Nicole H. M. Senden

Neuronal differentiation is accompanied by NSP-C expression

Abstract Neuroendocrine-specific protein (NSP) reticulons are expressed in neural and neuroendocrine tissues and cell cultures derived therefrom, while most other cell types lack NSP-reticulons. Three major subtypes have been identified so far, designated NSP-A, NSP-B, and NSP-C. We have investigated the correlation between the degree of neuronal differentiation, determined by morphological and biochemical criteria, and NSP-reticulon subtype expression. For this purpose, several human neuroblastoma cell lines, exhibiting different degrees of neuronal differentiation, were examined immuno(cyto)chemically. It became obvious that the expression of NSP-C, as detected by immunofluorescence microscopy and Western blotting, is most prominent in cell lines with a high degree of neuronal differentiation, such as LA-N-5. Such highly differentiated cells also express other neural and neuroendocrine markers, such as neural cell adhesion molecule (NCAM), neurofilament proteins, synaptophysin, and chromogranin. NSP-A was observed in all cell lines to a different extent. However, no clear correlation was observed with the degree of neuronal differentiation as defined by other neuronal and neuroendocrine markers or morphology. NSP-B could not be detected. The induction of neuronal differentiation with nerve growth factor, dbcAMP, and retinoic acid in the rat pheochromocytoma cell line PC12 and the human teratocarcinoma cell line hNT2, respectively, induced the expression of NSP-A and NSP-C in these cell lines parallel to the induction of neurofilament protein expression. It is concluded that NSP-C expression, in particular, is strongly correlated with neuronal differentiation.

A comparison of NSP-reticulons with conventional neuroendocrine markers in immunophenotyping of lung cancers

Neuroendocrine‐specific protein (NSP)‐reticulons are endoplasmic reticulum‐associated protein complexes, which have been identified as markers for neuroendocrine differentiation. In this study, the expression of two members of the family of NSP‐reticulons, NSP‐A and NSP‐C, have been investigated in different types of lung cancer and compared with the expression patterns of five conventional neuroendocrine markers, the neural cell adhesion molecule (NCAM), synaptophysin, chromogranin A, Leu‐7, and neurofilament proteins. NSP‐A and NSP‐C antibodies were reactive with most carcinoid tumour and small cell lung carcinoma (SCLC) cases, while atypical carcinoid tumours showed a variable expression. In the total group of neuroendocrine tumours, a high concordance of expression was found between NSP‐A and NSP‐C, while their expression correlated well with NCAM and synaptophysin positivity. Chromogranin A, Leu‐7, and neurofilament proteins were shown to be expressed to a limited extent in these neuroendocrine tumours. In a selected group of non‐SCLCs known to exhibit neuroendocrine features, NSP‐A expression was detected at much higher frequency than NSP‐C. In virtually all NSP‐A positive cases, this expression was associated with one or more of the other neuroendocine markers. NSP‐A expression showed a stronger correlation with conventional neuroendocrine markers than NCAM. In detecting neuroendocrine differentiation in non‐SCLC, NSP‐A is more sensitive than synaptophysin, chromogranin A, Leu‐7, and neurofilament proteins. It is concluded that NSP‐reticulons are valuable markers in the diagnosis of neuroendocrine differentiation in non‐SCLC and should be used in conjunction with NCAM.

Neuroendocrine-specific protein (NSP)-reticulons as independent markers for non-small cell lung cancer with neuroendocrine differentiation. An in vitro histochemical study

Abstract Neuroendocrine-specific protein (NSP)-reticulons have recently been discovered and were shown to exhibit a restricted, neuroendocrine/neural-specific expression pattern. These protein aggregates are anchored to the membranes of the endoplasmic reticulum and occur in small cell lung cancer (SCLC), but not in typical non-SCLC. In the current study we have examined the occurrence of NSP-reticulons in non-SCLC cell lines known to express neuroendocrine features (non-SCLC-NE). NSP-reticulon expression was observed in all three non-SCLC-NE cell lines studied, albeit with variable intensity and in varying numbers of cells. Western blot analysis confirmed the presence of NSP-reticulon expression in these non-SCLC-NE cell lines, and showed that they were predominantly of the NSP-A type. When compared to conventional neuroendocrine markers, NSP-reticulons revealed a distinct staining profile, showing only partial overlap with the other markers. The non-SCLC-NE cell lines combined these neuroendocrine characteristics with some features of non-SCLC. We conclude that NSP-reticulon expression is restricted to lung carcinoma cells with a neuroendocrine phenotype and predict that these constituents may become clinically relevant markers for the detection of neuroendocrine differentiation in solid tumours.