A selective cyclin-dependent kinase 4, 6 dual inhibitor, Ribociclib (LEE011) inhibits cell proliferation and induces apoptosis in aggressive thyroid cancer

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The RB-E2F1 pathway is an important mechanism of cell-cycle control, and deregulation of this pathway is one of the key factors contributing to tumorigenesis. Cyclin-dependent kinases (CDKs) and Cyclin D have been known to increase in aggressive thyroid cancer. However, there has been no study to investigate effects of a selective CDK 4/6 inhibitor, Ribociclib (LEE011), in thyroid cancer. Performing Western blotting, we found that RB phosphorylation and the expression of Cyclin D are significantly higher in papillary thyroid cancer (PTC) cell lines as well as anaplastic thyroid cancer (ATC) cell lines, compared with normal thyroid cell line and follicular thyroid cancer cell line. LEE011 dose-dependently inhibited RB phosphorylation and also decreased the expressions of its target genes such as <I>FOXM1, Cyclin A1,</I> and <I>Myc</I> in ATC. Furthermore, LEE011 induced cell cycle arrest in G0-G1 phase and cell apoptosis, and inhibited cell proliferation in ATC. Consistently, oral administration of LEE011 to ATC xenograft models strongly inhibited tumor growth with decreased expressions of pRB, pAKT and Ki-67, and also significantly increased tumor cell apoptosis. Taken together, our data support the rationale for clinical development of the CDK4/6 inhibitor as a therapy for patients with aggressive thyroid cancer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> pRB and Cyclin D were expressed high in aggressive thyroid cancer. </LI> <LI> LEE011 suppressed pRB and also decreased the expressions of its target genes in ATC. </LI> <LI> LEE011 induced cell cycle G1 arrest and apoptosis, and inhibited cell proliferation. </LI> <LI> LEE011 inhibited in vivo tumor growth with decreased expressions of pRB and Ki-67. </LI> <LI> We could explain the anticancer effects with the RB-E2F pathway. </LI> </UL> </P>