|
|
||||||||
Ann Thorac Surg 2001;72:1173-1178
© 2001 The Society of Thoracic Surgeons
a First Department of Surgery, Yamaguchi University School of Medicine, Yamaguchi, Japan
Accepted for publication June 18, 2001.
Address reprint requests to Dr Tanaka, First Department of Surgery, Yamaguchi University School of Medicine, 1-1-1 Minami-kogushi, Ube, Yamaguchi 755-8505, Japan
e-mail: toshik{at}po.cc.yamaguchi-u.ac.jp
| Abstract |
|---|
|
|
|---|
Methods. Systemic and local toxicities of isolated lung perfusion treatment were evaluated on the basis of body weight change, survival rate, and histologic findings. The maximal tolerated dose of digitonin was determined by assessing survival on day 21 after contralateral pneumonectomy, body weight change, and histologic findings. Pharmacokinetics were observed in a solitary lung tumor nodule model by measuring platinum concentration in tumor and normal lung tissue. The antitumor effect was evaluated by the number of tumor nodules in the left lung 21 days after isolated lung perfusion. Isolated lung perfusion was performed 7 days after 1.0 x 106 methylcholanthrene sarcoma cells were injected into the external jugular vein.
Results. The maximal tolerated dose of digitonin was 20 µmol/L. Platinum concentration of tumor nodules in the digitonin-cisplatintreated rats was 20% higher than in the cisplatin-only group (5.48 ± 0.64 µg/g tissue versus 4.50 ± 1.09 µg/g tissue; p = 0.067). The number of pulmonary nodules decreased significantly by digitonin use (1.3 ± 1.5 versus 9.7 ± 2; p < 0.0001).
Conclusions. Isolated lung perfusion with digitonin and cisplatin in combination was performed safely and enhanced the antitumor effect. These drugs in combination show promise for enhancing the effect of clinical isolated lung perfusion.
| Introduction |
|---|
|
|
|---|
Digitonin, a detergent, increases cell permeability by binding specifically to cholesterol in the plasma membrane, and it has been shown to enhance the intracellular uptake of platinum in a human ovarian carcinoma cell line in vitro [7]. In addition, digitonin increased platinum concentrations in rat hepatoma tissue in a carboplatin intraarterial administration study [8]. We selected digitonin in our experiment because we expected that the increase of cell permeability enhanced intracellular platinum concentration and antitumor effect. We investigated the toxicity, pharmacokinetics, and synergistic antitumor effect of digitonin-cisplatin combination ILP.
| Material and methods |
|---|
|
|
|---|
Male Fischer 344 rats weighing 250 to 300 g were used for experiments and were treated in accordance with the Animal Welfare Act and the "Guide for the Care and Use of Laboratory Animals" (National Institutes of Health publication 85-23, revised 1985). The Institutional Animal Care and Use Committee of Yamaguchi University approved the experiments. Rats were bred in a standard laboratory and allowed free access to food and water in a temperature-controlled environment under a 12-hour light and dark cycle.
Chemicals
Digitonin (Sigma Chemical Company, St. Louis, MO, USA) was dissolved in dimethylsulfoxide and diluted with phosphate-buffered saline solution (PBS) immediately before use [9]. Cisplatin (Sigma) was dissolved in 6% buffered hetastarch solution immediately before use [9].
Evaluation of intracellular concentration and antitumor effect in vitro
For the pharmacokinetic study, 1.0 x 107 MCA sarcoma cells were seeded into RPMI-1640 medium containing 50 µg/mL cisplatin (Cis group), 50 µg/mL cisplatin and 20 µmol/L digitonin (Cis-D20 group), or 50 µg/mL cisplatin and 50 µmol/L digitonin (Cis-D50 group). After a 30-minute treatment, cells were washed twice with PBS and extracted by centrifuge. Cell platinum levels were measured by flameless atomic spectrometry.
For the antitumor effect study, MCA sarcoma cells (1.0 x 103) were seeded for 12 hours in 96-well cell culture dishes (Nunclon Surface, Nalge Nunc International, Roskilde, Denmark). After seeding, the cells were exposed to PBS with 50 mmol/L dimethylsulfoxide (PBS group), 5 µmol/L digitonin alone (D group), 5 µg/mL cisplatin alone (C group), or 5 µg/mL cisplatin and 5 µmol/L digitonin (D + C group) for 10 minutes. The cells were then washed twice with PBS. After 72 hours in culture, bromodeoxyuridine uptake was measured to determine viable cell counts with a cell proliferation enzyme-linked immunosorbent assay system (Biotrak, Amersham Life Science Ltd, Little Chalfont, UK) [10].
Isolated left lung perfusion
Isolated left lung perfusion was performed by a method described previously [6]. Briefly, animals were anesthetized with 50 mg/kg of pentobarbital administered intraperitoneally, and tracheal intubation was performed with a 16F intravenous catheter [11]. The animals were ventilated with a volume ventilator (Harvard rodent ventilator, model 683, Harvard Apparatus Inc, South Natick, MA) with room air at a tidal volume of 10 mL/kg and a rate of 80 strokes/min. A left thoracotomy was performed through the fourth intercostal space, and the left pulmonary artery and vein were exposed under a surgical microscope. After the left main pulmonary artery and vein were clamped, a polyethylene (PE-10) catheter was inserted into the pulmonary artery for infusion, pulmonary venotomy was performed, and a suction catheter placed in the proximity of the venotomy collected the effluent. All rats were perfused for 10 minutes and followed by a 5-minute washout with buffered hetastarch solution at a rate of 0.5 mL/min. A 0.2-mL bolus of digitonin was injected into the pulmonary artery just before ILP treatment in digitonin-treatment groups.
Toxicity
A total of 12 rats were randomized into the following two treatments on day 0 for study of the toxicity of digitonin: ILP with 400 µmol/L digitonin (D400 group; n = 6) and 200 µmol/L digitonin (D200 group; n = 6), both with buffered hetastarch solution only, was performed. Eighteen rats were randomly selected for injection of digitonin at 50 µmol/L (Cis-D50 group; n = 6), 20 µmol/L (Cis-D20 group; n = 6), or 10 µmol/L (Cis-D10 group; n = 6), each with 100 µg/mL cisplatin, just before ILP on day 0 to study the synergistic toxicity of digitonin and cisplatin. Toxicity was evaluated in the same manner in both toxicity studies; all rats were monitored and their body weights recorded every second day. On day 21, a right pneumonectomy to evaluate the effect of perfusion on left lung function was performed on all surviving rats. On day 35, all rats that survived were killed. Histologic changes were evaluated in each group.
Pharmacokinetics
Solitary tumor nodules were established in 12 rats by a method described previously [5]. Animals were anesthetized and intubated, and ventilation was maintained as described above. A small left thoracotomy was performed, and the thoracic cavity was opened. A 27-gauge needle attached to a 100-µL microsyringe was inserted into the left lower lung at an angle of approximately 15 degrees to a depth of 3 mm, and 1.0 x 106 tumor cells in 20 µL of PBS were inoculated into the lung parenchyma. After the lung was expanded, the chest and thoracotomy incision were closed.
All 12 animals were randomized into two groups (n = 6 in each group) on day 14 after tumor cell inoculation. Rats in the Cis group underwent ILP with 100 µg/mL cisplatin. Rats in the Cis-D20 group underwent ILP with 100 µg/mL cisplatin after 20 µmol/L digitonin was injected. After perfusion, a left pneumonectomy was performed. The tumor nodule was removed from samples of the left lung. Total platinum concentrations of the tumor and the left lung were measured by flameless atomic spectrometry.
Antitumor effect
A total of 18 rats were randomized into two groups 7 days after 1 x 106 MCA sarcoma cells had been injected through the external jugular vein. A Cis group of 9 rats underwent ILP with 100 µg/mL cisplatin, and a Cis-D20 group of 9 rats were given ILP with 100 µg/mL cisplatin after 20 µmol/L digitonin was injected. All 18 rats were killed 14 days after ILP treatment, and their lungs were stained with India ink for identification of metastases according to the method of Wexler [12]. All tumor nodules were counted on the left lung.
Statistical analysis
All data are presented as mean ± standard deviation. In vitro data were analyzed by Fishers exact test, and in vivo data, by unpaired Students t test. Significance was determined at p less than 0.05.
| Results |
|---|
|
|
|---|
|
|
According to histologic analysis, the left lung recovered to almost normal architecture within 35 days in the D200 group, but slight interstitial thickness was revealed in the D400 group (Fig 3A, 3B). Severe left lung damage developed in the Cis-D50 group (Fig 3D). Body weight changes between the D400 and the D200 groups, and among Cis-D50, Cis-D20, and Cis-D10 groups, were not statistically different.
|
|
| Comment |
|---|
|
|
|---|
Cisplatin is widely used in the treatment of various malignant neoplasms including sarcomas. Cisplatin causes cytotoxicity by DNA injury by means of DNA platination. The intracellular concentration of platinum plays a very important role in cytotoxicity, but platinum-containing drugs enter cells relatively slowly in comparison with many other cytotoxic agents [17]. Although the mechanism by which cisplatin enters cells is not understood completely, many investigators report that uptake of cisplatin occurs primarily by passive diffusion. This slow uptake may relate to the clinical failures and our previous experimental findings [5].
Digitonin increases permeability of the plasma membrane by binding to cholesterol in the bilayer membrane in proportion to its cholesterol content [18]. This permeabilization enhances intracellular uptake of cisplatin [19]. Our in vitro experiment showed that the combined use of digitonin and cisplatin increases the cellular uptake of platinum in MCA sarcoma cells significantly. Furthermore, a significant synergistic antitumor effect was observed with the combined use of digitonin and cisplatin at very low doses, each of which, separately, had not shown an antitumor effect. Cisplatin with dimethylsulfoxide did not enhance the intracellular platinum concentration compared with cisplatin only, and dimethylsulfoxide only did not show an antitumor effect (data not shown). Our in vitro results indicate the possibility of a synergistic effect in ILP treatment.
Isolated lung perfusion with digitonin only did not result in toxicity in normal lung tissue. The toxicity resulting from digitonin and cisplatin in combination was quite severe. We obtained a 67% survival rate after right pneumonectomy when the dose of digitonin was decreased to 20 µmol/L. Thus, this was the dose that was studied.
Regarding the significant increase in intracellular platinum concentration in vitro, we expected that a very high platinum concentration would be seen in tumor tissue in the Cis-D20 group. The total platinum concentration of tumor tissue in the Cis-D20 group increased only slightly, however, in comparison with that in the control group. Although the reason for this was not clear, a possible factor is the different blood supply from the pulmonary and bronchial circulations to the tumor tissue. According to investigations conducted by Milne and associates [20] in humans and rats, the source of blood in pulmonary metastatic deposits may be the pulmonary circulation, bronchial circulation, or a combination of both. In fact, tumor nodules were stained after trypan blue infusion from both pulmonary artery and the aorta in our previous study [5]. This suggests that blood supply was derived from both pulmonary and bronchial systems in the rat solitary tumor model.
An antitumor effect was significantly evident in ILP with digitonin and cisplatin combined, which agreed well with results of the in vitro study. This may be related, in part, to the slight increase in total platinum in tumor tissue, but the synergistic effect was important also. Digitonin increases cell permeability and deformity by corrugations of hemitubules in the cell bilayer membrane [18]; thus, the antitumor effect of cisplatin is by the fragility of tumor cells after digitonin exposure. In fact, the combined use of low-dose cisplatin and digitonin caused an excellent antitumor effect in our in vitro study.
In summary, we observed that the combined use of digitonin and cisplatin increased intracellular platinum concentration and enhanced the antitumor effect in vitro. Furthermore, ILP to sarcomatous pulmonary metastases in the rat with digitonin and cisplatin in combination was performed safely and enhanced the antitumor effect in comparison with ILP with only cisplatin. A trial in large animals closer to humans will be needed before phase I human trials because we are aware of no published reports that describe the information in humans regarding potential toxicity of digitonin. If the toxicity to humans is solved, our findings suggest the possibility of enhancing the antitumor effects of clinical ILP treatment.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
P. E. Van Schil, J. M. Hendriks, B. P. van Putte, B. A. Stockman, P. R. Lauwers, P. W. ten Broecke, M. J. Grootenboers, and F. M. Schramel Isolated lung perfusion and related techniques for the treatment of pulmonary metastases Eur. J. Cardiothorac. Surg., March 1, 2008; 33(3): 487 - 496. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. P. v. Putte, A. Huisman, J. M.H. Hendriks, P. E.Y. v. Schil, W. J. v. Boven, F. Schramel, F. Nijkamp, and G. Folkerts Pulmonary intravascular volume can be used for dose calculation in isolated lung perfusion Eur. J. Cardiothorac. Surg., October 1, 2005; 28(4): 594 - 598. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. P. Van Putte, J. M.H. Hendriks, S. Romijn, B. Pauwels, J. B. Vermorken, and P. E.Y. Van Schil Combination chemotherapy with gemcitabine with isolated lung perfusion for the treatment of pulmonary metastases J. Thorac. Cardiovasc. Surg., July 1, 2005; 130(1): 125 - 130. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Jinbo, K. Ueda, Y. Kaneda, M. Sudo, T.-S. Li, and K. Hamano Video-assisted transcatheter lung perfusion regional chemotherapy Eur. J. Cardiothorac. Surg., June 1, 2005; 27(6): 1079 - 1082. [Abstract] [Full Text] [PDF] |
||||
![]() |
U. F.W. Franke, T. Wittwer, M. Kaluza, M. Albert, V. Becker, M. Roskos, M. Lessel, and T. Wahlers Evaluation of isolated lung perfusion as neoadjuvant therapy of lung metastases using a novel in vivo pig model: II. High-dose cisplatin is well tolerated by the native lung tissue Eur. J. Cardiothorac. Surg., October 1, 2004; 26(4): 800 - 806. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Schroder, S. Fisher, A. C. Pieck, A. Muller, U. Jaehde, H. Kirchner, A. Haverich, and P. Macchiarini Technique and results of hyperthermic (41{degrees}C) isolated lung perfusion with high-doses of cisplatin for the treatment of surgically relapsing or unresectable lung sarcoma metastasis Eur. J. Cardiothorac. Surg., July 1, 2002; 22(1): 41 - 46. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |