Chromogranin A and its fragments as regulators of small intestinal neuroendocrine neoplasm proliferation.

Abstract

INTRODUCTION:

Chromogranin A is a neuroendocrine secretory product and its loss is a feature of malignant NEN de-differentiation. We hypothesized that chromogranin A fragments were differentially expressed during NEN metastasis and played a role in the regulation of NEN proliferation.

METHODS:

Chromogranin A mRNA (PCR) and protein (ELISA/western blot) were studied in 10 normal human mucosa, 5 enterochromaffin cell preparations, 26 small intestinal NEN primaries and 9 liver metastases. Cell viability (WST-1 assay), proliferation (bromodeoxyuridine ELISA) and expression of AKT/AKT-P (CASE ELISA/western blot) in response to chromogranin A silencing, inhibition of prohormone convertase and mTOR inhibition (RAD001/AKT antisense) as well as different chromogranin A fragments were examined in 4 SI-NEN cell lines.

RESULTS:

Chromogranin A mRNA and protein levels were increased (37-340 fold, p<0.0001) in small intestinal NENs compared to normal enterochromaffin cells. Western blot identified chromogranin A-associated processing bands including vasostatin in small intestinal NENs as well as up-regulated expression of prohormone convertase in metastases. Proliferation in small intestinal NEN cell lines was decreased by silencing chromogranin A as well as by inhibition of prohormone convertase (p<0.05). This inhibition also decreased secretion of chromogranin A (p<0.05) and 5-HT (p<0.05) as well as expression of vasostatin. Metastatic small intestinal NEN cell lines were stimulated (50-80%, p<0.05) and AKT phosphorylated (Ser473: p<0.05) by vasostatin I, which was completely reversed by RAD001 (p<0.01) and AKT antisense (p<0.05) while chromostatin inhibited proliferation (~50%, p<0.05).

CONCLUSION:

Chromogranin A was differentially regulated in primary and metastatic small intestinal NENs and cell lines. Chromogranin A fragments regulated metastatic small intestinal NEN proliferation via the AKT pathway indicating that CgA plays a far more complex role in the biology of these tumors than previously considered.

• Authors: Francesco Giovinazzo, Simon Schimmack, Bernhard Svejda, Daniele Alaimo, Roswitha Pfragner, Irvin Modlin, Mark Kidd
• Journal: PloS one (PLoS One) Vol. 8 Issue 11 Pg. e81111 ( 2013) ISSN: 1932-6203 [Electronic] United States
• PMID: 24260544 (Publication Type: Journal Article)

Chemical References

• Calreticulin
• Chromogranin A
• Peptide Fragments
• RNA, Messenger
• RNA, Small Interfering
• vasostatin
• Everolimus
• MTOR protein, human
• Proto-Oncogene Proteins c-akt
• TOR Serine-Threonine Kinases
• Proprotein Convertases
• Sirolimus

Topics

• Calreticulin (metabolism, pharmacology)
• Cell Line, Tumor
• Cell Proliferation
• Cell Survival
• Chromogranin A (antagonists & inhibitors, genetics, metabolism)
• Everolimus
• Gene Expression Regulation, Neoplastic
• Humans
• Intestinal Neoplasms (genetics, metabolism, pathology)
• Liver Neoplasms (genetics, metabolism, secondary)
• Neuroendocrine Tumors (genetics, metabolism, secondary)
• Peptide Fragments (metabolism, pharmacology)
• Phosphorylation
• Proprotein Convertases (antagonists & inhibitors, genetics, metabolism)
• Proto-Oncogene Proteins c-akt (genetics, metabolism)
• RNA, Messenger (genetics, metabolism)
• RNA, Small Interfering (genetics, metabolism)
• Signal Transduction
• Sirolimus (analogs & derivatives, pharmacology)
• TOR Serine-Threonine Kinases (antagonists & inhibitors, genetics, metabolism)