Summary Increases in protein levels of XIAP in cancer cells have been associated with resistance to apoptosis induced by cellular stress. Herein we demonstrate that the upregulation of XIAP protein levels is regulated by MDM2 at the translational level. MDM2 was found to physically interact with the IRES of the XIAP 5′-UTR, and to positively regulate XIAP IRES activity. This XIAP IRES-dependent translation was significantly increased in MDM2-transfected cells where MDM2 accumulated in the cytoplasm. Cellular stress and DNA damage triggered by irradiation induced the dephosphorylation and cytoplasmic localization of MDM2, which also led to an increase in IRES-dependent XIAP translation. Upregulation of XIAP in MDM2-overexpressing cancer cells in response to irradiation resulted in resistance of these cells to radiation-induced apoptosis. Significance Overexpression of the MDM2 oncoprotein, which is often found in cancer cells, is associated with resistance to chemo-radiation therapy and poor prognosis of cancer patients. MDM2 is well characterized as an inhibitor of the tumor suppressor p53, and overexpression of MDM2 contributes to a growth advantage for cancer cells. However, the mechanism by which overexpression of MDM2 confers resistance to DNA damage induced by irradiation and chemotherapy are not fully elucidated. We report here that MDM2 was able to bind to XIAP mRNA and positively regulate the IRES-dependent XIAP translation during cellular stress triggered by irradiation. These results identify a p53-independent function for MDM2 in mediating XIAP translation, which is critical in effecting cancer cell response to chemo-radiation therapy.

Recently, a series of studies explored the correlation between the neutrophil to lymphocyte ratio and the prognosis of lung cancer. However, the current opinion regarding the prognostic role of the neutrophil to lymphocyte ratio in lung cancer is inconsistent.We performed a meta-analysis of published articles to investigate the prognostic value of the neutrophil to lymphocyte ratio in lung cancer. The hazard ratio (HR) and its 95% confidence interval (CI) were calculated.An elevated neutrophil to lymphocyte ratio predicted worse overall survival, with a pooled HR of 1.243 (95%CI: 1.106−1.397; Pheterogeneity=0.001) from multivariate studies and 1.867 (95%CI: 1.487−2.344; Pheterogeneity=0.047) from univariate studies. Subgroup analysis showed that a high neutrophil to lymphocyte ratio yielded worse overall survival in non-small cell lung cancer (NSCLC) (HR=1.192, 95%CI: 1.061−1.399; Pheterogeneity=0.003) as well as small cell lung cancer (SCLC) (HR=1.550, 95% CI: 1.156−2.077; Pheterogeneity=0.625) in multivariate studies.The synthesized evidence from this meta-analysis of published articles demonstrated that an elevated neutrophil to lymphocyte ratio was a predictor of poor overall survival in patients with lung cancer.

Berberine, a natural product derived from a plant used in Chinese herbal medicine, is reported to exhibit anticancer effects; however, its mechanism of action is not clearly defined. Herein, we demonstrate that berberine induces apoptosis in acute lymphoblastic leukemia (ALL) cells by downregulating the MDM2 oncoprotein. The proapoptotic effects of berberine were closely associated with both the MDM2 expression levels and p53 status of a set of ALL cell lines. The most potent apoptosis was induced by berberine in ALL cells with both MDM2 overexpression and a wild-type (wt)-p53, whereas no proapoptotic effect was detected in ALL cells that were negative for MDM2 and wt-p53. In contrast to the conventional chemotherapeutic drug doxorubicin, which induces p53 activation and a subsequent upregulation of MDM2, berberine strongly induced persistent downregulation of MDM2 followed by a steady-state activation of p53. We discovered that downregulation of MDM2 in ALL cells by berberine occurred at a posttranslational level through modulation of death domain-associated protein (DAXX), which disrupted the MDM2-DAXX-HAUSP interactions and thereby promoted MDM2 self-ubiquitination and degradation. Given that MDM2-overexpressing cancer cells are commonly chemoresistant, our findings suggest that this naturally derived agent may have a highly useful role in the treatment of cancer patients with refractory disease. Cancer Res; 70(23); 9895-904. Ó2010 AACR.

In pediatric acute lymphoblastic leukemia (ALL), overexpression of murine double minute 2 (MDM2) protein by leukemic cells is typically associated with a wild-type (wt)-p53 phenotype and chemoresistance. A recently developed small-molecule antagonist of MDM2, nutlin-3, inhibits the MDM2-p53 interaction, resulting in induction of p53 activity and apoptosis. In this study, we evaluated the cytotoxic effect of nutlin-3 on ALL cells with different p53 status and MDM2 expression, using 18 cell lines and 30 primary leukemia samples. We found that both ALL cell lines and primary ALL samples with wt-p53 are sensitive to nutlin-3. No cytotoxic effect of nutlin-3 was detected in ALL cells with either p53-mutant or -null phenotype. In wt-p53 ALL cells, there was a significant positive correlation between MDM2 expression levels and sensitivity to nutlin-3. Nutlin-3-induced cell death was mediated by p53-induced activation of proapoptotic proteins and by p53-induced repression of the anti-apoptotic protein survivin. As p53 function is inhibited by MDM2 in chemoresistant, MDM2-overexpressing ALL cells, potent killing of these cells by nutlin-3 suggests that this agent may be a novel therapeutic for refractory ALL.

Ratio of monocytes to lymphocytes <9% or >25% is predictive of active tuberculosis.

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The Kruppel-like factor 5 (KLF5) is a transcription factor that regulates cellular signaling involved in cell proliferation and oncogenesis. Here, we report that KLF5 interacts with tumor suppressor p53 in regulating the expression of the inhibitor-of-apoptosis protein survivin, which may play a role in pathological process of cancer. The core promoter region of survivin contains multiple GTboxes that have been characterized as KLF5 response elements. Deletion and mutation analyses as well as chromatin immunoprecipitation and electronic mobility shift assay indicated that KLF5 binds to the core survivin promoter and strongly induces its activity. Furthermore, we demonstrated that KLF5 protein is able to bind to p53 and abrogate the p53-regulated repression of survivin. Transfection of KLF5 into a KLF5-negative acute lymphoblastic leukemia cell line EU-8 enhanced survivin expression, and conversely, silencing of KLF5 by small interfering RNA in a KLF5-overexpressing acute lymphoblastic leukemia cell line EU-4 down-regulated survivin expression. The KLF5 small interfering RNA-mediated downregulation of survivin sensitized EU-4 cells to apoptosis induced by chemotherapeutic drug doxorubicin. These findings identify a novel regulatory pathway for the expression of survivin under the control of KLF5 and p53. Deregulation of this pathway may result in overexpression of survivin in cancer, thus contributing to drug resistance.Survivin is a unique member of the inhibitor-of-apoptosis protein family. It plays an important role not only in inhibiting apoptosis but also in regulating mitosis (1, 2). Moreover, it is highly expressed in almost all types of human cancer but undetected in most adult tissues (3). High levels of survivin expression have been associated with cancer progression, drug resistance, poor prognosis, and short patient survival (4, 5). On the other hand, inhibition of survivin expression or interference with survivin function has been demonstrated to reduce cancer cell growth, induce cancer cell death, and sensitize cancer cells to radiation or chemotherapy (6, 7). Therefore, survivin is regarded as a promising target for cancer treatment, and modulating the expression of survivin seems to be one important approach.Much effort has been made to explore the mechanisms by which survivin expression is regulated. It is well established that survivin expression is repressed by wild-type p53 (8 -10), while how survivin expression is activated remains less clear. Recent studies in colon cancer cells suggest that regulation of survivin expression is at least partially T-cell factor (TCF)/␤-catenin-dependent (11-13). Furthermore, a previous study to analyze the basal transcriptional requirement of survivin gene expression has indicated that the survivin gene promoter contains GC-rich sequences, and the Sp1 transcription factor induces survivin expression in HeLa cells (14). In addition to GC-rich sequences, the core promoter of survivin contains multiple CACCC or GGGTG motifs (also called GT-boxes) for Sp1-like pr...

Arterial calcification is a key pathologic component of vascular diseases such as atherosclerosis, coronary artery disease, and peripheral vascular disease. A hallmark of this pathological process is the phenotypic transition of vascular smooth muscle cells (VSMCs) to osteoblast-like cells. Several studies have demonstrated that microRNAs (miRNAs) regulate osteoblast differentiation, but it is unclear whether miRNAs also regulate VSMC-mediated arterial calcification. In the present study, we sought to characterize the role of miR-133a in regulating VSMC-mediated arterial calcification. Northern blotting analysis of VSMCs treated with β-glycerophosphate demonstrated that miR-133a was significantly decreased during osteogenic differentiation. Overexpression of miR-133a inhibited VSMC transdifferentiation into osteoblast-like cells as evidenced by a decrease in alkaline phosphatase activity, osteocalcin secretion, Runx2 expression, and mineralized nodule formation. Conversely, the knockdown of miR-133a using an miR-133a inhibitor promoted osteogenic differentiation of VSMCs by increasing alkaline phosphatase activity, osteocalcin secretion, and Runx2 expression. Runx2 was identified as a direct target of miR-133a by a cotransfection experiment in VSMCs with luciferase reporter plasmids containing wild-type or mutant 3'-untranslated region sequences of Runx2. Furthermore, the pro-osteogenic effects of miR-133a inhibitor were abrogated in Runx2-knockdown cells, and the inhibition of osteogenic differentiation by pre-miR-133a was reversed by overexpression of Runx2, providing functional evidence that the effects of miR-133a in osteogenic differentiation were mediated by targeting Runx2. These results demonstrate that miR-133a is a key negative regulator of the osteogenic differentiation of VSMCs.