CD44s and CD44v6 Expression in Head and Neck Epithelia

Background: CD44 splice variants are long-known as being associated
with cell transformation. Recently, the standard form of CD44
(CD44s) was shown to be part of the signature of cancer stem cells
(CSCs) in colon, breast, and in head and neck squamous cell
carcinomas (HNSCC). This is somewhat in contradiction to previous
reports on the expression of CD44s in HNSCC. The aim of the present
study was to clarify the actual pattern of CD44 expression in head
and neck epithelia. Methods: Expression of CD44s and CD44v6 was
analysed by immunohistochemistry with specific antibodies in
primary head and neck tissues. Scoring of all specimens followed a
two-parameters system, which implemented percentages of positive
cells and staining intensities from − to +++ (score = %×intensity;
resulting max. score 300). In addition, cell surface expression of
CD44s and CD44v6 was assessed in lymphocytes and HNSCC. Results: In
normal epithelia CD44s and CD44v6 were expressed in 60–95% and
50–80% of cells and yielded mean scores with a standard error of a
mean (SEM) of 249.5±14.5 and 198±11.13, respectively. In oral
leukoplakia and in moderately differentiated carcinomas CD44s and
CD44v6 levels were slightly increased (278.9±7.16 and 242±11.7;
291.8±5.88 and 287.3±6.88). Carcinomas in situ displayed unchanged
levels of both proteins whereas poorly differentiated carcinomas
consistently expressed diminished CD44s and CD44v6 levels.
Lymphocytes and HNSCC lines strongly expressed CD44s but not
CD44v6. Conclusion: CD44s and CD44v6 expression does not
distinguish normal from benign or malignant epithelia of the head
and neck. CD44s and CD44v6 were abundantly present in the great
majority of cells in head and neck tissues, including carcinomas.
Hence, the value of CD44s as a marker for the definition of a small
subset of cells (i.e. less than 10%) representing head and neck
cancer stem cells may need revision.