Thyroid Cancer With Autocrine Sialyl-fibronectin Depletion Has a Poor Prognosis due to EMT Progression

Elevated blood fibronectin (FN) levels have been observed in various cancers; however, their significance remains controversial. Herein, we measured the levels of sialyl-fibronectin (S-FN), a type of FN secreted by tumor cells, and investigated whether blood S-FN secretion is associated with recurrent metastasis and epithelial-mesenchymal transition (EMT).

An ELISA system recognizing S-FN was constructed, and the amount of S-FN in blood samples from 63 patients with thyroid carcinoma was measured. The relationship between S-FN secretion and clinical prognosis was also examined. Vimentin immunostaining was performed to identify the mesenchymal status of the cells during EMT.

After 12 years of observation, 17/63 patients had recurrent metastases, including nine cases of lymph node recurrence (LNR) and eight cases of remote metastasis (RM). LNR occurred in 7/39 (17.9%) of S-FN-negative cases, where 4/7 (57.1%) had two or more repeat recurrences. In S-FN-positive cases, LNR was observed in 2/24 cases (8.3%), and no repeat recurrence was observed. For RM, 6/39 (15.4%) patients were S-FN-negative, of which 5/6 (83.3%) had progressive disease even during treatment at metastasis. Of the S-FN-positive cases, RM was observed in 2/24 (8.3%) patients; progressive disease was observed in 1/2 (50.0%) patients. In 9/11 S-FN-negative recurrent metastasis cases (81.8%) and 2/4 S-FN-positive cases (50.0%), many vimentin-positive, FN-secreting cells were found in the interstitial tissue around the tumor.

S-FN-negative thyroid cancer has a poor prognosis because of the progression of EMT associated with increased paracrine FN levels in the stroma.