Therapy-induced rapid drug resistance driven by genome chaos and polyploid giant cancer cells.

Initially effective cancer drug treatments often lead to resistance with greater aggressiveness. Traditionally, this is attributed to preexisting mutation/epigenetic heterogeneity, which allow resistant populations to dominate through selection. The discovery of genome chaos-mediated rapid cellular macroevolution offers the new mechanism of drug resistance beyond pre-existing variants. To test the hypothesis that effective treatments can paradoxically induce rapid-resistance through genome reorganization, a rapid drug-resistance model is examined in real time. Phenotypic changes - including growth-death dynamics and shifts in cell types like Polyploid Giant Cancer Cells (PGCCs) - along with their genomitypes, were tracked under high and low drug dosages. Despite its low frequency, the transition from effective killing to treatment-induced resistance does occur. The underlying mechanisms include increased killing intensity that amplifies population heterogeneity, large initial population size, and intrinsic instability of the cellular populations. When all factors are considered together, the two-phased model of cancer evolution can often convert apparent outliers into observable outcomes, helping to account for the clinical results of treatment-induced resistance. This important finding requires timely validation, as it challenges current treatment strategies and suggests that cancer resistance may differ fundamentally from bacterial resistance. Treatment strategy must therefore be carefully reconsidered.