Current Topics in Medicinal Chemistry - Volume 15, Issue 8, 2015

Kruppel-like factor 5 (KLF5) belongs to a family of zinc-finger-containing transcription factors which are involved in regulating expression of a wide range of genes, thereby affecting diverse cellular functions. The activities of KLF5 are regulated by multiple signaling pathways including Wnt, Ras, TGFβ, Hippo, Notch, retinoid acid receptor, and hormone receptors. The expression of KLF5 is frequently abnormal in human cancers and the functions of KLF5 are context dependent. Accumulating evidence suggests that KLF5 represents a novel therapeutic target for cancer therapy. In this review, we discuss the potential biological functions of KLF5 associated with several key signaling pathways that are relevant to cancer as well as the involvement of KLF5 in various human cancers. We also describe the progress in the discovery and development of small molecules targeting KLF5 as potential therapeutics that may benefit cancer patients. The challenges and future research directions on the drug discovery of KLF5 ligands are also presented.

In recent years, there has been an increased effort in the development of therapies which target an epigenetic mode of action. Among thes e efforts include progress in the development of inhibitors of EZH2 (Enhancer of Zeste Homolog 2), a key epigenetic target with strong disease implications to cancer. Over the last 3+ years, multiple reports describing small molecule inhibitors of EZH2 have been described, including those for chemical probes and drug candidates which have entered the clinic as first-in-class agents. Recent progress in this emerging area is presented in this review.

Autophagy is an important basic metabolic mechanism by engulfing and degrading the unnecessary or dysfunctional cellular components within double-membered autolysosomes to maintain cellular homeostasis. Autophagy has sparkled great interest for its complicated functions in different stages of cancer, and is regarded as a potential target for anticancer therapy. As a suppressor pathway, autophagy prevents tumor initiation and as a survival pathway, autophagy contributes to tumor growth and progression by attenuating cellular metabolic stress and resisting therapeutic agents-induced cell death. Many autophagy regulators have been identified as potential cancer therapeutic agents and some cytotoxic anticancer drugs also induce autophagy. Combination regimen of autophagy regulators with other anticancer agent exhibits desirable efficacy and several protocols are underway in clinical trials. This review delineates the possible role of autophagy in anticancer therapy, and discusses reported potent autophagy regulators in cancer treatment.

The mitochondrion’s negatively charged membrane potential has been well documented to drive the accumulation of membrane permeable delocalized lipophilic cations (DLC). DLC attachments to known bioactive compounds can direct organelle localization and improve drug exposure to targets within the mitochondria. Due to the mitochondria’s essential function and its regulation of cell death, DLC targeted therapies are the focus of drug discovery projects altering cellular fate via mitochondrial targets. This review provides an update on recent developments for the two main applications of DLCs: cytoprotective therapies aimed at reducing oxidative stress and cytotoxic therapies aimed at initiating cell death for the treatment of various cancers. Both approaches have produced significant improvements using DLC conjugated compounds that include improved potency, pharmacokinetic properties, and the potential to overcome resistance mechanisms.

Due to ever-increasing failure rates, high cost, unsatisfactory safety profile, and limited efficacy associated with anticancer drug development, the repositioning of established non-cancer drugs for new oncology indications has emerged as an increasingly attractive approach to addressing the unmet cancer-related medical need. With the rapid development of bioinformatics, chemoinformatics as well as high-performance computing, drug repositioning is becoming more intentional than ever, and a significant surge of computational approaches has been well established to greatly facilitate drug repositioning for cancer treatment. In this review, we provide a brief overview of recent advances in the computational drug repositioning for anticancer applications with a specific emphasis on repositioning of non-cancer drugs by use of various computational approaches.

Lysine acetylation is a pivotal mechanism in chromatin processes and the regulation of gene transcription. The acetylated lysine residues of histones are exclusively recognized by bromodomains (BRDs) known as epigenetic reader. Proteins containing BRDs undergo a post-translational modification (PTM) with development of cellular signaling and disease biology. The bromo and extra-terminal (BET) proteins are the second subfamily, which play important roles in cellular proliferation, cell cycle progression and chromatin compaction. Recently, a variety of small molecules have been reported to interact with the BET family proteins and accelerate the validation of BET proteins as druggable targets for treatment of cancers, inflammation and related diseases. In this review, we will summarize the small-molecule inhibitors in clinical and preclinical studies of the BET family bromodomains and their medicinal implications.

Positron emission tomography (PET) is one of the most rapidly growing areas of medical imaging for cancer research. The principal goal of PET imaging is to visualize, characterize, and measure biological processes at the molecular and cellular levels in living subjects using non-invasive procedures. Taking advantage of the traditional diagnostic imaging techniques, PET imaging introduces positron-emitting probes to determine the expression of indicative molecular targets at different stages of cancer progression. As a key component of PET technique, an appropriate imaging probe must be able to specifically reach the target of interest in vivo while retaining in the target within reasonable time to be detected. Over the last decade, numerous target-specific PET probes have been developed and evaluated in preclinical and clinical studies. This review provides an overview of recent advances made in PET imaging of cancer biology with a focus on the best-studied biological targets. The trends in developing future PET imaging probes are also discussed.