Abstract:

Objective To investigate the effect of Notch3 on proliferation and the cell cycle in human small cell lung cancer H446 cells and its possible mechanism. Methods H446 cells were stably transfected with human Notch3 and HES1 expressing plasmid separately. Short hairpin RNA (shRNA) was used to knock down MDM2 in H446 cells. The cell cycle was studied by flow cytometry. The mRNA expression levels of Notch3 and MDM2 were measured by RT-PCR. Western blotting was performed to determine the protein expression levels of Notch3, hairy and enhancer of split 1(HES1), murine double minute 2(MDM2), Rb and P21. Results Notch3 suppressed proliferation and induced cell cycle G0/G1 arrest in H446 cells(P<0.05), and up-regulated HES1 and down-regulated MDM2 at protein levels(P<0.05). High expression of HES1 resulted in a lower protein level of MDM2(P<0.05) without affecting the mRNA expression of MDM2. MDM2 knockdown suppressed proliferation and up-regulated Rb and P21 at protein levels(P<0.05).  Conclusion Notch3 may suppress proliferation and induce cell cycle arrest by up-regulating HES1, Rb and P21, and down-regulating MDM2.

Key words: Notch3, small cell lung cancer, H446 cell, Murine Double Minute 2, cell cycle, Flow cytometry, Human