The correlation of genetic instability of PINX1 gene to clinico-pathological features of gastric cancer in the Chinese population

PinX1 plays multifaceted roles in human cancers: a review and perspectives

BACKGROUND

Pin2/TRF1 interacting protein X1 (PinX1), a telomerase inhibitor, is located at human chromosome 8p23. This region is important for telomere length maintenance and chromosome stability, both of which are essential for regulating human ageing and associated diseases.

METHODS AND RESULTS

We investigated the research progress of PinX1 in human cancers. In cancers, the expression levels of PinX1 mRNA and protein vary according to cancer cell types, and PinX1 plays a critical role in the regulation of cancer development and progression. Additionally, a review of the literature indicates that PinX1 is involved in mitosis and affects the sensitivity of cancer cells to radiation-induced DNA damage. Therefore, PinX1 has therapeutic potential for cancer, and understanding the function of PinX1 in the regulation of cancers is crucial for improving treatment. In this review, we discuss the expression level of PinX1 in a variety of cancers and how it affects the implicated pathways. Additionally, we outline the function of PinX1 in cancer cells and provide a theoretical basis for PinX1-related cancer therapy.

CONCLUSIONS

PinX1 has promising prospects in future cancer therapeutics. This review may provide theoretical support for researchers in this field.

Prognostic and Clinicopathological Value of PINX1 in Various Human Tumors: A Meta-Analysis

PINX1 (Pin2/TRF1 interacting protein X1, an intrinsic telomerase inhibitor and putative tumor suppressor gene) may represent a novel prognostic tumor biomarker. However, the results of previous studies are inconsistent and the prognostic value of PINX1 remains controversial. Therefore, we conducted a meta-analysis to determine whether PINX1 expression is associated with overall survival (OS), disease-specific survival (DSS), disease-free survival (DFS), recurrence-free survival (RFS), and clinicopathological characteristics in patients with malignant tumors. A systematic search was performed in the PubMed, Web of Science, and Embase databases in April 2018. Quality assessment was performed according to the modified Newcastle-Ottawa Scale. Pooled odds ratios (ORs) and hazard ratios (HRs) with 95.0% confidence intervals (CIs) were calculated to determine the relationship between PINX1 expression and OS, DSS, DFS/RFS, and clinicopathological characteristics. Due to the heterogeneity across the included studies, subgroup and sensitivity analyses were performed. Fixed-effects models were used when the heterogeneity was not significant and random-effects models were used when the heterogeneity was significant. Fourteen studies of 16 cohorts including 2,624 patients were enrolled. Low PINX1 expression was associated with poor OS (HR: 1.51, 95.0% CI: 1.03-2.20; P = 0.035) and DFS/RFS (HR: 1.78, 95.0% CI: 1.28-2.47; P = 0.001) but not DSS (HR: 0.80, 95.0% CI: 0.38-1.67; P = 0.548). Low PINX1 expression was also associated with lymphatic invasion (OR: 2.23, 95.0% CI: 1.35-3.70; P = 0.002) and advanced tumor-node-metastasis stage (OR: 2.43, 95.0% CI: 1.29-4.57; P = 0.006). No significant associations were observed between low PINX1 expression and sex, depth of invasion, grade of differentiation, and distant metastasis. Low PINX1 expression was associated with poor OS and DFS/RFS and lymphatic invasion and advanced tumor-node-metastasis stage, suggesting that PINX1 expression may be a useful predictor of prognosis in patients with malignant tumors.

Efficient expression of recombinant human telomerase inhibitor 1 (hPinX1) in Pichia pastoris

PinX1 encoded by a remarkable tumor suppressor gene and located in human chromosome 8p23 is known as telomerase inhibitor. In recent years, this protein has been of interest as clinically tumor suppressor. Pichia pastoris expression system is preferred to produce heterologous proteins and is suitable for industrial and research purposes. In the present study, human PinX1 gene (hPinX1) was cloned in E. coli One Shot TOP10 cells and overexpressed in P. pastoris strain X-33 intracellularly, using a strong AOX (alcohol oxidase) promoter. The recombinant cells were grown in shaking flask. Induction time, methanol concentration and initial pH were optimized for obtaining high levels of hPinX1 protein production. Recombinant protein production was confirmed by Western blot analysis and the relative expression levels of rhPinX1 were quantified. According to Western blot analysis, molecular mass of produced hPinX1 was determined as 47.5 kDa. At the end of optimization studies, the best fermentation conditions were determined as induction time 48 h, methanol concentration 3% and initial culture pH 5.0. This process would be an applicable way for obtaining recombinant hPinX1 using P. pastoris expression system. This is the first report on recombinant production of hPinX1 in P. pastoris.

PinX1: structure, regulation and its functions in cancer

PIN2/TRF1-interacting telomerase inhibitor 1 (PinX1) is a novel cloned gene located at human chromosome 8p23, playing a vital role in maintaining telomeres length and chromosome stability. It has been demonstrated to be involved in tumor genesis and progression in most malignancies. However, some researches showed opposing molecular status of PinX1 gene and its expression patterns in several other types of tumors. The pathogenic mechanism of PinX1 expression in human malignancy is not yet clear. Moreover, emerging evidence suggest that PinX1 (especially its TID domain) might be a potential new target cancer treatment. Therefore, PinX1 may be a new potential diagnostic biomarker and therapeutic target for human cancers, and may play different roles in different human cancers. The functions and the mechanisms of PinX1 in various human cancers remain unclear, suggesting the necessity of further extensive works of its role in tumor genesis and progression.

The depletion of PinX1 involved in the tumorigenesis of non-small cell lung cancer promotes cell proliferation via p15/cyclin D1 pathway

Background

The telomerase/telomere interacting protein PinX1 has been suggested as a tumor suppressor. However, the clinical and biological significance of PinX1 in human non-small cell lung cancer (NSCLC) is unclear.

Methods

PinX1 gene/expression pattern and its association with NSCLC patient survival were analyzed in cBioportal Web resource and two cohorts of NSCLC samples. A series of in vivo and in vitro assays were performed to elucidate the function of PinX1 on NSCLC cells proliferation and underlying mechanisms.

Results

More frequency of gene PinX1 homozygous deletion and heterozygote deficiency was first retrieved from cBioportal Web resource. Low expression of PinX1 correlated with smoking condition, histological type, T stage, N stage, M stage and TNM stage, and was an independent predictor for overall survival in a learning cohort (n = 93) and a validation cohort (n = 51) of NSCLC patients. Furthermore, knockdown of PinX1 dramatically accelerated NSCLC cell proliferation and G1/S transition, whereas ectopic overexpression of PinX1 substantially inhibited cell viability and cell cycle transition in vitro and in vivo. p15/cyclin D1 pathway and BMP5 might contribute to PinX1-associated cell proliferation and cell cycle transition.

Conclusion

The cost-effective expression of PinX1 could constitute a novel molecular predictor/marker for NSCLC management.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0637-4) contains supplementary material, which is available to authorized users.

PinX1 serves as a potential prognostic indicator for clear cell renal cell carcinoma and inhibits its invasion and metastasis by suppressing MMP-2 via NF-κB-dependent transcription

PIN2/TRF1-interacting telomerase inhibitor 1 (PinX1) is a novel cloned gene which has been identified as a major haploinsufficient tumor suppressor essential for maintaining telomerase activity, the length of telomerase and chromosome stability. This study explored the clinical significance and biological function of PinX1 in human clear cell renal cell carcinoma (ccRCC). The clinical relevance of PinX1 in ccRCC was evaluated using tissue microarray and immunohistochemical staining in two independent human ccRCC cohorts. Our data demonstrated that PinX1 expression was dramatically decreased in ccRCC tissues compared with normal renal tissues and paired adjacent non-tumor tissues. Low PinX1 expression was significantly correlated with depth of invasion, lymph node metastasis and advanced TNM stage in patients, as well as with worse overall and disease-specific survival. Cox regression analysis revealed that PinX1 expression was an independent prognostic factor for ccRCC patients. Moreover, PinX1 inhibited the migration and invasion of ccRCC by suppressing MMP-2 expression and activity via NF-κB-dependent transcription in vitro. In vivo studies confirmed that PinX1 negatively regulated ccRCC metastasis and the expression of MMP-2 and NF-κB-p65. These findings indicate that PinX1 suppresses ccRCC metastasis and may serve as a ccRCC candidate clinical prognostic marker and a potential therapeutic target.

PinX1 inhibits the invasion and metastasis of human breast cancer via suppressing NF-κB/MMP-9 signaling pathway

Background

PinX1 (PIN2/TRF1-interacting telomerase inhibitor 1) was suggested to be correlated with tumor progression. This study was designed to evaluate the role of PinX1 in human breast cancer.

Methods

To evaluate the function of PinX1 in breast cancer, we used a tissue microarray (TMA) of 405 human breast cancer patients and immunohistochemistry to analyze the correlation between PinX1 expression and clinicopathologic variables and patient survival. We also detected the abilities of cell migration and invasion in breast cancer by performing cell migration and invasion assay, gelatin zymography and western blot analysis. Lastly, we set up the nude mice model by Tail vein assay to exam the functional role of PinX1 in breast cancer metastasis.

Results

We found that low PinX1 expression was associated with lymph node metastasis (P = 0.002) and histology grade (P = 0.001) in patients, as well as with poorer overall and disease-specific survival (P = 0.010 and P = 0.003, respectively). Moreover, we identified that PinX1 inhibited the migration and invasion of breast cancer by suppressing MMP-9 expression and activity via NF-κB-dependent transcription in vitro. Finally, our mice model confirmed that PinX1 suppressed breast cancer metastasis in vivo.

Conclusions

Our data revealed that low PinX1 expression was an independent negative prognostic factor for breast cancer patients. These findings suggested that PinX1 might be function as a tumor metastasis suppressor in the development and progression of breast cancer by regulating the NF-κB/MMP-9 signaling pathway, and might be a prognostic marker as well as a therapeutic target for breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0332-2) contains supplementary material, which is available to authorized users.

PinX1 inhibits cell proliferation, migration and invasion in glioma cells

PinX1 induces apoptosis and suppresses cell proliferation in some cancer cells, and the expression of PinX1 is frequently decreased in some cancer and negatively associated with metastasis and prognosis. However, the precise roles of PinX1 in gliomas have not been studied. In this study, we found that PinX1 obviously reduced the gliomas cell proliferation through regulating the expressions of cell cycle-relative molecules to arrest cell at G1 phase and down-regulating the expression of component telomerase reverse transcriptase (hTERT in human), which is the hardcore of telomerase. Moreover, PinX1 could suppress the abilities of gliomas cell wound healing, migration and invasion via suppressing MMP-2 expression and increasing TIMP-2 expression. In conclusion, our results suggested that PinX1 may be a potential suppressive gene in the progression of gliomas.

Reduced expression of PinX1 correlates to progressive features in patients with prostate cancer

Background

Pin2/TRF1 binding protein X1 (PinX1) has been identified as an endogenous telomerase inhibitor and a major haploinsufficient tumor suppressor gene. Increasing evidence suggests that reduced expression of PinX1 plays a key role in tumorigenesis. However, the PinX1 expression status and its correlation with the clinicopathological features in prostate cancer (PCa) have not been investigated.

Methods

PinX1 mRNA and protein expression in PCa and adjacent normal prostate tissues were evaluated by real-time quantitative RT-PCR (qRT-PCR) and western blotting. The clinicopathological significance of PinX1 was investigated by immunohistochemistry (IHC) analysis on a PCa tissue microarray (TMA). The cut-off score for positive expression of PinX1 was determined by the receiver operating characteristic (ROC) analysis. The correlation between PinX1 expression and clinicopathological features of PCa was analyzed by Chi-square test.

Results

Reduced expression of PinX1 mRNA and protein was observed in the majority of PCa, compared with their paired adjacent normal prostate tissues. When PinX1 positive expression percentage was determined to be above 60% (area under ROC curve = 0.833, P = 0.000), positive expression of PinX1 was observed in 100% (8/8) of normal prostate tissues and 32.5% (13/40) of PCa tissues by IHC. Reduced expression of PinX1 in patients was correlated with advanced clinical stage (χ² = 10.230, p = 0.017), high Gleason score (χ² = 4.019, p = 0.045), positive regional lymph node metastasis (χ² = 10.852, p = 0.004) and distant metastasis (χ² = 7.965, p = 0.005).

Conclusions

Our findings suggest that reduced expression of PinX1 is correlates to progressive features in patients with PCa and may serve as a potential marker for diagnosis.

The role of PinX1 in growth control of breast cancer cells and its potential molecular mechanism by mRNA and lncRNA expression profiles screening

As a major tumor suppressor gene, the role of PinX1 in breast cancer and its molecular mechanism remain unclear. In this study, overexpression of PinX1 was generated in 3 breast cancer cell lines, and knockdown of PinX1 was performed in a nontumorigenic breast cell line. The regulation of PinX1 on cell proliferation and cell cycle was observed. A microarray-based lncRNA and mRNA expression profile screening was also performed. We found a lower growth rate, G0/G1 phase arrest, and S phase inhibition in the PinX1 overexpressed breast cancer cells, while a higher growth rate, decreased G0/G1 phase, and increased S phase rate in the PinX1 knocked-down nontumorigenic breast cell. A total of 977 mRNAs and 631 lncRNAs were identified as differentially expressed transcripts between PinX1 overexpressed and control MCF-7 cells. Further analysis identified the involvement of these mRNAs in 52 cancer related pathways and various other biological processes. 11 enhancer-like lncRNAs and 25 lincRNAs with their adjacent mRNA pairs were identified as coregulated transcripts. Our results confirmed the role of PinX1 as a major tumor suppressor gene in breast cancer cell lines and provided information for further research on the molecular mechanisms of PinX1 in tumorigenesis.

PinX1 suppresses bladder urothelial carcinoma cell proliferation via the inhibition of telomerase activity and p16/cyclin D1 pathway

BACKGROUND

PIN2/TRF1-interacting telomerase inhibitor1 (PinX1) was recently suggested as a putative tumor suppressor in several types of human cancer, based on its binding to and inhibition of telomerase. Moreover, loss of PinX1 has been detected in many human malignancies. However, the possible involvement of PinX1 and its clinical/prognostic significance in urothelial carcinoma of the bladder (UCB) are unclear.

METHODS

The PinX1 expression profile was examined by quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry (IHC) in UCB tissues and adjacent normal urothelial bladder epithelial tissues. PinX1 was overexpressed and silenced in UCB cell lines to determine its role in tumorigenesis, development of UCB, and the possible mechanism.

RESULTS

PinX1 expression in UCB was significantly down-regulated at both mRNA and protein level as compared with that in normal urothelial bladder epithelial tissues. PinX1 levels were inversely correlated with tumor multiplicity, advanced N classification, high proliferation index (Ki-67), and poor survival (P < 0.05). Moreover, overexpression of PinX1 in UCB cells significantly inhibited cell proliferation in vitro and in vivo, whereas silencing PinX1 dramatically enhanced cell proliferation. Overexpression of PinX1 resulted in G1/S phase arrest and cell growth/proliferation inhibition, while silencing PinX1 led to acceleration of G1/S transition, and cell growth/proliferation promotion by inhibiting/enhancing telomerase activity and via the p16/cyclin D1 pathway.

CONCLUSIONS

These findings suggest that down-regulation of PinX1 play an important role in the tumorigenesis and development of UCB and that the expression of PinX1 as detected by IHC is an independent molecular marker in patients with UCB.

Expression and mechanism of PinX1 and telomerase activity in the carcinogenesis of esophageal epithelial cells

Esophageal tissues were collected from an esophageal carcinoma high-risk area of China and were used to detect the telomere length and the expression of human telomerase reverse transcriptase (hTERT) by immuhistochemistry and fluorescence in situ hybridization; esophageal carcinoma tissues, paired-adjacent mucosa and paired normal mucosa were obtained from resected surgical specimens of esophageal squamous cell carcinoma in order to determine telomerase activity and expression of hTERT and Pin2/TRF1 interacting protein X1 (PinX1) by telomeric repeat amplification protocol-silver staining, RT-PCR and flow cytometry (FCM). The cell proliferation and apoptosis of Eca109 cells were analyzed by FCM and MTT assay. We found that the length of telomere DNA decreased and hTERT protein expression increased in the carcinogenesis of esophageal epithelial cells; telomerase activity was significantly upregulated followed by a decrease of PinX1 expression in esophageal carcinoma compared with dysplasia and normal patients, which notably correlated with grade and lymph node metastasis. Overexpression of PinX1 inhibited cell growth, arrested cells at the G0/G1 stage and induced cell apoptosis in Eca109 cells. In addition, PinX1 overexpression significantly inhibited telomerase activity. In conclusion, the length shortening of telomere was an important characteristic in the carcinogenesis of esophageal epithelial cells, followed by increase of telomerase activity and downregulation of PinX1. Overexpression of PinX1 blocked Eca109 cell proliferation and induced cell apoptosis by downregulating telomerase activity.

PinX1 regulation of telomerase activity and apoptosis in nasopharyngeal carcinoma cells

BACKGROUND

Human interacting protein X1 (PinX1) has been identified as a critical telomerase inhibitor and proposed to be a putative tumor suppressor gene. Loss of PinX1 has been found in a large variety of malignancies, however, its function in inhibiting telomerase activity of tumor cells is not well documented. Here we show that PinX1 is essential for down-regulation telomerase activity of nasopharyngeal carcinoma.

METHODS

Expression vectors of human PinX1 (pEGFP-C3-PinX1) and its small interfering RNA (PinX1-FAM-siRNA) were constructed and transfected into NPC. Their effects on mRNA of telomerase catalytic subunit (hTERT), telomerase activity, cell proliferation, cell migration, wound healing, cell cycles and apoptosis were examined using semi-quantitative RT-PCR, stretch PCR, MTT assay, Transwell, scratch assay and flow cytometry, respectively.

RESULTS

Transfection of pEGFP-C3-PinX1 and PinX1-FAM-siRNA increased and reduced PinX1 mRNA by 1.6-fold and 70%, respectively. Over-expression of PinX1 decreased hTERT mRNA by 21%, reduced telomerase activity, inhibited cell growth, migration and wound healing ability, arrested cells in G0/G1 phase, and increased apoptotic index. In contrast, down-regulation of PinX1 did not alter the above characteristics.

CONCLUSIONS

PinX1 may play important roles in NPC proliferation, migration and apoptosis and has application potential in tumor-targeted gene therapy.

Comparative features of colorectal and gastric cancers with microsatellite instability in Chinese patients

OBJECTIVE

The purpose of this study was to determine the unique and universal features of microsatellite instability-high (MSI-H) colorectal cancer (CRC) and MSI-H gastric cancer (GC) in the Chinese population.

METHODS

A new panel of mononucleotide MSI markers, BAT25, BAT26, NR21, NR24, and MONO-27, was used to define MSI status in 303 CRC and 288 GC subjects. Clinicopathological features of both types of MSI-H tumors were analyzed. Methylation analysis in the hMLH1 promoter region by methylation specific polymerase chain reaction (PCR) and mutation detection of hMSH2/hMLH1 genes by denaturing high-performance liquid chromatography (DHPLC) were carried out simultaneously.

RESULTS

MSI-H CRCs and MSI-H GCs account for 11.9% and 8.0% of unselected sporadic CRCs and GCs, respectively. MSI-H CRCs are strongly characterized by early onset, right-side location, low differentiation, mucinous tumor, less infiltration, less lymphatic metastasis, and more often familial tumor. MSI-H GCs only showed site preference for the antrum and less lymphatic metastasis. Genetic and epigenetic analyses were positive in 6/36 MSI-H CRCs and 0/23 MSI-H GCs with pathological mutation in major mismatch repair genes, and in 7/36 MSI-H CRCs and 18/23 MSI-H GCs with methylated hMLH1 promoter (P<0.01), respectively.

CONCLUSIONS

Although there are many differences in the genetic basis and clinicopathological features between MSI-H CRC and MSI-H GC, when compared with their microsatellite stable (MSS) counterparts, site preference and lymphatic metastasis are features common to both types of MSI-H tumors.

POT1 deficiency alters telomere length and telomere-associated gene expression in human gastric cancer cells

Telomeres are the end structures of linear chromosomes in eukaryotic cells. The integrity of a telomere is essential for the overall stability of the chromosome. The human protection of telomeres 1 (hPOT1) protein, a single-stranded telomeric DNA binding protein, plays an important role in telomere protection and telomere length regulation. Here, we show that the loss of hPOT1 by RNA interference in BGC823 (poorly differentiated human gastric adenocarcinoma) cells leads to an increase in multinucleated giant cells, a decrease in cell proliferation and colony formation, induction of senescence and apoptosis, shortened telomere length, upregulation of the TRF1 gene and downregulation of the TRF2, tankyrase1 and hTERT genes. These results suggest that the loss of hPOT1 results in a decrease in the viability of BGC823 cells; hPOT1 regulates telomere length positively and has an influence on the expression of other telomere-associated genes in the cells.

PinX1 inhibits telomerase activity in gastric cancer cells through Mad1/c-Myc pathway

INTRODUCTION

The aim of this study was to investigate the role of Mad1/c-Myc in telomerase regulation in gastric cancer cells in order to gain insight into telomerase activity and to evaluate PinX1 as a putative inhibitor of gastric cancer.

METHODS

PinX1 and PinX1siRNA eukaryotic expression vectors were constructed by recombinant technology and transfected into gastric carcinoma cells using Lipofectamine 2000. Telomerase activity was measured by the telomeric repeat amplification protocol. Apoptosis of gastric cancer cells was analyzed by flow cytometry and transmission electron microscopy. Reverse transcription-polymerase chain reaction and Western blotting were used to assess the expression levels of PinX1 and Mad1/c-Myc.

RESULTS

We found that PinX1-negative gastric cancer cells showed significantly higher telomerase activity than did the PinX1-postive cells. PinX1-transfection reduced telomerase activity in PinX1-negative gastric cancer cells and exhibited an upregulation of Mad1 and downregulation of c-Myc expression. Pinx1 RNAi treatment led to downregulation of Mad1 and upregulation of c-Myc.

CONCLUSION

Suppression of telomerase activity mediated by PinX1 is involved in the Mad1/c-Myc pathway.

Decreased expression of PinX1 protein is correlated with tumor development and is a new independent poor prognostic factor in ovarian carcinoma

Human interacting protein X1 (PinX1) has been identified as a critical telomerase inhibitor and proposed to be a putative tumor suppressor gene. Loss of PinX1 has been found in a large variety of malignancies, but the expression status in epithelial ovarian tumors has not been investigated. In this study, immunohistochemistry for PinX1 protein was performed on a tissue microarray (TMA) of epithelial ovarian tumors (informatively containing 25 cystadenomas, 29 borderline tumors, and 157 invasive carcinomas) and 12 normal ovaries. Receiver-operator curve (ROC) analysis was used to determine cut-off scores for tumor positivity and to evaluate patients' survival status. The threshold for PinX1 positivity was determined to be above 60% (area under the curve = 0.856, P < 0.001) based on the area under the ROC. Positive expression of PinX1 was observed in 100% of normal ovarian tissues, in 84% of cystadenomas, in 75.9% borderline tumors, and 66.2% of ovarian carcinomas. Decreased expression of PinX1 was strongly related to patients with poor prognostic factors regarding presence of lymph node metastasis (P = 0.024), distant metastasis (P < 0.001), and late International Federation of Gynecology and Obstetrics (FIGO) stage (P < 0.001). In univariate survival analysis, a highly significant correlation between loss of PinX1 and shortened patient survival (mean, 48.2 months vs 99.2 months, P < 0.001) was displayed. Multivariate analysis demonstrated PinX1 expression (P = 0.027) was evaluated as an independent parameter. Our findings suggest that loss of PinX1 is an adverse independent molecular marker for epithelial ovarian carcinoma patients. PinX1 may be a novel target for telomerase-based anticancer therapy due to inhibiting telomerase activity.