Loss of expression of the oncosuppressor PTEN in thyroid incidentalomas associates with GLUT1 plasmamembrane expression.

AIM: Molecular imaging diagnosis with FDG-PET ((18)F-fluorodeoxyglucose positron emission tomography with computed tomography) can reveal the presence of un-suspected thyroid cancer that are referred to as "incidentaloma" because of the incidental finding. The glucose analogue (18)FDG is internalized in the cells by glucose transporters belonging to the GLUTs family. The surface expression of GLUT is under the control of the PI3k/Akt pathway. PTEN is an oncosuppressor frequently mutated or deleted in thyroid cancers. The lipid phosphatase activity of wild type PTEN switches off the Akt pathway. Here we tested the hypothesis that PTEN expression might affect the surface expression of GLUT1 and therefore influence the possibility of "incidental" detection of thyroid cancer based on FDG-PET.

METHODS

The biopsy of 8 patients, who were incidentally diagnosed with PTC by (18)F-fluorodeoxyglucose positron emission tomography with computed tomography, was assayed by immunofluorescence for the co-expression of the PTEN oncosuppressor and of GLUT1.

RESULTS

Loss of PTEN expression was detected in the majority of investigated cases (N.=6/8). Strikingly, while the two PTEN positive cases were negative for GLUT1 expression, the PTEN negative cases showed intense expression of GLUT1 at the cell surface.

CONCLUSION

The present observations, though made in a limited number of cases, suggest that PTEN negative thyroid cancers have high chances to be revealed as incidentalomas at FDG-PET.