Metastatic rat carcinoma cells express a new retrotransposon

Genes differentially expressed by a rat bladder carcinoma NET-II cells and their in-vivo-selected metastatic M-NBT-II variant were analysed. Amplifica tion and cloning of a 277-bp B sequence, exclusively expressed by the M-NBT -II cells, were performed, and this sequence was detected as a 6.7-kb RNA. This fragment shares 46-50% identities with the gag-related protein of mous e and hamster Intracisternal A Particles (IAPs). Screening of a M-NBT-II cD NA library with the B probe selected a 1671-bp sequence corresponding to th e 5' end of a novel retrotransposon member of the rat IAP family. This sequ ence has a strong identity with the Ecker Rat IAP (ERA-IAP) except for the B portion and has an open reading frame potentially encoding a 114-amino-ac id gag retrovirus-related protein. Rearrangement of this new retrotransposo n could be relevant with the tumor progression in our model system since it is only expressed in the M-NBT-II in-vivo-selected carcinoma metastasis. ( C) 1999 Elsevier Science B.V. All rights reserved.