Prolonged quercetin administration diminishes the etoposide-induced DNA damage in bone marrow cells of rats

The DNA damage in bone marrow cells induced by etoposide (E) injected intraperitoneally to rats (100 mg/kg b.w.) decreased to the control level when quercetin (Q) was administered subcutaneously for 10 consecutive days (40 mg/kg b.w.per day) before E was injected. The antioxidant power (FRAP assay) increased significantly after Q or E compared with control rats but did not change when Q preceded the E injection. The superoxide dismutase activity significantly increased in Q+E-treated rats compared with quercetin given alone. The study provides evidence that Q protects bone marrow cells against long-lived E-induced DNA damage and alters the redox balance in lung tissue.

Effects of modifying topoisomerase II levels on cellular recovery from radiation damage

Effects of Modifying Topoisomerase II Levels on Cellular Recovery from Radiation Damage. Experiments were performed with the budding yeast, Saccharomyces cerevisiae, to test whether DNA topoisomerase II is involved in repair of DNA damage induced by ionizing radiation. Topoisomerase II was inactivated by use of a temperature-sensitive mutation. Enzyme inactivation increased cellular radiosensitivity, blocked the restitution of broken chromosomes, assayed by pulsed-field gel electrophoresis, and prolonged the induction of a DNA damage-inducible gene (RNR3). Overexpression of the topoisomerase II gene did not alter cellular radiosensitivity. The data support a role for topoisomerase II in the repair of DNA strand breaks.

Inhibition of potentially lethal and sublethal damage repair by camptothecin and etoposide in human melanoma cell lines

We investigated the ability of camptothecin (CPT), an inhibitor of topoisomerase (topo) I, and etoposide (VP-16), an inhibitor of topo II, to potentiate X-radiation response and to inhibit the repair of potentially lethal damage (PLDR) and sublethal damage (SLDR) in confluent cultures of a radioresistant (Sk-Mel-3) and a radiosensitive (HT-144) human melanoma cell line. CPT or VP-16 were present both during irradiation and during the subsequent delayed plating period allowed for repair of X-radiation damage. When the direct toxicities of CPT or VP-16 were corrected for, we found that a dose of either drug that killed approximately 15% of the clonogenic cells potentiated the effects of radiation differentially on the cell lines. CPT and VP-16 inhibited the increase in survival brought about by delayed plating of HT-144 but not Sk-Mel-3 cells. In both cell lines, CPT inhibited SLDR but not PLDR. VP-16 also inhibited SLDR in both cell lines, however, in contrast with CPT, it also inhibited PLDR in HT-144 cells. Our results therefore suggest that either topo I and II are both implicated in the repair of X-radiation damage, or that the lesions formed by CPT and VP-16 with DNA are able to impair the processing of X-radiation repair. In addition, we found that in the absence of the topo inhibitors, the two cell lines repaired similar amounts of PLD from an isosurvival level. Sk-Mel-3, however, repaired significantly increased SLD from an isosurvival level (about three-fold, p < 0.05) compared with HT-144.

Combined modality treatment using BID radiation for locally advanced non-small cell lung carcinoma

BACKGROUND

From February 1988 to August 1991, 82 patients were treated on Phase II trial of split-course multimodality treatment for locally advanced, non-small cell lung cancer (NSCLC).

METHODS

Treatment consisted of twice-daily radiation (150 cGy/fraction) delivered with concomitant infusional cisplatin, etoposide, and fluorouracil for 1 week every third week. Patients were classified before initial treatment as either potentially resectable (eligible for surgery [ES]) or ineligible for surgery (IES). The ES group consisted of 38 Stage IIIA and 7 Stage IIIB patients. The IES group had 5 patients staged as IIIA and 32 staged as IIIB. Most patients were staged clinically. ES patients received three cycles of treatment (39 Gy) before resection. IES patients received four cycles (60 Gy) delivered with curative intent.

RESULTS

Thirty-nine of 45 ES patients underwent resection. The pathologic response rate was 27%. Three-year actuarial local control was 86% for 41 evaluable ES patients. Three-year actuarial survival for the whole ES group was 39%, with a median follow-up for living patients of 32 months. The IES group faired less well, with an 18% 3-year actuarial survival. Treatment was well tolerated with a median weight loss of one-half pound, mild or moderate pneumonitis in 5%, mild esophagitis in 15%, and severe nausea and/or vomiting in 10% of patients. Treatment-related mortality was 5%.

CONCLUSIONS

Patients treated with conventional radiation alone for Stage III NSCLC are rarely cured. This well tolerated Phase II study demonstrated encouraging results for such patients. Both local control and survival appeared promising, especially in patients rendered resectable after combined-modality treatment.

Rapid and sensitive high-performance liquid chromatographic assay for novobiocin in human serum

In this paper we present a new HPLC method for the determination of novobiocin in human serum. The assay uses mitomycin C as an internal standard, protein precipitation with acetonitrile, an ODS reversed-phase column with an isocratic mobile phase of acetonitrile-0.01 M phosphoric acid (80:20, v/v), and UV detection at 340 nm. The assay has a lower limit of quantitation of 1 microgram/ml and is linear over the range of 1-1000 micrograms/ml. The assay is ideally suited for use in clinical trials as it requires minimal amounts of serum, is highly sensitive and reproducible, is performed with minimal sample preparation, and involves a short run time. It should prove important in evaluating the potential of novobiocin as a means to modulate resistance to antineoplastic chemotherapy and in therapeutic drug monitoring of the growing number of patients receiving novobiocin to control methicillin-resistant Staphylococcus aureus infections.

Interaction between 2N-methyl-9-hydroxyellipticinium and ionizing radiation in CHO cells

Incubation with 2N-methyl-9-hydroxyellipticinium (NMHE) increases the killing of gamma-irradiated CHO cells. The main effect is observed in the case of exponentially growing cells which are also more sensitive to the drug alone than plateau phase cells. Radiosensitivity increases with drug concentration and incubation time in the presence of the drug until a plateau value. However, the presence of NMHE in the culture medium inhibits neither the repair of sublethal nor potentially lethal damage. The influence of different ellipticine derivatives on the cell radiosensitivity was measured. The results show that only the hydroxylated derivatives (NMHE and 9-hydroxyellipticinium), which covalently bind to nucleic acids, increase the cellular sensitivity to ionizing radiations, whereas the non-hydroxylated derivative, 2N-methyl-ellipticinium, has no influence on cell radiosensitivity.