Moreover, breast cancer cell line spheroids showed dependency on PIK3CA according to their PIK3CA status, with mutant MCF7 and T47D cells (harbouring E575K and H1047R PIK3CA mutations, respectively) being sensitive to PIK3CA silencing, and MDA‐MB‐231 cells (wild type) showing no change in viability after PIK3CA silencing. This evidence concerns the gene PIK3CA and breast cancer.