Background: WEE1 is a G2/M checkpoint regulator protein. Various studies have indicated that WEE1could be a good target for cancer therapy. The main aim of this study was to asssess the tumor suppressivepotential of WEE1 silencing in two different breast cancer cell lines, MCF7 which carries the wild-type p53 andMDA-MB468 which contains a mutant type. Materials and Methods: After WEE1 knockdown with specificshRNAs downstream effects on cell viability and cell cycle progression were determined using MTT and flowcytometry analyses, respectively. Real-time PCR and Western blotting were conducted to assess the effect ofWEE1 inhibition on the expression of apoptotic (p53) and anti-apoptotic (Bcl2) factors and also a growth marker(VEGF). Results: The results showed that WEE1 inhibition could cause a significant decrease in the viability ofboth MCF7 and MDA-MB-468 breast cancer cell lines by more than 50%. Interestingly, DNA content assaysshowed a significant increase in apoptotic cells following WEE1 silencing. WEE1 inhibition also induced upregulationof the apoptotic marker, p53, in breast cancer cells. A significant decrease in the expression of VEGFand Bcl-2 was observed following WEE1 inhibition in both cell lines. Conclusions: In concordance with previousstudies, our data showed that WEE1 inhibition could induce G2 arrest abrogation and consequent cell deathin breast cancer cells. Moreover, in this study, the observed interactions between the pro- and anti-apoptoticproteins and decrease in the angiogenesis marker expression confirm the susceptibility to apoptosis and validatethe tumor suppressive effect of WEE1 inhibition in breast cancer cells. Interestingly, the levels of the sensitivityto WEE1 silencing in breast cancer cells, MCF7 and MDA-MB468, seem to be in concordance with the level ofp53 expression.
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