CD44 and ALDH1 immunoexpression as prognostic indicators of invasion and metastasis in oral squamous cell carcinoma

Tumour metastasis has been associated with cancer stem cells, a small population with stem-like cells properties, higher rate of migration and metastatic potential compared to cells from the tumour bulk. Our aim was to evaluate the immunoexpression of the putative cancer stem cell biomarkers ALDH1 and CD44 in primary tumour and corresponding metastatic lymph nodes.

Tumour tissue specimens (n = 50) and corresponding metastatic lymph nodes (n = 25) were surgically obtained from 50 patients with oral squamous cell carcinoma and submitted to immunohistochemistry. CD44 and ALDH1 were semi-quantitatively scored according to the proportion and intensity of positive cells within the invasive front and metastatic lymph nodes as a whole. A combined score was obtained by multiplying both parameters and later dichotomized into a final score classified as low (≤2) or high (>2) immunoexpression.

ALDH1 immunoexpression and CD44 immunoexpression were detected in both tumour sites, although the means of ALDH1 (P = .0985) and CD44 (P = .4220) cells were higher in metastasis compared to primary tumours. ALDH1^high was positively associated (P = .0184) with angiolymphatic invasion, while CD44^high was positively associated (P = .0181) with metastasis (N+). At multivariate analysis, CD44 significantly increased the odds of lymph node metastasis, regardless of T stage (OR = 8.24; 1.64-65.64, P = .0088).

CD44 immunoexpression was a significant predictor of lymph node metastasis, while ALDH1^high immunostaining was associated with angiolymphatic invasion. Altogether, it suggests that immunoexpression of CD44 and ALDH1 links the cancer stem cell phenotype with oral squamous cell carcinoma invasion and metastasis.