| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ORIGINAL ARTICLE |
Department of Cardiothoracic Surgery, Xiangya Hospital, Central South University
1 Department of Molecular Genetics, Reproductive & Genetics Hospital of CITIC-Xiangya Changsha, China
Wei Xing Zhang, MD, Tel: +86 0731 4327022, Fax: +86 0731 4327332, Email: drzwx{at}yahoo.cn, Department of Cardiothoracic Surgery, Xiangya Hospital, Central South University, Changsha 410008, China.
ABSTRACT
Phosphorylation of proteins on serine or threonine residues preceding proline is a major regulatory mechanism in cell proliferation and transformation, which is catalyzed specifically by Pin1, a peptidylprolyl isomerase. Pin1 is overexpressed in several human cancers. The expression of Pin1 mRNA in the circulation was assessed in 26 patients with non-small-cell lung cancer who underwent surgical resection. They were randomly assigned to a pulmonary artery first ligation group and a pulmonary vein first ligation group. Pin1 mRNA expression in blood samples from patients with lung cancer, controls with benign lung disease, and healthy subjects were determined by a real-time reverse transcriptase polymerase chain reaction. Compared to those with benign lung disease and healthy controls, Pin1 mRNA was overexpressed in patients with non-small-cell lung cancer, and the levels correlated with lymph node-positive disease and tumor stage. Expression of Pin1 mRNA in the distal part of the pulmonary vein was significantly higher than in the proximal part. Postoperative Pin1 mRNA expression was significant lower than preoperative expression. There was no significant difference in Pin1 expression between groups based on pulmonary vessel ligation. These findings suggest that Pin1 might be a useful tumor marker for cancer therapy.
Key Words: Carcinoma • Non-Small-Cell Lung • NIMA-interacting peptidylprolyl isomerase [Substance Name] • Reverse Transcriptase Polymerase Chain Reaction
INTRODUCTION
Lung cancer is one of the most common cancers and the leading cause of cancer-related death worldwide; with 1.2 million new diagnoses annually, it is responsible for 17.8% of all cancer-related deaths.1 There is a need for biomarkers of lung cancer, especially non-small-cell lung cancer (NSCLC), to enable early diagnosis and therapy. Pin1, an NIMA-interacting peptidylprolyl isomerase, is composed of 163 amino acids. It was first discovered in a screen for molecules regulating mitosis.2 It contains 2 domains: the N-terminal WW (1–39 amino acids), and the C-terminal peptidylprolyl isomerase domain (45–163 amino acids). The WW domain binds to serine or threonine when it is followed by proline, and the enzyme domain isomerizes the bond.3,4 Pin1 plays an important role in regulating cell proliferation because of these special structures. The phosphorylation of proteins on serine or threonine residues that immediately precede proline (pSer/Thr-Pro), so-called Pro-directed phosphorylation, is a central signaling mechanism controlling normal cell proliferation and malignant transformation.5 Ser/Thr-Pro motifs are the exclusive phosphorylation sites for a large number of Pro-directed protein kinases that play essential roles in signal transduction and cell cycle progression. Furthermore, many oncogenes and tumor suppressors are directly regulated by Pro-directed phosphorylation or trigger signaling pathways involving Pro-directed phosphorylation. By isomerizing specific Ser/Thr-Pro bonds, Pin1 has been shown to induce conformational changes in proteins after phosphorylation, thereby profoundly effecting their catalytic activity, dephosphorylation, protein-protein interactions, subcellular location, or turnover.2,6,7 Thus phosphorylation-dependent prolyl isomerization is a critical post-phosphorylation regulatory mechanism in phosphorylation signaling.8 This study was undertaken to assess the expression of Pin1 mRNA in the circulation of patients with NSCLC.
PATIENTS AND METHODS
This work was ratified by the Ethics Committee of Xiangya Hospital. All samples were obtained between September 2007 and January 2008. With informed consent, 104 blood samples were collected from 26 consecutive patients with lung cancer who underwent surgical resection with curative intent. Samples were obtained at 4 time points: preoperatively after tracheal intubation, intraoperatively before and after pulmonary vein ligation, and on the 7th day postoperatively (Figure 1
). Before the operation, the patients were randomly assigned to 1 of 2 surgical procedure groups based on the order of vessel ligation: pulmonary vein 1st group, and pulmonary artery 1st group. All blood samples were collected in vacuum tubes containing sodium heparin.
|
.
|
All statistical analyses were performed using SPSS version 13.0 for Windows software (SPSS, Inc., Chicago, IL, USA). The means average relative content was calculated as described by Livak and Schmittgen.9 Differences between the relative content of each group were examined by the Wilcoxon rank sum test. Differences were considered significant if the p value was <0.05.
RESULTS
Pin1 mRNA was overexpressed in the circulation of patients with NSCLC. Blood from NSCLC patients had a 1.69–34.78 Pin1 mRNA expression ratio compared to normal healthy samples. There were no significant differences in Pin1 expression between normal controls and patients with lung benign disease (Table 2). The expression of Pin1m RNA at different blood collection time points in patients with NSCLC was analyzed. Table 3 shows that the expression of Pin1 mRNA in the distal part of pulmonary vein after ligation was significantly higher than in the proximal part (mean rank, 31.42 vs. 21.58; p = 0.019); and the expression of Pin1 mRNA was significantly higher preoperatively than postoperatively (mean rank, 31.04 vs. 21.96; p = 0.031). As shown in Table 4, there was no significant correlation between Pin1 mRNA expression and the histologic or differentiation types of the tumors, but there was a high level of Pin1 mRNA expression in the presence of lymph node metastasis (p = 0.043), and it correlated with the stage of disease (p = 0.038).
|
|
|
Because traditional PCR technology is at best semi-quantitative, it has been difficult to differentiate between the baseline level of gene expression in normal tissues and increased levels associated with cancer, raising concerns of false-positive results. In this study, real-time PCR was exploited to investigate the possibility of using easily accessible body fluids for detection of circulating tumor cells, enabling longitudinal observation of the disease, therapy monitoring, and initial diagnosis. Detection and quantitation of circulating tumor cells from solid epithelial tumors could become a valuable tool for monitoring therapy.
We have shown that Pin1 is overexpressed in NSCLC, with a 1.69–34.78 Pin1 mRNA expression ratio in the circulation of patients with NSCLC compared to healthy controls. These tumors have been reported to have a 1.8 or greater expression ratio compared to normal tissue, which would be categorized as over-expressed.10 Because Pin1 is regulated by so many cell-signaling molecules and is involved in oncogenic pathways, it comes as no surprise that Pin1 has been implicated in cancer. Pin1 is overexpressed in many tumor types, including breast, prostrate, lung, ovarian, and cervical carcinomas.11–13 Bao and colleagues13 studied 2,041 tumor samples and 609 normal tissues; they found 38 of 60 types of tumor overexpressed Pin1 by more than 10% compared to normal samples, whereas in most normal tissue samples, Pin1 was expressed at very low levels.
Our data show that Pin1 mRNA expression was higher in the distal part of the ligated pulmonary vein than in the proximal part, it was also higher preoperatively than postoperatively, and higher in the proximal part of the pulmonary vein in the pulmonary artery 1st group than in the pulmonary vein 1st group, but this was not statistically significant. Previously, some studies demonstrated that a temporary intraoperative dissemination of tumor cells into the circulation could occur.14 One study found that surgical manipulation promoted the release of tumor cells into the blood stream, and ligation of the pulmonary vein before ligation of the pulmonary artery may partly prevent such release during surgery.15
Our results demonstrate a relationship between lymph node metastasis, tumor stage, and Pin1 mRNA. He and colleagues10 suggested that higher Pin1 mRNA expression might indicate a worse prognosis for patients with NSCLC. Because Pin1 is overexpressed in tumors, and a high level of expression suggests a worse prognosis, Pin1 is potentially an excellent tumor marker. Many research institutes have undertaken studies on the mechanism of tumors.2,13,16–18 It is considered that Pin1 may play a critical role in the pathogenesis, diagnosis, and treatment of many human cancers, including lung cancer. Furthermore, Pin1-knockout mice do reach adulthood despite some cell proliferative abnormalities.19 Some pharmaceutical companies are currently researching inhibitors of Pin1, hoping to produce a specific anti-Pin1 drug to induce tumor cell apoptosis. Thus detecting Pin1 mRNA expression in the circulation will also be crucial in examining the effects of such drugs.
ACKNOWLEDGMENTS
This work was supported by grant from the Scientific Fund of the Hunan Scientific and Technology Bureau (04JT1005).
REFERENCES
Asian Cardiovasc Thorac Ann 2009;
17:157-161
© 2009 by SAGE Publications
DOI: 10.1177/0218492309103297
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
