title: Temporal progression of metastasis in lung: cell survival, dormancy, and location dependence of metastatic inefficiency.
abstract: Cancer metastasis is an inefficient process. The steps in metastasis responsible for this inefficiency and how metastatic inefficiency can vary in different locations within an organ remain poorly understood. B16F10 cells were injected to target mouse lung, and at sequential times thereafter we quantified in lung the time course of: (a) overall cell survival and metastatic development; and (b) local cell survival and growth with respect to the lung surface and specific interior structures. We found high rates of initial survival of cells trapped in the lung circulation, extravasation into lung tissue, and subsequent survival of extravasated solitary cells (74% at day 3) before metastasis formation. However, at the time of initial replication of metastatic cells a major loss of cells occurred. Although only a small proportion of injected cells started to form metastases, most of these developed into macroscopic tumors. Solitary cells found at later times were dormant. Thus, overall metastatic inefficiency was largely due to postextravasation events affecting solitary cells. Regionally within the lung, cells and metastases were randomly distributed to day 4, but by day 10 preferential tumor growth was found along the lung surface and around arterial and venous vessels. Thus, trapping and early growth of injected cells was unaffected by location within the lung, whereas subsequent metastatic growth was enhanced in specific microenvironments. This study: (a) quantifies early temporal and spatial progression of metastasis in lung; (b) documents persistence of solitary dormant cells; and (c) shows that metastatic inefficiency depends on the initiation of growth in a subset of extravasated cells, whereas continued growth of metastases occurs preferentially in specific tissue environments.
authors.affiliation: Department of Medical Biophysics, University of Western Ontario, London, Canada.
authors.forename: M D
authors.initials: MD
authors.lastname: Cameron
authors.forename: E E
authors.initials: EE
authors.lastname: Schmidt
authors.forename: N
authors.initials: N
authors.lastname: Kerkvliet
authors.forename: K V
authors.initials: KV
authors.lastname: Nadkarni
authors.forename: V L
authors.initials: VL
authors.lastname: Morris
authors.forename: A C
authors.initials: AC
authors.lastname: Groom
authors.forename: A F
authors.initials: AF
authors.lastname: Chambers
authors.forename: I C
authors.initials: IC
authors.lastname: MacDonald
mesh_terms: D000818:Animals; D017209:Apoptosis; D002470:Cell Survival; D018450:Disease Progression; D005260:Female; D020287:In Situ Nick-End Labeling; D008175:Lung Neoplasms / Q000473:pathology*; D008545:Melanoma / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009362:Neoplasm Metastasis; D013997:Time Factors; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured