Induced expression of dominant-negative c-jun downregulates NF kappa B andAP-1 target genes and suppresses tumor phenotype in human keratinocytes

Jj. Li et al., Induced expression of dominant-negative c-jun downregulates NF kappa B andAP-1 target genes and suppresses tumor phenotype in human keratinocytes, MOL CARCINO, 29(3), 2000, pp. 159-169
Citations number
Categorie Soggetti
Onconogenesis & Cancer Research
Journal title
ISSN journal
0899-1987 → ACNP
Year of publication
159 - 169
SICI code
Neoplastically transformed mouse and human keratinocytes elevate transactiv ation of both activator protein 1 (AP-1) and nuclear factor kappaB (NF kapp aB) transcription factors. The present study addresses the question of whet her elevated NF kappaB in addition to elevated AP-1-dependent gene expressi on is necessary for maintaining the tumor cell phenotype. When a tetracycli ne-regulatable dominant-negative c-jun (TAM67, having a truncated transacti vation domain) was expressed in tumorigenic human keratinocytes, AP-1- and NF kappaB- but not p53-dependent reporter activity was inhibited by 40-60%. Tumor phenotype, as measured by anchorage-independent growth, was inhibite d by 90%. Neither AP-1/NF kappaB activation nor expression of tumor phenoty pe was inhibited in TAM67-harboring keratinocytes under noninducing conditi ons. Electrophoretic mobility shift analysis showed that induction of TAM67 expression slightly increased AP-1- but reduced NF kappaB DNA-binding acti vity. Immunoprecipitation showed that TAM67 interacted in keratinocyte nucl ei with NF kappaB p65, suggesting that inhibition of NF kappaB by TAM67 is mediated by direct protein-protein interactions, possibly producing decreas ed binding to DNA or inactivating p65. To analyze the putative effector gen es that may be targeted by TAM67, expression of genes responsive to AP-1 or NF kappaB was measured by reverse transcriptase-polymerase chain reaction in TAM67 transfectants with or without TAM67 induction. Induction of TAM67 inhibited or reduced the expression of collagenase I, stromelysin I (AP-1 r esponsive), and interleukins 1 and 6 (NF kappaB responsive). These results indicate that genes controlled by NF kappaB and by AP-1 may be transformati on-relevant targets of TAM67 and that TAM67 may inhibit NF kappaB activatio n through direct interaction with NF kappaB p65. Moreover, the findings pro vide proof for the principle of using inducible TAM67 as a gene therapy to suppress tumor phenotype in human carcinoma cells. Published 2000 Wiley-Lis s. Inc.