Mini Reviews in Medicinal Chemistry - Volume 10, Issue 6, 2010

Increasing evidence demonstrates that three classes of molecules originally derived from all-trans-retinoic acid and its synthetic analogues, which function by interacting with the retinoid nuclear receptors, exert their anticancer activities through alternative signaling pathways. Thus, the methylene-linked analogues (4-HBR, 4-HPRCG, and 4-HBRCG) of N-(4-hydroxyphenyl) retinamide (4-HPR) and its O-glucuronide metabolite (4-HPROG), the cinnamic acid analogues (3- Cl-AHPC and AHPC/ST1926) of 6-[3'-(1-adamantyl)-4'-hydroxyphenyl)]-2-naphthalenecarboxylic acid, and N-(2,3- dihydro-2,2,4,4-tetramethyl-6-benzothiopyranyl),N'-(4-nitrophenyl)thiourea (SHetA2) induce cancer cell-cycle arrest and apoptosis mediated most likely through mitochondrial and/or endoplasmic reticulum stress responses. Structure-activity relationships and potential for clinical translation as anticancer therapeutics are presented.

Tea (Camellia sinensis), a popular beverage, is consumed worldwide. The biological activities and mechanism( s) of chemopreventive effects of green tea polyphenols (monomeric catechins) have been extensively studied, while similar information regarding newly formed major black tea polyphenols (BTPs-oligomeric, polymeric) is not available. Therefore, this review focuses mainly on compiling the evidence on chemopreventive efficacy of black tea extract (BTE) / BTPs and describing their mechanism(s) of anti-initiating, anti-promoting and anti-progressor action(s) in in vivo experimental systems. Overall, the mechanism(s) implicated in the BTPs-mediated inhibition are diverse and involve effects on multiple molecular pathways and genes.

Progesterone is a major female steroid hormone produced by the ovarian corpus luteum and by the placental syncyiotrophoblast during the second trimester. The biological effects of this steroid hormone are mediated by the ubiquitously expressed progesterone receptor. The exact link between progesterone and female reproductive organ cancer is a controversial issue with various cross-talks. The present review summarizes recent trends in the development of some (anti)progestagen in the cure and management of breast and uterine cancers.

MDM2 protein negatively regulates p53 and is found to be elevated in cancer cells. An attractive approach towards targeting MDM2 is the use of small molecule inhibitors that bind to MDM2 and disrupt the MDM2-p53 interaction. Our laboratory has been at the forefront in testing MDM2 inhibitors in pancreatic adenocarcinoma (PaCa), a deadly disease with ~50% wild-type p53 population. Emerging evidence suggests that apart from regulating p53, MDM2 can influence other key molecules involved in cancer. This review summarizes recent advancements in the development of MDM2 inhibitors, their novel primary and secondary targets and highlights their potential as therapeutics for PaCa.

Cyclin-dependent kinases 4 and 6 (Cdk4/6) are important components of cell cycle activation and control in early G1 phase. Both enzymes and their regulators, e.g., cyclins, play critical roles in embryogenesis, homeostasis, and cancerogenesis. Cdk4/6 are attractive targets for cancer treatment. Recently, numerous selective small molecule inhibitors of Cdk4/6 have been developed. The potential of Cdk4/6 inhibitors, particularly, pyrido[2,3-d]pyrimidine derivatives, as both anti-cancer drugs and 124I- and 18F-radiolabeled tracers for cancer imaging using positron emission tomography is discussed.

Natural products are an abundant source of anti cancer agents. They act as cytotoxic drugs, and inhibitors of apoptosis, transcription, cell proliferation and angiogenesis. While pathways targeted by natural products have been well studied, there is paucity of information about the in vivo molecular target/s of these compounds. This review summarizes some of the natural compounds for which the molecular targets, mechanism of action and structural basis of specificity have been well documented. These examples illustrate that 'off target' binding can be explained on the basis of diversity inherent to biomolecular interactions. There is enough evidence to suggest that natural compounds are potent and versatile warheads that can be optimized for a multi targeted therapeutic intervention in cancer.

Phenolics including many polyphenols and flavonoids have the potentials to become chemoprevention and chemotherapy agents. However, poor bioavailability limits their biological effects in vivo. This paper reviews the factors that affect phenolics absorption and their bioavailabilities from the points of view of their physicochemical properties and disposition in the gastrointestinal tract. The up-to-date research data suggested that solubility and metabolism are the primary reasons that limit phenolic aglycones' bioavailability although stability and poor permeation may also contribute to the poor bioavailabilities of the glycosides. Future investigations should further optimize phenolics' bioavailabilities and realize their chemopreventive and chemotherapeutic effects in vivo.