A Fhit-mimetic peptide suppresses annexin A4-mediated chemoresistance to paclitaxel in lung cancer cells

Annexin A protein family: Focusing on the occurrence, progression and treatment of cancer

The annexin A (ANXA) protein family is a well-known tissue-specific multigene family that encodes Ca²⁺ phospholipid-binding proteins. A considerable amount of literature is available on the abnormal expression of ANXA proteins in various malignant diseases, including cancer, atherosclerosis and diabetes. As critical regulatory molecules in cancer, ANXA proteins play an essential role in cancer progression, proliferation, invasion and metastasis. Recent studies about their structure, biological properties and functions in different types of cancers are briefly summarised in this review. We further discuss the use of ANXA as new class of targets in the clinical diagnosis and treatment of cancer.

The Tumour Suppressor Fhit Protein Activates C-Raf Ubiquitination and Degradation in Human Melanoma Cells by Interacting with Hsp90

Fhit protein expression is reduced in the majority of human tumors; moreover, its restoration both triggers apoptosis of cancer cells and suppresses tumor formation in a large number of preclinical models of cancers. In the following study, we observed that Fhit expression is significantly reduced in human melanoma cells, and their in vivo growth is blocked by a recombinant adenovirus carrying the FHIT gene. Importantly, we found here that Fhit physically interacts with Hsp90. Since Hsp90 is a chaperone with a crucial function in the conformational maturation and stabilization of C-Raf, we also investigated whether Fhit could interfere with the Hsp90/C-Raf protein complex in melanoma. Interestingly, the administration of the Hsp90 inhibitor 17-AAG, in combination with Fhit protein overexpression in melanoma cells, reacts synergistically to increase C-Raf ubiquitination and degradation. These data reveal Hsp90 as a novel interactor of Fhit and suggest that FHIT activity restoration could represent a helpful strategy for suppressing the oncogenic C-Raf pathway in the therapy of human melanoma.

Pathobiological functions and clinical implications of annexin dysregulation in human cancers

Annexins are an extensive superfamily of structurally related calcium- and phospholipid-binding proteins, largely conserved and widely distributed among species. Twelve human annexins have been identified, referred to as Annexin A1-13 (A12 remains as of yet unassigned), whose genes are spread throughout the genome on eight different chromosomes. According to their distinct tissue distribution and subcellular localization, annexins have been functionally implicated in a variety of biological processes relevant to both physiological and pathological conditions. Dysregulation of annexin expression patterns and functions has been revealed as a common feature in multiple cancers, thereby emerging as potential biomarkers and molecular targets for clinical application. Nevertheless, translation of this knowledge to the clinic requires in-depth functional and mechanistic characterization of dysregulated annexins for each individual cancer type, since each protein exhibits varying expression levels and phenotypic specificity depending on the tumor types. This review specifically and thoroughly examines the current knowledge on annexin dysfunctions in carcinogenesis. Hence, available data on expression levels, mechanism of action and pathophysiological effects of Annexin A1-13 among different cancers will be dissected, also further discussing future perspectives for potential applications as biomarkers for early diagnosis, prognosis and molecular-targeted therapies. Special attention is devoted to head and neck cancers (HNC), a complex and heterogeneous group of aggressive malignancies, often lately diagnosed, with high mortality, and scarce therapeutic options.

Overcome Chemoresistance: Biophysical and Structural Analysis of Synthetic FHIT-Derived Peptides

The fragile histidine triad (FHIT) protein is a member of the large and ubiquitous histidine triad (HIT) family of proteins. On the basis of genetic evidence, it has been postulated that the FHIT protein may function as tumor suppressor, implying a role for the FHIT protein in carcinogenesis. Recently, Gaudio et al. reported that FHIT binds and delocalizes annexin A4 (ANXA4) from plasma membrane to cytosol in paclitaxel-resistant lung cancer cells, thus restoring their chemosensitivity to the drug. They also identified the smallest protein sequence of the FHIT still interacting with ANXA4, ranging from position 7 to 13: QHLIKPS. This short sequence of FHIT protein was not only able to bind ANXA4 but also to hold its target in the cytosol during paclitaxel treatment, thus avoiding ANXA4 translocation to the inner side of the cell membrane. Starting from these results, to obtain much information about structure requirements involved in the interaction of the peptide mentioned above, we synthetized a panel of seven peptides through an Ala-scan approach. In detail, to study the binding of FHIT derived peptides with ANXA4, we applied a combination of different biophysical techniques such as differential scanning fluorimetry (DSF), surface plasmon resonance (SPR), and microscale thermophoresis (MST). Circular dichroism (CD) and nuclear magnetic resonance (NMR) were used to determine the conformational structure of the lead peptide (7–13) and peptides generated from ala-scan technique. The application of different biophysical and structural techniques, integrated by a preliminary biological evaluation, allowed us to build a solid structure activity relationship on the synthesized peptides.

Intracellular Calcium Homeostasis and Kidney Disease

Kidney disease is a serious health problem that burdens our healthcare system. It is crucial to find the accurate pathogenesis of various types of kidney disease to provide guidance for precise therapies for patients suffering from these diseases. However, the exact molecular mechanisms underlying these diseases have not been fully understood. Disturbance of calcium homeostasis in renal cells plays a fundamental role in the development of various types of kidney disease, such as primary glomerular disease, diabetic nephropathy, acute kidney injury and polycystic kidney disease, through promoting cell proliferation, stimulating extracellular matrix accumulation, aggravating podocyte injury, disrupting cellular energetics as well as dysregulating cell survival and death dynamics. As a result, preventing the disturbance of calcium homeostasis in specific renal cells (such as tubular cells, podocytes and mesangial cells) is becoming one of the most promising therapeutic strategies in the treatment of kidney disease. The endoplasmic reticulum and mitochondria are two vital organelles in this process. Calcium ions cycle between the endoplasmic reticulum and mitochondria at the conjugation of these two organelles known as the mitochondria-associated endoplasmic reticulum membrane, maintaining calcium homeostasis. The pharmacologic modulation of cellular calcium homeostasis can be viewed as a novel therapeutic method for renal diseases. Here, we will introduce calcium homeostasis under physiological conditions and the disturbance of calcium homeostasis in kidney diseases. We will focus on the calcium homeostasis regulation in renal cells (including tubular cells, podocytes and mesangial cells), especially in the mitochondria- associated endoplasmic reticulum membranes of these renal cells.

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.

Expression levels and prognostic values of annexins in liver cancer

Annexins are a superfamily of calcium-dependent phospholipid-binding proteins that are implicated in a wide range of biological processes. The annexin superfamily comprises 13 members in humans (ANXAs), the majority of which are frequently dysregulated in cancer. However, the expression patterns and prognostic values of ANXAs in liver cancer are currently largely unknown. The present study aimed to analyze the expression levels of ANXAs and survival data in patients with liver cancer from the Oncomine, GEPIA, Kaplan-Meier plotter and cBioPortal for Cancer Genomics databases. The results demonstrated that ANXA1, A2, A3, A4 and A5 were upregulated, whereas ANXA10 was downregulated in liver cancer compared with normal liver tissues. The expression of ANXA10 was associated with pathological stage. High expression levels of ANXA2 and A5 were significantly associated with poor overall survival (OS) rate whereas ANXA7 and A10 were associated with increased OS. The prognostic values of ANXAs in liver cancer were determined based on sex and clinical stage, which revealed that ANXA2, A5, A7 and A10 were associated with OS in male, but not in female patients. In addition, the potential biological functions of ANXAs were identified by Gene Ontology functional annotation and Kyoto Encyclopedia of Genes Genomes pathway analysis; the results demonstrated that ANXAs may serve a role in liver cancer through the neuroactive ligand-receptor interaction pathway. In conclusion, the results of the present study suggested that ANXA1, A2, A3, A4, A5 and A10 may be potential therapeutic targets for liver cancer treatment, and that ANXA2, A5, A7 and A10 may be potential prognostic biomarkers of liver cancer.

Therapeutic implications of novel peptides targeting ER-mitochondria Ca2+-flux systems

Intracellular Ca²⁺-flux systems located at the ER-mitochondrial axis govern mitochondrial Ca²⁺ balance and cell fate. Multiple yet incurable pathologies are characterized by insufficient or excessive Ca²⁺ fluxes toward the mitochondria, in turn leading to aberrant cell life or death dynamics. The discovery and ongoing molecular characterization of the main interorganellar Ca²⁺ gateways have resulted in a novel class of peptide tools able to regulate relevant protein-protein interactions (PPIs) underlying this signaling scenario. Here, we review peptides, molecularly derived from Ca²⁺-flux systems or their accessory proteins. We discuss how they alter Ca²⁺-signaling protein complexes and modulate cell survival in light of their forthcoming therapeutic applications.

Fhit, a tumor suppressor protein, induces autophagy via 14-3-3τ in non-small cell lung cancer cells

Inactivation of the fragile histidine triad (Fhit) gene has been reported in the majority of human cancers, particularly in lung cancer. The role of Fhit as a tumor suppressor gene has been well documented, and restoration of Fhit expression suppresses tumorigenicity in tumor cell lines and in mouse models by inducing apoptosis and inhibiting proliferation of tumor cells. Autophagy is a catabolic pathway, whereby cytoplasmic proteins and organelles are sequestered in vacuoles and delivered to lysosomes for degradation and recycling. Although autophagy is necessary for cell survival under stress conditions, recent studies have shown that autophagy can also promote cell death. Due to the fact that both autophagy induction and Fhit expression are commonly associated with nutrient starvation, we hypothesized that Fhit expression may be related to autophagy induction. In the present study, we assessed whether Fhit overexpression by gene transfer induces autophagy in Fhit-deficient non-small cell lung cancer (NSCLC) cells. The results of our study indicate that Fhit protein induces autophagy in NSCLC cells, and that this autophagy prevents apoptotic cell death in vivo and in vitro in a 14-3-3τ protein-dependent manner. To the best of our knowledge, this is the first report to describe Fhit-induced autophagy. Suppressing autophagy might be a promising therapeutic option to enhance the efficacy of Fhit gene therapy in NSCLC.

A novel splice variant of the protein tyrosine phosphatase PTPRJ that encodes for a soluble protein involved in angiogenesis

PTPRJ is a receptor protein tyrosine phosphatase with tumor suppressor activity. Very little is known about the role of PTPRJ ectodomain, although recently both physiological and synthetic PTPRJ ligands have been identified. A putative shorter spliced variant, coding for a 539 aa protein corresponding to the extracellular N-terminus of PTPRJ, is reported in several databases but, currently, no further information is available.

Here, we confirmed that the PTPRJ short isoform (named sPTPRJ) is a soluble protein secreted into the supernatant of both endothelial and tumor cells. Like PTPRJ, also sPTPRJ undergoes post-translational modifications such as glycosylation, as assessed by sPTPRJ immunoprecipitation. To characterize its functional activity, we performed an endothelial cell tube formation assay and a wound healing assay on HUVEC cells overexpressing sPTPRJ and we found that sPTPRJ has a proangiogenic activity. We also showed that sPTPRJ expression down-regulates endothelial adhesion molecules, that is a hallmark of proangiogenic activity. Moreover, sPTPRJ mRNA levels in human high-grade glioma, one of the most angiogenic tumors, are higher in tumor samples compared to controls. Further studies will be helpful not only to clarify the way sPTPRJ works but also to supply clues to circumvent its activity in cancer therapy.

Role of epigenetics in lung cancer heterogeneity and clinical implication

Lung cancer, as a highly heterogeneous disease, can be initiated and progressed through the interaction between permanent genetic mutations and dynamic epigenetic alterations. However, the mediating mechanisms of epigenetics in cancer heterogeneity remain unclear. The evolution of cancer, the existence of cancer stem cells (CSCs) and the phenomenon of epithelial-mesenchymal transition (EMT) have been reported to be involved in lung cancer heterogeneity. In this review, we briefly recap the definition of heterogeneity and concept of epigenetics, highlight the potential roles and mechanisms of epigenetic regulation in heterogeneity of lung cancer, and summarize the diagnostic and therapeutic implications of epigenetic alterations in lung cancer, especially the role of DNA methylation and histone acetylation. Deep understanding of epigenetic regulation in cancer heterogeneity is instrumental to the design of novel therapeutic approaches that target lung cancer.