Cell experiment:

MCF-7, EMT-6/AR1, HeLa and MDA-MB-231 cells are seeded in 96 well plates. Subsequently, cells are incubated with vehicle (0.1% DMSO) or different concentrations (1-1000 pM) of Ansamitocin P3 for 48 h in MCF-7 cells and 24 h for EMT-6/AR1, HeLa and MDA-MB-231 cells, respectively. The half maximal inhibitory concentration of cell proliferation (IC50) for Ansamitocin P3 is determined by sulforhodamine B assay. Four independent experiments are carried out in MCF-7 cells and three independent sets of experiments are performed in EMT-6/AR1, HeLa and MDA-MB-231 cells[2].

Ansamitocin P-3, a natural product, is maytansinoid which showed potent cytotoxicity against the human solid tumor cell lines A-549 and HT-29 with ED50 of 4 x 10 -7, 4 x 10 – 7 μg/ml, respectively. [1]
Cytotoxic agents remain an important strategy in chemotherapy. In an activity-directed isolation and identification, ansamitocin P-3 was obtained from the active methanol extracts of two mosses.
Furthermore, the compound showed great cytotoxicity against several tumor cells. [1]
Ansamitocin P-3 is a maytansinoid isolated in very low yield from two members of the moss family Thuidiaceae, Claopodium crispifolium (Hook.) Ren. & Card. and Anomodon attenuatus (Hedw.) Hueb. Further biological evaluation of ansainitocin P-3 showed potent cytotoxicity against the human solid tumor cell line systems A-549 lung carcinoma cells, HT-29 colon adenocarcinoma cells and MCF-7 breast adenocarcinoma cells at ED50 of 4 x 10 -7, 4 x 10 - 7, 2 x 10 -6 μg/ml. respectively. [2]
Ansamitocin P-3 exhibited inhibition of cilia regeneration of partially deciliated Tetrahymena. The regeneration of cilia in Tetrahymena was assayed by observing recovery of motility of the deciliated cells which are nonmotile after being deciliated. After 60 min of incubation, more than 95% of partially deciliated Tetrahymena cells in the recovery buffer were fully motile. Ansamitocin P-3 completely inhibited cilia regeneration of Tetrahymena at 1 μM. Moreover, recovery of motility of partially deciliated cells after release from inhibition by 2 μM ansamitocin P-3. [2]
References：
[1]. Suwanborirux, K., et al. "Ansamitocin P-3, a maytansinoid, fromClaopodium crispifolium andAnomodon attenuatus or associated actinomycetes."Experientia 46.1 (1990): 117-120.
[2]. Tanida, Seiichi, Eiji Higashide, and Masahiko Yoneda. "Inhibition of cilia regeneration of Tetrahymena by ansamitocins, new antitumor antibiotics."Antimicrobial agents and chemotherapy 16.1 (1979): 101.