Protein Kinase D Research Articles

Developments in the Discovery and Design of Protein Kinase D Inhibitors

Protein kinase D (PKD) is a serine/threonine kinase family belonging to the Ca2+/calmodulin-dependent protein kinase group. Since its discovery two decades ago, many efforts have been put in elucidating PKD's structure, cellular role and functioning. The PKD family consists of three highly homologous isoforms: PKD1, PKD2 and PKD3. Accumulating cell-signaling research has evidenced that dysregulated PKD plays a crucial role in the pathogenesis of cardiac hypertrophy and several cancer types. These findings led to a broad interest in the design of small-molecule protein kinase D inhibitors. In this review, we present an extensive overview on the past and recent advances in the discovery and development of PKD inhibitors. The focus extends from broad-spectrum kinase inhibitors used in PKD signaling experiments to intentionally developed, bioactive PKD inhibitors. Finally, attention is paid to PKD inhibitors that have been identified as an off-target through large kinome screening panels.

Protein Kinase D2 drives chylomicron‐mediated lipid transport in the intestine and promotes obesity

Lipids are the most energy‐dense components of the diet, and their overconsumption promotes obesity and diabetes. Dietary fat content has been linked to the lipid processing activity by the intestine and its overall capacity to absorb triglycerides (TG). However, the signaling cascades driving intestinal lipid absorption in response to elevated dietary fat are largely unknown. Here, we describe an unexpected role of the protein kinase D2 (PKD2) in lipid homeostasis. We demonstrate that PKD2 activity promotes chylomicron‐mediated TG transfer in enterocytes. PKD2 increases chylomicron size to enhance the TG secretion on the basolateral side of the mouse and human enterocytes, which is associated with decreased abundance of APOA4. PKD2 activation in intestine also correlates positively with circulating TG in obese human patients. Importantly, deletion, inactivation, or inhibition of PKD2 ameliorates high‐fat diet‐induced obesity and diabetes and improves gut microbiota profile in mice. Taken together, our findings suggest that PKD2 represents a key signaling node promoting dietary fat absorption and may serve as an attractive target for the treatment of obesity.

Deficiency in Protein Kinase D Activity exacerbates post‐stroke injuries and impairs functional recovery after ischemic stroke in Mice

Diacylglycerol signaling network is a key mediator of neurovascular injuries after ischemic stroke. As a primary target of diacylglycerol, the family of protein kinase D (PKD) has been implicated in pathological processes involved in ischemia-reperfusion injuries after stroke, however, its in vivo function in the disease has not been thoroughly evaluated. This study aims to investigate whether loss of PKD activity affects ischemic stroke outcomes in mice. Homozygous kinase-dead PKD2 knock-in mice (KI) were obtained by intercrossing mice heterozygous for an inactivating mutation of PKD2S707A/S711A. PKD2 KI and wild type (WT) mice were subjected to 1 h of middle cerebral artery occlusion (MCAO) and 24 h of reperfusion. Infarct volumes and neurological scores were measured and compared between KI and WT mice after reperfusion. To gain insights into the mechanisms of PKD signaling, expression and activity of PKD isoforms and their downstream targets were evaluated by quantitative real-time PCR (qRT-PCR) and Western blot. Our data showed that catalytic deficiency of PKD aggravated post-stroke brain infarction and edema, correlating to worsened neurological scores in mice. Cellular analysis showed that all three PKD isoforms were expressed in mouse neuronal cells and activated in response to in vitro ischemia, correlating to changes of several downstream signaling events, supporting their involvement in pathological processes of neuronal injury. Our findings support a neuroprotective role of PKD in ischemic stroke and suggest potential therapeutic targets for neuroprotection.

A PKD-MFF signaling axis couples mitochondrial fission to mitotic progression.

Mitochondria are highly dynamic organelles subjected to fission and fusion events. During mitosis, mitochondrial fission ensures equal distribution of mitochondria to daughter cells. If and how this process can actively drive mitotic progression remains largely unknown. Here, we discover a pathway linking mitochondrial fission to mitotic progression in mammalian cells. The mitochondrial fission factor (MFF), the main mitochondrial receptor for the Dynamin-related protein 1 (DRP1), is directly phosphorylated by Protein Kinase D (PKD) specifically during mitosis. PKD-dependent MFF phosphorylation is required and sufficient for mitochondrial fission in mitotic but not in interphasic cells. Phosphorylation of MFF is crucial for chromosome segregation and promotes cell survival by inhibiting adaptation of the mitotic checkpoint. Thus, PKD/MFF-dependent mitochondrial fission is critical for the maintenance of genome integrity during cell division.

Protein kinase D, ubiquitin and proteasome pathways are involved in adenosine receptor-stimulated NR4A expression in myeloid cells

Adenosine is a purine nucleoside pivotal for homeostasis in cells and tissues. Stimulation of the adenosine receptors (AR) has been shown to regulate the nuclear orphan receptor 4A (NR4A1-3) family, resulting in attenuation of hyper-inflammatory responses in myeloid cells. The NR4A1-3 orphan receptors are early immediate response genes and transcriptional regulators of cell and tissue homeostasis. The signal transduction and transcriptional mechanism(s) of how AR-stimulation promotes NR4A expression in myeloid cells is unknown and is the focus of this study. We confirm that adenosine and the stable analogue, 5′-N-Ethylcarboxamidoadenosine (NECA), enhance NR4A1-3 expression in THP-1 cells. Pharmacological approaches identified that protein kinase D (PKD) mediates AR-stimulated NR4A expression in myeloid cells and reveals no involvement of PKA nor PKC. The role of NF-κB, a principal regulator of NR4A expression in myeloid cells, was examined as a possible transcriptional regulator downstream of PKD. Utilising BAY11-7082 and MG-132, inhibitors of the respective ubiquitin and proteasome pathways essential for NF-κB activation, suggested a prospective role for NF-κB, or more specifically signalling via IKKα/β. However, biological interventional studies using overexpression of IκBα in myeloid cells and MEF cells lacking IKKα and IKKβ (IKKα/β−/-) revealed the NF-κB pathway is not utilised in mediating AR-stimulated NR4A expression. Thus, this study contributes mechanistic insight into how AR signalling modulates the expression of NR4A receptors, pivotal regulators of inflammatory responses in myeloid cells.

Npas4 impairs fear memory via phosphorylated HDAC5 induced by CGRP administration in mice

The relationships among neuropeptide, calcitonin gene-related peptide (CGRP), and memory formation remain unclear. Here, we showed that the intracerebroventricular administration of CGRP impaired the traumatic fear memories, in a widely studied animal model of post-traumatic stress disorder. We found that CGRP administration suppressed fear memory by increasing neuronal PAS domain protein 4 (Npas4), phosphorylated histone deacetylase 5 (HDAC5), and protein kinase D (PKD). We also discovered that Npas4 knockdown inhibited CGRP-mediated fear memory. CGRP decreased the binding between HDAC5 and the Npas4 enhancer site and increased the binding between acetylated histone H3 and the Npas4 enhancer site. The pharmacological inhibition or knockdown of PKD attenuated the CGRP-mediated impairment of fear memory and the increased phosphorylation of HDAC5 and Npas4 expression. Our findings demonstrated that the CGRP-PKD pathway was associated with the histone H3 acetylation-Npas4 pathway. These results suggested a novel function for CGRP on fear memory, through epigenetic regulation.

Multifaceted Functions of Protein Kinase D in Pathological Processes and Human Diseases.

Protein kinase D (PKD) is a family of serine/threonine protein kinases operating in the signaling network of the second messenger diacylglycerol. The three family members, PKD1, PKD2, and PKD3, are activated by a variety of extracellular stimuli and transduce cell signals affecting many aspects of basic cell functions including secretion, migration, proliferation, survival, angiogenesis, and immune response. Dysregulation of PKD in expression and activity has been detected in many human diseases. Further loss- or gain-of-function studies at cellular levels and in animal models provide strong support for crucial roles of PKD in many pathological conditions, including cancer, metabolic disorders, cardiac diseases, central nervous system disorders, inflammatory diseases, and immune dysregulation. Complexity in enzymatic regulation and function is evident as PKD isoforms may act differently in different biological systems and disease models, and understanding the molecular mechanisms underlying these differences and their biological significance in vivo is essential for the development of safer and more effective PKD-targeted therapies. In this review, to provide a global understanding of PKD function, we present an overview of the PKD family in several major human diseases with more focus on cancer-associated biological processes.

PKD3 promotes metastasis and growth of oral squamous cell carcinoma through positive feedback regulation with PD-L1 and activation of ERK-STAT1/3-EMT signalling

Oral squamous cell carcinoma (OSCC) has a high incidence of metastasis. Tumour immunotherapy targeting PD-L1 or PD-1 has been revolutionary; however, only a few patients with OSCC respond to this treatment. Therefore, it is essential to gain insights into the molecular mechanisms underlying the growth and metastasis of OSCC. In this study, we analysed the expression levels of protein kinase D3 (PKD3) and PD-L1 and their correlation with the expression of mesenchymal and epithelial markers. We found that the expression of PKD3 and PD-L1 in OSCC cells and tissues was significantly increased, which correlated positively with that of mesenchymal markers but negatively with that of epithelial markers. Silencing PKD3 significantly inhibited the growth, metastasis and invasion of OSCC cells, while its overexpression promoted these processes. Our further analyses revealed that there was positive feedback regulation between PKD3 and PD-L1, which could drive EMT of OSCC cells via the ERK/STAT1/3 pathway, thereby promoting tumour growth and metastasis. Furthermore, silencing PKD3 significantly inhibited the expression of PD-L1, and lymph node metastasis of OSCC was investigated with a mouse footpad xenograft model. Thus, our findings provide a theoretical basis for targeting PKD3 as an alternative method to block EMT for regulating PD-L1 expression and inhibiting OSCC growth and metastasis.

Potential Role of Curcumin and Its Nanoformulations to Treat Various Types of Cancers.

Cancer is a major burden of disease globally. Each year, tens of millions of people are diagnosed with cancer worldwide, and more than half of the patients eventually die from it. Significant advances have been noticed in cancer treatment, but the mortality and incidence rates of cancers are still high. Thus, there is a growing research interest in developing more effective and less toxic cancer treatment approaches. Curcumin (CUR), the major active component of turmeric (Curcuma longa L.), has gained great research interest as an antioxidant, anticancer, and anti-inflammatory agent. This natural compound shows its anticancer effect through several pathways including interfering with multiple cellular mechanisms and inhibiting/inducing the generation of multiple cytokines, enzymes, or growth factors including IκB kinase β (IκKβ), tumor necrosis factor-alpha (TNF-α), signal transducer, and activator of transcription 3 (STAT3), cyclooxygenase II (COX-2), protein kinase D1 (PKD1), nuclear factor-kappa B (NF-κB), epidermal growth factor, and mitogen-activated protein kinase (MAPK). Interestingly, the anticancer activity of CUR has been limited primarily due to its poor water solubility, which can lead to low chemical stability, low oral bioavailability, and low cellular uptake. Delivering drugs at a controlled rate, slow delivery, and targeted delivery are other very attractive methods and have been pursued vigorously. Multiple CUR nanoformulations have also been developed so far to ameliorate solubility and bioavailability of CUR and to provide protection to CUR against hydrolysis inactivation. In this review, we have summarized the anticancer activity of CUR against several cancers, for example, gastrointestinal, head and neck, brain, pancreatic, colorectal, breast, and prostate cancers. In addition, we have also focused on the findings obtained from multiple experimental and clinical studies regarding the anticancer effect of CUR in animal models, human subjects, and cancer cell lines.

Adipose-specific knockout of Protein Kinase D1 suppresses de novo lipogenesis in mice via SREBP1c-dependent signaling

Having healthy adipose tissue is essential for metabolic health, as excessive adipose tissue in the body can cause its dysregulation and driving chronic metabolic diseases. Protein kinase D1 (PKD1) is considered to be a key kinase in signal transduction, which regulates multiple cellular functions, but its physiological functions in adipose are still not fully understood. This study aimed at elucidating the function of adipocyte PKD1 on lipogenesis. From RNA-Sequencing data, we found that the fatty acid biosynthesis pathway in white adipose tissue lacking PKD1 was significantly affected. Critical rate-limiting enzymes for de novo lipogenesis in adipocytes, such as FASN, ACCα, and SCD1, were significantly repressed after deleting PKD1 in vivo and in vitro. Further studies revealed that blockade of PKD1 significantly increased phosphorylation of SREBP1c at serine 372 site. Co-immunoprecipitation analysis showed that PKD1 interacts with SREBP1c in vitro and in vivo. Importantly, overexpression of SREBP1c reversed the inhibition of FASN and ACCα expression caused by PKD1 silencing. Together, adipocyte PKD1 promotes de novo lipogenesis via SREBP1c-dependent manner in visceral white adipose tissue and might provide a new target for the development of anti-obesity therapies.

Phosphoproteomic identification of vasopressin-regulated protein kinases in collecting duct cells.

The peptide hormone vasopressin regulates water transport in the renal collecting duct largely via the V2 receptor, which triggers a cAMP-mediated activation of a PKA-dependent signalling network. The protein kinases downstream from PKA have not been fully identified or mapped to regulated phosphoproteins. We carried out systems-level analysis of large-scale phosphoproteomic data quantifying vasopressin-induced changes in phosphorylation in aquaporin-2-expressing cultured collecting duct (mpkCCD) cells. Quantification was done using stable isotope labelling (SILAC method). Six hundred forty phosphopeptides were quantified. Stringent statistical analysis identified significant changes in response to vasopressin in 429 of these phosphopeptides. The corresponding phosphoproteins were mapped to known vasopressin-regulated cellular processes. The vasopressin-regulated sites were classified according to the sequences surrounding the phosphorylated amino acids giving 11 groups. Among the vasopressin-regulated phosphoproteins were 25 distinct protein kinases. Among these, six plus PKA appeared to account for phosphorylation of about 81% of the 313 vasopressin-regulated phosphorylation sites. The six downstream kinases were salt-inducible kinase 2 (Sik2), cyclin-dependent kinase 18 (Cdk18), calmodulin-dependent kinase kinase 2 (Camkk2), protein kinase D2 (Prkd2), mitogen-activated kinase 3 (Mapk3) and myosin light chain kinase (Mylk). In V2 receptor-mediated signalling, PKA is at the head of a complex network that includes at least six downstream vasopressin-regulated protein kinases that are prime targets for future study. The extensive phosphoproteomic data reported in this study are provided as a web-based data resource for future studies of GPCRs.

The protein kinase D1-mediated inflammatory pathway is involved in olanzapine-induced impairment of skeletal muscle insulin signaling in rats

AimsSkeletal muscle insulin resistance (SMIR) contributes to the metabolic syndrome. Mounting evidence has demonstrated that the second generation antipsychotic olanzapine causes SMIR. The present study sought to investigate the molecular mechanisms underlying olanzapine-induced SMIR. Main methodsMale rats were given olanzapine (5 mg/kg, by a gavage method) for consecutive eight weeks. Plasma glucose and insulin concentrations were determined enzymatically or by ELISA. Gene/protein expression was analyzed by Real-Time PCR, Western blot and/or immunohistochemistry. Key findingsOlanzapine increased fasting plasma insulin concentration, and decreased glucose clearance during insulin tolerance test in rats. In skeletal muscle, it decreased protein expression of membrane glucose transporter (GLUT) 4, the ratio of membrane to total GLUT4, and total insulin receptor substrate 1 (IRS1). However, it increased protein phosphorylation of Ser307 in IRS1, Y607 in phosphoinositide 3-kinase p85α and Ser307 in AKT. These results indicate olanzapine-induced impairment of skeletal muscle insulin signaling. Mechanistically, olanzapine upregulated mRNA expression of TNFα, IL6 and IL1β, and protein phosphorylation of both IκB kinase (IKK)α/β and nuclear factor (NF)κB p65. Furthermore, it increased protein phosphorylation of Ser485/491 in AMPKα2, whereas it decreased AMPKα2 activity. More importantly, both Western blot and immunohistochemical analyses revealed that olanzapine increased protein phosphorylation of Ser744/748 in protein kinase D1 (PKD1). SignificanceThe present results suggest that the PKD1-mediated inflammatory pathway is involved in olanzapine-induced impairment of skeletal muscle insulin signaling in rats. Our findings may go new insight into the mechanisms underlying olanzapine-induced SMIR.

Activation of Tripartite Motif Containing 63 Expression by Transcription Factor EB and Transcription Factor Binding to Immunoglobulin Heavy Chain Enhancer 3 Is Regulated by Protein Kinase D and Class IIa Histone Deacetylases.

RationaleThe ubiquitin–proteasome system (UPS) is responsible for skeletal muscle atrophy. We showed earlier that the transcription factor EB (TFEB) plays a role by increasing E3 ubiquitin ligase muscle really interesting new gene-finger 1(MuRF1)/tripartite motif-containing 63 (TRIM63) expression. MuRF 1 ubiquitinates structural proteins and mediates their UPS-dependent degradation. We now investigated how TFEB-mediated TRIM63 expression is regulated.ObjectiveBecause protein kinase D1 (PKD1), histone deacetylase 5 (HDAC5), and TFEB belong to respective families with close structural, regulatory, and functional properties, we hypothesized that these families comprise a network regulating TRIM63 expression.Methods and ResultsWe found that TFEB and transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3) activate TRIM63 expression. The class IIa HDACs HDAC4, HDAC5, and HDAC7 inhibited this activity. Furthermore, we could map the HDAC5 and TFE3 physical interaction. PKD1, PKD2, and PKD3 reversed the inhibitory effect of all tested class IIa HDACs toward TFEB and TFE3. PKD1 mediated nuclear export of all HDACs and lifted TFEB and TFE3 repression. We also mapped the PKD2 and HDAC5 interaction. We found that the inhibitory effect of PKD1 and PKD2 toward HDAC4, HDAC5, and HDAC7 was mediated by their phosphorylation and 14-3-3 mediated nuclear export.ConclusionTFEB and TFE3 activate TRIM63 expression. Both transcription factors are controlled by HDAC4, HDAC5, HDAC7, and all PKD-family members. We propose that the multilevel PKD/HDAC/TFEB/TFE3 network tightly controls TRIM63 expression.

Inhibition Lysosomal Degradation of Clusterin by Protein Kinase D3 Promotes Triple-Negative Breast Cancer Tumor Growth.

Triple negative breast cancer (TNBC), with its lack of targeted therapies, shows the worst mortality rate among all breast cancer subtypes. Clusterin (CLU) is implicated to play important oncogenic roles in cancer via promoting various downstream oncogenic pathways. Here, protein kinase D3 (PRKD3) is defined to be a key regulator of CLU in promoting TNBC tumor growth. Mechanically, PRKD3 with kinase activity binding to CLU is critical for CLU protein stability via inhibiting CLU's lysosomal distribution and degradation. CLU and PRKD3 protein level are significantly elevated and positively correlated in collected TNBC tumor samples. CLU silencer (OGX‐011) and PRKDs inhibitor (CRT0066101) can both result in impressive tumor growth suppression in vitro and in vivo, suggesting targeting CLU and its key regulator‐PRKD3 are promisingly efficient against TNBC. Finally, secreted CLU (sCLU) is found to be elevated in serums from TNBC patients and reduced in serum from TNBC murine models post OGX‐011 and/or CRT0066101 treatment, suggesting serum sCLU is a promising blood‐based biomarker for clinical management of TNBC. Taken together, this study provides a thorough molecular basis as well as preclinical evidences for targeting CLU pathway as a new promising strategy against TNBC via revealing PRKD3 as the key regulator of CLU in TNBC.

The oncogenic role of protein kinase D3 in cancer.

Protein kinase D3 (PRKD3), a serine/threonine kinase, belongs to protein kinase D family, which contains three members: PRKD1, PRKD2, and PRKD3. PRKD3 is activated by many stimuli including phorbol esters, and G-protein-coupled receptor agonists. PRKD3 promotes cancer cell proliferation, growth, migration, and invasion in various tumor types including colorectal, gastric, hepatic, prostate, and breast cancer. Accumulating data supports that PRKD3 is a promising therapeutic target for treatment of cancer. This review discusses the functions and mechanisms of PRKD3 in promoting tumorigenesis and tumor progression of various tumor types as well as the latest developments of small-molecule inhibitors selection for PRKD/PRKD3.

Dysfunctional EGFR and oxidative stress-induced PKD1 signaling drive formation of DCLK1+ pancreatic stem cells

SummaryDoublecortin-like kinase 1 (DCLK1)-positive pancreatic cancer stem cells develop at a precancerous stage and may contribute to the lack of efficacy of pancreatic cancer therapy. Although PanIN cells express oncogenic KRas and have an increased activity of epidermal growth factor receptor (EGFR), we demonstrate that, in DCLK1+ PanIN cells, EGFR signaling is not propagated to the nucleus. Mimicking blockage of EGFR with erlotinib in PanIN organoid culture or in p48cre;KrasG12D mice led to a significant increase in DCLK1+ PanIN cells. As a mechanism of how EGFR inhibition leads to formation of DCLK1+ cells, we identify an increase in hydrogen peroxide contributing to activation of Protein Kinase D1 (PKD1). Active PKD1 then drives stemness and abundance of DCLK1+ cells in lesions. Our data suggest a signaling mechanism that leads to the development of DCLK1+ pancreatic cancer stem cells, which can be exploited to target this population in potential therapeutic approaches.

Deciphering Cellular Signals in Adult Mouse Sinoatrial Node Cells

The flexibility of manipulating the mouse genome makes cells from this species an ideal model to study cellular signals that control organ function. Genetically-modified mice provide opportunities to decipher how pacemaking sinoatrial node (SAN) cells are regulated by several second messengers and signaling molecules. However, detailed information on the spatiotemporal dynamics of these signaling events in adult mouse SAN cells has been limited due to the challenge of visualizing them in live cells. Here, a method is described for culturing and immediate infection of adult mouse SAN cells with genetically-encoded FRET-based biosensors to examine cellular dynamics of signaling events. SAN cells maintained in culture media containing blebbistatin or (S)-nitro-blebbistatin retain their elongated morphology and action potential (AP) waveform for up to 40 hours. The culturing condition does not change β-adrenergic-mediated cAMP signal as determined in freshly dissociated and cultured SAN cells from a cardiac-specific cAMP reporter mouse. SAN cells expressing cAMP sensors in different cellular compartments show distinct β-adrenergic-mediated cAMP pools. Examination of cyclic GMP (cGMP), protein kinase A (PKA), Ca2+/CaM kinase II (CaMKII) and protein kinase D (PKD) activity with specific FRET biosensors also show unique responses to different stimuli in SAN cells. Isolation and culture of SAN cells from heart failure mice reveal a decrease in cAMP and cGMP signaling. Thus, a reliable and efficient method for culturing adult mouse SAN cells has been developed to facilitate studies of signaling network dynamics during physiological and pathological conditions.

Protein kinase D participates in cardiomyocyte hypertrophy by regulating extracellular signal-regulated and myocyte enhancer factor 2D

ObjectiveCardiomyocyte hypertrophy is an important feature of hypertension. However, its molecular underpinnings, especially the signaling cascades, remain unclear. Here we hypothesized that a protein kinase D (PKD)-dependent extracellular signal-regulated kinase 5 (ERK5) pathway was able to regulate downstream myocyte enhancer factor 2D (MEF2D), affecting prohypertrophic responses to angiotensin II (Ang II). MethodsNeonatal rat cardiomyocytes from 2- to 3-day-old Sprague-Dawley rats were prepared and Western blot, real-time quantitative PCR and immunofluorescence staining were used to assess the activation and translocation of pathway signaling molecules. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression and [3H]-leucine (Leu) incorporation were measured to determine cell hypertrophy. ResultsElevated levels of phosphorylated PKD (p-PKD) and ERK5 (p-ERK5) were observed in cardiomyocytes stimulated with Ang II, while silencing protein kinase C epsilon (PKCɛ) resulted in significantly lower levels of p-PKD. Furthermore, Ang II-induced ERK5 activated translocation was mediated by the PKD pathway. Consequently, inhibiting PKCɛ, PKD and ERK5 by siRNA significantly attenuated Ang II-induced MEF2D activation, ANP and BNP mRNA expression, and [3H]-Leu incorporation. ConclusionsOur studies are the first to show that the PKCɛ/PKD/ERK5/MEF2D pathway plays an important role in the cardiomyocyte hypertrophy response to Ang II.

Higher tumor protein kinase D1 correlates with increased tumor size, BCLC stage, CA199 level, AFP level and worse overall survival in hepatocellular carcinoma patients

ObjectiveHepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Protein kinase D1 (PKD1) is recognized as a key regulator in the progression in several solid cancers, while its clinical role in HCC is unclear. This study aimed to evaluate the correlation of PKD1 with clinical features and prognosis in HCC patients. MethodsA total of 218 HCC patients who underwent resection were retrospectively enrolled. PKD1 expression in tumor (N = 218) and adjacent (N = 110) tissues was detected by immunohistochemical staining, scored by a semi-quantitative scoring method ranging from 0 to 12, and further classified as PKD1-, PKD1+, PKD1++ and PKD1+++ for analysis. Meanwhile, patients’ clinical features and survival data were acquired from the database. ResultsPKD1 was elevated in tumor tissues compared with adjacent tissues. Meanwhile, higher tumor PKD1 was correlated with elevated tumor size, Barcelona Clinic Liver Cancer (BCLC) stage, carbohydrate antigen 199 (CA199) level and alpha fetoprotein (AFP) level; while no correlation was found in tumor PKD1 with patients’ basic features or liver function indexes. Moreover, higher tumor PKD1 was correlated with worse overall survival (OS) in HCC patients, then further validated as an independent predictive factor for worse OS by multivariate Cox’s regression model analysis. Additionally, in Child-Pugh stage A, Child-Pugh stage B, BCLC stage 0/A, and BCLC stage B subgroups, higher tumor PKD1 was also correlated with worse OS. ConclusionHigher PKD1 in tumor tissues correlates with elevated BCLC stage, bigger tumor size, increased CA199 level, higher AFP level and worse OS in HCC patients.

Expression Level of Protein Kinase D in Oral Squamous Cell Carcinoma with Diverse Differentiation

This study aimed to investigate the expression level of protein kinase D (PKD) in oral squamous cell carcinoma (OSCC) and its relationship with differentiation of OSCC. Sample was collected from 10 healthy control subjects and 40 OSCC confirmed by histopathological diagnosis, and the immunohistochemical staining was adopted to detect the expression of PKDs in OSCC tissues. The proportion of stained cell and staining intensity were evaluated to get a score, which used to analyze the difference among PKD1, PKD2 and PKD3 in various differentiation OSCC tissues. The correlations between the staining score of PKDs and differentiation of OSCC were further analyzed. PKD1 and PKD3 were high expression in OSCC tissues. There were statistical significance among the staining score of PKD1, PKD2 and PKD3 in various differentiation OSCC tissues ( P<0.001). In addition, there was a significantly negative correlation between the staining score of PKD1 and PKD2 with the differentiation of OSCC ( r=-0.574, -0.341, P<0.001). In OSCC tissues with different degree of differentiation, there might be some differences among PKDs which play a major role. The expression of PKD1 and PKD2 was correlated with the differentiation of OSCC, the poor differentiation of OSCC, the higher expression of PKD1 and PKD2.