Background & Aims: Acute promyelocytic leukemia (APL) is a malignant hematopoietic disorder caused by indefinite proliferation and lack of differentiation of leukemia stem cells. Elucidation of signaling pathways involved in leukemic stem cells are current strategies in treatment of leukemias. In this content, nucleostemin (NS) plays a critical role in proliferation and self renewal of stem and cancer cells. In the present study, effects of NS gene silencing on proliferation, differentiation and apoptosis in NB4 cell line as an APL model have been studied for the first time.

Materials & Methods: NB4 cell line was cultured in the presence of 200 nM NS-siRNA and after transfection with Nucleostemin specific siRNA nucleostemin gene expression pattern was evaluated by Semi-quantitative RT-PCR. Trypan blue exclusion test and fluorescent microscopy were used to study growth inhibitory and apoptotic effects, respectively. Differentiation was studied morphologically and biologically using Wright-Giemsa staining and latex particle phagocytic activity, respectively.

Results: NS gene was highly expressed in NB4 cells. NS-siRNA transfection into NB4 cells at 200 nM inhibited nucleostemin mRNA level up to 36.1% after 48h when compared to corresponding control cells. Between 12-72 hours after transfection, the cell growth was decreased up to 35.1% and differentiation characteristics such as decrease in nuclear cytoplasm ratio and ingestion of latex particles were observed, confirmed that differentiation toward monocytic/macrophagic Linage.

Conclusion: According to differentiating and growth inhibitory effects of NS inhibition in NB4 cells, it can be proposed as a new target for treatment of APL patients.

SOURCE: URMIA MED J 2013: 24(2): 132 ISSN: 1027-3727