Cdk2 suppresses cellular senescence induced by the c-myc oncogene

Chen

Molecular Cancer Research

et al. 2015

miRNA expression profiles are widely investigated in the major cancers, but their specific roles and functions in cancers have not yet to be fully elucidated. In this study, miRNA expression profiles were determined in clear cell renal cell carcinomas (ccRCC) and in matched normal kidney tissues by using a miRNA microarray platform which covers a total of 851 human miRNAs. Differential expression of 74 miRNAs were identified between ccRCC specimens and their matched adjacent noncancerous tissues, of which 30 were significantly upregulated in ccRCCs, and the other 44 were downregulated (fold change ! 2, P < 0.05). Interestingly, miR-200c was commonly downregulated in ccRCC specimens and ccRCC cell lines with significant functional consequences. Growth curve and FACS assay indicated that overexpression of miR-200c suppressed cell growth and induced cell-cycle arrest at G 0 -G 1 phases in SN12-PM6 and 786-O cells. Furthermore, miR-200c could suppress in vivo tumor growth of SN12-PM6 cells in mice. Bioinformatics exposed cyclin-dependent kinase 2 (CDK2) as a potential target of miR-200c, which was validated using a luciferase reporter assay. Mechanistic investigations revealed that miR-200c was directly responsible for suppressing the expression of CDK2 in ccRCC cell lines and xenografts. Taken together, miR-200c plays an antioncogenic role in ccRCC, through controlling cell growth and cell-cycle progression by downregulating the G 1 -S regulator CDK2.Implications: miR-200c exerts its novel antioncogenic function in renal cell carcinoma by controlling CDK2-dependent cell growth and cell-cycle progression.

Section: Discussionmentioning

confidence: 95%

miR-200c Targets CDK2 and Suppresses Tumorigenesis in Renal Cell Carcinoma

Chen

Molecular Cancer Research

et al. 2015

“…Along these lines, Lin et al (2010) reported that a Skp2-SCF inhibitor triggers senescence and inhibition of tumor growth of PTEN-deficient cancer cells. In further support of this emerging theme, Amati and colleagues (Campaner et al 2010) observed that oncogenic stress caused by the Myc oncoprotein sensitizes Cdk2-deficient cells to undergo senescence in vitro and in vivo. Similarly, in advanced non-small-cell lung carcinoma driven by activation of oncogenic KRas, tumor progression is halted and senescence is induced upon genetic ablation of Cdk4 (Puyol et al 2010).…”

Section: Restoration Of Cellular Senescence In Vivomentioning

confidence: 88%

The essence of senescence: Figure 1.

Kuilman¹,

Michaloglou²,

Mooi³

et al. 2010

Genes Dev.

1,806

1,771

Almost half a century after the first reports describing the limited replicative potential of primary cells in culture, there is now overwhelming evidence for the existence of “cellular senescence” in vivo. It is being recognized as a critical feature of mammalian cells to suppress tumorigenesis, acting alongside cell death programs. Here, we review the various features of cellular senescence and discuss their contribution to tumor suppression. Additionally, we highlight the power and limitations of the biomarkers currently used to identify senescent cells in vitro and in vivo.

“…12). Synthetic lethal interactions allow the elimination of tumour cells carrying genetic lesions that cannot be targeted using small molecules [23][24][25][26][27][28] . We show that elevated energy consumption and addiction to mitochondrial glutaminolysis in cells expressing deregulated MYC establish a dependence on the kinase ARK5, which limits mTORC1 activity and maintains a high respiratory capacity.…”

Section: Research Lettermentioning

confidence: 99%

Deregulated MYC expression induces dependence upon AMPK-related kinase 5

Liu

Ulbrich

Müller

et al. 2012

Nature

236

248

Deregulated expression of the MYC oncoprotein contributes to the genesis of many human tumours, yet strategies to exploit this for a rational tumour therapy are scarce. MYC promotes cell growth and proliferation, and alters cellular metabolism to enhance the provision of precursors for phospholipids and cellular macromolecules 1,2 . Here we show in human and murine cell lines that oncogenic levels of MYC establish a dependence on AMPK-related kinase 5 (ARK5; also known as NUAK1) for maintaining metabolic homeostasis and for cell survival. ARK5 is an upstream regulator of AMPK and limits protein synthesis via inhibition of the mammalian target of rapamycin 1 (mTORC1) signalling pathway. ARK5 also maintains expression of mitochondrial respiratory chain complexes and respiratory capacity, which is required for efficient glutamine metabolism. Inhibition of ARK5 leads to a collapse of cellular ATP levels in cells expressing deregulated MYC, inducing multiple pro-apoptotic responses as a secondary consequence. Depletion of ARK5 prolongs survival in MYC-driven mouse models of hepatocellular carcinoma, demonstrating that targeting cellular energy homeostasis is a valid therapeutic strategy to eliminate tumour cells that express deregulated MYC.To identify kinases that are specifically required for the viability of cells expressing deregulated MYC, we used U2OS cells expressing c-MYC fused to the oestrogen receptor ligand binding domain (MYC-ER) (Fig. 1a). Activation of MYC-ER by 4-hydroxytamoxifen (OHT) had little effect on apoptosis when cells were grown at low density in the presence of growth factors. Under these conditions, we performed a short interfering (si)RNA screen of the human kinome, using automated microscopy to identify siRNAs that induced poly-ADP-ribose-polymerase cleavage specifically in the presence of OHT. This screen yielded two hits, ARK5 and AMPK (Supplementary Table 1).Depletion of ARK5 induced the accumulation of MYC-expressing cells that stained positive for annexin V and propidium iodide (Fig. 1a and Supplementary Fig. 1a). Similarly, expressing different short hairpin (sh)RNAs targeting ARK5 induced levels of MYC-dependent death that correlated with the degree of knockdown (Fig. 1b). Titration of OHT revealed that levels of MYC that cause a dependence on ARK5 are higher than those required to promote proliferation ( Supplementary Fig. 1b). Depletion of ARK5 induced death in U2OS cells constitutively expressing MYC and suppressed propagation of MRC5 fibroblasts in a MYCdependent manner (Fig. 1c and Supplementary Fig. 1c). Expression of murine ARK5, which is not targeted by the shRNAs used, prevented death upon depletion of human ARK5 (Fig. 1d). This rescue required LKB1-dependent phosphorylation of T212, but not AKT-dependent phosphorylation of S601 (refs 3, 4). Mutation of K85 within the ATPbinding domain blocked the ability of murine ARK5 to prevent death, demonstrating that rescue requires ARK5 catalytic activity. Accordingly, a small-molecule inhibitor of ARK5, BX795, mimicked the effects o...