Protein kinase D1 regulates metabolic switch in pancreatic cancer via modulation of mTORC1

RBM47 promotes cell proliferation and immune evasion by upregulating PDIA6: a novel mechanism of pancreatic cancer progression

BACKGROUND

Pancreatic cancer (PC) is a lethal malignancy characterized by poor prognosis and high mortality. We found the highly expressed RNA-binding motif protein 47 (RBM47) in PC progression. The RBM47 expression was negatively correlated with natural killer (NK) cell infiltrate in PC. Moreover, RBM47 was predicted to bind to the 3'-UTR region of Protein Disulfide Isomerase Family A Member 6 (PDIA6), an oncogene of the development of PC. Therefore, we supposed that RBM47 might affect PC progression by regulating PDIA6.

METHODS

Bioinformatics analysis was performed to screen the candidate gene affecting PC progression using public databases. Loss- and gain-of-function effects of RBM47 on cell proliferation, tumor growth, and immune evasion were determined by CCK-8, EdU incorporation, colony formation assays, the xenogeneic tumor model, and co-culture system of PC and NK-92 cells. RBM47-RNA immunoprecipitation (RIP) followed by PCR and dual luciferase reporter assay were used to detect whether RBM47 could interact with the PDIA6 mRNA and how RBM47 would regulate the transcriptional activity of PDIA6, respectively. Simultaneous overexpression of PDIA6 in RBM47 knockdown PC cells was conducted to clarify whether PDIA6 would mediated effects of RBM47. Given the important role of cellular metabolism in cells proliferation and immune evasion, PC cells with RBM47 knockdown were subjected to metabolomics analysis to further investigate how RBM47 regulate PC progression.

RESULTS

RBM47 overexpression drove PC progression by promoting cell proliferation and xenografted tumor growth. Consistently, our results showed that RBM47 overexpression weakened sensitivity of PC cells to cytotoxic NK cells. However, RBM47 knockdown exhibited the opposite effects on proliferation and immune evasion of PC cells. RBM47 was able to bind to the 3'-UTR region of PDIA6, maintained PDIA6 mRNA stability, and increased the PDIA6 expression in PC cells. Rescue experiments supported that PDIA6 overexpression reversed the suppressing effects of RBM47 knockdown on cell proliferation and immune evasion. RBM47 knockdown significantly changed metabolites of PC cells.

CONCLUSIONS

In summary, our findings demonstrate that RBM47 contributes to PC progression, which might be mediated by the upregulated PDIA6 expression and the altered cellular metabolites in PC cells, offering a potential therapeutic target for PC treatment.

Hsa_circ_0007590/PTBP1 complex reprograms glucose metabolism by reducing the stability of m6A-modified PTEN mRNA in pancreatic ductal adenocarcinoma

The role of circular RNAs (circRNAs) in glucose metabolism in pancreatic duct adenocarcinoma (PDAC) remains elusive. Through RNA sequencing of cells cultured under conditions of glucose deprivation, we identified hsa_circ_0007590. Sanger sequencing and RNase R and Act D treatments were performed to confirm the circular RNA features of hsa_circ_0007590. RNA in situ hybridization (RNA-ISH) and quantitative reverse transcription PCR (qRT-PCR) were used to estimate hsa_circ_0007590 expression in PDAC clinical specimens and cell lines. hsa_circ_0007590 expression was higher in PDAC patients and closely related to the clinicopathological characteristics of the disease. Cytoplasm‒nuclear fractionation and FISH assays demonstrated that hsa_circ_0007590 was located in the nucleus. Gain-of-function and loss-of-function assays were performed to assess the biological behaviors of PDAC cells. Seahorse XF assays were performed to validate the Warburg effect. hsa_circ_0007590 facilitated the proliferation, migration, and invasion of PDAC cells and promoted the Warburg effect. Mass spectrometry, RNA pulldown, RNA immunoprecipitation (RIP), RNA m6A quantification, m6A dot blot, MeRIP, and Western blotting were conducted to investigate the detailed mechanism through which hsa_circ_0007590 produces these effects. Mechanistically, hsa_circ_0007590 targeted PTBP1 and increased the expression of the m6A reader protein YTHDF2, leading to PTEN mRNA degradation and PI3K/AKT/mTOR pathway activation. Overall, hsa_circ_0007590, which targets PTBP1, reprograms glucose metabolism by attenuating the stability of m6A-modified PTEN mRNA and holds potential promise as a therapeutic target for PDAC.

Protein kinase D1 - A targetable mediator of pancreatic cancer development

Members of the Protein kinase D (PKD) kinase family each play important cell-specific roles in the regulation of normal pancreas functions. In pancreatic diseases PKD1 is the most widely characterized isoform with roles in pancreatitis and in induction of pancreatic cancer and its progression. PKD1 expression and activation increases in pancreatic acinar cells through macrophage secreted factors, Kirsten rat sarcoma viral oncogene homolog (KRAS) signaling, and reactive oxygen species (ROS), driving the formation of precancerous lesions. In precancerous lesions PKD1 regulates cell survival, growth, senescence, and generation of doublecortin like kinase 1 (DCLK1)-positive cancer stem cells (CSCs). Within tumors, regulation by PKD1 includes chemoresistance, apoptosis, proliferation, CSC features, and the Warburg effect. Thus, PKD1 plays a critical role throughout pancreatic disease initiation and progression.

The role of PKC and PKD in CXCL12 and CXCL13 directed malignant melanoma and acute monocytic leukemic cancer cell migration

Cancer metastasis is the leading cause of cancer related mortality. Chemokine receptors and proteins in their downstream signalling axis represent desirable therapeutic targets for the prevention of metastasis. Despite this, current therapeutics have experienced limited success in clinical trials due to a lack of insight into the downstream signalling pathway of specific chemokine receptor cascades in different tumours. In this study, we investigated the role of protein kinase C (PKC) and protein kinase D (PKD) in CXCL12 and CXCL13 stimulated SK-MEL-28 (malignant melanoma) and THP-1 (acute monocytic leukaemia) cell migration. While PKC and PKD had no active role in CXCL12 or CXCL13 stimulated THP-1 cell migration, PKC and PKD inhibition reduced CXCL12 stimulated migration and caused profound effects upon the cytoskeleton of SK-MEL-28 cells. Furthermore, only PKC and not PKD inhibition reduced CXCL13 stimulated migration in SK-MEL-28 cells however PKC inhibition failed to stimulate any changes to the actin cytoskeleton. These findings indicate that PKC inhibitors would be a useful therapeutic for the prevention of both CXCL12 and CXCL13 stimulated migration and PKD inhibitors for CXCL12 stimulated migration in malignant melanoma.

Does β-Hydroxy-β-Methylbutyrate Have Any Potential to Support the Treatment of Duchenne Muscular Dystrophy in Humans and Animals?

Skeletal muscle is the protein reservoir of our body and an important regulator of glucose and lipid homeostasis. The dystrophin gene is the largest gene and has a key role in skeletal muscle construction and function. Mutations in the dystrophin gene cause Duchenne and Becker muscular dystrophy in humans, mice, dogs, and cats. Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular condition causing progressive muscle weakness and premature death. β-hydroxy β-methylbutyrate (HMB) prevents deleterious muscle responses under pathological conditions, including tumor and chronic steroid therapy-related muscle losses. The use of HMB as a dietary supplement allows for increasing lean weight gain; has a positive immunostimulatory effect; is associated with decreased mortality; and attenuates sarcopenia in elderly animals and individuals. This study aimed to identify some genes, metabolic pathways, and biological processes which are common for DMD and HMB based on existing literature and then discuss the consequences of that interaction.

Potential role for protein kinase D inhibitors in prostate cancer

Protein kinase D (PrKD), a novel serine-threonine kinase, belongs to a family of calcium calmodulin kinases that consists of three isoforms: PrKD1, PrKD2, and PrKD3. The PrKD isoforms play a major role in pathologic processes such as cardiac hypertrophy and cancer progression. The charter member of the family, PrKD1, is the most extensively studied isoform. PrKD play a dual role as both a proto-oncogene and a tumor suppressor depending on the cellular context. The duplicity of PrKD can be highlighted in advanced prostate cancer (PCa) where expression of PrKD1 is suppressed whereas the expressions of PrKD2 and PrKD3 are upregulated to aid in cancer progression. As understanding of the PrKD signaling pathways has been better elucidated, interest has been garnered in the development of PrKD inhibitors. The broad-spectrum kinase inhibitor staurosporine acts as a potent PrKD inhibitor and is the most well-known; however, several other novel and more specific PrKD inhibitors have been developed over the last two decades. While there is tremendous potential for PrKD inhibitors to be used in a clinical setting, none has progressed beyond preclinical trials due to a variety of challenges. In this review, we focus on PrKD signaling in PCa and the potential role of PrKD inhibitors therein, and explore the possible clinical outcomes based on known function and expression of PrKD isoforms at different stages of PCa.

Integrated bioinformatics data analysis reveals a risk signature and PKD1 induced progression in endometrial cancer patients with postmenopausal status

Background: Endometrial cancer (EC) is one of the most common type of female genital malignancies. The purpose of the present study was to reveal the underlying oncogene and mechanism that played a pivotal role in postmenopausal EC patients.

Methods: Weighted gene co-expression network analysis (WGCNA) was conducted using the microarray dataset and clinical data of EC patients from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases to identify significant gene modules and hub genes associated with postmenopausal status in EC patients. LASSO regression was conducted to build and validate the risk model. Finally, expression of hub gene was validated in pre- and post-menopausal EC patients in our center.

Results: 1240 common genes were used to construct the WGCNA model. According to the WGCNA results, we identified a brown module with 471 genes which was significantly associated with postmenopausal status in EC patients. Furthermore, we constructed an 11-gene risk signature to predict the overall survival of EC patients. The Kaplan–Meier curve and area under the ROC curve (AUC) of this model showed high accuracy in prediction. We also validate the risk model in patients in our center and it also has a high accuracy. Among the 11 genes, PKD1 was recognized as a potential biomarker in the progression of EC patients with postmenopausal status.

Conclusion: Taken together, we uncovered a common PKD1-mediated mechanism underlying postmenopausal EC patients’ progression by integrated analyses. This finding may improve targeted therapy for EC patients.

Golgi Complex: A Signaling Hub in Cancer

The Golgi Complex is the central hub in the endomembrane system and serves not only as a biosynthetic and processing center but also as a trafficking and sorting station for glycoproteins and lipids. In addition, it is an active signaling hub involved in the regulation of multiple cellular processes, including cell polarity, motility, growth, autophagy, apoptosis, inflammation, DNA repair and stress responses. As such, the dysregulation of the Golgi Complex-centered signaling cascades contributes to the onset of several pathological conditions, including cancer. This review summarizes the current knowledge on the signaling pathways regulated by the Golgi Complex and implicated in promoting cancer hallmarks and tumor progression.

Steviol Represses Glucose Metabolism and Translation Initiation in Pancreatic Cancer Cells

Pancreatic cancer has the worst prognosis and lowest survival rate among all cancers. Pancreatic cancer cells are highly metabolically active and typically reprogrammed for aberrant glucose metabolism; thus they respond poorly to therapeutic modalities. It is highly imperative to understand mechanisms that are responsible for high glucose metabolism and identify natural/synthetic agents that can repress glucose metabolic machinery in pancreatic cancer cells, to improve the therapeutic outcomes/management of pancreatic cancer patients. We have identified a glycoside, steviol that effectively represses glucose consumption in pancreatic cancer cells via the inhibition of the translation initiation machinery of the molecular components. Herein, we report that steviol effectively inhibits the glucose uptake and lactate production in pancreatic cancer cells (AsPC1 and HPAF-II). The growth, colonization, and invasion characteristics of pancreatic cancer cells were also determined by in vitro functional assay. Steviol treatment also inhibited the tumorigenic and metastatic potential of human pancreatic cancer cells by inducing apoptosis and cell cycle arrest in the G1/M phase. The metabolic shift by steviol was mediated through the repression of the phosphorylation of mTOR and translation initiation proteins (4E-BP1, eIF4e, eIF4B, and eIF4G). Overall, the results of this study suggest that steviol can effectively suppress the glucose metabolism and translation initiation in pancreatic cancer cells to mitigate their aggressiveness. This study might help in the design of newer combination therapeutic strategies for pancreatic cancer treatment.

Protein kinase D1 induced epithelial-mesenchymal transition and invasion in salivary adenoid cystic carcinoma via E-cadherin/Snail regulation

Salivary adenoid cystic carcinoma (SACC) is a malignant tumor, which is characterized by a higher incidence of distant metastasis. The aim of this study was to investigate the role and mechanism of protein kinase D1 (PKD1) in regulating the epithelial-mesenchymal transition (EMT) and promotes the metastasis in SACC. We analyzed the expression of PKD1 in 40 SACC patients and different metastatic potential cell lines. Then, we investigated whether the migration and growth of SACC were regulated by PKD1 using shRNA interference or inhibition of kinase active in vitro cell. Moreover, the mechanism by which PKD1 regulates the stability of Snail protein was determined. Finally, nude mice were used to testify the function of PKD1 via tail vein injection. PKD1 was correlated with metastasis and poor prognosis of SACC patients. PKD1 inhibition attenuated proliferation, migration, invasion, and EMT of SACC cells. Conversely, kinase active PKD1 could induce EMT and promoted cell migration in human HSG cell. Furthermore, downregulation of PKD1 regulated Snail via phosphorylation at Ser-11 on Snail protein and promotion of proteasome-mediated degradation, and reduced lung metastasis in vivo. Our results suggest that PKD1 induces the EMT and promotes the metastasis, which illustrate that PKD1 may be a potential prognostic biomarker and serve as a potential therapeutic target for SACC patients.

Small-Molecule Inhibitor Targeting Protein Kinase D: A Potential Therapeutic Strategy

The protein kinase D (PKD) family is a family of serine-threonine kinases that are members of the calcium/calmodulin-dependent kinase (CaMK) superfamily. PKDs have been increasingly implicated in multiple pivotal cellular processes and pathological conditions. PKD dysregulation is associated with several diseases, including cancer, inflammation, and obesity. Over the past few years, small-molecule inhibitors have emerged as alternative targeted therapy with fewer adverse side effects than currently available chemotherapy, and these specifically targeted inhibitors limit non-specific toxicities. The successful development of PKD inhibitors would significantly suppress the growth and proliferation of various cancers and inhibit the progression of other diseases. Various PKD inhibitors have been studied in the preclinical setting. In this context, we summarize the PKD inhibitors under investigation and their application for different kinds of diseases.

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.

Development of cancer metabolism as a therapeutic target: new pathways, patient studies, stratification and combination therapy

Cancer metabolism has undergone a resurgence in the last decade, 70 years after Warburg described aerobic glycolysis as a feature of cancer cells. A wide range of techniques have elucidated the complexity and heterogeneity in preclinical models and clinical studies. What emerges are the large differences between tissues, tumour types and intratumour heterogeneity. However, synergies with inhibition of metabolic pathways have been found for many drugs and therapeutic approaches, and a critical role of window studies and translational trial design is key to success.

Protein Kinase D1 Is Increased in Tumor Tissue, Correlates With Advanced Tumor Features and Worse Prognosis of Non-Small Cell Lung Cancer

OBJECTIVE

This study aimed to assess protein kinase D1 expression and its association with tumor characteristics as well as prognosis in patients with non-small cell lung cancer.

METHODS

Protein kinase D1 expression in tumor tissues and adjacent tissues from 172 patients with non-small cell lung cancer who underwent surgical resection were analyzed by immunohistochemical staining. Based on the total immunohistochemical score, protein kinase D1 expression was classified as protein kinase D1 high expression (further divided into protein kinase D1 high+++, protein kinase D1 high++, and protein kinase D1 high+ expressions) and protein kinase D1 low expression. Clinical characteristics of patients with non-small cell lung cancer were acquired from the database. Accumulating disease-free survival and overall survival were calculated based on patients' relapse/survival status.

RESULTS

Protein kinase D1 expression was increased in tumor tissues compared to adjacent tissues (P < .001). Tumor protein kinase D1 high expression correlated with poorer pathological differentiation (P = .041), increased tumor size (P = .003), the presence of lymph node metastasis (P = .001), and elevated tumor, nodes and metastases stage (P < .001). Besides, both accumulating disease-free survival and overall survival were decreased in patients with tumor protein kinase D1 high expression compared to patients with tumor protein kinase D1 low expression (P = .010 for disease-free survival and P = 0.005 for overall survival). Moreover, they were lowest in patients with tumor protein kinase D1 high+++ expression, followed by patients with tumor protein kinase D1 high++ expression, then patients with tumor protein kinase D1 high+ expression, and highest in patients with tumor protein kinase D1 low expression (P < .001 for disease-free survival and P = .001 for overall survival). Notably, higher tumor protein kinase D1 expression was an independent predictive factor for decreased disease-free survival (P = .001) and overall survival (P = .004).

CONCLUSIONS

Protein kinase D1 might be a potential marker to identify patients with non-small cell lung cancer with worse tumor features and prognosis.