The nature and biology of neuroendocrine cells and of
tumors derived therefrom have been the subject of intense research using cell
biological and molecular approaches. Diagnostic procedures for establishing the diagnosis of a
neuroendocrine tumor have been improved through the development of new serological markers and imaging procedures. Histopathological diagnosis has been refined by the introduction of a broad spectrum of marker
proteins for different subtypes of neuroendocrine
neoplasms. The high receptor specificity of
somatostatin analogues such as
octreotide or
lanreotide has made these drugs valuable tools in diagnosis and
therapy, and some of the achievements made as well as future directions are reviewed in this article. Another substance in use for
therapy of
neuroendocrine tumors is
interferon-a, whose signal transduction mechanism has been investigated considerably during the past several years. In addition to
biotherapy with
somatostatin analogues and/or
interferon-a,
chemotherapy is an accepted strategy in the treatment of advanced
neuroendocrine tumor disease derived from the foregut. In this context,
streptozotocin has caught some attention due to its somewhat selective toxicity against
neuroendocrine tumor cells. Some recent studies on the role of the
glucose transporter isoform GLUT2 may provide insight into
streptozotocin's action. The
multiple endocrine neoplasia type-1 gene has recently been cloned, sequenced and identified as a gene potentially involved in the development of the familial
cancer syndrome of
multiple endocrine neoplasia type 1 (MEN-1). Mutations of this putative tumor suppressor gene have been described, and the abundance of mutations in MEN-1-related
tumors as well as sporadic
neuroendocrine tumors at MEN-1 locations have been demonstrated. Whether determination of MEN-1 mutations will be valuable for clinical routine is under investigation.