FKBP3 Promotes Proliferation of Non-Small Cell Lung Cancer Cells through Regulating Sp1/HDAC2/p27

FKBP3 is a member of FK506-binding proteins (FKBPs). Little is known about the expression and functional role(s) of FKBP3 in non-small cell lung cancer (NSCLC). In the present study, we demonstrated up-regulation of FKBP3 expression, both at mRNA and protein levels, in NSCLC samples which closely correlated with poor survival in NSCLC patients. <i>In vitro</i> and <i>in vivo</i> experiments revealed that FKBP3 could promote NSCLC cell proliferation. Furthermore, knockdown of FKBP3 significantly decreased histone deacetylase 2 (HDAC2) expression and increased p27 (a cell cycle inhibitor) expression. HDAC2 modulated the acetylation of histone H3K4 by directly binding to the p27 promoter. The proliferation-promoting effect of FKBP3 was dependent on HDAC2 and inhibited by p27. Also, FKBP3 induced HDAC2 promoter activity via inhibiting the ubiquitination of transcription factor Sp1. Additionally, we identified miR-145-5p as a regulator of FKBP3. miR-145-5p overexpression suppressed cell proliferation of NSCLC cells which was abrogated by FKBP3 overexpression. Taken together, our data clearly show that FKBP3/Sp1/HDAC2/p27 control cell proliferation during NSCLC development.