Tumor budding correlates with poor prognosis and epithelial-mesenchymal transition in tongue squamous cell carcinoma

Abstract

Background: Tumor budding is a readily detectable histopathological feature and has been recognized as an adverse prognostic factor in several human cancers. However, the prognostic value of tumor budding in tongue squamous cell carcinoma (TSCC) has not been reported. The purpose of this study was to assess the correlation of tumor budding with the clinicopathologic features, and the known molecular biomarkers (E-cadherin and Vimentin), as well as to evaluate its prognostic significance for TSCC.

Methods: Archival clinical samples of 230 patients with TSCC were examined for tumor budding. Immunohistochemistry analyses were performed to examine the expression of E-cadherin and Vimentin. Statistical analyses were carried out to assess the correlation of tumor budding with clinicopathologic parameters and patient survival. The potential association between tumor budding and alterations of E-cadherin and Vimentin expression was also assessed.

Results: Of the 230 TSCC cases examined, tumor budding was observed in 165 cases (71.7%), with a mean tumor bud count of 7.5 (range from 1 to 48 buds). High-intensity budding (≥5 tumor buds) was observed in 111 cases (48.3%). Statistical analysis revealed that tumor budding was associated with tumor size (P < 0.05), differentiation (P < 0.05), clinical stage (P < 0.05), lymph node metastasis (P < 0.01), and correlated with reduced overall survival. In addition, significant associations were observed among tumor budding and the deregulation of E-cadherin (P < 0.001) and Vimentin (P < 0.001).

Conclusions: Tumor budding, which associates with epithelial-mesenchymal transition, is a frequent event and appears to be an independent prognostic factor in TSCC.

Figure 1. Histopathological analyses of tumor budding in tongue squmous cell carcinoma

Histopathological analyses were performed as described in Material and Methods to identify tumor buds in the invasion front of the TSCC. (A) Tumor budding at the invasive front in tongue squmous cell carcinoma (H&E, 20×). (B) Tumor budding with hyperchromatic nuclei in an H&E section (40×). Tumor buds were identified with arrowheads.

Figure 2. The effects of tumor budding on prognosis

Kaplan-Meier plots of overall survival in patient groups defined by intensity of tumor budding (High-intensity tumor budding: ≥5 tumor buds, Low-intensity or No tumor budding: < 5 tumor buds or no tumor bud detectable). The difference in survival rates is statistically significant (p<0.001).

Figure 3. Immunohistochemistry analyses of E-cadherin and Vimentin expression in the tumor budding cells

Immunohistopathological analyses were performed as described in Material and Methods to evaluate the expression of E-cadherin and Vimentin expression in tumor budding cells. Strong staining of E-cadherin protein was detected at the cytoplasmic membrane and the intercellular borders in the adjacent non-cancerous epithelium and in the center/superficial tumor parts (A and B, 40×). In contrast, cancer cells at the tumor budding site showed negative or weak (dot-like) membranous immunostaining for E-cadherin (C, 40×, arrow). As shown in D and E, no Vimentin staining was observed in adjacent non-cancerous epithelium or in the center/superficial tumor parts (20×). In contrast, strong Vimentin staining was detected in the ITF and tumor budding cells (F). A subset of cancer cells at budding site also exhibits a spindle-like morphology (40×, arrow).