Fig. 3 |. Establishment of an endoluminal rectal cancer assay in mice.

a, Cartoon of the implantation process and an endoscopic view of the first rectal tumoroid (RC-MSK-001) implanted in a NSG mouse; mouse at 4, 8, and 12 weeks (top panels). H&E of the engrafted tumoroid biopsied at 4 weeks via endoscopic channel (bottom panels) demonstrates high nuclear/cytoplasmic ratio, poor differentiation, and neoplastic glands (arrowhead). Adjacent normal mouse colonic epithelium and stroma is seen. Scale bars from low to high magnification are as follows: 200 μm, 100 μm, 50 μm. b, H&E, axial view of the rectal tumor within the NSG mouse rectum with adjacent serial sections (upper panels). Inset demonstrates intramucosal adenocarcinoma with atypical neoplastic cells, poorly differentiated tumor cells, and high nuclear to cytoplasmic ratio. IF (lower panels): DAPI (blue), hEpCAM (green), mEpCAM (red). Scale bars from low to high magnification: 2,000 μm, 500 μm, 200 μm, 50 μm. c, NSG mouse rectum (gross rectum with tumor, white dashed circle) and H&E shows evidence of a moderately differentiated tumor engrafted from RC-MSK-001 tumoroids with invasion into the muscularis (inset, arrowhead). Scale bars: 500 μm; inset, 50 μm. d, Gross lung metastasis (white dashed circle) from the same mouse presented in c engrafted endoluminally with RC-MSK-001 tumoroids. Corresponding H&Es demonstrate poorly differentiated architecture of the metastasis. IF serial section demonstrates engraftment of the human tumoroids: DAPI (blue), hEpCAM (green), mEpCAM (red). Lower panel shows axial thoracic CT imaging of the patient from which the tumoroid was derived, demonstrating lung metastases (orange arrows indicate two of multiple lung metastases). Scale bars: 500 μm; H&E and IF insets, 50 μm. Images are representative of 5 tumoroid engraftments into mouse rectum.