Possible Relation of p53 and mdm-2 Oncoprotein Expression in Thyroid Carcinoma: A Molecular-Pathological and Immunohistochemical Study on Paraffin-Embedded Tissue

Rationale for Testing TP53 Mutations in Thyroid Cancer-Original Data and Meta-Analysis

The p53 protein is a tumor-suppressing transcription factor that is critical in tumorigenesis. While TP53 mutations are rare in differentiated thyroid cancer (DTC), they are significantly more common in anaplastic thyroid cancer (ATC). This study presents original results and a meta-analysis reevaluating the prognostic value of TP53 mutations in thyroid cancer, including surrogate markers such as immunohistochemical p53 expression and serum p53-Abs levels. TP53 mutations were analyzed using SSSP and direct sequencing in a DTC group (15 patients), an ATC group (3 patients), and a control group (25 patients). The immunohistochemical p53 expression was assessed in tissue samples. A meta-analysis of 14 eligible studies identified through the PubMed, Scopus, Google Scholar, and Cochrane databases was conducted. Our results showed TP53 mutations in all ATC cases, 6.67% of DTC cases (1 out of 15), and none in the control group. Immunohistochemical p53 overexpression was observed in 4 out of 15 DTC (26.67%) and all ATC cases but absent in controls. A meta-analysis confirmed that TP53 mutations are significantly more frequent in ATC than controls (OR 8.95; 95% CI: 1.36-58.70; p = 0.02) but not in DTC vs. controls (OR 1.87; 95% CI: 0.53-6.58; p = 0.33). p53 overexpression was significantly higher in both DTC and ATC vs. controls (OR 7.99; 95% CI: 5.11-12.51; p < 0.01 and OR 64.37; 95% CI: 27.28-151.89; p < 0.01, respectively). The serum p53-Abs positivity was also elevated in patients with PTC vs. controls (OR 2.07; 95% CI: 1.24-3.47; p < 0.01). TP53 mutations are frequent events in the pathogenesis of ATC. In DTC, further prospective studies are needed to determine the prognostic value of TP53 mutations and related surrogate markers (immunohistochemical p53 expression, p53-Abs positivity).

Patterns of expression of cell cycle/apoptosis genes along the spectrum of thyroid carcinoma progression

BACKGROUND

Genetic screening studies suggest that genetic changes underlie progression from well differentiated to anaplastic thyroid cancers. The aim of this study is to determine to what extent cell cycle/apoptosis regulators contribute to cancer progression.

METHODS

Tissue microarrarys (TMAs) were constructed from well-differentiated papillary thyroid carcinoma (WDPTC; n = 41), poorly differentiated thyroid carcinoma (PDTC; n = 43), and anaplastic thyroid carcinoma (ATC; n = 22). TMAs were immunostained for 7 different cell cycle/apoptosis-related genes (p53, Ki-67, bcl-2, mdm-2, cyclin D1, p21, and p27).

RESULTS

p53 (0%, 12%, 32%) and Ki-67 (5%, 49%, 82%) were expressed with increasing frequency, and bcl-2 (68%, 42%, 0%) and p21 (40%, 7%, 0%) with decreasing frequency in WDPTC to PDTC and ATC, respectively (P < .001). Interestingly, mdm-2 (54%, 5%, 0%) showed decreased expression along the progression axis (P < .001). p27 and cyclin D1 were expressed in <15% of cases, with a trend toward decreasing expression from WDPTC to PDTC to ATC.

CONCLUSIONS

These data confirm the presence of increasing genetic complexity with progressive dedifferentiation in thyroid cancer, with aberrant tumor suppressor activity and increased proliferative activity being most prevalent in ATC. The data also confirm the intermediate position of PDTC in the classification scheme of thyroid carcinomas.

Does the fine-needle aspiration diagnosis of ?H�rthle-cell neoplasm/follicular neoplasm with oncocytic features? denote increased risk of malignancy?

The thyroid fine-needle aspiration (FNA) diagnosis of Hürthle-cell neoplasm (HCN)/follicular neoplasm with oncocytic features (FNOF) does not differentiate between Hürthle-cell adenoma and carcinoma. A majority of cases diagnosed as HCN undergo surgical excision for definite characterization. The aim of this study was to determine the risk of malignancy in cases diagnosed as HCN and identify clinical features that may help in predicting malignancy in patients with FNA diagnosis of HCN. We reviewed a cohort of 206 cases of thyroid FNA diagnosed as HCN; histological follow-up was available in 169 (82%) cases. The cases were evaluated for patient's age, sex, and size of the nodule and histological diagnosis. One hundred and sixty-six were female patients and 40 were male patients (age range, 12-83 yr). The histological diagnoses were benign in 93 (93/169, 55%) cases and malignant in 76 (76/169, 45%) cases. The malignant histological diagnoses were Hürthle-cell carcinoma (HCC), 53 cases; papillary thyroid carcinoma, 19 cases; follicular carcinoma, 3 cases; and medullary carcinoma, 1 case. The risk of malignancy was greater in nodules measuring > or =2 cm (55% vs. 45%; P value < 0.0001) in patients who were > or =40 yr old (82% vs. 18%, P value < 0.0001) than in patients <40 yr. The risk of malignancy was found greater in male patients than in female patients (61% vs. 43%); however, the difference was not statistically significant. The diagnosis HCN/FNOF carries a higher risk of malignancy as compared with a diagnosis of follicular lesion/neoplasm (20% malignancy rate from previously published studies). Clinical features including size of the nodule, age, and possibly sex of the patient can be a part of the decision analysis in selecting a patient for surgery.

Molecular pathogenesis of thyroid cancer

A number of molecular abnormalities have been described in association with the progression from normal thyroid tissue to benign adenomas to well-differentiated and finally anaplastic epithelial thyroid cancer. These include upregulation of proliferative factors, such as growth hormones and oncogenes, downregulation of apoptotic and cell-cycle inhibitory factors, such as tumor suppressors, disruption of normal cell-to-cell interactions, and cellular immortalization. The progression model for thyroid carcinoma has not been proven, but evidence suggests that an evolutionary molecular process is involved, especially in the development of follicular thyroid cancers for which there are distinct intermediate phenotypes. We present a comprehensive evaluation of factors involved in thyroid tumorigenesis and attempt to describe preliminary attributes of a progression model. The organization of this model should also provide a template for the incorporation of new information as it is derived from large-scale genomic studies.

p53 abnormalities are rare events in neuroendocrine (Merkel cell) carcinoma of the skin. An immunohistochemical and SSCP analysis

The aim of the present study was to assess a possible role of the tumour suppressor gene p53 in neuroendocrine (Merkel cell) carcinoma of the skin with regard to tumour development and tumour progression. p53 was investigated in a series of routinely processed Merkel cell carcinomas, with application of four different p53 antibodies (CM-1, PAb1801, DO7, and PAb240) to 25 carcinomas and screening for p53 mutations of exons 4-8 by single-strand conformation polymorphism (SSCP) analysis in 9 cases. All 25 tumours in the present series showed the characteristic microscopic and immunohistochemical features of Merkel cell carcinoma of the skin. In 5 of the 25 Merkel cell carcinomas investigated 5-10% of tumour cell nuclei showed a positive p53 reaction with at least one anti-p53 antibody. A few scattered p53 positive nuclei were found in an additional 9 cases. The remaining 11 cases completely lacked p53 immunostaining. SSCP analysis of exons 4-8 revealed no significant alterations in the mobility shift of the single strand DNAs in the five cases with 5-10% p53-immunoreactive tumour nuclei or in five cases lacking p53 accumulation significant. Our results suggest that alterations of the p53 gene play only a minor part in the development or progression of Merkel cell carcinoma of the skin.