This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Carvajal, D. Articles by Vassilev, L. T. Search for Related Content PubMed PubMed Citation Articles by Carvajal, D. Articles by Vassilev, L. T.

Activation of p53 by MDM2 Antagonists Can Protect Proliferating Cells from Mitotic Inhibitors

Discovery Oncology, Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey

Requests for reprints: Lyubomir T. Vassilev, Discovery Oncology, Hoffmann-La Roche Inc., 340 Kingsland Street, Nutley, NJ 07110. Phone: 973-235-8106; Fax: 973-235-6185; E-mail: lyubomir.vassilev{at}roche.com.

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
Recent studies have shown that activation of cell cycle checkpoints can protect normal proliferating cells from mitotic inhibitors by preventing their entry into mitosis. These studies have used genotoxic agents that act, at least in part, by activation of the p53 pathway. However, genotoxic drugs are known also to have p53-independent activities and could affect the sensitivity of tumor cells to antimitotic agents. Recently, we have developed the first potent and selective small-molecule inhibitors of the p53-MDM2 interaction, the nutlins, which activate the p53 pathway only in cells with wild-type but not mutant p53. Using these compounds, we show that p53 activation leads to G₁ and G₂ phase arrest and can protect cells from mitotic block and apoptosis caused by paclitaxel. Pretreatment of HCT116 and RKO colon cancer cells (wild-type p53) or primary human fibroblasts (1043SK) with nutlins for 24 hours followed by incubation with paclitaxel for additional 48 hours did not increase significantly their mitotic index and protected the cells from the cytotoxicity of paclitaxel. Cancer cells with mutant p53 (MDA-MB-435) responded to the same treatment with mitotic arrest and massive apoptosis. These results have two major implications for cancer therapy. First, p53-activating therapies may have antagonistic effect when combined with mitotic poisons. Second, pretreatment with MDM2 antagonists before chemotherapy of tumors with mutant p53 may offer a partial protection to proliferating normal tissues.

Key Words: p53 • MDM2 • cell cycle • paclitaxel • chemoprotection

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
Cell cycle is a highly ordered set of biochemical events leading to the faithful duplication and segregation of eukaryotic chromosomes (1, 2). This process is tightly controlled by checkpoint mechanisms evolved to prevent cells from entering any cell cycle phase before the completion of the previous one (3). Therefore, agents that interfere with processes specific for any particular cell cycle phase will be inactive if the cells are prohibited from entering their targeted phase. This phenomenon is in the basis of the recently proposed strategy for protection of normal cells from cytotoxicity of chemotherapeutic agents (4–6). Normal proliferating cells possess fully functional checkpoint controls and respond to treatment with cytotoxic agents, most of which are genotoxic, by cell cycle arrest in G₁ and/or G₂ phase. At the same time, most cancer cells that have suffered multiple genetic alterations and frequently lack effective checkpoint regulation may continue cycling through their apoptotic death. Thus, one can achieve partial protection of normal cells by pretreatment with low doses of common genotoxic drugs (7). This strategy is most applicable to chemotherapy with mitotic inhibitors, which are strictly dependent for their activity on the ability of the cells to enter mitosis. Following this approach, pretreatment of cancer cells with low doses of the genotoxic drug doxorubicin have shown cell cycle arrest and partial protection from mitotic poisons (e.g., paclitaxel, epothilone, and vinblastine). This effect is mostly due to induction of the p53 pathway and is mediated by p21^Waf1/CIP1 because p53-null or p21-null cancer cells cannot be protected (7). However, doxorubicin and other DNA-damaging agents can trigger multiple molecular events including activation of p53-independent checkpoints and thus may partially protect the cancer cells during chemotherapy. This can be avoided by using agents targeted specifically at the p53 pathway.

The tumor suppressor p53 plays a pivotal role in cellular response to genotoxic damage or other forms of stress by inducing cell cycle arrest or apoptosis and thus preventing the propagation of DNA damage that may lead to malignant cell transformation (8, 9). p53 is a potent transcription factor that controls the activity of multiple target genes involved in the control of cell cycle or apoptosis. One of the main functions of activated p53 is induction of the G₁-S and G₂-M checkpoints of the cell cycle. This function is mediated by the product of the immediate downstream gene p21^Waf1/CIP1 (8, 10). In proliferating cells that are not subjected to stress, p53 level is tightly controlled by its negative regulator MDM2, which binds p53 and modulates its transcriptional activity and stability (11–15). Recently, we have identified the first potent and selective small-molecule inhibitors of p53-MDM2 binding, the nutlins (16). These compounds can release p53 from negative control and activate the p53 pathway, leading to cell cycle arrest and apoptosis only in cancer cells that have retained wild-type p53 but not in cells in which p53 is deleted or disabled by mutation Cellular activity of nutlins is derived solely from activation of the p53 pathway and therefore they represent unique tools for p53-dependent modulation of the cell cycle in proliferating cells.

Due to its high importance in protection from tumor development, p53 is mutated in 50% of all human tumors rendering them practically insensitive to p53-activating agents (9, 17). This offers the opportunity to develop an improved protective strategy for protection of normal proliferating tissues without affecting the sensitivity of tumors with mutant p53 to antimitotic agents. Here, we use nutlins as p53-activating agents and show that they can induce G₁-S and G₂-M checkpoints and can protect normal proliferating cells but not cancer cells with mutant p53 from cytotoxicity of paclitaxel. Thus, MDM2 antagonists may offer a new modality for partial protection of normal proliferating tissues during antimitotic chemotherapy of p53-deficient tumors.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
Cells and Drug Treatment. RKO cells were a gift from Dr. B. Vogelstein (Johns Hopkins Oncology Center, Baltimore, MD) and MDA-MB-435 were provided by Dr. P. Steeg (National Cancer Institute, Bethesda, MD). HCT116, H460, LOX, SW480, SJSA-1, and 1043SK cells were purchased from American Type Culture Collection (Rockville, MD) and grown in the recommended medium supplemented with 10% heat-inactivated fetal bovine serum (Invitrogen, San Diego, CA) in a humidified environment with 5% CO₂. Drugs were dissolved in DMSO and kept as 10-mmol/L stock solutions in small aliquots at –20°C. For staining of cells, acridine orange and propidium iodide (Sigma Chemical Co., St. Louis, MO) were dissolved in PBS at 0.3 mg/mL and added to culture medium at 1 µg/mL. After 5- to 10-minute incubation at 37°C, cells were examined under fluorescence microscope and images were taken by SPOT digital camera. Cell viability was determined either by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay as previously described (18) or by the Guava personal cell analyzer using the Guava ViaCount kit (Guava Technologies, Hayward, CA).

Cell Cycle Analysis. For analysis of cell cycle distribution, 10⁶ cells were seeded in 75-cm² flasks 24 hours before drug treatment. They were labeled with 20 µmol/L bromodeoxyuridine (Sigma) added to the culture medium for 2 hours before harvesting. The cells were washed twice by PBS and collected by trypsinization. They were fixed with 70% ethanol and stored overnight at –20°C. After thawing, cells were washed twice in cold PBS and resuspended in 1 mL of 2N HCl and 0.5% Triton X-100 in PBS for 30 minutes at room temperature. Cells were collected by centrifugation and the cell pellet was neutralized with 1 mL of 0.1 mol/L sodium tetraborate (pH 8.5), washed with PBS and resuspended in 0.1 mL of 0.5% Tween 20 and 1% bovine serum albumin in PBS. Anti-bromodeoxyuridine FITC-conjugated monoclonal antibody (20 µL, Becton Dickinson, San Jose, CA) was added and incubated for 30 minutes in the dark at room temperature. After one wash with Tween 20/bovine serum albumin/PBS buffer, the cell pellet was resuspended in 0.5 mL of PBS with propidium iodide (50 µg/mL), filtered through filter caps, and bromodeoxyuridine incorporation was analyzed by dual-color flow cyometric DNA techniques in the FACSCalibur cytometer (Becton Dickinson, Franklin Lakes, NJ) using CellQuest software. Cell number in each phase of the cell cycle was determined and calculated as a percentage of the total cell population.

Quantitative PCR. Cells were seeded in 96-well plates (10⁴ cells per well) 24 hours before treatment. They were lysed and total RNA extracted using the ABI 6700 robotic workstation (Applied Biosystems, Foster City, CA). Aliquots containing 5 µg total RNA were converted to cDNA using the TaqMan RT reagents kit (Applied Biosystems). The relative quantity of the p21 transcripts was determined by TaqMan using gene-specific primer/probe sets and 18S RNA as a normalization control. The sequence of the p21 primers and probe were F: CTG-AGA-CTC-TCA-GGG-TCG-AA; R: CGG-CGT-TTG-GAG-TGG-TAG-AA; and probe: TTG-GCT-CAC-TGC-AAG-CTC-GCC-CTT).

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
MDM2 Antagonists Activate p53 and Arrest Cell Cycle Progression. Induction of cell cycle arrest at the G₁-S and G₂-M border is one of the main functions of activated p53. This arrest is mediated predominantly by the product of the p53 target gene p21^Waf1/CIP1 (8, 10) encoding a potent cyclin-dependent kinase (CDK) inhibitor. Inhibition of CDK2/cyclin E and CDK4/cyclin D activity is thought to block cell cycle progression in late G₁ phase just before entering into S phase. Inhibition of CDK1/cyclin B kinase activity leads to a block at the G₂-M phase border of the cell cycle. Recently, we developed a class of specific small-molecule antagonists of p53-MDM2 interaction, the nutlins, which can release p53 from negative control and activate the p53 pathway (16). These cis-imidazoline compounds represent valuable tools for modulation of the p53 pathway in living cells. We showed previously that they can effectively arrest cell cycle progression in cells with wild-type p53 but not in cells in which p53 is missing or disabled as a transcription factor. Each of these compounds can be separated postsynthetically into two enantiomers, arbitrarily called (a) and (b). Enantiomer (a) binds to MDM2 protein with 150-fold higher potency than enantiomer (b). Thus, the inactive enantiomer (b) offers an excellent control for cellular activities unrelated to MDM2 inhibition (16).

To show that p21 activation is involved in nutlin-induced cell cycle arrest, we incubated two human cancer cell lines with wild-type p53, HCT116 (colon cancer) and SJSA-1 (osteosarcoma) with nutlin-1 (racemic), or the active or inactive enantiomer of nutlin-3 for 24 hours and measured the expression of p21 by quantitative real-time PCR (Fig. 1A). In cells treated with nutlin-1 and the active enantiomer of nutlin-3 a dose-dependent elevation in p21 expression was observed. At 10 µmol/L, both nutlins induced p21 transcription 10-fold in HCT116 and 20-fold in SJSA-1 cells. Differences in the level of induction reflect differences in the basal level of p21 expression because the induced levels were similar between the two cell lines (data not shown). The inactive enantiomer did not show detectable elevation in p21 expression confirming the high selectivity of MDM2 antagonists.

View larger version (35K): [in this window] [in a new window] [Download PPT slide]   Figure 1. MDM2 antagonists activate the p53 pathway and induce cell cycle arrest in G1 and G2 phase. A, activation of p21 gene expression by nutlins in cancer cells with wild-type p53. Exponentially growing HCT116 and SJSA-1 cells were treated with nutlin-1 (racemic), the active enantiomer of nutlin-3 (nutlin-3a) or the inactive enantiomer nutlin-3b for 24 hours and the expression level of the p21 gene was determined by real-time quantitative PCR. It is expressed as fold activation over the expression level in control cells. B, HCT116 and SJSA-1 cells were incubated with the indicated concentrations of Nutlin-1 for 24 hours and their cell cycle distribution was determined by bromodeoxyuridine-labeling and fluorescence-activated cell-sorting analysis. The cells in G1, S, and G2-M phases were calculated as a percentage of the total cell population.

Activation of p53-regulated G₁ and G₂ Checkpoints Protect Cancer Cells from Paclitaxel. The activation of G₁-S and G₂-M checkpoints by p53 is a mechanism evolved to protect proliferating cells from propagation of DNA damage that may occur during chromosome replication and segregation. Cells prevented from entering mitosis should be protected effectively from mitotic inhibitors that only work throughout cell division by hindering the assembly of functional mitotic spindles. Taxanes are one of the most widely used classes of chemotherapeutic agents that block cell cycle progression in metaphase of mitosis by interfering with microtubule dynamics (19, 20). Mitotic block is followed by induction of apoptosis and cell death. Taxanes and other mitotic poisons (e.g., vinblastine and vincristine) are among the most potent cytotoxic drugs. However, due to their M phase–specific mechanism of action, mitotic inhibitors do not induce apoptosis in nonproliferating cells or cells blocked in cycle phases other then mitosis.

We tested the ability of nutlins to protect proliferating cancer cells from the most widely used mitotic inhibitor, paclitaxel. SJSA-1 cells were incubated with nutlin-3 or paclitaxel for 24 hours, or nutlin-3 for 24 hours followed by paclitaxel for another 24 hours. Paclitaxel (250 nmol/L) treatment caused a massive accumulation of cells with rounded morphology and condensed chromosomes typical for metaphase (Fig. 2). Pretreatment with nutlin-3 (4 µmol/L) for 24 hours reduced dramatically mitotic figures from 93% (paclitaxel alone) to 5% (nutlin-3 + paclitaxel), although significant percentage of the cells showed deterioration due to induction of p53-dependent apoptosis in this cell line (16). Similar observations were made with HCT116 and RKO cells (data not shown). These experiments show that nutlins can effectively protect cancer cells from entering mitosis, thus making them much less sensitive to paclitaxel.

View larger version (41K): [in this window] [in a new window] [Download PPT slide]   Figure 2. Pretreatment with nutlins can protect cancer cells with wild-type p53 from mitotic arrest by paclitaxel. SJSA-1 osteosarcoma cells were incubated with 4 µmol/L of the active enantiomer nutlin-3a for 24 hours (A), 250 µmol/L paclitaxel for 24 hours (B), and 4 µmol/L nutlin-3a for 24 hours followed by 250 µmol/L paclitaxel for another 24 hours (C). Live cells were stained with acridine orange and examined by fluorescence microscopy. Bars, 50 µm.

View larger version (19K): [in this window] [in a new window] [Download PPT slide]   Figure 3. Nutlins protect cancer cells with wild-type p53 from paclitaxel. HCT116 and RKO cells (2,500 cells per well, 96-well plates) were grown for 24 hours before treatment with nutlin-3 (6 µmol/L) for another 24 hours followed by 48 hours treatment with paclitaxel. Cell viability was determined 48 hours after paclitaxel addition using the MTT assay.

View larger version (70K): [in this window] [in a new window] [Download PPT slide]   Figure 4. Proliferating human skin fibroblasts 1043SK can be protected partially from the cytotoxicity of paclitaxel by nutlins. A, nutlin-1 activates the p53 pathway in proliferating fibroblasts. 1043SK cells were incubated with increasing concentrations of nutlin-1 for 24 hours and the transcription level of the p53 target gene p21 was measured in cell lysates by quantitative PCR. B, pretreatment with nutlin-1 can protect diploid fibroblasts from paclitaxel. Exponentially growing 1043SK cells (1 x 105 cells per well in six-well plates) were incubated with 6 µmol/L nutlin-1 for 24 hours followed by 48 hours incubation with a range of paclitaxel concentrations. Cells were washed with drug-free medium and their viability was measured after an additional 5-day incubation in fresh, drug-free medium. C, Fibroblasts survive high doses of paclitaxel in the presence of nutlins. Phase contrast images of 1043SK cells subjected to the treatment scheme outlined in (B) and control untreated cells.

View larger version (22K): [in this window] [in a new window] [Download PPT slide]   Figure 5. MDM2 antagonists may protect proliferating human skin fibroblasts during chemotherapy of tumors with mutant p53. A, normal proliferating cells that possess wild-type p53 and intact p53 pathway will respond to pretreatment with nutlins by G1 and G2 phase arrest and can be protected from the cytotoxicity of paclitaxel. They may resume cycling after drug removal. B, nutlin pretreatment of cancer cells in which p53 is disabled by mutation or deletion will not affect their cell cycle progression and paclitaxel will induce mitotic arrest and apoptotic cell death.

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 6. Sensitivity of cancer cells with mutant p53 to paclitaxel is not affected by MDM2 antagonists. Proliferating MDA-MB-435 breast cancer cells (mutant p53) were incubated with 6 µmol/L nutlin-1 for 24 hours (A) or 250 nmol/L paclitaxel for 24 hours (B), or 6 µmol/L nutlin-1 for 24 hours followed by 250 nmol/L paclitaxel for additional 24 hours (C). D, exponentially growing MDA-MB-435 cells were incubated with 6 µmol/L nutlin-1 for 24 hours followed by 48 hours incubation with increasing paclitaxel concentrations. Cells were washed with drug-free medium and their viability was determined by the Guava personal cell analyzer after 5 days incubation in drug-free medium.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

The experiments described in this study use primary fibroblasts as a model system for proliferating normal human cells. Fibroblasts may not represent the most sensitive tissues adversely affected during cytotoxic chemotherapy (e.g., proliferating cells from gut epithelium or hematopoietic system). However, treatment of nude mice with nutlin-3 doses that effectively inhibit the growth of tumor xenografts for 3 weeks did not reveal overt toxicity, thus suggesting that normal tissues may have higher tolerance to p53 activation (16, 21). Additional experiments in which the protective role of MDM2 antagonists is assessed on multiple normal tissues in vivo may help to better understand the clinical potential of this approach.

Another implication of our studies concerns combination therapy with antimitotic agents. Our data on the protective role of MDM2 antagonists in cancer cells with wild-type p53 suggest that these agents should be used with caution when combined with mitotic poisons. Paclitaxel and other mitotic chemotherapeutics are frequently used together with genotoxic drugs (e.g., DNA binders, alkylating agents, topoisomerase inhibitors, etc.). These agents can activate the p53 pathway in tumors with wild-type p53 via genotoxic stress. Therefore, if used before, or in combination with, mitotic drugs they could protect the cancer cells from the mitotic agents. This has been shown in vitro and in vivo by the decreased sensitivity of HCT116 colon cancer cells to paclitaxel compared with their isogenic p53-null or p21-null variants (28). Taken together, these observations suggest that p53-activating agents should be used with caution in combination therapy with mitotic poisons in patients whose tumors harbor wild-type p53.

	Acknowledgments

 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

We thank Mary Simcox for critically reading the manuscript.

	Footnotes

 
¹ Unpublished data.

Received 10/ 4/04. Revised 12/12/04. Accepted 12/20/04.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Pardee AB, Dubrow R, Hamlin JL, Kletzien RF. Animal cell cycle. Annu Rev Biochem 1978;47:715–50.[CrossRef][Medline]
2. Morgan DO. Principles of CDK regulation. Nature 1995;374:131–4.[CrossRef][Medline]
3. Lukas J, Lukas C, Bartek J. Mammalian cell cycle checkpoints: signalling pathways and their organization in space and time. DNA Repair 2004;3:997–1007.[CrossRef][Medline]
4. Blagosklonny MV, Pardee AB. Exploiting cancer cell cycling for selective protection of normal cells. Cancer Res 2001;61:4301–5.[Abstract/Free Full Text]
5. Blagosklonny MV, Darzynkiewicz Z. Cyclotherapy: protection of normal cells and unshielding of cancer cells. Cell Cycle 2002;1:375–82.[Medline]
6. Keyomarsi K, Pardee AB. Selective protection of normal proliferating cells against the toxic effects of chemotherapeutic agents. Prog Cell Cycle Res 2003;5:527–32.[Medline]
7. Blagosklonny MV, Robey R, Bates S, Fojo T. Pretreatment with DNA-damaging agents permits selective killing of checkpoint-deficient cells by microtubule-active drugs. J Clin Invest 2000;105:533–9.[Medline]
8. Levine AJ. p53, the cellular gatekeeper for growth and division. Cell 1997;88:323–31.[CrossRef][Medline]
9. Vogelstein B, Lane D, Levine AJ. Surfing the p53 network. Nature 2000;408:307–10.[CrossRef][Medline]
10. el-Deiry WS, Tokino T, Velculescu VE, et al. WAF1, a potential mediator of p53 tumor suppression. Cell 1993;75:817–25.[CrossRef][Medline]
11. Oliner JD, Pietenpol JA, Thiagalingam S, Gyuris J, Kinzler KW, Vogelstein B. Oncoprotein MDM2 conceals the activation domain of tumour suppressor p53. Nature 1993;362:857–60.[CrossRef][Medline]
12. Freedman DA, Wu L, Levine AJ. Functions of the MDM2 oncoprotein. Cell Mol Life Sci 1999;55:96–107.[CrossRef][Medline]
13. Momand J, Jung D, Wilczynski S, Niland J. The MDM2 gene amplification database. Nucleic Acids Res 1998;26:3453–9.[Abstract/Free Full Text]
14. Michael D, Oren M. The p53-Mdm2 module and the ubiquitin system. Semin Cancer Biol 1998;13:49–58.
15. Picksley SM, Lane, DP. The p53-mdm2 autoregulatory feedback loop: a paradigm for the regulation of growth control by p53? Bioessays 1993;15:689–90.[CrossRef][Medline]
16. Vassilev LT, Vu BT, Graves B, et al. In vivo activation of the p53 pathway by small-molecule antagonists of MDM2. Science 2004;303:844–8.[Abstract/Free Full Text]
17. Hollstein M, Sidransky D, Vogelstein B, Harris CC. p53 mutations in human cancers. Science 1991;253:49–53.[Abstract/Free Full Text]
18. Vassilev LT, Kazmer S, Marks IM, et al. Cell-based screening approach for antitumor drug leads which exploits sensitivity differences between normal and cancer cells: identification of two novel cell-cycle inhibitors. Anticancer Drug Des 2001;16:7–17.[Medline]
19. Hadfield JA, Ducki S, Hirst N, McGown AT. Tubulin and microtubules as targets for anticancer drugs. Prog Cell Cycle Res 2001;5:309–25.
20. Jordan MA, Wilson L. Microtubules as a target for anticancer drugs. Nat Rev Cancer 2004;4:253–65.[CrossRef][Medline]
21. Vassilev LT. Small-molecule antagonists of p53-MDM2 binding: research tools and potential therapeutics. Cell Cycle 2004;3:419–21.[Medline]
22. Khan SH, Wahl GM. p53 and pRb prevent rereplication in response to microtubule inhibitors by mediating a reversible G₁ arrest. Cancer Res 1998;58:396–401.[Abstract/Free Full Text]
23. Agarwal ML, Agarwal A, Taylor WR, Stark GR. p53 controls both the G₂/M and the G₁ cell cycle checkpoints and mediates reversible growth arrest in human fibroblasts. Proc Natl Acad Sci U S A 2004;92:8493–7.
24. Blagosklonny MV. Sequential activation and inactivation of G₂ checkpoints for selective killing of p53-deficient cells by microtubule-active drugs. Oncogene 2002;21:6249–54.[CrossRef][Medline]
25. Perego P, Corna E, De Cesare M, et al. Role of apoptosis and apoptosis-related genes in cellular response and antitumor efficacy of anthracyclines. Curr Med Chem 2004;8:31–7.
26. Sakowicz R, Finer JT, Beraud C, et al. Antitumor activity of a kinesin inhibitor. Cancer Res 2004;64:3276–80.[Abstract/Free Full Text]
27. Harrington EA, Bebbington D, Moore J, et al. VX-680, a potent and selective small-molecule inhibitor of the Aurora kinases, suppresses tumor growth in vivo. Nat Med 2004;10:262–7.[CrossRef][Medline]
28. Stewart ZA, Mays D, Pietenpol JA. Defective G₁-S cell cycle checkpoint function sensitizes cells to microtubule inhibitor-induced apoptosis. Cancer Res 2004;59:3831–7.

This article has been cited by other articles:

				T. Van Maerken, L. Ferdinande, J. Taildeman, I. Lambertz, N. Yigit, L. Vercruysse, A. Rihani, M. Michaelis, J. Cinatl Jr, C. A. Cuvelier, et al. Antitumor Activity of the Selective MDM2 Antagonist Nutlin-3 Against Chemoresistant Neuroblastoma With Wild-Type p53 J Natl Cancer Inst, November 10, 2009; (2009) djp355v1. [Abstract] [Full Text] [PDF]

				W. Du, J. Wu, E. M. Walsh, Y. Zhang, C. Y. Chen, and Z.-X. J. Xiao Nutlin-3 Affects Expression and Function of Retinoblastoma Protein: ROLE OF RETINOBLASTOMA PROTEIN IN CELLULAR RESPONSE TO NUTLIN-3 J. Biol. Chem., September 25, 2009; 284(39): 26315 - 26321. [Abstract] [Full Text] [PDF]

				M. Miyachi, N. Kakazu, S. Yagyu, Y. Katsumi, S. Tsubai-Shimizu, K. Kikuchi, K. Tsuchiya, T. Iehara, and H. Hosoi Restoration of p53 Pathway by Nutlin-3 Induces Cell Cycle Arrest and Apoptosis in Human Rhabdomyosarcoma Cells Clin. Cancer Res., June 15, 2009; 15(12): 4077 - 4084. [Abstract] [Full Text] [PDF]

				Y. Fang, B. Kong, Q. Yang, D. Ma, and X. Qu MDM2 309 polymorphism is associated with missed abortion Hum. Reprod., June 1, 2009; 24(6): 1346 - 1349. [Abstract] [Full Text] [PDF]

				P. Secchiero, E. Melloni, M. G. di Iasio, M. Tiribelli, E. Rimondi, F. Corallini, V. Gattei, and G. Zauli Nutlin-3 up-regulates the expression of Notch1 in both myeloid and lymphoid leukemic cells, as part of a negative feedback antiapoptotic mechanism Blood, April 30, 2009; 113(18): 4300 - 4308. [Abstract] [Full Text] [PDF]

				H. Shen, D. M. Moran, and C. G. Maki Transient Nutlin-3a Treatment Promotes Endoreduplication and the Generation of Therapy-Resistant Tetraploid Cells Cancer Res., October 15, 2008; 68(20): 8260 - 8268. [Abstract] [Full Text] [PDF]

				S. Shangary and S. Wang Targeting the MDM2-p53 Interaction for Cancer Therapy Clin. Cancer Res., September 1, 2008; 14(17): 5318 - 5324. [Abstract] [Full Text] [PDF]

				R. J. Jones, Q. Chen, P. M. Voorhees, K. H. Young, N. Bruey-Sedano, D. Yang, and R. Z. Orlowski Inhibition of the p53 E3 Ligase HDM-2 Induces Apoptosis and DNA Damage-Independent p53 Phosphorylation in Mantle Cell Lymphoma Clin. Cancer Res., September 1, 2008; 14(17): 5416 - 5425. [Abstract] [Full Text] [PDF]

				M. Lu, A. Strohecker, F. Chen, T. Kwan, J. Bosman, V. C. Jordan, and V. L. Cryns Aspirin Sensitizes Cancer Cells to TRAIL-Induced Apoptosis by Reducing Survivin Levels Clin. Cancer Res., May 15, 2008; 14(10): 3168 - 3176. [Abstract] [Full Text] [PDF]

				M. Chatterjee, C. Rancso, T. Stuhmer, N. Eckstein, M. Andrulis, C. Gerecke, H. Lorentz, H.-D. Royer, and R. C. Bargou The Y-box binding protein YB-1 is associated with progressive disease and mediates survival and drug resistance in multiple myeloma Blood, April 1, 2008; 111(7): 3714 - 3722. [Abstract] [Full Text] [PDF]

				C. F. Cheok, A. Dey, and D. P. Lane Cyclin-Dependent Kinase Inhibitors Sensitize Tumor Cells to Nutlin-Induced Apoptosis: a Potent Drug Combination Mol. Cancer Res., November 1, 2007; 5(11): 1133 - 1145. [Abstract] [Full Text] [PDF]

				P. Das, K. Vaiphei, D. Jain, and Jai Dev Wig p53 and mdm2 Expression in Colorectal Carcinoma: A Correlative Analysis With Clinical Staging and Histological Parameters International Journal of Surgical Pathology, October 1, 2007; 15(4): 335 - 345. [Abstract] [PDF]

				A. Efeyan, A. Ortega-Molina, S. Velasco-Miguel, D. Herranz, L. T. Vassilev, and M. Serrano Induction of p53-Dependent Senescence by the MDM2 Antagonist Nutlin-3a in Mouse Cells of Fibroblast Origin Cancer Res., August 1, 2007; 67(15): 7350 - 7357. [Abstract] [Full Text] [PDF]

				E. Drakos, A. Thomaides, L. J. Medeiros, J. Li, V. Leventaki, M. Konopleva, M. Andreeff, and G. Z. Rassidakis Inhibition of p53-Murine Double Minute 2 Interaction by Nutlin-3A Stabilizes p53 and Induces Cell Cycle Arrest and Apoptosis in Hodgkin Lymphoma Clin. Cancer Res., June 1, 2007; 13(11): 3380 - 3387. [Abstract] [Full Text] [PDF]

				J. A. Bernal and A. Hernandez p53 Stabilization can be Uncoupled from its Role in Transcriptional Activation by Loss of PTTG1/Securin J. Biochem., May 1, 2007; 141(5): 737 - 745. [Abstract] [Full Text] [PDF]

				M. Jiang, N. Pabla, R. F. Murphy, T. Yang, X.-M. Yin, K. Degenhardt, E. White, and Z. Dong Nutlin-3 Protects Kidney Cells during Cisplatin Therapy by Suppressing Bax/Bak Activation J. Biol. Chem., January 26, 2007; 282(4): 2636 - 2645. [Abstract] [Full Text] [PDF]

				P. Secchiero, F. Corallini, A. Gonelli, R. Dell'Eva, M. Vitale, S. Capitani, A. Albini, and G. Zauli Antiangiogenic Activity of the MDM2 Antagonist Nutlin-3 Circ. Res., January 5, 2007; 100(1): 61 - 69. [Abstract] [Full Text] [PDF]

				A. A. Levesque and A. Eastman p53-based cancer therapies: is defective p53 the Achilles heel of the tumor? Carcinogenesis, January 1, 2007; 28(1): 13 - 20. [Abstract] [Full Text] [PDF]

				D. Kranz and M. Dobbelstein Nongenotoxic p53 Activation Protects Cells against S-Phase-Specific Chemotherapy Cancer Res., November 1, 2006; 66(21): 10274 - 10280. [Abstract] [Full Text] [PDF]

				K. Kojima, M. Konopleva, T. McQueen, S. O'Brien, W. Plunkett, and M. Andreeff Mdm2 inhibitor Nutlin-3a induces p53-mediated apoptosis by transcription-dependent and transcription-independent mechanisms and may overcome Atm-mediated resistance to fludarabine in chronic lymphocytic leukemia Blood, August 1, 2006; 108(3): 993 - 1000. [Abstract] [Full Text] [PDF]

				L. T. Vassilev, C. Tovar, S. Chen, D. Knezevic, X. Zhao, H. Sun, D. C. Heimbrook, and L. Chen Selective small-molecule inhibitor reveals critical mitotic functions of human CDK1 PNAS, July 11, 2006; 103(28): 10660 - 10665. [Abstract] [Full Text] [PDF]

				P. Secchiero, E. Barbarotto, M. Tiribelli, C. Zerbinati, M. G. di Iasio, A. Gonelli, F. Cavazzini, D. Campioni, R. Fanin, A. Cuneo, et al. Functional integrity of the p53-mediated apoptotic pathway induced by the nongenotoxic agent nutlin-3 in B-cell chronic lymphocytic leukemia (B-CLL) Blood, May 15, 2006; 107(10): 4122 - 4129. [Abstract] [Full Text] [PDF]

				K. Kojima, M. Konopleva, I. J. Samudio, M. Shikami, M. Cabreira-Hansen, T. McQueen, V. Ruvolo, T. Tsao, Z. Zeng, L. T. Vassilev, et al. MDM2 antagonists induce p53-dependent apoptosis in AML: implications for leukemia therapy Blood, November 1, 2005; 106(9): 3150 - 3159. [Abstract] [Full Text] [PDF]

				Z. N. Demidenko, D. Halicka, J. Kunicki, J. A. McCubrey, Z. Darzynkiewicz, and M. V. Blagosklonny Selective Killing of Adriamycin-Resistant (G2 Checkpoint-Deficient and MRP1-Expressing) Cancer Cells by Docetaxel Cancer Res., May 15, 2005; 65(10): 4401 - 4407. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Carvajal, D. Articles by Vassilev, L. T. Search for Related Content PubMed PubMed Citation Articles by Carvajal, D. Articles by Vassilev, L. T.