Alternative models of cancer stem cells: The stemness phenotype model, 10 years later

Figure 1 Clonal stochastic model and effect of treatment with sequential chemotherapy cycles (or steps) on tumor progression. According to the clonal stochastic model a complex heterogeneous tumor may contain at a certain time, different subpopulations growing in different microenviroments. Clonal proliferation of single primordial cancer cell originates the original subpopulation (S₁). During tumor grow random mutations (represented by red lightning bolts) originates all different subpopulations (S₁-S₆). M₁-M₆ represent different microenvironments. Since this model is unidirectional repeated cycles of chemotherapy with no gap can gradually deplete specific cell subpopulations, reducing the tumor size and eventually, if all cancer cells are eliminated, lead to a cure.