title: Metastasis blood test by flow cytometry: in vivo cancer spheroids and the role of hypoxia.
abstract: Cancer hypoxia correlates with therapeutic resistance and metastasis, suggesting that hypoxic adaptation is a critical survival advantage for cancer stem cells (CSCs). Hypoxic metabolism, however, may be a disadvantage in aerobic circulation as the extremely low incidence of metastasis-compared to the high circulating tumor-cell numbers (CTCs)-appears to suggest. As rare metastatic CSCs still survive, we searched for a mechanism that protects them from oxygen in circulation. CSCs form multicellular spheroids in vitro from virtually all cancers tested. We asked, therefore, whether cancers also form spheroids in vivo and whether circulating spheroids play a role in metastasis. We used metabolic, apoptotic and hypoxia assays, we measured aerobic barriers and calculated hypoxia vs. spheroid-size correlations. We detected metabolic/oxidative stress in spheroids, we found correlation between stem cell presence and hypoxia and we showed that the size of hypoxic spheroids is compatible with circulation. To detect spheroids in patients, we worked out a new light-scatter flow cytometry blood test and assayed 67 metastatic and control cases. We found in vivo spheroids with positive stem cell markers in cancer blood and they showed exclusive correlation with metastasis. In conclusion, our data suggest that metastatic success depends on CSC-association with in vivo spheroids. We propose that the mechanism involves a portable "micro-niche" in spheroids that may support CSC-survival/adaptation in circulation. The new assay may establish a potential early marker of metastatic progression.
authors.affiliation: Department of Integrative Physiology and Pathobiology, Tufts University, Boston, MA 02111, USA.
authors.forename: Viktoria
authors.initials: V
authors.lastname: Denes
authors.forename: Monika
authors.initials: M
authors.lastname: Lakk
authors.forename: Andrew
authors.initials: A
authors.lastname: Makarovskiy
authors.forename: Pal
authors.initials: P
authors.lastname: Jakso
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Szappanos
authors.forename: Laszlo
authors.initials: L
authors.lastname: Graf
authors.forename: Laszlo
authors.initials: L
authors.lastname: Mandel
authors.forename: Istvan
authors.initials: I
authors.lastname: Karadi
authors.forename: Peter
authors.initials: P
authors.lastname: Geck
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002277:Carcinoma / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D009369:Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology*; D009360:Neoplastic Cells, Circulating / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000378:metabolism; D018874:Spheroids, Cellular; D013312:Stress, Physiological; D014407:Tumor Cells, Cultured
chemical_list: D015415:Biomarkers
keywords: CSC; blood-test; flow cytometry; hypoxia; metastasis; spheroid; tumorsphere