Liposomal delivery of a Pin1 inhibitor complexed with cyclodextrins as new therapy for high-grade serous ovarian cancer

The role of the master cancer regulator Pin1 in the development and treatment of cancer

This review examines the complex role of Pin1 in the development and treatment of cancer. Pin1 is the only peptidyl-prolyl isomerase (PPIase) that can recognize and isomerize phosphorylated Ser/Thr-Pro peptide bonds. Pin1 catalyzes a structural change in phosphorylated Ser/Thr-Pro motifs that can modulate protein function and thereby impact cell cycle regulation and tumorigenesis. The molecular mechanisms by which Pin1 contributes to oncogenesis are reviewed, including Pin1 overexpression and its correlation with poor cancer prognosis, and the contribution of Pin1 to aggressive tumor phenotypes involved in therapeutic resistance is discussed, with an emphasis on cancer stem cells, the epithelial-to-mesenchymal transition (EMT), and immunosuppression. The therapeutic potential of Pin1 inhibition in cancer is discussed, along with the promise and the difficulties in identifying potent, drug-like, small-molecule Pin1 inhibitors. The available evidence supports the efficacy of targeting Pin1 as a novel cancer therapeutic by analyzing the role of Pin1 in a complex network of cancer-driving pathways and illustrating the potential of synergistic drug combinations with Pin1 inhibitors for treating aggressive and drug-resistant tumors.

Integrating computational methods guided the discovery of phytochemicals as potential Pin1 inhibitors for cancer: pharmacophore modeling, molecular docking, MM-GBSA calculations and molecular dynamics studies

Pin1 is a pivotal player in interactions with a diverse array of phosphorylated proteins closely linked to critical processes such as carcinogenesis and tumor suppression. Its axial role in cancer initiation and progression, coupled with its overexpression and activation in various cancers render it a potential candidate for the development of targeted therapeutics. While several known Pin1 inhibitors possess favorable enzymatic profiles, their cellular efficacy often falls short. Consequently, the pursuit of novel Pin1 inhibitors has gained considerable attention in the field of medicinal chemistry. In this study, we employed the Phase tool from Schrödinger to construct a structure-based pharmacophore model. Subsequently, 449,008 natural products (NPs) from the SN3 database underwent screening to identify compounds sharing pharmacophoric features with the native ligand. This resulted in 650 compounds, which then underwent molecular docking and binding free energy calculations. Among them, SN0021307, SN0449787 and SN0079231 showed better docking scores with values of -9.891, -7.579 and -7.097 kcal/mol, respectively than the reference compound (-6.064 kcal/mol). Also, SN0021307, SN0449787 and SN0079231 exhibited lower free binding energies (-57.12, -49.81 and -46.05 kcal/mol, respectively) than the reference ligand (-37.75 kcal/mol). Based on these studies, SN0021307, SN0449787, and SN0079231 showed better binding affinity that the reference compound. Further the validation of these findings, molecular dynamics simulations confirmed the stability of the ligand-receptor complex for 100 ns with RMSD ranging from 0.6 to 1.8 Å. Based on these promising results, these three phytochemicals emerge as promising lead compounds warranting comprehensive biological screening in future investigations. These compounds hold great potential for further exploration regarding their efficacy and safety as Pin1 inhibitors, which could usher in new avenues for combating cancer.

pH-sensitive niosomes for ATRA delivery: A promising approach to inhibit Pin1 in high-grade serous ovarian cancer

The peptidyl-prolyl cis/trans isomerase Pin1 positively regulates numerous cancer-driving pathways, and it is overexpressed in several malignancies, including high-grade serous ovarian cancer (HGSOC). The findings that all-trans retinoic acid (ATRA) induces Pin1 degradation strongly support that ATRA treatment might be a promising approach for HGSOC targeted therapy. Nevertheless, repurposing ATRA into the clinics for the treatment of solid tumors remains an unmet need mainly due to the insurgence of resistance and its ineffective delivery. In the present study, niosomes have been employed for improving ATRA delivery in HGSOC cell lines. Characterization of niosomes including hydrodynamic diameter, ζ-potential, morphology, entrapment efficiency and stability over time and in culture media was performed. Furthermore, pH-sensitiveness and ATRA release profile were investigated to demonstrate the capability of these vesicles to release ATRA in a stimuli-responsive manner. Obtained results documented a nanometric and monodispersed samples with negative ζ-potential. ATRA was efficiently entrapped, and a substantial release was observed in the presence of acidic pH (pH 5.5). Finally, unloaded niosomes showed good biocompatibility while ATRA-loaded niosomes significantly increased ATRA Pin1 inhibitory activity, which was consistent with cell growth inhibition. Taken together, ATRA-loaded niosomes might represent an appealing therapeutic strategy for HGSOC therapy.

Cyclodextrin-Based Arsenal for Anti-Cancer Treatments

Anti-cancer drugs are mostly limited in their use due to poor physicochemical and biopharmaceutical properties. Their lower solubility is the most common hurdle limiting their use upto their potential. In the recent years, the cyclodextrin (CD) complexation have emerged as existing approach to overcome the problem of poor solubility. CD-based nano-technological approaches are safe, stable and showed well in vivo tolerance and greater payload for encapsulation of hydrophobic drugs for the targeted delivery. They are generally chosen due to their ability to get self-assembled to form liposomes, nanoparticles, micelles and nano-sponges etc. This review paper describes a birds-eye view of the various CD-based nano-technological approaches applied for the delivery of anti-cancer moieties to the desired target such as CD based liposomes, niosomes, niosoponges, micelles, nanoparticles, monoclonal antibody, magnetic nanoparticles, small interfering RNA, nanorods, miscellaneous formulation of anti-cancer drugs containing CD. Moreover, the author also summarizes the various shortcomings of such a system and their way ahead.

3D dynamic cultures of HGSOC organoids to model innovative and standard therapies

High-grade serous ovarian cancer (HGSOC) needs new technologies for improving cancer diagnosis and therapy. It is a fatal disease with few options for the patients. In this context, dynamic culture systems coupling with patient-derived cancer 3D microstructures could offer a new opportunity for exploring novel therapeutic approaches. In this study, we optimized a passive microfluidic platform with 3D cancer organoids, which allows a standardized approach among different patients, a minimum requirement of samples, multiple interrogations of biological events, and a rapid response. The passive flow was optimized to improve the growth of cancer organoids, avoiding the disruption of the extracellular matrix (ECM). Under optimized conditions of the OrganoFlow (tilting angle of 15° and an interval of rocking every 8 min), the cancer organoids grow faster than when they are in static conditions and the number of dead cells is reduced over time. To calculate the IC ₅₀ values of standard chemotherapeutic drugs (carboplatin, paclitaxel, and doxorubicin) and targeted drugs (ATRA), different approaches were utilized. Resazurin staining, ATP-based assay, and DAPI/PI colocalization assays were compared, and the IC ₅₀ values were calculated. The results showed that in the passive flow, the IC ₅₀ values are lower than in static conditions. FITC-labeled paclitaxel shows a better penetration of ECM under passive flow than in static conditions, and cancer organoids start to die after 48 h instead of 96 h, respectively. Cancer organoids are the last frontiers for ex vivo testing of drugs that replicate the response of patients in the clinic. For this study, organoids derived from ascites or tissues of patients with Ovarian Cancer have been used. In conclusion, it was possible to develop a protocol for organoid cultures in a passive microfluidic platform with a higher growth rate, faster drug response, and better penetration of drugs into ECM, maintaining the samples' vitals and collecting the data on the same plate for up to 16 drugs.

An Updated Overview of Cyclodextrin-Based Drug Delivery Systems for Cancer Therapy

Encompassing a group of complex and heterogeneous diseases, cancer continues to be a challenge for patients and healthcare systems worldwide. Thus, it is of vital importance to develop advanced treatment strategies that could reduce the trends of cancer-associated morbidity and mortality rates. Scientists have focused on creating performant delivery vehicles for anti-cancer agents. Among the possible materials, cyclodextrins (CDs) attracted increasing interest over the past few years, leading to the emergence of promising anti-tumor nanomedicines. Tackling their advantageous chemical structure, ease of modification, natural origin, biocompatibility, low immunogenicity, and commercial availability, researchers investigated CD-based therapeutical formulations against many types of cancer. In this respect, in this paper, we briefly present the properties of interest of CDs for designing performant nanocarriers, further reviewing some of the most recent potential applications of CD-based delivery systems in cancer management.

An Updated Overview of Cyclodextrin-Based Drug Delivery Systems for Cancer Therapy

Encompassing a group of complex and heterogeneous diseases, cancer continues to be a challenge for patients and healthcare systems worldwide. Thus, it is of vital importance to develop advanced treatment strategies that could reduce the trends of cancer-associated morbidity and mortality rates. Scientists have focused on creating performant delivery vehicles for anti-cancer agents. Among the possible materials, cyclodextrins (CDs) attracted increasing interest over the past few years, leading to the emergence of promising anti-tumor nanomedicines. Tackling their advantageous chemical structure, ease of modification, natural origin, biocompatibility, low immunogenicity, and commercial availability, researchers investigated CD-based therapeutical formulations against many types of cancer. In this respect, in this paper, we briefly present the properties of interest of CDs for designing performant nanocarriers, further reviewing some of the most recent potential applications of CD-based delivery systems in cancer management.

New PIN1 inhibitors identified through a pharmacophore-driven, hierarchical consensus docking strategy

PIN1 is considered as a therapeutic target for a wide variety of tumours. However, most of known inhibitors are devoid of cellular activity despite their good enzyme inhibitory profile. Hence, the lack of effective compounds for the clinic makes the identification of novel PIN1 inhibitors a hot topic in the medicinal chemistry field. In this work, we reported a virtual screening study for the identification of new promising PIN1 inhibitors. A receptor-based procedure was applied to screen different chemical databases of commercial compounds. Based on the whole workflow, two compounds were selected and biologically evaluated. Both ligands, compounds VS1 and VS2, showed a good enzyme inhibitory activity and VS2 also demonstrated a promising antitumoral activity in ovarian cancer cells. These results confirmed the reliability of our in silico protocol and provided a structurally novel ligand as a valuable starting point for the development of new PIN1 inhibitors.

Cyclodextrin-Modified Nanomaterials for Drug Delivery: Classification and Advances in Controlled Release and Bioavailability

In drug delivery, one widely used way of overcoming the biopharmaceutical problems present in several active pharmaceutical ingredients, such as poor aqueous solubility, early instability, and low bioavailability, is the formation of inclusion compounds with cyclodextrins (CD). In recent years, the use of CD derivatives in combination with nanomaterials has shown to be a promising strategy for formulating new, optimized systems. The goals of this review are to give in-depth knowledge and critical appraisal of the main CD-modified or CD-based nanomaterials for drug delivery, such as lipid-based nanocarriers, natural and synthetic polymeric nanocarriers, nanosponges, graphene derivatives, mesoporous silica nanoparticles, plasmonic and magnetic nanoparticles, quantum dots and other miscellaneous systems such as nanovalves, metal-organic frameworks, Janus nanoparticles, and nanofibers. Special attention is given to nanosystems that achieve controlled drug release and increase their bioavailability during in vivo studies.

Self-Therapeutic Cobalt Hydroxide Nanosheets (Co(OH)2 NS) for Ovarian Cancer Therapy

High-grade serous ovarian cancer (HGSOC) is one of the major life-threatening cancers in women, with a survival rate of less than 50%. So far, chemotherapy is the main therapeutic tool to cure this lethal disease; however, in many cases, it fails to cure HGSOC even with severe side effects. Self-therapeutic nanomaterials could be an effective alternative to chemotherapy, facilitated by their diverse physicochemical properties and the ability to generate reactive species for killing cancer cells. Herein, inorganic cobalt hydroxide nanosheets (Co(OH)₂ NS) were synthesized by a simple solution process at room temperature, and morphological, spectroscopic, and crystallographic analyses revealed the formation of Co(OH)₂ NS with good crystallinity and purity. The as-prepared Co(OH)₂ NS showed excellent potency, comparable to the FDA-approved cisplatin drug to kill ovarian cancer cells. Flow cytometric analysis (nnexin V) revealed increased cellular apoptosis for Co(OH)₂ NS than cobalt acetate (the precursor). Tracking experiments demonstrated that Co(OH)₂ NS are internalized through the lysosome pathway, although relocalization in the cytoplasm has been observed. Hence, Co(OH)₂ NS could be an effective self-therapeutic drug and open up an area for the optimization of self-therapeutic properties of cobalt nanomaterials for cancer treatment.

Development of Pin1 Inhibitors and their Potential as Therapeutic Agents

The prolyl isomerase Pin1 is a unique enzyme, which isomerizes the cis-trans conformation between pSer/pThr and proline and thereby regulates the function, stability and/or subcellular distribution of its target proteins. Such regulations by Pin1 are involved in numerous physiological functions as well as the pathogenic mechanisms underlying various diseases. Notably, Pin1 deficiency or inactivation is a potential cause of Alzheimer's disease, since Pin1 induces the degradation of Tau. In contrast, Pin1 overexpression is highly correlated with the degree of malignancy of cancers, as Pin1 controls a number of oncogenes and tumor suppressors. Accordingly, Pin1 inhibitors as anti-cancer drugs have been developed. Interestingly, recent intensive studies have demonstrated Pin1 to be responsible for the onset or development of nonalcoholic steatosis, obesity, atherosclerosis, lung fibrosis, heart failure and so on, all of which have been experimentally induced in Pin1 deficient mice. In this review, we discuss the possible applications of Pin1 inhibitors to a variety of diseases including malignant tumors and also introduce the recent advances in Pin1 inhibitor research, which have been reported.

Molecular crosstalk between cancer and neurodegenerative diseases

The progression of cancers and neurodegenerative disorders is largely defined by a set of molecular determinants that are either complementarily deregulated, or share remarkably overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the progression of both diseases. In this review, we particularly discuss our current knowledge on p53, cyclin D, cyclin E, cyclin F, Pin1 and protein phosphatase 2A, and their implications in the shared or distinct pathways that lead to cancers or neurodegenerative diseases. In addition, we focus on the inter-dependent regulation of brain cancers and neurodegeneration, mediated by intercellular communication between tumor and neuronal cells in the brain through the extracellular microenvironment. Finally, we shed light on the therapeutic perspectives for the treatment of both cancer and neurodegenerative disorders.

Identification of a potent and selective covalent Pin1 inhibitor

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is commonly overexpressed in human cancers, including pancreatic ductal adenocarcinoma (PDAC). While Pin1 is dispensable for viability in mice, it is required for activated Ras to induce tumorigenesis, suggesting a role for Pin1 inhibitors in Ras-driven tumors, such as PDAC. We report the development of rationally designed peptide inhibitors that covalently target Cys113, a highly conserved cysteine located in the Pin1 active site. The inhibitors were iteratively optimized for potency, selectivity, and cell permeability to give BJP-06–005-3, a versatile tool compound with which to probe Pin1 biology and interrogate its role in cancer. In parallel to inhibitor development, we employed genetic and chemical-genetic strategies to assess the consequences of Pin1 loss in human PDAC cell lines. We demonstrate that Pin1 cooperates with mutant KRAS to promote transformation in PDAC, and that Pin1 inhibition impairs cell viability over time in PDAC cell lines.

Prolyl isomerase Pin1 in metabolic reprogramming of cancer cells

Pin1 is one member of a group consisting of three prolyl isomerases. Pin1 interacts with the motif containing phospho-Ser/Thr-Pro of substrates and enhances cis-trans isomerization of peptide bonds, thereby controlling the functions of these substrates. Importantly, the Pin1 expression level is highly upregulated in most cancer cells and correlates with malignant properties, and thereby with poor outcomes. In addition, Pin1 was revealed to promote the functions of multiple oncogenes and to abrogate tumor suppressors. Accordingly, Pin1 is well recognized as a master regulator of malignant processes. Recent studies have shown that Pin1 also binds to a variety of metabolic regulators, such as AMP-activated protein kinase, acetyl CoA carboxylase and pyruvate kinase2, indicating Pin1 to have major impacts on lipid and glucose metabolism in cancer cells. In this review, we focus on the roles of Pin1 in metabolic reprogramming, such as "Warburg effects", of cancer cells. Our aim is to introduce these important roles of Pin1, as well as to present evidence supporting the possibility of Pin1 inhibition as a novel anti-cancer strategy.

Strategies for Delivery of siRNAs to Ovarian Cancer Cells

The unmet need for novel therapeutic options for ovarian cancer (OC) deserves further investigation. Among the different novel drugs, small interfering RNAs (siRNAs) are particularly attractive because of their specificity of action and efficacy, as documented in many experimental setups. However, the fragility of these molecules in the biological environment necessitates the use of delivery materials able to protect them and possibly target them to the cancer cells. Among the different delivery materials, those based on polymers and lipids are considered very interesting because of their biocompatibility and ability to carry/deliver siRNAs. Despite these features, polymers and lipids need to be engineered to optimize their delivery properties for OC. In this review, we concentrated on the description of the therapeutic potential of siRNAs and polymer-/lipid-based delivery systems for OC. After a brief description of OC and siRNA features, we summarized the strategies employed to minimize siRNA delivery problems, the targeting strategies to OC, and the preclinical models available. Finally, we discussed the most interesting works published in the last three years about polymer-/lipid-based materials for siRNA delivery.

Virtual screening identifies a PIN1 inhibitor with possible antiovarian cancer effects

Peptidyl-prolyl cis-trans isomerase, NIMA-interacting 1 (PIN1) is a peptidyl-prolyl isomerase that binds phospho-Ser/Thr-Pro motifs in proteins and catalyzes the cis-trans isomerization of proline peptide bonds. PIN1 is overexpressed in several cancers including high-grade serous ovarian cancer. Since few therapies are effective against this cancer, PIN1 could be a therapeutic target but effective PIN1 inhibitors are lacking. To identify molecules with in vivo inhibitory effects on PIN1, we used consensus docking to model existing PIN1-ligand X-ray structures and to screen a chemical database for candidate inhibitors. Ten molecules were selected and tested in cellular assays, leading to the identification of VS10 that bound and inhibited PIN1. VS10 treatment reduced the viability of ovarian cancer cell lines by inducing proteasomal PIN1 degradation, without effects on PIN1 transcription, and also reduced the levels of downstream targets β-catenin, cyclin D1, and pSer473-Akt. VS10 is a selective PIN1 inhibitor that may offer new opportunities for treating PIN1-overexpressing tumors.

First-of-its-kind STARD3 Inhibitor: In Silico Identification and Biological Evaluation as Anticancer Agent

STARD3 is a cellular protein that represents an attractive target for cancer therapy, being overexpressed in breast cancer and implied in the development of colorectal, gastric, and prostate cancers. Unfortunately, no STARD3 inhibitor has been identified yet. In this work, an in silico strategy was applied to predict a reliable binding mode of cholesterol into STARD3 and to develop a pharmacophore-based virtual screening protocol that allowed the identification of the first STARD3 inhibitor ever reported. The identified compound VS1 binds STARD3 with micromolar affinity (IC₅₀ = 35 μM) and shows antiproliferative activity in breast (MCF7 and MDA- MB-231) and colon (HCT-116) cancer cell lines in the same concentration range (IC₅₀ = 49.7-105.5 μM). Although VS1 has a moderate potency, we demonstrated that it specifically targets STARD3 in the cells and induces its degradation. Overall, the results confirm the reliability of the computational strategies herein applied and the identification of the first hit compound for the development of novel potent STARD3 inhibitors.

Structure-Based Design of Novel Benzimidazole Derivatives as Pin1 Inhibitors

Peptidyl-prolyl cis/trans isomerase Pin1 plays a key role in amplifying and translating multiple oncogenic signaling pathways during oncogenesis. The blockade of Pin1 provided a unique way of disrupting multiple oncogenic pathways and inducing apoptosis. Aiming to develop potent Pin1 inhibitors, a series of benzimidazole derivatives were designed and synthesized. Among the derivatives, compounds 6h and 13g showed the most potent Pin1 inhibitory activity with IC₅₀ values of 0.64 and 0.37 μM, respectively. In vitro antiproliferative assay demonstrated that compounds 6d, 6g, 6h, 6n, 6o and 7c exhibited moderate antiproliferative activity against human prostate cancer PC-3 cells. Taken together, these unique benzimidazole derivatives exhibited great potential to be further explored as potent Pin1 inhibitors with improved potency.

Oncogenic Hijacking of the PIN1 Signaling Network

Cellular choices are determined by developmental and environmental stimuli through integrated signal transduction pathways. These critically depend on attainment of proper activation levels that in turn rely on post-translational modifications (PTMs) of single pathway members. Among these PTMs, post-phosphorylation prolyl-isomerization mediated by PIN1 represents a unique mechanism of spatial, temporal and quantitative control of signal transduction. Indeed PIN1 was shown to be crucial for determining activation levels of several pathways and biological outcomes downstream to a plethora of stimuli. Of note, studies performed in different model organisms and humans have shown that hormonal, nutrient, and oncogenic stimuli simultaneously affect both PIN1 activity and the pathways that depend on PIN1-mediated prolyl-isomerization, suggesting the existence of evolutionarily conserved molecular circuitries centered on this isomerase. This review focuses on molecular mechanisms and cellular processes like proliferation, metabolism, and stem cell fate, that are regulated by PIN1 in physiological conditions, discussing how these are subverted in and hijacked by cancer cells. Current status and open questions regarding the use of PIN1 as biomarker and target for cancer therapy as well as clinical development of PIN1 inhibitors are also addressed.

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 as a molecular target in breast cancer: a therapeutic perspective of gynecological cancer

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (PIN1) induces conformational and functional changes to numerous key signaling molecules following proline-directed phosphorylation and its deregulation contributes to disease, particularly cancer. PIN1 is overexpressed in breast cancer, promoting cell proliferation and transformation in collaboration with several oncogenic signaling pathways, and is correlated with a poor clinical outcome. PIN1 level is also increased in certain gynecological cancers such as cervical, ovarian, and endometrial cancers. Although women with breast cancer are at risk of developing a second primary gynecological malignancy, particularly of the endometrium and ovary, the common oncogenic signaling pathway mediated by PIN1 has not been noted to date. This review discusses the roles of PIN1 in breast tumorigenesis and gynecological cancer progression, as well as the clinical effect of targeting this enzyme in breast and gynecological cancers.

A Guide to PIN1 Function and Mutations Across Cancers

PIN1 is a member of a family of peptidylprolyl isomerases that bind phosphoproteins and catalyze the rapid cis-trans isomerization of proline peptidyl bonds, resulting in an alteration of protein structure, function, and stability. PIN1 is overexpressed in human cancers, suggesting it promotes tumorigenesis, but depending on the cellular context, it also acts as a tumor suppressor. Here, we review the role of PIN1 in cancer and the regulation of PIN1 expression, and catalog the single nucleotide polymorphisms, and mutations in PIN1 gene associated with cancer. In addition, we provide a 3D model of the protein to localize the mutated residues.

PIN1 in Cell Cycle Control and Cancer

Cell cycle progression is tightly controlled by many cell cycle-regulatory proteins that are in turn regulated by a family of cyclin-dependent kinases (CDKs) through protein phosphorylation. The peptidyl-prolyl cis/trans isomerase PIN1 provides a further post-phosphorylation modification and functional regulation of these CDK-phosphorylated proteins. PIN1 specifically binds the phosphorylated serine or threonine residue preceding a proline (pSer/Thr-Pro) motif of its target proteins and catalyzes the cis/trans isomerization on the pSer/Thr-Pro peptide bonds. Through this phosphorylation-dependent prolyl isomerization, PIN1 fine-tunes the functions of various cell cycle-regulatory proteins including retinoblastoma protein (Rb), cyclin D1, cyclin E, p27, Cdc25C, and Wee1. In this review, we discussed the essential roles of PIN1 in regulating cell cycle progression through modulating the functions of these cell cycle-regulatory proteins. Furthermore, the mechanisms underlying PIN1 overexpression in cancers were also explored. Finally, we examined and summarized the therapeutic potential of PIN1 inhibitors in cancer therapy.

Gears-In-Motion: The Interplay of WW and PPIase Domains in Pin1

Pin1 belongs to the family of the peptidyl-prolyl cis-trans isomerase (PPIase), which is a class of enzymes that catalyze the cis/trans isomerization of the Proline residue. Pin1 is unique and only catalyzes the phosphorylated Serine/Threonine-Proline (S/T-P) motifs of a subset of proteins. Since the discovery of Pin1 as a key protein in cell cycle regulation, it has been implicated in numerous diseases, ranging from cancer to neurodegenerative diseases. The main features of Pin1 lies in its two main domains: the WW (two conserved tryptophan) domain and the PPIase domain. Despite extensive studies trying to understand the mechanisms of Pin1 functions, how these two domains contribute to the biological roles of Pin1 in cellular signaling requires more investigations. The WW domain of Pin1 is known to have a higher affinity to its substrate than that of the PPIase domain. Yet, the WW domain seems to prefer the trans configuration of phosphorylated S/T-P motif, while the PPIase catalyzes the cis to trans isomerasion. Such contradicting information has generated much confusion as to the actual mechanism of Pin1 function. In addition, dynamic allostery has been suggested to be important for Pin1 function. Henceforth, in this review, we will be looking at the progress made in understanding the function of Pin1, and how these understandings can aid us in overcoming the diseases implicated by Pin1 such as cancer during drug development.