Differential anti-proliferative properties of novel hydroxydicarboxylatoplatinum(II) complexes with high or low reactivity with thiols

EDTA enhances the antitumor efficacy of intratumoral cisplatin in s.c. grafted rat colon tumors

We have investigated whether EDTA, a calcium chelator, could improve the accumulation of platinum in tumors and enhance the antitumor efficacy by increasing drug diffusion through the extracellular tumor matrix. Intratumoral injection of 0.3 mg/kg cisplatin combined with 10 mg/ml EDTA in 2 ml saline serum led to tumor cure in four of eight rats and produced major tumor regression in the other animals. In contrast, intratumoral injection of cisplatin alone or EDTA alone had no antitumoral effect. EDTA increased platinum accumulation both in vivo and ex vivo in the PROb tumors. EDTA alone was cytotoxic at a concentration of 10 mg/ml, but neither increased platinum accumulation nor cisplatin toxicity on cultured PROb colonic cancer cells. We conclude that EDTA could be a useful and well-tolerated adjuvant for enhancing intratumoral cisplatin chemotherapy.

Radiosensitizing properties of novel hydroxydicarboxylatoplatinum(II) complexes with high or low reactivity with thiols: two modes of action

We examined radiosensitizing properties of two novel platinum complexes (ethylenediamine(L-malato)platinum(II)), Pt1 and bis(1-ethylimidazole(L-malato)platinum(II)), Pt4. Initial double strand break (DSB) level and DSB rejoining were measured, using pulse field gel electrophoresis (PFGE) in human G1 phase lymphocytes subjected to Pt complex treatment alone and in combination with 10Gy of X-rays. Effects of Pt complex pre-treatment followed by X-irradiation were examined on survival (clonogenic ability) and growth (48 h growth tests) in Chinese hamster ovary (CHO-K1), xrs6 and L5178Y (LY) cells (LY-R and LY-S sublines). Cell cycle distributions of CHO cells after drug treatment were determined with the use of flow cytometry. Pt1 slowed down rejoining of X-ray induced DSB. It exerted a more than additive lethal effect on CHO-K1 cells but not on L5178Y cells subjected to combined Pt complex treatment and X-irradiation. In xrs6 cells the effect of combined Pt1+X treatment was additive. We conclude that, as earlier proposed for other Pt complexes, the radiosensitizing effect of Pt1 is connected with converting repairable DNA damage into irrepairable one (mode (i) of action). The requirements for this mode of sensitization are functional DNA repair systems (nucleotide excision repair (NER) and non-homologous end-joining (NHEJ)). Pt4 does not slow down DSB rejoining. It shows a considerable ability to arrest cells in G2 phase. We assume that Pt4 pre-treatment arrests cells in G2 phase and thus sensitizes to X-rays these cells that have a radiosensitive G2 phase (mode (ii) of action).

Differential toxic effect of cis-platinum(II) and palladium(II) chlorides complexed with methyl 3,4-diamine-2,3,4,6-tetradeoxy-alpha-L-lyxo-hexopyranoside in mouse lymphoma cell lines differing in DSB and NER repair ability

The aim of this work was to test the cytotoxicity of newly synthesized cis-type complexes of platinum(II) and palladium(II) dichloride with methyl 3,4-diamine-2,3,4,6-tetradeoxy-alpha-L-lyxohexopyranoside, [M(C(7)H(16)N(2)O(2))Cl(2)].H(2)O, against two mouse lymphoma cell lines (L5178Y) differing in their double strand breaks and nucleotide excision repair ability. cis- Diaminedichloroplatinum (CDDP) was used as a reference compound. The toxicity of Pt(C(7)H(16)N(2)O(2))Cl(2) appeared to be similar for both cell lines: IC(50) is 8 microM for L5178Y-R cells and 12 microM for L5178Y-S cells, respectively. In contrast, the palladium complex was found to be more toxic for the LY-R cells than for the LY-S cells. The cytotoxicity of both compounds was compared with their ability to induce DNA crosslinks, as measured by the modified comet assay. CDDP caused retardation of the DNA migration induced by 2 Gy of the X-irradiation in a dose-dependent manner. The ability of Pd(C(7)H(16)N(2)O(2))Cl(2) to retard X-ray induced DNA migration was more pronounced than its platinum analogue and CDDP (see Fig. 6). However, this was not reflected in the toxicity of the compound. Such results indicate that these two compounds may cause a different type of DNA damage and/or that the DNA damage caused by the palladium(II) compound was dealt with in a different manner from that induced by the platinum(II) complex.

Structure and biological activity of cationic [PtLCl(DMSO)]NO(3).DMSO complex containing a chelated diaminosugar: methyl-3,4-diamino-2,3,4,6-tetradeoxy-alpha-L-lyxopyranoside

Cationic platinum(II) complex [Pt(C(7)H(16)N(2)O(2))(DMSO)Cl]NO(3).DMSO containing one chloride anion, methyl-3,4-diamino-2,3,4,6-tetradeoxy-alpha-L-lyxopyranoside (C(7)H(16)N(2)O(2)) and dimethylsulfoxide (DMSO) molecules forming a square-plane has been prepared and characterised, both spectroscopically and by single-crystal X-ray diffraction. Biological tests performed using leukemia L1210 cells have shown that toxicity of the title complex is similar to that of cisplatin.