Clinical Cancer Research Meeting Calendar Metabolism
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Clemons, M.
Right arrow Articles by Margison, G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Clemons, M.
Right arrow Articles by Margison, G.
Clinical Cancer Research Vol. 6, 966-970, March 2000
© 2000 American Association for Cancer Research

Experimental Therapeutics, Preclinical Pharmacology

Macrophage Inflammatory Protein 1{alpha} Attenuates the Toxic Effects of Temozolomide in Human Bone Marrow Granulocyte- Macrophage Colony-forming Cells1

Mark Clemons2, Amanda Watson, Anthony Howell, James Chang, Claire Heyworth, Brian Lord, Nidya Testa, T. Michael Dexter and Geoffrey Margison

Cancer Research Campaign Section of Genome Damage and Repair [M. C., A. W., G. M.], Cancer Research Campaign Department of Medical Oncology [M. C., A. H.], and Cancer Research Campaign Section of Haemopoietic Cell and Gene Therapeutics [C. H., T. M. D., B. L., N. T.], Paterson Institute for Cancer Research, and Department of Pathology, Christie Hospital [J. C.], Manchester M20 4BX, United Kingdom


   ABSTRACT
Top
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Macrophage inflammatory protein 1{alpha} (MIP-1{alpha}) is a chemokine that may act principally by preventing hemopoietic cells from entering G1, thereby attenuating the cytotoxic effects of cell cycle-specific chemotherapeutic agents. Here we examine the effect of MIP-1{alpha} on the sensitivity of human granulocyte-macrophage hemopoietic progenitor cells (granulocyte-macrophage colony-forming cells; GM-CFCs) with the cytotoxic effects of antitumor agents that act mainly via alkylation at the O6 position of guanine in DNA. Mononuclear cell preparations from human bone marrow were used in an in vitro GM-CFC colony-forming assay. The GM-CFC survival from individual patients displayed a range of sensitivities to the methylating agent temozolomide [(Tz) 20–55% survival at 10 µg/ml Tz]. However, in all 16 cases, MIP-1{alpha} (50 ng/ml) protected against GM-CFC killing: survival in the presence of MIP-1{alpha} ranged from 65–97% at 10 µg/ml Tz, with GM-CFCs being 1.5–4.5-fold more resistant than control cells from the same patient. The highest levels of protection were seen in the GM-CFCs with the highest sensitivity in the absence of MIP-1{alpha}. Similar degrees of protection were seen for the methylating agent streptozotocin, but no protection was detected for the chloroethylating agents carmustine or mitozolomide in the samples for which there was protection against the toxic effects of Tz. Whereas the mechanism of this effect remains to be established, the results may have potential immediate clinical application in the attenuation of hematological toxicity after administration of methylating antitumor agents.


   INTRODUCTION
Top
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Hemopoietic toxicity is the major dose-limiting factor for a number of commonly used chemotherapeutic agents. Circumvention of such effects would allow dose intensification and possibly improved tumor response and long-term survival in a range of tumor types. Hemopoietic growth factors such as granulocyte colony-stimulating factor have allowed some dose intensification, but the practical gains have been disappointing (1) .

An alternative approach to growth stimulation is to maintain stem cells in a quiescent state during periods of chemotherapy treatment so that the cells have an increased period during which the repair of potentially lethal damage may proceed prior to replication. This strategy has been shown to attenuate the cytotoxic effects on hemopoiesis (2, 3, 4, 5) and epithelium (6) , with the former being reflected in accelerated bone marrow and peripheral blood cell recoveries. One agent that has been demonstrated to be a specific hemopoietic stem cell proliferation inhibitor is MIP-1{alpha}3 (3 , 7 , 8) . Although MIP-1{alpha} is well tolerated (9) , thus far, only modest (10) or no (11) myeloprotective effects have been demonstrated clinically.

Alkylating agents that are methylating (e.g., dacarbazine, procarbazine, or Tz) or chloroethylating (e.g., BCNU or lomustine) are referred to as O6-alkylating agents because they exert their cytotoxic effects principally via the O6 position of guanine in DNA. We have shown previously that Tz is toxic to human GM-CFCs and that this effect is exacerbated by inactivation of the DNA repair protein, ATase (12) , which normally attenuates the toxic effects of such agents.

To establish whether MIP-1{alpha} might protect hemopoietic cells against the toxic effects of O6-alkylating agents, we investigated the sensitivity of primary human bone marrow GM-CFCs to the cytotoxic effects of these agents in the presence and absence of MIP-1{alpha} using an in vitro colony-forming assay. Tz was used most extensively because it is currently undergoing clinical development (13) .


   MATERIALS AND METHODS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Alkylating Agents and MIP-1{alpha}.
Tz was provided by the Cancer Research Campaign formulation unit. Steptozotocin and BCNU were obtained from the Christie Hospital Pharmacy, and mitozolomide was obtained from May and Baker. Stock solutions were made in DMSO and stored at -20°C. MIP-1{alpha} was supplied by British Biotechnology Limited (Oxford, United Kingdom) as a nonaggregating, genetically engineered variant of human MIP-1{alpha} (LD78) known as BB-10010. BB-10010 was dissolved in PBS at 50 µg/ml and stored at -20°C.

Bone Marrow Samples.
Ethics approval for the study was obtained from the South Manchester Ethics Committee. Human bone marrow samples were obtained by aspiration from the right posterior iliac crest after informed consent was obtained from patients undergoing staging investigations for previously untreated lung or breast cancer. Up to 2 ml of marrow were aspirated, mixed immediately with transport medium [10 ml of Iscove’s modified Dulbecco’s medium (Life Technologies, Inc.) containing 40 units of preservative-free heparin and 2% FCS], and stored on ice. Each sample was assessed microscopically (by J. C.) for the presence of cancer cells, and if cancer cells were present, the sample was not utilized further. Erythrocytes were removed by density centrifugation (14) . Samples were diluted 1:1 with PBS layered over an equal volume of J-Prep (1.077 mg/ml; TechGen International) and centrifuged at 400 x g for 30 min at room temperature. The mononuclear cells at the interface were collected, washed twice with PBS, and used in colony-forming assays.

GM-CFC Assay.
The isolated bone marrow cells were diluted to 1–2 x 105 cells/ml in medium [300 mosmol Iscove’s modified Dulbecco’s medium containing 20% FCS and 10% 5637 conditioned medium as a source of growth factors (15) ]. MIP-1{alpha} (final concentration, 50 ng/ml) was added to the cells, and 5–10 min later, agar noble (Life Technologies, Inc.; final concentration, 0.3%) was added, and the cells were plated into 35-mm Petri dishes containing the appropriate concentrations of each chemotherapeutic agent (diluted in medium). Control plates contained an equivalent volume of DMSO. After incubating for 9 days at 37°C in an atmosphere of 5% CO2 and 95% air, colonies that arose from the GM-CFC lineage and contained more than 50 cells were counted. In the absence of any drug, these conditions gave {approx}50 colonies/plate. A protection factor was calculated by dividing the percentage survival with MIP-1{alpha} by the percentage survival without MIP-1{alpha}, which was then plotted against the control survival with Tz (10 µg/ml) alone.


   RESULTS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Effect of Alkylating Agents and MIP-1{alpha} on GM-CFC Survival.
The survival of GM-CFCs after exposure to increasing doses of Tz in 6 of the 16 bone marrow mononuclear cell preparations examined is shown in Fig. 1Citation . GM-CFCs displayed a wide range of sensitivities, but in all cases, pretreatment with MIP-1{alpha} decreased sensitivity to Tz. Fig. 2Citation shows that for all samples studied, survival at 10 µg/ml Tz ranged from 20–55% (mean, 43%) and 65–97% (mean, 88%) in the absence and presence of MIP-1{alpha}, respectively. The mean protection ratio factor was 2.2. However, there was no direct correlation between survival in the absence of MIP-1{alpha} and the protection afforded by MIP-1{alpha} treatment (i.e., cells that were inherently more sensitive to Tz were afforded the greatest extent of protection by MIP-1{alpha}; Fig. 3Citation ).



View larger version (21K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 1. Sensitivity of GM-CFCs in six individual human bone marrow mononuclear cell preparations to the cytotoxic effects of Tz in the absence (•) and presence ({blacksquare}) of MIP-1{alpha} (50 ng/ml).

 


View larger version (46K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 2. Survival (percentage of control) of GM-CFCs in 16 individual human bone marrow mononuclear cell preparations to the cytotoxic effects of 10 µg/ml Tz in the absence ({blacksquare}) and presence ({square}) of MIP-1{alpha} (50 ng/ml). Data were intrapolated from the survival curves.

 


View larger version (16K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 3. Protection factor (fold increase in survival) provided by MIP-1{alpha} on the sensitivity of GM-CFCs to the cytotoxic effects of Tz (10 µM/ml).

 
In the Tz-untreated control samples, there were generally fewer colonies in the presence of MIP-1{alpha} than in the absence of MIP-1{alpha}. This was only statistically significant in 6 of the 16 samples, for which the protection factors ranged from 1.5–3.9; the range for those samples for which there was no statistically significant reduction in colony-forming ability was 1.5–4.5. Therefore, there was no indication of any relationship between MIP-1{alpha}-induced reduced colony-forming ability and increased resistance to Tz.

The effect of MIP-1{alpha} pretreatment on GM-CFC sensitivity to other chemotherapeutic agents was examined for a smaller number of samples. The results show that MIP-1{alpha} was able to protect GM-CFCs against the toxic effects of the methylating agent streptozotocin but not against the effects of the chloroethylating agents mitozolomide and BCNU (Fig. 4)Citation .



View larger version (13K):
[in this window]
[in a new window]
[Download PPT slide]
  		Fig. 4. Sensitivity of GM-CFCs in three individual human bone marrow mononuclear cell preparations to the cytotoxic effects of streptozotocin, mitozolomide, and BCNU in the absence (•) and presence ({blacksquare}) of MIP-1{alpha} (50 ng/ml).

 

   DISCUSSION
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Hemopoietic toxicity is frequently the major dose-limiting factor for a number of commonly used chemotherapeutic agents. Circumvention of such effects would allow dose intensification and possibly improve tumor response and patient survival in a range of tumor types. Hemopoietic growth factors have allowed some dose intensification, but the practical gains have been limited (1) . An alternative approach to growth stimulation is to maintain stem cells in a quiescent state during periods of chemotherapy treatment so that the cells have an increased period during which the repair of potentially lethal damage may proceed before replication.

MIP-1{alpha} is a member of a large family of small, inducible, and secreted cytokines (7 , 16) that, in vivo, rapidly reduce the cycling and numbers of progenitor cells in bone marrow and spleen (17) . These inhibitory effects appear to be specific for multipotential hemopoietic precursor cells that are intermediate to late in the stem cell hierarchy (18, 19, 20) . Murine models using MIP-1{alpha} in combination with cell cycle-specific (2 , 3) and nonspecific chemotherapeutic agents as well as repeated exposure to sublethal doses of ionizing radiation (21 , 22) have confirmed that MIP-1{alpha}-treated mice show attenuated levels of hemopoietic damage, increased recovery of leukocyte numbers, and improved progenitor cell mobilization. Recent studies suggest that these chemoprotective effects of MIP-1{alpha} are mediated through inhibition of primitive progenitors from entering S phase (23) .

To examine the extent to which MIP-1{alpha} might protect hemopoietic cells against the toxic effects of methylating and chloroethylating agents, primary human bone marrow mononuclear cell preparations were exposed to these agents in the presence and absence of MIP-1{alpha}. As reported previously (12) , GM-CFCs showed variable sensitivity to the methylating agent Tz over the concentration range used, the highest dose of which equates to the plasma levels achieved clinically (24) . However, in all samples, MIP-1{alpha} exposure resulted in the protection of the GM-CFCs against toxicity. The extent of this protection was variable: those samples that were intrinsically more sensitive to Tz were afforded the greatest degree of protection. In the untreated controls, MIP-1{alpha} caused a statistically significant reduction in the number of granulocyte macrophage colonies in <40% of the samples, and there was no correlation between this and protection against Tz toxicity. Therefore, unless protection was mediated by a transient growth suppression that had no effect on the number of colonies seen, cell cycle delay does not appear to explain our observations.

We have reported previously that inactivation of the DNA repair protein ATase, the principal mechanism of resistance to methylating agents, resulted in a considerably increased sensitivity of human GM-CFCs to the toxic effects of Tz (12) . Hence, another possible explanation for the protection against Tz toxicity observed is that MIP-1{alpha} might up-regulate the expression of ATase. If so, protection against the toxic effects of other methylating agents might be expected, and, indeed, this was seen with streptozotocin.

The toxic effects of the chloroethylating agents are also mediated by alkylation at the O6 position of guanine, in this case via lethal DNA interstrand cross-link formation (25 , 26) . Toxicity can be increased by inactivation of ATase (27 , 28) . Therefore, if MIP-1{alpha} increased ATase levels, it would be expected to attenuate resistance to this class of agents. However, protection against neither mitozolomide nor BCNU was observed in samples that were shown simultaneously to display increased MIP-1{alpha}-mediated resistance to Tz.

It is possible that MIP-1{alpha} is acting not via DNA repair mechanisms but via effects on cell cycle regulation, because delaying DNA replication would be expected to allow more time for ATase recovery by de novo synthesis, and this would then allow further repair of the potentially cytotoxic lesions and hence attenuate the toxicity of Tz. This would be expected to have much less impact on the toxicity of the chloroethylating agents that kill cells via the relatively rapid formation of DNA interstrand cross-links because only the precursors of these cross-links are substrates for ATase action. In this case, slow recovery of ATase activity would not be expected to have any effect on survival. Unfortunately, the small number of bone marrow cells available from each individual sample precluded simultaneous assessment in the same sample of ATase expression levels and survival after treatment with Tz or a chloroethylating agent. It would be clinically useful if it could be established that, as with human tumor xenografts (29) , ATase levels can predict response to these agents.

An attractive strategy for protecting bone marrow cells against the toxic effects of O6-alkylating agents is to introduce the ATase cDNA into human hemopoietic cells ex vivo via retroviral transduction, followed by reintroduction into the host before chemotherapy (30, 31, 32, 33) . The present report indicates that MIP-1{alpha} may be a viable alternative to such gene therapy approaches. Irrespective of the mechanism of protection of GM-CFCs by MIP-1{alpha}, the possible clinical exploitation of the observation should be considered, not only with Tz, but also for other methylating agents such as dacarbazine, for which dose escalation is clinically useful. In addition to its potential role in dose intensification, MIP-1{alpha} has the advantage of maintaining stem cell numbers and viability, which should result in reduced risks of both short- and long-term bone marrow toxicity.


   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 Supported by the Cancer Research Campaign of the United Kingdom. M. C. was the recipient of a Leukaemia Research Fund Fellowship. Back

2 To whom requests for reprints should be addressed. Present address: Department of Medical Oncology 5-303, Princess Margaret Hospital, 610 University Avenue, Toronto M5G -2M9, Canada. Phone: (416) 946-4534; Fax: (416) 946-2983; E-mail: markclemons{at}sprint.ca Back

3 The abbreviations used are: MIP-1{alpha}, macrophage inflammatory protein 1{alpha}; GM-CFC, granulocyte-macrophage colony-forming cell; Tz, temozolomide; BCNU, carmustine; ATase, O6-alkylguanine-DNA-alkyltransferase. Back

Received 8/16/99; revised 11/29/99; accepted 12/ 6/99.


   REFERENCES
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Clemons M. J., Gharif R., Howell A. Review of dose-intensification of standard chemotherapy for advanced breast cancer using colony-stimulating factors. Cancer Treat. Rev., 24: 173-184, 1998.[CrossRef][Medline]
  2. Lord B. I., Dexter T. M., Clements J. M., Hunter M. A., Gearing A. J. Macrophage inflammatory protein protects multipotent haematopoietic cells from the effects of hydroxyurea in vivo. Blood, 79: 2605-2609, 1992.[Abstract/Free Full Text]
  3. Dunlop D. J., Wright E. G., Lorimore S., Graham G. J., Holyoake T., Kerr D. J., Wolpe S. D., Pragnell I. B. Demonstration of stem cell inhibition and myeloprotective effects of SCI/rhMIP1{alpha} in vivo. Blood, 79: 2221-2225, 1992.[Abstract/Free Full Text]
  4. Guigon M., Enouf J., Frindel E. Effects of CFS-S inhibitors on murine bone marrow during ARA-C treatment. I. Effects on stem cells. Leuk. Res., 4: 385-391, 1980.[CrossRef][Medline]
  5. Paukovits W. R., Moser M. H., Paukovits J. B. Pre-CFU-S quiescence and stem cell exhaustion after cytostatic drug treatment. Protective effects of the inhibitory peptide pGlu-Glu-Asp-Gys-Lys (pEEDCK). Blood, 87: 1755-1761, 1993.
  6. Sonis S. T., Linquist L., Van Vugt A., Stewart A. A., Stam K., Qu G-Y., Iwata K. K., Hayley J. D. Prevention of chemotherapy-induced ulcerative mucositis by transforming growth factor ß3. Cancer Res., 54: 1135-1138, 1994.[Abstract/Free Full Text]
  7. Wolpe S. D., Cerami A. Macrophage inflammatory proteins 1 and 2: members of a novel superfamily of cytokines. FASEB J., 3: 2565-2573, 1989.[Abstract]
  8. Hunter M. G., Bawden L., Brotherton D., Craig S., Cribbes S., Czaplewski L. G., Dexter T. M., Drummond A. H., Gearing A. H., Heyworth C. M. BB-10010: an active variant of human macrophage inflammatory protein-1{alpha} with improved pharmaceutical properties. Blood, 12: 4400-4408, 1995.
  9. Marshall E., Lord B. I., Howell A. H. Clinical effects of human MIP-1{alpha} (LD78) administration to humans: a Phase I study in cancer patients and normal healthy volunteers with the genetically engineered variant, BB-10010. Eur. J. Cancer, 34: 1023-1029, 1997.[CrossRef]
  10. Clemons M. J., Marshall E., Dürig J., Watanabe K., Howell A., Miles D., Earl H., Kiernan J., Griffiths A., Towlson K., DeTakats P., Dexter T. M., Testa N. G., Lord B. I. A randomised Phase 2 study of BB-10010 (macrophage inflammatory protein 1-{alpha}) in patients with advanced breast cancer receiving 5-FU, Adriamycin, and cyclophosphamide (FAC) chemotherapy. Blood, 92: 1-11, 1998.[Free Full Text]
  11. Bernstein S. H., Eaves C. J., Herzig R., Fay J., Lynch J., Phillips G. L., Christiansen N., Reece D., Ericson S., Stephan M., Kovalsky M., Hawkins K., Rasmussen H., Devos A., Herzig G. P. A randomized Phase II study of BB-10010: a variant of human macrophage inflammatory protein-1{alpha} for patients receiving high-dose etoposide and cyclophosphamide for malignant lymphoma and breast cancer. Br. J. Haematol., 99: 888-895, 1997.[CrossRef][Medline]
  12. Fairbairn L. J., Watson A. J., Rafferty J. A., Elder R. H., Margison G. P. O6-Benzylguanine increases the sensitivity of human primary bone marrow cells to the cytotoxic effects of temozolomide. Exp. Hematol., 23: 112-116, 1995.[Medline]
  13. Middleton M., Lunn J. M., Morris C., Rustin G., Wedge S. R., Brampton M. H., Lind M. J., Lee S. M., Newell D. R., Bleehen N. M., Newlands E. S., Calvert A. H., Margison G. P., Thatcher N. O6-Methylguanine-DNA methyltransferase in pretreatment tumour biopsies as a predictor of response to temozolomide in melanoma. Br. J. Cancer, 78: 1199-1202, 1998.[Medline]
  14. Coutinho, L. H., Gilleece, M. H., Dewynter, E. A., Will, A., and Testa, N. G. Clonal and long-term culture using human bone marrow. In: N. G. Testa and G. M. Molneux (eds.), Haemopoiesis: A Practical Approach, p. 288. Oxford, United Kingdom: IRL Press, 1993.
  15. Myers C. D., Katz F. E., Joshi G., Millar J. L. A cell line secreting stimulating factors for CFU-GEMM culture. Blood, 64: 152-155, 1984.[Abstract/Free Full Text]
  16. Oppenheim J. J., Zacharial C. O. C., Mukaida N., Matoushima R. Properties of the novel proinflammatory supergene "intercrine" cytokine family. Annu. Rev. Immunol., 9: 617-648, 1991.[Medline]
  17. Cooper S., Martel C., Broxmeyer H. E. Myelosuppressive effects in vivo with very low dosages of monomeric recombinant murine macrophage inflammatory protein-1{alpha}. Exp. Hematol., 22: 186-193, 1994.[Medline]
  18. Broxmeyer H. E., Sherry B., Cooper S. Macrophage inflammatory protein (MIP) 1ß abrogates the capacity of MIP-1{alpha} to suppress myeloid progenitor cell growth. J. Immunol., 147: 2978-2983, 1991.[Abstract]
  19. Broxmeyer H. E., Sherry B., Lu L., Cooper S., Oh K., Tekamp-Olson P., Cerami A. Enhancing and suppressing effects of recombinant murine macrophage inflammatory proteins on colony formation in vitro by bone marrow myeloid progenitor cells. Blood, 76: 1110-1116, 1990.[Abstract/Free Full Text]
  20. Keller J. R., Bartelmez S. H., Sitnicka R., Ruscetti F. W. Distinct and overlapping direct of macrophage inflammatory protein-1{alpha} and transforming growth factor ß on haematopoietic progenitor/stem cell growth. Blood, 84: 2174-2181, 1994.
  21. Lord B. I., Marshall E., Woolford L. B., Hunter M. G. BB-10010/MIP-1{alpha} in vivo maintains haemopoietic recovery following repeated cycles of sublethal irradiation. Br. J. Cancer, 74: 1017-1022, 1996.[Medline]
  22. Marshall E., Woolford L. B., Lord B. I. BB-10010 (a variant of human MIP-1{alpha}) enhances leucocyte recovery and progenitor cell mobilisation following cyclophosphamide. Br. J. Cancer, 75: 1715-1720, 1997.[Medline]
  23. Cashman J. D., Eaves C. J., Sarris A. H., Eaves A. C. MCP-1, not MIP-1{alpha}, is the endogenous chemokine that cooperates with TGF-ß to inhibit the cycling of primitive normal but not leukemic (CML) progenitors in long-term human marrow cultures. Blood, 92: 2338-2344, 1998.[Abstract/Free Full Text]
  24. Newlands, E. S., Blackledge, G. R. P., Slack, J. A., Stuart, N. S. A., and Stevens, M. F. G. Experimental background and early clinical studies with imidazotetrazine derivatives. In: T. Giraldi, T. A. Connors, and G. A. Cartei (eds.), Triazenes. Chemical, Biological, and Clinical Aspects, p. 184. New York: Plenum Press, 1990.
  25. Tong W. P., Kirk M. C., Ludlam D. B. Formation of the crosslink 1-[N3-deoxycytidyl],2-[N1-doxyguanosinyl]ethane in DNA treated with N,N'-bis(chloroethyl)-N-nitrosourea. Cancer Res., 42: 3102-3105, 1982.[Abstract/Free Full Text]
  26. Bodell W. J., Tokuda K., Ludlum D. B. Differences in DNA alkylation products formed in sensitive and resistant human glioma cells treated with N-(2-chloroethyl)-N-nitrosourea. Cancer Res., 48: 4489-4492, 1988.[Abstract/Free Full Text]
  27. Aida T., Cheitlin R. A., Bodell W. J. Inhibition of O6-alkylguanine-DNA alkyltransferase activity potentiates cytotoxicity and induction of SCEs in human glioma cells resistant to 1,3-bis(chloroethyl)-1-nitrosourea. Carcinogenesis (Lond.), 8: 1219-1223, 1987.[Abstract/Free Full Text]
  28. Dolan M. E., Pegg A. E., Moschel R. C., Grindey G. B. Effect of O6-benzylguanine on the sensitivity of human colon tumor xenografts to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Biochem. Pharmacol., 46: 285-290, 1993.[CrossRef][Medline]
  29. Brent T. P., Vonwronski M. A., Edwards C. C., Bromley M., Margison G. P., Rafferty J. A., Pegram C. N., Bigner D. D. Identification of nitrosourea-resistant human rhabdomyosarcomas by in situ immunostaining of O6-methylguanine-DNA-methyltransferase. Oncol. Res., 5: 83-86, 1993.[Medline]
  30. Allay J. A., Dumenco L. L., Koc O. N., Liu L., Gerson S. L. Retroviral transduction and expression of the human alkyltransferase cDNA provides nitrosourea resistance to hematopoietic cells. Blood, 85: 3342-3354, 1995.[Abstract/Free Full Text]
  31. Reese J. S., Koc O. N., Lee K. M., Liu L., Allay J. A., Phillips W. P., Gerson S. L. Retroviral transduction of a mutant methylguanine DNA methyltransferase gene into human CD34 cells confers resistance to O6-benzylguanine plus 1,3-bis(2-chloroethyl)-1-nitrosourea. Proc. Natl. Acad. Sci. USA, 93: 14088-14093, 1996.[Abstract/Free Full Text]
  32. Chinnasamy N., Rafferty J. A., Hickson I., Ashby J., Tinwell H., Margison G. P., Dexter T. M., Fairbairn L. J. O6-Benzylguanine potentiates the in vivo toxicity and clastogenicity of temozolomide and BCNU in mouse bone marrow. Blood, 89: 1566-1573, 1997.[Abstract/Free Full Text]
  33. Chinnasamy N., Rafferty J. A., Hickson I., Lashford L. S., Longhurst S. J., Thatcher N., Margison G. P., Dexter T. M., Fairbairn L. J. Chemoprotective gene transfer II: multilineage in vivo protection of haemopoiesis against the effects of an antitumour agent by expression of a mutant human O6-alkylguanine-DNA alkyltransferase. Gene Ther., 5: 842-847, 1998.[CrossRef][Medline]



This article has been cited by other articles:


Home page
 Ann OncolHome page
M. E. Trudeau, M. Crump, D. Charpentier, L. Yelle, L. Bordeleau, S. Matthews, and E. Eisenhauer
Temozolomide in metastatic breast cancer (MBC): a phase II trial of the National Cancer Institute of Canada - Clinical Trials Group (NCIC-CTG)
Ann. Onc., June 1, 2006; 17(6): 952 - 956.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Clemons, M.
Right arrow Articles by Margison, G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Clemons, M.
Right arrow Articles by Margison, G.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online