The up-regulation of HSP70 is specific for cytotoxic treatment with TC-A. B-CLL cells of 5 patients were left untreated or treated with the following cytotoxic agents: TC-A, vincristine (Vincrist), cisplatin (cispl), dexamethasone (DEX), mafosfamide (Mafosf), and fludarabine phosphate (Fludara) at the indicated concentrations. Brefeldin A (Brefeld A), a known inducer of ER stress, was used as positive control. The expression of HSP70 was determined in permeabilized cells by immunofluorescence staining followed by flow cytometric analysis. The differences of basal and TC-A—induced HSP70 expression levels are presented as mean fluorescence intensities (Δ MFI). The mean values representing the differences between TC-A—induced apoptosis minus spontaneous apoptosis of at least 4 independent experiments are presented in the boxes at the top.