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Cell Growth & Differentiation Vol. 12, 481-486, September 2001
© 2001 American Association for Cancer Research

Involvement of p38 Kinase in Hydroxyurea-induced Differentiation of K562 Cells1

Joo-In Park2, Hee-Sun Choi, Jin-Sook Jeong, Jin-Yeong Han and In-Hoo Kim

Institute of Medical Science and Departments of Biochemistry [J-I. P., H-S. C.], Pathology [J-S. J.], and Clinical Pathology [J-Y. H.], Dong-A University College of Medicine, Busan 602-103, Korea, and Department of Molecular and Cellular Biology [I-H. K.], Baylor College of Medicine, Houston, Texas 77030


    Abstract
 TOP
 Abstract
 Introduction
 Results
 Discussion
 Materials and Methods
 References
 
Hydroxyurea is a differentiation-inducing agent of human erythroleukemia K562 cells. However, the cellular mechanisms by which hydroxyurea exerts its effects on tumor cells, leading to the inhibition of cell growth and the induction of differentiation markers, are largely unknown. This study examined the role of different mitogen-activated protein kinase signal transduction pathways in hydroxyurea-induced erythroid differentiation of K562 cells. Using a panel of anti-extracellular signal-related kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 phosphospecific antibodies, we demonstrated that phosphorylation of ERK and JNK is decreased after the treatment of cells with hydroxyurea, whereas phosphorylation of p38 is increased. Moreover, inhibition of ERK activity by PD98059 induced erythroid differentiation, and it acted synergistically with hydroxyurea on hemoglobin synthesis, whereas inhibition of p38 activity by SB203580 inhibited induction of hemoglobin production by hydroxyurea. These findings suggest that the activation of p38 kinase may play important roles in the signal transduction mechanisms of hydroxyurea leading to erythroid differentiation.


    Introduction
 TOP
 Abstract
 Introduction
 Results
 Discussion
 Materials and Methods
 References
 
Hydroxyurea is a free-radical quencher that inhibits the cellular enzyme ribonucleoside diphosphate reductase and, in so doing, reduces the levels of deoxyribonucleotides (1) . Hydroxyurea has been used over the last 30 years for the treatment of human diseases such as chronic myelogenous leukemia, myeloproliferative syndromes, and, more recently, sickle cell anemia (2, 3, 4, 5, 6) . Biologically, hydroxyurea has been shown to affect the morphology and the growth rate of mammalian cells, as well as to induce gene expression (7 , 8) . It induces differentiation in the human erythroleukemia cell line K562. However, despite its well-known biological and clinical importance, its mechanisms of action remain unknown. For example, the mechanisms by which it transduces its signal to the nucleus leading to nuclear activation and gene expression, which ultimately result in regulation of growth and differentiation, is poorly understood.

Recently, a family of serine-threonine protein kinases that is structurally similar yet functionally distinct has been identified. These MAP3 kinases fall into four distinct groups: the ERKs (9 , 10) , the JNKs (11) , p38 (12) , and Erk5/Big mitogen-active protein kinase 1 (13) . The MAP kinase signaling cascade has been shown to regulate a wide variety of cellular events, such as cell proliferation, differentiation, and development (10 , 14 , 15) , and it may therefore be a potential target of hydroxyurea action. To learn more about the signaling pathways used by hydroxyurea and the molecules which are involved in transducing signaling from hydroxyurea, we investigated whether these MAP kinase pathways are targets of this compound during erythroid differentiation of K562 cells. Treatment of K562 cells with hydroxyurea leads to erythroid differentiation as evidenced by the inhibition of cell proliferation and the induction of hemoglobin synthesis. The activation of p38 kinase and the inhibition of ERK during erythroid differentiation suggest that erythroid differentiation induced by hydroxyurea is mediated through activation of the p38 kinase in K562 cells.


    Results
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 Abstract
 Introduction
 Results
 Discussion
 Materials and Methods
 References
 
Hydroxyurea Induces Erythroid Differentiation of K562 Cells.
To assess the effect of hydroxyurea on the induction of cellular differentiation, exponentially growing K562 cells were treated with 200–400 µM hydroxyurea for up to 4 days (Fig. 1)Citation . The growth of K562 cells was inhibited by hydroxyurea (Fig. 1a)Citation . Next, the hydroxyurea-induced erythroid differentiation was determined by using the benzidine staining, in which the fraction of benzidine-positive cells is proportional to the degree of differentiation into hemoglobinized cells (16 , 17) . As shown in Fig. 1bCitation , the fraction of benzidine-positive cells from the culture treated with hydroxyurea increased.



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Fig. 1. Time course of hydroxyurea-induced cell growth inhibition (a) and hemoglobinization (b). Hemoglobinization and cell number/ml were determined after 6–96 h incubation in the presence of 200–400 µM of hydroxyurea, and in untreated cells (control). Data represent the mean ± SD from five independent experiments.

 
Hydroxyurea Modulates MAP Kinase Pathways in K562 Cells.
We have demonstrated that hydroxyurea is able to induce erythroid differentiation of K562 cells. Little is known on signal transduction pathways in hydroxyurea-induced differentiation. Therefore, we investigated the possible involvement of the MAP kinases ERK1/2, JNK, and p38 in the hydroxyurea-induced cellular differentiation of K562 cells. Cells were treated with 400 µM hydroxyurea for different times as indicated (Fig. 2)Citation , harvested and lysed, and the proteins were subjected to immunoblot analysis using phosphospecific antibodies against the respective MAP kinases. These antibodies specifically recognize the activated, diphosphorylated form of ERK1/2 (18) , JNK1/2 (19) , and p38 (20) . We observed diphosphorylation of ERK after hydroxyurea treatment (Fig. 2)Citation . In contrast to ERK signaling, p38 revealed a sustained phosphorylation starting 4 h after hydroxyurea addition and lasting for the entire observation period of 4 days (Fig. 2)Citation . JNK is down-regulated after hydroxyurea addition. All blots were stripped and reprobed with the respective antibodies recognizing ERK1, ERK2, JNK, and p38 proteins, demonstrating no changes in total MAP kinase expression. The same changes in phosphorylation patterns were observed in four experiments. Thus, hydroxyurea down-regulates ERK and JNK pathways and at the same time activates p38 in K562 cells. This modulation occurs well before measurable induction of hemoglobin synthesis occurs (Fig. 2)Citation .



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Fig. 2. Western blot analysis of the MAP kinase proteins ERK1/2, JNK, and p38 in hydroxyurea-treated K562 cells. Cells were treated with 400 µM hydroxyurea for the various times as indicated, harvested and lysed, and 20 µg of proteins were subjected to SDS-PAGE. After electroblotting, blots were incubated with specific antibodies against phosphorylated ERK1/2, JNK, and p38, respectively, and detected by chemiluminescence. Blots were stripped and reprobed with antibodies against ERK1, ERK2, JNK, and p38.

 
To investigate the relationship of ERK and p38 pathways, K562 cells were treated with p38 inhibitor SB203580 for 4 days, and ERK and JNK phosphorylation was observed by immunoblot analysis. Inhibition of p38 by SB203580 did not change ERK or JNK phosphorylation (Fig. 3)Citation . Thus, inhibition of p38 does not influence ERK signaling in K562 cells.



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Fig. 3. Western blot analysis of K562 cells treated with hydroxyurea (HU) in the presence of p38 inhibitor SB203580 (SB). Cells were cultured in the absence (control) or presence of hydroxyurea alone or with hydroxyurea plus SB203580 (SB+HU), harvested, and 20 µg of proteins were subjected to SDS-PAGE. After electroblotting, blots were incubated with specific antibodies against phosphorylated ERK1/2, JNK, and p38, respectively, and detected by chemiluminescence. Blots were stripped and reprobed with antibodies against ERK1, ERK2, JNK, and p38.

 
The Effect of Specific MAP Kinase Inhibitors on Hydroxyurea Action.
The Western blot experiments shown above suggested that inhibition of ERK/JNK and activation of p38 play a role in hydroxyurea-mediated erythroid differentiation of K562 cells. To prove this observation further, we next examined the effect of the specific ERK inhibitors PD98059 (21, 22, 23) and p38 inhibitor SB203580 (24, 25, 26) on hydroxyurea-induced erythroid differentiation. Cells were incubated with hydroxyurea in the presence or the absence of 10 µM SB203580 or 25 µM PD98059. Cellular differentiation was measured as described in "Materials and Methods." Fig. 4aCitation shows the percentage of benzidine-positive cells of hydroxyurea-treated K562 cells that were cultured in the presence of PD98059 and SB203580. PD98059 further increased benzidine positivity of hydroxyurea-treated K562 cells, whereas SB203580 inhibited induction of erythroid differentiation by hydroxyurea (Fig. 4a)Citation . We next investigated the influence of SB203580 on sodium butyrate-induced erythroid differentiation. As a result, we observed that SB203580 inhibited induction of erythroid differentiation by sodium butyrate (Fig. 4b)Citation . These data are similar to those of Witt et al. (27) . Thus, these results indicate that activation of p38 is essential for hydroxyurea-induced erythroid differentiation.



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Fig. 4. Effect of ERK inhibitor PD98059 and p38 inhibitor SB203580 on hydroxyurea-mediated erythroid differentiation of K562 cells. a, cells were cultured for 4 days in the absence (control) or presence of hydroxyurea alone (HU) or with hydroxyurea plus SB203580 (SB+HU) and PD98059 (PD+HU). Inhibitors were added 1 h before hydroxyurea. Hemoglobinization was determined by benzidine staining. Each experiment was performed four times and SEs were calculated as indicated. b, cells were cultured for 4 days in the absence (control) or presence of sodium butyrate alone (NaB) or with sodium butyrate plus SB203580 (SB+NaB) and PD98059 (PD+NaB). Inhibitor was added 1 h before sodium butyrate. Hemoglobinization was determined by benzidine staining. Each experiment was performed four times and SEs were calculated as indicated.

 

    Discussion
 TOP
 Abstract
 Introduction
 Results
 Discussion
 Materials and Methods
 References
 
Hydroxyurea treatment of K562 human erythroleukemia cells initiates a cascade of cellular events that profoundly influence the expression of a variety of genes and ultimately lead to cell differentiation. To date, there is little information on intracellular signaling of hydroxyurea-induced cellular differentiation. A recent report suggesting that butyrate-induced erythroid differentiation of K562 cells involves the inhibition of ERK and activation of p38 MAP kinase pathways (27) led us to explore the role of components of the ubiquitous MAP kinase signal transduction system in hydroxyurea-mediated induction of erythroid differentiation of K562 leukemia cells. In agreement with previously published data (27) , our data show that inhibition of ERK and activation of p38 signal transduction pathways play a critical role in hydroxyurea-induced erythroid differentiation. This is based on the following observations.

(a) Hydroxyurea causes dephosphorylation of ERK, dephosphorylation of JNK, and phosphorylation of p38 MAP kinases.

(b) Inhibition of ERK signaling by specific inhibitors induces hemoglobin synthesis and acts synergistically with hydroxyurea. Specific inhibition of p38 signaling inhibits hydroxyurea-mediated induction of hemoglobin production.

These data are similar to those of sodium butyrate-induced erythroid differentiation of K562 cells by Witt et al. (27) . The effect of hydroxyurea on cellular differentiation in K562 cells shares some similarities with that of sodium butyrate, although the action mechanism of hydroxyurea is different from that of sodium butyrate. Sodium butyrate is an inhibitor of histone deacetylase and also induces differentiation in a wide range of tumor cells in culture (28) . Involvement of signal transduction pathways in mediating butyrate effects on cells has been described recently. In murine erythroleukemia cells, butyrate causes sustained activation of JAK/STAT signaling (29) and inhibition of a serine-threonine-protein phosphatase is involved in butyrate-mediated differentiation of a hepatoma cell line (30) . In K562 cells, activation of ERK signaling by phorbol-ester leads to megakaryocytic differentiation in K562 cells, whereas inhibition of the ERK pathway enhances the erythroid phenotype (31 , 32) , consistent with our finding that ERK is down-regulated during hydroxyurea-induced erythroid differentiation.

ERK is rapidly activated by a variety of cell growth stimuli, and sustained activation eventually initiates cell proliferation and hallmarks of transformation (10 , 15 , 33 , 34) . Conversely, inhibition of ERK has been shown to inhibit cell growth and growth factor-stimulated gene transcription (35 , 36) . In PC12 rat pheochromocytoma cells, the duration of ERK activation seems to be critical for neuronal differentiation versus proliferation of cells (37 , 38) . Among ERK substrates are cytoskeletal elements and their phosphorylation by ERK seems to regulate cytoskeletal rearrangements and cellular morphology (39 , 40) . Furthermore, many of the cellular oncogenes involve mutations of receptor tyrosine kinases such as Src, Ras, Raf-1, and G proteins, leading to constitutive activation of the ERK pathway (10 , 41) . Thus, inhibition of ERK signaling by hydroxyurea might be an attractive explanation for the cellular differentiation after hydroxyurea treatment.

JNK and p38 kinase are primarily activated by various environmental stresses and have been suggested to play a critical role in apoptosis and cell growth (10 , 15) . It was recently reported that various hematopoietic cytokines, interleukins, and colony-stimulating factors, which regulate hematopoietic cell growth, survival, and differentiation, activate not only classical MAP kinase ERK, but also p38 and JNK (42, 43, 44, 45, 46) . Erythropoietin induces transient activation of all MAP kinase family, ERK, JNK, and p38 (43 , 44) , which, in turn, leads to erythroid differentiation. Actually, activation of p38 and JNK MAP kinase pathways have been shown to be essential for EPO-induced erythroid differentiation of mouse erythroleukemia cells (47) . Nagata et al. (48) reported that activation of p38 and JNK is required for environmental stress-induced erythroid differentiation of SKT6 cells. There are conflicting reports concerning the involvement of JNK in cellular differentiation (27 , 42 , 43 , 48) . We found that activation of p38 signaling is involved in the induction of hemoglobin synthesis, but the role of the observed changes in JNK MAP kinase activity by hydroxyurea remains to be clarified, because no specific inhibitor of this pathway is available.

It is intriguing to determine whether hydroxyurea similarly activates p38 kinase and inactivates ERK in other cell lines. Our colleagues examined the effect of hydroxyurea on activation of MAP kinase family in human diploid fibroblasts. As a result, hydroxyurea activated ERK but did not activate p38 kinase.4 This result is not similar to our result. Therefore, the effects of hydroxyurea cannot be generalized in any cell types. The present study suggests that hydroxyurea-induced erythroid differentiation of K562 cells requires the inhibition of ERK and the activation of p38 kinase. However, the mechanism for activation or inactivation of MAP kinases by hydroxyurea in K562 cells is not clear. Recently, it was suggested that hydroxyurea would be a nitric oxide generator via hydrogen peroxide-dependent peroxidation (49) . DNA single-strand breaks derived by the inhibition of ribonucleotide reductase or DNA damage induced by nitric oxide generated during hydrogen peroxide-dependent peroxidation of hydroxyurea might be responsible for the inhibition of ERK and the activation of p38 kinase by hydroxyurea in K562 cells. Additional speculation awaits the illustration of the molecular mechanisms by which hydroxyurea can inhibit ERK and activate p38 kinase in K562 cells. And also additional experiments will be required to identify the downstream signaling of hydroxyurea-induced erythroid differentiation of K562 cells.


    Materials and Methods
 TOP
 Abstract
 Introduction
 Results
 Discussion
 Materials and Methods
 References
 
Materials.
The following antibodies were purchased from Calbiochem, San Diego, CA: anti-ERK1/2 phosphorylated, anti-JNK1/2 phosphorylated, anti-ERK1, anti-ERK2, and anti-p38. Antibodies obtained from Sigma Chemical Co. (St. Louis, MO) were anti-p38 phosphorylated and anti-JNK1/2. The p38-specific inhibitor SB203580 and ERK1/2 specific inhibitor PD98059 were from Calbiochem.

Cell Culture.
The human leukemia cell line K562 was obtained from American Type Culture Collection (Philadelphia, PA) and maintained in RPMI 1640 (Life Technologies, Inc., Grand Island, NY) supplemented with 10% fetal bovine serum (Life Technologies, Inc.), 100 units/ml penicillin (Life Technologies, Inc.), and 100 µg/ml streptomycin (Life Technologies, Inc.) in a humidified 5% CO2 atmosphere at 37°C. For experiments, cells were seeded at 5 x105 cells/10 ml in 10-cm dishes (Nunc, Naperville, IL) and cultured for 4 days in the presence or absence of hydroxyurea or sodium butyrate as indicated. The following concentrations were used: 0.6 mM sodium butyrate (Sigma Chemical Co.), 200 or 400 µM hydroxyurea (Sigma Chemical Co.).

Benzidine Staining and Trypan Blue Exclusion.
The benzidine was prepared just before use by adding 5 µl of 30% hydrogen peroxide to 1 ml of a stock solution of 0.2% benzidine solution in 0.5% acetic acid. One ml of the staining solution was added to 1 ml of the cell suspension to be tested for hemoglobin content, and the reaction was allowed to proceed for 3–10 min at room temperature. The proportion of blue-purple stained hemoglobin-positive cells was quantified under light microscopy (10) . To evaluate the effect of ERK inhibitor PD98059 and p38 inhibitor SB203580 on hydroxyurea-mediated erythroid differentiation of K562 cells, cells were cultured for 4 days in the absence (control) or presence of hydroxyurea alone (HU) or with hydroxyurea plus PD98059 (PD+HU) and SB203580 (SB+HU). Inhibitors were added 1 h before hydroxyurea. Hemoglobinization was determined by benzidine staining.

One-fourth volume of trypan blue dye solution (0.4% w/v, Life Technologies, Inc.) was added to cell suspension, and the mixture was allowed to sit briefly at room temperature. Cells were scored for dye uptake under light microscope.

Analysis of MAP Kinase Family Proteins (ERK, JNK, p38) Phosphorylation in Hydroxyurea-Induced K562 Cells by Western Blotting Analysis.
K562 cells treated with or without 400 µM hydroxyurea for various times, as indicated, were lysed in lysis buffer [50 mM Tris (pH 7.4), 150 mM NaCl, 2 mM EDTA, 50 mM NaF, 0.2 mM sodium vanadate, 1% SDS, 1 mM PMSF, 1 µg/ml aprotinin, and 1 µg/ml leupeptin] by extensive vortexing. Samples were centrifuged at 13,000 x g for 10 min to remove cell debris. Total protein content was determined using Bio-Rad Protein Assay (Bio-Rad Laboratories, Hercules, CA). Laemmli sample buffer was added to lysates, which were resolved by 12% SDS-PAGE under reducing conditions. Twenty µg of the proteins were transferred to nitrocellulose membranes (Schleicher & Schuell, Keene, NH). Transfer of proteins was assessed by Ponceau red staining. Membranes were blocked in TBS-T buffer [10 mM Tris (pH 7.5), 100 mM NaCl, and 0.05% Tween 20] containing 5% nonfat dried skim milk for 1 h. The blots were incubated with the respective antiphosphorylated ERK1/2, JNK1/2, and p38 antibody (1 µg/ml) for 1 h, washed three times in TBS-T buffer, incubated for 1 h with goat-antirabbit peroxidase-conjugated antibody (Sigma Chemical Co.) in TBS-T buffer plus 5% nonfat dried milk, and washed three times in TBS-T buffer before detection with an enhanced chemiluminescence detection system (Amersham Pharmacia Biotech, Buckinghamshire, United Kingdom) according to the manufacturer’s instructions. Blots were stripped at 50°C for 30 min in 100 mM 2-mercaptoethanol, 2% SDS, 62.5 mM Tris-HCl (pH 6.7), and reprobed as indicated.


    Footnotes
 
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.

1 This work was supported by Grant HMP-98-M-3-0041 of the Korea Health 21 Research and Development Project, Ministry of Health and Welfare, Republic of Korea. Back

2 To whom requests for reprints should addressed, at Department of Biochemistry, Dong-A University College of Medicine, Dongdaesin-Dong 3 Ga 1, Seo-Gu, Busan 602-103, Korea. Phone: 82-51-240-2881; Fax: 82-51-241-6940; E-mail: jipark{at}daunet.donga.ac.kr Back

3 The abbreviations used are: MAP, mitogen-activated protein; ERK, extracellular signal-related kinase; JNK, c-Jun NH2-terminal kinase; p38, p38 MAP kinase; TBS-T, Tris-buffered saline containing Tween 20. Back

4 E. J. Yeo, unpublished data. Back

Received for publication 1/ 8/01. Revision received 6/28/01. Accepted for publication 7/ 2/01.


    References
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 Abstract
 Introduction
 Results
 Discussion
 Materials and Methods
 References
 

  1. Krakoff I. H., Brown N. C., Reichard P. Inhibition of ribonucleotide diphosphate reductase by hydroxyurea. Cancer Res., 28: 1559-1565, 1968.[Abstract/Free Full Text]
  2. Alter B. P., Gilbert H. S. The effect of hydroxyurea on hemoglobin F in patients with myeloproliferative syndromes. Blood, 66: 373-379, 1985.[Abstract/Free Full Text]
  3. Cortelazzo S., Finazzi G., Ruggeri M., Vestri O., Galli M., Rodeghiero F., Barbui T. Hydroxyurea for patients with essential thrombocythemia and a high risk of thrombosis. N. Engl. J. Med., 332: 1132-1136, 1995.[Medline]
  4. Najean Y., Rain J. D. Treatment of polycythemia vera: the use of hydroxyurea and pipobroman in 292 patients under the age of 65 years. Blood, 90: 3370-3377, 1997.[Abstract/Free Full Text]
  5. Steinberg M. H., Nagel R. L., Brugnara C. Cellular effects of hydroxyurea in Hb SC disease. Br. J. Haematol., 98: 838-844, 1997.[Medline]
  6. Charache S., Terrin M. L., Moore R. D., Dover G. J., Barton F. B., Eckert S. V., McMahon R. P., Bonds D. R. Effect of hydroxyurea on the frequency of painful crises in sickle cell anemia. Investigators of the Multicenter Study of Hydroxyurea in Sickle Cell Anemia. N. Engl. J. Med., 332: 1317-1322, 1995.[Medline]
  7. Adunyah S. E., Chander R., Barner V. K., Copper R. S. Regulation of c-jun mRNA expression by hydroxyurea in human K562 cells during erythroid differentiation. Biochim. Biophys. Acta., 1263: 123-132, 1995.[Medline]
  8. Mata F., Rius C., Cabanas C., Bernabeu C., Aller P. S-phase inhibitors induce vimentin expression in human promonocytic U-937 cells. FEBS Lett., 259: 171-174, 1989.[Medline]
  9. Boulton T. G., Nye S. H., Robbins D. J., Ip N. Y., Radziejewska E., Morgenbesser S. D., DePinho R. A., Panayotatos N., Cobb M. H., Yancopoulos G. D. ERKs: a family of protein-serine/threonine kinases that are activated and tyrosine phosphorylated in response to insulin and NGF. Cell, 65: 663-675, 1991.[Medline]
  10. Seger R., Krebs E. G. The MAPK signaling cascade. FASEB J., 9: 726-735, 1995.[Abstract]
  11. Minden A., Karin M. Regulation and function of the JNK subgroup of MAP kinases. Biochim. Biophys. Acta, 1333: F85-F104, 1997.[Medline]
  12. Ichijo H. From receptors to stress-activated MAP kinases. Oncogene, 18: 6087-6093, 1999.[Medline]
  13. Zhou G., Bao Z. Q., Dixon J. E. Components of a new human protein kinase signal transduction pathway. J. Biol. Chem., 270: 12665-12669, 1995.[Abstract/Free Full Text]
  14. Cano E., Mahadevan L. C. Parallel signal processing among mammalian MAPKs. Trends Biochem. Sci., 20: 117-122, 1995.[Medline]
  15. Lewis T. S., Shapiro P. S., Ahn N. G. Signal transduction through MAP kinase cascades. Adv. Cancer Res., 74: 49-139, 1998.[Medline]
  16. Rowley R. T., Ohlsson-Wilhelm B. M., Farley B. A. K562 human erythroleukemia cells demonstrate commitment. Blood, 65: 862-868, 1985.[Abstract/Free Full Text]
  17. Ishiguro K., Sartorelli A. C. The response of IL-3 dependent B6UtA bone marrow cells to both erythropoietin and chemical inducers of differentiation. Cancer Lett., 110: 233-241, 1996.[Medline]
  18. Payne D. M., Rossomando A. J., Martino P., Erickson A. K., Her J. H., Shabanowitz J., Hunt D. F., Weber M. J., Sturgill T. W. Identification of the regulatory phosphorylation sites in pp42/mitogen-activated protein kinase (MAP kinase). EMBO J., 10: 885-892, 1991.[Medline]
  19. Derijard B., Hibi M., Wu I. H., Barret T., Su B., Deng T., Karin M., Davis R. J. JNK1: a protein kinase stimulated by UV light and Ha-Ras that binds and phosphorylates the c-Jun activation domain. Cell, 76: 1025-1037, 1994.[Medline]
  20. Han J., Lee J. D., Bibbs L., Ulevitch R. J. A MAP kinase targeted by endotoxin and hyperosmolarity in mammalian cells. Science (Wash. DC), 265: 808-811, 1994.[Abstract/Free Full Text]
  21. Favata M. F., Horiuchi K. Y., Manos E. J., Daulerio A. J., Stradley D. A., Feeser W. S., Van Dyk D. E., Pitts W. J., Earl R. A., Hobbs F., Copeland R. A., Magolda R. L., Scherle P. A., Trzaskos J. M. Identification of a novel inhibitor of mitogen activated protein kinase kinase. J. Biol. Chem., 273: 18623-18632, 1998.[Abstract/Free Full Text]
  22. Desilva D. R., Jones E. A., Favata M. F., Jaffee B. D., Magolda R. L., Trzaskos J. M., Scherle P. A. Inhibition of mitogen-activated protein kinase kinase blocks T cell proliferation but does not induce or prevent anergy. J. Immunol., 160: 4175-4181, 1998.[Abstract/Free Full Text]
  23. Dudley D. T., Pang L., Decker S. J., Bridges A. J., Saltiel A. R. A synthetic inhibitor of the mitogen-activated protein kinase cascade. Proc. Natl. Acad. Sci. USA, 92: 7686-7689, 1995.[Abstract/Free Full Text]
  24. Cuenda A., Rouse J., Doza Y. N., Meier R., Cohen P., Gallagher T. F., Young P. R., Lee J. C. SB203580 is a specific inhibitor of a MAP kinase homologue which is stimulated by cellular stresses and interleukin-1. FEBS Lett., 364: 229-233, 1995.[Medline]
  25. Lee J. C., Laydon J. T., McDonnell P. C., Gallagher T. F., Kumar S., Green D., McNulty D., Blumenthal M. J., Heys J. R., Landvatter S. W., Strickler J. E., McLaughlin M. M., Siemens I. R., Fisher S. M., Livi G. P., White J. R., Adams J. L., Young P. R. A protein kinase involved in the regulation of inflammatory cytokine biosynthesis. Nature (Lond.), 372: 739-746, 1994.[Medline]
  26. Badger A. M., Bradbeer J. N., Votta B., Lee J. C., Adams J. L., Griswold D. E. Pharmacological profile of SB203580, a selective inhibitor of cytokine suppressive binding protein/p38 kinase, in animal models of arthritis, bone resorption, endotoxin shock and immune function. J. Pharmacol. Exp. Ther., 279: 1453-1461, 1996.[Abstract/Free Full Text]
  27. Witt O., Sand K., Pekrun A. Butyrate-induced erythroid differentiation of human K562 leukemia cells involves inhibition of ERK and activation of p38 MAP kinase pathways. Blood, 95: 2391-2396, 2000.[Abstract/Free Full Text]
  28. Kruh J. Effects of sodium butyrate, a new pharmacological agent, on cells in culture. Mol. Cell. Biochem., 42: 65-82, 1982.[Medline]
  29. Yamashita T., Wakao H., Miyajima A., Asano S. Differentiation inducers modulate cytokine signaling pathways in a murine erythroleukemia cell line. Cancer Res., 58: 556-561, 1998.[Abstract/Free Full Text]
  30. Cuisset L., Tichonicky L., Jaffray P., Delpech M. The effects of sodium butyrate on transcription are mediated through activation of a protein phosphatase. J. Biol. Chem., 272: 24148-24153, 1997.[Abstract/Free Full Text]
  31. Shelly C., Petruzzelli L., Herrera R. PMA-induced phenotypic changes in K562 cells: MAPK-dependent and -independent events. Leukemia, 12: 1951-1961, 1998.[Medline]
  32. Whalen A. M., Galasinski S. C., Shapiro P. S., Nahreini T. S., Ahn N. G. Megakaryocytic differentiation induced by constitutive activation of mitogen-activated protein kinase kinase. Mol. Cell Biol., 17: 1947-1958, 1997.[Abstract/Free Full Text]
  33. Mansour S. J., Matten W. T., Hermann A. S., Candia J. M., Rong S., Fukasawa K., Vande Woude G. F., Ahn N. G. Transformation of mammalian cells by constitutively active MAP kinase kinase. Science (Wash. DC), 265: 966-970, 1994.[Abstract/Free Full Text]
  34. Brunet A., Pages G., Pouysseger J. Constitutively active mutants of MAP kinase kinase (MEK1) induce growth factor-relaxation and oncogenecity when expressed in fibroblasts. Oncogene, 9: 3379-3387, 1994.[Medline]
  35. Kortenjann M., Thomae O., Shaw P. E. Inhibition of v-raf-dependent c-fos expression and transformation by a kinase-defective mutant of the mitogen-activated protein kinase Erk2. Mol. Cell. Biol., 14: 4815-4824, 1994.[Abstract/Free Full Text]
  36. Pages G., Lenormand P., L’Allemain G., Chambard J. C., Meloche S., Pouyssegur J. Mitogen-activated protein kinases p42mapk and p44mapk are required for fibroblast proliferation. Proc. Natl. Acad. Sci. USA, 90: 8319-8323, 1993.[Abstract/Free Full Text]
  37. Marshall C. J. Specificity of receptor tyrosine kinase signaling: transient versus sustained extracellular signal-regulated kinase activation. Cell, 80: 179-185, 1995.[Medline]
  38. Cowley S., Paterson H., Kemp P., Marshall C. J. Activation of MAP kinase kinase is necessary and sufficient for PC12 differentiation and for transformation of NIH3T3 cells. Cell, 77: 841-852, 1994.[Medline]
  39. Minshull J., Sun H., Tonks N. K., Murray A. W. A MAP kinase-dependent spindle assembly checkpoint in Xenopus egg extracts. Cell, 79: 475-486, 1994.[Medline]
  40. Ray L. B., Sturgill T. W. Rapid stimulation by insulin of a serine/threonine kinase in 3T3–L1 adipocytes that phosphorylates microtubule-associated protein 2 in vitro. Proc. Natl. Acad. Sci. USA, 84: 1502-1506, 1987.[Abstract/Free Full Text]
  41. Bishop J. M. Molecular themes in oncogenesis. Cell, 64: 235-248, 1991.[Medline]
  42. Rausch O., Marshall C. J. Tyrosine 763 of the murine granulocyte colony-stimulating factor receptor mediates Ras-dependent activation of the JNK/SAPK mitogen-activated protein kinase pathway. Mol. Cell. Biol., 17: 1170-1179, 1997.[Abstract/Free Full Text]
  43. Nagata Y., Nishida E., Todokoro K. Activation of JNK signaling pathway by erythropoietin, thrombopoietin, and interleukin-3. Blood, 89: 2664-2669, 1997.[Abstract/Free Full Text]
  44. Nagata Y., Moriguchi T., Nishida E., Todokoro K. Activation of p38 MAP kinase pathway by erythropoietin and interleukin-3. Blood, 90: 929-934, 1997.[Abstract/Free Full Text]
  45. Foltz I. N., Schrader J. W. Activation of the stress-activated protein kinases by multiple hematopoietic growth factors with the exception of interleukin-4. Blood, 89: 3092-3096, 1997.[Abstract/Free Full Text]
  46. Foltz I. N., Lee J. C., Young P. R., Schrader J. W. Hemopoietic growth factors with the exception of interleukin-4 activate the p38 mitogen-activated protein kinase pathway. J. Biol. Chem., 272: 3296-3301, 1997.[Abstract/Free Full Text]
  47. Nagata Y., Takahashi N., Davis R. J., Todokoro K. Activation of p38 MAP kinase and JNK but not ERK is required for erythropoietin-induced erythroid differentiation. Blood, 92: 1859-1869, 1998.[Abstract/Free Full Text]
  48. Nagata Y., Todokoro K. Requirement of activation of JNK and p38 for environmental stress-induced erythroid differentiation and apoptosis and of inhibition of ERK for apoptosis. Blood, 94: 853-863, 1999.[Abstract/Free Full Text]
  49. Sato K., Akaike T., Sawa T., Miyamoto Y., Suga M., Ando M., Maeda H. Nitric oxide generation from hydroxyurea via copper-catalyzed peroxidation and implications for pharmacological actions of hydroxyurea. Jpn. J. Cancer Res., 88: 1199-1204, 1997.[Medline]



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