Immunostaining for calcineurin, a Ca2+/calmodulin-regulated protein phosphatase, in the diagnostic tumor pathology

The present immunochemical study concerns the distribution of calcineurin (CaN), a Ca2+/calmodulin-regulated protein phosphatase, in the nervous and neuroendocrine systems of mammals, and discloses the CaN-immunostaining results of human neoplasms. CaN immunoreactivity (ir) was present throughout the nervous system with a marked regional variation in strength of the staining intensity. Light microscopic observations showed that CaN-ir was localized in neurons, but was not detected in non-neuronal cells including astrocytes. Ultrastructural study also revealed that CaN-ir was present only in neuronal elements such as somata, dendrites including postsynaptic densities and spines, and nerve terminals. CaN-ir was also detected in neuroendocrine cells of some endocrine tissues including the pineal gland, pituitary gland, adrenal grand, pancreas and thyroid gland. Immunostaining results of 107 surgical specimens of human neoplasms, including 9 cases of peripheral tumors, disclosed that CaN-immunopositive tumor cells were found to be present in the neuronal tumors including neuroblastomas, ganglioglioma, ganglioneuroma, ganglioneuroblastoma, retinoblastomas, medulloblastomas and central neurocytomas. Also, some neuroendocrine tumors, such as pineocytomas, olfactory neuroblastomas and paragangliomas, specifically reacted for anti-CaN antibody. On the basis of these immunochemical findings, we have proposed that CaN can be a marker protein for detection of neuronal and neuroendocrine tumor cells in the diagnostic pathology of human neoplasms.