Characterization of Cancer Stem Cells in Colon Adenocarcinoma Metastasis to the Liver

BACKGROUND: Fifty percent of colorectal cancer (CRC) patients develop liver metastasis. This study identified and characterized cancer stem cells (CSCs) within colon adenocarcinoma metastasis to the liver (CAML). METHODS: 3,3-Diaminobenzidine immunohistochemical (IHC) staining was performed on nine CAML samples for embryonic stem cell (ESC) markers OCT4, SOX2, NANOG, c-Myc, and KLF4. Immunofluorescence (IF) IHC staining was performed to investigate coexpression of two markers. NanoString mRNA expression analysis and colorimetric in situ hybridization (CISH) were performed on four snap-frozen CAML tissue samples for transcript expression of these ESC markers. Cells stained positively and negatively for each marker by IHC and CISH staining were counted and analyzed. RESULTS: 3,3-Diaminobenzidine IHC staining, and NanoString and CISH mRNA analyses demonstrated the expression of OCT4, SOX2, NANOG, c-Myc, and KLF4 within in all nine CAML samples, except for SOX2 which was below detectable levels on NanoString mRNA analysis. IF IHC staining showed the presence of a SOX2(+)/NANOG(+)/KLF4(+)/c-Myc(+)/OCT(−) CSC subpopulation within the tumor nests, and a SOX2(+)/NANOG(+)/KLF4(+)/c-Myc(+)/OCT4(−) CSC subpopulation and a SOX2(+)/NANOG(+)/KLF4(+)/c-Myc(+)/OCT4(+) CSC subpopulation within the peritumoral stroma. CONCLUSION: The novel finding of three CSC subpopulations within CAML provides insights into the biology of CRC.