RET/PTC rearrangements in Hashimoto's thyroiditis

Role of NF-kappaB in thyroid cancer

Thyroid cancer is the most common neoplasia of the endocrine system and accounts for approximately 1% of all newly diagnosed cancer cases. Its incidence has rapidly grown over the past few decades. Although most thyroid carcinomas are of the well-differentiated papillary histology, and respond well to treatment with surgical resection followed by radioactive iodine ablation, tumors with more aggressive phenotype, such as follicular, poorly differentiated, anaplastic, and medullary cancers, lead to almost 1500 patient deaths annually. Therefore, understanding molecular mechanisms that regulate the biology of these carcinomas could be helpful to identify new molecules acting as novel targets for therapeutic intervention. NF-kappaB has been recently shown to play an important role in thyroid cancer for its ability to control the proliferative and the anti-apoptotic signaling pathways of thyroid neoplastic cells. Oncogenic proteins RET/PTC, RAS and BRAF, that are involved in many aspects of thyroid carcinogenesis, can induce NF-kappaB activation in papillary, follicular, and medullary thyroid carcinomas, while constitutive de-regulated NF-kappaB activity has been found in anaplastic thyroid carcinomas. A number of NF-kappaB inhibitors have been demonstrated to induce anti-proliferative effects and/or massive apoptosis, especially in combination with radio- or chemo-therapy. The results obtained suggest that targeting NF-kappaB could be a promising strategy for advanced thyroid cancer treatment.

Immunohistochemical and electron microscopy studies of a case of hyalinizing trabecular tumor of the thyroid gland, with special consideration of the hyalinizing mass associated with it

Hyalinizing trabecular tumor (HTT) of the thyroid gland is rare and benign, and it neither recurs nor metastasizes. In this lesion, tumor cells are arranged in trabeculae, in association with hyalinizing mass in the stroma. The origin and nature of the hyalinizing mass are still controversial. We report here a case of HTT with cytological, immunohistochemical, and ultrastructural findings, focused in particular on the hyalinizing mass. Cytologically, tumor cells exhibiting many intranuclear cytoplasmic inclusions and nuclear grooves were found in association with light green-positive, irregular, fluffy membranous structures on touch smear. Staining with antibody to collagen type IV was positive in these membranous structures. Histopathologically, tumor cells exhibited many intranuclear cytoplasmic inclusions, and were positive for staining with antibodies to S100 protein, neuron-specific enolase, thyroglobulin, and vimentin. The hyalinizing eosinophilic mass, which was positive for PAS reaction, and for staining by antibody to collagen type IV, gradually increased in the areas surrounding tumor cells. This mass then appeared to replace the tumor cells, and exhibited a peculiar filiform pattern. We demonstrated ultrastructurally that this pattern was composed of long, irregular, fine cytoplasmic processes of tumor cells and basal lamina-like substance in the hyalinizing mass. In fact, the homogeneous hyalinizing mass, similar to basal lamina-like substance, contained many degenerated cytoplasmic processes at the ultrastructural level. These results suggested that the key cytological finding in differentiating HTT from papillary carcinoma is the fluffy membranous structure, although nuclear pseudoinclusions are important as well. The filiform pattern noted at light microscopic level consisted of long cytoplasmic processes of tumor cells and hyalinized mass at the ultrastructural level.

BRAFV600E mutation and X-linked inhibitor of apoptosis expression in papillary thyroid carcinoma

BACKGROUND

The BRAF mutation V600E (BRAF(V600E)) is the most common genetic alteration in papillary thyroid carcinoma (PTC), while overexpression of X-linked inhibitor of apoptosis (XIAP) has been found in various tumors. Both of these events are implicated in carcinogenesis, tumor progression, recurrence, etc. There are few reports, however, of the BRAF(V600E) mutation and XIAP overexpression in PTC patients. The aim of this study was to investigate the frequency of the BRAF(V600E) mutation in PTC and its relationship to clinicopathological parameters and the expression of XIAP.

METHODS

Genomic DNA was extracted from 123 paraffin-embedded PTC tumor tissue samples and amplified for analysis of the V600E mutation in exon 15 of the BRAF gene by polymerase chain reaction. XIAP expression was examined by immunohistochemical methods in 46 PTCs, 18 benign nodular goiters, and 10 Hashimoto's thyroiditis samples.

RESULTS

The BRAF(V600E) mutation was found in 34.1% of PTC, and was especially prevalent in the classic type. BRAF(V600E) was significantly correlated with younger age at diagnosis (p = 0.026), tumor size (p = 0.009), and histological variants (p = 0.024). There was a trend towards association with extrathyroidal invasion (p = 0.067). By logistic regression analysis, a significant relationship was found between tumor size and the BRAF(V600E) mutation (p = 0.03). XIAP was expressed in 82.6% of PTCs, which was a higher percentage than observed in the group of benign thyroid disorders (35.7%, p < 0.001). Neither the intensity (p = 0.611) nor the extent (p = 0.723) of XIAP staining was correlated with the presence of BRAF(V600E) in PTC patients.

CONCLUSIONS

These data indicate that BRAF(V600E) is associated some of the aggressive clinicopathological features of PTC including younger age at diagnosis, larger tumor size, and classic histological type, as well as also extrathyroidal invasion. XIAP-positive staining was more prevalent in PTCs than in the benign thyroid disorders. Although BRAF(V600E) and XIAP expression are commonly seen in PTC, their presence together seems unrelated.

Inhibition of oncogene-induced inflammatory chemokines using a farnesyltransferase inhibitor

Background

Farnesyltransferase inhibitors (FTI) are small molecule agents originally formulated to inhibit the oncogenic functions of Ras. Although subsequent analysis of FTI activity revealed wider effects on other pathways, the drug has been demonstrated to reduce Ras signaling by direct measurements. The purpose of the current study was to determine if FTI could be used to inhibit the inflammatory activities of a known Ras-activating human oncoprotein, RET/PTC3. RET/PTC3 is a fusion oncoprotein expressed in the thyroid epithelium of patients afflicted with thyroid autoimmune disease and/or differentiated thyroid carcinoma. Previous studies have demonstrated that RET/PTC3 signals through Ras and can provoke nuclear translocation of NFκB and the downstream release of pro-inflammatory mediators from thyroid follicular cells in vitro and in vivo, making it an ideal target for studies using FTI.

Methods

For the studies described here, an in vitro assay was developed to measure FTI inhibition of RET/PTC3 pro-inflammatory effects. Rat thyrocytes transfected with RET/PTC3 or vector control cDNA were co-cultured with FTI and examined for inhibition of chemokine expression and secretion measured by RT-PCR and ELISA. Immunoblot analysis was used to confirm the level at which FTI acts on RET/PTC3-expressing cells, and Annexin V/PI staining of cells was used to assess cell death in RET/PTC3-expressing cells co-cultured with FTI.

Results

These analyses revealed significant mRNA and protein inhibition of chemokines Ccl2 and Cxcl1 with nanomolar doses of FTI. Neither RET/PTC3 protein expression nor apoptosis were affected at any dose of FTI investigated.

Conclusion

These data suggest that FTI may be applied as an effective inhibitor for RET/PTC3-oncogene induced pro-inflammatory mediators.

Immunohistochemical detection of X-linked inhibitor of apoptosis (XIAP) in neoplastic and other thyroid disorders

The X-linked inhibitor of apoptosis (XIAP) is the most potent of the inhibitors of apoptosis, a group of related caspase inhibitors. X-linked inhibitor of apoptosis expression correlates with radio- and chemoresistance and clinical aggressiveness in certain tumors. XIAP expression was examined in 106 specimens from neoplastic and other thyroid disorders, which underwent citrate-based antigen retrieval and staining with monoclonal anti-XIAP. Normal thyroid was XIAP-negative. Of 35 papillary thyroid carcinomas (PTCs), 29 (83%) stained variably in intensity and/or extent. An insular carcinoma was strongly positive and 1 of 4 anaplastic carcinomas moderately positive. Follicular, medullary, and 3 of 4 anaplastic carcinomas, oncocytic neoplasms, and a hyalinizing trabecular tumor were nonstaining. Hashimoto's thyroiditis and adenomatous goiters were either nonstaining or occasionally stained in oncocytic foci. Because XIAP was highly specific for PTC among the thyroid neoplasms, it may be a useful marker for differential diagnosis when used alone or in combination with other markers. XIAP may also be useful in differentiating insular carcinoma from follicular neoplasm in certain difficult cases. In addition, the selective expression of XIAP in PTC and some high-grade thyroid malignancies also provides clues to the role of the apoptotic pathway in the tumorigenesis of these neoplasms.

Hashimoto's thyroiditis with papillary thyroid carcinoma (PTC)-like nuclear alterations express molecular markers of PTC

AIMS

Focal papillary thyroid carcinoma (PTC)-like nuclear alterations have been documented in Hashimoto's thyroiditis; however, the molecular association between PTC and Hashimoto's thyroiditis is poorly understood. The aim of this study was to determine whether molecular expression patterns of PTC are present in association with PTC-like nuclear alterations in Hashimoto's thyroiditis.

METHODS AND RESULTS

The expression of four genes known to be up-regulated in PTC [LGALS3 (galectin3), CITED1, KRT19 (cytokeratin 19) and FN1 (fibronectin-1)] and the human mesothelial cell protein identified by monoclonal antibody HBME1 was evaluated. Immunohistochemistry was performed on 23 cases of Hashimoto's thyroiditis with focal or diffuse Hürthle cell change and PTC-like nuclear alterations, 37 PTC and 18 normal thyroids. Focal expression of galectin3 (GAL3), CITED1, cytokeratin 19 (CK19), HBME1 and fibronectin-1 (FN1) was seen in 87%, 65%, 43%, 26% and 17% of Hashimoto's thyroiditis, respectively, only in thyrocytes showing PTC-like nuclear alterations. In contrast, diffuse expression of GAL3, CITED1, CK19, HBME1 and FN1 was seen in 100%, 95%, 70%, 87% and 89% of PTC, respectively. Normal thyroid tissues did not express any of these proteins. Following immunohistochemistry, four Hashimoto's thyroiditis cases were found to contain foci of PTC. These foci were highlighted by the diffuse and strong expression of PTC-associated proteins, which prompted additional retrospective scrutiny of the haematoxylin and eosin-stained sections leading to appreciation of complete PTC-type nuclear atypia.

CONCLUSIONS

Focal PTC-like immunophenotypic changes in Hashimoto's thyroiditis suggest the possibility of early, focal premalignant transformation in some cases of Hashimoto's thyroiditis.