Silkworm pupae (Bombyx mori) are a high-protein nutrition source consumed in China\nsince more than 2 thousand years ago. Recent studies revealed that silkworm pupae have therapeutic\nbenefits to treat many diseases. However, the ability of the compounds of silkworm pupae to\ninhibit tumourigenesis remains to be elucidated. Here, we separated the protein of silkworm pupae\nand performed alcalase hydrolysis. Silkworm pupa protein hydrolysate (SPPH) can specifically\ninhibit the proliferation and provoke abnormal morphologic features of human gastric cancer cells\nSGC-7901 in a dose- and time-dependent manner. Moreover, flow cytometry indicated that SPPH\ncan induce apoptosis and arrest the cell-cycle in S phase. Furthermore, SPPH was shown to provoke\naccumulation of reactive oxygen species (ROS) and depolarization of mitochondrial membrane\npotential. Western blotting analysis indicated that SPPH inhibited Bcl-2 expression and promoted Bax\nexpression, and subsequently induced apoptosis-inducing factor and cytochrome C release, which\nled to the activation of initiator caspase-9 and executioner caspase-3, cleavage of poly (ADP-ribose)\npolymerase (PARP), eventually caused cell apoptosis. Moreover, SPPH-induced S-phase arrest was\nmediated by up-regulating the expression of E2F1 and down-regulating those of cyclin E, CDK2\nand cyclin A2. Transcriptome sequencing and gene set enrichment analysis (GSEA) also revealed\nthat SPPH treatment could affect gene expression and pathway regulation related to tumourigenesis,\napoptosis and cell cycle. In summary, our results suggest that SPPH could specifically suppress cell\ngrowth of SGC-7901 through an intrinsic apoptotic pathway, ROS accumulation and cell cycle arrest,\nand silkworm pupae have a potential to become a source of anticancer agents in the future.
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