Correlation of P-cadherin and beta-catenin expression and phosphorylation with carcinogenesis in rat tongue cancer induced with 4-nitroquinoline 1-oxide

Impact of hyperglycemia on the expression of GLUT1 during oral carcinogenesis in rats

BACKGROUND

On the background of the epidemiological link between diabetes and oral cancer, the present study aimed to analyze the potential involvement of selected glucose transporters (GLUT1/GLUT3/GLUT4), if any, in such putative association.

METHODS AND RESULTS

Oral carcinogenesis was induced by 4-nitroquinoline N-oxide in 10 non-diabetic and 10 diabetic rats; 8 non-diabetic and 7 diabetic rats served as controls. Expressions of selected GLUTs at mRNA and protein levels were analyzed in oral tissue (normal/lesion) by quantitative real-time PCR and immunohistochemistry respectively. Premalignant lesions (hyperplasia/dysplasia/carcinoma-in-situ) appeared on tongues of carcinogen-treated animals. Significant increase of GLUT1mRNA level was seen from normal to lesion tongues, along increasing lesion grades (from hyperplasia/mild dysplasia to moderate/severe dysplasia) and in lesions induced under hyperglycemic condition than that induced under normoglycemic one; a similar trend was found in transcript variant-1 of GLUT1, but not in variant-2. GLUT3 and GLUT4 mRNA levels were comparable among lesions irrespective of grades and glycemic status. Concordant to mRNA level, overall expression of GLUT1 protein was higher in tongue lesions in presence of hyperglycemia than in absence of such condition; non-lesion portions of tongues exposed to carcinogen showed a similar trend. Moreover in carcinogen-treated groups, non-lesion and lesion portions of tongues under hyperglycemic condition showed predominantly membranous expression for GLUT1 which was again significantly higher than equivalent portions of tongue under normoglycemic condition.

CONCLUSION

Hyperglycemia seemed to favor GLUT1 over-expression and membrane localization of the protein during oral carcinogenesis. GLUT1 transcript variant-1 appeared to be more important than variant-2 in disease pathogenesis.

The efficiency of propranolol on occurrence and development of 4-nitroquinoline 1-oxide-induced squamous cell carcinoma of the tongue in rats

Aims:

The aim of this study to investigate the efficiency of propranolol on occurrence and development of 4-nitroquinoline 1-oxide (4NQO)-induced squamous cell carcinogenesis of the tongue in rats.

Subjects and Methods:

The sample was composed of 27 male Sprague Dawley rats that received 50 ppm 4NQO for 20 weeks in drinking water. Group 1 (n = 9) was treated with 50 mg/kg/day propranolol for 20 weeks, Group 2 (n = 9), after carcinogenesis inducement for 20 weeks, received propranolol (50 mg/kg/day) for 2 weeks and Group 3 (n = 9) received no treatment. At the end of the experimental stage, the tongue specimens were evaluated under a light microscope and categorized as low- or high-risk lesions according to a binary system.

Statistical Analysis Used:

The statistical comparison was performed with a likelihood ratio test.

Results:

Histopathological analysis revealed the risk of malignant transformation rates as 33.3% in Group 1, 55.5% in Group 2 and 77.8% in Group 3; however, the difference between the groups was not statistically significant (P > 0.05).

Conclusion:

The results of the study suggest that propranolol has a tendency to preventive effect against carcinogenesis.

The Significance of the Dysregulation of Canonical Wnt Signaling in Head and Neck Squamous Cell Carcinomas

The knowledge about the molecular alterations which are found in head and neck squamous cell carcinomas (HNSCC) has much increased in recent years. However, we are still awaiting the translation of this knowledge to new diagnostic and therapeutic options. Among the many molecular changes that are detected in head and neck cancer, the abnormalities in several signaling pathways, which regulate cell proliferation, cell death and stemness, seem to be especially promising with regard to the development of targeted therapies. Canonical Wnt signaling is a pathway engaged in the formation of head and neck tissues, however it is not active in adult somatic mucosal cells. The aim of this review paper is to bring together significant data related to the current knowledge on the mechanisms and functional significance of the dysregulation of the Wnt/β-catenin pathway in head and neck tumors. Research evidence related to the role of Wnt signaling activation in the stimulation of cell proliferation, migration and inhibition of apoptosis in HNSCC is presented. Moreover, its role in promoting stemness traits in head and neck cancer stem-like cells is described. Evidence corroborating the hypothesis that the Wnt signaling pathway is a very promising target of novel therapeutic interventions in HNSCC is also discussed.

The cytoplasmic domain of N-cadherin modulates MMP‑9 induction in oral squamous carcinoma cells

Oral squamous carcinoma is the sixth most common cancer worldwide, and one of the most common cancers in developing countries. Regional and distant metastases comprise the majority of cases at initial diagnosis and correlate with poor patient outcomes. Oral epithelia is one of many tissue types to exhibit a cadherin switch during tumor progression, in which endogenous cell adhesion proteins, such as E-cadherin, give way to those of mesenchymal origin. The mesenchymal cell adhesion protein N-cadherin is found at the invading front of oral squamous carcinomas and has been strongly correlated with poor patient prognosis. The goal of the present study was to elucidate the mechanism by which N-cadherin may increase extracellular matrix-associated proteolytic activity to facilitate invasiveness in oral tumor development. The overexpression of N-cadherin in two oral squamous carcinoma cell lines increased motility, invasive capacity and synthesis of matrix metalloproteinase-9 (MMP-9) in a manner that was independent of E-cadherin downregulation. The use of EN and NE chimeric cadherin molecules with reciprocally substituted cytoplasmic domains revealed that optimal induction of MMP-9 synthesis required the cytoplasmic region, but not the extracellular region, of N-cadherin. Utilizing an N-cadherin mutant with impaired p120 binding ability, we found that such mutation resulted in a 4-fold decrease in motility compared to wild-type N-cadherin, but did not affect either MMP-9 expression or motility-normalized invasion. Overexpression of wild-type N-cadherin produced a 27-fold increase in the transcriptional activity of β-catenin, concomitant with increases in MMP-9 transcription. These results suggest that N-cadherin may promote motility and invasiveness through distinct mechanisms, and that β-catenin may be an integral mediator of N-cadherin-dependent invasive signaling in oral epithelia.

Expression of E-cadherin, P-cadherin and N-cadherin in oral squamous cell carcinoma: correlation with the clinicopathologic features and patient outcome

PURPOSE

Alteration of cadherin expression is associated with the loss of cellular differentiation, the acquisition of an invasive phenotype and a poor prognosis in many types of cancer. This study aimed to evaluate the immunoreactivity of E-, P- and N-cadherins (cad) in oral squamous cell carcinoma and to correlate their expression with clinicopathological features and clinical outcome. The interaction between the cadherins was also investigated.

METHODS

A total of 71 tissue samples were examined by immunohistochemical methods on paraffin sections using specific antibodies.

RESULTS

In the primary lesions and lymph node metastases, the immunoreactivity of E-cad was reduced and P-cad was over-expressed, but the expression of N-cad was negative (p<0.001, 0.01 and 0.05, respectively). The reduced primary E-cad expression was related to the invasion pattern and lymph node metastasis (p=0.046 and 0.037, respectively). However, the expression of cadherins did not appear to differ significantly in relation to the histological grade, invasion, tumour size, stage of oral SCC or tumour recurrence. A much greater reduction in the expression of E-cad was found in the positive N-cadherin group (p=0.008). Nonetheless, cadherin expression was not significantly associated with failure-free survival or overall survival in this experiment subset.

CONCLUSION

The reduced E-cad expression and the aberrant N-cad expression are closely associated with each other in oral cancer cases, and this suggests that cadherin switching from E. cad to N. cad may play a critical role in cancer development and metastasis.

The influence of tamoxifen on growth behavior and cell-cell adhesion in OSCC in vitro

The aim of this study was to evaluate the influence of tamoxifen on the growth and aggregation behavior, focusing on the expression pattern of E-cadherin and beta-catenin, in oral squamous cell carcinoma (OSCC) in vitro. Oral squamous cancer cell lines (UM-SCC-14A, UM-SCC-14B and UM-SCC-14C) were treated with various concentrations of tamoxifen. Growth and aggregation behavior as well as the protein expression and its changes were analysed. All cell lines are estrogen receptor (ER) positive. Tamoxifen induced a significant growth inhibition and induced the ability to form cell aggregates. This phenomena was not accompanied by a change in E-cadherin or beta-catenin expression or due to transcriptional changes. beta-catenin showed isolated membrane staining and nuclear distribution in all cell lines. A defective Ecadherin/beta-catenin complex was seen in UM-SCC-14C with no restoration through tamoxifen treatment. The cell-cell formation is increased in all cell lines without any alterations in the functional and quantitative status of E-cadherin or beta-catenin, indicating that novel cell-cell adhesion complexes not involving the classical E-cadherin/beta-catenin influence cell growth and intercellular adhesion in OSCC.

4-nitroquinoline-1-oxide induced experimental oral carcinogenesis

Human oral cancer is the sixth largest group of malignancies worldwide and single largest group of malignancies in the Indian subcontinent. Seventy percent of premalignant cancers appear from premalignant lesions. Only 8-10% of these lesions finally turn into malignancy. The appearance of these premalignant lesions is one distinct feature of human oral cancer. At present there is dearth of biomarkers to identify which of these lesions will turn into malignancy. Regional lymph node metastasis and locoregional recurrence are the major factors responsible for the limited survival of patients with oral cancer. Paucity of early diagnostic and prognostic markers is one of the contributory factors for higher mortality rates. Cancer is a multistep process and because of constrain in availability of human tissues from multiple stages of oral carcinogenesis including normal tissues, animal models are being widely used, aiming for the development of diagnostic and prognostic markers. A number of chemical carcinogens like coal tar, 20 methyl cholanthrene (20MC), 9,10-dimethyl-1,2-benzanthracene (DMBA) and 4-nitroquinoline-1-oxide (4NQO) have been used in experimental oral carcinogenesis. However, 4NQO is the preferred carcinogen apart from DMBA in the development of experimental oral carcinogenesis. 4NQO is a water soluble carcinogen, which induces tumors predominantly in the oral cavity. It produces all the stages of oral carcinogenesis and several lines of evidences suggest that similar histological as well as molecular changes are observed in the human system. In the present review an attempt has been made to collate the information available on mechanisms of action of 4NQO, studies carried out for the development of biomarkers and chemopreventives agents using 4NQO animal models.

Ultrastructural changes of the palatal mucosa following application of 4-nitroquinoline-l-oxide (4NQO) in rats subjected to major salivary gland excision

OBJECTIVE

It has been suggested that saliva exerts a protective role against the carcinogenic effect of various substances in the oral cavity. The objective of this study was to examine the ultrastructural changes of the palatal mucosa caused by the application of 4-nitroquinoline-l-oxide (4NQO) in the presence or absence of saliva.

STUDY DESIGN

Wistar-Furth rats subjected and not subjected to total bilateral excision of the major salivary glands were either painted with an aqueous solution of 4NQO or with propylene glycol only (controls). Two animals of each group were humanely killed periodically. The areas of the palatal lesions were immediately sliced and processed for TEM examination.

RESULTS

Ultrastructurally, the progressive changes to squamous cell carcinoma were observed in the animals painted with 4NQO. In the desalivated animals group, the ultrastructural alterations appeared earlier than in the group with salivary glands.

CONCLUSIONS

Saliva appeared to delay but not hinder tumor induction by 4NQO.

P-cadherin expression reduced in squamous cell carcinoma of the oral cavity

BACKGROUND

The loss of cadherin expression has been shown to correlate to the invasion and metastasis of many types of carcinomas. The purpose of the current study was to evaluate whether the impaired expression of E-cadherin (E-cad) and P-cadherin (P-cad) correlated with the clinical evolution and prognosis of oral squamous cell carcinoma (OSCC).

METHODS

The authors used immunohistochemical methods to analyze the expression pattern of E-cad and P-cad in healthy oral mucosa, in oral carcinoma in situ (CIS), and in surgical samples of 50 patients with the early stages (Stages I-II) of OSCC.

RESULTS

E-cad showed weak expression in the basal layer of the healthy oral mucosa and reduced expression in patients with oral CIS. P-cad expression was conserved on the basal and suprabasal layers of the healthy mucosa and, also, in the CIS. In the group of patients with OSCC, univariate analysis demonstrated that reduced expression of E-cad or P-cad correlated significantly with locoregional disease recurrence in the follow-up (P=0.03 and P=0.01, respectively). However, only the reduction in the expression of P-cad emerged as an independent prognostic marker in the multivariate analysis (P=0.04, hazard ratio =8.06).

CONCLUSIONS

These findings suggested that a decrease in E-cad and/or P-cad expression may contribute to the invasive potential of early OSCC. According to the current data, P-cad expression may be a potential independent prognostic factor in patients with OSCC.

A Serial Analysis of Gene Expression (SAGE) database analysis of chemosensitivity: comparing solid tumors with cell lines and comparing solid tumors from different tissue origins

Drug sensitivity and resistance has been most extensively studied in cell lines carried in tissue culture. Furthermore, cell lines have been widely used in testing new anticancer agents, despite the widely recognized observation that cell lines are more sensitive to cytotoxic drugs than are their corresponding solid tumors. We used the Serial Analysis of Gene Expression (SAGE) database to identify differences between solid tumors and cell lines, hoping to detect genes that could potentially explain differences in drug sensitivity. SAGE libraries were available for both solid tumors and cell lines from breast, colon, ovarian, pancreatic, and prostate carcinomas and from gliomas and medulloblastomas. Sixty-two genes were identified as overexpressed in tumors. The immune response and complement pathways were the significant common themes, with extracellular matrix (ECM) proteins third. For the 61 genes overexpressed in cell lines, protein synthesis was the dominant theme. We next used the SAGE database to identify genetic differences between tumor types that convey a broad range of survival to the patients that bear them as distant metastases. SAGE gene expression data were correlated with 5-year survivals documented in the SEER (Surveillance, Epidemiology and End-Results) database for patients diagnosed with "distant" or metastatic cancers. These are unlikely to be amenable to surgical resection; therefore, survival here reflects, to some extent, sensitivity to systemic therapy, i.e., chemotherapy. Using survival data as a surrogate of chemotherapy sensitivity, a spectrum can be generated, with testicular cancer at one end and pancreatic cancer at the other. Favorable 5-year survival, despite a distant presentation, correlates with expression of protein synthesis genes. Poor 5-year survival correlates with expression of cell adhesion, cytoskeletal, and ECM genes, a pattern similar to that found to distinguish solid tumors from the more cytotoxin-sensitive cancer cell lines. One interpretation is that resistance to chemotherapy may arise, in part, from the adherent, relatively inert condition (i.e., low in protein synthesis potential) of refractory cancers. Thus, attachment or ECM genes could be targets for anticancer therapy.