Stathmin in pancreatic neuroendocrine neoplasms: a marker of proliferation and PI3K signaling

Tumour Biol. 2015 Jan;36(1):399-408. doi: 10.1007/s13277-014-2629-y. Epub 2014 Sep 30.

Abstract

Chromosome 1p35-36, which encodes tumor suppressors and mitotic checkpoint control genes, is commonly altered in human malignancies. One gene at this locus, stathmin 1 (STMN1), is involved in cell cycle progression and metastasis. We hypothesized that increased STMN1 expression may play a role in pancreatic neuroendocrine neoplasm (pNEN) malignancy. We investigated stathmin copy number variation, mRNA, and protein expression using PCR-Taqman Copy Number Assays, Q-PCR, Western blot, and immunohistochemistry. A mechanistic role for stathmin in proliferation was assessed in the BON cell line under growth-restrictive conditions and siRNA silencing. Furthermore, its role in PI3K signaling pathway activation was evaluated using pharmacological inhibitors. mRNA (p = 0.0001) and protein (p < 0.05) were overexpressed in pNENs. Expression was associated with pNEN tumor extension (p < 0.05), size (p < 0.01), and Ki67 expression (p < 0.01). Serum depletion decreased Ki67 expression (p < 0.01) as well as Ser38 phosphorylation (p < 0.05) in BON cells. STMN1 knockdown (siRNA) decreased proliferation (p < 0.05), and PI3K inhibitors directly inhibited proliferation via stathmin inactivation (dephosphorylation p < 0.01). We identified that stathmin was overexpressed and associated with pathological parameters in pancreatic NENs. We postulate that STMN1 overexpression and phosphorylation result in a loss of cell cycle mitotic checkpoint control and may render tumors amenable to PI3K inhibitory therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Cell Proliferation*
  • DNA Copy Number Variations
  • Gene Expression
  • Humans
  • Imidazoles / pharmacology
  • Liver Neoplasms / metabolism*
  • Liver Neoplasms / secondary
  • Neuroendocrine Tumors / metabolism*
  • Neuroendocrine Tumors / secondary
  • Pancreas / metabolism
  • Pancreas / pathology
  • Pancreatic Neoplasms / metabolism*
  • Pancreatic Neoplasms / pathology
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Quinolines / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Signal Transduction
  • Stathmin / metabolism*

Substances

  • Imidazoles
  • Phosphoinositide-3 Kinase Inhibitors
  • Quinolines
  • RNA, Messenger
  • STMN1 protein, human
  • Stathmin
  • dactolisib