CD26 (Dipeptidyl Aminopeptidase IV) Expression in Normal and Diseased Human Thyroid Glands

Impaired Glucose Metabolism, Anti-Diabetes Medications, and Risk of Thyroid Cancer

Simple Summary

An epidemiologic link exists between obesity, insulin resistance, diabetes, and some cancers, such as breast cancer and colon cancer. The prevalence of obesity and diabetes is increasing, and additional epidemiologic data suggest that there may be a link between obesity and risk of thyroid abnormalities. Factors that may link obesity and diabetes with thyroid proliferative disorders include elevated circulating levels of insulin, increased body fat, high blood sugars, and exogenous insulin use. However, mechanisms underlying associations of obesity, diabetes, and thyroid proliferative disorders are not yet fully understood. The present manuscript reviews and summarizes current evidence of mechanisms and epidemiologic associations of obesity, insulin resistance, and use of anti-diabetes medications with benign and malignant proliferative disorders of the thyroid.

Abstract

The prevalence of obesity is progressively increasing along with the potential high risk for insulin resistance and development of type 2 diabetes mellitus. Obesity is associated with increased risk of many malignancies, and hyperinsulinemia has been proposed to be a link between obesity and cancer development. The incidence of thyroid cancer is also increasing, making this cancer the most common endocrine malignancy. There is some evidence of associations between obesity, insulin resistance and/or diabetes with thyroid proliferative disorders, including thyroid cancer. However, the etiology of such an association has not been fully elucidated. The goal of the present work is to review the current knowledge on crosstalk between thyroid and glucose metabolic pathways and the effects of obesity, insulin resistance, diabetes, and anti-hyperglycemic medications on the risk of thyroid cancer development.

Expression of GLP-1 receptor and CD26 in human thyroid C-cells: The association of thyroid C-cell tumorigenesis with incretin-based medicine

Recent reports have demonstrated that long-term and high dosage treatments with incretin-based medicine, such as hormone glucagon-like peptide-1 (GLP-1) may induce thyroid C-cell pathological changes in rodents, rather than in humans. Doubts regarding the tumorigenic potential of GLP-1 analogues in human thyroid C-cells remain. The present study aimed to determine the expression levels of GLP-1 receptor (GLP-1R) and cluster of differentiation 26 (CD26) in the C-cells of thyroid tissues from non-neoplastic, medullary carcinoma and hyperplasia subjects, and to explore the potential clinical significance. The following cases were analyzed: Medullary thyroid carcinoma (n=62, including 59 paraffin-embedded samples and 3 fresh frozen samples), C-cell hyperplasia (n=20, paraffin-embedded samples) and non-neoplastic thyroid tissue samples (n=7, paraffin-embedded samples). GLP-1R and CD26 expression was detected using immunohistochemical staining and western blotting. There were significant differences in the expression levels of the two markers between medullary thyroid carcinoma and C-cell hyperplasia, in addition to between medullary thyroid carcinoma and non-neoplastic thyroid tissue following immunohistochemical staining. Similar significant differences in the expression of GLP-1R and CD26 were detected using western blot analysis in the medullary thyroid carcinoma compared with non-neoplastic thyroid tissue sectioned from the aforementioned fresh frozen samples. There was a significant negative correlation between GLP-1R and CD26 expression. In addition, the present data indicated that GLP-1R expression was associated with the age of the patients with medullary thyroid carcinoma. These results suggested that GLP-1R and CD26 may be closely associated with the development of thyroid C-cell hyperplasia and medullary thyroid carcinoma, and indicated the importance of being aware of the side effects of incretin medicine.

Interspecies differences in membrane-associated protease activities of thyrocytes and their relevance for thyroid cancer studies

Background

To understand the role of proteases involved in human thyroid cancer progression and tissue invasion, thyrocytes from other species could potentially be used provided their characteristics are similar. It is not known whether dipeptidyl peptidase IV and aminopeptidase N activities, which are overexpressed in human thyroid cancer, are, as in human, also absent in normal thyrocytes of other species, making them suitable models for studies on the regulation of these proteases.

Methods

To assess the role of these proteases, activity was measured in thyroid tissue of human, mouse, rat, porcine, bovine and ovine origin. The lysosomal protease, dipeptidyl peptidase II, was used for comparison.

Results

Murine, rat, ovine, bovine and human thyrocytes all lacked dipeptidyl peptidase IV and aminopeptidase N activity, but porcine thyrocytes were found to possess both. In contrast, lysosomal dipeptidyl peptidase II was strongly expressed in all species. These activity patterns were maintained in cultured cells. Cultured porcine thyrocytes formed follicles with typical morphology upon stimulation with TSH but differed from human thyrocytes in their response to thiamazole.

Conclusions

These species differences in the expression of dipeptidyl peptidase IV and aminopeptidase N, indicate that porcine thyrocytes cannot be considered appropriate for the study of proteases in human cancer development.

Stromal expression of CD34, α-smooth muscle actin and CD26/DPPIV in squamous cell carcinoma of the skin: a comparative immunohistochemical study

Invasion pathogenesis is one of the most complicated issues in the literature. There are numerous studies concerning the tumor markers implicated in the preinvasive-invasive tumor sequence. Despite ample studies on the invasion pathogenesis of cutaneous melanomas, there is limited and dispersed work presently available on non-melanoma skin cancer. The vast knowledge in the literature concerning this issue in squamous cell carcinoma comes mostly from the studies of the oral cavity, esophagus, larynx, and cervix. In this study, we investigated tumor-free neighboring stroma and tumor stroma in squamous cell carcinomas (SCCs) of the skin as well as keratoacanthomas (KAs) with respect to the presence of stromal CD34-positive (CD34+) fibrocytes and α-smooth muscle actin-positive (α-SMA+) myofibroblasts using seborrheic keratosis (SKs) and non-tumoral skin samples as controls. We also evaluated the stromal expression pattern of CD26/DPPIV (CD26), a tumor suppressor gene product that also has immunoregulatory properties. Immunohistochemistry was performed on samples of 31 SCC, 8 KA, 15 SK and 10 non-tumoral skin samples. Peri-tumoral stroma from resection margins was also evaluated. We found that CD34 and α-SMA demonstrated significantly different staining between benign and malignant squamous skin lesions consisting of a loss of CD34+ fibrocytes paralleled by a gain of α-SMA+ myofibroblasts in malignant tumor stroma. Additionally, it was shown that CD26 expression was lower in tumor stroma when compared to that of tumor neighboring stroma. However, we concluded that this finding may be attributable to the solar elastosis areas in the peritumoral tissue, which shows diffuse strong positivity for this marker.

Dipeptidyl peptidase IV expression in thyroid cytology: retrospective histologically confirmed study

Fine needle aspiration cytology (FNAC) of the thyroid gland is a well-established method. However, it has inherent limitations, especially in the diagnosis of follicular and oncocytic tumours and in distinguishing between nuclear atypia in colloid goitre with regressive changes and cystic papillary carcinoma. The aim of our study was to evaluate dipeptidyl peptidase IV (DPP IV) as a marker of malignancy in FNAC. We tested 254 thyroid specimens (intraoperative imprint smears) for DPP IV. The sensitivity was 71%, the specificity was 96%, and the diagnostic accuracy was 93%, respectively, with a threshold of 50% of positive cells. To the best of our knowledge it is the largest histologically confirmed study reported in the literature. We suggest the assessment of DPP IV as an adjunct diagnostic marker of malignancy in thyroid specimens suspicious of papillary carcinoma. However, the value of the marker in follicular lesions is very limited.

Diagnosis of malignant epithelial thyroid lesions: fine needle aspiration and histopathologic correlation

Fine needle aspiration is a diagnostic tool useful as a guide to patient management. We believe that its role in solving the diagnostic dilemmas presented by thyroid nodules is still underappreciated. Current fiscal constraints in health care might bring about a wider use of this simple technique to select patients for surgery. Care in sampling a mass is essential to obtain aspirates that are representative of the lesion and adequate in quantity for interpretation. Several aspirates are needed from all but the smallest masses. Most thyroid carcinomas are well-differentiated with a low grade of malignancy. The majority of these are papillary carcinomas, which are easily diagnosed in good cytologic smears. With fine needle aspirates the goal is to diagnose a follicular neoplasm and to separate it from the adenomatoid nodule. The follicular neoplasm then can be classified as adenoma or carcinoma with the histologic sections. The minimally invasive carcinoma still can be challenging to recognize. We hope that the cytologic criteria and histopathologic correlations presented here will help general pathologists who interpret aspirates. We believe that in the near future additional immunohistochemical methods and genetic markers will be used increasingly to discriminate among the neoplasms and to provide prognostic information.