For example, anywhere between 8 and 63% of T-cell acute lymphoblastic leukemia (T-ALL) patients have mutated or lost PTEN tumor suppressor gene [2–5], suggesting the importance of the PI3K pathway in T-cell leukemia and providing the rationale for the development of PI3K-targeted therapies in T-ALL. The gene discussed is PIK3CD; the disease is T-cell acute lymphoblastic leukemia.