Water channel protein subtype suggests the origin of renal cell carcinoma.
OBJECTIVE
Several subtypes of water selective channel protein have been cloned. In normal kidneys, CHIP-28 (channel forming integral protein of 28 kd) is expressed solely in the proximal tubules and descending thin limbs, and aquaporin-CD (AQP-CD) expression is restricted to collecting ducts. We assessed expression of these 2 distinct types of water channels in renal cancer tissues.


METHODS
Expression of CHIP-28 and AQP-CD was examined in 12 samples of primary renal cell carcinoma by Northern blot, reverse transcriptase-polymerase chain reaction and immunohistochemistry. We also evaluated expression of these 2 molecules immunohistochemically in 4 samples of Bellini duct tumor, which has been thought to arise from renal collecting ducts.


RESULTS
Expression of CHIP-28 was detected in all of the samples of primary renal cell carcinoma, whereas none of them expressed AQP-CD. None of 4 samples of Bellini duct tumor expressed CHIP-28, although expression of AQP-CD was recognized in 2.


CONCLUSIONS
Our current observation confirms the idea of the proximal or descending tubule origin of renal cell carcinoma.
Kageyama
Y
Y
Department of Urology, Tokyo Medical and Dental University School of Medicine, Japan.
Sasaki
S
S
Yamamura
Y
Y
Oshima
H
H
Ikawa
Y
Y
D000368:Aged; D000369:Aged, 80 and over; D051398:Aquaporin 1; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D001483:Base Sequence; D001789:Blood Group Antigens; D002292:Carcinoma, Renal Cell / Q000737:chemistry / Q000209:etiology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007473:Ion Channels / Q000032:analysis / Q000096:biosynthesis*; D007680:Kidney Neoplasms / Q000737:chemistry / Q000209:etiology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data
C496020:AQP1 protein, human; C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D001789:Blood Group Antigens; D007473:Ion Channels; D051398:Aquaporin 1