(a) Representative brightfield microscopy of HeLaCMV-FLuc cells treated with 4 different conditioned, filtered media for 24 hours (+media+P1787; +media+P1787-Stx2; +HeLa+P1787; and +HeLa+P1787-Stx2). Note the dramatic membrane blebbing and apoptotic morphology of +HeLa+P1787-Stx2 conditioned media-treated cells. (b) Bioluminescence imaging of HeLaCMV-FLuc cells treated with increasing amounts of 4 different conditioned, filtered media for 24 hours (bar groups, left to right: 17%, 29%, 44% of total volume per well). *p<0.0005 compared to all other treatments. Inset represents PCR amplification of Stx2A/B mRNA from P1787-Stx2 transformed SB300A1 co-cultured with HeLa cells.