|Year : 2018 | Volume
| Issue : 1 | Page : 124-127
Occludin protein expression in human cervical cancer and its association with patient's clinical characteristics
Bin Zhang, Xiuhui Chen, Yao Lin, Shaoyu Wang, Qiufang Bao
Department of Gynaecology and Obstetrics, The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian Province, PR China
|Date of Web Publication||8-Mar-2018|
Dr. Bin Zhang
Department of Gynaecology and Obstetrics, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian Province
Source of Support: None, Conflict of Interest: None
Objective: The objective of the study was to investigate the expression of the tight junction protein occludin (encoded by OCLN gene) in human cervical cancer and its association with clinical features of patients.
Materials and Methods: Sixty-one patients with cervical cancer were included in this study from June 30, 2015 to April 30, 2017. Immuno-histochemical assay was applied to examine the expression of occludin protein in 61 cervical cancer tissues and matched adjacent cancer normal tissues. The association of occludin protein expression with clinical pathology characteristics was analyzed.
Results: Occludin protein was mainly expressed in cell membranes and cytoplasm of both the cervical cancer cell and the normal cells. The protein was manifested with brownish-yellow granules. In cervical cancer tissues, the positive rate of occludin protein was 77.05% (47/61), whereas, in adjacent normal tissues of the cancer, the positive rate was 96.72% (59/61). Therefore, the positive rate of occludin in cervical cancer tissues was significantly lower than that of the adjacent cancer tissues (P < 0.05). Occludin protein expression level was not significantly correlated with the age (P > 0.05), tumor size (P > 0.05), International Federation of Gynecology and Obstetrics staging (P > 0.05), pathological grades (P > 0.05), and lymph node metastasis (P > 0.05) of the patients.
Conclusion: Occludin protein may contribute to the development of cervical cancer. However, it was not correlated with the clinical features.
Keywords: Cervical cancer, clinical characteristics, clinical significance, immunohistochemical assay, occludin
|How to cite this article:|
Zhang B, Chen X, Lin Y, Wang S, Bao Q. Occludin protein expression in human cervical cancer and its association with patient's clinical characteristics. J Can Res Ther 2018;14:124-7
|How to cite this URL:|
Zhang B, Chen X, Lin Y, Wang S, Bao Q. Occludin protein expression in human cervical cancer and its association with patient's clinical characteristics. J Can Res Ther [serial online] 2018 [cited 2021 Jun 24];14:124-7. Available from: https://www.cancerjournal.net/text.asp?2018/14/1/124/226749
| > Introduction|| |
Intercellular connection was an important structure for the maintenance of cellular physiological functions. The tight junction (TJ) played a crucial role in signaling pathways that controlled cell growth and differentiation. TJs also played a key role in the occurrence and development of tumor because of its roles in intracellular and extracellular signaling pathways.,,, TJs involved three major transmembrane proteins, namely, claudins, occludin, and connection adhesion factor. Occludin was an important transmembrane protein of TJs. Occludin has also been the first discovered  integral membrane protein that was separated from TJs. Studies demonstrated that occludin expression could be significantly decreased in many tumors, suggesting the probably changed quantity and/or quality. In the study of endometrial cancer, the expression of occludin was decreased with increased tumor level. Its low expression was related to the invasion of the myometrium and lymph node metastasis. However, whether occludin presented the same expression changes with clinical significance in cervical cancer patients has been still unclear. Therefore, 61 cases of cervical cancer patients who were diagnosed and treated in our hospital were selected as study objects. The occludin protein expression levels in both the cancerous and normal tissues of the patients were determined with immunohistochemical detection. Its relationship with the clinicopathological features of the patients was also discussed.
| > Materials and Methods|| |
A total of 61 cases of cervical cancer treated in the first affiliated hospital of Fujian Medical University from June 30, 2015 to April 30, 2017 were enrolled as study objects. The inclusion criteria were as follows: (1) diagnosed as cervical cancer with histopathology; (2) neither neoadjuvant chemotherapy nor biologic therapy was received before the surgery; and (3) consent form was signed by the patients and their families. The exclusion criteria were as follows: (1) unclear diagnosis of cervical cancer; (2) patients who had received the chemotherapy before surgery; (3) occurrence of distant metastases; and (4) patients with a history of other malignancies.
The primary tumor tissue and the adjacent normal tissue (distance from cancer tissue was >5 cm) were obtained by surgical resection. After the resection, the specimen was washed in phosphate-buffered solution (PBS), immediately frozen in liquid nitrogen, and transferred to a refrigerator for long-term preservation at −80°C to extract pretissue protein. This study had been approved by the Ethics Committee of the First Affiliated Hospital of Fujian Medical University. All patients or their family members filled out informed consent forms and agreed that their tissues would be applied for a clinical trial.
Table-type microcentrifuge (Mierofuge 18) was obtained from Bechman Coulter Company, Vortex oscillator (Vortex-GenieZ) was obtained from Scientific Industries (USA). Pure water system was from Millipore Company Germany. Mouse anti-occludin monoclonal antibody was obtained from Santa Cruz Biotechnology, Ltd., USA. Color kit was from Fuzhou Maixin Biotechnology, Ltd.
Two-step streptavidin-perosidase (SP) was applied for the test. Primary antibody was diluted at 1:200 and applied according to the kit instructions. PBS was involved to be the alternative of primary antibody as negative control. Cervical cancer tissue slices, which had been verified as positive by repeated pretests, were involved as the positive control. Positive occludin expression was observed in the immunohistochemical reaction, displaying as brownish cell membrane and cytoplasm. Brownish cell membrane/cytoplasm appeared brownish indicated positive expression. Colorless cytoplasm, cell membrane, and cell indicated negative expression. Colored cell counting method was adopted for scoring in this experiment. Well-colored area was selected, positive cell numbers under high-power field were counted, and mean value was calculated. The colored cell numbers that were <5% were determined as negative, and the cell numbers that were ≥5% were determined as positive.
STATA11.0 statistical software (http://www.stata.com) was applied for statistical analysis. The enumeration data were expressed with n (%), and the comparison was made through Chi-squared test. P <0.05 indicated statistical difference.
| > Results|| |
General information of the patients
The median age of the 61 patients with cervical cancer was 55.65 years old (ranged 28–74). There were twenty cases at Stage I and 41 cases at Stage II according to the International Federation of Gynecology and Obstetrics (FIGO) staging system. A total of 18 cases of local lymph node metastases and 43 cases of nonmetastases were also observed. A total of 58 cases of squamous carcinoma and three cases of adenocarcinoma were observed for pathological types. The basic clinical characteristics of the 61 cases of cervical cancer were summarized [Table 1].
|Table 1: The general information of the included 61 patients with cervical cancer|
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Occludin expression in cervical cancer and adjacent tissues
Occludin protein was mainly expressed in cell membranes and cytoplasm of the cervical cancer cell and of the normal cells beside the cancer cells. The protein manifested with brownish-yellow granules. The protein was evenly distributed on the membrane and cytoplasm [Figure 1].
|Figure 1: Occludin expression in cervical cancer (a) occludin negative expression ×100; (b) occludin negative expression ×200; (c) occludin negative expression ×4; (d) occludin positive expression ×100; (e) occludin positive expression ×200; (f) occludin positive expression ×400|
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Comparison of positive occludin rate in tissues of cervical cancer and cancer-adjacent tissues
In cervical cancer tissues, the positive rate of occludin protein was 77.05% (47/61), whereas in adjacent normal tissues of cancer, the positive rate was 96.72% (59/61). Therefore, the positive rate of occludin in cervical cancer tissues was significantly lower than that of the adjacent cancer tissues (P< 0.05) [Table 2].
|Table 2: The positive occludin rate in tissues of cervical cancer and cancer-adjacent tissues|
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Occludin expression and the clinicopathological features
Occludin protein expression level was not significantly correlated with the age (P > 0.05), tumor size (P > 0.05), FIGO staging (P > 0.05), pathological grades (P > 0.05), and lymph node metastasis (P > 0.05) of the patient [Table 3].
|Table 3: Correlation between protein expression and the clinicopathological features|
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| > Discussion|| |
Cervical cancer was one of the most common malignant tumors in the female reproductive system., Currently, human papillomavirus (HPV) has been one of the important factors that resulted in cervical cancer. Moreover, HPV DNA could be detected in cervical tissues of approximately 90% of cervical cancer patients., However, HPV infection was not sufficient to cause a malignant transformation in the cervical tissue. Therefore, other important factors would work with HPV to promote the malignant transformation of cervical tissue. Current studies showed that the molecular mechanism of cervical cancer lesion and malignant transformation was very complicated. Intercellular connective molecules played important roles in tumor development, especially in metastasis. Our study discovered that the closely linked occludin protein was significantly lower in the tissue specimen of cervical cancer patients, suggesting that occludin protein was probably involved in the occurrence and development of cervical cancer.
The intracellular connection mainly involved TJs, adherens junctions (AJs), and gap junctions, of which occluding tight junctions (OTJs) and AJs were closely related with cell reproduction and tumor formation. The destruction of TJ structure resulted in the reduction of cell cohesion and invasion, leading to the transfer of the tumor. TJ was a complex structure that was connected to intracellular skeleton proteins (e.g., actin) by transmembrane protein (e.g., occludin-chaudians) and membrane protein (e.g., ZO-1, ZO-2, ZO-3, and JAM). Occludin has been the most sensitive and reliable protein in TJ structures. Occludin genes were evolutionarily conservative. These genes were 90% homologous in mice, humans, and dogs, and their biological functions were closely related with intercellular axial attachment movement and intercellular permeability adjustment.
Occludin protein expression in tumor either for endometrial cancer or oral squamous cell carcinoma has been studied., Expression was decreased in the corresponding tumor tissues. In terms of clinical significance, occludin expression was decreased with increased endometrial cancer because of the invasion of mesometrium and lymph node metastasis. However, occludin was not associated with the pathological parameters in oral squamous cell carcinoma. Our findings in cervical cancer suggested that positive expression rate of occludin protein was significantly lower in cervical cancer than that of in adjacent tissues. However, its expression rate was not relevant with various clinical characteristics of a patient including age, tumor size, FIGO staging, pathological grades, and lymph node metastasis. The results were different with the research results from Tobioka et al. and others, which may be resulted from the small sample size of this test and low statistical efficiency. Therefore, if the sample size could be increased in the next step, then there may be a relationship between occludin protein and the clinicopathological features for the cervical cancer patients.
The immunohistological study demonstrated that occludin protein expression differed in the tissues of cervical cancer and paracarcinoma tissues. Therefore, it suggested that occludin protein might be related with the occurrence and development of cervical cancer. However, the function and action molecular mechanism of occludin protein in cervical cancer have been still unclear. Therefore, potential molecular mechanism should still be further explored with molecular clone and small interference RNA. In addition, the cause for the decrease in occludin protein expression rate in the cervical cancer has been still unclear. Therefore, in the next step, the possible upstream regulatory mechanism should be explored from the aspects of transcription inhibition, epigenetic modification, and noncoding RNA regulation.
Financial support and sponsorship
This work was supported by Natural Science Research Fund of Fujian province (No. 2017J01282).
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]