Phosphatidylinositol 3-kinase, class 2 beta (PI3KC2β) isoform contributes to neuroblastoma tumorigenesis

• PI3KC2β contributes to neuroblastoma tumorigenesis.
• MYCN-amplified vs non-MYCN amplified tumor cells demonstrate a differential dependence on PI3KC2β for their tumorigenic activity.
• The ITSN1–PI3KC2β pathway regulates the AKT but not the ERK–MAPK pathway activation by growth factor.

Phosphatidylinositol 3-kinases (PI3Ks) play important roles in human tumorigenesis. Activation of the PI3K target AKT is frequent in neuroblastoma (NB) and correlates with poor prognosis. PI3K pan-inhibitors reduce NB tumor formation but present severe toxicity, which limits their therapeutic potential. Therefore, defining the importance of specific PI3K isoforms may aid in developing more effective therapeutic strategies. We previously demonstrated that PI3K Class IIβ (PI3KC2β) and its regulator intersectin 1 (ITSN1) are highly expressed in primary NB tumors and cell lines. Silencing ITSN1 dramatically reduced the tumorigenic potential of NB cells. Interestingly, overexpression of PI3KC2β rescued the anchorage-independent growth of ITSN1-silenced cells suggesting that PI3KC2β mediates ITSN1's function in NB cells. To address the importance of PI3KC2β in NBs, we generated PI3KC2β-silenced lines and examined their biologic activity. Herein, we demonstrate that PI3KC2β-silencing inhibits early stages of NB tumorigenic growth. We also show that loss of endogenous PI3KC2β or ITSN1 reduces AKT activation but does not impact ERK–MAPK activation. These data reveal a novel role for PI3KC2β in human NB tumorigenesis.