Silencing of the caspase-1 gene occurs in murine and human renal cancer cells and causes solid tumor growth in vivo.
Renal cell cancer is a unique solid tumor that occasionally shows spontaneous regression even at an advanced stage, of which the underlying mechanism is not well understood. To investigate a potential role of the pro-apoptotic molecule caspase-1 in the growth regulation of renal cell cancer, we created transfectants expressing exogenous caspase-1 from a murine renal cancer cell line, Renca. Overexpression of caspase-1 did not affect the growth of Renca cells in vitro at the exponential phase but induced apoptotic cell death at 50% to 75% confluence, whereas control cells underwent apoptosis only after reaching 100% confluence. When implanted into the flank of a syngeneic BALB/c mouse, caspase-1-overexpressing Renca cells did not effectively establish growth as a solid tumor, forming a measurable tumor in only 7 of 11 (64%) animals, whereas control cells formed a tumor in 6 of 6 (100%) animals. The growth of tumors from caspase-1-overexpressing cells slowed down markedly after the tumors reached 5 to 10 mm in diameter, and histological examination of such tumors revealed numerous apoptotic cells positively stained by TUNEL assay. Interestingly, endogenous caspase-1 was not detected in the tumors from control cells, which re-expressed caspase-1 when they were re-cultured and exposed to a demethylation reagent, 5-aza-2'-deoxycytidine. Furthermore, treatment of a human renal cancer cell line, ACHN, with 5-aza-2'-deoxycytidine also caused recovery of caspase-1 expression, which was not detected before treatment. These data suggest that silencing of caspase-1 through DNA methylation may be involved in the oncogenesis of some renal cell cancers growing as a solid tumor.
Department of Urology, University of Tokyo Hospital, Tokyo, Japan. kueki-tky@umin.ac.jp
T
T
Ueki
T
T
Takeuchi
H
H
Nishimatsu
T
T
Kajiwara
N
N
Moriyama
Y
Y
Narita
K
K
Kawabe
K
K
Ueki
T
T
Kitamura
D000818:Animals; D017209:Apoptosis; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020170:Caspase 1 / Q000235:genetics*; D002455:Cell Division; D004396:Coloring Agents / Q000494:pharmacology; D019175:DNA Methylation; D018076:DNA, Complementary / Q000378:metabolism; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020868:Gene Silencing; D005822:Genetic Vectors; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007680:Kidney Neoplasms / Q000201:enzymology* / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D010957:Plasmids / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism
D004396:Coloring Agents; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D013778:Tetrazolium Salts; D013844:Thiazoles; D019014:fas Receptor; D000077209:Decitabine; D020170:Caspase 1; C022616:thiazolyl blue; D001374:Azacitidine