Annexin A2 Silencing Induces G2 Arrest of Non-small Cell Lung Cancer Cells through p53-dependent and -independent Mechanisms (original) (raw)

Inhibition of JNK reduces G2/M transit independent of p53, leading to endoreduplication, decreased proliferation, and apoptosis in breast cancer cells

Oncogene, 2004

c-Jun N-terminal kinase (JNK) is activated by diverse cell stimuli, including stress, growth factors, and cytokines. Traditionally, activation of JNK by stress treatment is thought to induce cell death. However, our recent data indicate that JNK's ability to sensitize cells to apoptosis may be, in part, cell cycle dependent. Here, we show that the majority of both paclitaxel-and UV-induced apoptosis can be inhibited by the pharmacological JNK inhibitor, SP600125, in MCF-7 cells. However, inhibition of JNK does little to reverse doxorubicin-induced apoptosis in MCF-7 cells or doxorubicin-and UV-mediated death in MDA MB-231 cells. SP treatment causes G2/M arrest of three breast cancer cell lines and results in the endoreduplication (cellular DNA content 44N) of MCF-7 and MDA MB-231 cells. These effects on cell cycle and apoptosis are not significantly altered by the inhibition of p53, indicating that JNK is functioning independently of p53. Lastly, inhibition of JNK using both SP and antisense oligonucleotides targeted to JNK1 and JNK2 reduced proliferation of all three breast cancer cell lines. Taken together, these results suggest that the activation of JNK is important for the induction of apoptosis following stresses that function at different cell cycle phases, and that basal JNK activity is necessary to promote proliferation and maintain diploidy in breast cancer cells.

ROS-dependent activation of JNK converts p53 into an efficient inhibitor of oncogenes leading to robust apoptosis

Cell Death and Differentiation, 2014

Rescue of the p53 tumor suppressor is an attractive cancer therapy approach. However, pharmacologically activated p53 can induce diverse responses ranging from cell death to growth arrest and DNA repair, which limits the efficient application of p53-reactivating drugs in clinic. Elucidation of the molecular mechanisms defining the biological outcome upon p53 activation remains a grand challenge in the p53 field. Here, we report that concurrent pharmacological activation of p53 and inhibition of thioredoxin reductase followed by generation of reactive oxygen species (ROS), result in the synthetic lethality in cancer cells. ROS promote the activation of c-Jun N-terminal kinase (JNK) and DNA damage response, which establishes a positive feedback loop with p53. This converts the p53-induced growth arrest/senescence to apoptosis. We identified several survival oncogenes inhibited by p53 in JNK-dependent manner, including Mcl1, PI3K, eIF4E, as well as p53 inhibitors Wip1 and MdmX. Further, we show that Wip1 is one of the crucial executors downstream of JNK whose ablation confers the enhanced and sustained p53 transcriptional response contributing to cell death. Our study provides novel insights for manipulating p53 response in a controlled way. Further, our results may enable new pharmacological strategy to exploit abnormally high ROS level, often linked with higher aggressiveness in cancer, to selectively kill cancer cells upon pharmacological reactivation of p53.

JNK targets p53 ubiquitination and degradation in nonstressed cells

Genes & …, 1998

In this study we elucidated the role of nonactive JNK in regulating p53 stability. The amount of p53-JNK complex was inversely correlated with p53 level. A peptide corresponding to the JNK binding site on p53 efficiently blocked ubiquitination of p53. Similarly, p53 lacking the JNK binding site exhibits a longer half-life than p53 wt. Outcompeting JNK association with p53 increased the level of p53, whereas overexpression of a phosphorylation mutant form of JNK inhibited p53 accumulation. JNK-p53 and Mdm2-p53 complexes were preferentially found in G 0 /G 1 and S/G 2 M phases of the cell cycle, respectively. Altogether, these data indicate that JNK is an Mdm2-independent regulator of p53 stability in nonstressed cells.

p53R2 Inhibits the Proliferation of Human Cancer Cells in Association with Cell-Cycle Arrest

Molecular Cancer Therapeutics, 2011

Deregulation of the expression of p53R2, a p53-inducible homologue of the R2 subunit of ribonucleotide reductase, has been found in various human cancer tissues; however, the roles p53R2 plays in cancer progression and malignancy remain controversial. In present study, we examined changes in gene expression profiles associated with p53R2 in cancer cells using the analysis of cDNA microarray. Gene set enrichment analysis (GSEA) identified the gene set regulating cell cycle progression was significantly enriched in p53R2-silencing human oropharyngeal carcinoma KB cells. Attenuation of p53R2 expression significantly reduced p21 expression and moderately increased cyclin D1 expression in both wild-type p53 cancer cells: KB, MCF-7, and mutant p53 cancer cells: PC3 and MDA-MB-231. Conversely, overexpression of p53R2-GFP resulted in an increase in the expression of p21 and decrease in the expression of cyclin D1, which correlated with reduced cell population in S-phase in vitro and suppressed growth in vivo. Furthermore, the MEK inhibitor PD98059 partially abolished modulation of p21 and cyclin D1 expression by p53R2. Moreover, under the conditions of non-stress and adriamycininduced genotoxic stress, attenuation of p53R2 in KB cells significantly increased phosphorylated H2AX, which indicates attenuation of p53R2 may enhance DNA damage induced by adriamycin. Overall, our study demonstrates that p53R2 may suppress cancer cells proliferation partially by up-regulation of p21 and down-regulation of cyclin D1; p53R2 plays critical roles not only in DNA damage repair but also in proliferation of cancer cells.

Specific role of JNK in the maintenance of the tumor-initiating capacity of A549 human non-small cell lung cancer cells

Oncology reports, 2013

Deregulation of c-Jun NH2-terminal kinase (JNK) signaling is now increasingly reported in a variety of human malignancies. Non-small cell lung cancer (NSCLC) is among such human malignancies with aberrant JNK activation; yet the exact role(s) of JNK deregulation in NSCLC biology, in particular in vivo, remains unclear. Here, we demonstrated a specific role of JNK in the control of the tumor-initiating capacity of A549 cells derived from human lung adenocarcinoma, a major subtype of NSCLC. Despite its potent inhibitory activity on A549 cell growth in vitro, SP600125, a reversible JNK inhibitor, failed to inhibit the growth of pre-established A549 xenografts in vivo when systemically administered. Nevertheless, the same SP600125 treatment caused a marked reduction in the tumor-initiating population within the A549 tumors, suggesting that JNK may be specifically required in vivo for the maintenance of the tumor-initiating population of tumor cells rather than for proliferation and surv...

MEKK1/JNK signaling stabilizes and activates p53

Proceedings of the National Academy of Sciences, 1998

Activation of the tumor suppressor p53 by stress and damage stimuli often correlates with induction of stress kinases, Jun-NH 2 kinase (JNK). As JNK association with p53 plays an important role in p53 stability, in the present study we have elucidated the relationship between the JNK-signaling pathway and p53 stability and activity. Expression of a constitutively active form of JNKK upstream kinase, mitogen-activated protein kinase kinase kinase (⌬MEKK1), increased the level of the exogenously transfected form of p53 in p53 null (10.1) cells as well as of endogenous p53 in MCF7 breast cancer cells. Increased p53 level by forced expression of ⌬MEKK1 coincided with a decrease in p53 ubiquitination in vivo and with prolonged p53 half-life. Computerized modeling of the JNK-binding site (amino acids 97-116; p7 region) enabled us to design mutations of exposed residues within this region. Respective mutations (p53 101-5-8) and deletion (p53 ⌬p7) forms of p53 did not exhibit the same increase in p53 levels upon ⌬MEKK1 expression. In vitro phosphorylation of p53 by JNK abolished Mdm2 binding and targeting of p53 ubiquitination. Similarly, ⌬MEKK1 expression increased p53 phosphorylation by immunopurified JNK and dissociated p53-Mdm2 complexes. Transcriptional activity of p53, as measured via mdm2 promoter-driven luciferase, exhibited a substantial increase in ⌬MEKK1-expressing cells. Cotransfection of p53 and ⌬MEKK1 into p53 null cells potentiated p53-dependent apoptosis, suggesting that MEKK1 effectors contribute to the ability of p53 to mediate programmed cell death. Our results point to the role of MEKK1-JNK signaling in p53 stability, transcriptional activities, and apoptotic capacity as part of the cellular response to stress.

Regulation of p53 tumour suppressor target gene expression by the p52 NF-κB subunit

The EMBO Journal, 2006

The p52/p100 nuclear factor kappa B (NF-jB) subunit (NF-jB2) is aberrantly expressed in many tumour types and has been implicated as a regulator of cell proliferation. Here, we demonstrate that endogenous p52 is a direct regulator of Cyclin D1 expression. However, stimulation of Cyclin D1 expression alone cannot account for all the cell cycle effects of p52/p100 and we also find that p52 represses expression of the Cyclin-dependent kinase inhibitor p21 WAF/CIP1. Significantly, this latter effect is dependent upon basal levels of the tumour suppressor p53. By contrast, p52 cooperates with p53 to regulate other known p53 target genes such as PUMA, DR5, Gadd45a and Chk1. p52 associates directly with these p53-regulated promoters where it regulates coactivator and corepressor binding. Moreover, recruitment of p52 is p53 dependent and does not require p52-DNA-binding activity. These results reveal a complex role for p52 as regulator of cell proliferation and p53 transcriptional activity. Furthermore, they imply that in some cell types, p52 can regulate p53 function and influence p53-regulated decision-making following DNA damage and oncogene activation.