Basu Alakananda, Xuan Zhenyu
Department of Microbiology, Immunology and Genetics, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
Department of Biological Sciences, Center for Systems Biology, University of Texas at Dallas, Richardson, TX 75080, USA.
Cancers (Basel). 2024 Nov 10;16(22):3783. doi: 10.3390/cancers16223783.
: The ribosomal S6 kinase 2 (S6K2) acts downstream of the mechanistic target of rapamycin complex 1 and is a homolog of S6K1 but little is known about its downstream effectors. The objective of this study was to use an unbiased transcriptome profiling to uncover how S6K2 promotes breast cancer cell survival. : RNA-Seq analysis was performed to identify novel S6K2 targets. Cells were transfected with siRNAs or plasmids containing genes of interest. Western blot analyses were performed to quantify total and phosphorylated proteins. Apoptosis was monitored by treating cells with different concentrations of doxorubicin. : Silencing of S6K2, but not S6K1, decreased p21 in MCF-7 and T47D breast cancer cells. Knockdown of Akt1 but not Akt2 decreased p21 in MCF-7 cells whereas both Akt1 and Akt2 knockdown attenuated p21 in T47D cells. While Akt1 overexpression enhanced p21 and partially reversed the effect of S6K2 deficiency on p21 downregulation in MCF-7 cells, it had little effect in T47D cells. S6K2 knockdown increased mRNA and knockdown of cJun enhanced p21. Low concentrations of doxorubicin increased, and high concentrations decreased p21 levels in T47D cells. Silencing of S6K2 or p21 sensitized T47D cells to doxorubicin via c-Jun N-terminal kinase (JNK)-mediated downregulation of Mcl-1. : S6K2 knockdown enhanced doxorubicin-induced apoptosis by downregulating the cell cycle inhibitor p21 and the anti-apoptotic protein Mcl-1 via Akt and/or JNK.
核糖体S6激酶2（S6K2）作用于雷帕霉素机制靶点复合物1的下游，是S6K1的同源物，但其下游效应分子鲜为人知。本研究的目的是通过无偏差转录组分析来揭示S6K2如何促进乳腺癌细胞存活。：进行RNA测序分析以鉴定新的S6K2靶点。用小干扰RNA（siRNA）或含有感兴趣基因的质粒转染细胞。进行蛋白质免疫印迹分析以定量总蛋白和磷酸化蛋白。通过用不同浓度的阿霉素处理细胞来监测细胞凋亡。：在MCF-7和T47D乳腺癌细胞中，沉默S6K2而非S6K1会降低p21水平。在MCF-7细胞中，敲低Akt1而非Akt2会降低p21水平，而在T47D细胞中，同时敲低Akt1和Akt2会减弱p21水平。虽然Akt1过表达增强了p21，并部分逆转了S6K2缺陷对MCF-7细胞中p21下调的影响，但对T47D细胞几乎没有影响。敲低S6K2会增加mRNA，而敲低c-Jun会增强p21。低浓度的阿霉素会增加T47D细胞中的p21水平，高浓度则会降低p21水平。沉默S6K2或p21会通过c-Jun氨基末端激酶（JNK）介导的Mcl-1下调使T47D细胞对阿霉素敏感。：敲低S6K2通过Akt和/或JNK下调细胞周期抑制剂p21和抗凋亡蛋白Mcl-1，增强了阿霉素诱导的细胞凋亡。
