Distribution and Variable Expression of Secretory Pathway Protein Reticulocalbin in Normal Human Organs and Non-neoplastic Pathologic Conditions

Takeaki Fukuda ^1*, Hiroshi Oyamada ¹, Takuma Isshiki ¹, Masahiro Maeda ¹, Takashi Kusakabe ¹, Ayumi Hozumi ¹, Tomiko Yamaguchi ¹, Toshihiko Igarashi ¹, Hidehiro Hasegawa ¹, Tsutomu Seidoh ¹ and Toshimitsu Suzuki ¹

¹ Second Department of Pathology, Fukushima Medical University School of Medicine, Fukushima, Japan (TF,HO,TI,TK,AH,TY,TS); Division of Histopathology, Central Hospital of Niigata Agriculture Association, Nagaoka, Japan (TI,HH); and Immunobiological Laboratories, Fujioka, Gunma, Japan (MM,TS)

^* To whom correspondence should be addressed. E-mail: doraemon{at}fmu.ac.jp .

Submitted on February 6, 2006
Accepted on 30 November 2006

	Abstract

Reticulocalbin (RCN) is one member of the Ca²⁺-binding proteins in the secretory pathway, and localized in the endoplasmic reticulum. RCN may play a role in the normal behavior and life of cells, although its detailed role remains unknown. Overexpression of RCN may also play a role in tumorigenesis, tumor invasion, and in drug resistance. The new antibody for human RCN is employed in the distribution of RCN in normal human organs of fetuses and adults with or without inflammation. Immunohistochemical examination demonstrated a broad distribution of RCN in various organs of fetuses and adults, predominantly in the endocrine and exocrine organs. However, RCN expression was heterogeneous in each constituent cell of some organs. Among non-epithelial organs, vascular endothelial cells, testicular germ cells, neurons, and follicular dendritic cells showed strong staining. Plasma cells were the only RCN positive cells amongst hematopoietic and lymphoid cells. In inflammatory conditions, RCN expression was enhanced in both epithelial and non-epithelial cells. Heterogeneous expression of RCN indicates that the amount of RCN needed for cell behavior and life may be variable depending on each cell type, and therefore RCN may be helpful in establishing the cell origin of neoplasms in some organs. However, further study is needed to establish the significance of RCN in tumorigenesis, and some peculiar features of neoplasms.

Key Words: reticulocalbin, overexpression, cellular localization, secretory pathway, immunohistochemistry

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