Knockdown of the prolyl isomerase Pin1 inhibits Hep-2 cell growth, migration, and invasion by targeting the β-catenin signaling pathway

Stress Activated MAP Kinases and Cyclin-Dependent Kinase 5 Mediate Nuclear Translocation of Nrf2 via Hsp90α-Pin1-Dynein Motor Transport Machinery

Non-lethal low levels of oxidative stress leads to rapid activation of the transcription factor nuclear factor-E2-related factor 2 (Nrf2), which upregulates the expression of genes important for detoxification, glutathione synthesis, and defense against oxidative damage. Stress-activated MAP kinases p38, ERK, and JNK cooperate in the efficient nuclear accumulation of Nrf2 in a cell-type-dependent manner. Activation of p38 induces membrane trafficking of a glutathione sensor neutral sphingomyelinase 2, which generates ceramide upon depletion of cellular glutathione. We previously proposed that caveolin-1 in lipid rafts provides a signaling hub for the phosphorylation of Nrf2 by ceramide-activated PKCζ and casein kinase 2 to stabilize Nrf2 and mask a nuclear export signal. We further propose a mechanism of facilitated Nrf2 nuclear translocation by ERK and JNK. ERK and JNK phosphorylation of Nrf2 induces the association of prolyl cis/trans isomerase Pin1, which specifically recognizes phosphorylated serine or threonine immediately preceding a proline residue. Pin1-induced structural changes allow importin-α5 to associate with Nrf2. Pin1 is a co-chaperone of Hsp90α and mediates the association of the Nrf2-Pin1-Hsp90α complex with the dynein motor complex, which is involved in transporting the signaling complex to the nucleus along microtubules. In addition to ERK and JNK, cyclin-dependent kinase 5 could phosphorylate Nrf2 and mediate the transport of Nrf2 to the nucleus via the Pin1-Hsp90α system. Some other ERK target proteins, such as pyruvate kinase M2 and hypoxia-inducible transcription factor-1, are also transported to the nucleus via the Pin1-Hsp90α system to modulate gene expression and energy metabolism. Notably, as malignant tumors often express enhanced Pin1-Hsp90α signaling pathways, this provides a potential therapeutic target for tumors.

Prognostic value of peptidyl-prolyl cis-trans isomerase 1 (PIN1) in human malignant tumors

BACKGROUND

PIN1, a peptidyl-prolyl cis-trans isomerase, specifically can regulate phosphorylation of proteins on serine/threonine residues that precede proline and has critical roles in cell proliferation and transformation. Many studies have revealed that overexpression of PIN1 is involved in the malignant biological behavior of various cancers, but to date, no meta-analyses have evaluated PIN1 clinical and prognostic value in patients with malignant tumors.

METHODS

We retrieved related articles from PubMed, Web of Science and Scopus databases up to April 20, 2019. Pooled odds ratios (ORs) and hazard ratios (HRs) with 95% CIs were used to estimate the correlation of PIN1 expression with clinicopathological characteristics and survival outcomes. The methodology was according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Cochrane Collaboration guidelines.

RESULTS

A total of 20 studies containing 2574 patients with various tumors were included in this analysis. Pooled results showed that PIN1 overexpression was significantly associated with the advanced clinical stages of cancer (OR = 1.37, 95% CI 1.06-1.78), positive lymph node metastasis (OR = 1.65, 95% CI 1.15-2.37) and poor prognosis (HR = 2.40, 95% CI 1.55-3.74), although no correlation with poor differentiation was found.

CONCLUSIONS

These results suggest that high expression of PIN1 can be considered as a risk factor for progression and invasion of malignant tumors and thus may serve as a promising therapeutic target and prognostic biomarker for human solid tumors.

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.