三氧化二砷是全球性環境毒物之一。根據流行病學研究顯示，長時間飲用三氧化二砷含量偏高飲用水造成慢性三氧化二砷暴露與烏腳病、膀胱癌或心血管粥狀硬化的發生有很大相關性。相反地，以三氧化二砷為治療藥物的藥用歷史已經超過2400年，特別是用於治療急性前髓性細胞白血病病人相當有效。近年研究報告指出：三氧化二砷誘導白血病細胞的細胞周期停滯或走向細胞凋亡，形成抗白血病效應。然而，三氧化二砷對細胞的精準作用機轉目前尚未清楚被架構出來。抑癌因子p21WAF1/ CIP1 (p21)是第一個被發現的細胞周期把關者。當細胞受到外界壓力刺激時，p21會被活化進而阻斷細胞周期進行，避免細胞受到傷害。為了探討三氧化二砷誘導p21活化的訊息傳遞路徑，我們以人類上皮癌A431細胞株為細胞模式，進行各項實驗。首先，不論蛋白質或是啟動子，三氧化二砷誘導的p21表現皆呈時間相關或劑量相關上升。接著，利用MAPK家族各訊息傳遞路徑的專一性抑制劑初步篩選參與三氧化二砷誘導p21活化的訊息傳遞路徑，發現：只有ERK1/2路徑的抑制劑－PD98059可以有效地抑制三氧化二砷對p21的活化表現。為了更進一步確認ERK1/2路徑的確參與三氧化二砷誘導p21表現的訊息傳遞路徑，我們利用ERK1/2路徑上游訊息因子－Ras、Raf證明之。分別同時轉殖感染全長p21-luc與持續表現Ras的質體－pSV2-ras，Ras dominant negative mutant質體－pMM-rasDN與Raf dominant negative mutant質體－Raf-C4B質體進入A431細胞株，觀察p21報告基因活性變化情形，發覺：Ras與Raf 確實都參與三氧化二砷活化的ERK1/2訊息傳遞路徑。另一方面，JNK路徑的抑制劑－SP600125與p38路徑的抑制劑－SB203580反而會促進三氧化二砷對p21的活化作用。由西方點墨法實驗證明：EGFR活性抑制劑－PD153035、AG1478可以抑制三氧化二砷誘導MAPK家族各訊息傳遞路徑活化與p21活化。利用不同抗氧化劑進行西方點墨法與reporter assay實驗皆證實：三氧化二砷誘導p21活化的過程中需要ROS現象形成。過去，我們實驗室利用5’-deletion analysis與site-direct mutation analysis兩種實驗方法證明－p21啟動子上-93 bp到+1 bp這段區域對三氧化二砷活化p21啟動子活性是必須的。為了了解是否三氧化二砷活化的EGFR-Ras-ERK1/2訊息傳遞路徑與ROS現象也是透過這段區域調控p21啟動子表現，外送只含p21啟動子上-93 bp到+1 bp這段區域的p93S質體進入A431細胞株，觀察細胞受到三氧化二砷刺激後，p21啟動子活性的變化情形。實驗結果證明－三氧化二砷活化的EGFR-Ras-ERK1/2訊息傳遞路徑與ROS現象的確是透過這段區域調控p21啟動子表現。然而，三氧化二砷誘導p21表現的生理意義為何呢？由DN片段分析結果得知：在我們的系統裡，三氧化二砷誘導p21表現的訊息傳遞路徑與細胞凋亡的訊息傳遞路徑是兩件獨立事件。從西方點墨法實驗結果發現：三氧化二砷誘導p21表現後，可能會造成細胞周期停滯於G1/S。綜合上述實驗結果，我們以A431細胞株為細胞模式，提出一個可能的訊息傳遞路徑：細胞受到三氧化二砷刺激後，透過EGFR活化下游Ras-ERK1/2路徑，進而作用到p21啟動子上-93bp區域，調控p21表現，造成細胞周期停滯於G1/S；整個訊息傳遞過程中，ROS現象的形成扮演不可或缺角色。

Arsenic trioxide (As2O3；arsenite) is one of the global environment toxicants. Chronic exposure to arsenite, as a result of a long-term ingestion of drinking water with a high concentration of arsenite, has been related to the etiology of Blackfoot disease, bladder cancer and atherosclerosis. In contrast, arsenite has been used as a therapeutic agent for more than 2400 years, effectively in treating acute promyelocytic leukemia (APL) patients. Recent studies have proved that the anti-leukemic effect of arsenite lies in its ability to induce cell cycle arrest or apoptosis. However, the precise mechanism of arsenite-induced effects is still unclear. p21WAF1/ CIP1 (p21) is the first identified cell cycle checkpoint and blocks cell cycle progression in response to extracellular stress. To investigate the signal transduction of arsenite-induced p21 activation, we performed several studies in human epidermoid carcinoma A431 cells. In the present study, we found that arsenite induced upregulation of promoter and protein expression of p21 in dose- and time-dependent manners. Then, we used MAPK inhibitors to address which pathway was involved in arsenite-induced p21 activation. Our preliminary results showed that only PD98059, an inhibitor of MEK, could inhibit arsenite-induced p21 induction. To further clarify the ERK1/2 pathway involved in the signal transduction of arsenite-induced p21 activation, we transfected respectively pSV2-ras, pMM-rasDN, Raf-C4B plasmids into A431 cells to address this question. The reporter assay showed that both Ras and Raf proteins were involved in the arsenite-induced ERK1/2 pathway. On the contrary, both JNK inhibitor, SP600125, and p38 inhibitor, SB203580, could enhance arsenite- induced p21 expression. In immunoblot analysis, pretreatment of PD153035 or AG1478, the specific inhibitors of EGFR tyrosine kinase, could inhibit arsenite- induced both MAPK phosphorylation and p21 activation. Several antioxidants (e.g. NAC, DPI, GSH) could inhibit arsenite-induced p21 activation from both immunoblot analysis and reporter assay. In our previous results, we proved that the region between –93 and +1 bp of p21 promoter played an essential role in arsenite-induced p21 activation by using 5’-deletion analysis and site-direct mutation analysis. To make sure whether this region was important for arsenite inducing EGRF-Ras-ERK1/2 pathway, ROS formation and p21activation, we transfected p93S plasmid instead of total length p21-luc plasmid to find out the answer. In the present results, we found out the region between –93 and +1 bp of p21 promoter was involved in the arsenite-induced signaling pathway. In our preliminary results, we didn’t find the correlation between arsenite-induced p21 activation and cell apoptosis by using DNA fragmentation analysis. To sum up, we suggest EGFR-Ras-ERK1/2 pathway and ROS formation were involved in the arsenite-induced p21 activation. The region between –93 and +1 bp located in the p21 promoter was the functional region of the effect of arsenite.

Aposhian HV., Zakharyan RA., Wildfang EK., Healy SM., Gailer J., Radabaugh TR., Bogdan GM., Powell LA., Aposhian MM. How is inorganic arsenic detoxified? In Arsenic exposure and health effects, eds. Chapell WR., Abernathy CO., Calderon RL. pp. 289-297, 1999

Arbabi S., Maier RV. Mitogen-activated protein kinases. Crit. Care Med. 30: S74-S79, 2002

Aronson SM. Arsenic and old myths. RI Med. 77: 233-234, 1994

Asada M., Yamada T., Ichijo H., Delia D., Miyazono K., Fukumuro K., Mizutan S. Apoptosis inhibitory activity of cytoplasmic p21WAF1/CIP1 in monocytic differentiation. EMBO J. 18(5): 1223-1234, 1999

Bae YS., Kang SW., Seo MS., Baines IC., Tekle E., Chock PB., Rhee SG. Epidermal growth factor (EGF)-induced generation of hydrogen peroxide. J. Biol. Chem. 272: 217-221, 1997

Barchowsky A., Roussel RR., Klei LR., James PE., Ganju N., Smith KR., Dudek EJ. Low levels of arsenic trioxide stimulate proliferative signals in primary vascular cells without activating stress effector pathways. Toxicol. Appl. Pharmacol. 159: 65-75, 1999

Bernstam L., Nriagu J. Molecular aspects of arsenic stress. J. Toxicol. Environ. Health 3: 293-322, 2000

Biggs JR, Kudlow JE., Kraft AS. The role of the transcription factor Sp1 in regulating the expression of the WAF1/CIP1 gene in U397 leukemic cells. J. Biol. Chem. 271: 901-906, 1996

Borrow J., Goddard AD., Sheer D., Solomon E. Molecular analysis of acute promyelocytic leukemia breakpoint cluster region on chromosome 17. Science 249: 1577-1580, 1990

Brugarolas J., Chadrasekaran C., Gordon J., Beach D., Jacks T., Hannon G. Radiation-induced cell cycle arrest compromised by p21 deficiency. Nature 377: 552-557, 1995

Chang FL., Lai MD. The relationship between p53 status and anticancer drugs-induced apoptosis in nine human bladder cancer cell lines. Anticancer Res. 20: 351-355, 2000

Chen F., Lu Y., Zhang Z., Vallyathan V., Ding M., Castranova V., Shi X. Opposite effects of NFkB and c-Jun N-terminal kinase on p53-independent GADD45 induction by arsenite. J. Biol. Chem. 276: 11414–11419, 2001

Chen GQ., Zhu J., Shi XG., Ni, JH., Zhong HJ., Si GY., Jin XL., Tang W., Li XS., Xong SM., Shen ZX., Sun GL., Ma J., Zhang P., Zhang TD., Gazin C., Naoe T., Chen SJ., Wang ZY., Chen Z. In vitro studies on cellular and molecular mechanisms of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia: As2O3
induces NB4 cell apoptosis with downregulation of Bcl-2 expression and modulation of PML-RARa/PML proteins. Blood 88: 1052–1061, 1996

Chen J., Jackson PK., Kirschner MW., Dutta A. Separate domain of p21 involved in the inhibition of Cdk kinase and PCNA. Nature 374: 386-388, 1995

Chen NY., Ma WY., Huang C., Ding M., Dong Z. Activation of PKC is required for arsenite-induced signal transduction. J. Environ. Pathol. Toxicol. Oncol. 21: 297-305, 2000

Chen W., Martindale JL., Holbrook NJ., Liu Y. Tumor promoter arsenite activates extracellular signal-regulated kinase through a signaling pathway mediated by epidermal growth factor receptor and Shc. Mol. Cell. Biol. 18(9): 5178-5188, 1998

Chen YC., Lin-Shiau SY., Lin JK. Involvement of reactive oxygen species and caspase 3 activation in arsenite-induced apoptosis. J. Cell. Physiol. 177: 324-333, 1998

Chrysogelos SA., Dickson RB. EGF receptor expression, regulation, and function in breast cancer. Breast Cancer Res. Treat. 29: 29-40, 1994

Clement A., Henrion-Caude A., Besnard V., Corroyer S. Role of cyclins in epithelial
response to oxidants. Am. J. Respir. Crit Care Med. 164: 581-584, 2001

Coleman ML., Marshall CJ., Olson MF. Ras promotes p21WAF1/CIP1 protein stability via
a cyclin D1-imposed block in proteasome-mediated degradation. EMBO J. 22(9): 2036-2046, 2003

Coqueret O., Gascan H. Functional interaction of STAT3 transcription factor with the cell cycle inhibitor p21WAF1/CIP1. J. Biol. Chem. 275: 18794-18800, 2000

Cross AR. Inhibitors of the leukocyte superoxide generating oxidase: Mechanisms of action and methods for their elucidation. Free Radic. Biol. Med. 8: 71-93, 1990

Czajkowski R., Drewa T., Wozniak A., Krzyzynska-Malinowaka E. Cell cycle in sporadic melanoma. Int. J. Dermatol. 41: 550-556, 2002

Dai J., Weinberg RS., Waxman S. Malignant cells can be sensitized to undergo growth inhibition and apoptosis by arsenic trioxide through modulation of the glutathione redox system. Blood 93: 268-277, 1999

de The´ H., Chomienne C., Lanotte M., Degos L., Dejean A. The t(15;17) translocation of acute promyelocytic leukaemia fuses the retinoic acid receptor a gene to a novel transcribed locus. Nature 347: 558–561, 1990

Deneke SM. Induction of Cysteine transport in bovine pulmonary artery endothelial cells by sodium arsenite. Biochim. Biophys. Acta 1109: 127–131, 1992

Dong JT., Luo XM. Arsenic-induced DNA-strand breaks associated with DNA-protein crosslinks in human fetal lung fibroblasts. Mutat Res. 302: 97-102, 1993

Dong Z. The molecular mechanisms of arsenic-induced transformation and apoptosis. Environ. Health Perspect. 110(Suppl 5): 757- 759, 2002

Dotto GP. Signal transduction pathways controlling the switch between keratinocyte growth and differentiation. Crit. Rev. Oral. Biol. Med. 10(4): 442-457, 1999

Dotto GP. p21WAF1/CIP1: more than a break to the cell cycle? Biochem. Biophys. Acta. 1471: M43- M56, 2000

Downward J., Yarden Y., Mayes E., Scrace G., Totty N., Stockwell P., Ullrich A. Schlessinger J., Waterfield MD. Close similarity of epidermal growth factor receptor and v-erb-B oncogene protein sequences. Nature 307: 521-527, 1984

El Deiry WS., Tokino T., Velculescu VE., Levy DB., Parsons R., Trent JM., Lin D., Mercer WE., Kinzler KW., Vogelstein B. WAF1, a potential mediator of p53 tumor suppression. Cell 75: 817-825, 1993

Fan M., Chambers TC. Role of mitogen-activated protein kinases in the response of tumor cells to chemotherapy. Drug Resistance Updates 5: 253-267, 2001

Fotedar R., Brickner H., Saadatmandi H., Rousselle T., Diederich L., Munshi A. Jung
B., Reed JC., Fotedar A. Effect of p21WAF1/CIP1 transgene on radiation induced apoptosis in T cells. Oncogene 18: 3652-3658, 1999

Gartel AL., Serfas MS., Tyner AL. p21-Negative regulator of the cell cycle. Exp. Biol. Med. 213: 138-149, 1996

Gartel AL., Tyner AL. Transcriptional regulation of the p21WAF1/CIP1 gene. Exp. Cell Res. 246: 280-289, 1999

Gartel AL., Tyner AL. The role of the cyclin-dependent kinase inhibitor p21 in apoptosis. Mol. Cancer Ther. 1: 639-649, 2002

Gebel T. Confounding variables in the environmental toxicology of arsenic. Toxicol.
144: 155- 162, 2002

Germolec DR., Spalding J., Boorman GA., Wilmer JL., Yoshida T., Simeonova PP., Bruccoleri A., Kayama F., Gaido K., Tennant R., Burleson F., Dong W., Lang RW., Luster MI. Arsenic can mediate skin neoplasia by chronic stimulation of
keratinocytes-derived growth factors. Mutat. Res. 386: 209-218, 1997

Germolec DR., Yoshida T., Gaido K., Wilmer JL., Simeonova PP., Kayama F., Burleson F., Dong W., Lange RW., Luster MI. Arsenic induces overexpression of growth factors in human keratinocytes. Toxicol. Appl. Pharmacol. 141: 308-318, 1996

Gu Y., Turck CW., Morgan DO. Inhibition of CDK2 activity in vivo by an associated 20K regulatory subunit. Nature 366: 707- 710, 1993

Gulli LF., Palmer KC., Chen YQ., Reddy KB. Epidermal growth factor-induced apoptosis in A431 cells can be reversed by reducing the tyrosine kinase activity. Cell Growth Diff. 7: 137-178, 1996

Gullick WJ. Prevalence of aberrant expression of the epidermal growth factor receptor in human cancers. Br. Med. Bull. 47: 87-98, 1991

Gurr JR., Bau DT., Liu F., Lynn S., Jan KY. Dithiothreitol enhances arsenic trioxide-induced apoptosis in NB4 cells. Mol. Pharmacol 115: 102- 109, 1999

Gusterson BA. Identification and interpretation of epidermal growth factor and c-erbB-2 overexpression. Eur. J. Cancer 28: 263-267, 1992

Harper JW., Adami GR., Wei N., Keyomarsi K., Elledge SJ. The p21 Cdk-interacting protein Cip1 is a potent inhibitor of G1 cyclin-dependent kinases. Cell 75: 805-816, 1993

Harper JW., Elledge SJ., Keyomarsi K., Dynlacht B., Tsai LH., Zhang P., Dobrowolski S., Bai C., Connell-Crowley L., Swindell E. Inhibition of cyclin-dependent kinases by p21. Mol. Cell. Biol. 6: 287-400, 1995

Hei TK., Liu SX., Waldren C. Mutagenicity of arsenic in mammalian cells: Role of reactive oxygen species. Proc, Natl. Acad. Sci. USA 95: 8103-8107, 1998

Huang HS., Chang WC., Chen CJ. Involvement of reactive oxygen species in arsenite-induced downregulation of phospholipid hydroperoxide glutathione peroxidase in human epidermoid carcinoma A431 cells. Free Radic. Biol. Med. 34(6): 864-873, 2002

Huang SY., Chang CS., Tang JL., Tien HF., Kuo TL., Huang SF., Yao WC., Chung CY., Wang CH., Shen MC., Chen YC. Acute and chronic arsenic poisoning associated with treatment in acute promyelocytic leukemia. Br. J. Haematol. 103: 1092-1099, 1996

Hughes MF. Arsenic toxicity and potential mechanisms of action. Toxicol. Lett. 133:1-16, 2002

International Agency for Research on Cancer. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man: Metals and Metallic Compounds 23: 39-141, 1980

Irani K. Oxidant signaling in vascular cell growth , death, and survival: a review of the
roles of reactive species in smooth muscle and endothelial cell mitogenic and apoptotic signaling. Circ. Res. 87: 179-183, 2000

Jiang H., Lin J., Su ZZ., Herlyn M., Kerbel RS., Weissman BE. The melanoma differentiating-associated gene mda-6, which encodes the cyclin-dependent kinase inhibitor p21, differentially expressed during growth, differentiation and proliferation in human melanoma cells. Oncogene 10: 1855-1864, 1995

Jing Y., Wang R., Xia L. Comined effect of all-trans retinoic acid and arsenic trioxide in
acute promyelocytic leukemia cells in vitro and in vivo. Blood 97: 264-269, 2001

Johnson M., Dimitrov D., Vojta P., Barrett J., Noda A., Pereira-Smith A., Smith J. Evidence for a p53-independent pathway for upregulation of SDI1/CIP1/WAF1/p21 RNA in human cells. Mol. Carcinog. 11: 59-64. 1994

Jta AN., Nodti M., Nilsson R., Natarajan AT. Genotoxic effects of sodium arsenite on human cells. Mutat. Res. 284: 215-221. 1992

Kang KH., Kim WH., Choi KH. p21 promotes ceramide-induced apoptosis and antagonizes the anti-death effect of Bcl-2 in human hepatocarcinoma cells. Exp. Cell Res.253: 403-412, 1999

Kapahi P., Takahashi T., Natoli G., Adams SR., Chen Y., Tsien RY., Karin M. Inhibition of NFkB activation by arsenite through reaction with a critical cysteine in the activation loop of IkB kinase. J. Biol. Chem. 383: 36062-36066, 2000

Kardassis D., Papakosta P., Pardali K., Moustakas A. c-Jun transactivates the promoter
of the human p21WAF1/CIP1 gene by acting as a superactivator of the ubiquitous transcription factor Sp1. J. Biol, Chem. 274(41): 29572-29581, 1999

Kato J., Matsuoka M., Strom D., Sherr C. Regulation of cyclin D-dependent kinase 4 (cdk4) by cdk4-activating kinase. Mol. Cell Biol. 14: 2713-2721, 1994

Kayajanian GM. Arsenic, Dioxin, and promotional step in cancer creation. Ecotoxicol. Environ. Saf. 45: 195-197, 2000

Kim GY., Mercer SE., Ewton DZ., Yan Z., Jin K., Friedman E. The stress-activated protein kinase p38a and JNK1 stabilize p21WAF1/CIP1 by phosphorylation. J. Biol. Chem. 277: 29792-29802, 2002

Kim KY., Rhim TY., Choi I., Kim SS. N-Aetylcysteine induces cell cycle arrest in hepatic stellate cells through its reducing activity. J. Biol. Chem. 276: 40591-40598,
2001

Kitaura H., Shinshi M., Uchikoshi Y., Ono T., Iguchi-Ariga SM., Ariga H. Reciprocal regulation via protein-protein interaction between c-Myc and p21WAF1/CIP1 in DNA replication and transcription. J. Biol. Chem. 275: 10477-10483, 2000

Klaassen CD. Heavy metals and heavy-metal antagonists. In: Hardman JG., Gilman AG., Limbird LE., eds. Goodman & Gilman’s The Pharmacological Basis of Therapeutics. pp. 1649-1672, New York: McGraw-Hill, 1996

Kochhar TS., Howard W., Hoffman S., Brammer-Carleton L. Effect of trivalent and pentavalent arsenic in causing chromosome alterations in cultured Chinese hamster ovary (CHO) cells. Toxicol. Lett. 84: 37-42, 1996

Kojima S., Nomura T., Icho T., Kahiwara Y., Kitabatake K., Kufbota K. Inhibitory effect of neopterin on NADPH-dependent superoxide- generating oxidase of rat peritoneal macrophages. FEBS Lett. 329: 125-128, 1993

Konkola K. More than a coincidence? The arrival of arsenic and the disappearance of plaque in early modern Europe. J. Hist. Med. Allied. Sci. 47: 186-209, 1992

Kwok TT., Mok CH., Menton-Brennan L. Upregulation of a mutant form of p53 by doxorubicin in human squamous carcinoma cells. Cancer Res. 54: 2834-2835, 1994

Kwong YL., Todd D. Delicious poison: arsenic trioxide for the treatment of leukemia [letter]. Blood 89: 3487-3488, 1997

LaBaer J., Garrett MD., Stevenson LF., Slingerland JM., Sandhu C., Chou HS., Fattaey
A., Harlow E. New functional activities for the p21 family of CDK inhibitors. Genes.
Dev. 11: 847-862, 1997

Larramendy ML., Popescu NC., Dipaolo JA. Induction by inorganic metal salts of sister
chromatid exchanges and chromosome aberrations in human and Syrian hamster cell strains Environ. Mutagen. 3: 597-606, 1981

Lee TC., Ho IC. Differential cytotoxic effects of arsenic on human and animal cells. Environ. Health Perspect 3: 101-105, 1994

Lee TC., Oshimura M., Barrett JC. Comparison of arsenic-induced cell transformation, cytotoxicity, mutation and cytogenetic effects in Syrian hamster embryo cells in culture. Carcinogenesis 6: 1421-1426, 1985.

Lee TC., Tanaka N., Lamb PW., Gilmer TM., Barrett JC. Induction of gene amplification by arsenic. Science 241: 79-81, 1988.

Li M., Cai JF., Chiu JF. Arsenic induces oxidative stress and activate stress gene
expressions in cultured lung epithelial cells. J. Cell. Biochem. 87: 29-38, 2002

Luch A. Cell cycle control and cell division: implications for chemically induced carcinogenesis. ChemBiochem. 3: 506-516, 2002

Macip S., Igarashi M., Fang L., Chen A., Pan ZQ., Lee SW., Aaronson SA. Inhibition of p21-mediated ROS accumulation can rescue p21-induced senescence. EMBO J. 21(9): 2180-2188, 2002

Maher PA. Disruption of cell-substrate adhesion activates the protein tyrosine kinase pp60c-src. Exp. Cell Res. 250: 189-198, 2000

Mass MJ., Wang L. Arsenic alters cytosine methylation patterns of the promoter of the tumor suppressor gene p53 in human lung cells: a model for a mechanism of carcinogenesis. Mutat. Res. 386: 263-277, 1997

Mccabe MJ. Jr., Singh KP., Reddy SA., Chelladurai B., Pounds JG., Reiners JJ. Jr.,
States JC. Sensitivity of myelomonocytic leukemia cells to arsenite-induced cell cycle disruption, apoptosis, and enhanced differentiation is dependent on the inter-relationship between arsenic concentration, duration of treatment, and cell cycle phase. J. Pharmacol. Exp. Ther. 295(2): 724-733, 2000

Meister A., Anderson ME. Glutathione. Annu. Rev. Biochem. 52: 711-760, 1983

Miller WH. Jr, Schipper HM., Lee JS., Singer J., Waxman S. Mechanisms of action of arsenic trioxide. Cancer Res. 62: 3893-3903, 2002

Morgan DO. Principle of CDK regulation. Nature 374: 131-134, 1995

Murgo AJ. Clinical trials of arsenite trioxide in hematologic and solid tumors: overview of the National Cancer Institute cooperative research and development studies. Oncologist 6(Suppl 2): 22-28, 2001

Nakagawa Y., Akao Y., Morikawa H., Hirata I., Katsu K., Naoe T., Ohishi N., Yagi K. Arsenic trioxide-induced apoptosis through oxidative stress in cells of colon cancer cell lines. Life Sci. 70: 2253-2269, 2002

Nakamuro K., Sayato Y. Comparative studies of chromosomal aberration induced by trivalent and pentavalent arsenic. Mutat. Res. 88: 73-80, 1981

National Academy of Sciences. Arsenic in drinking water. Washington DC: National Academy of Science Press, 1999

Nayak SK., O'Toole C., Price ZH. A cell line from an anaplastic transitional cell carcinoma of human urinary bladder. Br. J. Cancer 35: 142-151, 1977

Noda A., Ning Y., Venable SF., Pereira-Smith OM., Smith JR. Cloning of senescent cell-derived inhibitors of DNA synthesis using an expression screen. Exp. Cell Res. 211: 90-98, 1994

Okui T., Fujiwara Y. Inhibition of human excision DNA repair by inorganic arsenic and
the co-mutagenic effect in V79 Chinese hamster cells. Mutat. Res. 172: 69-76, 1986

Pagano PJ., Tornheim K., Cohen RA. Superoxide anion production by rabbit thoracic aorta: Effects of endothelium-derived nitric oxide. Am. J. Physiol. 265: H707-H712, 1993

Park JW., Jang MA., Lee YH., Passaniti A., Kwon TK. p53-independent elevation of p21 expression by PMA results from PKC-mediated mRNA stabilization. Biochem. Biophys. Res. Commun. 280: 244-248, 2001

Park WH., Cho HC., Jung CW., Park JO., Kim K., Im YH., Lee MH., Kang WK., Park K. Arsenic trioxide inhibits the growth of A498 renal cell carcinoma cells via cell cycle arrest or apoptosis. Biochem. Biophys. Res. Commun. 300: 230-235, 2003

Park WH., Serol JG., Kim ES. Arsenic trioxide-mediated growth inhibition in MC/CAR myeloma cells via cell cycle arrest in association with induction of cyclin-dependent kinase in inhibitor, p21, and apoptosis. Cancer Res. 60: 3065-3071, 2000

Perkins ND., Felzien LK., Betts JC., Leung K., Beach DH., Nabel GJ. Regulation of NF-kB by cyclin-dependent kinases associated with the p300 coactivator. Science 275: 523-527, 1997

Pontius FW., Brown KG., Chen CJ. Health implications of arsenic in drinking water. J.
Am. Water Works Assoc. 86: 52-63, 1994

Porter AC., Fanger GR., Vaillancourt RR. Signal transduction pathways regulated by arsenate and arsenite. Oncogene. 18: 7794-7802, 1999

Rasmussen RE., Menzel DB. Variation in arsenic-induced sister chromatid exchange in human lymphocytes and lymphoblastoid cell lines. Mutat. Res. 386: 299-306, 1997

Roboz GJ., Dias S. Lam G. Arsenic trioxide induces dose- and time-dependent apoptosis of endothelium and may exert an antileukemic effect via inhibition of angiogenesis. Blood 96: 1525-1530, 2000

Roninson IB. Oncogenic functions of tumor suppressor p21WAF1/CIP1/SDI1 : association with cell senescence and tumor-promoting zctivities of stromal fibroblasts. Cancer Lett. 179: 1-14, 2002

Rossman TG., Stone D., Molina M., Troll W. Absence of arsenite mutagenicity in E. coli. and Chinese hamster cells. Environ. Mutagen. 2: 307-314, 1980

Ruano MJ., Herna´ ndez-Hernando S., Jime´ nez1 A., Estrada C., Villalobo A. Nitric oxide-induced epidermal growth factor-dependent phosphorylations in A431 tumor cells. Eur. J. Biochem. 270: 1828-1837, 2003

Russo T., Zambrano N., Esposito F., Ammendola R., Cimino F., Fiscella M., Jackman J., O’Connor P., Anderson C., Appella E. A p53-independent pathway for activation of WAF1/CIP expression following oxidative stress. J. Biol. Chem. 270: 29386- 29391, 1995

Samet JM., Silbajoris R., Wu W., Graves LM. Tyrosine phosphatases as targets in metal-induced signaling in human airway epithelial cells. Am. J, Respir. Cell Mol. Biol. 134: 357–364, 1999

Shao W., Fanelli M., Ferrara FF., Riccioni R., Rosenauer A., Davison K., Lamph WW., Waxman S., Pelicci PG., Lo Coco F., Avvisati G., Testa U., Peschle C., Gambacorti-Passerini C., Nervi C., Miller WH. Jr. Arsenic trioxide as an inducer of
apoptosis and loss of PML/RAR_ protein in acute promyelocytic leukemia cells. J. Natl. Cancer Inst. 90: 124–133, 1998

Shen YH., Godlewski J., Zhu J., Sathyanarayana P., Leaner V., Birrer MJ., Rana A., Tzivion G. Cross talk between JNK/SAPK and ERK/MAPK pathways: sustained activation of JNK blocks ERK activation by mitogenic factors. J. Biol. Chem. In press, 2003

Shen ZX., Chen GQ., Ni JH. Use of arsenic trioxide (As2O3) in the treatment of acute
promyelocytic leukemia (APL):II. Clinical efficacy and pharmacokinetics in relapsed patients. Blood 89: 3354-3360, 1997

Sherr CJ., Roberts JM. CDK inhibitors: positive and negative regulation of G1-phase progression. Genes. Dev. 13: 1501-1512, 1999

Simeonaova PP., Wang S., Hulderman T., Luster MI. c-Src-dependent activation of the epidermal growth factor receptor and mitogen-activated protein kinase pathway by arsenic. J. Biol. Chem. 277: 2945-2950, 2002

Simeonaova PP., Wang S., Toriuma W., Kommineni V., Matheson J., Unimye N., Kayama F., Harki D., Ding M., Vallyathan V., Luster MI. Arsenic mediates cell proliferation and gene expression in the bladder epithelium: association with
activating protein-1 transformation. Cancer Res. 60: 3445-3453, 2000

Siu PY., Chan YW., Fung KP. Effect of arsenic trioxide on human hepatocellular carcinoma HepG2 cells: Inhibition of proliferation and induction of apoptosis. Life Sci. 71: 275-285, 2002

Smith KR., Klei LR., Barchowsky A. Arsenite stimulates plasma membrane NADPH oxidase in vascular endothelial cells. Am. J. Physiol. Lung Cell Mol. Physiol. 280: L442-L449, 2001

Smits VA., Klompmarker R., Vallenius T., Rijksen G., Makela TP., Medema RH. p21 inhibits thr 161 phosphorylation of cdc2 to enhance the G2 DNA damage checkpoint. J. Biol. Chem. 275: 30638-20643

Snowden AW., Anderson LA., Webster GA., Perkins ND. A novel transcriptional repression domain mediates p21WAF1/CIP1 induction of p300 transactivation. Mol. Cell Biol. 20: 2676-2686, 2000

States JC., Reiners JJ. Jr., Pounds JG., Kaplan DJ., Beauerle BD., McNeely SC., Mathieu P., McCabe MJ. Jr. Arsenite disrupts mitosis and induces apoptosis in SV40-transdormed human skin fibroblasts. Toxicol. Appl. Pharmacol. 180: 83-91, 2001

Sun HD., Ma L., Hu XC. Ai-Lin 1 treated 32 cases of acute promyelocytic leukemia. Chin. J. Integrat. Chin. Western.Med. 12: 170-172, 1992

Trouba KJ., Wauson EM., Vorce RL. Sodium arsenite-dysregulation of proteins involved in proliferative signaling. Toxicol. Appl. Pharmacol. 164: 161-170, 2000

Vega L., Styblo M., Patterson R., Cullen W., Wang C., Germolec D. Differential effects of trivalent and pentavalent arsenicals on cell proliferation and cytokine secretion in normal human epidermal keratinocytes. Toxicol. Appl. Pharmacol. 172: 225-232, 2001

Vogt BL., Rossman TG. Effects of arsenite on p53, p21, and cyclin D1 expression in normal human fibroblasts- a possible mechanism for arsenite’s comutagenicity. Mut. Res. 478: 159-168, 2001

Voldborg BR., Damstrup L., Spang-Thomsen M., Poulsen HS. Epidermal growth factor receptor (EGFR) and EGF mutations, function and possible role in clinical trials. Ann. Oncol. 8: 1197-1206, 1997

Wang TS., Hsu TY., Chung CH., Wang ASS., Bau DT., Jan KY. Arsenite induces oxidative DNA adducts and DNA-protein cross-links in mammalian cells. Free Radic. Biol. Med. 31(3): 321-330, 2001

Wang ZG., Rivi R., Delva L. Arsenic trioxide and melarsoprol induce programmed cell death in myeloid leukemia cell lines and function in a PML and PML-RARa independent manner. Blood 92: 1497-1504, 1998

Wang ZY. Arsenic compounds as anticancer agents. Cancer Chemother. Pharmacol. 48(Suppl 1): S72-S76, 2001

Waxman S., Anderson KC. History of the development of arsenic derivatives in cancer
therapy. Oncologist 6(Suppl 2): 3-10, 2001

Weil M., Raff MC., Braga VM. Caspase activation in the terminal differentiation of human epidermal keratinocytes. Curr. Biol. 9(7): 361-364, 1999

Weinberg WC., Denning MF. p21WAF1 control of epithelial cell cycle and cell fate. Crit. Rev. Oral Biol. Med. 13(6): 453-464, 2002

Westermarck J., Li SP., man S., Kallunki T., Han J., Kahari VM. p38 mitogen-activated protein kinase-dependent activation of protein phosphatases 1 and 2A inhibits MEK1 and MEK2 activity and collagenase 1 (MMP-1) gene expression. Mol. Cell. Biol. 21: 2373-2383, 2001

Wiencke JK., Yager JW. Specificity of arsenite in potentiating cytogenetic damage induced by the DNA crosslinking agent diepoxybutane. Environ. Mol. Mutagen. 19: 195-200, 1991

Wu W., Graves LM., Jaspers I., Devlin RB., Reed W., Samet JM. Activation of the EGF receptor signaling pathway in human airway epithelial cells exposed to metals. Am. J. physiol. 277: L924-L931, 1999

Xiong Y., Hannon GJ., Zhang H., Casso D., Kobayashi R., Beach D. p21 is a universal
inhibitor of cyclin kinases. Nature 366: 701-704, 1993

Yamamoto T., Nishida T., Miyajima N., Kawai S. Ooi T., Toyoshima K. The erbB gene of avian erythroblastosis virus is a membrane of the src gene family. Cell 35: 71-78, 1983

Yang CH., Kuo ML., Chen JC. Arsenic trioxide sensitivity is associated with low level of glutathione in cancer cells. Br. J. Cancer 81: 796-799, 1999

Yih LH., Lee TC. Effects of exposure protocol on induction of kinetochore-plus and -minus micronuclei by arsenite in diploid human fibroblasts. Mutat. Res. 440: 75-82, 1990

Zhang P., Wang SY., Hu XH. Arsenic trioxide treated 72 cases of acute promyelocytic leukemia. Chin. J.Hematol. 17: 58-62, 1996

Zhang Y., Fujita N., Tsuruo T. Caspase-mediated cleavage of p21WAF1/CIP1 converts cancer cells from growth arrest to undergoing apoptosis. Oncogene. 18: 1131-1138, 1999

Zhang Z., Leonard SS., Huang C., Vallyathan V., Castranova V., Shi X. Role of reactive oxygen species and MAPKs in vanadate-induced G2/M phase arrest. Free Radic. Biol. Med. 34(10): 1333-1342, 2003

Zhou BP., Liao Y., Xia W., Spohn B., Lee MH., Hung MC. Cytoplasmic localization of p21CIP1/WAF1 by Akt-induced phosphorylation in HER-2/neu-overexpressing cells. Nat. Cell Biol. 3: 245-252, 2001

Zhu J., Koken MH., Quignon F., Chelbi-Alix MK., Degos L., Wang ZY., Chen Z., de The´ H. Arsenic-induced PML targeting onto nuclear bodies: implications for the treatment of acute promyelocytic leukemia. Proc. Natl. Acad. Sci. USA 94: 3978–3983, 1997