Spheroid cells are resistant to chemotherapy <i>in vitro</i>.

<p>(A) More spheroid cells were killed by Cisplatin than parent cells. The same numbers of spheroid and parent cells were cultured in CM with indicated amount of Cisplatin for 2 days and numbers of cells from different time points were determined. (B) More parent cells survived after Cisplatin treatment for 48 h (Left). However, 8 days later, only spheroid cells were growing while parent cells disappeared (Right). (C) Spheroid and parent cells were treated with indicated amount of Cisplatin for 24 h, washed, and 300 of survived cells/well were cultured in CM for another 10 days, cell colonies were shown after crystal violet staining. The same clonogenic survival assays were repeated twice with similar results. Colonies formed (>5 cells) after 10 days of growth were counted and average and SD were shown. *,p<0.05.