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Issue 173: Via experiments and mathematical modelling, we investigated a "winner" clone that inhibits a "loser" clone derived from the same tumour. In this image, the two curves depict the distinctive three-phase frequency dynamics of the winner (blue) and loser (red) in co-culture. In the first phase, the two clones barely interact, and the loser increases in frequency due to its higher intrinsic growth rate. In phase two, paracrine factors suppress the loser while boosting the winner's growth. Finally, both clones die off as toxins accumulate and resources are exhausted. Overall, the interactions are effectively equivalent to those of a parasite and its host, such that the loser both suffers from the winner's presence and enhances the winner’s fitness. The distinctive shape of the frequency curves is appropriately reminiscent of a parasitic tick, such as shown here overlaid on a microscope photo of the competing tumour cells. Read more here.