Differential Protein Expression in Small Intestinal Neuroendocrine Tumors and Liver Metastases

Abstract

Objectives Small intestinal neuroendocrine tumors (SI-NETs) are often detected after they have become metastatic. Using a novel protein array, we identified pathways important in SI-NET metastasis development in surgically resected patients. Methods Paired primary tumors and liver metastases from 25 patients undergoing surgical resection for metastatic SI-NETs were harvested. Extracted proteins were separated by SDS gel, and multiplex immunoblots were performed with 136 antibodies. Significant Analysis of Microarray was used to select for differentially expressed proteins. A tissue microarray was constructed from 27 archived specimens and stained by immunohistochemistry. Results Comparing primary SI-NETs to matched normal small bowel mucosa, 9 proteins were upregulated and Cyclin E was down-regulated. SI-NET liver metastases demonstrated up-regulation of P-ERK and p27 but down-regulation of CDK2 and CDC25B. When comparing primary SI-NET with their paired liver metastases, cyclin E demonstrated a significant up-regulation in the liver metastasis. Tissue microarray demonstrated higher p38 expression and lower Cdc 25b expression in SI-NETs vs liver metastases and confirmed higher expression of p27 in liver metastases vs normal liver. Conclusions Few studies have compared protein expression in paired primary and metastatic SI-NETs. Our findings reveal changes in a limited number of proteins, suggesting these may be targets for therapy.

Genetic heterogeneity of primary lesion and metastasis in small intestine neuroendocrine tumors.

“…In-silico pathway analysis revelead that cell cycle pathways were found to be significantly mutated in the primary lesion, whereas genes regulating adherence junction stability and disassembly were identified in the metastases group. This correlates to protein expression data of a study of Kim et al, where proteins involved in cell cycle and proliferation were found to be differentially expressed in primary lesions and metastasis 21 . However, functional data of metastasis development of SI-NET are still due and further studies are warranted.…”

High-throughput proteomics: a methodological mini-review

“…It remains a time-consuming and subjective process and produces a qualitative or semiquantitative assessment of protein expression because of the nonspecific stain or background noise. As technology advanced and high-throughput demand increased over the last decade, the TMA gradually began to be widely used in both research and clinical fields 36 , 37 . TMA contains many small representative tissue cores of formalin-fixed paraffin-embedded (FFPE) or frozen blocks from hundreds of different cases assembled in an array fashion on a single histologic slide, and therefore allows a large-scale antibody-based molecular analysis of multiple samples at the same time 37 .…”