 Gene expression levels of the proteasomal subunits (PSMA1, PSMA5, PSMB4, PSMB5 and PSMD1) were investigated in 80 patients with neuroendocrine pulmonary tumors and compared to controls.The study reviled that PSMB4 mRNA was significantly associated with proliferative activity of neuroendocrine pulmonary tumors.However, a role of PSMA5 was also indicated in neuroendocrine pulmonary tumors.