SERPINB5 and neoplasm: To determine whether maspin overexpression regulates the gene expression of Bcl-2 family during apoptosis, a quantitative ribonuclease protection assay (RPA) was carried out using radiolabeled antisense probes for Bcl-2 family genes (RPA kit, BD PharMingen, Inc., CA), and RNAs isolated from tumor cells under apoptotic condition.