Makoto Monnai

Establishment of a humanized model of liver using NOD/Shi-scid IL2Rgnull mice

Severely immunodeficient NOD/Shi-scid IL2Rg(null) (NOG) mice are used as recipients for human tissue transplantation, which produces chimeric mice with various types of human tissue. NOG mice expressing transgenic urokinase-type plasminogen activator in the liver (uPA-NOG) were produced. Human hepatocytes injected into uPA-NOG mice repopulated the recipient livers with human cells. The uPA-NOG model has several advantages over previously produced chimeric mouse models of human liver: (1) the severely immunodeficient NOG background enables higher xenogeneic cell engraftment; (2) the absence of neonatal lethality enables mating of homozygotes, which increased the efficacy of homozygote production; and (3) donor xenogeneic human hepatocytes could be readily transplanted into young uPA-NOG mice, which provide easier surgical manipulation and improved recipient survival.

Innate Response to Human Cancer Cells with or without IL-2 Receptor Common γ-Chain Function in NOD Background Mice Lacking Adaptive Immunity

Immunodeficient hosts exhibit high acceptance of xenogeneic or neoplastic cells mainly due to lack of adaptive immunity, although it still remains to be elucidated how innate response affects the engraftment. IL-2R common γ-chain (IL-2Rγc) signaling is required for development of NK cells and a subset of dendritic cells producing IFN-γ. To better understand innate response in the absence of adaptive immunity, we examined amounts of metastatic foci in the livers after intrasplenic transfer of human colon cancer HCT116 cells into NOD/SCID versus NOD/SCID/IL-2Rγcnull (NOG) hosts. The intravital microscopic imaging of livers in the hosts depleted of NK cells and/or macrophages revealed that IL-2Rγc function critically contributes to elimination of cancer cells without the need for NK cells and macrophages. In the absence of IL-2Rγc, macrophages play a role in the defense against tumors despite the NOD Sirpa allele, which allows human CD47 to bind to the encoded signal regulatory protein α to inhibit macrophage phagocytosis of human cells. Analogous experiments using human pancreas cancer MIA PaCa-2 cells provided findings roughly similar to those from the experiments using HCT116 cells except for lack of suppression of metastases by macrophages in NOG hosts. Administration of mouse IFN-γ to NOG hosts appeared to partially compensate lack of IL-2Rγc–dependent elimination of transferred HCT116 cells. These results provide insights into the nature of innate response in the absence of adaptive immunity, aiding in developing tumor xenograft models in experimental oncology.

Abstract 2366: Reduced ecto-5′-nucleotidase CD73 expression and altered purine nucleotide metabolism in colorectal cancer cells robustly causing liver metastases

Liver metastases are frequently inoperative and severely impact the prognoses of patients with cancers. Colorectal cancers as well as pancreatic cancers most commonly metastasize to the liver, although there are some patients with colorectal cancers presenting liver metastases operative contrary to the cases of pancreatic cancers. Through liver metastasis models using NOD/SCID/IL-2Rγc null (NOG) mice, we have previously established and examined a highly liver-metastatic human pancreatic cancer cell subline, which was derived from the poorly liver-metastatic parental line, identifying a key molecular regulator of liver metastasis. In the present study, we established a highly liver-metastatic human colorectal cancer cell subline SW48LM2 through the serial intrasplenic transfer of cells derived from poor but visible hepatic tumor foci formed by parental SW48 cells transferred to NOG mice. The growth both under monolayer-culture conditions and during formation of the subcutaneous tumors was similar between the two cell lines, although there were morphological differences in the in vitro spheroid formation. Of 41 molecules reportedly associated positively or negatively with tumor progression, four were overexpressed and four were underexpressed in SW48LM2 cells. Most strikingly, this liver-metastatic cell subline exhibited strongly reduced expression of the ecto-5′ -nucleotidase CD73 as well as altered metabolism of purine nucleotides. Contrary to previous studies showing a positive correlation between CD73 expression and metastatic cancer phenotypes, reduced CD73 expression on tumor cells may contribute to the potential of liver metastases. The present study highlights the need for interpretative caution when investigating metastasis-associated molecules for the diagnostic and therapeutic applications, providing insights into the mechanisms of liver metastases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2366.