mRNA profiling of a well-differentiated G1 pancreatic NET correlates with immunohistochemistry profile: a case report

Abstract

Background Neuroendocrine neoplasms (NENs) are a complex group of tumours that occur in many organs. Routinely used IHC markers for NEN diagnosis include CgA, synaptophysin, Ki67 and CD56. These have limitations including lack of correlation to clinical outcomes and their presence in non-tumour tissue. Identification of additional markers and more quantitative analyses of tumour tissue has the potential to contribute to improved clinical outcomes. We used qRT-PCR to profile the expression levels of a panel of markers in tumour and matched non-tumour tissue from a patient with a G1 pancreatic neuroendocrine tumour. Differences in mRNA levels between tumour and non-tumour tissue were compared with IHC analyses of the same sample. Case presentation An elderly man presented with lower abdominal pain for 6 months. Histological analysis identified a low grade, well differentiated pancreatic endocrine neoplasm. Twenty-seven tumour markers for neuroendocrine status, proliferation, stem cell phenotype, angiogenesis, epithelial to mesenchymal transition, cell adhesion, differentiation and tumour suppression were selected from previous studies and mRNA levels of these markers were measured in tumour and adjacent non-tumour tissue sample using qRT-PCR. IHC was carried out on the same tissue to detect the corresponding marker proteins. Of the markers analysed, seven showed higher mRNA levels in tumour relative to non-tumour tissue while thirteen had lower expression in tumour relative to non-tumour tissue. Substantial differences in mRNA levels were a gain of CgA, CD56, β-catenin, CK20, PDX1 and p53 and loss of Ki67, PCAD, CK7, CD31, MENA, ECAD, EPCAM, CDX2 and CK6. Comparison of qRT-PCR data with IHC showed correlation between fifteen markers. Conclusion Our study is unique as it included matched controls that provided a comparative assessment for tumour tissue analysis, whereas many previous studies report tumour data only. Additionally, we utilised qRT-PCR, a relatively quantitative diagnostic tool for differential marker profiling, having the advantage of being reproducible, fast, cheap and accurate. qRT-PCR has the potential to improve the defining of tumour phenotypes and, in combination with IHC may have clinical utility towards improving tumour stratification or distinguishing tumour grades. The results need to be validated with different grades of NENs and related to clinical outcomes.

EMT Molecular Signatures of Pancreatic Neuroendocrine Neoplasms

“…mRNA levels of four markers, synaptophysin (G2), CD44 (G2), DAXX (G1, G2) and CK7 (G3) did not correlate with the protein expression. These data are consistent with our previous study comparing mRNA and protein markers in a G1 pancreatic NET sample which showed that CD44 and DAXX mRNA and protein levels in G1 did not correlate [ 24 ]. Poor correlation with some CD antigens like CD24 and CD44 has also been previously reported in prostrate cell types [ 28 ].…”

“…Twenty-seven markers that correlated with a range of tumour-associated characteristics that had been previously tested in a pancreatic tumour case study [ 24 ] were selected ( Table 4 ). These markers included indicators of a neuroendocrine origin, a category of markers associated with EMT including proliferation, stem cell phenotype, cell adhesion, differentiation and tumour suppression, a multifunctional category that included EMT-associated markers and a category of vascular markers indicating angiogenesis.…”

“…In a previous study, to improve the definition of tumour phenotypes, we tested a panel of 23 tumour-associated markers to profile matched tumour tissue relative to non-tumour tissue from a patient with a G1 pancreatic neuroendocrine tumour [ 24 ]. We utilised qRT-PCR, a quantitative diagnostic tool for differential marker profiling, that has the potential, and when used in combination with IHC has potential clinical utility, towards improving tumour stratification.…”