title: Characterization and propagation of tumor initiating cells derived from colorectal liver metastases: trials, tribulations and a cautionary note.
abstract: Tumor initiating cells (TIC) are increasingly being put forward as a potential target for intervention within colorectal cancer. Whilst characterisation and outgrowth of these cells has been extensively undertaken in primary colorectal cancers, few data are available describing characteristics within the metastatic setting. Tissue was obtained from patients undergoing surgical resection for colorectal liver metastases, and processed into single cell suspension for assessment. Tumor initiating cells from liver metastases were characterised using combinations of EPCAM, Aldehyde dehydrogenase activity, CD133 and CD26. CD133 expression was significantly lower in patients who had received chemotherapy, but this was accounted for by a decrease observed in the male patient cohort only. ALDHhigh populations were rare (0.4 and 0.3% for EPCAM+/ALDHhigh/CD133- and EPCAM+/ALDHhigh/CD133+ populations respectively) and below the limits of detection in 28% of samples. Spheroid outgrowth of metastatic tumor cells across all samples could not be readily achieved using standard spheroid-formation techniques, thus requiring further method validation to reliably propagate cells from the majority of tissues. Spheroid formation was not enhanced using additional growth factors or fibroblast co-culture, but once cells were passaged through NOD-SCID mice, spheroid formation was observed in 82% samples, accompanied by a significant increase in CD26. Order of spheroid forming ability was ALDHhigh>CD133>CD26. Samples sorted by these markers each had the ability to reform ALDHhigh, CD133 and CD26 positive populations to a similar extent, suggestive of a high degree of plasticity for each population. Ex vivo TIC models are increasingly being utilised to assess efficacy of therapeutic interventions. It is therefore essential that such investigations use well-characterised models that are able to sustain TIC populations across a large patient cohort in order that the inherent heterogeneity observed in cancer populations is maintained.
authors: University of Leicester, Leicester, United Kingdom.
authors: Mark I
authors: MI
authors: James
authors: University of Leicester, Leicester, United Kingdom.
authors: Lynne M
authors: LM
authors: Howells
authors: University of Leicester, Leicester, United Kingdom.
authors: Ankur
authors: A
authors: Karmokar
authors: University of Leicester, Leicester, United Kingdom.
authors: Jennifer A
authors: JA
authors: Higgins
authors: University of Leicester, Leicester, United Kingdom.
authors: Peter
authors: P
authors: Greaves
authors: University of Leicester, Leicester, United Kingdom.
authors: Hong
authors: H
authors: Cai
authors: University Hospitals of Leicester, Leicester, United Kingdom.
authors: Ashley
authors: A
authors: Dennison
authors: University Hospitals of Leicester, Leicester, United Kingdom.
authors: Matthew
authors: M
authors: Metcalfe
authors: University Hospitals of Leicester, Leicester, United Kingdom.
authors: Giuseppe
authors: G
authors: Garcea
authors: University Hospitals of Leicester, Leicester, United Kingdom.
authors: David M
authors: DM
authors: Lloyd
authors: University Hospitals of Wales, Cardiff, United Kingdom.
authors: David P
authors: DP
authors: Berry
authors: University of Leicester, Leicester, United Kingdom.
authors: William P
authors: WP
authors: Steward
authors: University of Leicester, Leicester, United Kingdom.
authors: Karen
authors: K
authors: Brown
mesh_terms: D000071916:AC133 Antigen; D000368:Aged; D000369:Aged, 80 and over; D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D000951:Antigens, Neoplasm / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D018920:Coculture Techniques; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005434:Flow Cytometry; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000556:secondary; D008297:Male; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008875:Middle Aged; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D018874:Spheroids, Cellular / Q000378:metabolism / Q000473:pathology; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D000444:Aldehyde Dehydrogenase; D018819:Dipeptidyl Peptidase 4