NEUROENDOCRINE-SPECIFIC PROTEIN (NSP)-RETICULONS AS INDEPENDENT MARKERS FOR NONSMALL CELL LUNG-CANCER WITH NEUROENDOCRINE DIFFERENTIATION -AN IN-VITRO HISTOCHEMICAL-STUDY

Neuroendocrine-specific protein (NSP)-reticulons have recently been di scovered 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 lu ng 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. Wester n 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 marker s, NSP-reticulons revealed a distinct staining profile, showing only p artial overlap with the other markers. The non-SCLC-NE cell lines comb ined these neuroendocrine characteristics with some features of non-SC LC. We conclude that NSP-reticulon expression is restricted to lung ca rcinoma cells with a neuroendocrine phenotype and predict that these c onstituents may become clinically relevant markers for the detection o f neuroendocrine differentiation in solid rumours.