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Nilotpal Roy,
Prashant V Bommi,
Uppoor G Bhat,
Shaumick Bhattacharjee,
Indira Elangovan,
Jing Li,
Krushna C Patra,
Dragana Kopanja,
Adam Blunier,
Richard V Benya,
Srilata Bagchi, Pradip Raychaudhuri
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ABSTRACT: Colon cancer is one of the deadliest cancers worldwide because of its metastasis to other essential organs. Metastasis of colon cancer involves a complex set of events, including epithelial to mesenchymal transition (EMT) that increases invasiveness of the tumor cells. Here we show that the xeroderma pigmentosum group E (XPE) gene product DDB2 is down-regulated in high-grade colon cancers, and it plays a dominant role in the suppression of EMT of the colon cancer cells. Depletion of DDB2 promotes mesenchymal phenotype, whereas expression of DDB2 promotes epithelial phenotype. DDB2 constitutively represses genes that are the key activators of EMT, indicating that DDB2 is a master regulator of EMT of the colon cancer cells. Moreover, we observed evidence that DDB2 functions as a barrier for EMT induced by hypoxia and TGF-β. Also, we provide evidence that DDB2 inhibits metastasis of colon cancer. The results presented here identify a transcriptional regulatory pathway of DDB2 that is directly linked to the mechanisms that suppress metastasis of colon cancer.
Cancer Research 04/2013; · 7.86 Impact Factor
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Zebin Wang,
Yu Zheng,
Hyun Jung Park,
Jing Li,
Janai R Carr,
Yi-Ju Chen,
Megan M Kiefer,
Dragana Kopanja,
Srilata Bagchi,
Angela L Tyner, Pradip Raychaudhuri
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ABSTRACT: The forkhead box transcription factor FOXM1 is considered to be a promising target for cancer therapy. However, the significance of FOXM1 in tumors harboring mutation in p53, which is very common, is unclear. In this study, we investigated the efficacy of FoxM1-targeting in spontaneous p53-null tumors using genetic ablation as well as using a peptide-inhibitor of FOXM1. We show that conditional deletion of FoxM1 inhibits growth of the p53 null thymic lymphoma and sarcoma cells. In addition, deletion of FoxM1 induces apoptotic cell death of the p53 null tumors, accompanied by reduced expression of the FOXM1 target genes Survivin and Bmi1. An ARF-derived peptide that inhibits the activity of FOXM1, by targeting it to the nucleolus, also induces apoptosis in the p53 null sarcoma and lymphoma, leading to a strong inhibition of their metastatic colonization. Together, our observations suggest that FOXM1 is critical for survival and growth of the p53-null lymphoma and sarcoma, and provide proof-of-principle that FOXM1 is an effective therapeutic target for sarcoma and lymphoma carrying loss of function mutation in p53.
Molecular Cancer Therapeutics 02/2013; · 5.23 Impact Factor
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ABSTRACT: Phenethyl isothiocyanate (PEITC) is a promising cancer chemopreventive agent commonly found in edible cruciferous vegetables. It has been implicated also for therapy, and is in clinical trial for lung cancer. Here, we provide evidence that the tumor suppressive effect of PEITC is related to its ability to induce expression of damaged DNA binding protein 2 (DDB2), a DNA repair protein involved also in apoptosis and premature senescence. DDB2 expression is attenuated in a wide variety of cancers including the aggressive colon cancers. We show that, in colon cancer cells, reactive oxygen species, which are induced by PEITC, augment expression of DDB2 through the p38MAPK/JNK pathway, independently of p53. PEITC-induced expression of DDB2 is critical for inhibition of tumor progression by PEITC. Tumors derived from DDB2-deficient colon cancer cells are refractory to PEITC-treatments, resulting from deficiencies in apoptosis and senescence. The DDB2-proficient tumors, on the other hand, respond effectively to PEITC. The results show that PEITC can be used to induce expression of DDB2, and that expression of DDB2 is critical for effective response of tumors to PEITC.
Cancer biology & therapy 10/2012; 14(2). · 2.64 Impact Factor
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Janai R Carr,
Megan M Kiefer,
Hyun Jung Park,
Jing Li,
Zebin Wang,
Joel Fontanarosa,
Danielle DeWaal,
Dragana Kopanja,
Elizaveta V Benevolenskaya,
Grace Guzman, Pradip Raychaudhuri
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ABSTRACT: Elevated expression of FoxM1 in breast cancer correlates with an undifferentiated tumor phenotype and a negative clinical outcome. However, a role for FoxM1 in regulating mammary differentiation was not known. Here, we identify another function of FoxM1, the ability to act as a transcriptional repressor, which plays an important role in regulating the differentiation of luminal epithelial progenitors. Regeneration of mammary glands with elevated levels of FoxM1 leads to aberrant ductal morphology and expansion of the luminal progenitor pool. Conversely, knockdown of FoxM1 results in a shift toward the differentiated state. FoxM1 mediates these effects by repressing the key regulator of luminal differentiation, GATA-3. Through association with DNMT3b, FoxM1 promotes methylation of the GATA-3 promoter in an Rb-dependent manner. This study identifies FoxM1 as a critical regulator of mammary differentiation with significant implications for the development of aggressive breast cancers.
Cell reports. 06/2012; 1(6):715-29.
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ABSTRACT: Premature senescence induced by DNA damage or oncogene is a critical mechanism of tumor suppression. Reactive oxygen species (ROS) have been implicated in the induction of premature senescence response. Several pathological disorders such as cancer, aging and age related neurological abnormalities have been linked to ROS deregulation. Here, we discuss how Damaged DNA binding Protein-2 (DDB2), a nucleotide excision repair protein, plays an important role in ROS regulation by epigenetically repressing the antioxidant genes MnSOD and Catalase. We further revisit a model in which DDB2 plays an instrumental role in DNA damage induced ROS accumulation, ROS induced premature senescence and inhibition of skin tumorigenesis.
International Journal of Molecular Sciences 01/2012; 13(9):11012-26. · 2.60 Impact Factor
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ABSTRACT: Exposure to ultraviolet rays (UV) in sunlight is the main cause of skin cancer. Here, we show that the p53-induced genes DDB2 and p21 are down-regulated in skin cancer, and in the mouse model they functionally cooperate to prevent UV-induced skin cancer. Our previous studies demonstrated an antagonistic role of DDB2 and p21 in nucleotide excision repair and apoptosis. Surprisingly, we find that the loss of p21 restores nucleotide excision repair and apoptosis in Ddb2(-/-) mice, but it does not protect from UV-mediated skin carcinogenesis. In contrast, Ddb2(-/-)p21(-/-) mice are significantly more susceptible to UV-induced skin cancer than the Ddb2(-/-) or the p21(-/-) mice. We provide evidence that p21 deletion in the Ddb2(-/-) background causes a strong increase in cell proliferation. The increased proliferation in the Ddb2(-/-)p21(-/-) background is related to a severe deficiency in UV-induced premature senescence. Also, the oncogenic pro-proliferation transcription factor FOXM1 is overexpressed in the p21(-/-) background. Our results show that the anti-proliferative and the pro-senescence pathways of DDB2 and p21 are critical protection mechanisms against skin malignancies.
Journal of Biological Chemistry 12/2011; 287(5):3019-28. · 4.77 Impact Factor
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ABSTRACT: Pulmonary arterial hypertension (PAH) is a devastating disease, and no effective treatments are available. Hypoxia-induced pulmonary artery remodeling, including smooth muscle cell proliferation, contributes to PAH, but the exact mechanisms underlying this abnormal process are largely undefined. The forkhead box M1 (FoxM1) transcription factor regulates cancer cell growth by modulating gene expression critical for cell cycle progression. Here, we report for the first time, to the best of our knowledge, a novel function of FoxM1 in the hypoxia-stimulated proliferation of human pulmonary artery smooth muscle cells (HPASMCs). Exposure to hypoxia caused a marked up-regulation of FoxM1 gene expression, mainly at the transcription level, and this induction correlated with HPASMC cell proliferation. The knockdown of FoxM1 inhibited the hypoxia-stimulated proliferation of HPASMCs. We found that the knockdown of HIF-2α, but not HIF-1α, diminished FoxM1 induction in response to hypoxia. However, the knockdown of FoxM1 did not alter expression levels of HIF-2α or HIF-1α, suggesting that HIF-2α is an upstream regulator of FoxM1. Furthermore, the knockdown of FoxM1 prevented the hypoxia-induced expression of aurora A kinase and cyclin D1. Collectively, our results suggest that hypoxia induces FoxM1 gene expression in an HIF-2α-dependent pathway, thereby promoting HPASMC proliferation.
American Journal of Respiratory Cell and Molecular Biology 10/2011; 46(4):431-6. · 5.13 Impact Factor
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ABSTRACT: The FoxM1 transcription factor gene is overexpressed in cancer. Its expression is stimulated by oncogenic signaling pathways and reactive oxygen species. It is also a target of regulation by the tumor suppressor genes. The transcriptional activity of FoxM1 depends upon activation by cyclin and cyclin-dependent kinases as well as Plk1. FoxM1 stimulates expression of several genes involved in the cell cycle progression. Moreover, it supports proliferation of tumor cells by stimulating expression of the antioxidant genes and reducing oxidative stress. A new study provides evidence that FoxM1, in the absence of its inhibitor, the tumor suppressor Arf, drives metastasis of hepatocellular carcinoma (HCC). It induces an epithelial-mesenchymal-like transition phenotype in HCC cells, increases cell migration, and induces premetastatic niche at the distal organ of metastasis. FoxM1 directly activates genes involved in multiple steps of metastasis. In this review, we discuss the evidence for a master regulatory role of FoxM1 in tumor metastasis.
Cancer Research 06/2011; 71(13):4329-33. · 7.86 Impact Factor
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Pradip Raychaudhuri
Cell cycle (Georgetown, Tex.) 06/2011; 10(12):1893-4. · 5.36 Impact Factor
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ABSTRACT: Malignant neuroblastomas contain stem-like cells. These tumors also overexpress the Forkhead box transcription factor FoxM1. In this study, we investigated the roles of FoxM1 in the tumorigenicity of neuroblastoma. We showed that depletion of FoxM1 inhibits anchorage-independent growth and tumorigenicity in mouse xenografts. Moreover, knockdown of FoxM1 induces differentiation in neuroblastoma cells, suggesting that FoxM1 plays a role in the maintenance of the undifferentiated progenitor population. We showed that inhibition of FoxM1 in malignant neuroblastoma cells leads to the downregulation of the pluripotency genes sex determining region Y box 2 (Sox2) and Bmi1. We provided evidence that FoxM1 directly activates expression of Sox2 in neuroblastoma cells. By using a conditional deletion system and neurosphere cultures, we showed that FoxM1 is important for expression of Sox2 and Bmi1 in the mouse neural stem/progenitor cells and is critical for its self-renewal. Together, our observations suggested that FoxM1 plays an important role in the tumorigenicity of the aggressive neuroblastoma cells through maintenance of the undifferentiated state.
Cancer Research 06/2011; 71(12):4292-302. · 7.86 Impact Factor
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ABSTRACT: The mammalian Cul4 genes, Cul4A and Cul4B, encode the scaffold components of the cullin-based E3 ubiquitin ligases. The two Cul4 genes are functionally redundant. Recent study indicated that mice expressing a truncated CUL4A that fails to interact with its functional partner ROC1 exhibit no developmental phenotype. We generated a Cul4A-/- strain lacking exons 4-8 that does not express any detectable truncated protein. In this strain, the male mice are infertile and exhibit severe deficiencies in spermatogenesis. The primary spermatocytes are deficient in progression through late prophase I, a time point when expression of the X-linked Cul4B gene is silenced due to meiotic sex chromosome inactivation. Testes of the Cul4A-/- mice exhibit extensive apoptosis. Interestingly, the pachytene spermatocytes exhibit persistent double stranded breaks, suggesting a deficiency in homologous recombination. Also, we find that CUL4A localizes to the double stranded breaks generated in pre-pachytene spermatocytes. The observations identify a novel function of CUL4A in meiotic recombination and demonstrate an essential role of CUL4A in spermatogenesis.
Developmental Biology 02/2011; 352(2):278-87. · 4.07 Impact Factor
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Hyun Jung Park,
Galina Gusarova,
Zebin Wang,
Janai R Carr,
Jing Li,
Ki-Hyun Kim,
Jin Qiu,
Yoon-Dong Park,
Peter R Williamson,
Nissim Hay,
Angela L Tyner,
Lester F Lau,
Robert H Costa, Pradip Raychaudhuri
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ABSTRACT: The forkhead box M1b (FoxM1b) transcription factor is over-expressed in human cancers, and its expression often correlates with poor prognosis. Previously, using conditional knockout strains, we showed that FoxM1b is essential for hepatocellular carcinoma (HCC) development. However, over-expression of FoxM1b had only marginal effects on HCC progression. Here we investigated the effect of FoxM1b expression in the absence of its inhibitor Arf. We show that transgenic expression of FoxM1b in an Arf-null background drives hepatic fibrosis and metastasis of HCC. We identify novel mechanisms of FoxM1b that are involved in epithelial-mesenchymal transition, cell motility, invasion and a pre-metastatic niche formation. FoxM1b activates the Akt-Snail1 pathway and stimulates expression of Stathmin, lysyl oxidase, lysyl oxidase like-2 and several other genes involved in metastasis. Furthermore, we show that an Arf-derived peptide, which inhibits FoxM1b, impedes metastasis of the FoxM1b-expressing HCC cells. The observations indicate that FoxM1b is a potent activator of tumour metastasis and that the Arf-mediated inhibition of FoxM1b is a critical mechanism for suppression of tumour metastasis.
EMBO Molecular Medicine 01/2011; 3(1):21-34. · 10.33 Impact Factor
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ABSTRACT: Inherent and acquired therapeutic resistance in breast cancer remains a major clinical challenge. In human breast cancer samples, overexpression of the oncogenic transcription factor FoxM1 has been suggested to be a marker of poor prognosis. In this study, we report that FoxM1 overexpression confers resistance to the human epidermal growth factor receptor 2 monoclonal antibody Herceptin and microtubule-stabilizing drug paclitaxel, both as single agents and in combination. FoxM1 altered microtubule dynamics to protect tumor cells from paclitaxel-induced apoptosis. Mechanistic investigations revealed that the tubulin-destabilizing protein Stathmin, whose expression also confers resistance to paclitaxel, is a direct transcriptional target of FoxM1. Significantly, attenuating FoxM1 expression by small interfering RNA or an alternate reading frame (ARF)-derived peptide inhibitor increased therapeutic sensitivity. Our findings indicate that targeting FoxM1 could relieve therapeutic resistance in breast cancer.
Cancer Research 06/2010; 70(12):5054-63. · 7.86 Impact Factor
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ABSTRACT: The Forkhead Box transcription factor FoxM1 regulates expression of genes that promote cell cycle progression, and it plays essential roles in the development of liver, lung, prostate and colorectal tumors. Thiazolidinediones (TZDs) activate the peroxisome proliferator-activated receptor gamma (PPARγ), a ligand-activated nuclear receptor transcription factor. We found that treatment of the human hepatoma cell lines HepG2 and PLC/PRF/5 cells with TZDs leads to inhibition of FoxM1 gene expression. No PPARγ/retinoid X receptor (RXR) consensus DNA binding sites were detected in the FoxM1 promoter extending to -10 kb upstream, and knockdown of PPARγ had no impact on TZD mediated downregulation of FoxM1 expression. Previously, others showed that PPARγ agonists inhibit the expression and DNA-binding activity of the Sp1 transcription factor. Here we show that Sp1 binds to the FoxM1 promoter region and positively regulates FoxM1 transcription, while mithramycin, a chemotherapy drug that specifically binds GC rich sequences in the DNA and inhibits activities of Sp1, inhibits expression of FoxM1. Our data suggest that TZD mediated suppression of Sp1 is responsible for downregulation of FoxM1 gene expression. Inhibition of FoxM1 expression by TZDs provides a new mechanism for TZD mediated negative regulation of cancer cell growth. FoxM1 expression and activity in cancer cells can be targeted using PPARγ agonists or the anti-neoplastic antibiotic mithramycin.
Cancer biology & therapy 06/2010; 9(12):1008-16. · 2.64 Impact Factor
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ABSTRACT: Reactive oxygen species (ROS) is critical for premature senescence, a process significant in tumor suppression and cancer therapy. Here, we reveal a novel function of the nucleotide excision repair protein DDB2 in the accumulation of ROS in a manner that is essential for premature senescence. DDB2-deficient cells fail to undergo premature senescence induced by culture shock, exogenous oxidative stress, oncogenic stress, or DNA damage. These cells do not accumulate ROS following DNA damage. The lack of ROS accumulation in DDB2 deficiency results from high-level expression of the antioxidant genes in vitro and in vivo. DDB2 represses antioxidant genes by recruiting Cul4A and Suv39h and by increasing histone-H3K9 trimethylation. Moreover, expression of DDB2 also is induced by ROS. Together, our results show that, upon oxidative stress, DDB2 functions in a positive feedback loop by repressing the antioxidant genes to cause persistent accumulation of ROS and induce premature senescence.
Molecular and cellular biology 03/2010; 30(11):2681-92. · 6.06 Impact Factor
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ABSTRACT: Apoptosis induced by DNA damage is an important mechanism of tumor suppression and it is significant also in cancer chemotherapy. Mammalian cells activate the pathways of p53 to induce apoptosis of cells harboring irreparable DNA damages. While p53 induces expression of various pro-apoptotic genes and directly participates in the disruption of mitochondrial membrane polarization, it also increases expression of the cell cycle inhibitor p21 that is a dominant inhibitor of caspase-activation and apoptosis. Here we discuss how Damaged-DNA Binding Protein-2 (DDB2) subdues the level of p21 in cells harboring irreparable DNA damage to support activation of the caspases. We speculate a model in which DDB2 detects and couples the presence of un-repaired DNA damages to the proteolysis of p21, leading to the induction of apoptosis.
Cell Division 01/2010; 5:3. · 3.00 Impact Factor
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ABSTRACT: ARF is a vital tumor suppressor and its loss contributes significantly to cancer. The frequency in which ARF is mutated, deleted or silenced is second to the loss of p53. The most documented and widely accepted activity of ARF is mediated through its activation of the p53 transcriptional program by inhibiting MDM2 function. However, several lines of evidence have surfaced demonstrating that ARF possesses p53-independent functions. One of these p53-independent functions is ARF's regulation of the E2F family. The E2F/DP transcription factor is critical for cell cycle progression. The balance between activator and repressor E2Fs regulates the expression of E2F target genes and thus cell proliferation as well as other cellular functions such as checkpoint, chromosome assembly and repair. Through its ability to bind directly to DP1, ARF can cause dissociation of both activator and repressor E2Fs. While the regulation of the activator E2Fs is related to cell cycle arrest, there is evidence that the regulation of the repressors, E2F4 and E2F5, is significant in maintaining genomic stability.
Cell cycle (Georgetown, Tex.) 01/2010; 9(1):86-9. · 5.36 Impact Factor
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ABSTRACT: DDB2 was identified as a protein involved in the Nucleotide Excision Repair (NER), a major DNA repair mechanism that repairs UV damage to prevent accumulation of mutations and tumorigenesis. However, recent studies indicated additional functions of DDB2 in the DNA damage response pathway. Herein, we discuss the proposed mechanisms by which DDB2 activates NER and programmed cell death upon DNA damage through its E3 ligase activity.
Cell cycle (Georgetown, Tex.) 12/2009; 8(24):4067-71. · 5.36 Impact Factor
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ABSTRACT: The Forkhead box M1 (FoxM1) transcription factor is critical for expression of the genes essential for G(1)/S transition and mitotic progression. To explore the cell cycle regulation of FoxM1, we examined the phosphorylation profile of FoxM1. Here, we show that the phosphorylated status and the activity of FoxM1 increase as cells progress from S to G(2)/M phases. Moreover, dephosphorylation of FoxM1 coincides with exit from mitosis. Using mass spectrometry, we have identified a new conserved phosphorylation site (Ser-251) within the forkhead domain of FoxM1. Disruption of Ser-251 inhibits phosphorylation of FoxM1 and dramatically decreases its transcriptional activity. We demonstrate that the Ser-251 residue is required for CDK1-dependent phosphorylation of FoxM1 as well as its interaction with the coactivator CREB-binding protein (CBP). Interestingly, the transcriptional activity of the S251A mutant protein remains responsive to activation by overexpressed Polo-like kinase 1 (PLK1). Cells expressing the S251A mutant exhibit reduced expression of the G(2)/M phase genes and impaired mitotic progression. Our results demonstrate that the transcriptional activity of FoxM1 is controlled in a cell cycle-dependent fashion by temporally regulated phosphorylation and dephosphorylation events, and that the phosphorylation at Ser-251 is critical for the activation of FoxM1.
Journal of Biological Chemistry 10/2009; 284(44):30695-707. · 4.77 Impact Factor
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ABSTRACT: The transcription factor FoxM1 is over-expressed in most human malignancies. Although it is evident that FoxM1 has critical functions in tumour development and progression, the mechanisms by which FoxM1 participates in those processes are not understood. Here, we describe an essential role of FoxM1 in the regulation of oxidative stress that contributes to malignant transformation and tumour cell survival. We identify a negative feedback loop involving FoxM1 that regulates reactive oxygen species (ROS) in proliferating cells. We show that induction of FoxM1 by oncogenic Ras requires ROS. Elevated FoxM1, in turn, downregulates ROS levels by stimulating expression of ROS scavenger genes, such as MnSOD, catalase and PRDX3. FoxM1 depletion sensitizes cells to oxidative stress and increases oncogene-induced premature senescence. Moreover, tumour cells expressing activated AKT1 are 'addicted' to FoxM1, as they require continuous presence of FoxM1 for survival. Together, our results identify FoxM1 as a key regulator of ROS in dividing cells, and provide insights into the mechanism how tumour cells use FoxM1 to control oxidative stress to escape premature senescence and apoptosis.
The EMBO Journal 09/2009; 28(19):2908-18. · 9.20 Impact Factor
