Co-expression of cytokeratin and vimentin in colorectal cancer highlights a subset of tumor buds and an atypical cancer-associated stroma

• Published in: Human pathology Vol. 87; pp. 18 - 27
• Main Authors: Meyer, Sara N., Galván, José A., Zahnd, Stefan, Sokol, Lena, Dawson, Heather, Lugli, Alessandro, Zlobec, Inti
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-05-2019; Elsevier Limited
• Subjects: Cancer-associated stroma; Classification; Colorectal cancer; Epithelial-mesenchymal transition; Fibroblasts; Lymphatic system; Mesothelial-mesenchymal transition; Metastasis; Tumor budding; Tumor budding; Epithelial-mesenchymal transition; Cancer-associated stroma; Mesothelial-mesenchymal transition; Colorectal cancer; Epithelial-Mesenchymal Transition, Mesothelial-Mesenchymal Transition; Colorectal Cancer; Tumor Budding; Cancer-Associated Stroma
• ISSN: 0046-8177; 1532-8392
• DOI: 10.1016/j.humpath.2019.02.002

Tumor buds in colorectal cancer are hypothesized to undergo a (partial) epithelial-mesenchymal transition (EMT). If so, cytokeratin (CK) and vimentin (VIM) co-expression is expected. CK+/VIM+ can also be found in some stromal cells; however, their origin remains unclear. Here, we determine the frequency of CK+/VIM+ tumor cells and characterize the CK+/VIM+ stroma in colorectal cancer. Three cell populations (CK+, VIM+, CK+/VIM+) were sorted using DepArray and fluorescence-activated cell sorting (FACS). Tumor areas were selected to include tumor center, stroma and tumor budding. Fluorescence microscopy was used to visualize co-expressing cells on whole slides. A next-generation tissue microarray (ngTMA) of matched Pan-CK–positive and -negative stroma was constructed and stained for E-cadherin, VIM, Snail1, Twist1, Zeb1 and Zeb2, COL11A1, SPARC, CD90, α-SMA, FAP and WT1. CK+/VIM+ co-expressing tumor cells were detected using all three methods. With DepArray, only tumor budding areas contained CK+/VIM+ cells. The proportion of CK+/VIM+ tumor cells was low (1.5%–22%). CK+ stroma was associated with aggressive tumor features like distant metastasis (P = .0003), lymphatic invasion (P = .0009) and tumor budding (P = .0084). CK+/VIM+ stroma was characterized by positive WT1 (P < .001), ZEB2 (P < .001), TWIST1 (P = .009), and FAP (P = .003). Our data suggest that CK+/VIM+ tumor cells exist, albeit in low numbers and could represent a subgroup of tumor buds in partial EMT. CK+/VIM+ stroma may be of mesothelial origin and shows features of mesenchymal cells and cancer-associated fibroblasts. These results, together with the association with metastasis point to cells in mesothelial-mesenchymal transition (MMT). This atypical stroma may be a potential target for therapy.
•CK+/VIM+ tumor cells exist in colorectal cancer, as shown using DepArray, FACS, and confocal microscopy and are located in tumor budding regions.•These CK+/VIM+ tumor cells comprise 1.5% to 22% of the CK-positive cell population.•CK+/VIM+ stroma is associated with aggressive tumor behavior including metastasis.•This double-positive stroma expresses significantly more WT1, ZEB2, TWIST1 and FAP compared to CK-negative tumor-associated stroma but shows no difference in E-cadherin, SNAIL1, ZEB1, COL11A1, SPARC, CD90, or α-SMA.•These results suggest that double-positive fibroblasts are experiencing mesothelial-mesenchymal transition (MMT).