Tumor budding at the invasive tumor front of colorectal cancer is recognized as an independent prognostic factor significantly related to both lymph node and distant metastasis. Several lines of evidence seem to suggest that tumor buds may, to some extent, represent malignant colorectal cancer stem cells because of their potential for migration and re-differentiation locally and at sites of metastasis.
However, phenotypic characterization of cancer stem cells in general is still debated although at least 8 putative stem cell markers have been suggested including CD166, CD44s, EpCAM, ALDH1, CD133, CD24, CD90, and ABCG5. Little is known about the potential of these proteins to act as prognostic biomarkers in patients with colorectal cancer and most of these proteins have never before been explored within tumor buds themselves.
A research article published on February 14, 2010 in the World Journal of Gastroenterology addressed this question. Considering the apparent stem cell-like properties of tumor buds and association of budding with adverse clinical outcomes, the research team led by Dr. Alessandro Lugli performed immunohistochemical staining of 8 putative cancer stem cell markers, namely CD166, CD44s, EpCAM, ALDH1, CD133, CD24, CD90, and ABCG5. The expression within tumor buds was evaluated, their frequency of occurrence and their potential prognostic significance in patients with colorectal cancer were determined.
Their findings showed that expression of EpCAM and particularly of ABCG5 within the tumor buds of colorectal cancer are frequent events. Moreover, expression of EpCAM or ABCG5 within tumor buds themselves has the potential to stratify patients with colorectal cancer into prognostic subgroups. This was particularly pronounced for patients with node-negative disease.