SPARC and neuroblastoma: SPARC overexpression prior to irradiation decreased pAKT levels by 60–70% when compared to mock or empty vector-treated controls (Fig. 3B); PTEN levels were increased up to 3- to 4-fold in SPARC-overexpressed neuroblastoma cells when compared to mock or empty vector-treated cells (Fig. 3B) as determined by densitometry analysis.