Dissemination feature based on PET/CT is a risk factor for diffuse large B cell lymphoma patients outcome.

BACKGROUND: 18F-FDG PET/CT provides precise information about dissemination of lymphoma lesions. Dmax, defined as distance between the two lesions that were farthest apart by PET/CT, was found to be a promising predictor of Diffuse large B-cell lymphoma (DLBCL) outcome in a small size of clinical trial data. We analyzed the impact of Dmax on the outcome of a large real-world DLBCL cohort. METHODS: Data of newly diagnosed DLBCL at the Third Affiliated Hospital of Soochow University were retrospectively collected. Baseline Dmax, clinical data and survival information were recorded. A metabolic parameter, metabolic bulk volume (MBV), was also measured to verify the independent impact of Dmax. RESULTS: Optimal cut-off values for Dmax and MBV were 45.34 cm and 21.65 cm3. With a median follow-up of 32 months, Dmax significantly impacted progression-free survival (PFS) and overall survival (OS) in 253 DLBCL patients. For Dmaxlow and Dmaxhigh groups, estimated 3-year OS were 87.0% and 53.8% (p < 0.001), while 3-year PFS were 77.3% and 37.3% (p < 0.001). And for MBVlow and MBVhighgroups, 3-year OS were 84.5% and 58.8% (p < 0.001), and 3-year PFS were 68.7% and 50.4% (p = 0.003). Multivariate analysis identified Dmax and Eastern Cooperative Oncology Group performance status (ECOG PS) independently associated with PFS and OS, while MBV only independently associated with OS. A Dmax revised prognostic index (DRPI) combining Dmax and ECOG PS identified an ultra-risk DLBCL population with 3-year PFS of 31.7% and 3-year OS of 38.5%. The area under the curve (AUC) showed that this model performed better than International prognostic Index (IPI). CONCLUSION: Dmax is a new and promising indicator to investigate dissemination of lymphoma lesions associated with the outcome of DLBCL. It significantly contributes to stratification of patients with disparate outcomes. TRIAL REGISTRATION: This research has been retrospectively registered in the Ethics Committee institutional of the Third Affiliated Hospital of Soochow University, and the registration number was approval No. 155 (approved date: 31 May 2022).

Altered serum lipid levels are associated with prognosis of diffuse large B cell lymphoma and influenced by utility of rituximab.

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma, and the prognosis of the disease varied. This research aims to investigate the impact of serum lipid level on the outcome of DLBCL patients and their interaction with rituximab (RTX). Data of newly diagnosed DLBCL in the third affiliated hospital of Soochow University were retrospectively collected. Baseline serum lipid levels, clinical data, and survival information were simultaneously recorded. Data of healthy controls were collected with age matching. Serum lipid levels significantly differed for the patients. All were transformed into categorical variables for the analysis of survival. During a median follow-up of 58 months, 32.8% patients died. Univariate analysis revealed all serum lipid indicators were associated with overall survival (OS); all except for total cholesterol (TC) and apolipoprotein B (apoB) showed significant impact on progression-free survival (PFS). Multivariable analysis confirmed the adverse effect of triglyceride (TG) on PFS (P = 0.013) and favorable impact of high-density lipoprotein (HDL) on OS (P = 0.003). For cases treated without RTX, apolipoprotein A (apoA) had independent favorable effect on both PFS (P = 0.004) and OS (P = 0.001). Comparably, for patients who received RTX, HDL showed remarkably predictive value of PFS (P = 0.011) and OS (P = 0.019). In conclusion, the abnormal serum lipids occurred throughout the course of DLBCL, and the associations of serum lipids and the prognosis of the disease were interfered by RTX. Trial registration: 2022()CL033; June 26, 2022, retrospectively registered.

Circulating tumor DNA: clinical roles in diffuse large B cell lymphoma.

Diffuse large B cell lymphoma (DLBCL), the most common non-Hodgkin lymphoma (NHL), is a clinically and molecularly heterogeneous malignant lymphoproliferative disease. In the era of personalized medicine, genetic information is critical to early diagnosis, aiding risk stratification, directing therapeutic option, and monitoring disease relapse. However, lacking a circulating disease with most DLBCL cases hampers the acquisition of tumor genomic landscapes and disease dynamics. Circulating tumor DNA (ctDNA) is a novel noninvasive, real-time, and tumor-specific biomarker, reliably reflecting the comprehensive tumor genetic profiles, thus holds great promise in individualized medicine, including precise diagnosis and prognosis, response monitoring, and relapse detection of DLBCL. Here, we reviewed the recent advances of ctDNA in DLBCL and discussed its clinical values at different time points during the disease courses by comparing with the current routine methods in clinical practice. Collectively, we anticipated that ctDNA will ultimately be integrated into the management of DLBCL to facilitate precision medicine.

Effects of Lewis Acidic Metal Ions (M) on Oxygen-Atom Transfer Reactivity of Heterometallic Mn3MO4 Cubane and Fe3MO(OH) and Mn3MO(OH) Clusters.

The modulation of the reactivity of metal oxo species by redox inactive metals has attracted much interest due to the observation of redox inactive metal effects on processes involving electron transfer both in nature (the oxygen-evolving complex of Photosystem II) and in heterogeneous catalysis (mixed-metal oxides). Studies of small-molecule models of these systems have revealed numerous instances of effects of redox inactive metals on electron- and group-transfer reactivity. However, the heterometallic species directly involved in these transformations have rarely been structurally characterized and are often generated in situ. We have previously reported the preparation and structural characterization of multiple series of heterometallic clusters based on Mn3 and Fe3 cores and described the effects of Lewis acidity of the heterometal incorporated in these complexes on cluster reduction potential. To determine the effects of Lewis acidity of redox inactive metals on group transfer reactivity in structurally well-defined complexes, we studied [Mn3MO4], [Mn3MO(OH)], and [Fe3MO(OH)] clusters in oxygen atom transfer (OAT) reactions with phosphine substrates. The qualitative rate of OAT correlates with the Lewis acidity of the redox inactive metal, confirming that Lewis acidic metal centers can affect the chemical reactivity of metal oxo species by modulating cluster electronics.

Striving for Positive Aging Among Chinese Older People: Effects of Life Stress and Control Beliefs in a Longitudinal Study.

We examined effects of life stress and control beliefs on a constellation of subjective indicators of well-being for older people, including meaning in life, happiness, peace of mind, and positive aging perception. The Chinese cultural background provided the sociocultural milieu for the present study. In a longitudinal study, 301 older Chinese adults completed a questionnaire survey twice, 6 months apart. Regression analyses found that stress caused by major life-changing events (acute) and financial hardship (chronic) were consistent negative predictors of all well-being indicators. Furthermore, primary control belief (tenacious goal pursuit) amplified the negative impacts of life events on happiness and peace of mind. Secondary control belief (submitting to circumstances), in contrast, acted as a buffer that alleviated the deleterious effects of financial hardship on peace of mind and meaning in life. Noting the threats of unfavorable life circumstances and the potency of secondary control belief for older Chinese people, theoretical and cultural implications were discussed.

Effect of Hypoxia-regulated Polo-like Kinase 3 (Plk3) on Human Limbal Stem Cell Differentiation.

Hypoxic conditions in the cornea affect epithelial function by activating Polo-like kinase 3 (Plk3) signaling and the c-Jun·AP-1 transcription complex, resulting in apoptosis of corneal epithelial cells. Hypoxic stress in the culture conditions also regulates limbal stem cell growth and fate. In this study, we demonstrate that there is a differential response of Plk3 in hypoxic stress-induced primary human limbal stem (HLS) and corneal epithelial (HCE) cells, resulting in different pathways of cell fate. We found that hypoxic stress induced HLS cell differentiation by down-regulating Plk3 activity at the transcription level, which was opposite to the effect of hypoxic stress on Plk3 activation to elicit HCE cell apoptosis, detected by DNA fragmentation and TUNEL assays. Hypoxic stress-induced increases in c-Jun phosphorylation/activation were not observed in HLS cells because Plk3 expression and activity were suppressed in hypoxia-induced HLS cells. Instead, hypoxic stress-induced HLS cell differentiation was monitored by cell cycle analysis and measured by the decrease and increase in p63 and keratin 12 expression, respectively. Hypoxic stress-induced Plk3 signaling to regulate c-Jun activity, resulting in limbal stem cell differentiation and center epithelial apoptosis, was also found in the corneas of wild-type and Plk3(-/-)-deficient mice. Our results, for the first time, reveal the differential effects of hypoxic stress on Plk3 activity in HLS and HCE cells. Instead of apoptosis, hypoxic stress suppresses Plk3 activity to protect limbal stem cells from death and to allow the process of HLS cell differentiation.

The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice.

Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI) was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI) was also conducted. Results showed that the PSI of the three groups measured during 20-30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***). The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***). Correlation coefficients between PSI and CHI of the three groups were -0.440, -0.369, and -0.537, respectively (p < 0.01 **). PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice.

Osmotic stress-induced phosphorylation of H2AX by polo-like kinase 3 affects cell cycle progression in human corneal epithelial cells.

Increased concentrations of extracellular solutes affect cell function and fate by stimulating cellular responses, such as evoking MAPK cascades, altering cell cycle progression, and causing apoptosis. Our study results here demonstrate that hyperosmotic stress induced H2AX phosphorylation (γH2AX) by an unrevealed kinase cascade involving polo-like kinase 3 (Plk3) in human corneal epithelial (HCE) cells. We found that hyperosmotic stress induced DNA-double strand breaks and increased γH2AX in HCE cells. Phosphorylation of H2AX at serine 139 was catalyzed by hyperosmotic stress-induced activation of Plk3. Plk3 directly interacted with H2AX and was colocalized with γH2AX in the nuclei of hyperosmotic stress-induced cells. Suppression of Plk3 activity by overexpression of a kinase-silencing mutant or by knocking down Plk3 mRNA effectively reduced γH2AX in hyperosmotic stress-induced cells. This was consistent with results that show γH2AX was markedly suppressed in the Plk3(-/-) knock-out mouse corneal epithelial layer in response to hyperosmotic stimulation. The effect of hyperosmotic stress-activated Plk3 and increased γH2AX in cell cycle progression showed an accumulation of G2/M phase, altered population in G1 and S phases, and increased apoptosis. Our results for the first time reveal that hyperosmotic stress-activated Plk3 elicited γH2AX. This Plk3-mediated activation of γH2AX subsequently regulates the cell cycle progression and cell fate.

Epidermal growth factor (EGF)-induced corneal epithelial wound healing through nuclear factor κB subtype-regulated CCCTC binding factor (CTCF) activation.

Epidermal growth factor (EGF) plays an important role in corneal epithelial migration and proliferation to improve the wound healing process. This study aimed to understand the role of NFκB in EGF-induced corneal epithelial wound healing through regulation of CTCF activity, which plays important roles in cell motility and migration to promote wound healing. The effect of NFκB p50 on corneal epithelial wound healing was investigated by comparing the eyes of wild-type and p50 knockout mice. We found that there was a significant retardation in corneal epithelial wound healing in the corneas of p50 knockout mice. Wound closure rates were measured in human corneal epithelial cells transfected with an NFκB activation-sensitive CTCF expression construct to demonstrate the effect of human CTCF expression under the control of EGF-induced NFκB activation on wound healing. EGF stimulation activated NFκB, which directly triggered the expression of the exogenous human CTCF in transfected cells and, subsequently, promoted human corneal epithelial cell motility, migration, and wound healing. Overexpression of CTCF in corneal epithelial cells and mouse corneas significantly enhanced the wound healing process. Furthermore, the effect of overexpressing NFκB p50 in corneal epithelial cells on the promotion of wound healing was abolished by knockdown of CTCF with CTCF-specific shRNA. Thus, a direct regulatory relationship between EGF-induced NFκB p50 and CTCF activation affecting corneal epithelial wound healing has been established, indicating that CTCF is, indeed, a NFκB p50-targeted and effective gene product in the core transcriptional network downstream from the growth factor-induced NFκB signaling pathway.

De-SUMOylation of CCCTC binding factor (CTCF) in hypoxic stress-induced human corneal epithelial cells.

Epigenetic factor CCCTC binding factor (CTCF) plays important roles in the genetic control of cell fate. Previous studies found that CTCF is positively and negatively regulated at the transcriptional level by epidermal growth factor (EGF) and ultraviolet (UV) stimulation, respectively. However, it is unknown whether other stresses modify the CTCF protein. Here, we report that regulation of CTCF by de-SUMOylation is dependent upon hypoxic and oxidative stresses. We found that stimulation of human corneal epithelial cells with hypoxic stress suppressed a high molecular mass form of CTCF (150 kDa), but not a lower molecular weight form of CTCF (130 kDa). Further investigation revealed that the hypoxic stress-suppressed 150-kDa CTCF was a small ubiquitin-related modifier (SUMO)ylated form of the protein. Hypoxic stress-induced de-SUMOylation of human CTCF was associated with lysine 74 and 689 residues, but not to the phosphorylation of CTCF. Overexpression of SENP1 induced de-SUMOylation of CTCF. However, knockdown of SENP1 could not rescue hypoxic stress-induced CTCF de-SUMOylation. Overexpression of SUMO1 and SUMO2 increased SUMOylation of CTCF and partially blocked hypoxic stress-induced CTCF de-SUMOylation, suggesting that free cellular SUMO proteins play roles in regulating hypoxia-induced CTCF de-SUMOylation. In addition, hypoxic stress significantly inhibited PAX6 mRNA and protein expressions by suppression of PAX6-P0 promoter activity. The result was further supported by data showing that knockdown of CTCF significantly enhanced expression of PAX6 and abolished hypoxia-induced suppression of PAX6. Thus, we conclude that hypoxic stress induces de-SUMOylation of CTCF to functionally regulate CTCF activity.

Sumoylation is important for stability, subcellular localization, and transcriptional activity of SALL4, an essential stem cell transcription factor.

SALL4 is a transcription factor that plays a key role in the maintenance and self-renewal of embryonic stem cells and hematopoietic stem cells. Given that little is known about regulation of SALL4, we studied biochemical modifications of SALL4B, a major splicing variant of SALL4, and elucidated their biological function. SALL4B was primarily modified by ubiquitination when it was expressed in both Sf9 and HEK293T cells. A significant fraction of SALL4B was further modified by sumoylation when it was expressed in HEK293T cells. Constitutive SUMO-modification of SALL4B was also detected in Tera-1, a cell line of the teratocarcinoma origin. SALL4B sumoylation was independent of ubiquitination and lysine residues 156, 316, 374, and 401 were essential for sumoylation. Chromatin fraction contained more SUMO-deficient SALL4B. Despite a shorter half-life than the wild-type counterpart, SUMO-deficient SALL4B interacted with OCT4 more efficiently than the wild-type SALL4B. RNAi-mediated silencing of SALL4 expression caused significant down-regulation of both OCT4 and SOX2, which was rescued by ectopic expression of SALL4B but not by SUMO-deficient mutant. Significantly, compared with the wild-type SALL4B, SUMO-deficient mutant exhibited compromised trans-activation or trans-repression activities in reporter gene assays. Combined, our studies reveal sumoylation as a novel form of post-translational modification for regulating the stability, subcellular localization, and transcriptional activity of SALL4.

CTCF mediates effect of insulin on glucagon expression.

Pancreatic islet α-cell development and glucagon production are mainly regulated by Pax6 in the homeobox gene families. However, the molecular mechanism fine-tuning the regulation of these events in α-cell still remains unclear. In ocular cells, Pax6 transcription is regulated by CTCF through its binding to specific sites in Pax6 promoter. In this study, CTCF-mediated regulations of islet α-cell development and glucagon production were investigated in both CTCF transgenic mice and α-TC-1-6 cells. Over-expression of CTCF in transgenic mice affected development of pancreatic islets by significantly suppressing α-cell population in both embryonic and adult pancreases. The effect of CTCF on Pax6 gene expression and subsequently, on pro-glucagon production was however, examined in pancreatic islet α-cells. Over-expression and knock-down of CTCF directly affected Pax6 expression. More importantly, the CTCF binding sites upstream from Pax6 p0 promoter were required for regulating p0 promoter activity in islet α-cells. Stimulation of α-cells with insulin resulted in a significant increase in CTCF expression and a decrease in Pax6 expression, and consequently suppressed pro-glucagon expression. In contrast, these insulin-induced effects were blocked by knockdown of CTCF mRNA with specific siRNA in α-cells. Altogether, our results demonstrated for the first time that CTCF functions as a switch-like molecule between the insulin signaling and the regulations of Pax6 and glucagon expression in pancreatic islet α-cells.

Design and synthesis of 3,4-seco-lupane triterpene derivatives to resist myocardial ischemia-reperfusion injury by inhibiting oxidative stress-mediated mitochondrial dysfunction via the PI3K/AKT/HIF-1α axis.

In this study, 86 new seco-lupane triterpenoid derivatives were designed, synthesized, and characterized, and their protective activities against ischemia-reperfusion injury were investigated in vitro and in vivo. Structure-activity relationship studies revealed that most target compounds could protect cardiomyocytes against hypoxia/reoxygenation-induced injury in vitro, with compound 85 being the most active and exhibiting more potent protective activity than clinical first-line drugs. Furthermore, all thiophene derivatives exhibited stronger protective activity than furan, pyridine, and pyrazine derivatives, and the protective activity gradually increased with the extension of the alkyl chain and changed in the substituent. The data from the in-vitro and in-vivo experiments revealed that compound 85 protected mitochondria from damage by inhibiting excessive production of oxidative stressors, such as intracellular ROS, which in turn inhibited the apoptosis and necrotize of cardiomyocytes and reduced infarct size, thereby protecting normal cardiac function. It was associated with enhanced activation of the PI3K/AKT-mediated HIF-1α signaling pathway. Therefore, compound 85 acts as an oxidative stress inhibitor, blocks ROS production, protects mitochondria and cells from myocardial ischemia/reperfusion (MI/R) injury, and represents an effective new drug for treating MI/R injury.

Hyperosmotic stress-induced ATF-2 activation through Polo-like kinase 3 in human corneal epithelial cells.

Elevated extracellular solute concentration (hyperosmotic stress) perturbs cell function and stimulates cell responses by evoking MAPK cascades and activating AP-1 transcription complex resulting in alterations of gene expression, cell cycle arrest, and apoptosis. The results presented here demonstrate that hyperosmotic stress elicited increases in ATF-2 phosphorylation through a novel Polo-like kinase 3 (Plk3) pathway in human corneal epithelial (HCE) cells. We found in hyperosmotic stress-induced HCE cells that Plk3 transferred to the nuclear compartment and was colocalized with ATF-2 in nuclei. Kinase activity of Plk3 was significantly activated by hyperosmotic stimulation. Further downstream, active Plk3 phosphorylated ATF-2 at the Thr-71 site in vivo and in vitro. Overexpression of Plk3 and its mutants enhanced hyperosmotic stress-induced ATF-2 phosphorylation. In contrast, suppression of Plk3 by knocking down Plk3 mRNA effectively diminished the effect of hyperosmotic stress-induced ATF-2 phosphorylation. The effect of hyperosmotic stress-induced activation of Plk3 on ATF-2 transcription factor function was also examined in CRE reporter-overexpressed HCE cells. Our results for the first time reveal that hyperosmotic stress can activate the Plk3 signaling pathway that subsequently regulates the AP-1 complex by directly phosphorylating ATF-2 independent from the effects of JNK and p38 activation.

Sickness Presenteeism as a Link between Long Working Hours and Employees' Outcomes: Intrinsic and Extrinsic Motivators as Resources.

The aim of this study was to test the flow from long working hours to sickness presenteeism behavior and its outcomes for employees, while integrating intrinsic and extrinsic work value orientations as moderators in the process. We employed a two-wave design with a five-month interval. Data were obtained from 275 employees in Taiwan. The results of latent moderated structural equations (LMS) revealed that long working hours were positively associated with presenteeism, which in turn was negatively related to employees' well-being and job performance. Furthermore, the negative indirect effect of working long hours on job performance via presenteeism was weaker for those with a higher intrinsic work value orientation. The negative indirect effect of working long hours on well-being via presenteeism was weaker for those with a higher extrinsic work value orientation. We demonstrated that the long-term impact of presenteeism behavior could be understood by viewing work value orientations as resource gains to compensate resource depletion in a demanding work context. This resource dynamism is pivotal to realizing the functional or dysfunctional outcomes of presenteeism behavior. Theoretical and managerial implications of the findings for employees' well-being and organizational effectiveness are discussed.

Patient Safety and Staff Well-Being: Organizational Culture as a Resource.

The present study examines the relationship between patient safety culture and health workers' well-being. Applying the conservation of resources mechanism, we tested theory-based hypotheses in a large cross-disciplinary sample (N = 3232) from a Taiwanese metropolitan healthcare system. Using the structural equation modeling technique, we found that patient safety culture was negatively related to staff burnout (ß = -0.74) and could explain 55% of the total variance. We also found that patient safety culture was positively related to staff work-life balance (ß = 0.44) and could explain 19% of the total variance. Furthermore, the above relationships were invariant across groups of diverse staff demography (gender, age, managerial position, and incident reporting) and job characteristics (job role, tenure, and patient contact). Our findings suggest that investing in patient safety culture can be viewed as building an organizational resource, which is beneficial for both improving the care quality and protecting staff well-being. More importantly, the benefits are the same for everyone in the healthcare services.

NF-kappaB subtypes regulate CCCTC binding factor affecting corneal epithelial cell fate.

CCCTC binding factor (CTCF) controls DNA imprinting, insulates important gene expression, and mediates growth factor- and stress-induced cell fate. However, regulatory mechanisms involved in intracellular CTCF activity are largely unknown. In this study, we show that epidermal growth factor (EGF)-induced increase and UV stress-induced decrease in CTCF activities mediate human corneal epithelial cell proliferation and apoptosis, respectively. CTCF is regulated by activation of different NF-kappaB subtypes via stimulation by EGF and UV stress. EGF-induced formation of a p65/p50 heterodimer activated CTCF transcription to promote cellular proliferation. This was accomplished by the heterodimer binding to a kappaB site in the promoter region of CTCF gene. In contrast, UV stress induced formation of a p50/p50 homodimer, which suppressed CTCF expression leading to apoptosis. Thus, CTCF by itself plays a central role in mediating the dichotomous effects of growth factor- and stress-stimulated NF-kappaB activation on cell survival and death. These results suggest that CTCF is a downstream component of the NF-kappaB pathway involved in the core transcriptional network of cell fate.

Regulation of PTEN stability and activity by Plk3.

By studying primary isogenic murine embryonic fibroblasts (MEFs), we have shown that PLK3 null MEFs contain a reduced level of phosphatase and tensin homolog (PTEN) and increased Akt1 activation coupled with decreased GSK3ß activation under normoxia and hypoxia. Purified recombinant Plk3, but not a kinase-defective mutant, efficiently phosphorylates PTEN in vitro. Mass spectrometry identifies threonine 366 and serine 370 as two putative residues that are phosphorylated by Plk3. Immunoblotting using a phosphospecific antibody confirms these sites as Plk3 phosphorylation sites. Moreover, treatment of MEFs with LiCl, an inhibitor of GSK3ß and CK2, only partially suppresses the phosphorylation, suggesting Plk3 as an additional kinase that phosphorylates these sites in vivo. Plk3-targeting mutants of PTEN are expressed at a reduced level in comparison with the wild-type counterpart, which is associated with an enhanced activity of PDK1, an upstream activator of Akt1. Furthermore, the reduced level of PTEN in PLK3 null MEFs is stabilized by treatment with MG132, a proteosome inhibitor. Combined, our study identifies Plk3 as a new player in the regulation of the PI3K/PDK1/Akt signaling axis by phosphorylation and stabilization of PTEN.

Plk3 functions as an essential component of the hypoxia regulatory pathway by direct phosphorylation of HIF-1alpha.

Polo-like kinase 3 (Plk3) plays an important role in the regulation of cell cycle progression and stress responses. Plk3 also has a tumor-suppressing activity as aging PLK3-null mice develop tumors in multiple organs. The growth of highly vascularized tumors in PLK3-null mice suggests a role for Plk3 in angiogenesis and cellular responses to hypoxia. By studying primary isogenic murine embryonic fibroblasts, we tested the hypothesis that Plk3 functions as a component in the hypoxia signaling pathway. PLK3(-/-) murine embryonic fibroblasts contained an enhanced level of HIF-1α under hypoxic conditions. Immunoprecipitation and pulldown analyses revealed that Plk3 physically interacted with HIF-1α under hypoxia. Purified recombinant Plk3, but not a kinase-defective mutant, phosphorylated HIF-1α in vitro, resulting in a major mobility shift. Mass spectrometry identified two unique serine residues that were phosphorylated by Plk3. Moreover, ectopic expression followed by cycloheximide or pulse-chase treatment demonstrated that phospho-mutants exhibited a much longer half-life than the wild-type counterpart, strongly suggesting that Plk3 directly regulates HIF-1α stability in vivo. Combined, our study identifies Plk3 as a new and essential player in the regulation of the hypoxia signaling pathway.