While in CT26 tumor cells, PSG-1 exerts its anti-tumor effect mainly through the activation of cyclic AMP (cAMP)/protein kinase A (PKA) pathway, Ca2+/PKC pathway or mitochondria-mediated apoptotic pathway to increase the apoptotic rate of tumor cells, decrease tumor weight and increase the immune organ index to activate host immune function of tumor cell-bearing mice [96]. Here, PSG1 is linked to neoplasm.