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Kawano T, Inokuchi J, Eto M, Murata M, Kang JH. Protein Kinase C (PKC) Isozymes as Diagnostic and Prognostic Biomarkers and Therapeutic Targets for Cancer. Cancers (Basel) 2022; 14:5425. [PMID: 36358843 PMCID: PMC9658272 DOI: 10.3390/cancers14215425] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/02/2022] [Accepted: 11/02/2022] [Indexed: 08/05/2023] Open
Abstract
Protein kinase C (PKC) is a large family of calcium- and phospholipid-dependent serine/threonine kinases that consists of at least 11 isozymes. Based on their structural characteristics and mode of activation, the PKC family is classified into three subfamilies: conventional or classic (cPKCs; α, βI, βII, and γ), novel or non-classic (nPKCs; δ, ε, η, and θ), and atypical (aPKCs; ζ, ι, and λ) (PKCλ is the mouse homolog of PKCι) PKC isozymes. PKC isozymes play important roles in proliferation, differentiation, survival, migration, invasion, apoptosis, and anticancer drug resistance in cancer cells. Several studies have shown a positive relationship between PKC isozymes and poor disease-free survival, poor survival following anticancer drug treatment, and increased recurrence. Furthermore, a higher level of PKC activation has been reported in cancer tissues compared to that in normal tissues. These data suggest that PKC isozymes represent potential diagnostic and prognostic biomarkers and therapeutic targets for cancer. This review summarizes the current knowledge and discusses the potential of PKC isozymes as biomarkers in the diagnosis, prognosis, and treatment of cancers.
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Affiliation(s)
- Takahito Kawano
- Center for Advanced Medical Innovation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Junichi Inokuchi
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Masatoshi Eto
- Center for Advanced Medical Innovation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Masaharu Murata
- Center for Advanced Medical Innovation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Jeong-Hun Kang
- Division of Biopharmaceutics and Pharmacokinetics, National Cerebral and Cardiovascular Center Research Institute, 6-1 Shinmachi, Kishibe, Suita, Osaka 564-8565, Japan
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Unraveling the hidden role of a uORF-encoded peptide as a kinase inhibitor of PKCs. Proc Natl Acad Sci U S A 2021; 118:2018899118. [PMID: 34593629 PMCID: PMC8501901 DOI: 10.1073/pnas.2018899118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2021] [Indexed: 02/01/2023] Open
Abstract
Approximately 40% of human messenger RNAs (mRNAs) contain upstream open reading frames (uORFs) in their 5' untranslated regions. Some of these uORF sequences, thought to attenuate scanning ribosomes or lead to mRNA degradation, were recently shown to be translated, although the function of the encoded peptides remains unknown. Here, we show a uORF-encoded peptide that exhibits kinase inhibitory functions. This uORF, upstream of the protein kinase C-eta (PKC-η) main ORF, encodes a peptide (uPEP2) containing the typical PKC pseudosubstrate motif present in all PKCs that autoinhibits their kinase activity. We show that uPEP2 directly binds to and selectively inhibits the catalytic activity of novel PKCs but not of classical or atypical PKCs. The endogenous deletion of uORF2 or its overexpression in MCF-7 cells revealed that the endogenously translated uPEP2 reduces the protein levels of PKC-η and other novel PKCs and restricts cell proliferation. Functionally, treatment of breast cancer cells with uPEP2 diminished cell survival and their migration and synergized with chemotherapy by interfering with the response to DNA damage. Furthermore, in a xenograft of MDA-MB-231 breast cancer tumor in mice models, uPEP2 suppressed tumor progression, invasion, and metastasis. Tumor histology showed reduced proliferation, enhanced cell death, and lower protein expression levels of novel PKCs along with diminished phosphorylation of PKC substrates. Hence, our study demonstrates that uORFs may encode biologically active peptides beyond their role as translation regulators of their downstream ORFs. Together, we point to a unique function of a uORF-encoded peptide as a kinase inhibitor, pertinent to cancer therapy.
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Hart M, Rheinheimer S, Leidinger P, Backes C, Menegatti J, Fehlmann T, Grässer F, Keller A, Meese E. Identification of miR-34a-target interactions by a combined network based and experimental approach. Oncotarget 2018; 7:34288-99. [PMID: 27144431 PMCID: PMC5085156 DOI: 10.18632/oncotarget.9103] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 04/16/2016] [Indexed: 12/25/2022] Open
Abstract
Circulating miRNAs have been associated with numerous human diseases. The lack of understanding the functional roles of blood-born miRNAs limits, however, largely their value as disease marker. In a systems biology analysis we identified miR-34a as strongly associated with pathogenesis. Genome-wide analysis of miRNAs in blood cell fractions highlighted miR-34a as most significantly up-regulated in CD3+ cells of lung cancer patients. By our in silico analysis members of the protein kinase C family (PKC) were indicated as miR-34a target genes. Using a luciferase assay, we confirmed binding of miR-34a-5p to target sequences within the 3′UTRs of five PKC family members. To verify the biological effect, we transfected HEK 293T and Jurkat cells with miR-34a-5p causing reduced endogenous protein levels of PKC isozymes. By combining bioinformatics approaches with experimental validation, we demonstrate that one of the most relevant disease associated miRNAs has the ability to control the expression of a gene family.
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Affiliation(s)
- Martin Hart
- Institute of Human Genetics, Saarland University, 66421 Homburg, Germany
| | | | - Petra Leidinger
- Institute of Human Genetics, Saarland University, 66421 Homburg, Germany
| | - Christina Backes
- Chair for Clinical Bioinformatics, Saarland University, 66123 Saarbrücken, Germany
| | - Jennifer Menegatti
- Institute of Virology, Saarland University Medical School, 66421 Homburg, Germany
| | - Tobias Fehlmann
- Chair for Clinical Bioinformatics, Saarland University, 66123 Saarbrücken, Germany
| | - Friedrich Grässer
- Institute of Virology, Saarland University Medical School, 66421 Homburg, Germany
| | - Andreas Keller
- Chair for Clinical Bioinformatics, Saarland University, 66123 Saarbrücken, Germany
| | - Eckart Meese
- Institute of Human Genetics, Saarland University, 66421 Homburg, Germany
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PKCη is an anti-apoptotic kinase that predicts poor prognosis in breast and lung cancer. Biochem Soc Trans 2015; 42:1519-23. [PMID: 25399563 DOI: 10.1042/bst20140182] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The successful treatment of cancer in a disseminated stage using chemotherapy is limited by the occurrence of drug resistance, often mediated by anti-apoptotic mechanisms. Thus the challenge is to pinpoint the underlying key factors and to develop therapies for their direct targeting. Protein kinase C (PKC) enzymes are promising candidates, as some PKCs were shown to be involved in regulation of apoptosis. Our studies and others have shown that PKCη is an anti-apoptotic kinase, able to confer protection on tumour cells against stress and chemotherapy. We have demonstrated that PKCη shuttles between the cytoplasm and the nucleus and that upon DNA damage is tethered at the nuclear membrane. The C1b domain mediates translocation of PKCη to the nuclear envelope and, similar to the full-length protein, could also confer protection against cell death. Furthermore, its localization in cell and nuclear membranes in breast cancer biopsies of neoadjuvant-treated breast cancer patients was an indicator for poor survival and a predictor for the effectiveness of treatment. PKCη is also a novel biomarker for poor prognosis in non-small-cell lung cancer (NSCLC). Thus PKCη presents a potential target for therapy where inhibition of its activity and/or translocation to membranes could interfere with the resistance to chemotherapy.
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Zurgil U, Ben-Ari A, Atias K, Isakov N, Apte R, Livneh E. PKCη promotes senescence induced by oxidative stress and chemotherapy. Cell Death Dis 2014; 5:e1531. [PMID: 25412309 PMCID: PMC4260739 DOI: 10.1038/cddis.2014.481] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 10/06/2014] [Accepted: 10/09/2014] [Indexed: 12/21/2022]
Abstract
Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabolic activity, in conjunction with the secretion of a complex mixture of extracellular proteins and soluble factors known as the senescence-associated secretory phenotype (SASP). Cellular senescence has been shown to prevent the proliferation of potentially tumorigenic cells, and is thus generally considered a tumor suppressive process. However, some SASP components may act as pro-tumorigenic mediators on premalignant cells in the microenvironment. A limited number of studies indicated that protein kinase C (PKC) has a role in senescence, with different isoforms having opposing effects. It is therefore important to elucidate the functional role of specific PKCs in senescence. Here we show that PKCη, an epithelial specific and anti-apoptotic kinase, promotes senescence induced by oxidative stress and DNA damage. We further demonstrate that PKCη promotes senescence through its ability to upregulate the expression of the cell cycle inhibitors p21Cip1 and p27Kip1 and enhance transcription and secretion of interleukin-6 (IL-6). Moreover, we demonstrate that PKCη creates a positive loop for reinforcing senescence by increasing the transcription of both IL-6 and IL-6 receptor, whereas the expression of IL-8 is specifically suppressed by PKCη. Thus, the presence/absence of PKCη modulates major components of SASP. Furthermore, we show that the human polymorphic variant of PKCη, 374I, that exhibits higher kinase activity in comparison to WT-374V, is also more effective in IL-6 secretion, p21Cip1 expression and the promotion of senescence, further supporting a role for PKCη in senescence. As there is now considerable interest in senescence activation/elimination to control tumor progression, it is first crucial to reveal the molecular regulators of senescence. This will improve our ability to develop new strategies to harness senescence as a potential cancer therapy in the future.
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Affiliation(s)
- U Zurgil
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - A Ben-Ari
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - K Atias
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - N Isakov
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - R Apte
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - E Livneh
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
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Abstract
Protein kinase C (PKC) is a family of phospholipid-dependent serine/threonine kinases, which can be further classified into three PKC isozymes subfamilies: conventional or classic, novel or nonclassic, and atypical. PKC isozymes are known to be involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and drug resistance. Because of their key roles in cell signaling, PKC isozymes also have the potential to be promising therapeutic targets for several diseases, such as cardiovascular diseases, immune and inflammatory diseases, neurological diseases, metabolic disorders, and multiple types of cancer. This review primarily focuses on the activation, mechanism, and function of PKC isozymes during cancer development and progression.
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Wallace JA, Pitarresi JR, Sharma N, Palettas M, Cuitiño MC, Sizemore ST, Yu L, Sanderlin A, Rosol TJ, Mehta KD, Sizemore GM, Ostrowski MC. Protein kinase C Beta in the tumor microenvironment promotes mammary tumorigenesis. Front Oncol 2014; 4:87. [PMID: 24795864 PMCID: PMC4006052 DOI: 10.3389/fonc.2014.00087] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 04/08/2014] [Indexed: 02/04/2023] Open
Abstract
Protein kinase C beta (PKCβ) expression in breast cancer is associated with a more aggressive tumor phenotype, yet the mechanism for how PKCβ is pro-tumorigenic in this disease is still unclear. Interestingly, while it is known that PKCβ mediates angiogenesis, immunity, fibroblast function and adipogenesis, all components of the mammary tumor microenvironment (TME), no study to date has investigated whether stromal PKCβ is functionally relevant in breast cancer. Herein, we evaluate mouse mammary tumor virus–polyoma middle T-antigen (MMTV–PyMT) induced mammary tumorigenesis in the presence and absence of PKCβ. We utilize two model systems: one where PKCβ is deleted in both the epithelial and stromal compartments to test the global requirement for PKCβ on tumor formation, and second, where PKCβ is deleted only in the stromal compartment to test its role in the TME. MMTV–PyMT mice globally lacking PKCβ live longer and develop smaller tumors with decreased proliferation and decreased macrophage infiltration. Similarly, when PKCβ is null exclusively in the stroma, PyMT-driven B6 cells form smaller tumors with diminished collagen deposition. These experiments reveal for the first time a tumor promoting role for stromal PKCβ in MMTV–PyMT tumorigenesis. In corroboration with these results, PKCβ mRNA (Prkcb) is increased in fibroblasts isolated from MMTV–PyMT tumors. These data were confirmed in a breast cancer patient cohort. Combined these data suggest the continued investigation of PKCβ in the mammary TME is necessary to elucidate how to effectively target this signaling pathway in breast cancer.
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Affiliation(s)
- Julie A Wallace
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Jason R Pitarresi
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Nandini Sharma
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Marilly Palettas
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Maria C Cuitiño
- Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Steven T Sizemore
- Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA ; Department of Radiation Oncology, The Ohio State University , Columbus, OH , USA
| | - Lianbo Yu
- Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA ; Center for Biostatistics, The Ohio State University , Columbus, OH , USA
| | - Allen Sanderlin
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Thomas J Rosol
- Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA ; Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University , Columbus, OH , USA
| | - Kamal D Mehta
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA
| | - Gina M Sizemore
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
| | - Michael C Ostrowski
- Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University , Columbus, OH , USA ; Comprehensive Cancer Center, The Ohio State University , Columbus, OH , USA
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