Fine-needle aspiration biopsy-RT-PCR expression analysis of prothymosin alpha and parathymosin in thyroid: novel proliferation markers?

Fine-needle aspiration biopsy-based cytology has become an established and reliable diagnostic preoperative test in the evaluation of thyroid nodules. Despite the high specificity and sensitivity of the method, results might be doubtful in a significant number of cases. Genetic analysis of the aspirates by RT-PCR may contribute, in parallel to the cytology report, to a more precise diagnosis. Prothymosin alpha and parathymosin are two homologous chromatin remodeling proteins essential for cell cycle progression and proliferation of either normal or malignant cells. A semi-quantitative RT-PCR assay was developed to determine prothymosin alpha and parathymosin mRNA expression patterns in thyroid follicular cells obtained from the fine-needle aspiration biopsy specimens of patients diagnosed with simple nodular goitre, follicular adenoma, papillary and follicular well-differentiated carcinomas. Prothymosin alpha and parathymosin mRNA levels were found significantly elevated in well-differentiated carcinomas in relation to adenomas (p<0.05) and goitres (p<0.05), an event possibly linked to the proliferation activity of thyroid follicular cells. Further studies are required to establish prothymosin alpha and parathymosin as diagnostic proliferation markers in thyroid cancer, especially in cases of undetermined cellular morphology of follicular origin which reflect the most common cytohistopathological discrepancies.

Transcription factor-mediated proliferation and apoptosis in benign and malignant thyroid lesions.

Transcription factors play an essential role in regulating both cell proliferation and programmed cell death. Proliferation and apoptosis-related transcription factor immunoexpression patterns were concomitantly investigated in tissue sections of normal thyroid, goiters, follicular adenomas and well-differentiated papillary and follicular carcinomas using antibodies against prothymosin alpha, E2F-1, p53, Bcl2, and Bax proteins. Proliferation and apoptotic indices were determined by Ki-67 immunoreactivity and the terminal deoxynucleotidyl transferase-mediated deoxy uridine triphosphate nick-end labeling technique, respectively. Prothymosin alpha and E2F-1 immunoexpression levels were found to be significantly elevated in well-differentiated carcinomas compared to adenomas, goiters and normal tissues (P < 0.05). Both proteins were directly correlated with the proliferation index (P < 0.05). E2F-1 was additionally correlated with the apoptotic index (P < 0.05). The majority of cases were negative for p53 staining. Positive Bcl2 immunostaining was detected in all thyroid histotypes. None of the normal tissues showed Bax immunoreactivity, while positive accumulation differed significantly between hyperplastic and neoplastic histotypes. Direct correlations were observed between prothymosin alpha and Bcl2 as well as between E2F-1 and Bax immunoexpression (P < 0.05). These data demonstrate that prothymosin alpha and E2F-1 are strongly involved in the proliferation processes of thyroid neoplasias. Furthermore, prothymosin alpha may promote cell survival through the Bcl2 anti-apoptotic pathway, while E2F-1-induced apoptosis via p53-independent pathways may be associated with transcriptional activation of bax pro-apoptotic gene.

Prothymosin alpha is localized in mitotic spindle during mitosis.

Prothymosin a is a small, acidic, ubiquitous protein, thought to play a role in cell proliferation, carcinogenesis and apoptosis. We have reported earlier that in the interphase nucleus prothymosin a exhibits a punctuated nuclear distribution associated with transcription sites. Moreover, the protein was found to localize in 1-6 subnuclear domains where PML and CstF64 proteins were also identified. In the present study we followed the subcellular distribution of prothymosin a during mitosis. Our data identify prothymosin a to colocalize with alpha-tubulin in the mitotic spindle throughout mitosis, and to decorate the midbody during cytokinesis. Moreover nocodazole treatment disrupted prothymosin alpha and alpha-tubulin colocalization at the centrosomes of the interphase cell. Prothymosin a was also found to decorate gamma-tubulin identified centrosomes, during mitosis. Taken together our colocalization study suggests involvement of prothymosin a, in the formation, maintenance, or functioning of the mitotic spindle.

Interferon induces the interaction of prothymosin-alpha with STAT3 and results in the nuclear translocation of the complex.

Interferons (IFNs) play critical roles in host defense by modulating the expression of various genes via tyrosine phosphorylation of STAT transcription factors. Many cytokines including IFNs induce tyrosine phosphorylation of the STAT3 transcription factor, which regulates acute phase gene expression. Using the yeast two-hybrid interaction trap, in which a tyrosine kinase is introduced into the yeast to allow tyrosine phosphorylation of bait proteins, prothymosin-alpha (ProTalpha) was identified to interact with the amino terminal half of tyrosine-phosphorylated STAT3. ProTalpha is a small, acidic, extremely abundant, and essential protein that may play a role in chromatin remodeling, and has been implicated in regulating the growth and survival of mammalian cells. Besides the interaction of tyrosine-phosphorylated STAT3 with ProTalpha in yeast cells, IFN induced the interaction of ProTalpha with STAT3 in mammalian cells, and this interaction was dependent on the tyrosine phosphorylation of STAT3. Moreover, IFNalpha induces the translocation of STAT3 and ProTalpha from the cytoplasm to the nucleus where these proteins colocalize. Since ProTalpha has an extremely strong nuclear localization and STAT proteins apparently lack any nuclear localization signals, the association of STAT3 with ProTalpha may provide a mechanism to result in STAT localization in the nucleus.

Additional proteins in BAL fluid of Metsovites environmentally exposed to asbestos: more evidence of "protection" against neoplasia?

INTRODUCTION: Inhabitants of Metsovo in northwest Greece have been exposed to asbestos from use of a tremolite-containing whitewash ("luto" soil). As a result, they have increased incidence of malignant pleural mesothelioma and pleural calcifications (PCs). However, subjects with calcifications have a much lower incidence of mesothelioma than those without. A previous study of the two groups with BAL revealed higher proportional lymphocytosis among subjects with calcifications. We suggested that BAL lymphocytosis may be somehow correlated with "protection" against neoplasia. METHODS: The present report is a study of the liquid phase of BAL in the two groups. BAL specimens of 43 Metsovites (13 subjects with PCs and 30 subjects without PCs) and two control groups were examined. We measured total protein, albumin, IgG, IgA, and interleukin-6. Proteins were analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional electrophoresis and further characterized using an appropriate computer program. RESULTS: The most interesting finding was the presence of two additional protein spots corresponding to the electrophoretic site of Ig heavy chain and C(4) component of complement. The two proteins were present in all Metsovites with PCs but in none without PCs and also in none of the control groups. CONCLUSION: This study further separates two groups of Metsovites with different reaction to asbestos, possibly as a result of different activation of alveolar macrophages. This difference leads the first group to the formation of PCs, BAL fluid lymphocytosis, and relative "protection" against malignancy, and the second group to no calcifications, no lymphocytosis, but also no protection against malignancy.