Br. J. Cancer (1978) 37,
Suppl. III, 20
EFFECT OF RADIATION ON CIS-DICHLORODIAMMINEPLATINUM(II) AND DNA IN AQUEOUS SOLUTION R. C. RICHMOND* AND M. G. SIMICt From the *Department of Microbiology and Virology, Boston University Medical Center, Boston, MA 02118, U.S.A., and the tFood Engineering Laboratory, U.S. Army NARADCOM, Natick, MA 01760, U.S.A.
Summary.-The radiolysis of cis-dichlorodiammineplatinum(II) (cis-PDD) was studied in order to better understand the mechanisms by which it acts as a radiation sensitizer. The Pt(I) intermediate formed by e-aq reduction of cis-PDD loses both chlorides rapidly, interacts with 02 to form a Pt-oxygen adduct, reacts with the hydroxyl radical adduct of thymine and the peroxy radical of t-butanol, and disproportionates to platinum metal and trans-PDD. The Pt(III) intermediate formed by OH oxidation of cis-PDD likely disproportionates to cis-PDD and Pt(IV) complexes. In a biological model, radiation-induced 3H-thymine base residue release from DNA is found to be inhibited by cis-PDD. THE PLATINUM complex cis-dichlorodiammineplatinum(II) (cis-PDD) is established as a potent anticancer drug (Rosenberg, 1973). The potential advantages of
tions were irradiated without pH adjustment using 60Co-gamma rays (9 5 krad/min). Qualitative analysis of irradiated solutions was made by preconditioning samples in an antitumour agent acting as a radiation 0-15 M NaCl for 30 min at ambient temperafollowed by thin layer chromatography sensitizer in combined drug and radiation ture, (TLC) on silica gel (Kontes channelled cancer treatment led to previous investiga- Quantum-Q) with plates an acetone/water (9: 1) tions on the radiosensitizing properties of solvent. Spots were visualized by 12 vapour. cis-PDD in bacteria (Richmond and This is a modification of a previous method Powers, 1976; Richmond, Zimbrick and (Basolo et al., 1963). Quantitative analysis of Hykes, 1977) and mammalian tumours cis-PDD was made by adding scrapings of (Douple, Richmond and Logan, 1977), non-visualized TLC spots to 2 ml of a 0 1 N HCI and 0.5% KI solution previously with encouraging results. An understanding of the mechanism(s) conditioned at a tenfold higher concentration ambient temperature for 2-5 h. These by which cis-PDD sensitizes cells to radia- at samples were incubated at 70TC for 45 min, tion is important if optimal use and future centrifuged, and the supernatant gassed with development of platinum drugs are to be N2 for 45 min. The Pt-iodide complex of this realized at the clinical levels of combined reaction displays Amax = 492 nm and E = treatment of cancer. For this reason we 1-21 X 104 M-1 cm-1. A non-irradiated cisinvestigated the radiation chemistry of PDD sample was carried as a normalizing cis-PDD in aqueous solution. control when irradiated samples were assayed by TLC for cis-PDD destruction. Thymine base residue release experiments MATERIALS AND METHODS involved irradiating aqueous samples of 3HCis-PDD was provided by the Drug thymine labelled DNA purified from E. coli Development Branch, Division of Cancer C 321 thy-. After irradiation, DNA samples Treatment, National Cancer Institute were incubated at 37°C for 16 h (Ward and Kuo, 1976), then dialysed, and the dialysate (U.S.A.). Pulse radiolysis techniques are as previously concentrated and chromatographed on described (Simic, Neta and Hayon, 1969). Sephadex G-10 (Richmond and Zimbrick, In steady experiments, 1 mm cis-PDD solu- 1975).
RADIATION,
cis-Pt(NH3)2C12,
AND
DNA
21
RESULTS
Cis-PDD reacts rapidly with e-aq and OH, as determined by pulse radiolysis: k(cis-PDD + e-aq) 1=8 X 1010 M-1 s-1 k(cis-PDD + OH) 2-0 x 109 M-1 s-1 The Pt(J) intermediate obtained on reduction by e-aq is observed to participate in some novel reactions. (a) An 02-adduct forms in the presence 1-3 x 104 M-1 cm-1), with k(Pt(NH3)2CI + 02) 5 x 109 M-1 s-1
Of
02
(Amax
250 nm;
E
x -
.E C.)
(b) This adduct likely reacts with the t-butyl peroxy radical to give a stable peroxide, judging from absorbence in the 240 to 300 nm region after gammairradiation of 2 mm cis-PDD and 0-2 M t-butanol solutions in the presence of 2 x 10-4M 02. FRACTION NUMBER (c) Pt(J) reacts with the hydroxyl FIG.-3HM,-thymidine labelled DNA puriradical adduct of thymine *TOH, with fied from E. coli C 321 thy- and irradiated in aerated 10 mM NaCI04 solution with k 1.2 x 109 M-1 s-1 as deduced from 60Co-gamma rays. 3H-activity profile re*TOH decay at 400 nm. This reaction presents radiation-induced thymine base residue release products. scheme is: Pt(NH3)2+ + *TOH products (most likely Pt(NH3)2R+) and N20, no trans-PDD or Pt metal is observed following irradiation, although or reveals two unidentified spots at, and TLC Pt(NH3)2CI +-TOH products (most near, the origin for N20 gassed solutions. likely Pt(NH3)2ClR) The Figure shows the 3H-radioactivity The results of steady state radiolysis profiles from the dialysate of aerated solutions of 3H-thymine labelled DNA irare shown in Table I. The TLC of cis-PDD irradiated in N2 reveals Pt metal and radiated on ice with 15 krad in the absence trans-PDD as radiation products. In 02 and presence of cis-PDD. These results =
--*
--
TABLE.-Steady State Chemistry of cis-PDD Dose 0 rad 0 rad 100 krad
100 krad
1
Conditions cis-PDD mM trans-PDD mM cis-PDD; N2
1
mm cis-PDD; N2
1
t-butanol mm cis-PDD; N20
1
1
mM
0 -2
100 krad
mM
Rf* 0 79 0 89 0 79 0 90 0 79 0 89 0 78 0 03 0o00
pHt
G-value4
5-10
2 -24
5-92
3 25
4 64
2 47
Silica gel TLC plates; acetone/water (9:1) solvent; 80 ,Iu sample. t After treatment interval. t cis-PDD destruction; assayed from TLC spot.
*
Pt metal formation
4 62 small amount black precipitate moderate amount black precipitate no precipitate
22
R. C. RICHMOND AND M. G. SIMIC
represent two different experiments. In one, cis-PDD is added to an ice cold DNA solution and irradiated immediately. Under these conditions there is negligible binding of cis-PDD to DNA, and results indicate free solution effects. In the second, cisPDD and DNA (1 Pt to 4 bases) are first incubated at 37°C for 24 h before irradiation. Under these conditions cis-PDD complexes extensively with DNA (Horacek and Drobnik, 1971), and results indicate the effect of bound cis-PDD. Thymine residue release products are obviously reduced in the presence of cisPDD. TLC of samples from the gel filtration profile of DNA irradiated alone was run in one dimension on PEI cellulose sheets using a n-butanol/methanol/water/ ammonia (60:20:20: 1) solvent (Raaen and Kraus, 1968). The TLC results verify the major peak at fraction 20 as thymine; fraction 16 as a mix of thymidine and an unknown; fraction 14 as an unknown; and fraction 11 as containing some thymidylic acid. DISCUSSION
Pulse conductivity measurements (Simic and Lilie, 1974) of aqueous solutions reveals that the Pt(J) transient from e-aq reduction of cis-PDD loses two chlorides (M. G. Simic and J. Lilie, unpublished results): (a) Pt(NH3)2C12-+ Pt(NH3)2CI + Cl(tl estimated < 1 ,us) (b) Pt(NH3)2CI -+ Pt(NH3)2+ + CL(tl- 140 /is) The Pt(NH3)2+ intermediate appears to be relatively stable (up to 1 s). Hence, the Pt(NH3)2+ and Pt(NH3)2CI intermediates have to be both considered in reactions of Pt(J), depending on the time scale of the second order reaction studied. Thus, in the presence of 02, Pt(NH3)2 C102 is most likely formed, with some contribution of Pt(NH3)202+ at lower 02 concentrations. These intermediates most likely can react with peroxy radicals, as
is the case for Rh(NH3)4022+ (Endicott, personal communication), to give peroxy complexes, e.g.: Pt(NH3)2CIO2 + *OOR --Pt(NH3)2Cl02R + 02 where *OOR is the t-butyl peroxy radical in this work. The reaction of the Pt(NH3)2CI intermediate with *TOH is 3 times faster than k(2 * TOH) = 40 x 108 M-1 5-1 (Hayon and Simic, 1973). We suggest addition of the Pt(J) intermediate to the free radical site of *TOH as most likely. Complexes of Pt(II) with carbon ligands are well known (Basolo and Pearson, 1967). However, reduction of *TOH by Pt(I) cannot be excluded here. These reactions of Pt(I) may be accurate models for cis-PDD sensitization. Reactions of Pt(J) similar to that with *TOH are probable with DNA free radicals. Reactions of the Pt(NH3)2CIO2 intermediate with cellular peroxy radicals may also be relevant to the small amount of cis-PDD sensitization reported for bacterial spores (Richmond and Powers, 1976) and cells (Richmond, Zimbrick and Hykes, 1977) in 02. Increases in pH observed after irradiation certainly reflect release of ammonia ligands as a consequence of disproportionation: 2 Pt(I) -> Pt° + Pt(II) The G-values of cis-PDD destruction in N2 (Table) indicate that in the absence of OH, the yield of cis-PDD destroyed is equivalent to G(e-aq + H) - 3.3. This fact, and the distinct appearance of both Pt metal and trans-PDD, strongly suggest that the Pt(I) intermediate (having lost both chlorides) loses cis-direction and disproportionates. Trans-PDD binds differently and to a greater extent than cisPDD to biological material, such as DNA (Pascoe and Roberts, 1974). An altered PDD binding pattern to DNA may be relevant to radiation-induced damage, since bound cis-PDD is shown to reduce the yields of thymine base residues re-
RADIATION,
cis-Pt(NH3)2CI2,
AND
DNA
23
REFERENCES leased from the irradiated cis-PDD/DNA complex. BASOLO, F., LEDERER, M., OssIcINI, L. & STEPHEN, K. H. (1963) A Paper Chromatographic Study of In N20, the G-value for cis-PDD Some Platinum(II) Compounds II. The Separation destruction is essentially half that of the of cis- and trans-Dihalogenodiammineplatinum(II) OH radical yield in this system, G(OH)Complexes. J. Chromatog., 10, 262. PEARSON, R. G. (1967) Mechanisms of 5-6, suggesting that disproportionation of BASOLO, F. &Reactions: A Study of Metal Complexes Inorganic the Pt(III) intermediate yields cis-PDD: in Solution. New York: John Wiley and Sons. DOUPLE, E. B., RICHMOND, R. C. & LOGAN, M. E. 2 Pt(111) -> Pt(II) + Pt(JV) (1977) Therapeutic Potentiation in a Mouse Mammary Tumor and an Intracerebral Rat The Pt(III), in contrast to Pt(I), Brain Tumor by Combined Treatment with cisDichlorodiammineplatinurn(II) and Radiation. J. therefore appears not to lose cis-direction, Clin. Hematol. Oncol., 7, 585. suggesting Cl- ligand retention in this HAYON, E. & SIMIC, M. G. (1973) Addition of Hydroxyl Radicals to Pyrimidine Bases and Electron intermediate. The low Rf-values of the Transfer Reactions of Intermediates to Quinones. two presumed Pt(IV) products (Table) J. Am. Chem. Soc., 95, 1029. suggests they are cationic complexes HORACEK, P. & DROBNIK, J. (1971) Interaction of cis-Dichlorodiammineplatinum(II) with DNA. (J. D. Hoeschele, unpublished results). Biochem. biophys. Acta, 254, 341. Subsequent reactions of Pt(III) and PASCOE, J. M. & ROBERTS, J. J. (1974) Interactions Pt(JV) species with cellular constituents Between Mammalian Cell DNA and Inorganic Platinum Compounds. I. DNA Interstrand Crossor bioradicals may contribute to the small Linking and Cytotoxic Properties of Platinum(II) compartment of cis-PDD sensitization Compounds. Biochem. Pharmac., 23, 1345. RAAEN, H. P. & KRAUS, F. E. (1968) Resolution of reported for bacterial systems irradiated Complex Mixtures of Nucleic Acid Bases, Nucleoin 02 or N20 (Richmond and Powers, sides, and Nucleotides by Two-Dimensional Thin1976; Richmond, Zimbrick and Hykes, Layer Chromatography on PolyethyleneimineCellulose. J. Chromatog., 35, 531. 1977). R. C. & ZIMBRICK, J. D. (1975) In vivo The radiation chemistry of cis-PDD as RICHMOND, Radiation-Induced Thymine Residue Release from it relates to the radiation sensitization of E. coli DNA. Biochem. biophys. Res. Comm., 64, 391. cells is complex. The results presented RICHMOND, R. C. & POWERS, E. L. (1976) Radiation here allow for conventional mechanisms, Sensitization of Bacterial Spores by cis-Dichloroand in addition suggest other possibilities. diammineplatinum(II). Radiat. Res., 68, 251. RICHMOND, R. C., ZIMBRICK, J. D. & HYKES, D. L. These latter include the potential for: (1977) Radiation-Induced DNA Damage and Lethality in E. Coli as Modified by the Antitumor (a) reactions of Pt intermediates (Pt(J), Agent cis-Dichlorodiammineplatinum(II). Radiat. Pt(mIJ), Pt(NH3)2C102) with bioradicals; Res., 71, 447. B. (1973) Platinum Coordination Com(b) secondary reactions of stable pro- ROSENBERG, plexes in Cancer Chemotherapy. Naturwissenducts (trans-PDD, Pt(IV) complexes) with schaften, 60, 399. cellular constituents and bioradicals; SIMIc, M. G., NETA, P. & HAYON, E. (1969) Pulse Radiolysis Study of Alcohols in Aqueous Solu(c) effects of Pt complexes or intertions. J. Phys. Chem., 73, 3794. mediates coordinated to biological ligands SIMIC, M. G. & LILIE, J. (1974) The Kinetics of Ammonia Detachment from Reduced Co(III) (e.g., DNA) at or near damaged sites. RCR acknowledges support from an NRC Research Associateship tenable at the U.S. Army NARADCO0M Laboratories, Natick, MA 01760, U.S.A.; this work partially supported by ACS grant LOI-PDT-90 and PHS grant A04-18522-02.
Complexes Based on Conductometric Pulse Radiolysis. J. Am. Chem. Soc., 96, 291. WARD, J. D. & Kuo, I. (1976) Strand Breaks, Base Release, and Post Irradiation Changes in DNA Gamma-Irradiated in Dilute 02-Saturated Aqueous Solution. Radiat. Res., 66, 485.
Suppl. III, 20
EFFECT OF RADIATION ON CIS-DICHLORODIAMMINEPLATINUM(II) AND DNA IN AQUEOUS SOLUTION R. C. RICHMOND* AND M. G. SIMICt From the *Department of Microbiology and Virology, Boston University Medical Center, Boston, MA 02118, U.S.A., and the tFood Engineering Laboratory, U.S. Army NARADCOM, Natick, MA 01760, U.S.A.
Summary.-The radiolysis of cis-dichlorodiammineplatinum(II) (cis-PDD) was studied in order to better understand the mechanisms by which it acts as a radiation sensitizer. The Pt(I) intermediate formed by e-aq reduction of cis-PDD loses both chlorides rapidly, interacts with 02 to form a Pt-oxygen adduct, reacts with the hydroxyl radical adduct of thymine and the peroxy radical of t-butanol, and disproportionates to platinum metal and trans-PDD. The Pt(III) intermediate formed by OH oxidation of cis-PDD likely disproportionates to cis-PDD and Pt(IV) complexes. In a biological model, radiation-induced 3H-thymine base residue release from DNA is found to be inhibited by cis-PDD. THE PLATINUM complex cis-dichlorodiammineplatinum(II) (cis-PDD) is established as a potent anticancer drug (Rosenberg, 1973). The potential advantages of
tions were irradiated without pH adjustment using 60Co-gamma rays (9 5 krad/min). Qualitative analysis of irradiated solutions was made by preconditioning samples in an antitumour agent acting as a radiation 0-15 M NaCl for 30 min at ambient temperafollowed by thin layer chromatography sensitizer in combined drug and radiation ture, (TLC) on silica gel (Kontes channelled cancer treatment led to previous investiga- Quantum-Q) with plates an acetone/water (9: 1) tions on the radiosensitizing properties of solvent. Spots were visualized by 12 vapour. cis-PDD in bacteria (Richmond and This is a modification of a previous method Powers, 1976; Richmond, Zimbrick and (Basolo et al., 1963). Quantitative analysis of Hykes, 1977) and mammalian tumours cis-PDD was made by adding scrapings of (Douple, Richmond and Logan, 1977), non-visualized TLC spots to 2 ml of a 0 1 N HCI and 0.5% KI solution previously with encouraging results. An understanding of the mechanism(s) conditioned at a tenfold higher concentration ambient temperature for 2-5 h. These by which cis-PDD sensitizes cells to radia- at samples were incubated at 70TC for 45 min, tion is important if optimal use and future centrifuged, and the supernatant gassed with development of platinum drugs are to be N2 for 45 min. The Pt-iodide complex of this realized at the clinical levels of combined reaction displays Amax = 492 nm and E = treatment of cancer. For this reason we 1-21 X 104 M-1 cm-1. A non-irradiated cisinvestigated the radiation chemistry of PDD sample was carried as a normalizing cis-PDD in aqueous solution. control when irradiated samples were assayed by TLC for cis-PDD destruction. Thymine base residue release experiments MATERIALS AND METHODS involved irradiating aqueous samples of 3HCis-PDD was provided by the Drug thymine labelled DNA purified from E. coli Development Branch, Division of Cancer C 321 thy-. After irradiation, DNA samples Treatment, National Cancer Institute were incubated at 37°C for 16 h (Ward and Kuo, 1976), then dialysed, and the dialysate (U.S.A.). Pulse radiolysis techniques are as previously concentrated and chromatographed on described (Simic, Neta and Hayon, 1969). Sephadex G-10 (Richmond and Zimbrick, In steady experiments, 1 mm cis-PDD solu- 1975).
RADIATION,
cis-Pt(NH3)2C12,
AND
DNA
21
RESULTS
Cis-PDD reacts rapidly with e-aq and OH, as determined by pulse radiolysis: k(cis-PDD + e-aq) 1=8 X 1010 M-1 s-1 k(cis-PDD + OH) 2-0 x 109 M-1 s-1 The Pt(J) intermediate obtained on reduction by e-aq is observed to participate in some novel reactions. (a) An 02-adduct forms in the presence 1-3 x 104 M-1 cm-1), with k(Pt(NH3)2CI + 02) 5 x 109 M-1 s-1
Of
02
(Amax
250 nm;
E
x -
.E C.)
(b) This adduct likely reacts with the t-butyl peroxy radical to give a stable peroxide, judging from absorbence in the 240 to 300 nm region after gammairradiation of 2 mm cis-PDD and 0-2 M t-butanol solutions in the presence of 2 x 10-4M 02. FRACTION NUMBER (c) Pt(J) reacts with the hydroxyl FIG.-3HM,-thymidine labelled DNA puriradical adduct of thymine *TOH, with fied from E. coli C 321 thy- and irradiated in aerated 10 mM NaCI04 solution with k 1.2 x 109 M-1 s-1 as deduced from 60Co-gamma rays. 3H-activity profile re*TOH decay at 400 nm. This reaction presents radiation-induced thymine base residue release products. scheme is: Pt(NH3)2+ + *TOH products (most likely Pt(NH3)2R+) and N20, no trans-PDD or Pt metal is observed following irradiation, although or reveals two unidentified spots at, and TLC Pt(NH3)2CI +-TOH products (most near, the origin for N20 gassed solutions. likely Pt(NH3)2ClR) The Figure shows the 3H-radioactivity The results of steady state radiolysis profiles from the dialysate of aerated solutions of 3H-thymine labelled DNA irare shown in Table I. The TLC of cis-PDD irradiated in N2 reveals Pt metal and radiated on ice with 15 krad in the absence trans-PDD as radiation products. In 02 and presence of cis-PDD. These results =
--*
--
TABLE.-Steady State Chemistry of cis-PDD Dose 0 rad 0 rad 100 krad
100 krad
1
Conditions cis-PDD mM trans-PDD mM cis-PDD; N2
1
mm cis-PDD; N2
1
t-butanol mm cis-PDD; N20
1
1
mM
0 -2
100 krad
mM
Rf* 0 79 0 89 0 79 0 90 0 79 0 89 0 78 0 03 0o00
pHt
G-value4
5-10
2 -24
5-92
3 25
4 64
2 47
Silica gel TLC plates; acetone/water (9:1) solvent; 80 ,Iu sample. t After treatment interval. t cis-PDD destruction; assayed from TLC spot.
*
Pt metal formation
4 62 small amount black precipitate moderate amount black precipitate no precipitate
22
R. C. RICHMOND AND M. G. SIMIC
represent two different experiments. In one, cis-PDD is added to an ice cold DNA solution and irradiated immediately. Under these conditions there is negligible binding of cis-PDD to DNA, and results indicate free solution effects. In the second, cisPDD and DNA (1 Pt to 4 bases) are first incubated at 37°C for 24 h before irradiation. Under these conditions cis-PDD complexes extensively with DNA (Horacek and Drobnik, 1971), and results indicate the effect of bound cis-PDD. Thymine residue release products are obviously reduced in the presence of cisPDD. TLC of samples from the gel filtration profile of DNA irradiated alone was run in one dimension on PEI cellulose sheets using a n-butanol/methanol/water/ ammonia (60:20:20: 1) solvent (Raaen and Kraus, 1968). The TLC results verify the major peak at fraction 20 as thymine; fraction 16 as a mix of thymidine and an unknown; fraction 14 as an unknown; and fraction 11 as containing some thymidylic acid. DISCUSSION
Pulse conductivity measurements (Simic and Lilie, 1974) of aqueous solutions reveals that the Pt(J) transient from e-aq reduction of cis-PDD loses two chlorides (M. G. Simic and J. Lilie, unpublished results): (a) Pt(NH3)2C12-+ Pt(NH3)2CI + Cl(tl estimated < 1 ,us) (b) Pt(NH3)2CI -+ Pt(NH3)2+ + CL(tl- 140 /is) The Pt(NH3)2+ intermediate appears to be relatively stable (up to 1 s). Hence, the Pt(NH3)2+ and Pt(NH3)2CI intermediates have to be both considered in reactions of Pt(J), depending on the time scale of the second order reaction studied. Thus, in the presence of 02, Pt(NH3)2 C102 is most likely formed, with some contribution of Pt(NH3)202+ at lower 02 concentrations. These intermediates most likely can react with peroxy radicals, as
is the case for Rh(NH3)4022+ (Endicott, personal communication), to give peroxy complexes, e.g.: Pt(NH3)2CIO2 + *OOR --Pt(NH3)2Cl02R + 02 where *OOR is the t-butyl peroxy radical in this work. The reaction of the Pt(NH3)2CI intermediate with *TOH is 3 times faster than k(2 * TOH) = 40 x 108 M-1 5-1 (Hayon and Simic, 1973). We suggest addition of the Pt(J) intermediate to the free radical site of *TOH as most likely. Complexes of Pt(II) with carbon ligands are well known (Basolo and Pearson, 1967). However, reduction of *TOH by Pt(I) cannot be excluded here. These reactions of Pt(I) may be accurate models for cis-PDD sensitization. Reactions of Pt(J) similar to that with *TOH are probable with DNA free radicals. Reactions of the Pt(NH3)2CIO2 intermediate with cellular peroxy radicals may also be relevant to the small amount of cis-PDD sensitization reported for bacterial spores (Richmond and Powers, 1976) and cells (Richmond, Zimbrick and Hykes, 1977) in 02. Increases in pH observed after irradiation certainly reflect release of ammonia ligands as a consequence of disproportionation: 2 Pt(I) -> Pt° + Pt(II) The G-values of cis-PDD destruction in N2 (Table) indicate that in the absence of OH, the yield of cis-PDD destroyed is equivalent to G(e-aq + H) - 3.3. This fact, and the distinct appearance of both Pt metal and trans-PDD, strongly suggest that the Pt(I) intermediate (having lost both chlorides) loses cis-direction and disproportionates. Trans-PDD binds differently and to a greater extent than cisPDD to biological material, such as DNA (Pascoe and Roberts, 1974). An altered PDD binding pattern to DNA may be relevant to radiation-induced damage, since bound cis-PDD is shown to reduce the yields of thymine base residues re-
RADIATION,
cis-Pt(NH3)2CI2,
AND
DNA
23
REFERENCES leased from the irradiated cis-PDD/DNA complex. BASOLO, F., LEDERER, M., OssIcINI, L. & STEPHEN, K. H. (1963) A Paper Chromatographic Study of In N20, the G-value for cis-PDD Some Platinum(II) Compounds II. The Separation destruction is essentially half that of the of cis- and trans-Dihalogenodiammineplatinum(II) OH radical yield in this system, G(OH)Complexes. J. Chromatog., 10, 262. PEARSON, R. G. (1967) Mechanisms of 5-6, suggesting that disproportionation of BASOLO, F. &Reactions: A Study of Metal Complexes Inorganic the Pt(III) intermediate yields cis-PDD: in Solution. New York: John Wiley and Sons. DOUPLE, E. B., RICHMOND, R. C. & LOGAN, M. E. 2 Pt(111) -> Pt(II) + Pt(JV) (1977) Therapeutic Potentiation in a Mouse Mammary Tumor and an Intracerebral Rat The Pt(III), in contrast to Pt(I), Brain Tumor by Combined Treatment with cisDichlorodiammineplatinurn(II) and Radiation. J. therefore appears not to lose cis-direction, Clin. Hematol. Oncol., 7, 585. suggesting Cl- ligand retention in this HAYON, E. & SIMIC, M. G. (1973) Addition of Hydroxyl Radicals to Pyrimidine Bases and Electron intermediate. The low Rf-values of the Transfer Reactions of Intermediates to Quinones. two presumed Pt(IV) products (Table) J. Am. Chem. Soc., 95, 1029. suggests they are cationic complexes HORACEK, P. & DROBNIK, J. (1971) Interaction of cis-Dichlorodiammineplatinum(II) with DNA. (J. D. Hoeschele, unpublished results). Biochem. biophys. Acta, 254, 341. Subsequent reactions of Pt(III) and PASCOE, J. M. & ROBERTS, J. J. (1974) Interactions Pt(JV) species with cellular constituents Between Mammalian Cell DNA and Inorganic Platinum Compounds. I. DNA Interstrand Crossor bioradicals may contribute to the small Linking and Cytotoxic Properties of Platinum(II) compartment of cis-PDD sensitization Compounds. Biochem. Pharmac., 23, 1345. RAAEN, H. P. & KRAUS, F. E. (1968) Resolution of reported for bacterial systems irradiated Complex Mixtures of Nucleic Acid Bases, Nucleoin 02 or N20 (Richmond and Powers, sides, and Nucleotides by Two-Dimensional Thin1976; Richmond, Zimbrick and Hykes, Layer Chromatography on PolyethyleneimineCellulose. J. Chromatog., 35, 531. 1977). R. C. & ZIMBRICK, J. D. (1975) In vivo The radiation chemistry of cis-PDD as RICHMOND, Radiation-Induced Thymine Residue Release from it relates to the radiation sensitization of E. coli DNA. Biochem. biophys. Res. Comm., 64, 391. cells is complex. The results presented RICHMOND, R. C. & POWERS, E. L. (1976) Radiation here allow for conventional mechanisms, Sensitization of Bacterial Spores by cis-Dichloroand in addition suggest other possibilities. diammineplatinum(II). Radiat. Res., 68, 251. RICHMOND, R. C., ZIMBRICK, J. D. & HYKES, D. L. These latter include the potential for: (1977) Radiation-Induced DNA Damage and Lethality in E. Coli as Modified by the Antitumor (a) reactions of Pt intermediates (Pt(J), Agent cis-Dichlorodiammineplatinum(II). Radiat. Pt(mIJ), Pt(NH3)2C102) with bioradicals; Res., 71, 447. B. (1973) Platinum Coordination Com(b) secondary reactions of stable pro- ROSENBERG, plexes in Cancer Chemotherapy. Naturwissenducts (trans-PDD, Pt(IV) complexes) with schaften, 60, 399. cellular constituents and bioradicals; SIMIc, M. G., NETA, P. & HAYON, E. (1969) Pulse Radiolysis Study of Alcohols in Aqueous Solu(c) effects of Pt complexes or intertions. J. Phys. Chem., 73, 3794. mediates coordinated to biological ligands SIMIC, M. G. & LILIE, J. (1974) The Kinetics of Ammonia Detachment from Reduced Co(III) (e.g., DNA) at or near damaged sites. RCR acknowledges support from an NRC Research Associateship tenable at the U.S. Army NARADCO0M Laboratories, Natick, MA 01760, U.S.A.; this work partially supported by ACS grant LOI-PDT-90 and PHS grant A04-18522-02.
Complexes Based on Conductometric Pulse Radiolysis. J. Am. Chem. Soc., 96, 291. WARD, J. D. & Kuo, I. (1976) Strand Breaks, Base Release, and Post Irradiation Changes in DNA Gamma-Irradiated in Dilute 02-Saturated Aqueous Solution. Radiat. Res., 66, 485.
