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A M Fichtinger-Schepman

Publications and source records attributed to A M Fichtinger-Schepman.

At least 37 records · Page 2Linked to original sources
PubMed1995

Cisplatin- and carboplatin-DNA adducts: is PT-AG the cytotoxic lesion?

In order to determine the nature of the cytotoxic lesion(s) formed by the antitumour drugs cisplatin and carboplatin, a comparative study was made of bifunctional DNA-adduct formation by these drugs. The kinetics of bifunctional cisplatin adduct formation were studied with DNA in vitro and in cultured Chinese hamster ovary (CHO) cells. Prior to adduct measurements with AAS in in vitro platinated DNA and with ELISA in cellular DNA, the monoadducts were inactivated with thiourea (10 mM; 1 h at 37 degrees C). The data indicated that the conversion of monofunctional to bifunctional adducts, with t1/2 of approximately 2 h (37 degrees C), leads to maximum intrastrand adduct levels after approximately 4-6 h postincubation. This interval coincided with the period during which the cytotoxic effect of cisplatin could be reduced by a 1 h 10 mM thiourea post-incubation of the cells. The formation of interstrand crosslinks continued for approximately 7 h of post-incubation; then these amounted to approximately 2% of the total DNA adducts. When a DNA sample was dialysed against 0.1 M NH4HCO3 (16 h, 37 degrees C) immediately after cisplatin treatment, in order to block mono- to bifunctional adduct conversion, adduct levels were found similar to those after the 4-6 h post-incubation. From this it is clear that the high values reported earlier for bifunctional cisplatin adducts in such DNA samples are not correct. These values apparently represent the amounts of adducts that eventually would have been formed during post-incubation in DNA in vitro but also in cells in the absence of cellular repair. The cisplatin data of CHO cells were compared with those after treatment of the cells with equitoxic doses of carboplatin. The data indicate that after 12 h post-incubation, when all bifunctional adducts are formed, the total amount of the various bifunctional adducts after cisplatin treatment (37.5 +/- 4.5 fmol/micrograms DNA) was in the same range as that after carboplatin (32.8 +/- 6.3 fmol/micrograms DNA). However, because the relative occurrences of the adducts were different, it could also be concluded that if one of the diadducts were exclusively responsible for the cytotoxic effect of these platinum antitumour drugs, Pt-AG is the only likely candidate.

Animals↗
PubMed1994

Deficient repair of cisplatin-DNA adducts identified in human testicular teratoma cell lines established from tumours from untreated patients.

Germ cell tumour lines appear generally more sensitive in vitro to cisplatin than other cultured cell lines, reflecting their clinical responsiveness. We proposed (Cancer Res 1988, 48, 3019-3024) that cisplatin hypersensitivity, expressed by a testicular teratoma line (SuSa), might be explained by an inability to repair platinated DNA. We have now quantitated cisplatin cytotoxicity by clonogenic assay, and platinum (Pt)-DNA adduct formation and removal immunochemically in four other testicular teratoma continuous cell lines (GCT46, GCT27 clone 4, H32 and H12.1), all established from tissue from non-drug-treated patients. For 1-h in vitro drug exposures, the cisplatin concentration required to reduce survival by 50% (IC50) ranged from 0.09 to 0.42 micrograms/ml (0.3-1.4 microM). Immediately following a 1-h exposure to 5 mu/ml cisplatin, total cellular platination levels ranged from 4.5 to 36.8 fmol Pt per microgram DNA, with lower platination occurring in the most sensitive lines. Following an 18-h post-treatment incubation period, the levels of the major cis-Pt-(NH3)2d(pGpG) (Pt-GG) adducts were not significantly reduced in any of the four lines, indicating a general deficiency in either the rate or extent of removal of these lesions. Deficient removal of the cis-Pt-(NH3)2d(pApG) adducts was also noted in two of the lines. DNA polymerase beta gene expression was comparable in all the tested testicular lines established from previously untreated patients, but markedly lower than that identified in the 833K testicular line, established from a drug-treated patient and identified earlier as proficient in Pt-GG adduct removal (Cancer Res 1988, 48, 3019-3024). Expression of the DNA excision repair genes ERCC-1 and XPBC/ERCC-3 was not significantly different in any of the five lines tested, including the 833K cell line. These data provide evidence of the apparent inability of testicular cell lines, derived from untreated tumours, to repair the major platinum-DNA intrastrand crosslinks, and so provide a biological basis for their hypersensitivity to cisplatin.

Cell Survival↗
PubMed1994

Differential formation and enhanced removal of specific cisplatin-DNA adducts in two cisplatin-selected resistant human testicular teratoma sublines.

Mechanisms of cisplatin resistance have been studied in two independently-selected sublines expressing clinically-relevant levels of resistance (3-fold) and established from a primary testicular teratoma obtained from previously untreated patients. Resistance was not associated with any significant modification in cellular uptake of cisplatin, in total glutathione levels or associated enzyme activities. However, immunochemical quantitation of specific platinum-DNA adduct formation and removal revealed that both resistant sublines were more proficient in repairing certain adducts than their generally repair deficient respective parental lines. SUSA/CP+ cells were more efficient in removing the intrastrand adducts in the sequence Pt-AG and the bi-functional Pt-(GMP)2 lesions, as well as DNA-DNA interstrand cross-links, whilst H12.1/DDP cells were highly proficient in removing the major Pt-GG intrastrand adducts.

Cisplatin↗
PubMed1993

Evidence of differential cisplatin-DNA adduct formation, removal and tolerance of DNA damage in three human lung carcinoma cell lines.

The expression of intrinsic resistance to cisplatin in two lung cancer cell lines, one derived from a small cell carcinoma (SW1271) and the other from an adenocarcinoma (A549), relative to a drug-sensitive small cell line SW900, was characterized by: (i) expression of cross-resistance to mitomycin C and cadmium chloride, but increased sensitivity to adriamycin and etoposide; (ii) significantly decreased cisplatin uptake; (iii) elevated levels of glutathione which could be reduced by buthionine L-sulfoximine resulting in significant sensitization of the cells to cisplatin; (iv) a lack of consistent modification of metallothionein content and expression of levels of glutathione S-transferase, glutathione reductase and glutathione peroxidase or of activities of DT-diaphorase or catalase; (v) significantly reduced total DNA-platination levels immediately following a 1 h cisplatin treatment with 10 micrograms/ml (33.3 microM); (vi) increased removal of Pt-GG and Pt-AG adducts by the A549 cells, consistent with increased repair capacity, but a lack of removal of these major adducts by the SW1271 cells indicative of tolerance of this drug-induced DNA damage. These data therefore provide evidence of differential formation, repair and tolerance of DNA damage following exposure of three human lung carcinoma cell lines to cisplatin.

Adenocarcinoma↗
PubMed1992

Characterization of a cisplatin-resistant human ovarian carcinoma cell line expressing cross-resistance to 5-fluorouracil but collateral sensitivity to methotrexate.

In vitro exposure of the TR170 ovarian carcinoma cell line to six intermittent 24-h treatments with a 90% inhibitory concentration of cisplatin (CDDP) (0.15 micrograms/ml; 0.5 microM) resulted in a 2-fold stably resistant subline designated TR170/CP+ (B.T. Hill et al., Int. J. Cancer, 39: 219-225, 1987). Resistance to CDDP in these CP+ cells has now been associated with reduced uptake of 195mCDDP (2-fold; P less than 0.01) and decreased removal of specific Pt-DNA adducts, quantitated immunochemically, indicative of an apparent increased tolerance of CDDP-induced DNA damage. Specifically these resistant cells appeared deficient in removal of the major cis-Pt-(NH3)2d(pGpG) adduct and the difunctional cis-Pt(NH3)2d(GMP)2 lesion, showed less efficiency in removing cis-Pt(NH3)2d(pApG) adducts, but proved as proficient as the parental cell line in removing DNA-DNA interstrand cross-links. Activities of DNA polymerase-alpha and -beta were comparable in both lines, and no significant alterations in glutathione metabolism were identified. Response to acute X-irradiation was not modified in these TR170/CP+ cells, but they showed marked (10-fold) cross-resistance to 5-fluorouracil and, unusually, proved collaterally sensitive (12-fold) to methotrexate. Resistance to 5-fluorouracil was associated with significantly increased thymidylate synthase activity (P less than 0.01), but this was not reflected in altered gene expression, while increased sensitivity to methotrexate was accompanied by increased drug uptake but by unaltered activity and expression of dihydrofolate reductase. These results indicate that exposure to CDDP can result in numerous alterations, both intracellularly and at the cellular membrane, reflected in significant changes in the tumor cells' responses to the cytotoxic effects of a range of antitumor drugs. The clinical relevance of these observations remains to be established.

Antineoplastic Agents↗
PubMed1992

Effects of the modulating agent WR2721 and its main metabolites on the formation and stability of cisplatin-DNA adducts in vitro in comparison to the effects of thiosulphate and diethyldithiocarbamate.

The influence of the modulating agent WR2721, its active thiol-metabolite WR1065 and the symmetrical disulphide WR33278 on the in vitro formation and stability of cis-diamminedichloroplatinum(II) (cisplatin, CDDP)-DNA adducts was investigated and compared with the effects of the highly nucleophilic modulating agents diethyldithiocarbamate (DDTC) and thiosulphate (TS). Salmon sperm DNA (0.5 mg/mL) was incubated with 25 micrograms/mL (83 microM) cisplatin for 1 hr in 50 mM phosphate buffer, pH 7.2 at 37 degrees in the absence or presence of modulating agent. DDTC and TS were potent inhibitors of the platination of the DNA (95 and 89%, respectively, with 4.2 mM of modulating agent). The WR-compounds were also remarkably active in the inhibition of DNA platination. Prevention of adduct formation in the presence of 4.2 mM WR-compound decreased in the order WR1065 (74%) greater than WR33278 (63%) greater than WR2721 (51%). The prevention of CDDP-DNA adduct formation by WR1065 was strongly concentration-dependent up to 4.2 mM but at higher concentrations this protection hardly increased at all. In the presence of the modulating agents, increased levels of CDDP monofunctionally bound to a guanine residue were observed with a simultaneous decrease in the relative abundance of bifunctional adducts. All modulators were also able to reverse part of the CDDP-DNA adducts formed. After a 2-hr incubation of already platinated salmon sperm DNA with 4.2 mM of modulating agent, the removal of Pt from DNA amounted to about 43% with DDTC, 28% with WR1065 and 13-14% with TS, WR2721 and WR33278. Even CDDP bifunctionally bound to two adjacent guanines in the same DNA strand, which is considered to be a very stable adduct, was partly reversed. Our observations suggest that WR2721, especially when administered prior to or concomitantly with CDDP, can be expected to protect those tissues from CDDP-induced damage to DNA that are able to efficiently dephosphorylate WR2721 followed by uptake of the thiol metabolite WR1065. This stresses the importance of a selective formation and uptake of WR1065 by non-tumour tissues for the successful use of WR2721 as a protective agent in combination with platinum-based cancer chemotherapy.

Amifostine↗
PubMed1992

Mechanisms associated with the expression of cisplatin resistance in a human ovarian tumor cell line following exposure to fractionated X-irradiation in vitro.

Interactions between cisplatin (CDDP) and irradiation are of potential significance for the combined modality treatment of cancer. Previous data have indicated that following in vitro exposure to X-irradiation certain tumour cells expressed resistance to CDDP. To identify parameters associated with this CDDP resistance, the human ovarian carcinoma cell line SK-OV-3/P was pre-exposed to fractionated X-irradiation (total dose: 50 Gy) in vitro. The resultant subline (SK-OV-3/DKR-10) proved 2-fold resistant to CDDP, but not to acute X-irradiation. Consistent with unaltered dihydrofolate reductase and thymidylate synthase activities, SK-OV-3/DXR-10 cells were neither cross-resistant to methotrexate nor to 5-fluorouracil. Verapamil (6.6 microM) significantly (P less than 0.05) enhanced CDDP-induced cytotoxicity in the resistant DXR-10 subline, but not in the parental cells. Total glutathione levels were significantly (P less than 0.01) lower in the resistant subline and BSO pretreatment failed to influence cytotoxicity, whilst related enzyme activities were not consistently modified in the SK-OV-3/DXR-10 cells. Resistance in these cells was associated with significantly decreased cisplatin uptake (P less than 0.002). Immediately following drug exposure the total platination level of the DNA, quantitated immunochemically, was higher (P less than 0.05) in the resistant subline indicative of increased tolerance to DNA damage. After an 18 h post-treatment incubation the parental cell line appeared proficient in the removal of the intrastrand adduct Pt-AG, but deficient in removing the major adduct Pt-GG and the difunctional Pt-(GMP)2 lesion, whilst the DXR-10 resistant subline appeared proficient in removal of all four Pt-DNA adducts. DNA polymerases alpha and beta activities, however, were comparable in both cell lines. These data implicate both enhanced repair and increased tolerance of DNA damage as mechanisms of resistance to CDDP resulting from in vitro exposure of a human ovarian carcinoma cell line to fractionated X-irradiation.

Biological Transport↗
PubMed1991

Resistance patterns between cis-diamminedichloroplatinum(II) and ionizing radiation.

Cross-resistance between cis-diamminedichloroplatinum(II) (CDDP) and radiation resistance has been suggested from clinical and experimental data (C. T. Coughlin and R. C. Richmond, Semin. Oncol., 16: 31-43, 1989). To determine whether cross-resistance patterns between both cytotoxic approaches exist, resistance against CDDP and ionizing radiation was induced separately in human ovarian cancer cells in a cross-over design. Subsequently sensitivity changes were determined for both treatment modalities. CDDP resistance was induced previously (P. J. Kuppen et al., Cancer Res., 48: 3355-3359, 1988), and resistant cells were grown at three different levels of CDDP:0 ng/ml; 250 ng/ml; and 500 ng/ml. Resistance with resistance factor (RF) 3.4 to 5.1 proved to be stable, since withdrawal of CDDP pressure for at least 6 mo did not alter resistance patterns. CDDP-resistant cells also demonstrated stable resistance against ionizing radiation, with RF ranging from 1.7 to 2.0. The resistance patterns could not be explained by differences in growth kinetics and DNA content. Resistance to ionizing radiation was induced in the same human ovarian cancer cells as used for CDDP resistance studies. Exposure with 1.5 Gy of intermittent irradiation during 6 mo, at time intervals of 48 h, resulted in cells which were able to grow under chronic ionizing radiation pressure. RF was 2.0; the resistance was lost after 6 mo of culturing without ionizing radiation pressure. With intermittent radiation doses of 0.5 and 1.0 Gy, no significant resistance could be induced. Cells intermittently exposed to 0.5, 1.0, and 1.5 Gy during 6 mo demonstrated increased sensitivity to CDDP, with 0.22 less than RF less than 0.43. Increased sensitivity was associated with proportionally increased formation of the platinum-DNA adducts. Differences in sensitivity for both ionizing radiation and CDDP were lost after 6 mo of culturing without radiation pressure; therefore, resistance toward ionizing radiation and, likewise, the increased sensitivity to CDDP, were judged to be unstable. In conclusion, data of the present study demonstrated that development of stable resistance to CDDP is associated with development of stable resistance to ionizing radiation in human ovarian cancer. Contrastingly, increased sensitivity to CDDP was found when resistance against irradiation was induced in the same cells.

Cell Survival↗
PubMed1991

Comparative study of two human melanoma cell lines with different sensitivities to mustine and cisplatin.

The cytotoxic effects of the bifunctional DNA-reactive drugs cisplatin, mustine and melphalan were studied in two human melanoma cell lines, RPMI 8322 and A 375. A 375 cells were 3.0 times more sensitive to cisplatin and 1.5 times more sensitive to mustine than RPMI 8322 cells. In contrast, A 375 cells were less sensitive to melphalan than RPMI 8322 cells. The increased sensitivity of A 375 cells was parallelled by an increased induction of DNA interstrand crosslinks following exposure to cisplatin and mustine. After cisplatin exposure A 375 cells also showed higher levels of platinum-DNA intrastrand adducts than RPMI 8322 cells. The increased effect of cisplatin in A 375 cells was not due to an increased drug accumulation in these cells. The higher sensitivity of A 375 cells to cisplatin may be related to lower intranuclear levels of glutathione, compared to RPMI 8322 cell nuclei, while the sensitivity to mustine may depend on lower overall levels of glutathione than in RPMI 8322 cells.

Cell Line↗
PubMed1991

Lack of significant modulation of the formation and removal of platinum-DNA adducts by aphidicolin glycinate in two logarithmically-growing ovarian tumour cell lines in vitro.

Two recently established human ovarian carcinoma cell lines (JA-T and TR175) have been used to study the effects of aphidicolin glycinate (APG), a specific competitive inhibitor of DNA polymerase alpha (Ikegani et al. (1978) Nature, 275, 458-460), on the formation and removal of four platinum-DNA adducts. Logarithmically-growing cells were exposed to cis-diamminedichloroplatinum (II) (cisplatin) (10 micrograms, 33.4 microM) in the presence or absence of APG (5 or 50 micrograms/ml, 11.6 or 116 microM). Platinum-DNA adducts were quantitated using a competitive ELISA technique. No differences were observed between the initial levels of total DNA platination and of specific DNA adducts formed in the presence or absence of APG in either cell line. Following 18 h posttreatment incubation both lines showed some ability to remove each of the three main platinum-DNA lesions (Pt-GMP, Pt-AG and Pt-GG). However, the levels of these specific DNA adducts decreased over this time period, by similar rates with or without APG addition. It was also shown that the APG concentrations used had minimal inhibitory effects alone on growth or DNA synthesis during this 18 h posttreatment incubation period. Furthermore its addition did not significantly modify cisplatin-induced cytotoxicity, as judged by inhibition of growth or DNA synthesis over this time period. We therefore conclude that under these experimental conditions APG does not modulate 'repair' of cisplatin-induced DNA damage in logarithmically-growing cultures of these two apparently 'repair-proficient' human ovarian tumour cell lines.

Antibiotics, Antineoplastic↗
PubMed1990

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.

During chemotherapy with a cisplatin-containing combination of drugs, 217 blood samples from 30 cancer patients were analyzed for the presence of the main cisplatin-DNA adduct cis-Pt(NH3)2d(pGpG) (Pt-GG). Cisplatin was administered during 3-h infusions on each of 5 consecutive days, resulting in increasing adduct levels which, on the average, were about twice as high after the fifth as after the first infusion. Higher levels were found in blood samples of patients who received the same total amount of cisplatin in one single 3-h infusion. No significant differences in adduct levels were found during first and repeated courses. The nonlinear dependence of adduct levels on total dose can be attributed to removal of adducts. At 21 h after a very first cisplatin infusion 76% of the adducts were removed. Lower percentages of removal were observed over the 21-h periods following the fourth and fifth infusions of 5-day courses (49 and 53%, respectively). After the initial 21 h the removal of adducts continued, albeit at a slower rate. Substantial interindividual variation was found in the adduct levels, which did correlate with the levels obtained after in vitro cisplatin treatment of blood samples from the same patients but not with their age or gender. Testicular cancer patients with complete tumor response showed higher adduct levels in their blood than those with partial response or progressive disease. When blood samples from 8 healthy volunteers were treated with cisplatin in vitro, the person-to-person variation in adduct levels and the intraindividual variation observed over a 2-year period were found to be in the same range, which was narrower than that observed with samples from treated patients. In vitro studies with human blood showed that the formation of the Pt-GG adduct is proportional to cisplatin concentration and complete after about 1 hour. In some of the in vivo and in vitro cisplatin-treated blood samples, all 4 known platinum-DNA adducts were determined. In all cases Pt-GG was by far the major adduct, and no significant differences were observed with respect to the relative amounts of the 4 adducts. Similar adduct ratios were found in DNA from a testicular tumor obtained from a patient who underwent orchidectomy; the Pt-GG adduct level was about 10-fold higher than that in his blood cells.

Adult↗
PubMed1990

Enhanced DNA repair and tolerance of DNA damage associated with resistance to cis-diammine-dichloroplatinum (II) after in vitro exposure of a human teratoma cell line to fractionated X-irradiation.

In vitro exposure of a human testicular teratoma continuous cell line to fractionated X-irradiation resulted in the expression of resistance to cisplatin. In two independently-derived sublines, designated SUSA-DXR13 and SUSA-DXR10 resulting from treatment with either 13 fractions of 1.5 Gy (dose required to reduce survival by 1 log) or 10 fractions of 3 Gy (dose required to reduce survival by 2 logs) respectively, the IC50 values for cisplatin were 2- and 3.1-fold higher than that of the parental cell line. These sublines were cross-resistant to carboplatin (approximately 2-fold) but not to adriamycin and they showed unaltered radiosensitivities. The SUSA-DXR10 subline expressed some cross-resistance to mitomycin C and melphalan but none to Carmustine (BCNU). Total glutathione content was significantly reduced in both SUSA-DXR10 and SUSA-DXR13 cells, but the activities of associated enzymes, including the glutathione S-transferases, peroxidase and reductase were not modified significantly in the resistant sublines. Resistance in the SUSA-DXR10 subline was associated with significantly decreased 195mcisplatin uptake (p less than 0.01), but this was not reflected in a reduced level of drug bound to the DNA. The formation and removal of four platinum-DNA adducts were immunochemically quantitated. Immediately following drug treatment there was a higher level of total platination of the DNA in the resistant subline indicative of increased tolerance to DNA damage. After an 18 hr post treatment incubation, there was an indication of some repair capacity in this SUSA-DXR10 cell line, which was not apparent in the parental cells. Neither the parental nor the SUSA-DXR10 cell line was proficient in the repair of the major adduct Pt-GG, whereas both lines repaired the monofunctional adduct and the adduct Pt(GMP)2. SUSA-DXR10 cells were also able to repair the intrastrand adduct Pt-AG and interstrand crosslinks, unlike the repair deficient parental cells. Higher levels of interstrand crosslinks were characteristic of the SUSA-DXR10 subline. These observations therefore implicate both enhanced repair and increased tolerance of DNA damage as mechanisms of resistance to cisplatin resulting from in vitro exposure of a human teratoma cell line to fractionated X-irradiation.

Cisplatin↗
PubMed1989

Platinum concentrations and DNA adduct levels in tumors and organs of cisplatin-treated LOU/M rats inoculated with cisplatin-sensitive or -resistant immunoglobulin M immunocytoma.

Female LOU/M rats, bearing either a cisplatin (cisDDP)-sensitive or -resistant IgM immunocytoma, were sacrificed at 1 or 24 h after cisDDP administration (i.v., 10 mg/kg of body weight). Platinum levels, determined with atomic absorption spectroscopy, were in the order kidney much greater than liver greater than tumor greater than spleen in the 1-h samples. In the 24-h samples, more platinum was found in spleens than in tumors; the levels in the kidneys were the same as those measured at 1 h, in the spleens they were higher, and in livers and tumors they were lower than at 1 h after the injection; the greatest decrease occurred in the resistant tumor. cisDDP-DNA adducts were detected after chromatography of digested DNA samples isolated from these tissues and from blood cells. The quantitation of the four cisDDP-DNA adducts (Pt-G, Pt-AG, Pt-GG, G-Pt-G, the same as found previously in cisDDP-reacted DNA) was performed with specific antibodies, in the competitive enzyme-linked immunosorbent assay. The cisDDP-DNA adduct levels in the various 1-h tissue samples showed the same ranking order as the platinum levels. The blood samples contained the lowest amount of adducts. Because of the high platinum level in the kidneys (26 mg/kg of wet tissue), the adducts in this organ also could be determined with atomic absorption spectroscopy (the four adducts comprised about 400 fmol/micrograms of DNA). Comparison of the atomic absorption spectroscopy and enzyme-linked immunosorbent assay data showed excellent agreement. Except for the kidney, all samples showed a decrease in adduct level between 1 and 24 h after cisDDP treatment. The data on the tumors indicated that the difference in susceptibility to cisDDP between the sensitive and resistant tumors is not due to a decreased platinum content or reduced DNA adduct formation in the resistant tumor.

Animals↗
PubMed1989

Influence of the degree of DNA modification on the immunochemical determination of cisplatin-DNA adduct levels.

Two different enzyme-linked immunosorbent assays (ELISAs) are used for the sensitive determination of cisplatin-DNA adducts in, for example, blood cells of cisplatin-treated cancer patients. Poirier et al. determined the adducts in native DNA with an antiserum raised against highly modified cisplatin-DNA. Fichtinger-Schepman et al. assayed the various adducts after chromatography of enzymatically digested DNA samples, with antibodies raised against synthetic haptens mimicking the Pt-containing digestion products. In identical human samples analysed by both methods, 14- to 300-fold higher adduct levels were found with the Fichtinger-Schepman method. Adduct levels in organ samples of cisplatin-treated rats and mice allowed comparison of both ELISAs with independent Pt assays (atomic absorption spectroscopy, AAS). AAS data confirmed the results of the Fichtinger-Schepman assay, whereas ELISAs according to Poirier showed differences up to a factor of 1000. Analysis of cisplatin adducts in in vitro modified DNA revealed that the Poirier antibodies yield correct estimates with highly modified DNA, but fall short at low platination levels: no adducts could be detected in samples modified to a level similar to that found in blood cells from cisplatin-treated patients. The positive responses obtained with samples of such patients, who had been treated repeatedly, might be explained if cisplatin adducts are preferentially formed around persistent lesions from the previous treatments.

Animals↗