Induction of Gastric Cancer by Successive Oncogenic Activation in the Corpus

Background & Aims Metaplasia and dysplasia in the corpus are reportedly derived from de-differentiation of chief cells. However, the cellular origin of metaplasia and cancer remained uncertain. Therefore, we investigated whether pepsinogen C (PGC) transcript–expressing cells represent the cellular origin of metaplasia and cancer using a novel Pgc -specific CreERT2 recombinase mouse model. Methods We generated a Pgc - mCherry-IRES-CreERT2 ( Pgc-CreERT2 ) knock-in mouse model. Pgc-CreERT2/ + and Rosa-EYFP mice were crossed to generate Pgc-CreERT2/Rosa-EYFP (Pgc-CreERT2/YFP) mice. Gastric tissues were collected, followed by lineage-tracing experiments and histologic and immunofluorescence staining. We further established Pgc-CreERT2 ; Kras G12D/+ mice and investigated whether PGC transcript–expressing cells are responsible for the precancerous state in gastric glands. To investigate cancer development from PGC transcript–expressing cells with activated Kras, inactivated Apc, and Trp53 signaling pathways, we crossed Pgc-CreERT2/ + mice with conditional Kras G12D , Apc flox , Trp53 flox mice. Results Expectedly, mCherry mainly labeled chief cells in the Pgc-CreERT2 mice. However, mCherry was also detected throughout the neck cell and isthmal stem/progenitor regions, albeit at lower levels. In the Pgc-CreERT2 ; Kras G12D/+ mice, PGC transcript–expressing cells with Kras G12D/+ mutation presented pseudopyloric metaplasia. The early induction of proliferation at the isthmus may reflect the ability of isthmal progenitors to react rapidly to Pgc -driven Kras G12D/+ oncogenic mutation. Furthermore, Pgc-CreERT2 ; Kras G12D/+ ;Apc flox/flox mice presented intramucosal dysplasia/carcinoma and Pgc-CreERT2 ; Kras G12D/+ ;Apc flox/flox ;Trp53 flox/flox mice presented invasive and metastatic gastric carcinoma. Conclusions The Pgc-CreERT2 knock-in mouse is an invaluable tool to study the effects of successive oncogenic activation in the mouse corpus. Time-course observations can be made regarding the responses of isthmal and chief cells to oncogenic insults. We can observe stomach-specific tumorigenesis from the beginning to metastatic development.