BART inhibits pancreatic cancer cell invasion by PKCα inactivation through binding to ANX7

Potential implications of protein kinase Cα in pathophysiological conditions and therapeutic interventions

PKCα is a molecule with many functions that play an important role in cell survival and death to maintain cellular homeostasis. Alteration in the normal functioning of PKCα is responsible for the complicated etiology of many pathologies, including cancer, cardiovascular diseases, kidney complications, neurodegenerative diseases, diabetics, and many others. Several studies have been carried out over the years on this kinase's function, and regulation in normal physiology and pathological conditions. A lot of data with antithetical results have therefore accumulated over time to create a complex framework of physiological implications connected to the PKCα function that needs comprehensive elucidation. In light of this information, we critically analyze the multiple roles played by PKCα in basic cellular processes and their molecular mechanism during various pathological conditions. This review further discusses the current approaches to manipulating PKCα signaling amplitude in the patient's favour and proposed PKCα as a therapeutic target to reverse pathological states.

Protein Kinase C (PKC) Isozymes as Diagnostic and Prognostic Biomarkers and Therapeutic Targets for Cancer

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.

Annexins and cardiovascular diseases: Beyond membrane trafficking and repair

Cardiovascular diseases (CVD) remain the leading cause of mortality worldwide. The main cause underlying CVD is associated with the pathological remodeling of the vascular wall, involving several cell types, including endothelial cells, vascular smooth muscle cells, and leukocytes. Vascular remodeling is often related with the development of atherosclerotic plaques leading to narrowing of the arteries and reduced blood flow. Atherosclerosis is known to be triggered by high blood cholesterol levels, which in the presence of a dysfunctional endothelium, results in the retention of lipoproteins in the artery wall, leading to an immune-inflammatory response. Continued hypercholesterolemia and inflammation aggravate the progression of atherosclerotic plaque over time, which is often complicated by thrombus development, leading to the possibility of CV events such as myocardial infarction or stroke. Annexins are a family of proteins with high structural homology that bind phospholipids in a calcium-dependent manner. These proteins are involved in several biological functions, from cell structural organization to growth regulation and vesicle trafficking. In vitro gain- or loss-of-function experiments have demonstrated the implication of annexins with a wide variety of cellular processes independent of calcium signaling such as immune-inflammatory response, cell proliferation, migration, differentiation, apoptosis, and membrane repair. In the last years, the use of mice deficient for different annexins has provided insight into additional functions of these proteins in vivo, and their involvement in different pathologies. This review will focus in the role of annexins in CVD, highlighting the mechanisms involved and the potential therapeutic effects of these proteins.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

Leptin Receptor (LEPR) promotes proliferation, migration, and invasion and inhibits apoptosis in hepatocellular carcinoma by regulating ANXA7

Background

Leptin Receptor (LEPR) has been suggested to have several roles in cancer metastasis. However, the role of LEPR and its underlying mechanisms in lymphatic metastasis of hepatocarcinoma have not yet been studied.

Methods

We performed bioinformatics analysis, qRT-PCR, western blotting, immunohistochemistry, immunofluorescence, enzyme-linked immunosorbent, coimmunoprecipitation assays and a series of functional assays to investigate the roles of LEPR in hepatocellular carcinoma.

Results

We discovered that LEPR was highly expressed in liver cancer tissues, and the expression of LEPR in Hca-F cells was higher than that in Hca-P cells. Furthermore, LEPR promotes the proliferation, migration and invasion and inhibits the apoptosis of hepatocarcinoma lymphatic metastatic cells. Further studies indicated that LEPR interacts with ANXA7. Mechanistically, LEPR regulated ERK1/2 and JAK2/STAT3 expression via ANXA7 regulation.

Conclusions

These findings unveiled a previously unappreciated role of LEPR in the regulation of lymphatic metastatic hepatocellular carcinoma, assigning ANXA7-LEPR as a promising therapeutic target for liver cancer treatments.

Downregulation of annexin A7 decreases proliferation, migration, and invasion of gastric cancer cells by reducing matrix metalloproteinase 1 and 9 expression

High annexin A7 expression is a potential indicator of lymphatic metastasis and poor prognosis in patients with gastric cancer (GC). The mechanism underlying the effects of annexin A7 on GC cells remains unclear. In patients with GC, primary adenocarcinoma tissues had higher annexin A7 expression than adjacent non-cancerous tissues (P < 0.05). Among three human GC cell lines with high, moderate, and low levels of differentiation, respectively, the cell line with the lowest level of differentiation displayed the highest level of annexin A7 expression. We transfected cells of the human GC cell line BGC823 with short interfering RNAs (siRNAs) targeting annexin A7 and investigated the effects on signaling pathways related to cancer progression by quantitative real-time PCR and western blot. The silencing of endogenous annexin A7 suppressed the proliferation, migration, and invasion abilities of the BGC823 cells. In the cells treated with annexin A7 siRNA, the expression of p16, p21, and p27 was significantly upregulated while that of proliferating cell nuclear antigen (PCNA), cyclin A, cyclin D1, cyclin E1, matrix metalloproteinase-2 (MMP-2), MMP-9, and intercellular cell-adhesion molecule-1 (ICAM-1) was significantly downregulated compared with that in control cells. Our results suggest that the downregulation of endogenous annexin A7 inhibits GC cell proliferation, migration, and invasion by impacting cell cycle regulators and the expression of MMP-1, MMP-2, and ICAM-1. Targeting annexin A7 may represent a valuable strategy for the diagnosis and clinical treatment of GC.

Annexins - insights from knockout mice

Annexins are a highly conserved protein family that bind to phospholipids in a calcium (Ca2+) - dependent manner. Studies with purified annexins, as well as overexpression and knockdown approaches identified multiple functions predominantly linked to their dynamic and reversible membrane binding behavior. However, most annexins are found at multiple locations and interact with numerous proteins. Furthermore, similar membrane binding characteristics, overlapping localizations and shared interaction partners have complicated identification of their precise functions. To gain insight into annexin function in vivo, mouse models deficient of annexin A1 (AnxA1), A2, A4, A5, A6 and A7 have been generated. Interestingly, with the exception of one study, all mice strains lacking one or even two annexins are viable and develop normally. This suggested redundancy within annexins, but examining these knockout (KO) strains under stress conditions revealed striking phenotypes, identifying underlying mechanisms specific for individual annexins, often supporting Ca2+ homeostasis and membrane transport as central for annexin biology. Conversely, mice lacking AnxA1 or A2 show extracellular functions relevant in health and disease that appear independent of membrane trafficking or Ca2+ signaling. This review will summarize the mechanistic insights gained from studies utilizing mouse models lacking members of the annexin family.

RETRACTED: Annexin A7 modulates BAG4 and BAG4-binding proteins in mitochondrial apoptosis

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concerns were raised in the public domain and also reported by the authors to the journal regarding the similarity between various sections from Figures 1B, 2A, 3A and 4A. Given also the findings of the investigation conducted by the funder, the journal requested the authors to provide the raw data. However, the authors were not able to provide raw data of sufficient quality and detail for the journal to independently audit the provenance and validity of the data, and therefore the Editor-in-Chief decided to retract the article.

IGF2BP3-mediated translation in cell protrusions promotes cell invasiveness and metastasis of pancreatic cancer

Pancreatic cancers are aggressive because they are highly invasive and highly metastatic; moreover, effective treatments for aggressive pancreatic cancers are lacking. Here, we report that IGF2BP3 promoted the invasiveness and metastasis of pancreatic cancers through locally translated IGF2BP3-bound transcripts. In neural cells, transcripts sorted into cytoplasmic RNA granules are transported to dendrites and translated in these dendrites, thereby mediating long-term synaptic plasticity; however, such cytoplasmic RNA granules are not known to contribute to the progression of pancreatic cancer. We show evidence that IGF2BP3 and IGF2BP3-bound transcripts are localized in cytoplasmic RNA granules that accumulate in membrane protrusions of pancreatic cancer cells. Specific IGF2BP3-bound transcripts—ARF6 and ARHGEF4—that are preferentially translated in membrane protrusions induce further formation of membrane protrusions; consequently, IGF2BP3 promotes cell invasiveness and tumor metastasis. Our results provide insight into the link between regulation of localized translation in cell protrusions and the invasiveness and metastasis of pancreatic cancers. New therapies that prevent local translation in cell protrusions may hold significant clinical promise.

Ribonucleoprotein HNRNPA2B1 interacts with and regulates oncogenic KRAS in pancreatic ductal adenocarcinoma cells

BACKGROUND & AIMS

Development of pancreatic ductal adenocarcinoma (PDAC) involves activation of c-Ki-ras2 Kirsten rat sarcoma oncogene homolog (KRAS) signaling, but little is known about the roles of proteins that regulate the activity of oncogenic KRAS. We investigated the activities of proteins that interact with KRAS in PDAC cells.

METHODS

We used mass spectrometry to demonstrate that heterogeneous nuclear ribonucleoproteins (HNRNP) A2 and B1 (encoded by the gene HNRNPA2B1) interact with KRAS G12V. We used co-immunoprecipitation analyses to study interactions between HNRNPA2B1 and KRAS in KRAS-dependent and KRAS-independent PDAC cell lines. We knocked down HNRNPA2B1 using small hairpin RNAs and measured viability, anchorage-independent proliferation, and growth of xenograft tumors in mice. We studied KRAS phosphorylation using the Phos-tag system.

RESULTS

We found that interactions between HRNPA2B1 and KRAS correlated with KRAS-dependency of some human PDAC cell lines. Knock down of HNRNPA2B1 significantly reduced viability, anchorage-independent proliferation, and formation of xenograft tumors by KRAS-dependent PDAC cells. HNRNPA2B1 knock down also increased apoptosis of KRAS-dependent PDAC cells, inactivated c-akt murine thymoma oncogene homolog 1 signaling via mammalian target of rapamycin, and reduced interaction between KRAS and phosphatidylinositide 3-kinase. Interaction between HNRNPA2B1 and KRAS required KRAS phosphorylation at serine 181.

CONCLUSIONS

In KRAS-dependent PDAC cell lines, HNRNPA2B1 interacts with and regulates the activity of KRAS G12V and G12D. HNRNPA2B1 is required for KRAS activation of c-akt murine thymoma oncogene homolog 1-mammalian target of rapamycin signaling, interaction with phosphatidylinositide 3-kinase, and PDAC cell survival and tumor formation in mice. HNRNPA2B1 might be a target for treatment of pancreatic cancer.

Expression of annexin A7 and its clinical significance in differentiation and metastasis of gastric carcinoma

OBJECTIVE

To investigate the expression and clinical significance of annexin A7 in the differentiation and lymphatic metastasis of gastric cancer (GC).

METHODS

The clinical and pathological data were recorded for analysis. Immunohistochemical staining and Western blot were performed to analyze the expression of ANXA 7 in primary GC tissues. Logistic regression analyses were conducted to evaluate the associations between annexin A7 expression levels and differentiations of GC. Analyses of the ROC were conducted to determine the cut-off value of the ratio of pixel density of annexin A7 for predicting lymphatic metastasis of GC.

RESULTS

A total of 162 GC patients were enrolled in this study, and expression rate of annexin A7 was 65.4% in GC. The survival rate of patients with positive expression of annexin A7 was lower than that in patients with negative expression (P=0.000). The results of COX regression showed that the positive expression of annexin A7, submucosal confinement and pathological stage of GC were associated with poor clinical outcomes. The ratio of pixel density value of primary GC tissues with PN 1-3 lymphatic spread was significantly higher than those in tissues with PN 0 lymphatic spread (0.56±0.09 vs. 0.42±0.07, P < 0.05). ROC analysis showed a high area under the curve for the ratio of pixel density value of annexin A7 in primary GC tissues. At a cut-off level of > 0.505, the ratio of pixel density value of annexin A7 exhibited 76.7% sensitivity and 88.3% specificity for detecting lymphatic metastasis of GC.

CONCLUSION

High annexin A7 expression is associated with poor differentiation in GC patients, and it may be a predictor for lymphatic metastasis of GC.

Guanine nucleotide-binding protein subunit beta-2-like 1, a new Annexin A7 interacting protein

We report for the first time that Guanine nucleotide-binding protein subunit beta-2-like 1 (RACK1) formed a complex with Annexin A7. Hca-F and Hca-P are a pair of syngeneic mouse hepatocarcinoma cell lines established and maintained in our laboratory. Our previous study showed that both Annexin A7 and RACK1 were expressed higher in Hca-F (lymph node metastasis >70%) than Hca-P (lymph node metastasis <30%). Suppression of Annexin A7 expression in Hca-F cells induced decreased migration and invasion ability. In this study, knockdown of RACK1 by RNA interference (RNAi) had the same impact on metastasis potential of Hca-F cells as Annexin A7 down-regulation. Furthermore, by co-immunoprecipitation and double immunofluorescence confocal imaging, we found that RACK1 was in complex with Annexin A7 in control cells, but not in the RACK1-down-regulated cells, indicating the abolishment of RACK1-Annexin A7 interaction in Hca-F cells by RACK1 RNAi. Taken together, these results suggest that RACK1-Annexin A7 interaction may be one of the means by which RACK1 and Annexin A7 influence the metastasis potential of mouse hepatocarcinoma cells in vitro.

Potential role of annexin A7 in cancers

Annexin A7 (Anxa7) is a member of the multigene annexin superfamily of Ca(2+)-regulated and phospholipid-binding proteins. Accumulated evidence indicates that the deregulation, loss of heterozygosity (LOH) and subcellular localization of Anxa7 are associated with the occurrence, invasion, metastasis and progression of a variety of cancers. Anxa7 appears to have a tumor-suppression role in glioblastoma, glioblastoma multiforme (GBM), melanoma and prostate cancer (CaP) but, controversially and interestingly, Anxa7 also appears to promote the development and malignancies of liver cancer, gastric cancer (GC), nasopharyngeal carcinoma (NPC), colorectal cancer (CRC) and breast cancer (BC). The associations between Anxa7 and malignant tumors as well as potential mechanisms of action are summarized and discussed in current review. Anxa7 has potential for use as a biomarker for the diagnosis, treatment and prognosis of certain tumors.