BCR-ABL and Interleukin 3 Promote Haematopoietic Cell Proliferation and Survival through Modulation of Cyclin D2 and p27Kip1 Expression

Abstract

Although it is evident that BCR-ABL can rescue cytokine-deprived hematopoietic progenitor cells from cell cycle arrest and apoptosis, the exact mechanism of action of BCR/ABL and interleukin (IL)-3 to promote proliferation and survival has not been established. Using the pro-B cell line BaF3 and a BaF3 cell line stably overexpressing BCR-ABL (BaF3-p210), we investigated the proliferative signals derived from BCR-ABL and IL-3. The results indicate that both IL-3 and BCR-ABL target the expression of cyclin Ds and down-regulation of p27Kip1 to mediate pRB-related pocket protein phosphorylation, E2F activation, and thus S phase progression. These findings were further confirmed in a BaF3 cell line (TonB.210) where the BCR-ABL expression is inducible by doxycyclin and by using the drug STI571 to inactivate BCR-ABL activity in BaF3-p210. To establish the functional significance of cyclin D2 and p27Kip1 expression in response to IL-3 and BCR-ABL expression, we studied the effects of ectopic expression of cyclin D2 and p27Kip1 on cell proliferation and survival. Our results demonstrate that both cyclin D2 and p27Kip1 have a role in BaF3 cell proliferation and survival, as ectopic expression of cyclin D2 is sufficient to abolish the cell cycle arrest and apoptosis induced by IL-3 withdrawal or by BCR-ABL inactivation, while overexpression of p27 Kip1 can cause cell cycle arrest and apoptosis in the BaF3 cells. Furthermore, our data also suggest that cyclin D2 functions upstream of p27 Kip1 , cyclin E, and cyclin D3, and therefore, plays an essential part in integrating the signals from IL-3 and BCR-ABL with the pRB/E2F pathway.

GSK3β mediates suppression of cyclin D2 expression by tumor suppressor PTEN

“…Furthermore, two phosphatase-defective mutants, PTEN(C124S) and PTEN(G129E), were unable to inhibit the promoter activity, suggesting that PTEN inhibited cyclin D2 by a phosphatase-dependent mechanism. PTEN also inhibited cyclin D2 promoter activity in murine precursor B cells BAF3 (Figure 1d), in which the critical role of cyclin D2 in proliferation has already been demonstrated (Jena et al, 2002;Parada et al, 2001). Similar data were obtained in NIH3T3 cells (Figure 1e) and melanoma B16 cells (Figure 1f), both of which express wild-type PTEN, and in PTEN-null glioblastoma U87 cells (data not shown), in which reintroduction of PTEN can cause growth arrest (Furnari et al, 1997).…”

Glycogen synthase kinase-3β and p38 phosphorylate cyclin D2 on Thr280 to trigger its ubiquitin/proteasome-dependent degradation in hematopoietic cells

“…Recent studies have revealed that GSK3b is a key regulator of numerous signaling pathways and is involved in a wide range of cellular processes, ranging from glycogen metabolism to cell-cycle regulation and proliferation. In murine IL-3-dependent hematopoietic progenitor cell lines, IL-3 has been shown to induce cyclin D2 mRNA and protein expression, mainly through activation of the PI3K-dependent pathway, to promote G1 cell-cycle progression (Ando et al, 1993;Parada et al, 2001;Fox et al, 2005).…”

“…Although the mechanisms for cyclin D2 overexpression in most of these tumors remain to be known, very recent studies showed the aberrant expression of the cyclin D2 gene located at chromosome 12p13 through chromosomal translocations, t(12;14) or t(7;12), in T-cell acute lymphoblastic leukemia (ALL) (Clappier et al, 2006;Karrman et al, 2006). It was also reported that breakpoint cluster region/abelson kinase (BCR/ABL), the fusion tyrosine kinase causing chronic myelogenous leukemia and Ph þ ALL, induces cyclin D2 overexpression, which was found to play a crucial role in proliferation and transformation of hematopoietic cells by BCR/ABL (Deininger et al, 2001;Parada et al, 2001;Jena et al, 2002). Thus, deregulated expression of cyclin D2 may play an important role in pathogenesis of hematopoietic malignancies.…”

Involvement of cell cycle progression in survival signaling through CD40 in the B-lymphocyte line WEHI-231

“…34,35 These observations suggest that expression of antiapoptotic members of the Bcl-2 family is involved in survival induced by cytokines. However, these cytokines reduce the p27 kip1 level and increase the levels of CDKs, 36,37 as is the case for CD40 signaling. Therefore, it could be possible that cytokine-induced full survival requires cell cycle progression through regulation of CDKs and their inhibitors.…”