PHF14 is required for germinal center B cell development

Germinal centers (GCs), which are the site of antibody diversification and affinity maturation, are vitally important for humoral immunity. GC B cell proliferation is essentially for these processes by providing enough templates for somatic hypermutation (SHM) and serving as a critical mechanism of positive selection. In the current study, we found a significant reduction of GC response in the spleens of GC B cell specific PHF14 knockout (PHF14^{GCB KO}) mice compared with the wild-type control (PHF14^{GCB WT}) when the mice were challenged with SRBCs or lymphocytic choriomeningitis virus. We also demonstrated that PHF14 did not affect the cell survival of GC B cells, but regulated the proliferation of GC B cells. In addition, PHF14 suppressed the expression of Cdkn1a (p21) though regulating the level of H3K4me3 to control the proliferation of GC B cells. Collectively, our data suggest that PHF14 plays an important role in the process of germinal center formation by regulating GC B cell proliferation in spleen.

Silencing expression of PHF14 in glioblastoma promotes apoptosis, mitigates proliferation and invasiveness via Wnt signal pathway

Background

The plant homeodomain (PHD) finger protein 14 (PHF14) is a vital member of PHD finger protein families. Abnormal expression of PHF14 has been identified in various cancers and is known to be implicated in the pathogenesis of tumors. This study investigates the role and the underlying mechanisms of PHF14 in GBM (glioblastoma multiforme).

Methods

Tissue microarrays and public databases interrogation were used to explore the relationship between the expression of PHF14 and GBM. Three stable PHF14-silenced cell lines (U251, U87MG and A172) were constructed to assess the biological functions changes of GBM cells in vitro. In addition, tumorigenicity in vivo was also performed using U87MG cell line. To understand the mechanism of action of PHF14, RNA-Seq, qRT-PCR, Western blot, IC50 assay and subsequent pathway analysis were performed.

Results

Our results showed that the expression of PHF14 was upregulated in glioma, especially in GBM. Overexpression of PHF14 translated to poor prognosis in glioma patients. In vitro assays revealed that silencing expression of PHF14 in glioma cells inhibited migration, invasiveness and proliferation and promoted cell apoptosis. Animal assay further confirmed that over-expression of PHF14 was a dismal prognostic factor. Analysis based on RNA-Seq suggested a PHF14-dependent regulation of Wnt signaling networks, which was further validated by qRT-PCR, Western blot and IC50 analysis. In addition, the mRNA expression of several key markers of EMT (epithelial–mesenchymal transition) and angiogenesis was found to change upon PHF14 silencing.

Conclusions

Our data provide a new insight into the biological significance of PHF14 in glioma and its potential application in therapy and diagnosis.

Pulsed SILAC-based proteomic analysis unveils hypoxia- and serum starvation-induced de novo protein synthesis with PHD finger protein 14 (PHF14) as a hypoxia sensitive epigenetic regulator in cell cycle progression

Hypoxia is an environmental cue that is associated with multiple tumorigenic processes such as immunosuppression, angiogenesis, cancer invasion, metastasis, drug resistance, and poor clinical outcomes. When facing hypoxic stress, cells initiate several adaptive responses such as cell cycle arrest to reduce excessive oxygen consumption and co-activation of oncogenic factors. In order to identify the critical novel proteins for hypoxia responses, we used pulsed-SILAC method to trace the active cellular translation events in A431 cells. Proteomic discovery data and biochemical assays showed that cancer cells selectively activate key glycolytic enzymes and novel ER-stress markers, while protein synthesis is severely suppressed. Interestingly, deprivation of oxygen affected the expression of various epigenetic regulators such as histone demethylases and NuRD (nucleosome remodeling and deacetylase) complex in A431 cells. In addition, we identified PHF14 (the plant homeodomain finger-14) as a novel hypoxia-sensitive epigenetic regulator that plays a key role in cell cycle progress and protein synthesis. Hypoxia-mediated inhibition of PHF14 was associated with increase of key cell cycle inhibitors, p14^ARF, p15^INK4b, and p16^INK4a, which are responsible for G1-S phase transition and decrease of AKT-mTOR-4E-BP1/pS6K signaling pathway, a master regulator of protein synthesis, in response to environmental cues. Analysis of TCGA colon cancer (n=461) and skin cancer (n=470) datasets revealed a positive correlation between PHF14 expression and protein translation initiation factors, eIF4E, eIF4B, and RPS6. Significance of PHF14 gene was further demonstrated by in vivo mouse xenograft model using PHF14 KD cell lines.

A novel PHD-finger protein 14/KIF4A complex overexpressed in lung cancer is involved in cell mitosis regulation and tumorigenesis

The plant homeodomain (PHD) finger-containing proteins have been implicated in many human diseases including cancer. In this study, we found that PHF14, a newly identified PHD finger protein, is highly expressed in lung cancer. The high expression level of PHF14 was associated with adenocarcinoma and poor survival in lung cancer patients. Knocking down PHF14 suppressed cancer cell growth and carcinogenesis, while over-expressing PHF14 promoted cell proliferation. During cell division, PHF14 directly bound to and co-localized with KIF4A (a nuclear motor protein involved in lung carcinogenesis) to form a functional complex. Similarly to the effect of KIF4A depletion, silencing PHF14 in several cell lines caused cell mitotic defects, prolonged M phase, and inhibited cell proliferation. What's more, these two proteins had a synergistic effect on cell proliferation and were significantly co-overexpressed in lung cancer tissues. Our data provide new insights into the biological significance of PHD finger proteins and imply that PHF14 may be a potential biomarker for lung cancer.

Severe persistent pulmonary hypertension of the newborn and dysmorphic features in neonate with a deletion involving TWIST1 and PHF14: a case report

Background

Persistent pulmonary hypertension is a well-known disease of the newborn that in most cases responds well to treatment with nitric oxide and treatment of any underlying causes. Genetic causes of persistent pulmonary hypertension of the newborn are rare. The TWIST1 gene is involved in morphogenetics, and deletions are known to cause Saethre-Chotzen syndrome. Deletions of PHF14 have never been reported in neonates, but animal studies have shown a link between severe defects in lung development and deletions of this gene. There have not, to the best of our knowledge, been any publications of a link between the genes TWIST1 and PHF14 and persistent pulmonary hypertension of the newborn, making this a novel finding.

Case presentation

We describe a white male neonate born at term to non-consanguineous white parents; he presented with dysmorphic features and a therapy-refractory persistent pulmonary hypertension. Array-based comparative genomic hybridization revealed the presence of a 14.7 Mb interstitial deletion on chromosome 7, encompassing the genes TWIST1 and PHF14.

Conclusions

The TWIST1 gene can explain our patient’s dysmorphic features. His severe persistent pulmonary hypertension has, however, not been described before in conjunction with the TWIST1 gene, but could be explained by involvement of PHF14, consistent with findings in animal experiments showing lethal respiratory failure with depletion of PHF14. These findings are novel and of importance for the clinical management and diagnostic workup of neonates with severe persistent pulmonary hypertension of the newborn and dysmorphic features.

Depletion of PHF14, a novel histone-binding protein gene, causes neonatal lethality in mice due to respiratory failure

The plant homeodomain (PHD) finger is identified in many chromatin-binding proteins, and functions as a 'reader' that recognizes specific epigenetic marks on histone tails, bridging transcription factors and their associated complexes to chromatin, and regulating gene expression. PHD finger-containing proteins perform many biological functions and are involved in many human diseases including cancer. PHF14 is predicted to code for a protein with multiple PHD fingers. However, its function is unidentified. The aim of this study is to characterize PHF14 and investigate its biological significance by employing multiple approaches including mouse gene-targeting knockout, and molecular cloning and characterization. Three transcripts of PHF14 in human cell lines were identified by reverse transcriptase polymerase chain reaction. Two isoforms of PHF14 (PHF14α and PHF14β) were cloned in this study. It was found that PHF14 was ubiquitously expressed in mouse tissues and human cell lines. PHF14α, the major isoform of PHF14, was localized in the nucleus and also bound to chromatin during cell division. Interestingly, co-immunoprecipitation results suggested that PHF14α bound to histones via its PHD fingers. Strikingly, gene-targeting knockout of PHF14 in mice resulted in a neonatal lethality due to respiratory failure. Pathological analysis revealed severe disorders of tissue and cell structures in multiple organs, particularly in the lungs. These results indicated that PHF14 might be an epigenetic regulator and play an important role in the development of multiple organs in mouse.

Aberrant expression of the PHF14 gene in biliary tract cancer cells

DNA copy number aberrations in human biliary tract cancer (BTC) cell lines were investigated using a high-density oligonucleotide microarray. A novel homozygous deletion was detected at chromosomal region 7p21.3 in the OZ cell line. Further validation experiments using genomic PCR revealed a homozygous deletion of a single gene, plant homeodomain (PHD) finger protein 14 (PHF14). No PHF14 mRNA or protein expression was detected, thus demonstrating the absence of PHF14 expression in the OZ cell line. Although the PHD finger protein is considered to be involved in chromatin-mediated transcriptional regulation, little is known about the function of PHF14 in cancer. The present study observed that the knock down of PHF14 using small interfering RNA (siRNA) enhanced the growth of the BTC cells. These observations suggest that aberrant PHF14 expression may have a role in the tumorigenesis of BTC.