Reduced expression of CD44 v3 and v6 is related to invasion in lung adenocarcinoma

We have previously reported that the histological pattern of invasion is correlated with the prognosis of surgically treated patients of lung adenocarcinoma. On the other hand, several clinicopathologic studies have shown that CD44 variant isoforms are associated with invasion and metastasis in human malignant tumors. The expression of CD44 variant isoforms v3 and v6 was analyzed in 93 Japanese lung adenocarcinoma patients by immunostaining to study the relationship between their expression and the invasion in lung adenocarcinoma. The specimens were histologically categorized into three groups. Both the invasive lesion and the noninvasive lesion were observed in 49 out of 93 cases (group I). Twenty cases were noninvasive carcinoma growing mainly in a lepidic pattern (group II). Twenty-three cases were invasive carcinoma which showed no frankly noninvasive lesion growing in a lepidic pattern (group III). The significant reduced expression of CD44 v3 and v6 was observed in the invasive lesion compared with the noninvasive lesion in adenocarcinoma of group I (P < 0.05). Although reduced expression of CD44 v3 and v6 was observed in the invasive carcinoma of group III compared with the noninvasive carcinoma of group II, it was not significant (P = 0.0693 for v3, P = 0.0827 for v6). The pattern of expression of CD44 v3 was significantly concordant with that of CD44 v6 (P < 0.0001). Our results suggest that reduced expression of CD44 v3 and v6 is associated with the invasion in the lung adenocarcinoma.