The development of new anticancer agents derived from natural resources requires 
a rapid identification of their molecular mechanism of action. To make this step 
short, we have initiated the proteomic profiling of HeLa cells treated with 
anticancer drugs representing a wide spectrum of mechanisms of action using 
two-dimensional difference gel electrophoresis (2D-DIGE). Unique proteome 
patterns were observed in HeLa cells treated with the HSP90 inhibitor 
geldanamycin, and were similar to the patterns induced by radicicol, a 
structurally different HSP90 inhibitor. On the other hand, etoposide and 
ICRF-193, compounds claimed to be topoisomerase II inhibitors, showed different 
proteomic profiles, which reflect their different biological activities as 
revealed by cell-cycle analysis. Thus far, combined data from 19 compounds have 
allowed their successful classification by cluster analysis according to the 
mechanism of action.