Impact of NAP1L1 silencing of tumor growth in an orthotopic pNEN mouse model. After having established stable NAP1L1 knockdown BON cells (confirmation of shRNA internalization by fluorescence microscopy (A) and thereafter puromycin-selection), we injected 1.5 × 106 transfected cells in 100 μl PBS into the pancreas tail of nine Ns/J-mice by flank-laparotomy (CON = 4 mice, KD = 5 mice). Six weeks after pancreas injection, necroscopy identify large tumors with metastases in control injected mice (B), while KD-injected mice had smaller (C) (*p < 0.05) and lighter (D) (*p < 0.05) tumors that were all localized. KD tumors expressed less NAP1L1 than controls (E and G). Circulating chromogranin A (CgA) levels were also decreased in serum of KD mice (F) (*p < 0.05), and expression of this marker was lower in the liver metastases (G). Mean ± SEM.