Differentially expressed protein Pdcd4 inhibits tumor promoter-induced neoplastic transformation.
An mRNA differential display comparison of mouse JB6 promotion-sensitive (P+) and -resistant (P-) cells identified a novel gene product that inhibits neoplastic transformation. The JB6 P+ and P- cells are genetic variants that differ in their transformation response to tumor promoters; P+ cells form anchorage-independent colonies that are tumorigenic, and P- cells do not. A differentially displayed fragment, A7-1, was preferentially expressed in P- cells at levels >/=10-fold those in P+ cells, making its mRNA a candidate inhibitor of neoplastic transformation. An A7-1 cDNA was isolated that was identical to murine Pdcd4 gene cDNAs, also known as MA-3 or TIS, and analogous to human H731 and 197/15a. Until now, the function of the Pdcd4 protein has been unknown. Paralleling the mRNA levels, Pdcd4 protein levels were greater in P- than in P+ cells. Pdcd4 mRNA was also expressed at greater levels in the less progressed keratinocytes of another mouse skin neoplastic progression series. To test the hypothesis that Pdcd4 inhibits tumor promoter-induced transformation, stable cell lines expressing antisense Pdcd4 were generated from parental P- cells. The reduction of Pdcd4 proteins in antisense lines was accompanied by acquisition of a transformation-sensitive (P+) phenotype. The antisense-transfected cells were reverted to their initial P- phenotype by overexpression of a Pdcd4 sense fragment. These observations demonstrate that the Pdcd4 protein inhibits neoplastic transformation.
Cmarik
J L
JL
Basic Research Laboratory, Frederick Cancer Research and Development Center, National Cancer Institute, Frederick, MD 21702, USA. cmarik@ncifcrf.gov
Min
H
H
Hegamyer
G
G
Zhan
S
S
Kulesz-Martin
M
M
Yoshinaga
H
H
Matsuhashi
S
S
Colburn
N H
NH
D000818:Animals; D051017:Apoptosis Regulatory Proteins; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D015870:Gene Expression; D006801:Humans; D015151:Immunoblotting; D015603:Keratinocytes / Q000166:cytology; D051379:Mice; D008807:Mice, Inbred BALB C; D010641:Phenotype; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D051017:Apoptosis Regulatory Proteins; C114487:PDCD4 protein, human; C498443:Pdcd4 protein, mouse; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D013755:Tetradecanoylphorbol Acetate