Imaging innate immune responses at tumour initiation: new insights from fish and flies.

Recent imaging studies in genetically tractable and translucent zebrafish and Drosophila melanogaster models have opened a window on the earliest stages of tumorigenesis, when pre-neoplastic cells first arise in tissues before they progress into full-blown cancers. Innate immune cells often find these cells soon after they develop, but this efficient surveillance is not always good for the host because although immune cells have phagocytic capacity, they can also nurture the growing clones of pre-neoplastic cells. We describe these newly observed early interactions between immune cells and cancer cells and speculate on their potential clinical implications.