Differential expression of DUSP6 with expression of ERK and Ki-67 in non-small cell lung carcinoma.

Dual specificity phosphatase 6 (DUSP6) is a member of the MAP kinase phophatase family. DUSP6 inactivates extracellular signal-regulated kinase (ERK), belonging to the MAP kinase family, and can act in tumor suppressive pathways. The aim of this study was to investigate associations of DUSP6 expression with expression of ERK and Ki-67 and with clinicopathological parameters in lung adenocarcinoma and squamous cell carcinoma. A total of 102 squamous cell carcinomas and 66 adenocarcinomas were studied using immunohistochemistry for DUSP6, ERK1/2, and Ki-67. In 66 adenocarcinomas, high DUSP6 expression was positively correlated with ERK1/2 expression. High DUSP6 expression was correlated with lower histological grade and lower Ki-67 index in the adenocarcinomas. In 102 squamous cell carcinomas, high DUSP6 expression was correlated with lower ERK expression, with greater smoking pack-years, but not with the Ki-67 index. These results indicate that DUSP6 acts as a negative feedback regulator of ERK in adenocarcinoma progression, but that DUSP6 does not play a role in the downregulation of ERK in squamous cell carcinoma. The differential expression of DUSP6 correlated with Ki-67 index, suggesting that DUSP6 plays an important role in cancer resistance in different subtypes of non-small cell lung carcinoma.