Design and testing of a new cisplatin form using a base material by combining poly-D,L-lactic acid and polyethylene glycol acid against peritoneal metastasis

Microspheres containing cisplatin (CDDP) embedded in poly-d,l-lactic acid (PLA) and polyethylene glycol acid (CDDP-PPMS) were developed to improve treatment of malignant effusions. In vitro studies demonstrated that CDDP was released continuously for more than 4 weeks from CDDP-PPMS without initial burst. CDDP-PPMS was compared with CDDP aqueous solution (CDDP-SOL) by i.p. administration in rats for 1) tissue distribution, 2) toxicity and 3) therapeutic effects against Yoshida sarcoma. We found that the CDDP concentration in the omentum was maintained at a higher level than in the CDDP-SOL group, while the particles of CDDP-PPMS were observed in the stomata of the omentum by electron microscopy. Concentrations of CDDP in the lung, liver, kidney and blood were lower in the CDDP-PPMS group than in the CDDP-SOL group. All rats given CDDP-PPMS containing < or = 28 mg/kg were alive, whereas in the CDDP-SOL group, all rats given > or = 16 mg/kg died from side effects. The LD50 of CDDP-PPMS and CDDP-SOL were 32.8 and 14.8 mg/kg, respectively. The survival of rats with peritoneal metastasis was better in the CDDP-PPMS group than in the CDDP-SOL group.

Establishment and characterization of an acquired cisplatin-resistant subline in a human osteosarcoma cell line

A cisplatin (CDDP)-resistant human osteosarcoma cell line (OST/R) was established by continuous exposure to CDDP. OST/R cells proved to be 6.73 times more resistant to CDDP compared with parental OST cells, and showed cross-resistance to carboplatin (CBDCA). The mechanism of CDDP resistance was a significant decrease of intracellular platinum accumulation which was 40% of that in OST cells. OST/R cells were exposed to CDDP for 6 hours, the platinum was released from the cytoplasm of OST/R cells without reaching a state of equilibrium. DNA synthesis in OST/R cells was not inhibited by CDDP exposure, while in OST cells it was reduced by 50%. These data provide the first evidence that the increased efflux of platinum may play an important role in CDDP-resistance.

Monte Carlo methods for the in vivo analysis of cisplatin using X-ray fluorescence

A Monte Carlo method has been used to model the measurement of cisplatin uptake with in vivo X-ray fluorescence. A user-code has been written for the EGS4 Monte Carlo system that incorporates linear polarisation and multiple element fluorescence extensions. The yield of fluorescent photons to the mainly Compton scattered background is computed for our detector arrangement. The detector consists of a mutually orthogonal arrangement of X-ray tube, aluminium polariser and high purity germanium scintillation detector. The influence of tube voltage on the minimum detectable concentration is modelled for 100 through 150 kVp X-radiation. The code is able to predict absorbed dose to the patient which will influence the optimal choice of tube voltage. The influence of alterations to collimator design and scatterer construction can also be examined. A minimum detectable concentration of 50 ppm is determined from measurements with a 115 kVp X-ray source and a 615 ppm cisplatin sample in a water phantom.

Rat tibial nerve regeneration after postoperative administration of cis-diaminedichloroplatinum

We investigated the results of postoperative administration of cis-diaminedichloroplatinum on nerve regeneration in rats. Forty-two Lewis rats were divided into two groups, receiving end-to-end suture or nerve grafting. Subgroups of the suture group included control, a one-time dose of cis-diaminedichloroplatinum (3 mg/kg), and four doses of the same amount of cis-diaminedichloroplatinum. Subgroups in the nerve grafting group included a control and a four-dose group. Functional recovery was measured by gait analysis using the tibial function index. Biopsies of nerve were taken distal to the suture site for histologic evaluation 20 weeks postoperatively. Tibial function index at 4, 6, and 20 postoperative weeks in the four-dose group was significantly inferior to that of the control group in the suture group. Tibial function index was inferior in the four-dose group until 10 weeks postoperatively compared with control in the nerve grafting group; however, there was no significant difference. The percentage of neural tissue in the one-dose suture group was significantly greater than in the four-dose suture group. These results suggest that postoperative cis-diaminedichloroplatinum administration may have a detrimental effect on nerve regeneration.

Hydration regimen and hematological toxicity of a cisplatin-based chemotherapy regimen. Clinical observations and pharmacokinetic analysis

The administration of 100 mg/m2 Cisplatin (CDDP) in five 20 mg/m2 daily infusions together with bolus 5-Fluorouracil (5FU) allows patients with advanced head and neck cancer (HNC) to be treated with a rapidly alternating chemoradiotherapy regimen in an out-patient setting. Due to the extremely low rate of acute renal failure, the induction of forced diuresis is not mandatory, although hydration is usually performed at every CDDP administration. In this retrospective analysis of 73 homogenously treated HNC patients, the influence of hydration on hematological toxicity was studied. A lower incidence of grade II to IV acute myelosuppression (57% vs 92%; p < 0.005), together with a lower rate of anemia lasting two weeks or more (13% vs 46%; p < 0.009), were seen in the group of patients treated with CDDP along with a forced hydration scheme (2000 ml normal saline and 20 mg furosemide before the CDDP infusion) when compared to patients on a non-forced diuresis regimen (no furosemide and 1500 ml normal saline). The lower hematological toxicity translated into a better compliance to treatment. No differences in terms of other toxicities or response rate were evident between the two groups. A pharmacokinetic study with a cross over design was performed on 7 patients, and suggests that the first day Pt kinetics are not affected by the hydration scheme used, although a significantly lower Pt urinary concentration was found in the forced diuresis group. A further kinetic analysis performed on one additional patient over the entire five-day period of two consecutive cycles showed a marked increase in the AUC of filterable Pt and in the unbound Pt fraction (fu) from the second to the fifth day in the forced hydration course, while this was not the case in the non-forced hydration course. Results from this kinetic study support the hypothesis of a lowering of Pt reactive species after repeated CDDP-furosemide treatments and an influence of furosemide-induced diuresis on Pt binding to plasma proteins.

Pharmacokinetics of cisplatin in combined cisplatin and 5-fluorouracil therapy: a comparative study of three different schedules of cisplatin administration

BACKGROUND

Cisplatin is widely used in combination chemotherapy against a variety of tumors; however, the optimal administration schedule of cisplatin is still controversial. To clarify the pharmacokinetic differences according to the administration schedules of cisplatin, we compared three different administration schedules of cisplatin such as single short-term infusion, daily short-term infusion and daily continuous infusion in combination with 5-fluorouracil. Preliminary clinical responses and toxicities were also investigated.

METHODS

A total of 12 courses in combination of cisplatin and 5-fluorouracil therapy was studied. The schedules of cisplatin tested were as follows: single short-term infusion (80 mg/m2, day 1,2 h div., n = 4), daily short-term infusion (20 mg/m2, days 1 to 5, 2 h div., n = 4), daily continuous infusion (100 mg/m2, 120 h, n = 4). In all schedules, 5-fluorouracil was continuously administered at a dose of 800 mg/m2/day on days 1 to 5. The area under the time-concentration curve (AUC) and the maximum concentration (Cmax) of total and free Pt were investigated.

RESULTS

The highest AUC of total and free Pt and the lowest Cmax of free Pt were observed in the daily continuous infusion (total AUC; 162.53 +/- 18.39 micrograms h/ml, free AUC; 5.50 +/- 0.9 micrograms h/ml, free Cmax; 0.07 +/- 0.01 microgram/ml, mean +/- SEM). Two patients in the single short-term infusion and one patient in the daily continuous infusion indicated partial responses clinically. No nephrotoxicity or ototoxicity was observed. All toxicities were mild and tolerable in all regimens; however, the incidence of GI toxicity in daily continuous infusion seemed to be relatively higher.

CONCLUSIONS

Daily continuous infusion of cisplatin gave the best pharmacokinetic results and to evaluate the clinical advantage of this schedule a prospective randomized trial should be conducted with sufficient numbers of patients.

Role of thromboxane receptor on the intracellular accumulation of cis-diamminedichloroplatinum(II) in non-small-cell but not in small-cell lung cancer cell lines

cis-Diamminedichloroplatinum(II) (CDDP) is a key anticancer agent. It has been reported that intracellular accumulation of CDDP is an important step as a determinant for resistance to CDDP, which may be modulated by Na+, K(+)-ATPase activity. In this study, the significance of membrane Na+, K(+)-ATPase activity and the role of thromboxane (TX) receptors were evaluated using human lung cancer cell lines. In the non-small-cell lung cancer (NSCLC) cell line, EBC-1, sensitivity to CDDP was improved by treatment with two different selective thromboxane receptor antagonists, calcium 5(z)-[1R,2S,3S,4S-7-[3-phenylsulfonylaminobicyclo [2.2.1]hept-2-yl]-5-heptenoate hydrate (S-1452), and (3R)-3-(4-fluorophenyl sulfonamido)-1,2,3,4-tetrahydro-9-carbazolepropanoic acid (BAYu3405). Na+, K(+)-ATPase was activated and intracellular accumulation of CDDP increased with treatment in EBC-1. In the small-cell lung cancer (SCLC) cell lines, SBC-1, sensitivity to CDDP and Na+, K(+)-ATPase activity did not change significantly, and intracellular accumulation of CDDP was not modulated. These results suggest the importance of the TX receptors as determinants of the sensitivity to CDDP in NSCLC cell lines. However, Na+, K(+)-ATPase activity and the role of TX receptors may not be so significant in the resistance mechanisms to CDDP in SCLC cell lines. In EBC-1 cells, the specific binding of S-145 was evident, but not in SBC-1 cells. The difference in TX receptors in NSCLC and SCLC cell lines may be one of the reasons for the variety of the antitumor effects of CDDP in chemotherapy for lung cancer.

[Design and application of oral sustained-release anticancer drug--a new oral dosage form of cisplatin]

As compared to the conventional standard chemotherapy of solid cancer such as lung, biochemical modulation (BCM) therapy has been proven to have a good therapeutic efficiency. BCM therapy uses the low dose and low infusion rate of anti-cancer drug. To increase of the QOL of cancer patients, oral BCM therapy is needed. For this purpose, two kinds of new oral sustained-release cisplatin preparations were developed, micro-porous CDDP capsule made of ethylcellulose(EC) and CDDP-EC-stearic acid solid dispersion. After oral administrations of these preparations, serum CDDP levels were maintained over 0.2 microgram/ml for 24h. Experimental therapy using P815 tumor cells transplanted mice suggested the usefulness of CDDP solid dispersion preparation.

The effect of dexamethasone on the uptake of cisplatin in 9L glioma and the area of brain around tumor

The negative influence of dexamethasone (Dex) on the uptake of cisplatin in brain tumors was investigated in rats bearing 9L glioma. Dex or saline was given intraperitoneally prior to intravenous administration of cisplatin 5 mg/kg. Total Platinum (Pt) concentration was quantified with atomic absorption spectroscopy (AAS) in tumor, brain around tumor (BAT), normal brain and plasma. In the second experiment DNA-adducts of cisplatin were determined in tumor and BAT by AAS. In tumor, there was no difference in the Pt concentration and in the DNA-adduct level between the two treatment groups. In BAT, the Pt level in the Dex group was 0.20 microg/g (SD=0.10 microg/g), which was significantly lower than in the controls (0.53 microg/g (SD=0.21 microg/g); p < 0.001). In addition, the DNA-adduct level in BAT was 23% lower in the Dex treated rats (p=0.05). In normal brain the Pt concentration was 10-fold lower than in tumor tissue. Thus, Dex did not significantly limit the uptake of cisplatin in brain tumor nor did it influence the uptake in normal brain parenchyma. In contrast, in BAT that has a partially disrupted BBB, the concentrations of Pt and DNA-adduct formation were significantly decreased following pretreatment with Dex. The influence of Dex on limiting the effects of chemotherapy for brain tumors needs further study.

Rat liver transport and biotransformation of a cytostatic complex of bis-cholylglycinate and platinum (II)

BACKGROUND/AIMS

Bile acids have previously been used as shuttles for directing organic drugs to the liver. The aim of this study was to investigate liver transport and biotransformation of a new cytostatic bioinorganic complex (Bamet-H2), that was obtained by binding platinum(II) to two cholylglycinate moieties.

METHODS

Using rat hepatocytes in primary culture, the kinetics of cholylglycinate, cisplatin and Bamet-H2 uptake were studied. Sodium-dependency of Bamet-H2 uptake was investigated by replacement of 116 mM NaCl by 116 mM choline chloride. Liver biotransformation was investigated by HPLC analysis of bile samples collected from anesthetized rats following intravenous Bamet-H2 administration. Using isolated rat liver preparations, which were perfused with erythrocyte- and albumin-free Krebs-Henseleit solutions for 40 min, measurement of cholylglycinate, cisplatin and Bamet-H2 uptake and bile output was carried out. Interaction between Bamet-H2 and cholylglycinate for liver transport was studied by co-administration of 1 microM Bamet-H2 plus 500 microM cholylglycinate and 1 microM [14C]-cholylglycinate plus 500 microM Bamet-H2.

RESULTS

Both cholylglycinate and Bamet-H2 uptake by rat hepatocytes followed saturation kinetics. Comparison between the two compounds indicated that the Vmax (22.2 versus 8.5 nmol.5 min(-1).mg protein(-1)), and Kt (365 versus 171 microM) were higher for Bamet-H2 uptake. The efficiency of Bamet-H2 uptake (Vmax/Kt) was significantly reduced (-35%) in the absence of sodium. Cisplatin uptake by rat hepatocytes was approximately 10-fold lower than that for Bamet-H2 at any dose used. Moreover, this was not saturable up to 400 microM cisplatin. Bamet-H2 was not biotransformed during its intrahepatic residence in anesthetized rats. Bamet-H2 uptake and secretion into bile by isolated rat livers exceeded cisplatin but were less than cholylglycinate. Differences between Bamet-H2 and cholylglycinate were more marked for bile output than for liver uptake. Thus, higher drug liver content was found after perfusion with Bamet-H2 than with cholylglycinate or cisplatin. Co-administration of Bamet-H2 and cholylglycinate revealed the existence of partial cross-inhibition in both liver uptake and bile output. Bamet-H2 induced a more profound alteration on cholylglycinate uptake and bile secretion than cholylglycinate on both process for Bamet-H2.

CONCLUSION

These results suggest that in the transfer of Bamet-H2 from the sinusoids to the canaliculi both bile acid and non-bile acid transport systems are involved.

Significance of Na+, K(+)-ATPase on intracellular accumulation of cis-diamminedichloroplatinum(II) in human non-small-cell but not in small-cell lung cancer cell lines

cis-Diamminedichloroplatinum(II) (CDDP) is the most active anticancer agent. It has been reported that intracellular accumulation of CDDP is an important step as a determinant for resistance to CDDP, which may be modulated by Na+, K(+)-ATPase activity. In this study, the significance of membrane Na+, K(+)-ATPase activity in the intracellular accumulation of CDDP were evaluated using human lung cancer cell lines. Na+, K(+)-ATPase was active in each cell line, not only non-small-cell lung cancer (NSCLC) but also in small-cell lung cancer (SCLC) cell lines. In NSCLC cell lines, there were significant correlations between Na+, K(+)-ATPase activities and intracellular accumulation of CDDP and the accumulation significantly decreased by ouabain, an inhibitor of Na+, K(+)-ATPase in each cell line. However, the correlation between enzyme activity and intracellular accumulation of CDDP were not significant in SCLC cell lines where sensitivity to CDDP was better than in NSCLC cell lines. These results suggest Na+, K(+)-ATPase are active in both NSCLC and SCLC cells, however, the importance of the enzyme as an active transporter of CDDP may be limited only to NSCLC cells. The mechanisms of intracellular accumulation may not be so important as a determinant of sensitivity to CDDP in SCLC cells.

Influence of amifostine on the pharmacokinetics of cisplatin in cancer patients

The pharmacokinetics of cisplatin was investigated in 13 patients receiving 18 courses of cisplatin alone or in combination with amifostine to investigate the influence of amifostine (WR 2721; Ethyol) on the pharmacokinetics of cisplatin. Cisplatin was administered as a 1-h i.v. infusion, whereas amifostine was given i.v. over 15 min just before the cisplatin infusion. An increase in the final half-life of ultrafilterable platinum was observed after treatment with cisplatin and amifostine (t1/2, 0.77 +/- 0.10 h; n = 8), compared to cisplatin alone (t1/2, 0.57 +/- 0.15 h; n = 8). This might be caused by an influence of amifostine on the kidney function, because an increase in the serum creatinine levels was also observed 24 h after treatment with cisplatin and amifostine (13.8 +/- 12.6%; n = 9), which was not observed after treatment with cisplatin alone (-0.1 +/- 6.8%; n = 9). Surprisingly, the final half-life of unchanged cisplatin did not increase, but even showed a slight decrease after treatment with amifostine. In vitro data would suggest that this might be due to a chemical interaction between cisplatin and amifostine. Because the AUC values of ultrafilterable platinum and unchanged cisplatin did not change significantly and no change in Pt-DNA adduct (Pt-GG) levels in leukocytes was observed upon addition of amifostine in the treatment schedule, the change in the pharmacokinetics of cisplatin is most probably of minor importance and has no significant impact on the efficacy of cisplatin, as already confirmed by clinical studies.

Pharmacokinetics of cisplatin with and without amifostine in tumour-bearing nude mice

Amifostine (Ethyol, WR-2721) is in use in the clinic as a protector against platinum-induced toxicities. We have previously reported that amifostine induced a potentiation of the antitumour activity of carboplatin in human ovarian cancer xenografts. An influence of amifostine on the pharmacokinetics of carboplatin, resulting in higher platinum concentrations in plasma and tissues of the tumour-bearing nude mice, was thought to be the cause of enhancement of the antitumour activity. Therefore, the pharmacokinetics of cisplatin were investigated in tumour-bearing nude mice treated with cisplatin alone or in combination with amifostine. A significant increase in the area under the curve (AUC) of the total platinum concentration in mice treated with amifostine was only observed in the kidney (from 355 to 398 nmol h/g), whereas in the other tissues and plasma no significant changes were measured. The selective protection of normal tissues by amifostine was confirmed by a decrease in the AUC of the cisplatin-DNA adduct levels in normal tissues. The decrease was only significant in the liver (282-240 fmol h/microgram DNA), whereas in tumour tissue a slight increase in the AUC of the cisplatin-DNA adducts could be detected (91.3-110.1 fmol h/microgram DNA). The minor influence of amifostine on the pharmacokinetics of cisplatin may be the reason why amifostine did not potentiate the antitumour activity of cisplatin. The influence of amifostine on cisplatin-DNA adduct levels in normal tissues versus tumour tissues is further evidence for the usefulness of this toxicity modulator in cancer patients.

Distribution of platinum in human gynecologic tissues and pelvic lymph nodes after administration of cisplatin

BACKGROUND

Defining tissue accumulation of platinum may be of importance, since it may provide a pharmacological explanation for organ-specific cisplatin activity. This study was conducted to evaluate the efficacy of cisplatin at the tissue level in different gynecologic organs. The doses administered were equivalent to those used in neoadjuvant chemotherapy regimens.

STUDY DESIGN

Cisplatin was administered intravenously to patients with cervical or endometrial cancer 1 h before operation, and platinum accumulations in tissues were assayed by the atomic absorption method.

RESULTS

Platinum accumulation was highest in the cervix and next highest in the myometrium in both cancers. Platinum accumulation in ovary and lymph node was only 0.58 and 0.57 times that in the myometrium, respectively. In patients with cervical cancer, the platinum accumulations in the myometrium and cervix were significantly higher than in the ovary and lymph node. Platinum accumulation in cervical cancer tissue was lower than in the myometrium and cervix, suggesting that delivery of cisplatin to a cervical cancer is somewhat more difficult than to the normal cervix. In patients with endometrial cancer, there was significantly more accumulation in the cervix than in the ovary and lymph node.

CONCLUSIONS

These data indicated that cisplatin was easily distributed to the cervix and myometrium, but not to the ovary, lymph node, and cancer tissues.

Abrogated energy-dependent uptake of cisplatin in a cisplatin-resistant subline of the human ovarian cancer cell line IGROV-1

The parental IGROV-1 human ovarian adenocarcinoma cell line was intermittently exposed to increasing concentrations of cisplatin to obtain resistant sublines. A stable resistant subline with a resistance factor of 8.4 had been developed after 9 months and 28 passages, which was denoted IGROV(CDDP). A high correlation coefficient of 0.97 was found between the log cell survival and the DNA-adduct peak level during the process of resistance development. IGROV(CDDP) was strongly cross-resistant to carboplatin and doxorubicin and moderately cross-resistant to etoposide, docetaxel, and topotecan. Only minor resistance against 5-fluorouracil was observed, whereas IGROV(CDDP) was not cross-resistant to methotrexate. Intracellular accumulation of cisplatin was 65% lower in IGROV(CDDP) as compared with parental IGROV-1 at 37 degrees C under normal conditions. Coincubation of cisplatin with the Na+/K+-ATPase inhibitor ouabain resulted in a more pronounced decrease in platinum accumulation in IGROV-1 (44% decrease) than in IGROV(CDDP) (26% decrease). Under energy-depleting conditions the accumulation of cisplatin in the parental cell line was approximately 60% lower than that observed under normal (energy [i.e., ATP] rich) culture conditions. In contrast, the accumulation in IGROV(CDDP) was not affected by ATP-depletion. There appeared to be no significant difference between the intracellular accumulation of platinum in the resistant and sensitive cells under conditions of energy deprivation or when the uptake was studied at 0 degrees C. In conclusion, abrogation of energy-dependent accumulation in IGROV(CDDP) seems to be a major mechanism of resistance to cisplatin in this cell line.

Influence of exposure and infusion times on the cytotoxicity and pharmacokinetics of cis-malonato[(4R, 5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolane]platinum(II)

The effect of exposure time on the in vitro cytotoxicity of a new platinum complex, cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolan e]platinum(II) (SKI 2053R) and cisplatin (CDDP) toward two human lung-adenocarcinoma cell lines (PC-9, PC-14) and two human stomach-adenocarcinoma cell lines (KATO III, MKN-45) was investigated by variation of the exposure time (1, 4, 12, and 24 h) and drug concentration to yield a constant product of drug concentration times exposure time (C x T). Exposure of cancer cells to low concentrations of SKI 2053R for 12 or 24 h resulted in a greater killing effect than did 1- or 4-h exposure to 24- or 6-fold higher concentrations; the inhibitory effects of SKI 2053R on the colony formation of all tumor cell lines except for KATO III were significantly increased with increasing exposure time (P < 0.05). However, the inhibitory effects of CDDP against all tumor cell lines tested except for PC-14 were inversely correlated with increasing exposure time (P < 0.05). The intracellular accumulation of SKI 2053R and CDDP was measured under the same conditions used in the cell-survival assay using MKN-45 cells. The amount of platinum accumulated from SKI 2053R into MKN-45 cells was greater for the treatment involving low concentrations and long-term exposures (12 and 24 h) than for that using high concentrations and short-term exposures (1 and 4 h) at the constant C x T values; however, the increased accumulation of CDDP was more prominent as the concentration was increased, even if the exposure time became shorter. The pharmacokinetics studies of SKI 2053R following 1-, 4-, 12-, and 24-h infusions were performed in beagle dogs. A single dose of SKI 2053R (5.0 mg/kg) was successively given over various infusion periods to three beagle dogs at 3-week intervals. The peak levels of ultrafiltrable platinum observed for SKI 2053R at the 1-, 4-, 12-, and 24-h infusions were 3.10+/-0.49 (mean +/- SD), 1.24+/-0.06, 0.43+/-0.07, and 0.25+/-0.04 microg/ml, respectively. The mean binding ratios of platinum from SKI 2053R to plasma protein at the end of 1-, 4-, 12-, and 24-h infusions were approximately 91%, 73%, 53%, and 51%, respectively. The steady-state level of free platinum was maintained during long-term infusions (12 and 24 h) after short periods (1-3 h) from the start of the infusion. This study strongly suggests that the therapeutic efficacy of SKI 2053R given by continuous long-term infusion should be investigated in future clinical studies.

Sample handling for determination of free platinum in blood after cisplatin exposure

Cisplatin is a commonly used cytostatic drug that can be pharmacokinetically monitored by measurement of non-protein-bound platinum (Pt) in plasma. The present report elucidates some practical aspects on blood sample preparation with the purpose of identifying methodological error sources and simplifying sample handling. Human blood was incubated in vitro with clinically relevant doses of cisplatin and then stored at different temperatures for various periods prior to deproteinization. Pt concentrations were analyzed by inductively coupled plasma mass spectrometry, which is a very sensitive technique that is well suited for determination of free Pt in biological samples. Free Pt concentration is usually determined after ultrafiltration of plasma. An alternative approach used to study the protein-free fraction is to precipitate the proteins with ice-cold ethanol and then analyze the aliquot. We compared the Pt concentrations in protein-free plasma obtained by these two methods and the levels were very similar. Thus, ethanol deproteinization may be an attractive alternative to ultrafiltration, since it is both simple to perform and very cost-effective. Storage of nondeproteinized whole blood or plasma at 4 degrees C or 20 degrees C did not affect the free Pt fraction significantly for the first 2 h, after which a gradual decrease was noted. This suggests that saving the blood sample for approximately 1 h before processing should not have any major impact on the result. On long-term storage of frozen blood samples prior to deproteinization the freezing temperature proved to be of critical importance. At -20 degrees C there was a gradual decrease in the free Pt fraction during the study period of 14 days, whereas the free Pt concentration remained unchanged at -70 degrees C for at least 3 months. Thus, samples may be stored unprocessed at -70 degrees C for several months, whereas -20 degrees C is not sufficiently cold.

Differentiation-specific nuclear matrix proteins cross-linked to DNA by cis-diammine dichloroplatinum

DNA-protein cross-linkages were performed in intact undifferentiated and differentiated-HL60 cells by the action of cis-diammine dichloroplatinum. Total nuclear matrix proteins and DNA cross-linked nuclear matrix proteins were resolved by two-dimensional gel electrophoresis. The comparison of the electrophoretic patterns allowed the identification of a set of differentiation-induced nuclear matrix proteins cross-linked to DNA. One of these proteins binds cloned histone SAR sequences. Our results outline an experimental strategy for isolating and characterizing nuclear matrix components that may play a fundamental role in the overall control and coordination of gene expression during differentiation.

In vitro circumvention of cisplatin resistance by the novel sterically hindered platinum complex AMD473

A novel sterically hindered platinum complex, AMD473 [cis-aminedichloro(2-methylpyridine) platinum (II)], has been selected for phase I clinical trials due to commence in 1997. AMD473 was rationally designed to react preferentially with nucleic acids over sulphur ligands such as glutathione. This report documents the in vitro circumvention of acquired cisplatin resistance mechanisms in human ovarian carcinoma (HOC) cell lines by AMD473. In a panel of 11 HOC cell lines, AMD473 showed intermediate growth inhibition potency (mean IC50 of 8.1 microM) in comparison to cisplatin (mean IC50 of 2.6 microM) and carboplatin (mean IC50 of 20.3 microM). AMD473 showed only a 30.7-fold increase in IC50 value from the most sensitive to the most resistant HOC cell line, whereas for cisplatin it was 117.9-fold and for carboplatin 119.7-fold. AMD473 also showed significantly (P < 0.05) reduced cross-resistance to cisplatin in a panel of three cell lines with known acquired platinum drug resistance mechanisms (mean RF for AMD473 was 1.9, for cisplatin 9.1). Cellular accumulation of AMD473 was not reduced in two HOC cell lines (A2780cisR and 41McisR), in which reduced cisplatin accumulation is a major mechanism of acquired cisplatin resistance. AMD473 naked-DNA binding was significantly less affected (P < 0.05) than that of cisplatin by the presence of 5 mM glutathione. Also, AMD473 almost completely circumvented acquired cisplatin resistance in a cell line (A2780cisR) with fivefold elevated intracellular glutathione levels compared with the parent A2780 cell line when measured by clonogenic assay (RF 4.5 for AMD473 vs RF 18 for cisplatin). AMD473 also showed a lower increase in IC50 than cisplatin in an A2780 cell line model with artificially elevated glutathione levels. AMD473 DNA binding was slower than that of cisplatin on both naked and cellular DNA. AMD473 also formed DNA interstrand cross-links (ICLs) at a slower rate than cisplatin (peak ICL formation was at 5 h for cisplatin vs > or = 14 h for AMD473) after equitoxic doses were exposed to HOC cells for 2 h. AMD473 ICLs in the CH1 HOC cell line were slowly formed and showed no visible signs of being repaired 24 h after removal of drug. This was paralleled by a slower, longer lasting induction of p53 protein by equitoxic doses of AMD473 in HOC cell lines with wild-type p53. This new class of sterically hindered platinum compound, selected for clinical trial in 1997, may therefore elicit improved clinical response in intrinsically and acquired cisplatin-resistant tumours in the clinic.

Intraperitoneal cisplatin with regional hyperthermia in advanced ovarian cancer: pharmacokinetics and cisplatin-DNA adduct formation in patients and ovarian cancer cell lines

The purpose of this study was to investigate the influence of hyperthermia on cisplatin pharmacokinetics and DNA adduct formation. The latter was investigated both in tumour cell lines in vitro and in tumour cells and buccal cells from cancer patients. The patients had advanced ovarian carcinoma and were entered into a phase I study for cytoreductive surgery followed by hyperthermia in combination with intraperitoneal cisplatin administration. The cisplatin-DNA modifications in vivo and in vitro were studied by an immunocytochemical method with the polyclonal antiserum NKI-A59. The patient samples for pharmacokinetic determinations were analysed by flameless atomic absorption spectrometry. In vitro, the combination of hyperthermia and cisplatin enhanced cell killing compared with either treatment alone, such that the cisplatin-resistant ovarian cell line A2780/DDP became almost as sensitive as the parent A2780 cell line (resistance factor reduced from 30 to 2 at the IC50). In addition, increased cisplatin-DNA adducts were observed in the resistant cell line after the combined treatment compared with cisplatin alone. A good correlation was found between nuclear staining density and surviving fraction for all groups, indicating that the DNA adducts generated are an important determinant of toxicity and that the mechanism by which hyperthermia enhances kill is by increasing adduct levels. In the patients, the ratio of drug concentration in the peritoneal perfusate compared with that in plasma was found to be approximately 15, indicating a favourable pharmacokinetic ratio. Cisplatin-DNA adduct formation in tumour cells from patients was higher than in buccal cells, reflecting this higher drug exposure, i.e. local plus systemic versus systemic only. In addition, the tumour cells but not buccal cells were exposed to hyperthermia. The higher number of tumour adducts also suggests that a favourable therapeutic ratio could be achieved. Platinum-DNA adduct formation was found to decrease with distance from the surface of the tumour nodules. However, at a distance of 3-5 mm, the nuclear staining density levels were still measurable and higher than in buccal cells. In conclusion, the combined pharmacokinetic and adduct data in patients support the advantages of the intraperitoneal route for drug administration, and the addition of heat.

cis-Diamminedichloroplatinum(II) given in low-dose continuous infusion with concurrent radiotherapy to patients affected by inoperable lung carcinoma: a pharmacokinetic approach

The pharmacokinetics of cis-diamminedichloro platinum(II) (cisplatin), given as a continuous infusion with concurrent radiotherapy to patients with locally advanced inoperable non-small-cell lung carcinoma, was investigated in 16 cases. The regimen, repeated for 6 consecutive weeks, consisted of weekly 10-Gy radiotherapy given in five fractions from Monday to Friday, and concurrent 100-h infusion of cisplatin delivered at a daily dose of 4 mg/m2 by a central venous catheter and a portable pump. Throughout the weeks of therapy the platinum levels were determined in plasma and in ultrafiltered plasma by respectively inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. Mean levels of platinum in plasma ([Pt]tot ) increased from the 1st to the 6th week of infusion, while mean levels of platinum in ultrafiltered plasma ([Pt]uf), 110 microg/l, showed no marked variation throughout the therapy. [Pt]uf ranged from 16% to 22% of the total Pt. Mean levels of Pt in ultrafiltered plasma were of the same order of magnitude as those found to be active in vitro as radiopotentiators. Pt decay levels were measured for 24 h at the end of the 1st and 5th weeks of infusion, allowing the calculation of the Pt half-life and the area under the decay curves. The mean value of the area under the decay curve, plotting [Pt]tot against time (AUC), in the range 0-24 h from the end of the 5th week of infusion, was about twice that from the end of the 1st week; by contrast, the mean AUC values did not vary for the [Pt]uf against time curves. The mean values of the alpha half-life of Pt in the ultrafiltered plasma were in accordance with those published in the literature; however, an unexpected very long beta half-life was found (more than 100 h). Thus it was suggested that Pt species other than free cisplatin were present in the ultrafiltered plasma; such species probably involve metal bound to low-molecular-mass proteins. Throughout the therapy, the toxic effects in all patients were negligible, and 75% of them had an objective locoregional reduction of disease. In only 2 cases was progression of disease observed within the irradiated area. On the basis of these data, it can be concluded that cisplatin at a level of 110 microg/l in the ultrafiltered plasma, in the reported scheme of continuous intravenous infusion, has an enhancing effect on radiation and avoids concentration peaks of platinum not bound to protein.

Protective effects of betamipron on renal toxicity during repeated cisplatin administration in rats and protective mechanism

The protective effects of betamipron (BP, N-benzoyl-beta-alanine) against nephrotoxicity induced by repeated cisplatin injections were examined. The ratio of the kidney weight to body weight and the lipid peroxide level after treatment with cisplatin plus BP tended to be larger and lower than those after treatment with cisplatin plus alkaline solution, respectively. The blood urea nitrogen, serum creatinine and glutathione levels in the animals treated with cisplatin plus BP differed significantly from those in the animals treated with cisplatin plus alkaline solution. Furthermore, the mechanism of the preventive effects of BP was analyzed for cisplatin-induced nephrotoxicity. The concentration of cisplatin in the renal cortex significantly decreased with concomitant BP. BP inhibited the uptake of cisplatin into the renal cortex in a competitive manner in the same way as an anionic transport inhibitor, probenecid. The treatment with BP appears to be useful for the renal toxicity induced by repeated cisplatin administration.

Pharmacokinetics and tissue distribution of cisplatin and conjugates of cisplatin with carboxymethyldextran and A5B7 monoclonal antibody in CD1 mice

The plasma disposition kinetics and tissue distribution of platinum was evaluated following intravenous bolus administration to CD1 immune-competent mice of cisplatin, cisplatin conjugated to anti-CEA monoclonal antibody A5B7 via a carboxymethyl dextran (CMdextran) carrier molecule, and cisplatin coupled to the CMdextran in the absence of antibody. In addition, the in vivo characteristics of 125I-labeled A5B7 were compared with and without conjugation to CMdextran. Conjugation of cisplatin [clearance (CL = 0.62 mL/min/g, volume of distribution at steady-state (Vdss) = 16 mL/g] to CMdextran restricted its tissue distribution (Vdss = 0.43 mL/g) and reduced its systemic clearance (CL = 0.055 mL/min/g). Subsequent conjugation of the complex to A5B7 further reduced both its distribution (Vdss = 0.20 mL/g) and clearance (CL = 0.016 mL/min/g). Clearance of A5B7 (CL = 0.002 mL/min/g) was increased by conjugation to CMdextran (CL = 0.014 mL/min/g); tissue distribution was unchanged. A5B7-CMdextran-cisplatin was relatively stable in plasma and other tissues, except the liver. The extent of distribution of platinum into tissues (lung, liver, muscle, kidney) was markedly influenced by conjugation, with the influence being greatest for unmodified cisplatin and least for the A5B7-CMdextran conjugate. However, the time courses of tissue distribution, expressed in mean residence time scales, were similar, implying a common mechanism controlling tissue uptake.

Protective effects of vitamin E and C on cisplatin nephrotoxicity in developing rats

The kinetics of vitamin E was followed in serum, liver and kidney of 10- and 55-day-old rats after the administration of a single i.m. dose of 100 mg alpha-tocopherol acetate/100 g body wt. The basal levels without vitamin E administration were significantly higher in serum and liver of 10- than 55-day-old rats. The effect of vitamin E on cisplatin (CP; 0.6 mg/100 g body wt., i.p.) nephrotoxicity was investigated by determining urinary volume and protein excretion, as well as the concentration of blood urea nitrogen (BUN) and lipid peroxides in renal tissue (LPO). Previously described age differences in CP nephrotoxicity were confirmed. The administration of vitamin E, 12 h prior to CP, diminished the toxic effect of CP in young and adult rats. This effect could not be enhanced by a second administration of vitamin E. The simultaneous administration of vitamin E and C 12 h prior to CP intensified the protective effect of a single administration of vitamin E in 10- and 55-day-old rats without influencing the concentration of platinum in renal tissue.