Anti-sense oligonucleotide of p21(waf1/cip1) prevents Interleukin 4-mediated elevation of p27(kip1) in low grade astrocytoma cells

Abstract

Elevation of the cyclin-dependent kinase (cdk) inhibitor, p27(kip1) is necessary for Interleukin (IL)-4-mediated growth arrest of human low grade astrocytoma (RTLGA) cells and occurs at 24 h of treatment. Pathways involved in IL-4 alteration of p27(kip1) are unknown, however. Here we investigated whether other cdk inhibitors contributed to the actions of IL-4 on RTLGA cells. By 12 h of IL-4 treatment, both cdk4 and cdk2 kinase activities against the retinoblastoma protein (pRb) were reduced and nuclear entry of pRb was prohibited. Twelve-hour cdk complexes contained elevated p21(waf1/cip1) but not p27(kip1), p15(ink4B) or p16(ink4A). IL-4 increased p21(waf1/cip1) but not p27(kip1) mRNA levels, and stimulated luciferase activity of a p21(waf1/cip1) promoter-luciferase reporter. In p53-mutant WITG3 cells, IL-4 did not alter p21(waf1/cip1) mRNA and promoter-luciferase activity or p27(kip1) protein, suggesting a need for functional p53. STAT6 phosphorylation by IL-4, however, occurred in both p53-mutant WITG3 and p53-functional RTLGA cells. Pre-treatment of RTLGA with anti-sense but not missense p21(waf1/cip1) oligonucleotide prior to IL-4: (a) restored cdk activities; (b) reduced cdk4-associated p21(waf1/cip1) levels; (c) prevented p27(kip1) elevation; and (d) reversed growth arrest. These results are the ®rst to suggest that p21(waf1/cip1) is essential for IL-4-mediated elevation of p27(kip1) and growth arrest of astrocytoma cells. Oncogene (2000) 19, 661 ± 669.

Cell cycle-independent upregulation of p27Kip1 by p21Waf1 in K562 cells

“…This does not obviate the probability that stabilization of p27Kip1 by p21Waf1 is a signi®cant physiologic mechanism employed in many settings. This is further supported by the recent report that antisense p21Waf1 prevents p27Kip1 upregulation by IL-4 in astroglioma cells (Liu et al, 2000). It is likely that in many cellular lineages the direct stabilization of p27Kip1 by p21Waf1 helps to coordinate the di erentiation-speci®c functions of these proteins.…”

Upregulation of p27 and its inhibition of CDK2/cyclin E activity following DNA damage by a novel platinum agent are dependent on the expression of p21

“…As we have demonstrated that increases in p27 by DAP are dependent on p21, the observed p21-mediated inhibition of CDK2 activity is the likely mechanism, with resultant decrease in phosphorylation of p27. Although previous reports have suggested that p27 upregulation may involve p21 (Liu et al, 2000;Steinman et al, 2001;MunozAlonso et al, 2005), the present study not only provides definitive evidence for this, but also demonstrates for the first time that this upregulation is robust, inhibits CDK2/cyclin E and occurs in response to DNA damage.…”

“…Therefore, p27 levels may be induced by mechanisms that inhibit p27 degradation, such as that observed with proteasome inhibitors MG132 and lovastatin (Lee and Goldberg, 1998;Rao et al, 1999), or following downregulation of Skp2 by siRNA (Jiang et al, 2005). There are scant reports to suggest that p21 may also increase p27 levels (Liu et al, 2000;Steinman et al, 2001;Munoz-Alonso et al, 2005), but other studies contradict this, as no increases in p27 were demonstrated when p21 was induced either ectopically (Yamamoto et al, 1999) or following treatment with UCN-01 (Facchinetti et al, 2004).…”

IL‐4 blocks M‐CSF‐dependent macrophage proliferation by inducing p21Waf1 in a STAT6‐dependent way

“…Kip1 as an inhibitor of proliferation has been reported to be mediated by p21 Waf1 [47], as has the IL-4-induced differentiation of macrophages [48]. Under our experimental conditions, no increase in p27 Kip1 was found.…”