DNA topoisomerase I is incubated in the presence or absence of drugs (including β-Lapachone), in 20 μL of relaxation buffer (50 mM Tris (pH 7.5). 50 mM KCl, 10 mM MgCl₂, 0.5 mM dithiothreitol, 0.5 mM EDTA, 30 μg/mL bovine serum albumin) for 30 min at 37°C. Reactions are stopped by adding 1% SDS and proteinase K (50 μg/mL). After an additional 1-h incubation at 37°C, the products are separated by electrophoresis in 1% agarose gel in TAE buffer (0.04 M tris acetate, 0.001 M EDTA). The gel is stained with ethidium bromide after electrophoresis. The photographic negative is scanned with an NIH image analysis system^[1].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Cytotoxicity is measured by an MTT assay. IMR-32 and JCI cells are plated in 96-well microtiter plates at a concentration of 5.0?×?10⁴ (topotecan) or 2.5?×?10⁴ (β-lapachone) cells/well/100?μL medium 24 hr prior to addition of various concentrations of topotecan or β-lapachone. The cells are then incubated for 72?hr at 37°C in a CO₂ incubator. Cell proliferation is assessed using a Cell Proliferation Kit I. Experiments are performed using four independent cultures^[4].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Male Balb/c mice are provided a commercial pellet diet and water ad libitum. After 1 week of acclimation, the mice are randomly allocated to one of the following groups (5 per group): control, β-lapachone, cisplatin (18 mg/kg, ip), and β-lapachone + cisplatin (18 mg/kg, ip). The β-lapachone groups are fed a diet containing the drug (0.066) for 2 weeks prior to cisplatin injection. All mice are sacrificed under carbon dioxide anesthesia 3 days after cisplatin injection. The blood samples are subjected to serum BUN and CRE analyses. Half of the kidney is quickly removed for histopathological and immunohistochemical (IHC) studies. The other half is stored at ?70°C until western blot assay^[3].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

• [1]. Li CJ, et al. beta-Lapachone, a novel DNA topoisomerase I inhibitor with a mode of action different from camptothecin. J Biol Chem. 1993 Oct 25;268(30):22463-8.  [Content Brief]

  [2]. Vanni A, et al. DNA damage and cytotoxicity induced by beta-lapachone: relation to poly(ADP-ribose) polymerase inhibition. Mutat Res. 1998 Jun 5;401(1-2):55-63.  [Content Brief]

  [3]. Kim TW, et al. β-Lapachone enhances Mre11-Rad50-Nbs1 complex expression in cisplatin-induced nephrotoxicity. Pharmacol Rep. 2016 Feb;68(1):27-31.  [Content Brief]