Design, synthesis, and characterization of piperazinedione-based dual protein inhibitors for both farnesyltransferase and geranylgeranyltransferase-I

Targeting prenylation inhibition through the mevalonate pathway

Protein prenylation is a critical mediator in several diseases including cancer and acquired immunodeficiency syndrome (AIDS). Therapeutic intervention has focused primarily on directly targeting the prenyltransferase enzymes, FTase and GGTase I and II. To date, several drugs have advanced to clinical trials and while promising, they have yet to gain approval in a medical setting due to off-target effects and compensatory mechanisms activated by the body which results in drug resistance. While the development of dual inhibitors has mitigated undesirable side effects, potency remains sub-optimal for clinical development. An alternative approach involves antagonizing the upstream mevalonate pathway enzymes, FPPS and GGPPS, which mediate prenylation as well as cholesterol synthesis. The development of these inhibitors presents novel opportunities for dual inhibition of cancer-driven prenylation as well as cholesterol accumulation. Herein, we highlight progress towards the development of inhibitors against the prenylation machinery.

Protein Lipidation: Occurrence, Mechanisms, Biological Functions, and Enabling Technologies

Protein lipidation, including cysteine prenylation, N-terminal glycine myristoylation, cysteine palmitoylation, and serine and lysine fatty acylation, occurs in many proteins in eukaryotic cells and regulates numerous biological pathways, such as membrane trafficking, protein secretion, signal transduction, and apoptosis. We provide a comprehensive review of protein lipidation, including descriptions of proteins known to be modified and the functions of the modifications, the enzymes that control them, and the tools and technologies developed to study them. We also highlight key questions about protein lipidation that remain to be answered, the challenges associated with answering such questions, and possible solutions to overcome these challenges.

Recent progress in developing small molecule inhibitors designed to interfere with ras membrane association: toward inhibiting K-Ras and N-Ras functions

K-Ras and N-Ras are mutated in a wide range of human cancers, thus making these proteins attractive targets of anticancer drug development. However, no effective compounds have been obtained so far. One of the approaches taken to inhibit the function of K-Ras and N-Ras is to interfere with their membrane association. Various attempts have been taken. In the first example, we examine the approach conceived in early 1990s to inhibit protein prenylation that is required for their membrane association. The initial premise that the inhibition of Ras farnesylation leads to the inhibition of Ras was not realized, mainly due to alternative prenylation of K-Ras and N-Ras proteins. This led to the idea that the combined inhibition of FTase and GGTase-I can block membrane association of K-Ras and N-Ras. Dual specificity inhibitors of FTase and GGTase-I (DPIs) were also developed. These compounds were tested in preclinical and clinical studies. It appears that sufficiently high concentration of the drug to inhibit K-Ras was not achieved in previous attempts. In addition, dose-limiting toxicity has been observed and this was primarily ascribed to GGTase-I inhibition. Strategies to confer cancer targeting capabilities to the inhibitors may overcome the dose-limiting toxicity. In the second approach, postprenylation events were exploited. This led to the development of various inhibitors including the ICMT inhibitors. Finally, recent identification of compounds that inhibit the interaction between K-Ras and PDE-δ is discussed.

Targeting Rho GTPase signaling for cancer therapy

Accumulating evidence from basic and clinical studies supports the concept that signaling pathways downstream of Rho GTPases play important roles in tumor development and progression. As a result, there has been considerable interest in the possibility that specific proteins in these signal transduction pathways could be potential targets for cancer therapy. A number of inhibitors targeting critical effector proteins, activators or the Rho GTPases themselves, have been developed. We will review the strategies currently being used to develop inhibitors of Rho GTPases and downstream signaling kinases and discuss candidate entities. Although molecularly targeted drugs that inhibit Rho GTPase signaling have not yet been widely adopted for clinical use, their potential value as cancer therapeutics continues to drive considerable pharmaceutical research and development.

Chemical biology of lipidated proteins

Many signaling proteins such as the members of the Ras superfamily of GTPases are posttranslationally modified by covalent attachment of lipid groups, which is crucial for the correct localization and function of these proteins. Numerous lipidated proteins are oncogens often found mutated in several human cancers. Therefore, several therapeutic strategies have been developed based on the inhibition of the enzymes involved in these lipidation steps. Here, we will summarize the results on protein lipidation inhibition, mainly focusing on the small molecules targeting the isoprenylation and acylation of proteins.