Activity of caspase 8, caspase 9 and caspase 3/7 in the cervical carcinoma cell line expressing VWT and VGly proteins of mumps virus. (A) Caspase 8 measured with the Caspase-Glo 8 assay (Promega) using Ac-LETD-pNA as substrate. *, statistical difference between samples treated with IFN and IFN/MG132 with respect to untreated group. §, statistical difference between samples with and without treatment with IFN and IFN/MG132. ℓ, statistical difference between samples with VWT and VGly. (B) Caspase-9 measured with the colorimetric assay Caspase 9 (BioVision) using LEDH-pNA as substrate. The absorbance was taken at 420 nm in a Shimadzu spectrophotometer 2 h after adding substrate. (C) Caspase 3 and 7 measured with the Caspase-Glo 3/7 assay system (Promega) using the substrate Ac-DEVD-pNA. Readings were taken 1 h after in the GloMax 20/20 luminometer (Promega). Each column represents the mean ± SD of three independent experiments. (In B and C, * represents the statistical difference between samples with and without IFN). Student t-test (P < 0.05).