|
Advertisement |
|
|
||
 |
|
|||||
|
|||||
|
 |
||||||
|
||||||
|
||||||
|
Originally published as JCO Early Release 10.1200/JCO.2005.07.385 on May 9 2005 © 2005 American Society of Clinical Oncology. Extent of Damage and Repair in the p53 Tumor-Suppressor Gene After Treatment of Myeloma Patients With High-Dose Melphalan and Autologous Blood Stem-Cell Transplantation Is Individualized and May Predict Clinical OutcomeFrom the Department of Clinical Therapeutics and First Department of Propedeutic Medicine, University of Athens School of Medicine; and Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, Athens, Greece Address reprint requests to Meletios A. Dimopoulos, MD, 227 Kifissias Ave, Kifissia, Athens, 14561, Greece; e-mail: mdimop{at}med.uoa.gr
PURPOSE: To quantitate the individual levels of melphalan-induced DNA damage formation and repair in vivo and to search for possible correlations with clinical outcome in patients with multiple myeloma (MM). PATIENTS AND METHODS: The formation and subsequent repair of DNA damage (monoadducts and interstrand cross-links) in the p53 tumor-suppressor gene, the proto-oncogene N-ras, and the housekeeping gene beta-actin during the first 24 hours after treatment with high-dose melphalan (HDM; 200 mg/m2) supported by autologous blood stem-cell transplantation (ABSCT) was measured in blood leukocytes of 26 patients with MM. The peak DNA adduct levels, the total amount of adducts over time, and the rate of adducts repair in each gene were correlated with response and time to progression after HDM. RESULTS: The levels of gene-specific DNA damage formation and the individual repairing capacity varied up to 16-fold among patients, indicating that the melphalan-induced biologic effect in vivo is highly individualized. A significantly greater DNA damage and a slower rate of repair in p53 for all end points under study were found in patients who achieved tumor reduction compared with nonresponding patients. Furthermore, longer progression-free survival correlated with increased peak monoadduct levels in the p53 gene (P = .032). CONCLUSION: Increased DNA damage and slower repairing capacity in the p53 gene from blood leukocytes after HDM correlate with improved outcome of patients with MM who undergo ABSCT. These results suggest that quantitation of such biologic end points may identify patients who are more likely to benefit from this procedure.
Nitrogen mustards are bifunctional alkylating agents that react extensively with cellular macromolecules (DNA, RNA, and proteins), inducing multiple molecular lesions. Melphalan is an important member of this class of chemotherapeutic agents and is the most effective drug used for treating multiple myeloma (MM). The critical cellular target of melphalan is DNA, which is alkylated primarily at the N-7 position of guanine with lesser reaction at the N-3 position of adenine.1 In addition to monofunctional binding of melphalan to a single site in the DNA molecule (monoadducts), cross-linking between bases in the complementary strands of a DNA molecule (DNA interstrand cross-links) and DNA-protein cross-links also occur. Although interstrand cross-links represent only a small fraction of the total adducts formed, they are thought to be the main determinant of nitrogen mustard toxicity.2,3 Nucleotide excision repair mechanism plays a crucial role in the repair of monoadducts.4 Furthermore, a number of multistep DNA repair pathways, including nucleotide excision repair, homologous recombination, and postreplication/translesion repair, contribute to the interstrand cross-link repair.5 DNA repair mechanisms are believed to play an important role in the protection of cells and tissues after exposure to genotoxic agents. Evidence demonstrating an inverse relationship between cellular DNA repair activity and sensitivity to genotoxic effects comes not only from studies of experimental carcinogenesis,6,7 but also from human syndromes combining deficiency in DNA repair with increased susceptibility to cancer.8,9 Furthermore, there is accumulating evidence that the biologic role of DNA lesions must be evaluated in terms of the fine structure of DNA repair.10 Selective DNA damage and repair seem to affect not only cellular sensitivity to DNA-damaging agents, but also cancer susceptibility and aging.11 We have previously reported the kinetics of gene-specific monoadducts and interstrand cross-link formation and repair in peripheral-blood leukocytes from humans after exposure to melphalan.12 Although measurements of melphalan-induced DNA adduct levels in blood cells from MM patients using immunoassay display a good correlation with the dose of drug administered,13 to the best of our knowledge, there is no study correlating melphalan-induced adduct levels with the clinical outcome. Twenty years ago, McElwain and Powles14 demonstrated that there is a dose-response effect with intravenous melphalan administered at a dose of 100 to 140 mg/m2 in patients with refractory MM. More recently, Palumbo et al15 showed that patients receiving two or three courses of melphalan 100 mg/m2 had superior complete response rate, event-free survival, and overall survival compared with patients receiving standard-dose melphalan and prednisone, suggesting that the extent of melphalan-induced cytotoxicity affects clinical outcome. High-dose melphalan (HDM) combined with autologous blood stem-cell transplantation (ABSCT) is currently the standard treatment for many patients with MM. Despite the remarkable activity of melphalan, only 30% of patients achieve an immunofixation-negative complete response, and the long-term disease-free survival rate is less than 10%.16 Surrogate biologic markers that may predict clinical outcome after treatment in these patients may be of value. The present study is a preliminary report on the in vivo quantitation of gene-specific damage formation and repair in a readily accessible tissue, such as peripheral-blood leukocytes, from MM patients exposed to HDM. Using these results, we searched for possible correlations between HDM-induced tumor reduction, as well as progression-free survival (PFS), and the individual levels of damage and repair in the p53 tumor suppressor gene, the proto-oncogene N-ras, and the housekeeping beta-actin (ß-actin) gene.
Patients Peripheral-blood samples were obtained immediately before and 2, 8, and 24 hours after administration of a single infusion of HDM (200 mg/m2) from 26 patients with MM supported by ABSCT. Patient and disease characteristics are listed in Table 1. Four patients were treated while their disease was relapsing despite chemotherapy (refractory relapse), six patients had not responded to frontline therapy (primary resistant), and 16 patients received HDM in remission that was achieved after treatment with conventional chemotherapy. Thus, 10 patients were considered chemotherapy-resistant and 16 patients were considered chemotherapy-sensitive at the time of HDM. Twenty of 26 patients had measurable serum and/or urine monoclonal protein before the administration of HDM and were assessable for possible subsequent tumor reduction. All 26 patients were assessable for PFS. Clinical response and progression were assessed according to the European Bone Marrow Transplantation Group criteria.17 All patients provided informed consent according to institutional guidelines.
Detection of DNA Damage Gene-specific monoadducts and interstrand cross-link formation and repair were measured, as described previously.12 Briefly, for the measurement of N-alkylpurines (monoadducts and interstrand cross-links together) after DNA isolation from peripheral WBCs (collected after lysis of the RBCs), genomic DNA was digested to completion with HindIII (p53) or EcoRI (N-ras and ß-actin), and DNA samples dissolved in sterile deionized H2O were heated at 70°C for 30 minutes to depurinate N-alkylated bases. Apurinic sites were converted to single-strand breaks by the addition of NaOH for 30 minutes at 37°C, size fractionated using agarose gel electrophoresis, and Southern blotted. For the detection of DNA interstrand cross-links, after DNA isolation and restriction enzyme digestion as described earlier, alkylations were not converted to strand breaks, and DNA was denatured before gel electrophoresis and Southern blotting. Hybridizations for the detection of alkylations in the p53 and N-ras genes were performed as described previously.12 The ß-actin–specific probe was a 202-bp polymerase chain reaction fragment and part of the exon 3 of the human ß-actin gene (forward primer: 5'-CAC-ACT-GTG-CCC-ATC-TAC-GA-3'; reverse primer: 5'-CCA-TCT-CTT-GCT-CGA-AGT-CC-3').18 The rate of DNA repair was defined as the percentage of decrease of DNA damage from the time of highest DNA damage (monoadducts, 2 hours; cross-links, 8 hours) to 24 hours. Total amounts of each type of DNA damage over time were represented by the area under the curve (AUC) for DNA adducts during the whole experiment (0 to 24 hours). The ratio of highest to lowest observations for each type of DNA damage formation and repair represented the interpatient variation of these parameters.
Statistics
In Vivo Kinetics of Melphalan-Induced DNA Adduct Formation and Repair The kinetics of formation and repair of monoadducts within the first 24 hours after exposure to HDM are shown in Figure 1A and are in agreement with our in vitro data presented previously.12 No measurable DNA monoadducts could be detected before the start of the melphalan treatment. All 26 MM patients examined showed a maximum of the adduct levels at 2 hours. Thereafter, mean values of monoadducts decreased by 44.68% ± 14.40% (ß-actin), 38.78% ± 10.07% (p53), and 34.35% ± 11.89% (N-ras) of maximal levels during the 2- to 24-hour time period.
The kinetics of formation and repair of DNA interstrand cross-links are shown in Figure 1B. Again, no measurable DNA interstrand cross-links could be detected before the start of the melphalan treatment. A relatively slow accumulation of DNA damage was observed in all patients, with a maximum at 8 hours. This delayed formation of interstrand cross-links is in agreement with our previous in vitro results12 and the two-step model of Kohn.19 Thereafter, mean values of the melphalan-induced interstrand cross-links decreased by 41.89% ± 15.91% (ß-actin), 34.09% ± 11.01% (p53), and 28.04% ± 9.14% (N-ras) of maximal levels during the 8- to 24-hour time period. Although DNA interstrand cross-links are much more difficult to be repaired compared with monoadducts, it should be noted that the assay used in the present study measures only the excision of one of the cross-linked bases (first step, or unhooking step) and not necessarily the complete removal of the damage. Because the inhibition of strand separation is the critical cytotoxic lesion, the unhooking step represents the critical first step in the repair process.20 A high interindividual variation in the levels of DNA damage formation and repair (as represented by the peak DNA adduct levels, the rate of adduct repair, and the AUC) for both monoadducts and interstrand cross-links was found in both the p53 and N-ras genes (Fig 2), as well as in the ß-actin gene (data not shown). Peak monoadducts levels in different patients fell within a range of 1.9 adducts/106 nucleotides (11.0 to 20.5 adducts/106 nucleotides; ß-actin), 2.2 adducts/106 nucleotides (10.5 to 22.8 adducts/106 nucleotides; p53), and 2.6 adducts/106 nucleotides (9.5 to 24.9 adducts/106 nucleotides; N-ras), whereas peak interstrand cross-links levels fell within a range of 2.3 adducts/106 nucleotides (1.0 to 2.3 adducts/106 nucleotides; ß-actin), 3.1 adducts/106 nucleotides (0.8 to 2.8 adducts/106 nucleotides; p53), and 3.4 adducts/106 nucleotides (0.9 to 2.9 adducts/106 nucleotides; N-ras). Furthermore, the repair rates in different patients fell within a range of 2.7% (24.7% to 67.1%; ß-actin), 2.4% (25.3% to 60.0%; p53), and 3.3% (20.6% to 67.1%; N-ras) for monoadducts and within a range of 2.7% (25.5% to 68.8%; ß-actin), 2.9% (21.0% to 61.9%; p53), and 2.8% (18.8% to 52.9%; N-ras) for interstrand cross-links. Finally, the AUC levels in different patients fell within a range of 11.8 adducts/106 nucleotides x h (30.6 to 360.7 adducts/106 nucleotides x h; ß-actin), 4.5 adducts/106 nucleotides x h (75.6 to 356.9 adducts/106 nucleotides x h; p53), and 16.5 adducts/106 nucleotides x h (28.5 to 469.0 adducts/106 nucleotides x h; N-ras) for monoadducts and within a range of 4.9 adducts/106 nucleotides x h (8.7 to 42.2 adducts/106 nucleotides x h; ß-actin), 5.4 adducts/106 nucleotides x h (8.8 to 47.4 adducts/106 nucleotides x h; p53), and 5.9 adducts/106 nucleotides x h (9.4 to 55.2 adducts/106 nucleotides x h; N-ras) for interstrand cross-links.
Correlation of DNA Damage Formation With DNA Repair There is accumulating evidence demonstrating an inverse relationship between cellular DNA repair activity and sensitivity to genotoxic effects.6-9 Thus, we searched for possible correlations between individual DNA damage and the rate of DNA repair. Using linear regression analysis within individual patients, we found a strong negative correlation between DNA damage formation and the rate of DNA repair in all three genes and in both DNA adducts analyzed. Representative results for the p53 gene are presented in Figures 1C through 1F.
Correlation of DNA Damage Formation and Repair With Clinical and Laboratory Parameters
Correlation of DNA Damage Formation and Repair With Clinical Outcome To search for possible correlations between the individual levels of DNA damage formation/repair and clinical response to HDM, our 20 patients with measurable serum and/or urine monoclonal protein at baseline were classified into two groups. Group A comprised 14 patients who achieved tumor reduction (responders: complete response or partial response) after HDM, whereas group B comprised the six patients without tumor reduction (nonresponders: stable disease or progressive disease). Patients with lower levels of serum ß2-microglobulin at diagnosis and patients with chemotherapy-sensitive disease had a higher likelihood of response after administration of HDM (Table 3).
When the clinical response was related to the peak levels of either type of DNA adducts, significantly greater DNA damage was found in group A in the p53 gene (monoadducts: 15.15 ± 1.48 adducts/106 nucleotides for responders and 12.39 ± 1.57 adducts/106 nucleotides for nonresponders, P = .002; interstrand cross-links: 1.68 ± 0.36 adducts/106 nucleotides for responders and 1.22 ± 0.51 adducts/106 nucleotides for nonresponders, P = .04; Fig 2A). The same pattern was found in the N-ras gene, but differences reached marginal significance (Fig 2B). In contrast, no difference between responders and nonresponders was found in ß-actin gene (data not shown). Furthermore, the rate of repair of either type of melphalan-induced DNA adducts in the p53 gene was also found to correlate with clinical response. In accordance with the peak DNA adducts data presented earlier, a slower rate of repair during the next hours was observed in group A compared with group B (monoadducts: 35.9% ± 5.6% and 49.9% ± 8.1% decrease of maximal levels during the 2- to 24-hour time period for responders and nonresponders, respectively, P = .001; interstrand cross-links: 30.0% ± 6.5% and 45.9% ± 10.7% decrease of maximal levels during the 8- to 24-hour time period for responders and nonresponders, respectively, P = .001; Fig 2C). Similar results were obtained for N-ras, but differences did not reach statistical significance (Fig 2D). Again, no difference was found between responders and nonresponders in the ß-actin gene (data not shown). The combined effect of the induction and the rate of repair of either type of DNA damage in p53 gene, as represented by the AUC for DNA adducts during the whole experiment, was also found to correlate with clinical response. AUC levels of both types of DNA adduct were greater in the responder group (monoadducts: 237.9 ± 61.9 adducts/106 nucleotides x h for responders and 169.8 ± 45.5 adducts/106 nucleotides x h for nonresponders, P = .002; interstrand cross-links: 28.2 ± 9.5 adducts/106 nucleotides x h for responders and 17.7 ± 11.3 adducts/106 nucleotides x h for nonresponders, P = .002; Fig 2E). The same pattern was observed in the N-ras gene, but differences reached marginal significance (Fig 2F). No difference between responders and nonresponders was found in the ß-actin gene (data not shown). In addition, several clinical and laboratory variables were analyzed for their possible correlation with PFS. Chemotherapy-resistant disease was the only parameter associated with shorter PFS (P = .03). We also examined whether the individual levels of HDM-induced gene-specific damage and repair affect PFS. Patients were arbitrarily divided in two groups according to their individual values in each of the three biologic end points in either type of adduct for the p53, N-ras, and ß-actin genes (total of 18 Kaplan-Meier curves), that is, patients having values higher or lower than the corresponding mean value of the given biologic end point were analyzed separately. It was found that patients with greater DNA damage and/or slower rate of repair in the p53 tumor suppressor gene had a longer PFS. As shown in Figure 3, a significant difference for the peak monoadduct levels was revealed (P = .032), indicating that patients with greater p53 damage within the first 2 hours after administration of HDM have a better clinical outcome in the long term. A comparable pattern was observed in the N-ras gene; however, differences were marginally significant. In contrast, no differences were observed in the ß-actin gene. Also, the 10 chemotherapy-resistant patients were separated into two groups depending on the peak monoadduct levels in the p53 gene. Despite the small number of patients, we found that the median PFS for patients with high peak monoadduct levels (ie, increased DNA damage) was not reached, and the median PFS for patients with low peak monoadduct levels was 5 months (P = .1).
Because DNA damage and repair were measured in leukocytes, we also searched for possible correlations between these parameters and mucositis. Thus, patients were classified into the following two groups: patients with grade 3 mucositis (n = 10) and patients with less than grade 3 mucositis (n = 16). It was found that, in all three genes analyzed, grade 3 mucositis was significantly more common in patients with more DNA damage (mean AUC monoadducts: p53, 271.0 ± 96.5 v 204.0 ± 83.5 adducts/106 nucleotides x h, P = .07; N-ras, 309.2 ± 64.2 v 219.3 ± 106.8 adducts/106 nucleotides x h, P = .02; ß-actin, 235.0 ± 64.7 v 169.0 ± 76.1 adducts/106 nucleotides x h, P = .07) and less DNA repair (mean % monoadducts repair: p53, 35.6% ± 10.4% v 41.2% ± 9.5%, P = .19; N-ras, 28.1% ± 6.6% v 50.7% ± 27.5%, P = .017; ß-actin, 37.9% ± 13.8% v 59.4% ± 23.4%, P = .015).
A number of previous studies, particularly those using cancer cell lines, have shown that the loss of p53 function resulted in increased resistance to chemotherapeutic agents.21-24 In contrast, others have found that inactivation of p53, in the absence of other genetic alterations, leads to enhanced sensitivity to multiple chemotherapeutic agents, including melphalan, cisplatin, carboplatin, paclitaxel, and doxorubicin.25,26 Furthermore, Rowley et al26 found that mutated N-ras12 gene was able to protect the ANBL6 myeloma cell line from apoptosis induced by melphalan, dexamethasone, and doxorubicin. We have previously reported the kinetics of gene-specific damage formation and repair in the p53 and N-ras genes of human peripheral-blood mononuclear cells after in vitro treatment with melphalan.12 In the present study, we extend our results by measuring in vivo melphalan-induced gene-specific damage formation and repair in the p53 and N-ras genes and in the housekeeping ß-actin gene of peripheral-blood leukocytes in a large number of patients with MM. A question of fundamental importance in any attempt to use blood leukocyte adduct levels as indicators of tissue-specific therapeutic effectiveness or carcinogenic risk is their relationship to adduct levels in the target cells. Differences in DNA damage formation and repair in nonmalignant cells are mainly governed by gene polymorphisms in important genes related to these processes.8,9 In malignant cells, genes related to DNA damage formation and repair are dysregulated, and this happens to a greater extent with increasing amounts of prior therapy.27,28 Therefore, there will never be a perfect correlation between DNA damage in normal versus malignant tissues. Correlations between drug sensitivity of tumor cells in vitro as well as individual differences in the response of tumor cells to antineoplastic agents have been observed.29,30 However, to perform these assays, invasive procedures are necessary to obtain a sufficient amount of tumor cells, and they are rarely used in clinical practice. Determining DNA adducts formation and repair in a readily accessible tissue, such as peripheral-blood leukocytes, may provide a noninvasive method for evaluating the effectiveness of some antineoplastic agents. A limitation when using peripheral-blood leukocytes as indicators of therapeutic effectiveness is that granulocytes have a median survival of 5 hours; therefore, a selection bias may exist when comparing differences in number of adducts between 2 and 24 hours of repair. However, we have previously shown that the kinetics of gene-specific monoadducts and interstrand cross-link formation and repair are similar in isolated peripheral human lymphocytes after in vitro exposure to melphalan and peripheral-blood leukocytes obtained from MM patients after in vivo melphalan administration.12 Moreover, in several previous studies, leukocyte DNA was used to correlate DNA damage formation and repair with clinical outcome in patients receiving chemotherapy.31-34 We found that the levels of gene-specific DNA damage formation and repair within the first 24 hours varied up to 16-fold among our 26 patients, indicating that the melphalan-induced biologic effect is highly individualized. To the best of our knowledge, no previous study has addressed the kinetics of gene-specific damage formation and repair in vivo. Previous studies addressing possible differences in DNA damage and repair among individuals have used total DNA. Accordingly, lower interindividual variation has been found in Hodgkin's disease and lymphoma patients treated with the alkylating agents procarbazine and dacarbazine, respectively, because adduct levels in different individuals fell within a range of three.35,36 Studies on cisplatin adducts have shown a large interpatient variation in adduct formation that is apparently related to therapy.31,37 Measurement of total DNA adducts after melphalan administration using immunoassay showed a generally low degree of interpatient variation.13 Also, plasma cells from MM patients exposed to melphalan ex vivo display significant differences in DNA interstrand cross-link repair (ie, cells from melphalan-naïve patients showed no repair, whereas cells from previously treated patients exhibited different rates of repair, varying between 42% and 100%).27 To search for possible correlations between the individual levels of DNA damage formation and repair and the clinical outcome, we examined the impact of the high and low levels of damage formation and repairing capacity among our patients on the achievement of tumor reduction after HDM and on PFS. A significantly greater damage in the p53 gene was observed in patients achieving tumor reduction. Panasci et al38 exposed lymphocytes from patients with chronic lymphocytic leukemia to melphalan ex vivo and found that DNA alkylation was two- to five-fold greater in cells from responding patients than cells from resistant patients. Furthermore, in accordance with previous reports showing that in vitro resistance to melphalan is associated with increased repair of DNA damage,27,39 we found that the rate of repair of p53 adducts was significantly lower in the group of responding patients. No correlation with clinical outcome was found in the housekeeping ß-actin gene. Finally, a longer PFS correlated with increased p53 monoadduct formation within the first hours after HDM administration. Thus, although DNA interstrand cross-link is thought to be the main determinant of nitrogen mustard toxicity,40 repair of DNA monoadducts before cross-linking may play an important role in protecting cells from melphalan cytotoxicity and may be a significant factor leading to chemotherapy failure. Significantly greater DNA damage formation and a slower rate of DNA repair was found in the p53 gene of responding patients, whereas no such correlation was obtained for the other two genes analyzed (ß-actin and N-ras). Wild-type p53 has been shown to be involved in DNA repair by blocking cells in the G0/G1 stage of the cell cycle, thus allowing DNA repair before the initiation of DNA synthesis and thus reducing the cytotoxicity of various therapeutic agents.41 Therefore, p53 inactivation resulting from the significant p53-specific damage found in these individuals may render myeloma cells to be repaired less efficiently before the stage of DNA synthesis and more sensitive to melphalan-induced apoptosis. Alternatively, the specific correlation of increased DNA damage and clinical outcome found in p53 may represent nothing but a useful biologic marker in predicting the individual response to drug treatment without a real effect in the increased cytotoxicity of melphalan. Notably, no significant difference in the levels of melphalan-induced lesions was observed between the three gene sequences when naked DNA was treated with melphalan in vitro (Souliotis et al, unpublished data), indicating that the primary base sequence composition (ie, the melphalan targets guanine and adenine)1 in the gene fragments analyzed does not significantly affect the overall distribution of melphalan lesions. Along this line, another interesting finding of our study was that, in all three genes analyzed, grade 3 mucositis was more common in patients with more DNA damage and less DNA repair. Our study included a relatively small number of patients with various disease states before transplantation. Thus, our results should be considered preliminary. Furthermore, an important question is whether measurements of DNA damage and repair may be independent prognostic factors or whether they are surrogate end points to develop more effective therapies. We observed that patients with chemotherapy-resistant disease had less DNA damage and higher repairing capacity than chemotherapy-sensitive patients. No such correlations were detected for serum ß2-microglobulin. Furthermore, it seems that, within the group of chemotherapy-resistant patients, less DNA damage and higher repairing capacity may be associated with shorter PFS. A larger number of patients is needed to provide definitive answers. In conclusion, although the presence of total DNA damage in humans as a result of exposure to nitrogen mustards has been reported in the past,13,27 the present study describes the in vivo kinetics of gene-specific damage formation and repair in human blood leukocytes after therapeutic exposure to HDM. Increased individual damage formation and slower repairing capacity in p53 gene within the first 24 hours after treatment of myeloma patients with HDM correlate with an improved clinical outcome. These results suggest that quantitation of such biologic end points in a readily accessible tissue may be of predictive value for these patients. Because the assessment of p53 gene damage formation and repair after in vitro exposure of peripheral-blood mononuclear cells to melphalan is feasible,12 our ongoing studies will indicate whether in vitro experiments may identify those patients who are more likely to benefit from this treatment.
The following authors or their immediate family members have indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. Consultant/Advisory Role: Meletios A. Dimopoulos, Millennium, Novartis. For a detailed description of this category, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Declaration and Disclosures of Potential Conflicts of Interest found in Information for Contributors in the front of each issue.
We thank S.A. Kyrtopoulos, MD, for his valuable collaboration.
Authors' disclosures of potential conflicts of interest are found at the end of this article.
1. Osborne MR, Wilman DE, Lawley PD: Alkylation of DNA by the nitrogen mustard bis(2-chloroethyl)methylamine. Chem Res Toxicol 8:316-320, 1995[CrossRef][Medline] 2. Lawley PD, Phillips DH: DNA adducts from chemotherapeutic agents. Mutat Res 355:13-40, 1996[CrossRef][Medline] 3. Ringborg U, Hansson J, Jungnelius U, et al: Melphalan-induced DNA cross-linking and inhibition of DNA and RNA synthesis in human melanoma and lymphoblast cells. Anticancer Res 10:297-301, 1990[Medline]
4. Grant DF, Bessho T, Reardon JT: Nucleotide excision repair of melphalan monoadducts. Cancer Res 58:5196-5200, 1998 5. Dronkert ML, Kanaar R: Repair of DNA interstrand cross-links. Mutat Res 486:217-247, 2001[Medline]
6. Swenbeg JA, Bedell MA, Billings KC, et al: Cell-specific differences in O6-alkylguanine DNA repair activity during continuous exposure to carcinogen. Proc Natl Acad Sci U S A 79:5499-5502, 1982 7. Yarosh DB: The role of O6-methylguanine-DNA-methyltransferase in cell survival, mutagenesis and carcinogenesis. Mutat Res 145:1-16, 1985[Medline] 8. Arlett CF: Human DNA repair defects. J Inherited Metab Dis 9:69-84, 1986 (suppl 1) 9. Lehman AR: Xeroderma pigmentosum, Cockayne syndrome and ataxia-telangiectasia: Disorders relating DNA repair to carcinogenesis. Cancer Surv 1:93-118, 1982 10. Hanawalt PC: Heterogeneity of DNA repair at the gene level. Mutat Res 247:203-211, 1991[Medline] 11. Mullenders LH, Vrieling H, Venema J, et al: Hierarchies of DNA repair in mammalian cells: Biological consequences. Mutat Res 250:223-228, 1991[Medline]
12. Souliotis VL, Dimopoulos MA, Sfikakis PP: Gene-specific formation and repair of DNA monoadducts and interstrand cross-links after therapeutic exposure to nitrogen mustards. Clin Cancer Res 9:4465-4474, 2003 13. Tilby MJ, Mewell DR, Viner C, et al: Application of a sensitive immunoassay to the study of DNA adducts formed in peripheral blood mononuclear cells of patients undergoing high-dose melphalan therapy. Eur J Cancer 29A:681-686, 1993 14. McElwain TJ, Powles RL: High-dose intravenous melphalan for plasma-cell leukaemia and myeloma. Lancet 2:822-824, 1983[Medline]
15. Palumbo A, Triolo S, Argentino C, et al: Dose-intensive melphalan with stem cell support (MEL100) is superior to standard treatment in elderly myeloma patients. Blood 94:1248-1253, 1999
16. Barlogie B, Shaughnessy J, Tricot G, et al: Treatment of multiple myeloma. Blood 103:20-32, 2004 17. Blade J, Samson D, Reece D, et al: Criteria for evaluating disease response and progression in patients with multiple myeloma treated by high-dose therapy and haemopoietic stem cell transplantation: Myeloma Subcommittee of the EBMT—European Group for Blood and Marrow Transplant. Br J Haematol 102:1115-1123, 1998[CrossRef][Medline]
18. Nakajima-Iijima S, Hamada H, Reddy P, et al: Molecular structure of the human cytoplasmic beta-actin gene: Interspecies homology of sequences in the introns. Proc Natl Acad Sci U S A 82:6133-6137, 1985 19. Kohn KW: Molecular mechanisms of crosslinking by alkylating agents and platinum complexes, in Sartorelli AC, Lazlo JS, Bertino JR (eds): Molecular Actions and Targets for Cancer Chemotherapy Agents. New York, NY, Academic Press Inc, 1981, pp 3-16 20. Reid BD, Walker IG: The response of mammalian cells to alkylating agents: II. On the mechanism of the removal of sulfur-mustard-induced cross-links Biochim Biophys Acta 179:179-188, 1968 21. Lowe SW, Ruley HE, Jacks T, et al: p53-dependent apoptosis modulates the cytotoxicity of anticancer agents. Cell 74:957-967, 1993[CrossRef][Medline]
22. Fan S, El-Deiry WS, Bae L, et al: p53 gene mutations are associated with decreased sensitivity of human lymphoma cells to DNA damaging agents. Cancer Res 54:5824-5830, 1994
23. O'Connor PM, Jackman J, Jondle D, et al: Role of the p53 tumor suppressor gene in cell cycle arrest and radiosensitivity of Burkitt's lymphoma cell lines. Cancer Res 53:4776-4780, 1993
24. Lowe SW, Bodos S, McClatchey A, et al: p53 status and the efficacy of cancer therapy in vivo. Science 266:807-810, 1994
25. Hawkins DS, Demers GW, Galloway DA: Inactivation of p53 enhances sensitivity to multiple chemotherapeutic agents. Cancer Res 56:892-898, 1996
26. Rowley M, Liu P, Van Ness B: Heterogeneity in therapeutic response of genetically altered myeloma cells to interleukin 7, dexamethasone, doxorubicin, and melphalan. Blood 96:3175-3180, 2000
27. Spanswick VJ, Craddock C, Sekhar M, et al: Repair of DNA interstrand cross-links as a mechanism of clinical resistance to melphalan in multiple myeloma. Blood 100:224-229, 2002
28. Esteller M, Garcia-Foncillas J, Andion E, et al: Inactivation of the DNA repair gene MGMT and the clinical response of gliomas to alkylating agents. N Engl J Med 343:1350-1354, 2000 29. Ozols RF, Hogan WM, Young RC: Direct cloning of human ovarian cancer in soft agar: Clinical limitations and pharmacologic applications. Recent Results Cancer Res 94:41-50, 1984[Medline] 30. Kaufmann M: Biochemical short-term predictive assay: Results of correlative trials in comparison to other assays. Recent Results Cancer Res 94:151-160, 1984[Medline]
31. Fichtinger-Schepman AM, van der Velde-Visser SD, van Dijk-Knijnenburg HC, et al: Kinetics of the formation and removal of cisplatin-DNA adducts in blood cells and tumor tissue of cancer patients receiving chemotherapy: Comparison with in vitro adduct formation. Cancer Res 50:7887-7894, 1990 32. Poirier MC, Reed E, Zwelling LA, et al: Polyclonal antibodies to quantitate cis-diamminedichloroplatinum(II)-DNA adducts in cancer patients and animal models. Environ Health Perspect 62:89-94, 1985[Medline] 33. Reed E, Yuspa SH, Zwelling LA, et al: Quantitation of cis-diamminedichloroplatinum(II) (Cisplatin)-DNA intrastrand adducts in testicular and ovarian cancer patients receiving cisplatin chemotherapy. J Clin Invest 77:545-550, 1986
34. Reed E, Ozols RF, Tarone R, et al: Platinum-DNA adducts in leukocyte DNA correlate with disease response in ovarian cancer patients receiving platinum-based chemotherapy. Proc Natl Acad Sci U S A 84:5024-5028, 1987
35. Souliotis VL, Boussiotis VA, Pangalis GA, et al: In vivo formation and repair of O6-methylguanine in human leukocyte DNA after intravenous exposure to dacarbazine. Carcinogenesis 12:285-288, 1991
36. Souliotis VL, Valavanis C, Boussiotis VA, et al: Comparative dosimetry of O6-methylguanine in humans and rodents treated with procarbazine. Carcinogenesis 15:1675-1680, 1994
37. Parker RJ, Gill I, Tarone R, et al: Platinum-DNA damage in leukocyte DNA of patients receiving carboplatin and cisplatin chemotherapy, measured by atomic absorption spectrometry. Carcinogenesis 12:1253-1258, 1991
38. Panasci L, Henderson D, Torres-Garcia SJ, et al: Transport, metabolism and DNA interaction of melphalan in lymphocytes from patients with chronic lymphocytic leukemia. Cancer Res 48:1972-1976, 1988
39. Zwelling L, Michaels S, Schwartz H, et al: DNA crosslinking as an indicator of sensitivity and resistance of L1210 leukaemia cells to cis-diamminedichloroplatinum (II) and L-phenylalanine mustard. Cancer Res 41:640-649, 1981 40. Sunters A, Springer CJ, Bagshawe KD, et al: The cytotoxicity, DNA crosslinking ability and DNA sequence selectivity of the aniline mustards melphalan, chlorambucil and 4-[bis (2-chloroethyl)amino]benzoic acid. Biochem Pharmacol 44:59-64, 1992[CrossRef][Medline]
41. Ferreira CG, Tolis C, Giaccone G, et al: p53 and chemosensitivity. Ann Oncol 10:1011-1021, 1999 Submitted November 28, 2004; accepted March 7, 2005.
This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|||||||||||
|
|||||||||||
|
|
Copyright © 2005 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
|
TOP
ABSTRACT
INTRODUCTION
