IFN-gamma Induction of p21WAF1 Is Required for Cell Cycle Inhibition and Suppression of Apoptosis

Abstract

Interferons (IFN) inhibit the growth of tumor cells by blocking the progression of their cell cycle. Recently, we showed that this cell cycle inhibition correlates with the ability of IFN to upregulate the cyclin-dependent kinase inhibitor p21(WAF1). This, however, is not proof of a causal relationship. Using p21(WAF1)-deficient cells derived from the HCT116 colon adenocarcinoma cell line, we now show that p21(WAF1) is indeed responsible for the antiproliferative effects of the type II IFN, IFN-gamma. IFN-gamma upregulated p21(WAF1) expression in a p53-independent manner, decreased cyclin-dependent kinase 2 activity, and inhibited entry into the S phase of the cell cycle in p21+/+ but not in p21-/- HCT116 cells. We additionally found that the lack of p21(WAF1) expression resulted in an increase in the ability of IFN-gamma to induce apoptosis, as reflected by an earlier induction of DNA fragmentation and caspase 3 activity in p21-/- cell. Our results indicate that p21(WAF1) expression is necessary for IFN-gamma-mediated cell cycle inhibition and suppression of IFN-gamma-induced apoptosis.

Cytotoxic T Lymphocytes Block Tumor Growth Both by Lytic Activity and IFNγ-Dependent Cell-Cycle Arrest

“…IFNg inhibits cell proliferation via cell type-specific pathways that involve CKIs, such as p21Cip1 (29,30) and p27Kip1 (31,32). It has been shown that STAT1 interacts directly with cyclin D1/ Cdk4 and mediates the cell-cycle arrest of human U3A cells (33).…”

“…Mice transgenic for the pmel-1-TCR, which recognizes the H-2D b -restricted epitope EGSRNQDWL from gp100 (gp100 [25][26][27][28][29][30][31][32][33] ), were obtained from The Jackson Laboratory. All mice were housed in a pathogen-free environment, and all animal procedures were conducted in accordance with institutional guidelines.…”

“…All animal experiments were approved by the University of Tokyo Ethics Committee for Animal Experiments (10-P-127). The H-2D brestricted peptide human gp100 (hgp100 [25][26][27][28][29][30][31][32][33] , KVPRNQDWL) was purchased from GenScript Japan at a purity of >90%, with free amino and carboxyl terminals. B16F10, FBL3, and 3LL cell lines were maintained in culture medium consisting of DMEM with 10% FCS, 100 U/mL penicillin, and 100 mg/mL streptomycin.…”

Functional interaction between p53 and the interferon-inducible nucleoprotein IFI 16

“…Furthermore, the interferon inducible transcription factor IRF-1 has been shown to functionally synergise with p53 (Tanaka et al, 1996). However, IFNs, can regulate proliferation and death in cells that contain functionally inactive, or are absent in, p53 (Subramanium and Johnson, 1997) and addition of IFN-g to p53 null cells can still result in an increase in the levels of p21 waf1/Cip1 (Hobeika et al, 1999). Clearly the molecular pathways leading to IFN-mediated cell death and cell cycle arrest have not yet been completely de®ned.…”

Induction of melanoma-associated antigen systemic immunity upon intratumoral delivery of interferon-γ retroviral vector in melanoma patients

“…IFN-␥ has been shown to up-regulate the cyclin-dependent kinase inhibitor p21 (WAF1). 29,30 The mechanisms of action are suggested to occur through signal transducers and activators of transcription protein-1, which can by activated by IFN-␥. 30 The up-regulation of p21 inhibits entry of cells into the S phase of the cell cycle, thereby causing cell growth arrest.…”