CCR1-mediated accumulation of myeloid cells in the liver microenvironment promoting mouse colon cancer metastasis

• Published in: Clinical & experimental metastasis 2014-12, Vol.31 (8), p.977-989
• Main Authors: Hirai, Hideyo, Fujishita, Teruaki, Kurimoto, Kazuki, Miyachi, Hitoshi, Kitano, Satsuki, Inamoto, Susumu, Itatani, Yoshiro, Saitou, Mitinori, Maekawa, Taira, Taketo, M. Mark
• Format: Article
• Language: English
• Subjects: Animals; Biomedical and Life Sciences; Biomedicine; Blotting, Western; Bone Marrow Cells - metabolism; Bone Marrow Cells - pathology; Cancer Research; Cell Cycle; Cell Movement; Colonic Neoplasms - genetics; Colonic Neoplasms - metabolism; Colonic Neoplasms - pathology; Disease Models, Animal; Flow Cytometry; Hematology; Humans; Immunoenzyme Techniques; In Situ Hybridization; Liver Neoplasms - genetics; Liver Neoplasms - metabolism; Liver Neoplasms - secondary; Matrix Metalloproteinase 2 - genetics; Matrix Metalloproteinase 2 - metabolism; Matrix Metalloproteinase 9 - genetics; Matrix Metalloproteinase 9 - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Myeloid Cells - metabolism; Myeloid Cells - pathology; Oncology; Real-Time Polymerase Chain Reaction; Receptors, CCR1 - physiology; Research Paper; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; Surgical Oncology; Tumor Cells, Cultured; Tumor Microenvironment
• ISSN: 0262-0898; 1573-7276
• DOI: 10.1007/s10585-014-9684-z

To understand colon cancer metastasis, we earlier analyzed a mouse model that developed liver metastasis of cancer cells disseminated from the spleen. We suggested that CCR1 + bone marrow (BM)-derived cells are recruited to the microenvironment of disseminated colon cancer cells, and produce metalloproteinases MMP9 and MMP2, helping metastatic colonization. In the present study, we have examined these myeloid cells expressing CCR1 and/or MMPs in detail. To this end, we have established bacterial artificial chromosome (BAC)-based transgenic mouse lines in which membrane-targeted Venus fluorescent protein (mVenus) was expressed under the control of Ccr1 gene promoter. Then, myeloid cells obtained from the BM and liver metastatic foci were analyzed by the combination of flow cytometry and cytology/immunohistochemistry, in situ RNA hybridization, or quantitative RT-PCR. We have found four distinct types of myeloid cells recruited to the metastatic foci; neutrophils, eosinophils, monocytes and fibrocytes. These cell types exhibited distinct expression patterns for CCR1, MMP2 and MMP9. Namely, neutrophils found in the early phase of cancer cell dissemination expressed CCR1 exclusively and MMP9 preferentially, whereas fibrocytes accumulated in later phase expressed MMP2 exclusively. Either genetic inactivation of Ccr1 or antibody-mediated neutrophil depletion reduced subsequent recruitment of fibrocytes. The recruitment of CCR1 + neutrophils in early phase of colon cancer dissemination appears to cause that of fibrocytes in late phase. These results implicate the key role of CCR1 in colon cancer metastasis in this mouse model, and explain why both MMP9 and MMP2 are essential as genetically demonstrated previously. The results also suggest relevant mechanisms in humans.