I focused my attention on Pin1 expression and chemical inhibition in HGS-EOC models.
First, I confirmed that Pin1 is effectively involved in tumor progression utilizing mouse ovarian surface epithelial cancer cell line (STOSE), which closely recapitulates the characteristics of human HGS-EOC. So, I showed that comparing normal and knock down cells there is a tumor formation only in mice with Pin1 expression and activity.
Then I focused my attention in order to develop an efficient Pin1 inhibitor, able to down regulate Pin1 expression in vitro but also in vivo. Starting from the inhibitor developed by Pfizer (Fig.9), which showed a good enzymatic activity in vitro 90, and it’s very specific for the catalytic site of the enzyme, in the last 3 years I worked in order to increase the permeability of this compound.The presence of carboxylate group permits the formation of different H-bond interactions in the proline binding site, interactions necessary for Pin1 catalytic function. Also the benzyl-imidaziole is a donator of hydrogen bonds that stabilize the interaction with Pin1. Despite significant
improvements in Pin1 inhibitor affinity, these benzimidazole-based inhibitors failed to show cellular effects (up to 100 μM) on cancer cells. The authors hypothesized that this was due to poor cell permeability caused by high polarity on the benzimidazole series.
The hydrophobic and nonionizable drugs cannot be loaded into liposomes through conventional means. In fact, ionisable hydrophilic drug can be remote loaded inside the liposomes using a transmembrane pH with efficient incorporation The most important example is the Doxil. But a poorly soluble hydrophobic drug is not encorporated into liposomes with the same high efficacy. For this reasons, how reported from Volgestein group, the hydrophobic compound can be actively loaded into liposomes by encapsulating them into modified cyclodextrins.The encapsulation of a poorly soluble drug into an ionizable cyclodextrin (preloading) enhances its water solubility and permits efficient liposomal loading via a pH gradient.
In our protocol the Pin1 inhibitor, called compound 8, is preloaded inside modified cyclodextrins, Heptakis 6ammino6deoxy cyclodextrins, and then the complex cyclodextrin-compound 8 (C8) is loaded inside the liposomes via a pH gradient. How reported in the published article, the complex liposomes-cyclodextrin-compound 8 (LC8) is able to down regulate the Pin1 level in vitro, reducing the vitality of cancer cells, and also had activity in vivo, reducing the tumor volume and the Pin1 expression.
