as part of the overall goal of identifying and functionally characterizing the genes responsible for the refractory phenotype.