Effects of PEG-ZnPP and SMA-ZnPP on proliferation and viability of neoplastic mast cells. (A) HMC-1.1 cells (●) and HMC-1.2 cells (■) were incubated in control-medium (0) or in various concentrations of PEG-ZnPP (top panel) or SMA-ZnPP (bottom panel) as indicated at 37°C for 48 hours. Uptake of ³H-thymidine was then measured. Results show the percentage of ³H-thymidine uptake compared with medium control (0 on x-axis = 100%) and represent the mean (± SD) of 3 independent experiments. (B) HMC-1.1 cells (left panels) and HMC-1.2 cells (right panels) were incubated in control medium (control) or various concentrations of PEG-ZnPP (upper panels) or SMA-ZnPP (lower panels) as indicated at 37°C for 48 hours. Then, the numbers (percentages) of apoptotic cells were determined by light microscopy. Results represent the mean (± SD) of 3 independent experiments. *P < .05 compared with control. (C) HMC-1.1 cells and HMC-1.2 cells were cultured in control medium (left panels) or medium containing SMA-ZnPP (10 μM) (right panels) at 37°C for 72 hours. Then, cells were harvested and subjected to electron microscopic examination. Typical cells are depicted. Those from cultures kept in SMA-ZnPP showed characteristic signs of apoptosis. Original magnification, 5000×. Images were captured using a Gatan Bioscan Camera model 792 and Digital Micrograph acquisition software (Gatan, Pleasanton, CA). (D) HMC-1.1 cells and HMC-1.2 cells were cultured in control medium (left panels) or medium containing SMA-ZnPP (10 μM) (right panels) at 37°C for 72 hours. Then, apoptosis was examined by a TUNEL assay. Images were obtained using a Nikon Plan Apo 40×/1.0 numeric aperture oil objective. Images were acquired from FITC-labeled cells using a Hamamatsu high-resolution digital camera (model C4242-95; Hamamatsu, Japan) and HPD-CPX32 Microsoft Windows 95 software (Microsoft, Redmond, WA). Citifluor (Agar Science, Stansted, United Kingdom) was used as imaging solution. (E) Primary neoplastic cells obtained from the bone marrow of patients with ISM, SSM, and ASM were cultured in control medium or medium containing various concentrations of SMA-ZnPP at 37°C for 48 hours. In one patient (ASM), PEG-ZnPP was also applied. After exposure to drugs, uptake of ³H-thymidine was measured. Results show the percentage of ³H-thymidine uptake compared with medium control (0 on x-axis = 100%) and represent the mean (± SD) of triplicates. (F) HMC-1.1 cells (left panels) and HMC-1.2 cells (right panels) were cultured in control medium (0 on x-axis) or medium containing either PEG-ZnPP alone or SMA-ZnPP alone (■), PKC412 alone (●), or a combination (at fixed ratio) between PKC412 and one of the 2 Hsp32/HO-1-targeting compounds (PEG-ZnPP, top panels; SMA-ZnPP, bottom panels) (▴) at the concentrations indicated. After incubation (37°C for 48 (hours), ³H-thymidine was measured. Results show the percentage of ³H-thymidine uptake compared with medium control (0 on x-axis = 100%) and represent the mean (± SD) of triplicates from 1 typical experiment.