(1-3) In contrast, ER-mediated signals critically affect the growth and progression of several cancers. In particular, the impact of estrogen signals on breast cancer is now well established. (4)(5)(6) Therefore, the current therapeutic strategy to treat ER-positive breast cancer relies on the blockade of ER-mediated signaling by an ER antagonist, such as tamoxifen.(4-6) However, the role of ER-signaling in other cancers is still unclear. In addition, the differences in expression patterns and the exact role of ERα and ERβ on cell growth, invasion and metastasis in various cancer cells have not been elucidated. (7)(8)(9) Human squamous cell carcinoma (SCC) is the most common neoplasm in the oral cavity cancer, and the incidence of lingual carcinoma has recently been increasing. The optimal treatment or therapy for carcinoma of the tongue remains a controversial issue, and surgical operation is still effective for SCC in the field of head and neck surgery. However, the recovery of lost function after a large surgical excision is accompanied by many problems such as speech impediment and dysphagia.(10) Local regional control of head and neck cancer has improved in recent decades. Nevertheless, overall survival remains largely unchanged. (11,12) The major reason for this discrepancy is distant metastasis and secondary neoplasms. (13,14)

Gicerin is a cell adhesion molecule of an immunoglobulin (Ig) superfamily isolated from a chicken. It shows homophilic and heterophilic binding activities and has two isoforms. s-Gicerin which has small cytoplasmic domain and the same extracellular domain as l-gicerin shows stronger cell adhesion activity. In the chick nervous system, gicerin expression is only observed in the developmental stage when neurons extend neurites and migrate. In other tissues, gicerin participates in the tissue regeneration or oncogenesis. In this report, we identified two isoforms of rat gicerin corresponding to chicken and we concluded that gicerin is a homologue of human CD146/MUC18/MCAM. Next we generated antibody to characterize a rat gicerin in the nervous system. Gicerin is expressed in the hippocampal cells, Purkinje cells, and sensory neurons of a spinal chord of an adult rat, while expressed most abundantly in the lung. In addition to this, its expression in the hippocampus was increased by electroconvulsive shock, suggesting some role in the mature nervous system. And we also showed neurite promotion activity of gicerin from hippocampal neurons.

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