SN-38 (NK012) is the active metabolite of Irinotecan, a DNA topoisomerase I (Topo I) inhibitor, which inhibits DNA and RNA synthesis (IC50=0.077/1.3 μM). SN-38 has antitumor activity and induces autophagy.

DNA synthesis:0.077 μM, RNA synthesis:1.3 μM

方法：肺癌细胞 LLC、A549 和 H358 用 SN-38 (10-1000 nM) 处理 48 h，使用 MTT assay 检测细胞活力。
结果：SN-38 在 10 nM 浓度下开始表现出作用，并在 100 nM 下诱导约 50% 的细胞死亡。[1]
方法：结直肠癌细胞 KM12C、KM12SM 和 KM12L4a 用 SN-38 (2.5 µg/mL) 处理 4-48 h，使用 Flow cytometry 检测细胞周期和凋亡。
结果：SN-38 诱导的 S 期和 G2 期阻滞，KM12L4a 细胞以时间依赖性反应最强。KM12SM 和 KM12L4a 细胞系的凋亡率随时间增加，但在 KM12C 细胞中没有这种变化。[2]

方法：为检测体内抗肿瘤活性，将 SN-38 (2 mg/kg) 单次腹腔注射给腹膜腔内移植 LLC 细胞的 C57BL/6 小鼠。
结果：单次腹腔注射 SN-38 可显著减弱 LLC 肿瘤的生长，使肿瘤生长减少 22.7%。[1]
方法：为检测体内抗肿瘤活性，将 SN-38 (10 mg/kg in 0.5% carboxymethylcellulose sodium，腹腔注射) 和 gefitinib (100 mg/kg，皮下注射) 携带人口腔鳞状肿瘤 HSC-2 的 BALB/c nude 小鼠，每周五次，持续三周。
结果：仅 gefitinib 治疗和 gefitinib 加 SN-38 治疗在肿瘤生长抑制方面没有显著差异。然而，当治疗停止后继续进行肿瘤测量时，仅吉非替尼组的一些肿瘤显示出新的生长。[3]

Topoisomerase I Assay: One unit (the minimum amount for full relaxation of 0.5 μg SV40 DNA under the conditions of this study) of topoisomerase I, 0.5 μL of the test compounds, and 0.5μg SV40 DNA are added sequentially to the reaction buffer, which is composed of 25 mM Tris-HCl (pH 7.5), 50 mM KC1, 5 mM MgCl2, 0.25 mM EDTA disodium salt, 0.25 mM dithiothreitol, 15μg /mL bovine serum albumin, and 5% glycerol. Then, the reaction mixture (50 μL) is incubated for 10 min at 37 °C, and the reaction is terminated by treatment with 7.5 μL of a solution consisting of 1% sodium dodecyl sulfate, 20 mM EDTA disodium salt, and 0.5 mg/mL proteinase K for an additional 30 min at 37°C. The samples are mixed with 5 μL of the loading buffer containing 10 mM Na2HPO4, 31.3% sucrose, and 0.3% bromophenol blue. Relaxed (form Ir) DNA is separated from supercoiled (form I) and nicked (form II) DNA by electrophoresis on 0.8% agarose gel at 50 mA and 20 V for 17 h in the presence of 2 μg/mL chloroquine, 10 mM EDTA, 30 mM NaH2PO4, and 36 Mm Tris-HCl (pH 7.8). After electrophoresis, the gel is stained with 0.05% ethidium bromide and photographed with UV light (302 nm). The amount of DNA is quantified using a densitometer.

MTT assay(Only for Reference)