PhytohemagglutininPhytohemagglutinin (PHA) is expressed in Pichia pastoris using native signal peptides, or the Saccharomyces alpha-factor preprosequence, to direct proteins into the secretory pathway. Phytohemagglutinin induces apoptosis in human HEp-2 carcinoma cells via increasing proapoptotic protein Bax and activating caspases-3.