Function of PrPC (1-OPRD) in biological activities of gastric cancer cell lines

Approximately 10-15% of the human prion disease is inherited and one of the important genetic mutations occurs in the octapeptide repeat region of prion protein gene. One of the variants, one octapeptide repeat deletion (1-OPRD), existed in several gastric cancer cell lines and its mutation frequency was higher in gastric cancer cases. However, the biological functions of it remain unknown. Wild-type and mutation forms of PrP(C) were cloned and transfected into gastric cancer cells. Cell apoptosis, adhesion, invasion, multidrug resistance (MDR) and proliferation were, respectively, investigated. Different expressed genes were screened by gene array and proved by PT-PCR. Further, luciferase report assay was used to explore the transcriptional activation of target genes. Forced overexpression PrP(C) (1-OPRD) could promote the gastric cancer cells SGC7901 growth through facilitating G1- to S-phase transition in the cell cycle. PrP(C) (1-OPRD) could also inhibit apoptosis, and promote adhesion, invasion and MDR in SGC7901. However, it exhibited no significant difference between wild-type PrP(C) (1-OPRD) and PrP(C) on apoptosis, invasion or MDR effects. Further experiments indicated that PrP(C) (1-OPRD) could trigger the transactivation of cyclinD3 besides cyclinD1 to promote cell transition and proliferation. Overexpression of PrP(C) (1-OPRD) might promote the proliferation of gastric cancer cells at least partially through transcriptional activation of cyclinD3 to accelerate the G1-/S-phase transition. The promoting proliferation effect of PrP(C) (1-OPRD) was more than that of wild-type PrP(C). However, they showed no difference on apoptosis, adhesion, invasion or MDR effects of gastric cancer cells.