To further assess the functional importance of the PI3K p110δ in both macrophages and cancer cells, we evaluated the impact of p110δ inhibition on tumour growth in two specific combinations of host mice and tumour cells: we used tumour cells expressing p110δ inoculated into mice with defective macrophages and tumour cells lacking p110δ growing up in mice with normal macrophages. The gene discussed is PIK3CD; the disease is cancer.