A novel and selective inhibitor of PKC ζ potently inhibits human breast cancer metastasis in vitro and in mice

PTX3 promotes breast cancer cell proliferation and metastasis by regulating PKCζbreast cancer, pentraxin 3, protein kinase Cζ, proliferation, metastasis

Breast cancer (BC) is the most commonly diagnosed cancer in women, providing a leading cause of death from malignancy. Pentraxin 3 (PTX3) and protein kinase C ζ (PKCζ) are both known to exert important roles in the progression of multiple types of tumors, including BC. The present study aimed to explore both their interaction and their role in promoting the proliferation and metastasis of BC. The expression level of PTX3 was found to be elevated both in patients with BC and in BC cells; furthermore, it was found to be associated with lymph node metastasis in patients with BC. Knockdown of PTX3 decreased the rate of cell proliferation and the effects of a series of metastasis-associated cellular processes, including cell chemotaxis, migration, adhesion and invasion, as well as diminishing actin polymerization of the MDA-MB-231 and MCF7 BC cells, and decreasing tumor pulmonary metastasis in vivo. Mechanistically, PTX3 and PKCζ were found to be colocalized intracellularly, and they were co-translocated to the cell membrane upon stimulation with epidermal growth factor. Following the knockdown of PTX3, both the phosphorylation and membrane translocation of PKCζ were significantly impaired, suggesting that PTX3 regulates the activation of PKCζ. Taken together, the findings of the present study have shown that PTX3 may promote the proliferation and metastasis of BC cells through regulating PKCζ activation to enhance cell migration, cell chemotaxis, cell invasion and cell adhesion.

Evaluating the current status of protein kinase C (PKC)-protein kinase D (PKD) signalling axis as a novel therapeutic target in ovarian cancer

Ovarian cancer, especially high grade serous ovarian cancer is one of the most lethal gynaecological malignancies with high relapse rate and patient death. Notwithstanding development of several targeted treatment and immunotherapeutic approaches, researchers fail to turn ovarian cancer into a manageable disease. Protein kinase C (PKC) and protein kinase D (PKD) are families of evolutionarily conserved serine/threonine kinases that can be activated by a plethora of extracellular stimuli such as hormones, growth factors and G-protein coupled receptor agonists. Recent literature suggests that a signalling cascade initiated by these two protein kinases regulates a battery of cellular and physiological processes involved in tumorigenesis including cell proliferation, migration, invasion and angiogenesis. In an urgent need to discover novel therapeutic interventions against a deadly pathology like ovarian cancer, we have discussed the status quo of PKC/PKD signalling axis in context of this disease. Additionally, apart from discussing the structural properties and activation mechanisms of PKC/PKD, we have provided a comprehensive review of the recent reports on tumor promoting functions of PKC isoforms and discussed the potential of PKC/PKD signalling axis as a novel target in this lethal pathology. Furthermore, in this review, we have discussed the significance of several recent clinical trials and development of small molecule inhibitors that target PKC/PKD signalling axis in ovarian cancer.

Autoencoded DNA methylation data to predict breast cancer recurrence: Machine learning models and gene-weight significance

Breast cancer is the most frequent cancer in women and the second most frequent overall after lung cancer. Although the 5-year survival rate of breast cancer is relatively high, recurrence is also common which often involves metastasis with its consequent threat for patients. DNA methylation-derived databases have become an interesting primary source for supervised knowledge extraction regarding breast cancer. Unfortunately, the study of DNA methylation involves the processing of hundreds of thousands of features for every patient. DNA methylation is featured by High Dimension Low Sample Size which has shown well-known issues regarding feature selection and generation. Autoencoders (AEs) appear as a specific technique for conducting nonlinear feature fusion. Our main objective in this work is to design a procedure to summarize DNA methylation by taking advantage of AEs. Our proposal is able to generate new features from the values of CpG sites of patients with and without recurrence. Then, a limited set of relevant genes to characterize breast cancer recurrence is proposed by the application of survival analysis and a pondered ranking of genes according to the distribution of their CpG sites. To test our proposal we have selected a dataset from The Cancer Genome Atlas data portal and an AE with a single-hidden layer. The literature and enrichment analysis (based on genomic context and functional annotation) conducted regarding the genes obtained with our experiment confirmed that all of these genes were related to breast cancer recurrence.

Analysis of PKC-ζ protein levels in normal and malignant breast tissue subtypes

It is estimated that breast cancer will be the second leading cause of cancer-associated mortality in women in 2018. Previous research has demonstrated that the atypical protein kinase C-ζ (PKC-ζ) is a component of numerous dysregulated pathways in breast cancer, including cellular proliferation, survival, and cell cycle upregulation. The present study investigated the PKC-ζ protein in breast tissue to evaluate its potential as a biomarker for breast cancer invasion, and demonstrated that an overexpression of PKC-ζ protein can be indicative of carcinogenesis. The present study analyzed the expression of PKC-ζ in individuals with no tumor complications and malignant female human breast tissue samples (lobular carcinoma in situ, invasive lobular carcinoma, ductal carcinoma in situ and invasive ductal carcinoma) with the use of western blot analysis, immunohistochemistry and statistical analysis (83 samples). The present study also evaluated the invasive behavior of MDA-MB-231 breast cancer cells following the knockdown of PKC-ζ with a Transwell invasion assay and an immunofluorescent probe for filamentous actin (F-actin) organization. The data demonstrated that PKC-ζ expression was identified to be higher in invading tissues when compared with non-invading tissues. The results also suggest that PKC-ζ is more abundant in ductal tissues when compared with lobular tissues. In addition, the protein studies also suggest that PKC-ζ is a component for invasive behavior through the Ras-related C3 botulinum toxin substrate 1 (Rac1) and Ras homolog gene family member A (RhoA) pathway, and PKC-ζ is required for the F-actin reorganization in invasive cells. Therefore, PKC-ζ should be considered to be a biomarker in the development of breast cancer as well as an indicator of invading tumor cells.

PKCζ Phosphorylates SIRT6 to Mediate Fatty Acid β-Oxidation in Colon Cancer Cells

Protein kinase C (PKC) has critical roles in regulating lipid anabolism and catabolism. PKCζ, a member of atypical PKC family, has been reported to mediate glucose metabolism. However, whether and how PKCζ regulates tumor cells fatty acid β-oxidation are unknown. Here, we report that the phosphorylation of SIRT6 is significantly increased after palmitic acid (PA) treatment in colon cancer cells. PKCζ can physically interact with SIRT6 in vitro and in vivo, and this interaction enhances following PA treatment. Further experiments show that PKCζ is the phosphorylase of SIRT6 and phosphorylates SIRT6 at threonine 294 residue to promote SIRT6 enrichment on chromatin. In the functional study, we find that the expression of ACSL1, CPT1, CACT, and HADHB, the genes related to fatty acid β-oxidation, increases after PA stimulation. We further confirm that PKCζ mediates the binding of SIRT6 specifically to the promoters of fatty acid β-oxidation–related genes and elicits the expression of these genes through SIRT6 phosphorylation. Our findings demonstrate the mechanism of PKCζ as a new phosphorylase of SIRT6 on maintaining tumor fatty acid β-oxidation and define the new role of PKCζ in lipid homeostasis.

Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease

Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.

Metabolomics research on potential role for 9-cis-retinoic acid in breast cancer progression

Deciphering the molecular networks that discriminate organ-confined breast cancer from metastatic breast cancer may lead to the identification of critical biomarkers for breast cancer invasion and aggressiveness. Here metabolomics, a global study of metabolites, has been applied to explore the metabolic alterations that characterize breast cancer progression. We profiled a total of 693 metabolites across 87 serum samples related to breast cancer (46 clinically localized and 41 metastatic breast cancer) and 49 normal samples. These unbiased metabolomic profiles were able to distinguish normal individuals, clinically localized and metastatic breast cancer patients. 9-cis-Retinoic acid, an isomer of all-trans retinoic acid, was identified as a differential metabolite that significantly decreased during breast cancer progression to metastasis, and its levels were also reduced in urine samples from biopsy-positive breast cancer patients relative to biopsy-negative individuals and in invasive breast cancer cells relative to benign MCF-10A cells. The addition of exogenous 9-cis-retinoic acid to MDA-MB-231 cells and knockdown of aldehyde dehydrogenase 1 family member A1, a regulatory enzyme for 9-cis-retinoic acid, remarkably impaired cell invasion and migration, presumably through preventing the key regulator cofilin from activation and inhibiting MMP2 and MMP9 expression. Taken together, our study showed the potential inhibitory role for 9-cis-retinoic acid in breast cancer progression by attenuating cell invasion and migration.

Baicalin Inhibits Human Cervical Cancer Cells by Suppressing Protein Kinase C/Signal Transducer and Activator of Transcription (PKC/STAT3) Signaling Pathway

BACKGROUND Like other human cancers, the malignancy of cervical cancer is also characterized by abilities of proliferation, migration, and invasion. Protein kinase C-zeta (PKCζ) has been highly correlated with several human cancers. Baicalin was proven to regulate PKC. This study aimed to investigate the anti-cancer effect and involved molecular mechanisms of baicalin on human cervical cancer. MATERIAL AND METHODS Baicalin at various concentrations was used to treat 2 human cervical cancer cell lines HeLa and SiHa. The proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenylterazolium bromide (MTT) assay. The apoptosis was detected by terminal transferase UTP nick end labeling (TUNEL) assay. Wound healing assay and Transwell assay were used to evaluate the migration and invasion respectively. Western blotting was performed to assess the protein expression levels. RESULTS Baicalin administration significantly reduced the viability by facilitating the apoptosis in HeLa and SiHa cells. Baicalin treatment also significantly reduced the wound closure and cell amount invaded as measured by Transwell assay. The expression levels of PKCζ, survivin, matrix metalloproteinase (MMP)2, MMP9 as well as the phosphorylation of signal transducer and activator of transcription (STAT) 3 were reduced in baicalin administrated cervical cancer cells. CONCLUSIONS Baicalin exerted anti-cancer effects on human cervical cancer cells by targeting STAT3 regulated signaling pathways.

Combination therapy of PKCζ and COX-2 inhibitors synergistically suppress melanoma metastasis

Background

Metastatic malignant melanoma is one of the most aggressive malignancies and its treatment remains challenging. Recent studies demonstrate that the melanoma metastasis has correlations with the heightened activations of protein kinase C ζ (PKCζ) and cyclooxygenase-2 (COX-2) signaling pathways. Targeted inhibitions for PKCζ and COX-2 have been considered as the promising strategies for the treatment of melanoma metastasis. Thus, the PKCζ inhibitor J-4 and COX-2 inhibitor Celecoxib were combined to treat melanoma metastasis in this study.

Methods

The Transwell assay, Wound-healing assay and Adhesion assay were used to evaluate the inhibition of combined therapy of J-4 and Celecoxib on melanoma cells invasion, migration and adhesion in vitro, respectively. The impaired actin polymerization was observed by confocal microscope and inactivated signal pathways about PKCζ and COX-2 were confirmed by the Western blotting assay. The B16-F10/C57BL mouse melanoma model was used to test the inhibition of combined therapy of J-4 and Celecoxib on melanoma metastasis in vivo.

Results

The in vitro results showed that the combination of J-4 and Celecoxib exerted synergistic inhibitory effects on the migration, invasion and adhesion of melanoma B16-F10 and A375 cells with combination index less than 1. The actin polymerization and phosphorylation of Cofilin required in cell migration were severely impaired, which is due to the inactivation of PKCζ related signal pathways and the decrease of COX-2. The combined inhibition of PKCζ and COX-2 induced Mesenchymal-Epithelial Transition (MET) in melanoma cells with the expression of E-Cadherin increasing and Vimentin decreasing. The secretion of MMP-2/MMP-9 also significantly decreased after the combination treatment. In C57BL/6 mice intravenously injected with B16-F10 cells (5 × 10⁴ cells/mouse), co-treatment of J-4 and Celecoxib also severely suppressed melanoma lung metastasis. The body weight monitoring and HE staining results indicated the low toxicity of the combination therapy.

Conclusions

This study demonstrates that the combination therapy of PKCζ and COX-2 inhibitors can significantly inhibit melanoma metastasis in vitro and in vivo, which will be an efficient strategy for treatment of melanoma metastasis in clinics.

Antitumor Effects of JAK3 Inhibitor on the Model of Transplantable Lewis Lung Carcinoma and Mechanisms of Their Development

Mice with Lewis lung carcinoma were used to study the antitumor and antimetastatic effects of JAK3 inhibitor. The study revealed no effect of JAK3 inhibitor on the growth of primary tumor node, but found a pronounced inhibition of hematogenous spread of the pathologic process into the lungs. In vitro blockade of JAK3 in cultured Lewis lung carcinoma produced no effect on the count of the stem tumor cells and stimulated functions of committed elements. In addition, blockade of JAK3 significantly elevated maturation index of the tumor tissue.