Alarin, a 25
amino acid splice variant of the
galanin-like peptide, was originally discovered in gangliocytes of neuroblastic
tumors and shown to be expressed in
ganglioneuroblastoma and
ganglioneuroma but not in undifferentiated
neuroblastoma. Recently, in vivo studies have elucidated the physiological functions of
alarin in the central nervous system (CNS).
Alarin was shown to stimulate food intake, increase
body weight, induce
luteinizing hormone secretion and stimulate fos-expression in rats; the anatomical localization for these functions correlates well with the varied distribution of the
alarin peptide in the brain. Because
alarin was originally detected in neuroblastic
tumors and is present in a wide range of nuclei in the CNS, we determined in the present study the expression of
alarin in a variety of CNS
tumors. Immunohistochemical analysis of 179
tumor samples resulted in different
alarin-like immunoreactivity (
alarin-LI) intensities, which were score-rated from 0 (no
alarin stainin), 1 (low intensity), 2 (medium intensity) to 3 (high intensity). Immunohistochemical analyses revealed score 2 or 3
alarin-LI in all
choroid plexus tumors (100 %, 7/7) and in the majority of
ependymomas (90 %, 52/58), but only in a minority of
astrocytomas (15 %, 5/33),
meningiomas (14 %, 7/49) and
tumors of the cranial nerves (7 %, 1/15). In
oligodendrogliomas (0 %, 0/12) and oligoastrocytoma (0 %, 0/5)
alarin-LI was not detectable. The high specificity (83 %) of
alarin-LI suggests that it might be used as a diagnostic marker for
ependymoma in differentiating them from other
gliomas such as
astrocytomas and
oligodendrogliomas.