E. Zeindl-eberhart et al., Proteome analysis of rat hepatomas: Carcinogen-dependent tumor-associated protein variants, ELECTROPHOR, 22(14), 2001, pp. 3009-3018
Proteome analysis led to the identification and characterization of tumor-a
ssociated protein variants by two-dimensional electrophoresis and mass spec
trometry. We focused on comparing the influence of genotoxic nitroso compou
nds N-methyl-N-nitrosourea, diethylnitrosamine and N-nitrosomorpholine and
the nongenotoxic peroxisome proliferator Nafenopin as tumor-inducing agents
on the protein pattern of rat hepatomas. We found several tumor-associated
variants that represent members of the aldo-keto reductase superfamily. Th
eir induction and/or inhibition was specifically related to the carcinogen
used for tumor induction. The most prominent tumor-associated protein, rat
aldose reductase-like protein-1 (rARLP-1) (69% sequence identity to lens al
dose reductase) and three additional types of rARLP-1 were detected in nitr
oso compound-induced rat hepatomas, while rat aldo-keto reductase protein-c
(Rak-c), a novel tumor-associated variant (65% sequence identity with 3 al
pha -hydroxysteroid dehydrogenase) was discovered in N-methyl-N-nitrosourea
-induced hepatomas only. 3 alpha -Hydroxysteroid dehydrogenase and delta4-3
-ketosteroid-5 beta -reductase, both liver-specific enzymes, were reduced i
n amount in all hepatomas investigated, independent of their mode of induct
ion. We conclude, that detoxification enzymes like 3a-hydroxysteroid dehydr
ogenase (3 alpha -HSD) and delta4-3-ketosteroid-5 beta -reductase (5 beta -
Red) might be replaced in hepatomas by tumor-associated proteins that are o
ften present in the embryonal state, like the rARLPs or the Rak-c protein.
Their induction appears to reflect an altered constitutive pattern of detox
ification enzymes, detoxifying toxic aldehydes being induced by nitroso com
pounds. In contrast, members of the aldo-keto reductase superfamily have no
t been found in Nafenopin-induced hepatomas. The pattern of tumor-associate
d protein variants is apparently characteristic for a given group of initia
ting carcinogens. The hypothesis is proposed that carcinogens leave specifi
c fingerprints at the proteome level of manifest liver tumors.