CD44 and its v6 spliced variant in lung carcinomas: relation to NCAM, CEA, EMA and UP1 and prognostic significance

CD44 is a polymorphic family of cell surface glycoproteins that was recently reported to have important role in cell adhesion and migration as well as modulation of cell-matrix interactions. Thus, expression of CD44 has been proposed to be associated with malignant behavior of tumors like invasive growth and formation of metastasis. The expression of CD44s and its v6 isoform (CD44v6) was determined immunohistochemically in 106 lung tumors of various histophenotypes, degrees of differentiation, and clinical stages. The results were compared with the expression of NCAM, CEA, EMA and UP1 and with clinicopathological parameters including patients' survival. CD44s was expressed in all histophenotypes of non-small cell lung carcinomas (NSCLC) with tendency being squamous cell lung carcinoma (SqCC) > bronchioloalveolar adenocarcinoma (BAC) > conventional adenocarcinoma (ConAC) (91, 66.7 and 38.9%, respectively). Almost identical distribution of positivity revealed CD44v6 in all three subgroups of NSCLC mentioned above (91, 66.7 and 36.1%, respectively). In the subgroup of neuroendocrine tumors, CD44s and CD44v6 were restrictedly expressed in small cell lung carcinomas (2/14 tumors), while all 3 typical carcinoids were strongly positive for these markers. Expression of NCAM and CEA was significantly higher in adenocarcinoma subgroup than those in SqCC subgroup (45.7 and 75% vs. 14.8 and 39%, respectively). NCAM expression was also significantly different in BACs and in ConACs (69.2 vs. 36.4%, p < 0.05). The expression of CD44 was related to the differentiation of SqCC. The carcinomas with keratinization were CD44 positive. Adenocarcinomas producing mucin were CD44 negative. The expression of CD44, NCAM, CEA, EMA and UP1 did not correlate with lymph node metastasis and disease stage. CD44V6 was the only marker that its expression was closely related to patients' survival. The absence CD44v6 but not CD44s in NSCLC group was associated with significantly longer survival of patients compared to patients with CD44v6 positive tumors. This difference was even higher in tumors negative for CD44v6 and simultaneously NCAM and/or CEA positive. The data of this study suggest that CD44v6 might be an independent prognostic factor in NSCLC. Moreover, our data give another evidence of diverse role of CD44 in the differentiation and progression of non-small cell lung carcinomas and neuroendocrine carcinomas of the lung.