Expression of cancer stem cell markers and epithelial-mesenchymal transition-related factors in anaplastic thyroid carcinoma

Abstract

Background: Anaplastic thyroid carcinoma (ATC) is an undifferentiated tumor of the thyroid that has poor prognosis owing to its aggressive behavior and resistance to current treatments. We hypothesized that the stem cell properties induced by the epithelial-mesenchymal transition (EMT) was one of reasons for the dismal outcome of ATC.

Materials and methods: Paraffin blocks and slides of 17 ATC cases were retrieved. We also collected 60 cases of papillary thyroid carcinoma (PTC) for comparison. We used immunohistochemistry to examine the expression of multiple markers of cancer stem cells and EMT-activating transcriptional factors.

Results: Majority of ATC cases showed loss of epithelial (E)-cadherin expression (15/17); however, all PTC cases (60/60) retained E-cadherin expression. EMT-activating transcription factors, such as snail and slug, were more frequently expressed in ATC than PTC cases (35.3% versus 6.7%, 76.5% versus 5%, respectively). Cancer stem cell markers such as CD133 and nestin were more highly expressed in ATC than PTC (52.9% versus 5%, 52.9% versus 0%, respectively).

Conclusion: We found that the expression of EMT-related factors and stem cell markers was higher in ATC than PTC. We therefore conclude that stemness induced by EMT plays an important role in the pathogenesis of ATC.

Keywords: Epithelial-mesenchymal transition (EMT); anaplastic thyroid carcinoma (ATC); cancer stem cell; immunohistochemistry.

Figure 1

The expression of EMT-related markers in ATC and PTC. ATC cells show mesenchymal features (A) and frequently show loss of E-cadherin expression (B). Snail and slug proteins are expressed in the nucleus of ATC cells and this staining is regarded as positive (C and E). Cytoplasmic staining is defined as negative (D and F). Representative hematoxylin and eosin staining (G) and staining for E-cadherin (H), snail (I, J), and slug (K, L) in PTC cases. All PTC cases show characteristic nuclear features of PTC (G) and retain E-cadherin expression (H). A small percentage of PTC cases are immunoreactive for snail (I) and slug (K), and almost all cases reveal no immunoreactivity for snail (J) and slug (L). Original magnification: ×200.

Figure 2

The expression of cancer stem cell markers in ATC and PTC. CD133 and nestin are highly over-expressed in the membrane and cytoplasm of ATC cells and this staining is regarded as positive (A and C). ATC cases showing very weak cytoplasmic staining for CD133 (B) and nestin (D) were regarded as a negative. Representative images of staining for CD133 (E, F) and nestin (G) in PTC cases. A few PTC cases reveal positive staining for CD133 (E) and almost cases show negative staining for CD133 (F). All PTC cases show no immunoreactivity for nestin (G). Original magnification: ×200.

Figure 3

The BRAF mutation study was carried out using pyrosequencing with formalin-fixed paraffin-embedded tissue. Representative images of mutant type (A, arrow indicates the mutation site) and wild type (B). All the BRAF mutated cases had T>A transition change of a single amino acid, from valine to glutamic acid (V600E).