L-type amino acid transporter 1 (LAT1) is frequently expressed in thymic carcinomas but is absent in thymomas.
BACKGROUND
L-type amino acid transporter 1 (LAT1) has been associated with tumor growth and is highly expressed in the primary human neoplasms. We investigated the significance of LAT1 expression to evaluate malignant potential in thymic epithelial tumors.


METHODS
Immunohistochemical studies of 45 surgically resected thymic epithelial tumors [15 noninvasive thymomas (NT), 22 invasive thymomas (IT), and 8 thymic carcinomas (TC)] were conducted. LAT1, Ki-67 labeling index (LI), vascular endothelial growth factor (VEGF), and microvessel density of the thymic epithelial tumors were analyzed.


RESULTS
LAT1 expression for thymomas and thymic carcinomas were 0 (0%) of 37 and 6 (75%) of eight patients, respectively. Ki-67 LI for NT, IT, and TC were 7.9 +/- 2.8%, 16.1 +/- 8.5%, and 50.6 +/- 24.4%, respectively. VEGF expression in groups NT, IT, and TC was 0 (0%) of 15, 9 (41%) of 22, and 6 (75%) of eight patients, respectively. VEGF expression was statistically associated with microvessel count. The LAT1 expression was statistically associated with Ki-67 LI, VEGF, and microvessel density in thymic carcinomas.


CONCLUSIONS
LAT1 is frequently expressed in thymic carcinomas but is absent in thymomas. Our results suggest that LAT1 expression might be an immunohistochemical marker for carcinomas, and could distinguish between thymomas and thymic carcinomas.
Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma 371-8511, Japan. kkaira1970@yahoo.co.jp
Kyoichi
K
Kaira
Noboru
N
Oriuchi
Hisao
H
Imai
Kimihiro
K
Shimizu
Noriko
N
Yanagitani
Noriaki
N
Sunaga
Takeshi
T
Hisada
Tamotsu
T
Ishizuka
Yoshikatsu
Y
Kanai
Hitoshi
H
Endou
Takashi
T
Nakajima
Masatomo
M
Mori
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002277:Carcinoma / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D027283:Large Neutral Amino Acid-Transporter 1 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D013945:Thymoma / Q000378:metabolism*; D013953:Thymus Neoplasms / Q000378:metabolism*
D014408:Biomarkers, Tumor; D027283:Large Neutral Amino Acid-Transporter 1