Annexin A4 is a possible biomarker for cisplatin susceptibility of malignant mesothelioma cells

FOXD1-activated ANXA3 facilitates cisplatin resistance of lung cancer cells via promoting ANXA4 expression

The expression of Annexin A3 (ANXA3) is thought to be associated with chemoresistance in lung cancer. However, the underlying molecular mechanisms of ANXA3-mediated cisplatin (DDP) resistance in lung cancer still need to be further explored. The levels of ANXA3, forkhead box D1 (FOXD1), and Annexin A4 (ANXA4) were examined by qRT-PCR or Western blot. The DDP resistance, viability, apoptosis, invasion, and migration were determined by CCK8 assay, MTT assay, flow cytometry, TUNEL staining, transwell assay, and wound healing assay. The interaction between FOXD1 and ANXA3 promoter was confirmed by dual-luciferase reporter assay and ChIP assay. Co-IP assay and immunofluorescence staining were used to verify ANXA3 and ANXA4 interaction. The effect of ANXA3 on the DDP resistance of tumor tissues was further confirmed by animal experiments. ANXA3 was highly expressed in lung cancer DDP-resistant tissues and cells. ANXA3 knockdown inhibited lung cancer cell growth and metastasis, thereby improving DDP sensitivity. FOXD1 bound to ANXA3 promoter region to activate its transcription. In rescue experiments, silencing of FOXD1 enhanced the DDP sensitivity of lung cancer cells, and this effect was abolished by ANXA3 overexpression. Moreover, ANXA3 interacted with ANXA4 to promote its expression, and ANXA4 overexpression could reverse the promoting effect of ANXA3 knockdown on DDP sensitivity of lung cancer cells. In addition, FOXD1 positively regulated ANXA4 expression by activating ANXA3. Also, ANXA3 silencing could reduce lung cancer tumorigenesis and enhance DDP sensitivity by decreasing ANXA4 expression in vivo. ANXA3, activated by FOXD1, might contribute to the DDP resistance of lung cancer via regulating ANXA4, providing new ideas for overcoming chemoresistance in lung cancer.

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.

Evidence of an Annexin A4 mediated plasma membrane repair response to biomechanical strain associated with glaucoma pathogenesis

Glaucoma is a common neurodegenerative blinding disease that is closely associated with chronic biomechanical strain at the optic nerve head (ONH). Yet, the cellular injury and mechanosensing mechanisms underlying the resulting damage have remained critically unclear. We previously identified Annexin A4 (ANXA4) from a proteomic analyses of human ONH astrocytes undergoing pathological biomechanical strain that mimics glaucomatous conditions. Annexins are a family of calcium-dependent phospholipid binding proteins with key functions in plasma membrane repair (PMR); an active mechanism to limit and mend cellular injury that involves membrane and cytoskeletal reorganizations. However, a role for direct membrane damage and PMR has not been well studied in the context of biomechanical strain, such as that associated with glaucoma. Here we report that this moderate strain surprisingly damages cell membranes to increase permeability in a calcium-dependent manner, and induces rapid aggregation of ANXA4 at injury sites. ANXA4 loss-of-function increases permeability, while exogenous ANXA4 reduces it. Furthermore, ANXA4 aggregation is associated with F-actin dynamics in vitro, and remarkably this interaction and aggregation signature is also observed in the glaucomatous ONH in patient samples. Together these studies link moderate biomechanical strain with direct membrane damage and actin dynamics, and identify an active PMR role for ANXA4 in new model of cell injury associated with glaucoma pathogenesis.

Metformin impairs cisplatin resistance effects in A549 lung cancer cells through mTOR signaling and other metabolic pathways

Lung cancer is the leading cause of cancer‑associated death worldwide and exhibits intrinsic and acquired therapeutic resistance to cisplatin (CIS). The present study investigated the role of mTOR signaling and other signaling pathways after metformin (MET) treatment in control and cisplatin‑resistant A549 cells, mapping pathways and possible targets involved in CIS sensitivity. MTT, flow cytometry, clonogenic assay, western blotting, proteomic analysis using the Stable Isotope Labeling by Amino acids in Cell culture (SILAC) approach and reverse transcription‑quantitative PCR were performed. The results revealed that CIS treatment induced mTOR signaling pathway overactivation, and the mTOR status was restored by MET. MET and the mTOR inhibitor rapamycin (RAPA) decreased the viability in control and resistant cells, and decreased the cell size increase induced by CIS. In control cells, MET and RAPA decreased colony formation after 72 h and decreased IC₅₀ values, potentiating the effects of CIS. Proteomics analysis revealed important pathways regulated by MET, including transcription, RNA processing and IL‑12‑mediated signaling. In CIS‑resistant cells, MET regulated the apoptotic process, oxidative stress and G₂/M transition. Annexin 4 (ANXA4) and superoxide dismutase 2 (SOD2), involved in apoptosis and oxidative stress, respectively, were chosen to validate the SILAC analysis and may represent potential therapeutic targets for lung cancer treatment. In conclusion, the chemosensitizing and antiproliferative effects of MET were associated with mTOR signaling and with potential novel targets, such as ANXA4 and SOD2, in human lung cancer cells.

Phage Display Technology as a Powerful Platform for Antibody Drug Discovery

Antibody drugs with a high affinity and specificity are effective and safe for intractable diseases, such as cancers and autoimmune diseases. Furthermore, they have played a central role in drug discovery, currently accounting for eight of the top 20 pharmaceutical products worldwide by sales. Forty years ago, clinical trials on antibody drugs that were thought to be a magic bullet failed, partly due to the immunogenicity of monoclonal antibodies produced in mice. The recent breakthrough in antibody drugs is largely because of the contribution of phage display technology. Here, we reviewed the importance of phage display technology as a powerful platform for antibody drug discovery from various perspectives, such as the development of human monoclonal antibodies, affinity enhancement of monoclonal antibodies, and the identification of therapeutic targets for antibody drugs.

Multi-Omics Profiling for NF1 Target Discovery in Neurofibromin (NF1) Deficient Cells

Loss of NF1 is an oncogenic driver. In efforts to define pathways responsible for the development of neurofibromas and other cancers, transcriptomic and proteomic changes are evaluated in a non-malignant NF1 null cell line. NF1 null HEK293 cells were created using CRISPR/Cas9 technology and they are compared to parental cells that express neurofibromin. A total of 1222 genes and 132 proteins are found to be differentially expressed. The analysis is integrated to identify eight transcripts/proteins that are differentially regulated in both analyses. Metacore Pathway analysis identifies Neurogenesis NGF/TrkA MAPK-mediated signaling alterations. Next, the data set is compared with other published studies that involve analysis of cells or tumors deficient for NF1 and it is found that 141 genes recur in the sample and others; only thirteen of these genes recur in two or more studies. Genes/proteins of interest are validated via q-RT-PCR or Western blot. It is shown that KRT8 and 14-3-3σ protein levels respond to exogenously introduced mNf1 cDNA. Hence, transcripts/proteins that respond to neurofibromin levels are identified and they can potentially be used as biomarkers.

Development and Evaluation of Antibody Proteomics Technology for Rapid and Comprehensive Identification of Potential Biomarkers and Therapeutic Targets

Proteomics-based analyses are powerful means of identifying potentially useful proteins in the initial stage of drug development. Technological developments in the field of proteomics, and increases in the sensitivity of MS analyses, now facilitate identification and examination of increasingly small amounts of proteins that are differentially expressed in diseased versus normal tissues and can be candidate biomarkers or therapeutic targets. However, the current approach is for candidate proteins to be prioritized by research interest and then validated one by one; this is very inefficient. To address this issue, we have developed what we refer to as "antibody proteomics technology," which uses a phage antibody library and tissue microarray analysis to rapidly and comprehensively isolate monoclonal antibodies against candidate proteins for the identification of potential biomarkers and therapeutic targets. In our validation of this technology, we successfully identified oxysterol binding protein-like 5 and calumenin as potential biomarkers related to metastasis in lung cancer, annexin A4 as a potential biomarker related to cisplatin resistance in malignant mesothelioma, and Eph receptor A10 as a potential therapeutic target in breast cancer, including refractory breast cancer. These findings suggest that antibody proteomics technology has the potential to become a fundamental technology in drug discovery for the development of novel biomarkers and therapeutic targets.

[Challenge to the Development of Molecular Targeted Therapy against a Novel Target Candidate Identified by Antibody Proteomics Technology]

Disease proteomics that systemically analyzes and identifies differentially expressed proteins between healthy and diseased samples is a potentially useful approach for obtaining target proteins for drug development. To date, however, very few target proteins have been identified from this field. A key issue that remains to be resolved is how to correctly identify target proteins from a number of potential candidates. To circumvent this problem, we have developed "antibody proteomics technology" in which a single chain Fv phage antibody library is utilized for proteome analysis. Here, we describe the application of this technology by primarily focusing on Eph receptor A10 (EphA10), a novel breast cancer-related protein that is a promising target for antibody drugs. To establish an effective and safe targeted cancer therapy, it is important that the target is specifically expressed in cancer tissues. Therefore, we attempted to analyze the EphA10 expression profiles. Tissue microarray analysis showed that EphA10 was expressed in all subtypes of breast cancer containing triple negative breast cancer cases. On the other hand, EphA10 was only expressed in testis tissue among 36 kinds of normal tissues. Thus, EphA10 could be a highly cancer-specific protein, making it a promising target for female breast cancer patients. Finally, we examined the anti-tumor effect by anti-EphA10 antibody, aiming for the development of a novel EphA10 targeting therapy. Administration of the antibody showed that tumor volumes were significantly inhibited. Our results suggest that targeting EphA10 in breast cancer cases might be a promising new form of therapy.

Annexin A4-nuclear factor-κB feedback circuit regulates cell malignant behavior and tumor growth in gallbladder cancer

Gallbladder cancer (GBC) is the most common malignant tumor of the biliary system. However, the mechanisms underlying its tumor initiation, progression, and metastasis are not yet fully understood. The annexin A4 (ANXA4) gene is highly expressed in GBC tissues and may play an important role in the initiation and progression of this disease. In this study, we examined the up-regulation of ANXA4 in human GBC tissues and cell lines. Elevated ANXA4 correlated well with invasion depth in GBC patients and predicted a poor prognosis. In vitro, GBC-SD and NOZ cells with ANXA4 knockdown demonstrated increased apoptosis and inhibited cell growth, migration, and invasion. Interactions between ANXA4 and nuclear factor-κB (NF-κB) p65 proteins were detected. In vivo, ANXA4 knockdown inhibited tumor growth of GBC cells in nude mice and down-regulated the expression of downstream factors in the NF-κB signaling pathway. Taken together, these data indicate that up-regulation of ANXA4 leads to activation of the NF-κB pathway and its target genes in a feedback regulatory mechanism via the p65 subunit, resulting in tumor growth in GBC.

Overexpression of annexin A4 indicates poor prognosis and promotes tumor metastasis of hepatocellular carcinoma

The prognosis of hepatocellular carcinoma (HCC) after surgical resection remains unsatisfactory for the majority of HCC patients who developed early recurrence or metastasis. There is still a lack of reliable biomarkers that can be used to predict the possibility of recurrence/metastasis in HCC patients after operation. In the current study, annexin A4, a calcium-dependent phospholipid-binding protein, has been found to be significantly elevated in HCC patients with early recurrence/metastasis, and had a strong correlation with portal vein tumor thrombosis (p = 0.03) and advanced BCLC stage (p = 0.002). Cox proportional hazards regression analysis revealed that annexin A4 was an independent prognostic predictor for both early recurrence/metastasis (HR = 1.519, p = 0.032) and overall survival (HR = 1.827, p = 0.009) after surgical resection. Meanwhile, Kaplan-Meier analysis showed that Patients with high-expression levels of annexin A4 had higher recurrence rate and shorter overall survival than those with low expression (log-rank test, p < 0.001). Furthermore, in vitro studies have demonstrated that overexpression of annexin A4 facilitated HCC cell migration and invasion via regulating epithelial-mesenchymal transition (EMT). In conclusion, annexin A4 has played important roles in the progression of HCC, and might act as a potential prognostic biomarker for HCC.

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

We recently reported that Fhit is in a molecular complex with annexin A4 (ANXA4); following to their binding, Fhit delocalizes ANXA4 from plasma membrane to cytosol in paclitaxel-resistant lung cancer cells, thus restoring their chemosensitivity to the drug. Here, we demonstrate that Fhit physically interacts with A4 through its N-terminus; molecular dynamics simulations were performed on a 3D Fhit model to rationalize its mechanism of action. This approach allowed for the identification of the QHLIKPS heptapeptide (position 7 to 13 of the wild-type Fhit protein) as the smallest Fhit sequence still able to preserve its ability to bind ANXA4. Interestingly, Fhit peptide also recapitulates the property of the native protein in inhibiting Annexin A4 translocation from cytosol to plasma membrane in A549 and Calu-2 lung cancer cells treated with paclitaxel. Finally, the combination of Tat-Fhit peptide and paclitaxel synergistically increases the apoptotic rate of cultured lung cancer cells and blocks in vivo tumor formation.Our findings address to the identification of chemically simplified Fhit derivatives that mimic Fhit tumor suppressor functions; intriguingly, this approach might lead to the generation of novel anticancer drugs to be used in combination with conventional therapies in Fhit-negative tumors to prevent or delay chemoresistance.

Annexin A4 induces platinum resistance in a chloride-and calcium-dependent manner

Platinum resistance has long been a major issue in the treatment of various cancers. We previously reported that enhanced annexin A4 (ANXA4) expression, a Ca²⁺-regulated phospholipid-binding protein, induces chemoresistance to platinum-based drugs. In this study, we investigated the role of annexin repeats, a conserved structure of all the annexin family, responsible for platinum-resistance as well as the effect of knockdown of ANXA4. ANXA4 knockdown increased sensitivity to platinum-based drugs both in vitro and in vivo. To identify the domain responsible for chemoresistance, ANXA4 deletion mutants were constructed by deleting annexin repeats one by one from the C terminus. Platinum resistance was induced both in vitro and in vivo in cells expressing either full-length ANXA4 or the deletion mutants, containing at least one intact annexin repeat. However, cells expressing the mutant without any calcium-binding sites in the annexin repeated sequence, which is essential for ANXA4 translocation from the cytosol to plasma membrane, failed to acquire platinum resistance. After cisplatin treatment, the intracellular chloride ion concentration, whose channel is partly regulated by ANXA4, significantly increased in the platinum-resistant cells. These findings indicate that the calcium-binding site in the annexin repeat induces chemoresistance to the platinum-based drug by elevating the intracellular chloride concentration.

Annexin A4 and cancer

Annexin A4 (Anxa4) is one of the Ca(2+)-regulated and phospholipid-binding annexin superfamily proteins. Anxa4 has a potential role in diagnosis, prognosis, and treatment of certain cancers. Studies indicate that Anxa4 up-regulation promotes the progression of tumor and chemoresistance of colorectal cancer (CRC), esophageal squamous cell carcinoma (ESCC), endometrial carcinoma (EC), gastric cancer (GC), chemoresistant lung cancer (LC), malignant mesothelioma (MM), renal cell carcinoma (RCC), ovarian clear cell carcinoma (OCCC), cholangiocarcinoma, hepatocellular carcinoma (HCC), breast cancer (BC), and laryngeal cancer. Interestingly, Anxa4 also might specifically function as a tumor suppressor for prostate cancer (PCa) and have a paradoxical role for pancreatic cancer (PCC). Differential expression of Anxa4 may distinguish major salivary gland tumor (MSGT) from thyroid cancer. In addition, its differential expression was linked to Sirt1-induced cisplatin resistance of oral squamous cell carcinoma (OSCC) and miR-7-induced migration and invasion inhibition of glioma. This current review summarizes and discusses the clinical significance of Anxa4 in cancer as well as its potential mechanisms of action. It may provide new integrative understanding for future studies on the exact role of Anxa4 in cancer.

Proteomic analysis of cellular protein expression profiles in response to grass carp reovirus infection

Grass carp (Ctenopharyngodon idella) hemorrhagic disease, caused by grass carp reovirus (GCRV), is emerging as a serious problem in grass carp aquaculture. To better understand the molecular responses to GCRV infection, two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization tandem mass spectroscopy were performed to investigate altered proteins in C. idella kidney (CIK) cells. Differentially expressed proteins in mock infected CIK cells and GCRV-infected CIK cells were compared. Twenty-three differentially expressed spots were identified (22 upregulated spots and 1 downregulated spot), which included cytoskeleton proteins, macromolecular biosynthesis-associated proteins, stress response proteins, signal transduction proteins, energy metabolism-associated proteins and ubiquitin proteasome pathway-associated proteins. Moreover, 10 of the corresponding genes of the differentially expressed proteins were quantified by real-time reverse transcription polymerase chain reaction to examine their transcriptional profiles. The T cell internal antigen 1 (TIA1) and Ras-GTPase-activating SH3-domain-binding protein1 (G3BP1) of the cellular stress granule pathway from grass carp C. idella (designated as CiTIA1 and CiG3BP1) were upregulated and downregulated during GCRV infection, respectively. The full-length cDNA of CiTIA1 was 2753 bp, with an open reading frame (ORF) of 1155bp, which encodes a putative 385-amino acid protein. The 2271 bp full-length cDNA of CiG3BP1 comprised an ORF of 1455 bp that encodes a putative 485-amino acid protein. Phylogenetic analysis revealed that the complete ORFs of CiTIA1 and CiG3BP1 were very similar to zebrafish and well-characterized mammalian homologs. The expressions of the cellular proteins CiTIA1 and CiG3BP1 in response to GCRV were validated by western blotting, which indicated that the GCRV should unlink TIA1 aggregation and stress granule formation. This study provides useful information on the proteomic and cellular stress granule pathway's responses to GCRV infection, which adds to our understanding of viral pathogenesis.

Identification and evaluation of metastasis-related proteins, oxysterol binding protein-like 5 and calumenin, in lung tumors

Metastasis is an important prognosis factor in lung cancer, therefore, it is imperative to identify target molecules and elucidate molecular mechanism of metastasis for developing new therapeutics and diagnosis methods. We searched for metastasis-related proteins by utilizing a novel antibody proteome technology developed in our laboratory that facilitated efficient screening of useful target proteins. Two-dimensional differential in-gel electrophoresis (2D-DIGE) analysis identified sixteen proteins, which were highly expressed in metastatic lung cancer cells, as protein candidates. Monoclonal single-chain variable fragments (scFvs) binding to candidates were isolated from a scFv-displaying phage library by affinity selection. Tissue microarray analysis of scFvs binding to candidates revealed that oxysterol binding protein-like 5 (OSBPL5) and calumenin (CALU) were expressed at a significantly higher levels in the lung tissues of metastasis-positive cases than that in the metastasis-negative cases (OSBPL5; p=0.0156, CALU; p=0.0055). Furthermore, 80% of OSBPL5 and CALU double-positive cases were positive for lymph node metastasis. Consistent with these observations, overexpression of OSBPL5 and CALU promoted invasiveness of lung cancer cells. Conversely, knockdown of these proteins using respective siRNAs reversed the invasiveness of the lung cancer cells. Moreover, these proteins were expressed in lung tumor tissues, but not in normal lung tissues. In conclusion, OSBPL5 and CALU are related to metastatic potential of lung cancer cells, and they could be useful targets for cancer diagnosis and also for development of drugs against metastasis.

A quantitative proteomics-based signature of platinum sensitivity in ovarian cancer cell lines

Although DNA encodes the molecular instructions that underlie the control of cell function, it is the proteins that are primarily responsible for implementing those instructions. Therefore quantitative analyses of the proteome would be expected to yield insights into important candidates for the detection and treatment of disease. We present an iTRAQ (isobaric tag for relative and absolute quantification)-based proteomic analysis of ten ovarian cancer cell lines and two normal ovarian surface epithelial cell lines. We profiled the abundance of 2659 cellular proteins of which 1273 were common to all 12 cell lines. Of the 1273, 75 proteins exhibited elevated expression and 164 proteins had diminished expression in the cancerous cells compared with the normal cell lines. The iTRAQ expression profiles allowed us to segregate cell lines based upon sensitivity and resistance to carboplatin. Importantly, we observed no substantial correlation between protein abundance and RNA expression or epigenetic DNA methylation data. Furthermore, we could not discriminate between sensitivity and resistance to carboplatin on the basis of RNA expression and DNA methylation data alone. The present study illustrates the importance of proteomics-based discovery for defining the basis for the carboplatin response in ovarian cancer and highlights candidate proteins, particularly involved in cellular redox regulation, homologous recombination and DNA damage repair, which otherwise could not have been predicted from whole genome and expression data sources alone.

Annexin A4 is a promising therapeutic target for the treatment of platinum-resistant cancers

INTRODUCTION

Platinum drugs are widely used for the treatment of testicular, bladder, ovarian, colorectal, lung and prostate cancers. With regard to ovarian cancer in particular, the prognosis is poor for tumours that are (or have become) platinum-resistant. Determining the mechanism underlying platinum resistance may aid in the identification of therapeutic targets for the treatment of platinum-resistant tumours.

AREAS COVERED

This review gives an overview of the characteristics and functions of Annexin (Anx) A4, the mechanism of Anx A4-induced platinum resistance, the association between platinum resistance and platinum transporters, recent reports that Anx A4 overexpression promotes the efflux of platinum drugs via platinum transporters and the association between other Anxs and chemoresistance. The reader will gain an understanding of recent studies on the mechanism of Anx A4-induced chemoresistance. Anx A4 represents a therapeutic target for the treatment of Anx A4-overexpressing platinum-resistant tumours.

EXPERT OPINION

Anx A4 is overexpressed in ovarian clear cell carcinoma (CCC), and enhanced Anx A4 expression induces platinum resistance. Recent studies showed that Anx A4 is also associated with platinum resistance in cancers other than ovarian CCC. Furthermore, other Anxs are reportedly associated with chemoresistance, suggesting a relationship between the Anx family and chemoresistance.

Annexin a5 as a new potential biomarker for Cisplatin-induced toxicity in human kidney epithelial cells

Cisplatin is a member of platinum-containing anti-cancer drugs that causes cross-linking of DNA and ultimately cancer cell apoptosis. The therapeutic function of cisplatin on various types of cancers has been widely reported but the side effects have been discovered together and nephrotoxicity has been regarded as major side effect of cisplatin. To select candidates for new sensitive nephrotoxicity biomarker, we performed proteomic analysis using 2-DE/MALDI-TOF-MS followed by cisplatin treatment in human kidney cell line, HK-2 cells, and compared the results to the gene profi le from microarray composed of genes changed in expression by cisplatin from formerly reported article. Annexin A5 has been selected to be the most potential candidate and it has been identifi ed using Western blot, RT-PCR and cell viability assay whether annexin A5 is available to be a sensitive nephrotoxic biomarker. Treatment with cisplatin on HK-2 cells caused the increase of annexin A5 expression in protein and mRNA levels. Overexpression of annexin A5 blocked HK-2 cell proliferation, indicating correlation between annexin A5 and renal cell toxicity. Taken together, these results suggest the possibility of annexin A5 as a new biomarker for cisplatin-mediated nephrotoxicity.

Sorafenib sensitizes hepatocellular carcinoma cell to cisplatin via suppression of Wnt/β-catenin signaling

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Systemic chemotherapy plays an important role in the treatment of patients with advanced liver cancer. However, chemoresistance to cisplatin is a major limitation of cisplatin-based chemotherapy in the clinic, and the underlying mechanism of such resistance is not fully understood. In this study, we found that nuclear accumulation of β-catenin was higher in cisplatin-resistant Huh7 cells than in Huh7 cells, indicating that Wnt signaling was activated in cisplatin-resistant cells. Wnt signaling inhibition increased cisplatin-induced growth inhibition in hepatoma cell. We further demonstrated that sorafenib could inhibit Wnt signaling in Huh7 cells and cisplatin-resistant Huh7 cells. Co-treatment with cisplatin and sorafenib was more effective in inhibiting cancer cell proliferation than cisplatin alone in vitro and in vivo, whereas Wnt3a (Wnt activator) treatment abrogated sorafenib-induced growth inhibition. These data demonstrated that sorafenib sensitizes human HCC cell to cisplatin via suppression of Wnt/β-catenin signaling, thus offering a new target for chemotherapy of HCC.

Revealing the molecular mechanism of gastric cancer marker annexin A4 in cancer cell proliferation using exon arrays

Gastric cancer is a malignant disease that arises from the gastric epithelium. A potential biomarker for gastric cancer is the protein annexin A4 (ANXA4), an intracellular Ca²⁺ sensor. ANXA4 is primarily found in epithelial cells, and is known to be involved in various biological processes, including apoptosis, cell cycling and anticoagulation. In respect to cancer, ANXA4-overexpression has been observed in cancers of various origins, including gastric tumors associated with Helicobacter pylori infection. H. pylori induces ANXA4 expression and intracellular [Ca²⁺]_i elevation, and is an important risk factor for carcinogenesis that results in gastric cancer. Despite this correlation, the role of ANXA4 in the progression of gastric tumors remains unclear. In this study, we have investigated whether ANXA4 can mediate the rate of cell growth and whether ANXA4 downstream signals are involved in tumorigenesis. After observing the rate of cell growth in real-time, we determined that ANXA4 promotes cell proliferation. The transcription gene profile of ANXA4-overexpressing cells was measured and analyzed by human exon arrays. From this transcriptional gene data, we show that overexpression of ANXA4 regulates genes that are known to be related to cancer, for example the activation of hyaluronan mediated motility receptor (RHAMM), AKT, and cyclin-dependent kinase 1 (CDK1) as well as the suppression of p21. The regulation of these genes further induces cancer cell proliferation. We also found Ca²⁺ could regulate the transmission of downstream signals by ANXA4. We suggest that ANXA4 triggers a signaling cascade, leading to increased epithelial cell proliferation, ultimately promoting carcinogenesis. These results might therefore provide a new insight for gastric cancer therapy, specifically through the modification of ANXA4 activity.