Tween-80 Alters Natural Resistance of Sarcoma-180 to Bouvardin (NSC 259968)

Effect of Tween 80 on Adriamycin Cytotoxicity in Murine P388 Leukemia

Studies on mice bearing P388 adriamycin sensitive and resistant lymphocytic leukemia were carried out to compare antitumor activity of adriamycin dissolved in Tween 80 (10 % in distilled water) with that of adriamycin dissolved in distilled water alone. The antitumor activity of adriamycin dissolved in acqueous solutions of Tween 80 was higher than that of adriamycin dissolved in distilled water against P388 leukemia sensitive to adriamycin. However, no change in the activity was observed in P388 leukemia resistant to adriamycin when the drug was administered either in acqueous solution of Tween 80 or in distilled water alone.

Inhibition of Macromolecular Synthesis in P388 Mouse Leukemia Ascites Cells by Bouvardin (NSC 259968)

Bouvardin, a new antineoplastic plant product, inhibits macromolecular synthesis in P388 cells in a dose-dependent manner. At the same concentration of bouvardin, protein synthesis was inhibited to a greater extent than the synthesis of DNA and RNA. There was a reversal of inhibition of both DNA and RNA synthesis after the cells were washed free of bouvardin. However, there was partial reversal of inhibition of protein synthesis when the cells were washed free of the drug.

Effect of induced acidosis on cytotoxicity of anticancer drugs

The effect of adriamycin (ADR), vincristine (VCR), mitoxantrone (MTN) and cis-platin (PtCl) at acidic pH on the incorporation of 3H-thymidine (3H-TdR) was studied in vitro on P388 murine leukemia cells. The incorporation was inhibited at low pH by the four drugs used. In order to induce acidosis in tumor bearing mice, 6 g/kg glucose was administered intraperitoneally. The lowest pH that could be obtained was 6.8 two hours after glucose administration. The drugs ADR, VCR, MTN and PtCl administered to tumor-bearing mice 2 h following induction of acidosis resulted in significant increase in the life span of the tumor bearing mice.

Modulation of in vitro response to adriamycin by verapamil in murine P388 leukaemia, Ehrlich ascites carcinoma and sarcoma 180

Experiments were carried out in vitro on adriamycin (ADR) accumulation and cytotoxicity alone and in combination with calcium channel antagonist, verapamil (VRP), in ascites murine tumour models of Ehrlich carcinoma (EAC), sarcoma 180 (S180) and P388 lymphocytic leukaemia (P388). The cytotoxicity was assayed as the inhibition of [3H]-thymidine incorporation into the cellular DNA. ADR, a broad-spectrum anticancer drug, at a concentration of 10 micrograms/ml showed a cytotoxic effect in the order S180 greater than P388 greater than EAC. VRP alone exhibited the DNA synthesis inhibiting activity. The enhanced DNA biosynthesis inhibition of ADR along with VRP was maximal in S180 and marginal in P388 and EAC. The ADR retention after 3 hr of incubation in these tumour models correlated with the cytotoxicity. VRP enhanced the accumulation of ADR in all these cell lines. The property of potentiation in the activity and accumulation of ADR in these tumours exposed to a non-toxic concentration of VRP can best be utilized in cancer chemotherapy where the massive cytotoxic therapy, with a single large dose of ADR, can be substituted with a low dose, along with this drug-response modulator, for better therapeutic results.

Augmentation of Hydroxyurea Cytotoxicity by Sintamil in Human Chronic Myeloid Leukemia Cells

The in vitro effect of sintamil, as a modulator alone and in combination with hydroxyurea (HU), on cytotoxicity was studied in 16 cases of human chronic myeloid leukemia (CML). We investigated the cytotoxicity of the drugs as a function of the exposure dose (HU, 10−4 M; sintamil, 10 μg/ml) and the exposure time (1 h) to the agent. Cytotoxicity was evaluated as the inhibition of incorporation of [3H-methyl]thymidine in the nucleic acids of CML cells. Cytotoxicity of HU was greatly enhanced (P < 0.001) by 1 h exposure of the CML cells to sintamil. The present data indicate that sintamil potentiates the cytotoxic activity of HU in CML cells.

Enhancement of the in vitro cytotoxicity of bouvardin by verapamil alone and combined with hyperthermia in Sarcoma 180 and Ehrlich ascites carcinoma cells

The cytotoxic effect of bouvardin (BVD) a protein synthesis inhibitor was studied separately and in combination with verapamil (VRP), a vasodilator and hyperthermia (43 degrees C) against Sarcoma 180 (S 180) and Ehrlich ascites carcinoma (EAC) tumour cells in vitro. S 180 cells exhibited natural resistance to hyperthermia and BVD, whereas EAC tumour cells were found to be sensitive. VRP alone did not show cytotoxicity to either tumour cells. A combination of BVD and VRP at an elevated temperature resulted in a greater cell kill in the EAC tumour cell line whereas the natural resistance of S 180 tumour cells to the drug BVD and hyperthermia was circumvented by combination with VRP. Combination of BVD, hyperthermia and VRP resulted in greater cell kill, compared to separate treatment with the single agents. The cytotoxicity was evaluated by comparing the inhibition of incorporation of 3H-thymidine in treated cells to that in untreated cells.

Reversal of natural resistance to bouvardin (NSC 259968) in sarcoma 180 cells in vitro and in vivo by verapamil

Reversal of natural resistance to bouvardin (NSC 259968) has been attained in vitro and in vivo, by the calcium influx blocker verapamil in sarcoma 180 cells insensitive to bouvardin. Verapamil increased the in vitro lethality of the tumor cells following exposure with cells for 1 and 3 h as a result of the cytotoxic effect of bouvardin. Similar results were observed in vivo when the tumor cells were exposed to verapamil and then treated with bouvardin, showing a significant percent increase in the lifespan to 30% and 45%. This suggested that this calcium channel blocker had interacted with tumor cell membrane to modulate the response of the cells, and make them more amenable to the drug action.