Targeting Pin1 renders pancreatic cancer eradicable by synergizing with immunochemotherapy.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by notorious resistance to current therapies attributed to inherent tumor heterogeneity and highly desmoplastic and immunosuppressive tumor microenvironment (TME). Unique proline isomerase Pin1 regulates multiple cancer pathways, but its role in the TME and cancer immunotherapy is unknown. Here, we find that Pin1 is overexpressed both in cancer cells and cancer-associated fibroblasts (CAFs) and correlates with poor survival in PDAC patients. Targeting Pin1 using clinically available drugs induces complete elimination or sustained remissions of aggressive PDAC by synergizing with anti-PD-1 and gemcitabine in diverse model systems. Mechanistically, Pin1 drives the desmoplastic and immunosuppressive TME by acting on CAFs and induces lysosomal degradation of the PD-1 ligand PD-L1 and the gemcitabine transporter ENT1 in cancer cells, besides activating multiple cancer pathways. Thus, Pin1 inhibition simultaneously blocks multiple cancer pathways, disrupts the desmoplastic and immunosuppressive TME, and upregulates PD-L1 and ENT1, rendering PDAC eradicable by immunochemotherapy.

Proline isomer-specific antibodies reveal the early pathogenic tau conformation in Alzheimer's disease.

cis-trans isomerization of proteins phosphorylated by proline-directed kinases is proposed to control numerous signaling molecules and is implicated in the pathogenesis of Alzheimer's and other diseases. However, there is no direct evidence for the existence of cis-trans protein isomers in vivo or for their conformation-specific function or regulation. Here we develop peptide chemistries that allow the generation of cis- and trans-specific antibodies and use them to raise antibodies specific for isomers of phosphorylated tau. cis, but not trans, p-tau appears early in the brains of humans with mild cognitive impairment, accumulates exclusively in degenerated neurons, and localizes to dystrophic neurites during Alzheimer's progression. Unlike trans p-tau, the cis isomer cannot promote microtubule assembly, is more resistant to dephosphorylation and degradation, and is more prone to aggregation. Pin1 converts cis to trans p-tau to prevent Alzheimer's tau pathology. Isomer-specific antibodies and vaccines may therefore have value for the early diagnosis and treatment of Alzheimer's disease.

Function and regulation of cis P-tau in the pathogenesis and treatment of conventional and nonconventional tauopathies.

Conventional tauopathies are a group of disease characterized by tau inclusions in the brains, including Alzheimer's disease (AD), Pick's disease (PiD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and certain types of frontotemporal dementia (FTD), among which AD is the most prevalent. Extensive post-translational modifications, especially hyperphosphorylation, and abnormal aggregation of tau protein underlie tauopathy. Cis-trans isomerization of protein plays an important role in protein folding, function, and degradation, which is regulated by peptidyl-proline isomerases (PPIases). Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1), the only PPIase found to isomerize Pro following phosphorylated Ser or Thr residues, alters phosphorylated tau protein conformation at pT231-P motif. The cis P-tau but not trans P-tau serves as an early driver of multiple neurodegenerative disease, encompassing AD, traumatic brain injury (TBI), chronic traumatic encephalopathy (CTE), and vascular contributions to cognitive impairment and dementia (VCID). Cis but not trans P-tau is resistant to protein dephosphorylation and degradation, and also prone to protein aggregation. Cis P-tau loses its ability to stabilize microtubule, causing and spreading tauopathy mainly in axons, a pathological process called cistauosis. The conformation-specific monoclonal antibody that targets only the cis P-tau serves as a very early diagnosis method and a potential treatment of not only conventional tauopathies but also nonconventional tauopathies such as VCID, with clinical trials ongoing. Notably, cis P-tau antibody is the only clinical-stage Alzheimer's therapeutic that has shown the efficacy in animal models of not only AD but also TBI and stroke, which are very early stages of dementia. Here we review the identification and pathological consequences of cis pt231-tau, the role of its regulator Pin1, as well as the clinical implication of cis pt231-tau conformation-specific antibody in conventional and nonconventional tauopathies.

Essential role for the prolyl isomerase Pin1 in Toll-like receptor signaling and type I interferon-mediated immunity.

Toll-like receptors (TLRs) shape innate and adaptive immunity to microorganisms. The enzyme IRAK1 transduces signals from TLRs, but mechanisms for its activation and regulation remain unknown. We found here that TLR7 and TLR9 activated the isomerase Pin1, which then bound to IRAK1; this resulted in activation of IRAK1 and facilitated its release from the receptor complex to activate the transcription factor IRF7 and induce type I interferons. Consequently, Pin1-deficient cells and mice failed to mount TLR-mediated, interferon-dependent innate and adaptive immune responses. Given the critical role of aberrant activation of IRAK1 and type I interferons in various immune diseases, controlling IRAK1 activation via inhibition of Pin1 may represent a useful therapeutic approach.

Sulfopin is a covalent inhibitor of Pin1 that blocks Myc-driven tumors in vivo.

The peptidyl-prolyl isomerase, Pin1, is exploited in cancer to activate oncogenes and inactivate tumor suppressors. However, despite considerable efforts, Pin1 has remained an elusive drug target. Here, we screened an electrophilic fragment library to identify covalent inhibitors targeting Pin1's active site Cys113, leading to the development of Sulfopin, a nanomolar Pin1 inhibitor. Sulfopin is highly selective, as validated by two independent chemoproteomics methods, achieves potent cellular and in vivo target engagement and phenocopies Pin1 genetic knockout. Pin1 inhibition had only a modest effect on cancer cell line viability. Nevertheless, Sulfopin induced downregulation of c-Myc target genes, reduced tumor progression and conferred survival benefit in murine and zebrafish models of MYCN-driven neuroblastoma, and in a murine model of pancreatic cancer. Our results demonstrate that Sulfopin is a chemical probe suitable for assessment of Pin1-dependent pharmacology in cells and in vivo, and that Pin1 warrants further investigation as a potential cancer drug target.

ATR Plays a Direct Antiapoptotic Role at Mitochondria, which Is Regulated by Prolyl Isomerase Pin1.

ATR, a PI3K-like protein kinase, plays a key role in regulating DNA damage responses. Its nuclear checkpoint kinase function is well documented, but little is known about its function outside the nucleus. Here we report that ATR has an antiapoptotic activity at mitochondria in response to UV damage, and this activity is independent of its hallmark checkpoint/kinase activity and partner ATRIP. ATR contains a BH3-like domain that allows ATR-tBid interaction at mitochondria, suppressing cytochrome c release and apoptosis. This mitochondrial activity of ATR is downregulated by Pin1 that isomerizes ATR from cis-isomer to trans-isomer at the phosphorylated Ser428-Pro429 motif. However, UV inactivates Pin1 via DAPK1, stabilizing the pro-survival cis-isomeric ATR. In contrast, nuclear ATR remains in the trans-isoform disregarding UV. This cytoplasmic response of ATR may provide a mechanism for the observed antiapoptotic role of ATR in suppressing carcinogenesis and its inhibition in sensitizing anticancer agents for killing of cancer cells.

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.

The Pin1-CaMKII-AMPA Receptor Axis Regulates Epileptic Susceptibility.

Pin1 is a unique isomerase that regulates protein conformation and function after phosphorylation. Pin1 aberration contributes to some neurological diseases, notably Alzheimer's disease, but its role in epilepsy is not fully understood. We found that Pin1-deficient mice had significantly increased seizure susceptibility in multiple chemical inducing models and developed age-dependent spontaneous epilepsy. Electrophysiologically, Pin1 ablation enhanced excitatory synaptic transmission to prefrontal cortex (PFC) pyramidal neurons without affecting their intrinsic excitability. Biochemically, Pin1 ablation upregulated AMPA receptors and GluA1 phosphorylation by acting on phosphorylated CaMKII. Clinically, Pin1 was decreased significantly, whereas phosphorylated CaMKII and GluA1 were increased in the neocortex of patients with epilepsy. Moreover, Pin1 expression restoration in the PFC of Pin1-deficient mice using viral gene transfer significantly reduced phosphorylated CaMKII and GluA1 and effectively suppressed their seizure susceptibility. Thus, Pin1-CaMKII-AMPA receptors are a novel axis controlling epileptic susceptibility, highlighting attractive new therapeutic strategies.

The Association Between Cancer and Spousal Rate of Memory Decline: A Negative Control Study to Evaluate (Unmeasured) Social Confounding of the Cancer-memory Relationship.

Cancer diagnoses are associated with better long-term memory in older adults, possibly reflecting a range of social confounders that increase cancer risk but improve memory. We used spouse's memory as a negative control outcome to evaluate this possible confounding, since spouses share social characteristics and environments, and individuals' cancers are unlikely to cause better memory among their spouses. We estimated the association of an individual's incident cancer diagnosis (exposure) with their own (primary outcome) and their spouse's (negative control outcome) memory decline in 3601 couples from 1998 to 2014 in the Health and Retirement Study, using linear mixed-effects models. Incident cancer predicted better long-term memory for the diagnosed individual. We observed no association between an individual's cancer diagnosis and rate of spousal memory decline. This negative control study suggests that the inverse association between incident cancer and rate of memory decline is unlikely to be attributable to social/behavioral factors shared between spouses.

Antibody against early driver of neurodegeneration cis P-tau blocks brain injury and tauopathy.

Traumatic brain injury (TBI), characterized by acute neurological dysfunction, is one of the best known environmental risk factors for chronic traumatic encephalopathy and Alzheimer's disease, the defining pathologic features of which include tauopathy made of phosphorylated tau protein (P-tau). However, tauopathy has not been detected in the early stages after TBI, and how TBI leads to tauopathy is unknown. Here we find robust cis P-tau pathology after TBI in humans and mice. After TBI in mice and stress in vitro, neurons acutely produce cis P-tau, which disrupts axonal microtubule networks and mitochondrial transport, spreads to other neurons, and leads to apoptosis. This process, which we term 'cistauosis', appears long before other tauopathy. Treating TBI mice with cis antibody blocks cistauosis, prevents tauopathy development and spread, and restores many TBI-related structural and functional sequelae. Thus, cis P-tau is a major early driver of disease after TBI and leads to tauopathy in chronic traumatic encephalopathy and Alzheimer's disease. The cis antibody may be further developed to detect and treat TBI, and prevent progressive neurodegeneration after injury.

Melatonin directly binds and inhibits death-associated protein kinase 1 function in Alzheimer's disease.

Death-associated protein kinase 1 (DAPK1) is upregulated in the brains of human Alzheimer's disease (AD) patients compared with normal subjects, and aberrant DAPK1 regulation is implicated in the development of AD. However, little is known about whether and how DAPK1 function is regulated in AD. Here, we identified melatonin as a critical regulator of DAPK1 levels and function. Melatonin significantly decreases DAPK1 expression in a post-transcriptional manner in neuronal cell lines and mouse primary cortical neurons. Moreover, melatonin directly binds to DAPK1 and promotes its ubiquitination, resulting in increased DAPK1 protein degradation through a proteasome-dependent pathway. Furthermore, in tau-overexpressing mouse brain slices, melatonin treatment and the inhibition of DAPK1 kinase activity synergistically decrease tau phosphorylation at multiple sites related to AD. In addition, melatonin and DAPK1 inhibitor dramatically accelerate neurite outgrowth and increase the assembly of microtubules. Mechanistically, melatonin-mediated DAPK1 degradation increases the activity of Pin1, a prolyl isomerase known to play a protective role against tau hyperphosphorylation and tau-related pathologies. Finally, elevated DAPK1 expression shows a strong correlation with the decrease in melatonin levels in human AD brains. Combined, these results suggest that DAPK1 regulation by melatonin is a novel mechanism that controls tau phosphorylation and function and offers new therapeutic options for treating human AD.

Cell-cycle-regulated activation of Akt kinase by phosphorylation at its carboxyl terminus.

Akt, also known as protein kinase B, plays key roles in cell proliferation, survival and metabolism. Akt hyperactivation contributes to many pathophysiological conditions, including human cancers, and is closely associated with poor prognosis and chemo- or radiotherapeutic resistance. Phosphorylation of Akt at S473 (ref. 5) and T308 (ref. 6) activates Akt. However, it remains unclear whether further mechanisms account for full Akt activation, and whether Akt hyperactivation is linked to misregulated cell cycle progression, another cancer hallmark. Here we report that Akt activity fluctuates across the cell cycle, mirroring cyclin A expression. Mechanistically, phosphorylation of S477 and T479 at the Akt extreme carboxy terminus by cyclin-dependent kinase 2 (Cdk2)/cyclin A or mTORC2, under distinct physiological conditions, promotes Akt activation through facilitating, or functionally compensating for, S473 phosphorylation. Furthermore, deletion of the cyclin A2 allele in the mouse olfactory bulb leads to reduced S477/T479 phosphorylation and elevated cellular apoptosis. Notably, cyclin A2-deletion-induced cellular apoptosis in mouse embryonic stem cells is partly rescued by S477D/T479E-Akt1, supporting a physiological role for cyclin A2 in governing Akt activation. Together, the results of our study show Akt S477/T479 phosphorylation to be an essential layer of the Akt activation mechanism to regulate its physiological functions, thereby providing a new mechanistic link between aberrant cell cycle progression and Akt hyperactivation in cancer.

Negative regulation of the stability and tumor suppressor function of Fbw7 by the Pin1 prolyl isomerase.

Fbw7 is the substrate recognition component of the Skp1-Cullin-F-box (SCF)-type E3 ligase complex and a well-characterized tumor suppressor that targets numerous oncoproteins for destruction. Genomic deletion or mutation of FBW7 has been frequently found in various types of human cancers; however, little is known about the upstream signaling pathway(s) governing Fbw7 stability and cellular functions. Here we report that Fbw7 protein destruction and tumor suppressor function are negatively regulated by the prolyl isomerase Pin1. Pin1 interacts with Fbw7 in a phoshorylation-dependent manner and promotes Fbw7 self-ubiquitination and protein degradation by disrupting Fbw7 dimerization. Consequently, overexpressing Pin1 reduces Fbw7 abundance and suppresses Fbw7's ability to inhibit proliferation and transformation. By contrast, depletion of Pin1 in cancer cells leads to elevated Fbw7 expression, which subsequently reduces Mcl-1 abundance, sensitizing cancer cells to Taxol. Thus, Pin1-mediated inhibition of Fbw7 contributes to oncogenesis, and Pin1 may be a promising drug target for anticancer therapy.

Targeting PIN1 exerts potent antitumor activity in pancreatic ductal carcinoma via inhibiting tumor metastasis.

The human prolyl isomerase PIN1, best known for its association with carcinogenesis, has recently been indicated in the disease of pancreatic ductal adenocarcinoma (PDAC). However, the functions of PIN1 and the feasibility of targeting PIN1 in PDAC remain elusive. For this purpose, we examined the expression of PIN1 in cancer, related paracarcinoma and metastatic cancer tissues by immunohistochemistry and analyzed the associations with the pathogenesis of PDAC in 173 patients. The functional roles of PIN1 in PDAC were explored in vitro and in vivo using both genetic and chemical PIN1 inhibition. We showed that PIN1 was upregulated in pancreatic cancer and metastatic tissues. High PIN1 expression is significantly association with poor clinicopathological features and shorter overall survival and disease-free survival. Further stratified analysis showed that PIN1 phenotypes refined prognostication in PDAC. Inhibition of PIN1 expression with RNA interference or with all trans retinoic acid decreased not only the growth but also the migration and invasion of PDAC cells through regulating the key molecules of multiple cancer-driving pathways, simultaneously resulting in cell cycle arrest and mesenchymal-epithelial transition in vitro. Furthermore, genetic and chemical PIN1 ablation showed dramatic inhibition of the tumorigenesis and metastatic spread and then reduced the tumor burden in vivo. We provided further evidence for the use of PIN1 as a promising therapeutic target in PDAC. Genetic and chemical PIN1 ablation exerted potent antitumor effects through blocking multiple cancer-driving pathways in PDAC. More potent and specific PIN1 targeted inhibitors could be exploited to treat this aggressive cancer.

Pin1 inhibition potently suppresses gastric cancer growth and blocks PI3K/AKT and Wnt/ß-catenin oncogenic pathways.

Gastric cancer is the second leading cause of cancer-related mortality and the fourth most common cancer globally. High intratumor heterogeneity of advanced gastric cancer poses great challenges to targeted therapy due to simultaneous activation of many redundant cancer-driving pathways. A central common signaling mechanism in cancer is proline-directed phosphorylation, which is further regulated by the unique proline isomerase Pin1. Pin1 inhibition exerts anticancer activity by blocking multiple cancer-driving pathways in some cancers, but its role in gastric cancer is not fully understood. Here we detected Pin1 protein expression in 1065 gastric cancer patients and paired normal tissues using immunohistochemistry and Western blot, and then examined the effects of Pin1 overexpression, and genetic and chemical Pin1 inhibition using Pin1 short hairpin RNA or small molecule inhibitor all-trans retinoic acid (ATRA) on tumorigenesis of human gastric cancer in vitro and in vivo, followed by biochemical analyses to elucidate Pin1 regulated oncogenic pathways. We found that Pin1 was significantly overexpressed in primary and metastasized tumors, with Pin1 overexpression being correlated with advanced stage and poor prognosis. Furthermore, whereas Pin1 overexpression promoted the transformed phenotype in immortalized and nontransformed human gastric cells, either genetic or chemical Pin1 inhibition in multiple human gastric cancer cells potently suppressed cell growth, G1/S transition and colony formation in vitro, as well as tumor growth in xenograft tumor models in vivo, which were further supported by downregulation of multiple key oncoproteins in PI3K/AKT and Wnt/ß-catenin signaling pathways. These results not only provide the first evidence for a critical role of Pin1 in the tumorigenesis of gastric cancer but also suggest that targeting Pin1 using ATRA or other inhibitors offers an effective new therapeutic approach for treating advanced gastric cancer.

The prolyl isomerase PIN1: a pivotal new twist in phosphorylation signalling and disease.

Protein phosphorylation regulates many cellular processes by causing changes in protein conformation. The prolyl isomerase PIN1 has been identified as a regulator of phosphorylation signalling that catalyses the conversion of specific phosphorylated motifs between the two completely distinct conformations in a subset of proteins. PIN1 regulates diverse cellular processes, including growth-signal responses, cell-cycle progression, cellular stress responses, neuronal function and immune responses. In line with the diverse physiological roles of PIN1, it has also been linked to several diseases that include cancer, Alzheimer's disease and asthma, and thus it might represent a novel therapeutic target.

Death-associated protein kinase 1 phosphorylates Pin1 and inhibits its prolyl isomerase activity and cellular function.

Pin1 is a phospho-specific prolyl isomerase that regulates numerous key signaling molecules and whose deregulation contributes to disease notably cancer. However, since prolyl isomerases are often believed to be constitutively active, little is known whether and how Pin1 catalytic activity is regulated. Here, we identify death-associated protein kinase 1 (DAPK1), a known tumor suppressor, as a kinase responsible for phosphorylation of Pin1 on Ser71 in the catalytic active site. Such phosphorylation fully inactivates Pin1 catalytic activity and inhibits its nuclear location. Moreover, DAPK1 inhibits the ability of Pin1 to induce centrosome amplification and cell transformation. Finally, Pin1 pSer71 levels are positively correlated with DAPK1 levels and negatively with centrosome amplification in human breast cancer. Thus, phosphorylation of Pin1 Ser71 by DAPK1 inhibits its catalytic activity and cellular function, providing strong evidence for an essential role of the Pin1 enzymatic activity for its cellular function.

Critical role of XBP1 in cancer signalling is regulated by PIN1.

XBP1 (X-box-binding protein 1) is activated in cancer and has a pivotal role in tumorigenesis and progression of human cancer. In particular, the XBP1 transcriptional regulatory network is well known to drive cancer development, but little is known about whether the stability of XBP1 is regulated and, if so, what controls the stability of XBP1. In the present study we show that PIN1 prolyl isomerase interacts with the active form of XBP1 (XBP1s) in a phosphorylation-dependent manner and promotes XBP1s-induced cell proliferation and transformation through the regulation of XBP1 stability. By contrast, depletion of Pin1 in cancer cells reduced XBP1s expression, which subsequently inhibits cell proliferation and transformation. Interestingly, XBP1s activates multiple oncogenic pathways including NF-κB (nuclear factor κB), AP1 (activator protein 1) and Myc, and down-regulates PIN1 transcription via a negative-feedback mechanism through p53 induction. Ultimately, reciprocal regulation of Pin1 and XBP1s is associated with the activation of oncogenic pathways, and the relationship of PIN1 and XBP1 may be an attractive target for novel therapy in cancers.

Association of cancer and Alzheimer's disease risk in a national cohort of veterans.

INTRODUCTION: To examine the risk of Alzheimer's disease (AD) among cancer survivors in a national database. METHODS: Retrospective cohort of 3,499,378 mostly male US veterans aged ≥65 years were followed between 1996 and 2011. We used Cox models to estimate risk of AD and alternative outcomes (non-AD dementia, osteoarthritis, stroke, and macular degeneration) in veterans with and without a history of cancer. RESULTS: Survivors of a wide variety of cancers had modestly lower AD risk, but increased risk of the alternative outcomes. Survivors of screened cancers, including prostate cancer, had a slightly increased AD risk. Cancer treatment was independently associated with decreased AD risk; those who received chemotherapy had a lower risk than those who did not. DISCUSSION: Survivors of some cancers have a lower risk of AD but not other age-related conditions, arguing that lower AD diagnosis is not simply due to bias. Cancer treatment may be associated with decreased risk of AD.