A Constitutively Active NFATc1 Mutant Induces a Transformed Phenotype in 3T3-L1 Fibroblasts

Abstract

The calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway is best known for its role in T lymphocyte activation. However, it has become increasingly apparent that this signaling pathway is also involved in the regulation of cell growth and development in a wide variety of different tissues and cell types. Here we have investigated the effects of sustained NFATc1 signaling on the growth and differentiation of the murine 3T3-L1 preadipocyte cell line. Remarkably, we find that expression of a constitutively active NFATc1 mutant (caNFATc1) in these immortalized cells inhibits their differentiation into mature adipocytes and causes them to adopt a transformed cell phenotype, including loss of contact-mediated growth inhibition, reduced serum growth requirements, protection from growth factor withdrawal-induced apoptosis, and formation of colonies in semisolid media. Furthermore, we find that caNFATc1-expressing cells acquire growth factor autonomy and are able to proliferate even in the complete absence of serum. We provide evidence that this growth factor independence is caused by the NFATc1-dependent production of a soluble heat-labile autocrine factor that is capable of promoting the growth and survival of wild type 3T3-L1 cells as well as potently inhibiting their differentiation into mature adipocytes. Finally, we demonstrate that cells expressing caNFATc1 form tumors in nude mice. Taken together, these results indicate that deregulated NFATc1 activity is able to induce the immortalized 3T3-L1 preadipocyte cell line to acquire the well established hallmarks of cellular transformation and thereby provide direct evidence for the oncogenic potential of the NFATc1 transcription factor.

Bombesin induces cyclooxygenase-2 expression through the activation of the nuclear factor of activated T cells and enhances cell migration in Caco-2 colon carcinoma cells

“…Moreover, involvement of Gaq-coupled receptors as the GRP-R in the activation of NFAT and in the induction of NFATdependent genes has been described in a variety of cell types (Boss et al, 1996;Horsley and Pavlath, 2002;Liu et al, 2004). Noticeably, recent reports have proposed that NFAT proteins may play an important role in cancer, having shown a direct involvement of NFATmediated transcriptional regulation of different genes, including Cox-2 (Jauliac et al, 2002;Lara-Pezzi et al, 2002;Saurin et al, 2002;Neal and Clipstone, 2003;Holzmann et al, 2004;Yiu and Toker, 2006). As mentioned above, GRP-R and Cox-2 expression in human colon cancer cells correlates with more invasive characteristics.…”

Cyclin D1 Is a Bona Fide Target Gene of NFATc1 and Is Sufficient in the Mediation of Injury-induced Vascular Wall Remodeling

“…It was demonstrated that constitutively active forms of NFATc1 and NFATc2 induce two distinct phenotypes in NIH 3T3 cells; whereas NFATc1 increases their proliferation capacity and transformation (34,35), NFATc2 causes their cell cycle arrest and apoptosis (35). NFATc1 has also been shown to mediate VEGF-induced endothelial cell proliferation (36).…”

Conditional Disruption of Calcineurin B1 in Osteoblasts Increases Bone Formation and Reduces Bone Resorption

“…These bone marrow stem cells are pluripotent and capable of differentiating into several lineages such as chondrocytes, myocytes, and adipocytes in addition to osteoblasts (3). Interestingly, Cn/NFAT signaling has been shown to play a critical role in the lineage decision of stem cells to differentiate into chondrocytes, myocytes, and adipocytes (34,36,37). Indeed, the global deletion of NFATc2 in mice has been shown to increase the expression of chondrocytic-specific genes and chondrogenesis, suggesting that NFATc2 is a negative regulator of chondrocyte growth and differentiation (37).…”