Cell experiment:

The U251, U87, GSCs-U251 and GSCs-U87 cells are seeded at a density of 2×104 cells per well in 96-well plates separately, and incubated for 24 h. Cells are administered with Shikonin and Topotecan (0.02, 0.2, 2, 20, 40 μM). After the treatment, 10 μL of cell counting kit-8 (CCK-8) is added into each well for additional 1-hour incubation at 37℃. The optical density (OD) is read with a microplate reader at 450 nm[1].

Animal experiment:

Mice[2] For subcutaneous xenograft studies, we used SK-N-BE, SH-SY5Y, KHOS, and RH30. 1×106 cells are implanted subcutaneously into the inguinal fat pad of each of nonobese diabetic/severe combined immune deficient (NOD/SCID) mice. When tumors reached 0.5 cm in diameter, the animals are randomized into 4 groups and treated daily by oral gavage. The animals are grouped as: Control group, LDM Topotecan group or LDM TP (1 mg/kg Topotecan), Pazopanib group or PZ (150 mg/kg Pazopanib) and combination group or TP+PZ (1 mg/kg Topotecan+150 mg/kg Pazopanib). To compare pulse Topotecan with LDM TP in KHOS osteosarcoma model, PZ is replaced by weekly oral dose of pulse Topotecan (SKF104864) or Pulse TP (15 mg/kg Topotecan (SKF104864)). The criteria for endpoint are tumor sizes exceeding 2.0 cm in diameter or animals showing signs of morbidity. The tumor sizes are measured on a daily basis until the endpoint or sacrifice. The long (D) and short diameters (d) are measured with calipers. Tumor volume (cm3) is calculated as V=0.5×D×d2. When the endpoint is reached or at the end of the treatment, the animals are sacrificed by cervical dislocation.

Topotecan (SKF104864) is an inhibitor of topoisomerase 1 and semisynthetic analogue of camptothecin [1].

Topotecan (SKF104864) has been reported to have a potent antitumor activity against tumors in murine models. In addition, Topotecan has also shown the potent effect against intravenously implanted P388 leukemia and both intravenously and subcutaneously implanted Lewis lung carcinoma. Topotecan has noted the activity against subcutaneously implanted solid tumors including chemorefractory tumors and human colon carcinoma xenograft HT-29. Topotecan has been found to induce regressions in the lung tumor model (Lewis lung carcinoma and B16 melanoma), compared to camptothecin and 9-amino-camptothecin. In the preclinical toxicology studies, Topotecan has been revealed to have a concentration-dependent, reversible and limited toxoicity to rapidly proliferation tissues such as bone marrow and gastro-intestinal epithelium [1].

References:
[1] Creemers GJ1, Lund B, Verweij J. Topoisomerase I inhibitors: topotecan and irenotecan. Cancer Treat Rev. 1994 Jan;20(1):73-96.