Inhibitors against the p110δ isoform of PI3K have shown remarkable therapeutic efficacy in some human leukaemias1,2. Since p110δ is primarily expressed in leukocytes3, drugs against p110δ have not been considered for the treatment of solid tumours4. We report here that p110δ inactivation in mice protects against a broad range of cancers, including non-haematological solid tumours. We demonstrate that p110δ inactivation in regulatory T cells (Treg) unleashes CD8+ cytotoxic T cells and induces tumour regression. Thus, p110δ inhibitors can break tumour-induced immune tolerance and should be considered for wider use in oncology.

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Although not the prime focus of the InSight mission, the near-surface geology and physical properties investigations provide critical information for both placing the instruments (seismometer and heat flow probe with mole) on the surface and for understanding the The InSight Mission to Mars II Edited by William B.