Frequent down-regulation of pim-1 mRNA expression in non-small cell lung cancer is associated with lymph node metastases

Abstract

Pim kinases are emerging as important mediators of cytokine signalling pathways in hematopoietic cells, and contribute to the progression of certain leukemias and solid tumors. The mRNA expression of pim-1, a putative oncogenic serine-threonine kinase, was determined in non-small cell lung cancer (NSCLC) patients. Sixty-eight patients with potentially curative resections (R0 resections) for NSCLC in histopathological stages I-IIIA were included. An analysis of pim-1 mRNA expression was performed on paired tumor and normal lung tissue samples by quantitative real-time reverse transcriptase-PCR (RT-PCR) standardized for β-actin. Pim-1 expression in the tumor (median 0.28) was significantly down-regulated (p<0.0001) compared to the paired normal tissue (median 4.96). Immunohistochemistry showed a strong expression of Pim-1 protein in the normal respiratory epithelium and a lower expression in the tumor cells. A significant association between the pim-1 down-regulation and occurrence of lymph node metastases (p=0.05) was detected. The down-regulation of pim-1 mRNA was demonstrated for 59 out of 68 lung cancer patients (86.8%). Down-regulation occurs already in the early stage of NSCLC and is either directly involved in the lymphatic progression in NSCLC or represents a surrogate marker.