Nuclear factor of activated T3 is a negative regulator of Ras-JNK1/2-AP-1 induced cell transformation

Ribosomal S6 kinase 2-forkhead box protein O4 signaling pathway plays an essential role in melanogenesis

Although previous studies have examined the signaling pathway involved in melanogenesis through which ultraviolet (UV) or α-melanocyte-stimulating hormones (α-MSH) stimuli act as key inducers to produce melanin at the stratum basal layer of the epidermis, the signaling pathway regulating melanogenesis is still controversial. This study reports that α-MSH, not UVA and UVB, acted as a major stimulus of melanogenesis in B16F10 melanoma cells. Signaling pathway analysis using gene knockdown technology and chemical inhibitors, the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK)/p90 ribosomal S6 kinase 2 (RSK2) played an important role in melanogenesis. Unexpectedly, LY294002, a PI3K inhibitor, increased melanogenesis without UV or α-MSH stimulation, suggesting that the PI3K/AKT signaling pathway may not be a major signaling pathway for melanogenesis. Chemical inhibition of the MEKs/ERKs/RSK2 signaling pathway using U0126 or BI-D1870 suppressed melanogenesis by stimulation of UVA or α-MSH stimulation, or both. In particular, the genetic depletion of RSK2 or constitutive active (CA)-RSK2 overexpression showed that RSK2 plays a key role in melanogenesis. Interestingly, forkhead box protein O4 (FOXO4) was phosphorylated by RSK2, resulting in the increase of FOXO4's transactivation activity. Notably, the FOXO4 mutant harboring serine-to-alanine replacement at the phosphorylation sites totally abrogated the transactivation activity and reduced melanin production, indicating that RSK2-mediated FOXO4 activity plays a key role in melanogenesis. Furthermore, kaempferol, a flavonoid inhibiting the RSK2 activity, suppressed melanogenesis. In addition, FOXO4-wt overexpression showed that FOXO4 enhance melanin synthesis. Overall, the RSK2-FOXO4 signaling pathway plays a key role in modulating melanogenesis.

Recent knowledge of NFATc4 in oncogenesis and cancer prognosis

Nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4), a transcription factor of NFAT family, which is activated by Ca²⁺/calcineurin signaling. Recently, it is reported that aberrantly activated NFATc4 participated and modulated in the initiation, proliferation, invasion, and metastasis of various cancers (including cancers of the lung, breast, ovary, cervix, skin, liver, pancreas, as well as glioma, primary myelofibrosis and acute myelocytic leukemia). In this review, we cover the latest knowledge on NFATc4 expression pattern, post-translational modification, epigenetic regulation, transcriptional activity regulation and its downstream targets. Furthermore, we perform database analysis to reveal the prognostic value of NFATc4 in various cancers and discuss the current unexplored areas of NFATc4 research. All in all, the result from these studies strongly suggest that NFATc4 has the potential as a molecular therapeutic target in multiple human cancer types.

Tacrolimus and ascomycin inhibit melanoma cell growth, migration and invasion via targeting nuclear factor of activated T-cell 3

Melanoma is the most malignant form of skin cancer with high metastatic potential. Nuclear factor of activated T-cells (NFATs) are discovered as transcription factors that regulate the expression of proinflammatory cytokines and other genes during the immune response. Among five NFAT members, NFAT3 is exclusively not expressed in immune cells and its role in progression of different types of cancer remains controversial. Our previous study showed that NFAT3 was highly expressed in skin cancer compared with normal skin tissues and critical for melanoma cell survival and tumor growth. Here, we reported that knockdown of NFAT3 expression, as well as treatment with the calcineurin (CaN) inhibitors, tacrolimus (FK506) or ascomycin (FK520) inhibits melanoma cell migration and invasion, and also proliferation and colony formation. Mechanistic studies revealed that FK506 or FK520 blocked the nuclear translocation and reduced the transcriptional activity of NFAT3. These data support that the antimelanoma effect of FK506 and FK520 is partially mediated by inhibiting the oncogenic factor NFAT3, suggesting that therapeutics based on NFAT3 inhibition may be effective in clinical melanoma treatment.

MicroRNA-24 regulates vascular remodeling via inhibiting PDGF-BB pathway in diabetic rat model

PURPOSE

Hyperglycemia is the high risk factor of vascular remodeling induced by angioplasty, and neointimal hyperplasia is strongly implicated in the pathogenesis of vascular remodeling caused by carotid artery balloon injury. Studies have shown that MicroRNA 24 (miR-24) plays an important role in angiocardiopathy, However, the role of miR-24 is far from thorough research. In this study, we investigate whether up-regulation of miR-24 by using miR-24 recombinant adenovirus (Ad-miR-24-GFP) can inhibit PDGF-BB signaling pathway and attenuate vascular remodeling in the diabetic rat model.

METHODS

Male Sprague-Dawley rats (n = 60) were randomly divided into 5 groups and fed with high sugar and high fat diet (Sham, Saline, Scramble, Ad-miR-24 groups), or ordinary diet (Control group). The front four groups were treated with streptozotocin (STZ) four weeks later and the blood glucose level was closely monitored. After the successful establishment of diabetic rats, the external carotid artery was injured by pressuring balloon 1.5 after internal carotid artery ligation, then the blood vessels were harvested 14 days later and indexes were detected including the following: HE staining for the level of vascular intima thickness, immunohistochemical detection for PCNA and P27 to test the proliferative degree of vascular smooth muscle cells (VSMCs), qRT-PCR for the level of miR-24, RAS,PDGF-R, western blot for the protein levels of JNK1/2, p- JNK1/2, ERK1/2, p-ERK1/2, RAS, PDGF-R, AP-1,P27 and PCNA. Serological detection was conducted for TNF-α, IL-6, IL-8.

RESULTS

The delivery of Ad-miR-24 into balloon injury site has significantly increased the level of miR-24. Up-regulation of miR-24 could regulate vascular remodeling effectively, lower the level of inflammatory factors, inhibit the expression of mRNA and protein levels of JNK1/2, ERK1/2, RAS, PDGF-R, AP-1, P27, PCNA.

CONCLUSION

miR-24 can inhibit the expression of AP-1 via the inhibition of PDGF-BB signaling pathway, thus inhibit VSMCs proliferation and vascular remodeling.

Phosphorylation of NFAT3 by CDK3 induces cell transformation and promotes tumor growth in skin cancer

The nuclear factor of activated T cells (NFAT) family proteins are transcription factors that regulate the expression of pro-inflammatory cytokines and other genes during the immune response. Although the NFAT proteins have been extensively investigated in the immune system, their role in cancer progression remains controversial. Here, we report that NFAT3 is highly expressed in various skin cancer cell lines and tumor tissues. Knockdown of endogenous NFAT3 expression by short hairpin RNA (shRNA) significantly inhibited tumor cell proliferation, colony formation and anchorage-independent cell growth. Furthermore, results of the mammalian two-hybrid assay showed that cyclin-dependent kinase 3 (CDK3) directly interacted with NFAT3 and phosphorylated NFAT3 at serine 259 (Ser259), which enhanced the transactivation and transcriptional activity of NFAT3. The phosphorylation site of NFAT3 was critical for epidermal growth factor (EGF)-stimulated cell transformation of the HaCaT immortalized skin cell line and mutation of NFAT3 at Ser259 led to a reduction of colony formation in soft agar. We also found that overexpressing wildtype NFAT3, but not mutant NFAT3-S259A, promoted A431 xenograft tumor growth. Importantly, we showed that CDK3, NFAT3 and phosphorylated NFAT3-Ser259 were highly expressed in skin cancer compared with normal skin tissues. These results provided evidence supporting the oncogenic potential of NFAT3 and suggested that CDK3-mediated phosphorylation of NFAT3 has an important role in skin tumorigenesis.

Integrative Analysis of mRNA, microRNA, and Protein Correlates of Relative Cerebral Blood Volume Values in GBM Reveals the Role for Modulators of Angiogenesis and Tumor Proliferation

Dynamic susceptibility contrast-enhanced magnetic resonance imaging is routinely used to provide hemodynamic assessment of brain tumors as a diagnostic as well as a prognostic tool. Recently, it was shown that the relative cerebral blood volume (rCBV), obtained from the contrast-enhancing as well as -nonenhancing portion of glioblastoma (GBM), is strongly associated with overall survival. In this study, we aim to characterize the genomic correlates (microRNA, messenger RNA, and protein) of this vascular parameter. This study aims to provide a comprehensive radiogenomic and radioproteomic characterization of the hemodynamic phenotype of GBM using publicly available imaging and genomic data from the Cancer Genome Atlas GBM cohort. Based on this analysis, we identified pathways associated with angiogenesis and tumor proliferation underlying this hemodynamic parameter in GBM.

NFAT2 Isoforms Differentially Regulate Gene Expression, Cell Death, and Transformation through Alternative N-Terminal Domains

The NFAT (nuclear factor of activated T cells) family of transcription factors is composed of four calcium-responsive proteins (NFAT1 to -4). The NFAT2 (also called NFATc1) gene encodes the isoforms NFAT2α and NFAT2β that result mainly from alternative initiation exons that provide two different N-terminal transactivation domains. However, the specific roles of the NFAT2 isoforms in cell physiology remain unclear. Because previous studies have shown oncogenic potential for NFAT2, this study emphasized the role of the NFAT2 isoforms in cell transformation. Here, we show that a constitutively active form of NFAT2α (CA-NFAT2α) and CA-NFAT2β distinctly control death and transformation in NIH 3T3 cells. While CA-NFAT2α strongly induces cell transformation, CA-NFAT2β leads to reduced cell proliferation and intense cell death through the upregulation of tumor necrosis factor alpha (TNF-α). CA-NFAT2β also increases cell death and upregulates Fas ligand (FasL) and TNF-α in CD4(+) T cells. Furthermore, we demonstrate that differential roles of NFAT2 isoforms in NIH 3T3 cells depend on the N-terminal domain, where the NFAT2β-specific N-terminal acidic motif is necessary to induce cell death. Interestingly, the NFAT2α isoform is upregulated in Burkitt lymphomas, suggesting an isoform-specific involvement of NFAT2 in cancer development. Finally, our data suggest that alternative N-terminal domains of NFAT2 could provide differential mechanisms for the control of cellular functions.

Licochalcone A, a natural inhibitor of c-Jun N-terminal kinase 1

The c-Jun N-terminal kinases (JNK) play an important role in many physiologic processes induced by numerous stress signals. Each JNK protein appears to have a distinct function in cancer, diabetes, or Parkinson's disease. Herein, we found that licochalcone A, a major phenolic constituent isolated from licorice root, suppressed JNK1 activity but had little effect on JNK2 in vitro activity. Although licochalcone A binds with JIP1 competitively with either JNK1 or JNK2, a computer simulation model showed that after licochalcone A binding, the ATP-binding cleft of JNK1 was distorted more substantially than that of JNK2. This could reduce the affinity of JNK1 more than JNK2 for ATP binding. Furthermore, licochalcone A inhibited JNK1-mediated, but not JNK2-mediated, c-Jun phosphorylation in both ex vivo and in vitro systems. We also observed that in colon and pancreatic cancer cell lines, JNK1 is highly expressed compared with normal cell lines. In cancer cell lines, treatment with licochalcone A or knocking down JNK1 expression suppressed colon and pancreatic cancer cell proliferation and colony formation. The inhibition resulted in G1 phase arrest and apoptosis. Moreover, an in vivo xenograft mouse study showed that licochalcone A treatment effectively suppressed the growth of HCT116 xenografts, without affecting the body weight of mice. These results show that licochalcone A is a selective JNK1 inhibitor. Therefore, we suggest that because of the critical role of JNK1 in colon cancer and pancreatic carcinogenesis, licochalcone A might have preventive or therapeutic potential against these devastating diseases.

JNK1 and 2 play a negative role in reprogramming to pluripotent stem cells by suppressing Klf4 activity

Embryonic stem (ES) cells are pluripotent cells with the capacity for unlimited self-renewal or differentiation. Inhibition of MAPK pathways enhances mouse ES cell pluripotency characteristics. Compared to wildtype ES cells, jnk2(-/-) ES cells displayed a much higher growth rate. To determine whether JNKs are required for stem cell self-renewal or differentiation, we performed a phosphorylation kinase array assay to compare mouse ES cells under LIF+ or LIF- culture conditions. The data showed that activation of JNKs was induced by LIF withdrawal. We also found that JNK1 or 2 phosphorylated Klf4 at threonines 224 and 225. Activation of JNK signaling and phosphorylation of Klf4 inhibited Klf4 transcription and transactivation activity. Importantly, jnk1(-/-) and jnk2(-/-) murine embryonic fibroblasts (MEFs) exhibited a significantly greater potency in the ability to increase the number of iPS colonies compared with jnk wildtype MEFs. Overall, our results demonstrated that JNK1 and 2 play a negative role in reprogramming to pluripotent stem cells by suppressing Klf4 activity.

Phosphorylation of moesin by c-Jun N-terminal kinase is important for podosome rosette formation in Src-transformed fibroblasts

Podosomes are actin-based membrane protrusions that facilitate extracellular matrix degradation and invasive cell motility. Podosomes can self-organize into large rosette-like structures in Src-transformed fibroblasts, osteoclasts, and some highly invasive cancer cells. However, the mechanism of this assembly remains obscure. In this study, we show that the suppression of c-Jun N-terminal kinase (JNK) by the JNK inhibitor SP600125 or short-hairpin RNA inhibited podosome rosette formation in SrcY527F-transformed NIH3T3 fibroblasts. In addition, SrcY527F was less potent to induce podosome rosettes in JNK1-null or JNK2-null mouse embryo fibroblasts than in their wild-type counterparts. The kinase activity of JNK was essential for promoting podosome rosette formation but not for its localization to podosome rosettes. Moesin, a member of the ERM (ezrin, radixin, and moesin) protein family, was identified as a substrate of JNK. We show that the phosphorylation of moesin at Thr558 by JNK was important for podosome rosette formation in SrcY527F-transformed NIH3T3 fibroblasts. Taken together, our results unveil a novel role of JNK in podosome rosette formation by phosphorylating moesin.

Nuclear factor of activated T cells (NFAT) signaling regulates PTEN expression and intestinal cell differentiation

Previously we demonstrated that overexpression of PTEN enhanced intestinal cell differentiation. In this study we provide evidence showing that NFATc1 and NFATc4 are regulators of PTEN expression. Importantly, our results suggest that NFATc1 and NFATc4 regulation of intestinal cell differentiation may be through PTEN regulation.

The nuclear factor of activated T cell (NFAT) proteins are a family of transcription factors (NFATc1–c4) involved in the regulation of cell differentiation and adaptation. Previously we demonstrated that inhibition of phosphatidylinositol 3-kinase or overexpression of PTEN enhanced intestinal cell differentiation. Here we show that treatment of intestinal-derived cells with the differentiating agent sodium butyrate (NaBT) increased PTEN expression, NFAT binding activity, and NFAT mRNA expression, whereas pretreatment with the NFAT signaling inhibitor cyclosporine A (CsA) blocked NaBT-mediated PTEN induction. Moreover, knockdown of NFATc1 or NFATc4, but not NFATc2 or NFATc3, attenuated NaBT-induced PTEN expression. Knockdown of NFATc1 decreased PTEN expression and increased the phosphorylation levels of Akt and downstream targets Foxo1 and GSK-3α/β. Furthermore, overexpression of NFATc1 or the NFATc4 active mutant increased PTEN and p27^kip1 expression and decreased Akt phosphorylation. In addition, pretreatment with CsA blocked NaBT-mediated induction of intestinal alkaline phosphatase (IAP) activity and villin and p27^kip1 expression; knockdown of either NFATc1 or NFATc4 attenuated NaBT-induced IAP activity. We provide evidence showing that NFATc1 and NFATc4 are regulators of PTEN expression. Importantly, our results suggest that NFATc1 and NFATc4 regulation of intestinal cell differentiation may be through PTEN regulation.