Ricardo J. Parker

Platinum‐DNA adducts assayed in leukocytes of patients with germ cell tumors measured by atomic absorbance spectrometry and enzyme‐linked immunosorbent assay

Background. Platinum‐DNA adducts can be measured in peripheral blood cells, and high adduct levels have previously been correlated with favorable clinical response to platinum‐based therapy in patients with germ cell tumors and ovarian cancer.

Effect of liposome encapsulation of a fluorescent dye on its uptake by the lymphatics of the rat

The fluorescent dye carboxyfluorescein (CF), entrapped in liposomes and administered by intraduodenal injection to thoracic duct-cannulated rats, was not detected in thoracic duct lymph at any time after dosing. However, the dye was present in blood, and in higher concentration in portal than in systemic blood. Similarly, free CF given intraperitoneally (i.p.) appeared to be absorbed into portal blood and was quickly cleared from the circulation, with less than 1% of the injected dye being recovered in thoracic duct lymph within 24 h after dosing. In contrast, 27% of the injected CF was recovered in thoracic duct lymph of rats receiving CF/liposomes i.p. These findings indicate that liposomal entrapment effectively limits passage of CF into the splanchnic blood vessels while enhancing the lymphatic uptake of the dye from the peritoneal cavity.

Synergistic effect and possible mechanisms of tumor necrosis factor and cisplatin cytotoxicity under moderate hyperthermia against gastric cancer cells.

AbstractBackground: Peritoneal carcinomatosis is a difficult management problem, and intraperitoneal treatment approaches may provide an opportunity to intensify dose and minimize toxicity. The current experiments were conducted to characterize the cytotoxic effects of cisplatin (cDDP), tumor necrosis factor (TNF), and hyperthermia (HT) on a gastric cancer cell line in vitro under conditions achievable with intraperitoneal treatment. Methods: Seoul National University gastric cancer cell line (SNU-5), a poorly differentiated gastric cancer cell line, was tested for sensitivity to various doses of cDDP, TNF, or combinations of the two at normothermia (37°C) or HT (42.5°C). The effect of TNF on cellular rates of cDDP accumulation, efflux, and cDDP-DNA adduct formation were evaluated using atomic absorbance spectrometry with Zeemen background correction. Results: During a 2-h exposure to various doses of cDDP with HT, we observed a supraadditive cytotoxicity of SNU-5 with 1 to 50 µg/ml of TNF (p2=0.0001). In the presence of the three-agent combination (HT, TNF, and cDDP) we observed statistically significant increases in total cellular accumulation of cisplatin (p2=0.016); a nonsignificant decrease in cellular efflux of drug (p2=0.098); and a 40% increase in persistent cisplatin DNA damage as measured by atomic absorption spectrophotometry (p2=0.06). These patterns were specifically not seen with the combinations of cDDP and HT, or cDDP and TNF. Conclusions: These data provide the experimental basis for the use of TNF and cDDP with HT in the treatment of gastric cancer and support the investigation of these agents in vivo in the regional treatment of peritoneal carcinomatosis.

Effect of cadmium on human ovarian cancer cells with acquired cisplatin resistance

Cadmium (Cd) dichloride is a compound that has teratogenic, mutagenic, and carcinogenic properties. Recent reports have suggested the possibility that this compound may also have tumor suppressive properties in some settings. For these reasons, we have studied the subcellular pharmacological profile of elemental cadmium in human ovarian cancer cells, when administered as cadmium dichloride. The cell lines A2780 and A2780/CP70 were used, which are well characterized with respect to their cellular response to platinum-based compounds. Cd was measured in all experiments with the use of atomic absorbance spectrometry with Zeeman background correction. In both cell lines, there were direct relationships between; drug dose and cellular accumulation of drug; cellular accumulation of drug and DNA damage levels; and DNA damage levels and cytotoxicity. These cell lines differed in that the cisplatin-resistant A2780/CP70 cell line, was also comparatively resistant to cadmium dichloride. This enhanced cellular resistance appeared to be mediated through decreased drug accumulation, and increased cellular tolerance to higher levels of DNA damage. Total genomic DNA repair and cytosolic inactivation of drug appeared not to differ substantively between these two cell lines.

Peripheral Blood Leukocytes as a Surrogate Marker for Cisplatin Drug Resistance: Studies of Adduct Levels and the Repair Gene ERCC1

Cisplatin and its analogs are potent chemotherapeutic agents in the treatment of ovarian cancer, testicular cancer, and other malignancies. Studies by this group have shown that the level of platinum-DNA adduct formed in leukocyte DNA is directly related to disease response in ovarian cancer (Reed et al, 1987) and testicular cancer (Reed et al, 1988a), and that the level of adduct attained is influenced by the persistence of the adduct in leukocyte precursors in some patients for no less than 28 days (Reed et al, 1986). Because this persistence has been observed in some patients but not in others (Reed et al, 1986), we have been interested in the study of those factors that may influence persistence, and whether these factors are directly related to clinical parameters and/or subcellular parameters of cisplatin drug resistance. We have assessed the relative contribution of clinical parameters to disease response in a cohort of patients with ovarian cancer, and we compare those data to platinum-DNA adduct measurements in leukocyte DNA from these same individuals.