Inhibition of tumor cell growth by RTP/rit42 and its responsiveness to p53 and DNA damage.
Through a differential screening technique, we have identified a cDNA clone with differential expression in normal versus tumor cells. This clone, designated rit42 (reduced in tumor, 42 kDa), was previously isolated as a homocysteine-inducible gene in human endothelial cells (RTP), and the same or a highly related androgen-responsive gene in mouse has also been identified. Both Northern blot analysis and in situ hybridization demonstrated a significantly diminished expression in tumor cells, including those derived from breast and prostate when compared with normal cells. It was shown that RTP/rit42 mRNA cycles with cell division, peaking at G1 and G2-M, with lower expression in S phase. The biphasic expression of RTP/rit42 mRNA was absent in tumor cells. Introduction of rit42 cDNA into human cancer cells reduced cell growth both in vitro and in nude mice. Moreover, analysis of a tetracycline-regulated p53-inducible system in null-p53 cell lines showed that RTP/rit42 mRNA expression increased concomitantly with p53 expression and followed a similar time course. In addition, DNA-damaging agents induced RTP/rit42 expression in a p53-dependent manner but independent of a p53-mediated G1 arrest. Immunofluorescence analysis of a FLAG epitope-tagged RTP/rit42 protein revealed a cytoplasmic localization pattern with redistribution to the nucleus upon DNA damage. We have localized RTP/rit42 to human chromosome 8q24.3. Taken together, these results are consistent with a growth inhibitory role for RTP/rit42, and its down-regulation may contribute to the tumor malignant phenotype.
Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Harvard Institutes of Medicine, Boston, Massachusetts 02115, USA.
S K
SK
Kurdistani
P
P
Arizti
C L
CL
Reimer
M M
MM
Sugrue
S A
SA
Aaronson
S W
SW
Lee
D000818:Animals; D001943:Breast Neoplasms; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics*; D002455:Cell Division; D002478:Cells, Cultured; D002874:Chromosome Mapping; D002898:Chromosomes, Human, Pair 8; D004249:DNA Damage; D003609:Dactinomycin / Q000633:toxicity; D004317:Doxorubicin / Q000633:toxicity; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005260:Female; D015723:Gene Library; D016158:Genes, p53; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D016685:Mitomycin / Q000633:toxicity; D016133:Polymerase Chain Reaction; D011471:Prostatic Neoplasms; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics; D001749:Urinary Bladder Neoplasms; D000099259:N-myc Downstream-Regulated Gene 1 Protein
D018797:Cell Cycle Proteins; D003609:Dactinomycin; D004317:Doxorubicin; D047908:Intracellular Signaling Peptides and Proteins; D016685:Mitomycin; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D000099259:N-myc Downstream-Regulated Gene 1 Protein