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A mutation screening of oncogenes, tumor suppressor gene TP53 and nuclear encoded mitochondrial complex I genes in oncocytic thyroid tumors.

Evangelisti C, de Biase D, Kurelac I, Ceccarelli C, Prokisch H, Meitinger T, Caria P, Vanni R, Romeo G, Tallini G, Gasparre G, Bonora E - BMC Cancer (2015)

Bottom Line: The series of analyzed cases did not include poorly- or undifferentiated thyroid carcinomas, and none of the TP53 mutated cases had significant mitotic activity or high-grade features.Thus, the presence of disruptive TP53 mutations was completely unexpected.In addition, novel mutations in nuclear-encoded complex I genes were identified.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical and Surgical Sciences (DIMEC), Policlinico S. Orsola-Malpighi, Unit of Medical Genetics, University of Bologna, Bologna, Italy. cecilia.evangelisti2@unibo.it.

ABSTRACT

Background: Thyroid neoplasias with oncocytic features represent a specific phenotype in non-medullary thyroid cancer, reflecting the unique biological phenomenon of mitochondrial hyperplasia in the cytoplasm. Oncocytic thyroid cells are characterized by a prominent eosinophilia (or oxyphilia) caused by mitochondrial abundance. Although disruptive mutations in the mitochondrial DNA (mtDNA) are the most significant hallmark of such tumors, oncocytomas may be envisioned as heterogeneous neoplasms, characterized by multiple nuclear and mitochondrial gene lesions. We investigated the nuclear mutational profile of oncocytic tumors to pinpoint the mutations that may trigger the early oncogenic hit.

Methods: Total DNA was extracted from paraffin-embedded tissues from 45 biopsies of oncocytic tumors. High-resolution melting was used for mutation screening of mitochondrial complex I subunits genes. Specific nuclear rearrangements were investigated by RT-PCR (RET/PTC) or on isolated nuclei by interphase FISH (PAX8/PPARγ). Recurrent point mutations were analyzed by direct sequencing.

Results: In our oncocytic tumor samples, we identified rare TP53 mutations. The series of analyzed cases did not include poorly- or undifferentiated thyroid carcinomas, and none of the TP53 mutated cases had significant mitotic activity or high-grade features. Thus, the presence of disruptive TP53 mutations was completely unexpected. In addition, novel mutations in nuclear-encoded complex I genes were identified.

Conclusions: These findings suggest that nuclear genetic lesions altering the bioenergetics competence of thyroid cells may give rise to an aberrant mitochondria-centered compensatory mechanism and ultimately to the oncocytic phenotype.

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Related in: MedlinePlus

PAX8/PPARγrearrangement observed in isolated nuclei from an oncocytic tumor biopsy. The white arrow indicates the gene fusion observed with the two differently labeled probes. See text for details.
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Fig1: PAX8/PPARγrearrangement observed in isolated nuclei from an oncocytic tumor biopsy. The white arrow indicates the gene fusion observed with the two differently labeled probes. See text for details.

Mentions: To identify the PAX8/PPARγ rearrangement, a dual-color single-fusion home-brew probe containing BACs RP11-339 F22 (for PAX8) labeled with Spectrum Orange (Abbott Molecular/Vysis Downers Grove, IL) and RP11-167 M22 (for PPARγ) labeled with Spectrum Green (Abbott Molecular/Vysis) was designed. Cytogenetic and fluorescence in situ hybridization (FISH) studies were performed as described [18]. Evaluation of the results was done by counting 25–105 nuclei (mean 65) per case, depending on the quality of preparations, using a digital image analysis system based on an epifluorescence Olympus BX41 microscope and charge-coupled device camera (Cohu), interfaced with the CytoVysion system (software 2.81 Applied Imaging, Pittsburg, PA, USA). Normal nuclei were identified by two orange and two green FISH signals, nuclei with PAX8/PPARγ gene fusion were identified by one orange, one green and one fused orange/green signal. An example of the observed nuclear pattern is reported in Figure 1.Figure 1


A mutation screening of oncogenes, tumor suppressor gene TP53 and nuclear encoded mitochondrial complex I genes in oncocytic thyroid tumors.

Evangelisti C, de Biase D, Kurelac I, Ceccarelli C, Prokisch H, Meitinger T, Caria P, Vanni R, Romeo G, Tallini G, Gasparre G, Bonora E - BMC Cancer (2015)

PAX8/PPARγrearrangement observed in isolated nuclei from an oncocytic tumor biopsy. The white arrow indicates the gene fusion observed with the two differently labeled probes. See text for details.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4374372&req=5

Fig1: PAX8/PPARγrearrangement observed in isolated nuclei from an oncocytic tumor biopsy. The white arrow indicates the gene fusion observed with the two differently labeled probes. See text for details.
Mentions: To identify the PAX8/PPARγ rearrangement, a dual-color single-fusion home-brew probe containing BACs RP11-339 F22 (for PAX8) labeled with Spectrum Orange (Abbott Molecular/Vysis Downers Grove, IL) and RP11-167 M22 (for PPARγ) labeled with Spectrum Green (Abbott Molecular/Vysis) was designed. Cytogenetic and fluorescence in situ hybridization (FISH) studies were performed as described [18]. Evaluation of the results was done by counting 25–105 nuclei (mean 65) per case, depending on the quality of preparations, using a digital image analysis system based on an epifluorescence Olympus BX41 microscope and charge-coupled device camera (Cohu), interfaced with the CytoVysion system (software 2.81 Applied Imaging, Pittsburg, PA, USA). Normal nuclei were identified by two orange and two green FISH signals, nuclei with PAX8/PPARγ gene fusion were identified by one orange, one green and one fused orange/green signal. An example of the observed nuclear pattern is reported in Figure 1.Figure 1

Bottom Line: The series of analyzed cases did not include poorly- or undifferentiated thyroid carcinomas, and none of the TP53 mutated cases had significant mitotic activity or high-grade features.Thus, the presence of disruptive TP53 mutations was completely unexpected.In addition, novel mutations in nuclear-encoded complex I genes were identified.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical and Surgical Sciences (DIMEC), Policlinico S. Orsola-Malpighi, Unit of Medical Genetics, University of Bologna, Bologna, Italy. cecilia.evangelisti2@unibo.it.

ABSTRACT

Background: Thyroid neoplasias with oncocytic features represent a specific phenotype in non-medullary thyroid cancer, reflecting the unique biological phenomenon of mitochondrial hyperplasia in the cytoplasm. Oncocytic thyroid cells are characterized by a prominent eosinophilia (or oxyphilia) caused by mitochondrial abundance. Although disruptive mutations in the mitochondrial DNA (mtDNA) are the most significant hallmark of such tumors, oncocytomas may be envisioned as heterogeneous neoplasms, characterized by multiple nuclear and mitochondrial gene lesions. We investigated the nuclear mutational profile of oncocytic tumors to pinpoint the mutations that may trigger the early oncogenic hit.

Methods: Total DNA was extracted from paraffin-embedded tissues from 45 biopsies of oncocytic tumors. High-resolution melting was used for mutation screening of mitochondrial complex I subunits genes. Specific nuclear rearrangements were investigated by RT-PCR (RET/PTC) or on isolated nuclei by interphase FISH (PAX8/PPARγ). Recurrent point mutations were analyzed by direct sequencing.

Results: In our oncocytic tumor samples, we identified rare TP53 mutations. The series of analyzed cases did not include poorly- or undifferentiated thyroid carcinomas, and none of the TP53 mutated cases had significant mitotic activity or high-grade features. Thus, the presence of disruptive TP53 mutations was completely unexpected. In addition, novel mutations in nuclear-encoded complex I genes were identified.

Conclusions: These findings suggest that nuclear genetic lesions altering the bioenergetics competence of thyroid cells may give rise to an aberrant mitochondria-centered compensatory mechanism and ultimately to the oncocytic phenotype.

Show MeSH
Related in: MedlinePlus