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.

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