Method for searching and screening for target of anti-cancer agent using non-human animal model having NOG established cancer cell line transplanted therein

#This is the U.S. National Stage of International Application No. PCT/JP2010/073266, filed Dec. 24, 2010, which in turn claims the benefit of Japanese Patent Application No. 2009-295426, filed Dec. 25, 2009.

#The present invention relates to non-human animal models of cancer pathology, which mimic the hierarchical organization of human cancer tissues with cancer stem cells at the top of the hierarchy, reproduce the cancer progression process, and enable assessment of their biological properties. The present invention also relates to methods of screening for anti-cancer agents and methods for assessing the pharmacological effects of test substances, which use the non-human animal model or an in vitro culture system of an NOG-established cancer cell line, which is established by transplanting human tumor tissues into severely-immunodeficient NOD/SCID/gamma(c)(null) (NOG) mice.

#Human tumor cells show various tissue structures, and such tissues are known to have a hierarchical organization with cancer stem cells at the top of the hierarchy (Non-patent Document 1). For example, it is known that colon cancer is roughly subdivided into two layers: first an area with differentiated colon epithelium-like cells having a glandular structure, and second an invasive area with cells having a tendency to differentiate into mesenchymal cells (Non-patent Documents 2 and 3). Such findings were obtained based on knowledge accumulated through a vast amount of morphological observations of human colon cancer tissues. However, animal models that mimic the hierarchical organization of cancer tissues are rare. Thus, little is understood about the process leading to the formation of the hierarchical organization of cancer tissues and the involvement of cancer stem cells in this process.

#FIG. 1 is a photograph showing an epithelium-like proliferation area in colon cancer. The glandular structure is observed, and E-cadherin is expressed on the whole cell surface.

#FIG. 2 shows photographs depicting an epithelium-like proliferation under in vitro culture conditions. Left panel: three-dimensional suspension culture; right panel: three-dimensional Matrigel culture. Formation of epithelium-like glandular structures is observed with the three-dimensional Matrigel culture. NOG-established colon cancer cell line was used.

#FIG. 3 shows photographs depicting an invasive area in colon cancer. E-cadherin expression has disappeared where each invasive area comes into contact with tumor stroma.

#The present invention relates to non-human animal models of cancer pathology, which can be effectively used for developing pharmaceutical agents for treating or preventing human cancer, and cell culture systems that exhibit in vitro cell morphology more similar to that in a cancer pathology. Specifically, the present invention relates to non-human animal models obtained by transplanting an NOG-established cancer cell line (established by transplanting human cancer tissues into severely-immunodeficient NOD/SCID/gamma(c)(null) (NOG) mice) into non-human animals of the same or a different species, as well as in vitro culture systems of the NOG-established cancer cell lines.

#The non-human animal models of the present invention may mimic the hierarchical organization of cancer tissues, cancer progression process, and biological properties thereof, which are unique to pathology of a human cancer. In the present invention, types of target cancers are not particularly limited, but preferably include, for example, colon cancer, stomach cancer, lung cancer, breast cancer, and pancreatic cancer.

#Herein, the “hierarchical organization of cancer tissues, which is unique to human cancer pathology” includes a two-layer structure having an area with a glandular structure consisting of cells with epithelial-like differentiation and an invasive area with cells having a tendency to differentiate into mesenchymal cells.