  Tumor growth is often the result of the simultaneous development of two or
more cancer cell populations. Their interaction between them characterizes the
system evolution. To obtain information about these interactions we apply the
recently developed vector universality (VUN) formalism to various instances of
competition between tumor populations. The formalism allows us: (a) to quantify
the growth mechanisms of a HeLa cell colony, describing the phenotype switching
responsible for its fast expansion, (b) to reliably reconstruct the evolution
of the necrotic and viable fractions in both in vitro and in vivo tumors using
data for the time dependences of the total masses, and (c) to show how the
shedding of cells leading to subspheroid formation is beneficial to both the
spheroid and subspheroid populations, suggesting that shedding is a strong
positive influence on cancer dissemination.
