Matrix metalloproteinases (MMPs) are a family of zinc- and calcium-dependent endopeptidases which are secreted or anchored in the cell membrane and are capable of degrading the multiple components of the extracellular matrix (ECM). MMPs are frequently overexpressed or highly activated in numerous human diseases. Owing to the important role of MMPs in human diseases, many MMP inhibitors (MMPIs) have been developed as novel therapeutics, and some of them have entered clinical trials. However, so far, only one MMPI (doxycycline) has been approved by the FDA. Therefore, the evaluation of the activity of a specific subset of MMPs in human diseases using clinically relevant imaging techniques would be a powerful tool for the early diagnosis and assessment of the efficacy of therapy. In recent years, numerous MMPIs labeled imaging agents have emerged. This article begins by providing an overview of the MMP subfamily and its structure and function. The latest advances in the design of subtype selective MMPIs and their biological evaluation are then summarized. Subsequently, the potential use of MMPI-labeled diagnostic agents in clinical imaging techniques are discussed, including positron emission tomography (PET), single-photon emission computed tomography (SPECT) and optical imaging (OI). Finally, this article concludes with future perspectives and clinical utility.

Cyclopentenone prostaglandins (cyPG) are reactive eicosanoids that may display anti-inflammatory and antiproliferative actions, possibly offering therapeutic potential. Here we report the identification of members of the aldo-keto reductase (AKR) family as selective targets of the cyPG prostaglandin A₁ (PGA₁). AKR enzymes metabolize aldehydes and drugs containing carbonyl groups and are involved in inflammation and tumorigenesis. Thus, these enzymes represent a class of targets to develop small molecule inhibitors with therapeutic activity. Molecular modeling studies pointed to the covalent binding of PGA₁ to Cys299, close to the active site of AKR, with His111 and Tyr49, which are highly conserved in the AKR family, playing a role in PGA₁ orientation. Among AKR enzymes, AKR1B10 is considered as a tumor marker and contributes to tumor development and chemoresistance. We validated the direct modification of AKR1B10 by biotinylated PGA₁ (PGA₁-B) in cells, and confirmed that mutation of Cys299 abolishes PGA₁-B incorporation, whereas substitution of His111 or Tyr49 reduced the interaction. Modification of AKR1B10 by PGA₁ correlated with loss of enzymatic activity and both effects were increased by depletion of cellular glutathione. Moreover, in lung cancer cells PGA₁ reduced tumorigenic potential and increased accumulation of the AKR substrate doxorubicin, potentiating cell-cycle arrest induced by this chemotherapeutic agent. Our findings define PGA₁ as a new AKR inhibitor and they offer a framework to develop compounds that could counteract cancer chemoresistance. Cancer Res; 71(12); 4161–71. ©2011 AACR.

The Vinca alkaloids are a group of widely used anticancer drugs, originally extracted from the Madagascar periwinkle, that disrupt microtubule dynamics in mammalian cells by interfering with proper assembly of α,β-tubulin heterodimers. They favor curved tubulin assemblies that destabilize microtubules and induce formation of spiral aggregates. Their binding energy profiles have been characterized by means of sedimentation velocity assays and the binding site of vinblastine at the interface between two tubulin dimers (α1β1 – α2β2) has been ascertained by X-ray crystallographic studies on a complex of tubulin with the stathmin-like domain of protein RB3, albeit at relatively low resolution. Here we use molecular modeling and simulation techniques to build, refine and perform a comparative analysis of the three-dimensional complexes of vinblastine, vincristine, vinorelbine and vinflunine with a β1α2-tubulin interface in explicit water to rationalize the binding affinity differences in structural and energetic terms. Our results shed some more light into the binding determinants and the structure-activity relationships of these clinically useful agents.