Table 1.

Comparison of orthotopic transplantation methods of stomach tumor

Method	The engraftment volume	Application	Advantage	Limitation
Cell injection	<  50 μl	Tumor proliferation and metastasis profile of gastric cancer cell lines. Functional validation of cancer driver genes/pathways by transplanting engineered cell lines. Efficacy test of anti-tumor or anti-metastatic therapeutics.	Minimal organ damage. The fastest transplantation method. High reproducibility.	Possible to inject only single-cell suspension.
Tissue implantation by suture on the exposed sub-serosa	Tissue less than 3 mm in diameter	Tumor proliferation and metastasis profile of gastric cancer cell lines and patient-derived tumors.	Possible to transplant patient-derived tissue. Relatively easy procedure as a tissue implantation technic.	Engraft only hard tissue fragment. Tumor exposed to the peripheral cavity. Increase the adhesion to the nearby organs. Difficult to control the tumor heterogeneity.
Tissue implantation in sub-serosa with glue	Tissue less than 1 mm in diameter	Tumor proliferation and metastasis profile of gastric cancer cell lines and patient-derived tumors.	Possible to transplant patient-derived tissue.	Engraft only hard 1 mm3 tissue fragment. Difficult to control the tumor heterogeneity.
Completely-closed tissue implantation method	<  20 μl or Tissue less than 2 mm in diameter	Tumor proliferation and metastasis profile of gastric cancer cell lines and patient-derived tumors. Functional validation of cancer driver genes by using patient-derived organoids system. Possible to test anti-tumor or anti-metastatic therapeutics.	No limit to transplant any types of tissues, including organoids and homogeneous tissue suspension. Tissue insertion completely into the stomach wall.	Technical challenges.