Affiliations: [a] Department of Thyroid Surgery, the Affiliated Hospital of Qingdao University, Qingdao, Shandong, China | [b] Department of Clinical Laboratory, the Women and Children's Hospital of Qingdao, Qingdao, Shandong, China | [c] Department of Pathology, the Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
Correspondence:
[*]
Corresponding author: Kejun Zhang, Department of Thyroid Surgery, the Affiliated Hospital of Qingdao University, Qingdao, Shandong, China. E-mail:zkejun@yahoo.ca
Note: [1] These authors equal to the study.
Abstract: Anaplastic thyroid cancer (ATC) is a locally aggressive type of thyroid
tumor with high rate of distant metastases. It is often incurable because it
does not respond to radioiodine, radiotherapy, or chemotherapy. With
conventional treatment, the median survival is about 6 months; therefore,
new treatment options are needed. S100A4 is a calcium-binding protein
related to the metastatic potential of carcinoma. Previous study has found
S100A4 was overexpressed in human papillary thyroid carcinomas (PTC)
tissues, and overexpression of S100A4 is associated with thyroid tumour
invasion and metastasis. In the present study, we first examined S100A4
protein expression in 14 ATC tissues, 20 PTC tissues and 14 normal thyroid
tissue by immunohistochemistry analysis. We then knocked down of S100A4
expression by RNA interference (S100A4 siRNA) and investigated its effects
on growth and metastasis in two human ATC cell lines 8505C (BRAFV600E)
and Cal-62 (BRAFwt) in vitro and in vivo. S100A4 and BRAFV600E
protein expression was evaluated by western blot assay and
immunohistochemistry analysis. Using immunohistochemistry, we found that
high levels of S100A4 were detected in ATC specimens and PTC specimens. No
S100A4 staining was observed in normal thyroid tissues. S100A4 siRNA
significantly decreased proliferation and increased apoptosis, and inhibited
the invasive potential of the two cells in vitro. In addition, S100A4 siRNA
could effectively inhibit BRAFV600E expression in the 8505C cells, and
treatment with 100 ng/ml human recombinant BRAF V600E in S100A4 siRNA/8505C
cells could partly restore its proliferative and invasive ability. Results
of implantation in vivo showed S100A4 shRNA could significantly inhibit
abdominal cavity metastasis and tumor growth in vivo. Furthermore, knockdown
of S100A4 has significant role on invasion, metastasis and growth inhibition
in the 8505C cells than that of in the Cal-62 cells. These results support
the hypothesis that S100A4 contributes significantly to growth and
metastasis, and that down-regulation of S100A4 expression decreases the
metastatic potential of ATC cells. Furthermore, down-regulation of S100A4
expression is more marked in BRAFV600E cells than that of in the
BRAFwt cells.
