title: Solving the puzzle of metastasis: the evolution of cell migration in neoplasms.
abstract: BACKGROUND
  Metastasis represents one of the most clinically important transitions in neoplastic progression. The evolution of metastasis is a puzzle because a metastatic clone is at a disadvantage in competition for space and resources with non-metastatic clones in the primary tumor. Metastatic clones waste some of their reproductive potential on emigrating cells with little chance of establishing metastases. We suggest that resource heterogeneity within primary tumors selects for cell migration, and that cell emigration is a by-product of that selection.
  
  
  RESULTS
  We developed an agent-based model to simulate the evolution of neoplastic cell migration. We simulated the essential dynamics of neoangiogenesis and blood vessel occlusion that lead to resource heterogeneity in neoplasms. We observed the probability and speed of cell migration that evolves with changes in parameters that control the degree of spatial and temporal resource heterogeneity. Across a broad range of realistic parameter values, increasing degrees of spatial and temporal heterogeneity select for the evolution of increased cell migration and emigration.
  
  
  CONCLUSIONS
  We showed that variability in resources within a neoplasm (e.g. oxygen and nutrients provided by angiogenesis) is sufficient to select for cells with high motility. These cells are also more likely to emigrate from the tumor, which is the first step in metastasis and the key to the puzzle of metastasis. Thus, we have identified a novel potential solution to the puzzle of metastasis.
authors.affiliation: Genomics and Computational Biology Program, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.forename: Kathleen
authors.initials: K
authors.lastname: Sprouffske
authors.forename: Qihong
authors.initials: Q
authors.lastname: Huang
authors.forename: Carlo C
authors.initials: CC
authors.lastname: Maley
mesh_terms: D001808:Blood Vessels / Q000473:pathology; D002465:Cell Movement; D006801:Humans; D008962:Models, Theoretical; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000098:blood supply / Q000473:pathology*; D009389:Neovascularization, Pathologic