Identification of differentially expressed proteins in papillary thyroid carcinomas with V600E mutation of BRAF

Multi-omics Signatures and Translational Potential to Improve Thyroid Cancer Patient Outcome

Recent advances in high-throughput molecular and multi-omics technologies have improved our understanding of the molecular changes associated with thyroid cancer initiation and progression. The translation into clinical use based on molecular profiling of thyroid tumors has allowed a significant improvement in patient risk stratification and in the identification of targeted therapies, and thereby better personalized disease management and outcome. This review compiles the following: (1) the major molecular alterations of the genome, epigenome, transcriptome, proteome, and metabolome found in all subtypes of thyroid cancer, thus demonstrating the complexity of these tumors and (2) the great translational potential of multi-omics studies to improve patient outcome.

Molecular Signature of Indeterminate Thyroid Lesions: Current Methods to Improve Fine Needle Aspiration Cytology (FNAC) Diagnosis

Fine needle aspiration cytology (FNAC) represents the gold standard for determining the nature of thyroid nodules. It is a reliable method with good sensitivity and specificity. However, indeterminate lesions remain a diagnostic challenge and researchers have contributed molecular markers to search for in cytological material to refine FNAC diagnosis and avoid unnecessary surgeries. Nowadays, several "home-made" methods as well as commercial tests are available to investigate the molecular signature of an aspirate. Moreover, other markers (i.e., microRNA, and circulating tumor cells) have been proposed to discriminate benign from malignant thyroid lesions. Here, we review the literature and provide data from our laboratory on mutational analysis of FNAC material and circulating microRNA expression obtained in the last 6 years.

Differentiated thyroid tumors: surgical indications

Thyroid gland tumors represent 1% of malignant tumors. In Italy their incidence is in constant growth. The aggressiveness depends on the histological type. The relative non-aggressive grade of different forms of tumors is the basis for discussing the treatment of choice: total thyroidectomy vs lobectomy with or without lymphadenectomy of the sixth level in the absence of metastasis. Authors report about their experience, and they advocate, given the high percentage of multicentric forms, total thyroidectomy as treatment of choice.

Increased type 3 deiodinase expression in papillary thyroid carcinoma

BACKGROUND

Thyroid hormone regulates a wide range of cellular activities, including the balance between cell proliferation and differentiation. The thyroid-hormone-inactivating type 3 deiodinase (DIO3, D3) has been shown to be reactivated in human neoplasias. Here, we evaluated DIO3 expression in human papillary thyroid carcinoma (PTC).

METHODS

Tumor and surrounding normal thyroid tissue were collected from 26 unselected patients with PTC. Clinical data were retrospectively reviewed in medical records. DIO3 mRNA levels were measured by real-time polymerase chain reaction and D3 activity by paper-descendent chromatography. Studies of DIO3 gene regulation were performed in a human PTC-derived cell line (K1 cells). BRAF(V600E) mutation was identified in DNA from paraffin-embedded tissues by direct sequencing. Immunohistochemistry analyses were performed using a specific human D3 antibody.

RESULTS

Increased D3 activity was detected in all 26 PTC samples analyzed as compared with adjacent thyroid tissue. The augmentations in D3 activity were paralleled by increased DIO3 mRNA levels (approximately fivefold). In PTC-derived cells, DIO3 transcripts were further upregulated by the transforming growth factor β1 (TGFβ1). Interestingly, preincubation with mitogen-activated protein kinase (MAPK) cascade inhibitors U0126 (ERK pathway) and SB203580 (p38 pathway) decreased DIO3 mRNA levels and blocked the TGFβ1-induced increase in DIO3 transcripts, suggesting that D3 induction might be mediated through the MAPK signaling pathway. Accordingly, DIO3 mRNA and activity levels were significantly higher in BRAF(V600E)-mutated samples (p=0.001). Increased D3 activity was correlated with tumor size (r=0.68, p=0.003), and associated with lymph node (p=0.03) or distant metastasis (p=0.006) at diagnosis. Conversely, decreased levels of the thyroid-hormone-activating type 2 deiodinase (DIO2) gene were observed in PTC, which might contribute to further decreases in intracellular thyroid hormone levels. Increased D3 expression was also observed in follicular thyroid carcinoma but not in medullary or anaplastic thyroid carcinoma samples.

CONCLUSIONS

These results indicate that the malignant transformation of thyroid follicular cell toward PTC promotes opposite changes in DIO3 and DIO2 expression by pretranscriptional mechanisms. The association between increased levels of D3 activity and advanced disease further supports a role for intracellular triiodothyronine concentration on the thyroid tumor cell proliferation or/and dedifferentiation.

Mortalin inhibition in experimental Parkinson's disease

Among heat shock proteins, mortalin has been linked to the pathogenesis of Parkinson's disease. In the present work a rat model of Parkinson's disease was used to analyze the expression of striatal proteins and, more specifically, mortalin expression. The possible involvement of mortalin in Parkinson's disease pathogenesis was further investigated by utilizing an electrophysiological approach and pharmacological inhibition of mortalin in both the physiological and the parkinsonian states. Proteomic analysis was used to investigate changes in striatal protein expression in the 6-hydroxydopamine rat model of Parkinson's disease. The electrophysiological effects of MKT-077, a rhodamine-123 analogue acting as an inhibitor of mortalin, were measured by field potential recordings from corticostriatal brain slices obtained from control, sham-operated, and 6-hydroxydopamine-denervated animals. Slices in the presence of rotenone, an inhibitor of mitochondrial complex I, were also analyzed. Proteomic analysis revealed downregulation of mortalin in the striata of 6-hydroxydopamine-treated rats in comparison with sham-operated animals. MKT-077 reduced corticostriatal field potential amplitude in physiological conditions, inducing membrane depolarization and inward current in striatal medium spiny neurons. In addition, we observed that concentrations of MKT-077 not inducing any electrophysiological effect in physiological conditions caused significant changes in striatal slices from parkinsonian animals as well as in slices treated with a submaximal concentration of rotenone. These findings suggest a critical link between mortalin function and mitochondrial activity in both physiological and pathological conditions mimicking Parkinson's disease.

Prohibitin is overexpressed in papillary thyroid carcinomas bearing the BRAF(V600E) mutation

BACKGROUND

Prohibitin (PHB) is a multifunctional protein that is localized in different intracellular sites. PHB may exert different roles in tumorigenesis, having either a permissive action on tumor growth or an oncosuppressor role, depending on the cellular context. The objective of this study was to evaluate PHB expression in normal thyroid tissues, thyroid follicular adenomas (FAs), and papillary thyroid carcinomas (PTCs).

METHODS

PHB expression was analyzed by immunohistochemistry, Western blot, and quantitative reverse transcription polymerase chain reaction (RT-PCR). Transfections in the BCPAP and TPC-1 thyroid cancer cell lines were used to evaluate the PHB promoter activity.

RESULTS

In terms of protein and mRNA levels, normal tissues from patients with serum thyrotropin (TSH) values >0.8mU/L had PHB levels that were significantly reduced compared to specimens from patients with serum TSH values <0.5mU/L, suggesting that TSH exerts an inhibitory effect on PHB expression. Consistent with this was the finding that the presence of TSH was associated with low PHB levels in normal FRTL5 thyroid cells. Immunohistochemical analysis showed relatively low and high PHB expression in FAs and PTCs, respectively. PHB mRNA and protein overexpression, as assessed by quantitative RT-PCR and Western blot, was noted only in PTCs bearing the BRAF(V600E) mutation. Notably, cell transfection experiments suggested that presence of the BRAF(V600E) mutation may be associated to increase of the PHB promoter activity.

CONCLUSIONS

PHB is overexpressed in PTCs bearing the BRAF(V600E) mutation. We postulate that the presence of the BRAF(V600E) mutation increases PHB promoter activity and therefore potentially mediates effects of this mutation on the behavior of BRAF(V600E) positive PTCs.