Alpha-Actinin 4 Is Associated with Cancer Cell Motility and Is a Potential Biomarker in Non–Small Cell Lung Cancer

Live-cell imaging and CLEM reveal the existence of ACTN4-dependent ruffle-edge lamellipodia acting as a novel mode of cell migration

α-Actinin-4 (ACTN4) expression levels are correlated with the invasive and metastatic potential of cancer cells; however, the underlying mechanism remains unclear. Here, we identified ACTN4-localized ruffle-edge lamellipodia using live-cell imaging and correlative light and electron microscopy (CLEM). BSC-1 cells expressing EGFP-ACTN4 showed that ACTN4 was most abundant in the leading edges of lamellipodia, although it was also present in stress fibers and focal adhesions. ACTN4 localization in lamellipodia was markedly diminished by phosphoinositide 3-kinase inhibition, whereas its localization in stress fibers and focal adhesions remained. Furthermore, overexpression of ACTN4, but not ACTN1, promoted lamellipodial formation. Live-cell analysis demonstrated that ACTN4-enriched lamellipodia are highly dynamic and associated with cell migration. CLEM revealed that ACTN4-enriched lamellipodia exhibit a characteristic morphology of multilayered ruffle-edges that differs from canonical flat lamellipodia. Similar ruffle-edge lamellipodia were observed in A549 and MDA-MB-231 invasive cancer cells. ACTN4 knockdown suppressed the formation of ruffle-edge lamellipodia and cell migration during wound healing in A549 monolayer cultures. Additionally, membrane-type 1 matrix metalloproteinase was observed in the membrane ruffles, suggesting that ruffle-edge lamellipodia have the ability to degrade the extracellular matrix and may contribute to active cell migration/invasion in certain cancer cell types.

Nuclear α-actinin-4 regulates breast cancer invasiveness and EMT

Epithelial-to-mesenchymal transition (EMT) is a key process where cells lose their adhesion properties and augment their invasive properties. α-Actinin4 (ACTN4) is an actin crosslinking protein that responds to mechanical stimuli and is found to be elevated in breast cancer patients. While ACTN4 has been implicated in regulating cancer invasiveness by modulating cytoskeletal organization, its nuclear functions remain much less explored. Here we address this question by first establishing a correlation between nuclear localization and invasiveness in breast cancer cells. Using cancer databases, we then establish a correlation between ACTN4 expression and EMT in breast cancer. Interestingly, TGFβ-induced EMT induction in MCF10A normal mammary epithelial cells leads to increased ACTN4 expression and nuclear enrichment. We then show that ACTN4 knockdown in MDA-MB-231 breast cancer cells, which harbor sizeable fraction of nuclear ACTN4, leads to reduced invasiveness and loss of mesenchymal traits. Similar behavior was observed in knockdown cells expressing K255E ACTN4, which is primarily localized to the cytosol. Together, our findings establish a role for nuclear ACTN4 in regulating invasiveness via modulation of EMT.

KLF5 regulates actin remodeling to enhance the metastasis of nasopharyngeal carcinoma

Transcription factors (TFs) engage in various cellular essential processes including differentiation, growth and migration. However, the master TF involved in distant metastasis of nasopharyngeal carcinoma (NPC) remains largely unclear. Here we show that KLF5 regulates actin remodeling to enhance NPC metastasis. We analyzed the msVIPER algorithm-generated transcriptional regulatory networks and identified KLF5 as a master TF of metastatic NPC linked to poor clinical outcomes. KLF5 regulates actin remodeling and lamellipodia formation to promote the metastasis of NPC cells in vitro and in vivo. Mechanistically, KLF5 preferentially occupies distal enhancer regions of ACTN4 to activate its transcription, whereby decoding the informative DNA sequences. ACTN4, extensively localized within actin cytoskeleton, facilitates dense and branched actin networks and lamellipodia formation at the cell leading edge, empowering cells to migrate faster. Collectively, our findings reveal that KLF5 controls robust transcription program of ACTN4 to modulate actin remodeling and augment cell motility which enhances NPC metastasis, and provide new potential biomarkers and therapeutic interventions for NPC.

Disulfidptosis-related signature elucidates the prognostic, immunologic, and therapeutic characteristics in ovarian cancer

Introduction

Ovarian cancer (OC) is the deadliest malignancy in gynecology, but the mechanism of its initiation and progression is poorly elucidated. Disulfidptosis is a novel discovered type of regulatory cell death. This study aimed to develop a novel disulfidptosis-related prognostic signature (DRPS) for OC and explore the effects and potential treatment by disulfidptosis-related risk stratification.

Methods

The disulfidptosis-related genes were first analyzed in bulk RNA-Seq and a prognostic nomogram was developed and validated by LASSO algorithm and multivariate cox regression. Then we systematically assessed the clinicopathological and mutational characteristics, pathway enrichment analysis, immune cell infiltration, single-cell-level expression, and drug sensitivity according to DRPS.

Results

The DRPS was established with 6 genes (MYL6, PDLIM1, ACTN4, FLNB, SLC7A11, and CD2AP) and the corresponding prognostic nomogram was constructed based on the DRPS, FIGO stage, grade, and residual disease. Stratified by the risk score derived from DRPS, patients in high-risk group tended to have worse prognosis, lower level of disulfidptosis, activated oncogenic pathways, inhibitory tumor immune microenvironment, and higher sensitivity to specific drugs including epirubicin, stauroporine, navitoclax, and tamoxifen. Single-cell transcriptomic analysis revealed the expression level of genes in the DRPS significantly varied in different cell types between tumor and normal tissues. The protein-level expression of genes in the DRPS was validated by the immunohistochemical staining analysis.

Conclusion

In this study, the DRPS and corresponding prognostic nomogram for OC were developed, which was important for OC prognostic assessment, tumor microenvironment modification, drug sensitivity prediction, and exploration of potential mechanisms in tumor development.

A novel disulfidptosis-related prognostic gene signature and experimental validation identify ACTN4 as a novel therapeutic target in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) is a prevalent form of malignancy globally. Disulfidptosis is novel programmed cell death pathway based on disulfide proteins, may have a positive impact on the development of LUAD treatment strategies.

OBJECTIVE

To investigate the impact of disulfidptosis-related genes (DRGs) on the prognosis of LUAD, developed a risk model to facilitate the diagnosis and prognostication of patients. We also explored ACTN4 (DRGs) as a new therapeutic biomarker for LUAD.

METHODS

We investigated the expression patterns of DRGs in both LUAD and noncancerous tissues. To assess the prognostic value of the DRGs, we developed risk models through univariate Cox analysis and lasso regression. The expression and function of ACTN4 was evaluated by qRT-PCR, immunohistochemistry and in vitro experiments. The TIMER examined the association between ACTN4 expression and immune infiltration in LUAD.

RESULTS

Ten differentially expressed DRGs were identified. And ACTN4 was identified as potential risk factors through univariate Cox regression analysis (P< 0.05). ACTN4 expression and riskscore were used to construct a risk model to predict overall survival in LUAD, and high-risk demonstrated a significantly higher mortality rate compared to the low-risk cohort. qRT-PCR and immunohistochemistry assays indicated ACTN4 was upregulated in LUAD, and the upregulation was associated with clinicopathologic features. In vitro experiments showed the knockdown of ACTN4 expression inhibited the proliferation in LUAD cells. The TIMER analysis demonstrated a correlation between the expression of ACTN4 and the infiltration of diverse immune cells. Elevated ACTN4 expression was associated with a reduction in memory B cell count. Additionally, the ACTN4 expression was associated with m6A modification genes.

CONCLUSIONS

Our study introduced a prognostic model based on DRGs, which could forecast the prognosis of patients with LUAD. The biomarker ACTN4 exhibits promise for the diagnosis and management of LUAD, given its correlation with tumor immune infiltration and m6A modification.

LncRNA TP73-AS1 Exacerbates the Non-Small-Cell Lung Cancer (NSCLC) Process via Regulating miR-125a-3p-Mediated ACTN4

Background

LncRNA TP73-AS1 has been revealed to exert a noteworthy impact on the occurrence and advancement of different cancers. In this study, we explored the function of TP73-AS1 in tumor growth, cell progression as well as the relevant molecular mechanism in non-small-cell lung cancer (NSCLC).

Methods

QRT-PCR was employed to assess the expression of TP73-AS1, miR‐125a-3p, and actinin alpha 4 (ACTN4) in NSCLC cells. The biological effect of TP73-AS1 on NSCLC cells was assessed by cell transfection, CCK8, and transwell experiments. We further predicted the interaction among RNAs (TP73-AS1, miR-125a-3p, and ACTN4) through bioinformatics online tools and verified via luciferase reporter, RNA immunoprecipitation, and qRT-PCR assays. Xenograft models of SPC-A1 cells were conducted to test how TP73-AS1 regulates tumorigenesis. Western blot, as well as the immunohistochemistry (IHC) assays, was utilized to measure the expression levels. Functions of TP73-AS1 in NSCLC progression through the miR-125a-3p/ACTN4 axis were investigated by rescue experiments.

Results

Knockdown of TP73-AS1 suppressed the growth and simultaneously attenuated the migration and invasion ability of NSCLC SPC-A1 and A549 cells. Bioinformatics and molecular mechanism assays demonstrated that TP73-AS1 could bind to miR-125a-3p/ACTN4 and regulate their expression. Moreover, the rescued‐function experiment demonstrated that suppressing miR-125a-3p or elevating ACTN4 turned around the suppression effect of sh-TP73-AS1 on NSCLC progression. TP73-AS1 inhibition could also inhibit the NSCLC tumor growth and correspondingly regulated the expression of miR-125a-3p and ACTN4 in the tumor xenograft model.

Conclusion

The present study indicated that TP73-AS1 affects NSCLC progression through a new competitive RNA (ceRNA) regulatory network of miR-125a-3p/ACTN4, providing an underlying target for NSCLC treatment in the future.

RNF38 suppress growth and metastasis via ubiquitination of ACTN4 in nasopharyngeal carcinoma

Background

Accumulated evidence suggests that RING finger proteins (RNFs) are involved in the carcinogenesis of cancers. However, RNF38, a member of the RNF protein family, has not been studied in nasopharyngeal carcinoma (NPC).

Methods

RNF38 expression was analyzed by RT-PCR, Western blotting and Immunohistochemistry. Biological functions of RNF38 were evaluated by cell growth, colony formation, apoptosis, migration and invasion assays in vitro. Xenograft growth and lung metastasis models were conducted to investigate the effect of RNF38 in vivo. Liquid chromatography coupled with tandem mass spectrometry, co-immunoprecipitation, and CHX assay were implemented to detect the interaction among RNF38 and ACTN4.

Results

RNF38 was significantly downregulated in NPC cells and tissues. Immunohistochemistry implied that loss of RNF38 was an independent prognostic factor for poor outcomes of NPC patients. Gain- and loss-of-function experiments showed that RNF38 inhibited proliferation and metastasis in NPC in vitro and in vivo. Upregulation of RNF38 promoted apoptosis of NPC cells to etoposide but not cisplatin. ACTN4 was upregulated in NPC and negatively correlated with RNF38. Mechanistic investigations suggested that RNF38 inactivates the NF-𝛋B and ERK1/2 signaling pathways by inducing ubiquitination and degradation of ACTN4. RNF38 suppress the development of NPC by interacting with ACTN4.

Conclusions

RNF38 plays a potential cancer suppressor gene role in NPC tumorigenesis and is a prognostic biomarker in NPC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09641-x.

Microfluidic Determination of Distinct Membrane Transport Properties between Lung Adenocarcinoma Cells CL1-0 and CL1-5

The cell membrane permeability of a cell type to water (Lp) and cryoprotective agents (Ps), is the key factor that determines the optimal cooling and mass transportation during cryopreservation. The human lung adenocarcinoma cell line, CL1, has been widely used to study the invasive capabilities or drug resistance of lung cancer cells. Therefore, providing accurate databases of the mass transport properties of this specific cell line can be crucial for facilitating either flexible and optimal preservation, or supply. In this study, utilizing our previously proposed noncontact-based micro-vortex system, we focused on comparing the permeability phenomenon between CL1-0 and its more invasive subline, CL1-5, under several different ambient temperatures. Through the assay procedure, the cells of favor were virtually trapped in a hydrodynamic circulation to provide direct inspection using a high-speed camera, and the images were then processed to achieve the observation of a cell’s volume change with respect to time, and in turn, the permeability. Based on the noncontact nature of our system, we were able to manifest more accurate results than their contact-based counterparts, excluding errors involved in estimating the cell geometry. As the results in this experiment showed, the transport phenomena in the CL1-0 and CL1-5 cell lines are mainly composed of simple diffusion through the lipid bilayer, except for the case where CL1-5 were suspended in the cryoprotective agent (CPA) solution, which also demonstrated higher Ps values. The deviated behavior of CL1-5 might be a consequence of the altered expression of aquaporins and the coupling of a cryoprotective agent and water, and has given a vision on possible studies over these properties, and their potential relationship to invasiveness and metastatic stability of the CL1 cell line.

ACTN4 gene amplification is a predictive biomarker for adjuvant chemotherapy with UFT in stage I lung adenocarcinomas

Although adjuvant tegafur/uracil (UFT) is recommended for patients with completely resected stage I non‐small‐cell lung cancer (NSCLC) in Japan, only one‐third of cases has received adjuvant chemotherapy (ADJ) according to real‐world data. Therefore, robust predictive biomarkers for selecting ADJ or observation (OBS) without ADJ are needed. Patients who underwent complete resection of stage I lung adenocarcinoma with or without adjuvant UFT were enrolled. The status of ACTN4 gene amplification was analyzed by FISH. Statistical analyses to determine whether the status of ACTN4 gene amplification affected recurrence‐free survival (RFS) were carried out. Formalin‐fixed, paraffin‐embedded samples from 1136 lung adenocarcinomas were submitted for analysis of ACTN4 gene amplification. Ninety‐nine (8.9%) of 1114 cases were positive for ACTN4 gene amplification. In the subgroup analysis of patients aged 65 years or older, the ADJ group had better RFS than the OBS group in the ACTN4‐positive cohort (hazard ratio [HR], 0.084, 95% confidence interval [CI], 0.009‐0.806; P = .032). The difference in RFS between the ADJ group and the OBS group was not significant in ACTN4‐negative cases (all ages: HR, 1.214; 95% CI, 0.848‐1.738; P = .289). Analyses of ACTN4 gene amplification contributed to the decision regarding postoperative ADJ for stage I lung adenocarcinomas, preventing recurrence, improving the quality of medical care, preventing the unnecessary side‐effects of ADJ, and saving medical costs.

α-actinin-4 drives invasiveness by regulating myosin IIB expression and myosin IIA localization

The mechanisms by which the mechanoresponsive actin crosslinking protein α-actinin-4 (ACTN4) regulates cell motility and invasiveness remains incompletely understood. Here we show that in addition to regulating protrusion dynamics and focal adhesion formation, ACTN4 transcriptionally regulates expression of non-muscle myosin IIB (NMM IIB), which is essential for mediating nuclear translocation during 3D invasion. We further show that an indirect association between ACTN4 and NMM IIA mediated by a functional F-actin cytoskeleton is essential for retention of NMM IIA at the cell periphery and modulation of focal adhesion dynamics. A protrusion-dependent model of confined migration recapitulating experimental observations predicts a dependence of protrusion forces on the degree of confinement and on the ratio of nucleus to matrix stiffness. Together, our results suggest that ACTN4 is a master regulator of cancer invasion that regulates invasiveness by controlling NMM IIB expression and NMM IIA localization.

Metastasis suppressor 1 interacts with α-actinin 4 to affect its localization and regulate formation of membrane ruffling

Membrane ruffling plays an important role in the directed cell migration and escape of tumor cells from the monolayer. Metastasis suppressor 1 (MTSS1), also known as missing in metastasis, has been implicated in cell morphology, motility, metastasis, and development. Here, the dynamic interaction proteins associated with MTSS1 and involved in membrane ruffling were determined by cross-linking and mass spectrometry analysis. We identified α-actinin 4 (ACTN4) as an interacting protein and confirmed a direct interaction between MTSS1 and ACTN4. Moreover, co-expression of MTSS1 in fibroblasts recruited cytoplasmic ACTN4 to the cell periphery, at which point ruffling became thick and rigid. In MCF-7 cells, MTSS1 knockdown did not show an obvious effect on the cell shape or the distribution of endogenous ACTN4; however, ACTN4 overexpression transformed cell morphology from an epidermal- to a fibroblast-like shape, and further MTSS1 depletion significantly increased the ratio of fibroblast cells exhibiting prominent ruffling. Furthermore, biochemical data suggested that MTSS1 cross-linking with ACTN4 induced the formation of actin fiber bundles into more organized structures in vitro. These data indicated that MTSS1 might recruit cytoplasmic ACTN4 to the cell periphery and regulate cytoskeleton dynamics to restrict its performance in membrane ruffling.

Distinct forms of the actin cross-linking protein α-actinin support macropinosome internalization and trafficking

The α-actinin family of actin cross-linking proteins have been implicated in driving tumor cell metastasis through regulation of the actin cytoskeleton; however, there has been little investigation into whether these proteins can influence tumor cell growth. We demonstrate that α-actinin 1 and 4 are essential for nutrient uptake through the process of macropinocytosis in pancreatic ductal adenocarcinoma (PDAC) cells, and inhibition of these proteins decreases tumor cell survival in the presence of extracellular protein. The α-actinin proteins play essential roles throughout the macropinocytic process, where α-actinin 4 stabilizes the actin cytoskeleton on the plasma membrane to drive membrane ruffling and macropinosome internalization and α-actinin 1 localizes to actin tails on macropinosomes to facilitate trafficking to the lysosome for degradation. In addition to tumor cell growth, we also observe that the α-actinin proteins can influence uptake of chemotherapeutics and extracellular matrix proteins through macropinocytosis, suggesting that the α-actinin proteins can regulate multiple tumor cell properties through this endocytic process. In summary, these data demonstrate a critical role for the α-actinin isoforms in tumor cell macropinocytosis, thereby affecting the growth and invasive potential of PDAC tumors.

Proteomic Analyses of Fibroblast- and Serum-Derived Exosomes Identify QSOX1 as a Marker for Non-invasive Detection of Colorectal Cancer

Simple Summary

Early diagnosis of colorectal cancer (CRC) is crucial to improve patient outcomes. The tumour microenvironment immediately adapts to malignant transformations, including the activation of fibroblasts in the connective tissue nearby. In this study, we investigated fibroblast activity-related protein secretion via extracellular vesicles (EVs). QSOX1, a protein identified to be significantly reduced in activated fibroblasts and derived EVs, was also found to be significantly reduced in circulating blood plasma EVs of CRC patients as compared to control patients. Hence, blood plasma EV-associated QSOX1 represents a promising platform for diagnostic CRC screening.

Abstract

The treatment of colorectal cancer (CRC) has improved during the last decades, but methods for crucial early diagnosis are yet to be developed. The influence of the tumour microenvironment on liquid biopsies for early cancer diagnostics are gaining growing interest, especially with emphasis on exosomes (EXO), a subgroup of extracellular vesicles (EVs). In this study, we established paired cancer-associated (CAFs) and normal fibroblasts (NF) from 13 CRC patients and investigated activation status-related protein abundance in derived EXOs. Immunohistochemical staining of matched patient tissue was performed and an independent test cohort of CRC patient plasma-derived EXOs was assessed by ELISA. A total of 11 differentially abundant EV proteins were identified between NFs and CAFs. In plasma EXOs, the CAF-EXO enriched protein EDIL3 was elevated, while the NF-EXO enriched protein QSOX1 was diminished compared to whole plasma. Both markers were significantly reduced in patient-matched CRC tissue compared to healthy colon tissue. In an independent test cohort, a significantly reduced protein abundance of QSOX1 was observed in plasma EXOs from CRC patients compared to controls and diagnostic ROC curve analysis revealed an AUC of 0.904. In conclusion, EXO-associated QSOX1 is a promising novel marker for early diagnosis and non-invasive risk stratification in CRC.

Proteomic Analyses of Fibroblast- and Serum-Derived Exosomes Identify QSOX1 as a Marker for Non-invasive Detection of Colorectal Cancer

The treatment of colorectal cancer (CRC) has improved during the last decades, but methods for crucial early diagnosis are yet to be developed. The influence of the tumour microenvironment on liquid biopsies for early cancer diagnostics are gaining growing interest, especially with emphasis on exosomes (EXO), a subgroup of extracellular vesicles (EVs). In this study, we established paired cancer-associated (CAFs) and normal fibroblasts (NF) from 13 CRC patients and investigated activation status-related protein abundance in derived EXOs. Immunohistochemical staining of matched patient tissue was performed and an independent test cohort of CRC patient plasma-derived EXOs was assessed by ELISA. A total of 11 differentially abundant EV proteins were identified between NFs and CAFs. In plasma EXOs, the CAF-EXO enriched protein EDIL3 was elevated, while the NF-EXO enriched protein QSOX1 was diminished compared to whole plasma. Both markers were significantly reduced in patient-matched CRC tissue compared to healthy colon tissue. In an independent test cohort, a significantly reduced protein abundance of QSOX1 was observed in plasma EXOs from CRC patients compared to controls and diagnostic ROC curve analysis revealed an AUC of 0.904. In conclusion, EXO-associated QSOX1 is a promising novel marker for early diagnosis and non-invasive risk stratification in CRC.

Binding of alpha-ACTN4 to EGF receptor enables its rapid phosphorylation

Alpha-ACTN4, a member of alpha-actinin family is critical for cell motility through its regulated binding of actin filaments. We previously found that EGF exposure of cells triggers the tyrosyl-phosphorylation of ACTN4 in fibroblasts that dramatically downregulates its binding to actin filaments. However, the exact kinase remained uncertain. In the present study, we report that the phosphorylation of ACTN4 occurs within seconds upon EGF treatments and is accomplished via direct interaction of ACTN4 with the EGF receptor. The major binding domain of ACTN4 for EGF receptor is mapped to the N-terminal 32 amino acids. A second domain minimizes the interaction, as truncation of the C-terminal tail enhances ACTN4 binding to EGF receptor. A mimetic phosphorylated ACTN4, Y4/31E, presents low binding to EGF receptor. Overexpression of EGF receptor in melanoma cell lines, also accomplishes the phosphorylation of ACTN4 in the presence of EGF. These findings suggest that the binding of ACTN4 to EGFR enables its direct and rapid phosphorylation resulting in dissociation from EGFR and decreased binding to actin filaments.

Serum Actinin-4 Levels as a Potential Diagnostic and Prognostic Marker in Cervical Cancer

Purpose

The present study was aimed at determining the serum levels of actinin-4 (ACTN4) in cervical cancer (CC) and investigating the diagnostic and prognostic value of serum ACTN4 in CC.

Materials and Methods

We included 93 CC patients, 52 cervical intraepithelial neoplasia (CIN) patients, and 70 healthy women. Serum ACTN4 levels were assessed using an ELISA method. A receiver operating characteristic (ROC) curve was performed to evaluate the diagnostic value of serum ACTN4. The survival curves were used to display the overall survival distributions.

Results

Serum ACTN4 levels in CC patients were 48.39 ± 13.98 pg/mL which is significantly higher than those in CIN patients (32.72 ± 9.44 pg/mL; P < 0.001) and those in healthy controls (30.84 ± 8.08 pg/mL; P < 0.001). The ROC analysis demonstrated that the area under the curve (AUC) of ACTN4 was 0.852 (95%CI = 0.796-0.908), with sensitivity of 76.3% and specificity of 87.7%. Serum ACTN4 levels were associated with the FIGO stage, lymph node metastasis, and lymphovascular space invasion of CC (all P < 0.05). The survival curve suggested that high serum ACTN4 levels were related to poor prognosis.

Conclusion

Our findings suggest that serum ACTN4 levels may be valuable diagnostic and prognostic biomarkers for CC.

Prognostic impact of ACTN4 gene copy number alteration in hormone receptor-positive, HER2-negative, node-negative invasive breast carcinoma

BACKGROUND

Most patients with hormone receptor (HR)-positive, human epidermal growth factor receptor type 2 (HER2)-negative breast cancer can be cured by surgery and endocrine therapy, but a significant proportion suffer recurrences. Actinin-4 is associated with cancer invasion and metastasis, and its genetic alteration may be used for breast cancer prognostication.

METHODS

The copy number of the actinin-4 (ACTN4) gene was determined by fluorescence in situ hybridisation (FISH) in two independent cohorts totalling 597 patients (336 from Japan and 261 from the USA) with HR-positive, HER2-negative, node-negative breast cancer.

RESULTS

In the Japanese cohort, multivariate analysis revealed that a copy number increase (CNI) of ACTN4 was an independent factor associated with high risks of recurrence (P = 0.01; hazard ratio (HR), 2.95) and breast cancer death (P = 0.014; HR, 4.27). The prognostic significance of ACTN4 CNI was validated in the US cohort, where it was the sole prognostic factor significantly associated with high risks of recurrence (P = 0.04; HR, 2.73) and death (P = 0.016; HR, 4.01).

CONCLUSIONS

Copy number analysis of a single gene, ACTN4, can identify early-stage luminal breast cancer patients with a distinct outcome. Such high-risk patients may benefit from adjuvant chemotherapy.

IMPAD1 functions as mitochondrial electron transport inhibitor that prevents ROS production and promotes lung cancer metastasis through the AMPK-Notch1-HEY1 pathway

The tumor microenvironment (TME) and metabolic reprogramming have been implicated in cancer development and progression. However, the link between TME, metabolism, and cancer progression in lung cancer is unclear. In the present study, we identified IMPAD1 from the conditioned medium of highly invasive CL1-5. High expression of IMPAD1 was associated with a poorer clinical phenotype in lung cancer patients, with reduced survival and increased lymph node metastasis. Knockdown of IMPAD1 significantly inhibited migration/invasion abilities and metastasis in vitro and in vivo. Upregulation of IMPAD1 and subsequent accumulation of AMP in cells increased the pAMPK, leading to Notch1 and HEY1 upregulation. As AMP is an ADORA1 agonist, treatment with ADORA1 inhibitor reduced the expression of pAMPK and HEY1 expression in IMPAD1-overexpressing cells. IMPAD1 caused mitochondria dysfunction by inhibiting mitochondrial Complex I activity, which reduced mitochondrial ROS levels and activated the AMPK-HEY1 pathway. Collectively this study supports the multipotent role of IMPAD1 in promotion of lung cancer metastasis by simultaneously increasing AMP levels, inhibition of Complex I activity to decrease ROS levels, thereby activating AMPK-Notch1-HEY1 signaling, and providing an alternative metabolic pathway in energy stress conditions.

The role of actinin-4 (ACTN4) in exosomes as a potential novel therapeutic target in castration-resistant prostate cancer

Prostate cancer is the second leading cause of cancer death in men in the United States. Several novel therapeutic agents have been developed for castration-resistant prostate cancer (CRPC), but the prognosis for patients with CRPC remains poor. The identification of novel therapeutic targets for CRPC is an urgent issue. Exosomes are small vesicles secreted by a variety of cells, and exosomes derived from cancer cells have been reported to circulate in the patient's bodily fluids, promoting metastasis and invasion. We aimed to identify novel therapeutic targets for CRPC by proteomic analysis of serum exosomes. Exosomes were isolated by ultracentrifugation of sera from 36 men with metastatic prostate cancer: untreated (n = 8), well-controlled with primary androgen deprivation therapy (ADT) (n = 8), and CRPC (n = 20). We identified 823 proteins in the serum exosomes. Six proteins were increased in CRPC patients compared with untreated patients. In contrast, only ACTN4 was increased in the CRPC patients compared to the ADT patients. We focused on ACTN4 as a candidate for targeted therapeutics. ACTN4 was highly expressed in the prostate cancer cell line DU145 as well as exosomes from this line. RNA interference-mediated downregulation of ACTN4 significantly attenuated cell proliferation and invasion in DU145 cells. ACTN4 could be a potential therapeutic target for CRPC.

Role of ACTN4 in Tumorigenesis, Metastasis, and EMT

The actin-binding protein ACTN4 belongs to a family of actin-binding proteins and is a non-muscle alpha-actinin that has long been associated with cancer development. Numerous clinical studies showed that changes in ACTN4 gene expression are correlated with aggressiveness, invasion, and metastasis in certain tumors. Amplification of the 19q chromosomal region where the gene is located has also been reported. Experimental manipulations with ACTN4 expression further confirmed its involvement in cell proliferation, motility, and epithelial-mesenchymal transition (EMT). However, both clinical and experimental data suggest that the effects of ACTN4 up- or down-regulation may vary a lot between different types of tumors. Functional studies demonstrated its engagement in a number of cytoplasmic and nuclear processes, ranging from cytoskeleton reorganization to regulation of different signaling pathways. Such a variety of functions may be the reason behind cell type and cell line specific responses. Herein, we will review research progress and controversies regarding the prognostic and functional significance of ACTN4 for tumorigenesis.

Measurement of copy number of ACTN4 to optimize the therapeutic strategy for locally advanced pancreatic cancer

The standard therapeutic strategy recommended for locally advanced pancreatic cancer (LAPC) is typically chemotherapy or chemoradiotherapy (CRT). Although the clinical benefit of chemotherapy alone versus CRT for LAPC has been compared in a number of clinical trials, the optimal therapy for LAPC remains unclear. Moreover, the clinical benefit derived from treatment in each clinical trial is a matter of controversy, and the superiority of one treatment over another has yet to be definitively demonstrated. The poor outcomes seen among patients with LAPC owe largely to the emergence of metastatic disease; therefore, accurately evaluating occult distant metastasis before choosing a therapeutic strategy could be expected to help stratify patients with LAPC into the most appropriate treatment regimen, namely local control or systemic therapy. In 1998, we identified the actinin-4 gene (ACTN4) as an actin-binding protein and showed its molecular mechanisms had clinical implications for cancer metastasis. We also identified ACTN4 gene amplification in pancreatic, ovarian, and salivary gland cancer, and demonstrated its utility as a strong prognostic biomarker for stage I lung adenocarcinoma in patients who had never received chemotherapy. Moreover, we recently reported that ACTN4 gene amplification could be a useful biomarker for predicting the efficacy of CRT for LAPC. In the present review, we summarize current knowledge regarding therapeutic strategies for LAPC and discuss the potential development of personalized medicine using ACTN4 measurement for patients with LAPC.

DJ-1 is a useful biomarker for invasive extrahepatic cholangiocarcinoma

We have previously reported that DJ-1 protein is up-regulated in cholangiocarcinoma compared with non-neoplastic epithelium of the bile duct in a study using liquid-chromatography mass spectrometry-based proteomics. The aim of this study was to clarify whether DJ-1 expression offers a biomarker for patients with invasive extrahepatic cholangiocarcinoma (EHCC) who undergo surgical resection with curative intent. Positive immunohistochemical (IHC) staining of DJ-1 was significantly more frequent in the cytoplasm of 96 invasive EHCCs (n = 28, 29.2%) than in that of 66 non-neoplastic epithelial lesions adjacent to invasive EHCC (n = 7, 10.6%; P = .006). No significant difference in clinicopathological features was evident between invasive EHCC patients with negative (n = 68) and positive (n = 28) IHC staining. However, negative IHC staining for DJ-1 in cytoplasm was selected as an independent risk factor for adverse prognosis on multivariate analysis (P = .004, hazard ratio 2.13, 95% confidence interval 1.28-3.57). Serum levels of DJ-1 in 16 invasive EHCC patients with metastasis were compared with 12 invasive EHCC patients without metastasis. Serum levels of DJ-1 tended to be higher in 16 patients with metastasis (median, 40.9 ng/ml) than in 12 patients without (27.6 ng/ml, P = .137). In addition, patients with high serum levels (≥ 40 ng/ml) of DJ-1 tended to have metastasis more frequently than those without (P = .054, Fisher's exact test). We concluded that IHC staining pattern and serum level of DJ-1 in patients with invasive EHCC might be predictive of prognosis and metastasis, respectively.

Actinin-4 protein overexpression as a predictive biomarker in adjuvant chemotherapy for resected lung adenocarcinoma

Aim: Although several clinical trials demonstrated the benefits of platinum-combination adjuvant chemotherapy for stage II–IIIA lung adenocarcinoma, predictive biomarkers for the efficacy of such therapy have not yet been identified. We evaluated protein overexpression of actinin-4 as a predictive biomarker of the efficacy of adjuvant chemotherapy in resected lung adenocarcinoma. Materials & methods: We measured actinin-4 protein levels in patients with completely resected stage II–IIIA lung adenocarcinoma using immunohistochemistry and then retrospectively compared survival between adjuvant chemotherapy and observation groups. Results: A total of 148 eligible patients were classified into actinin-4 positive or negative cases by immunohistochemistry. In the former, patients with adjuvant chemotherapy survived significantly longer than those with observation (hazard ratio [HR]: 0.307; p = 0.028). But, no significant survival benefit was noted with adjuvant chemotherapy (HR: 0.926; p = 0.876) in the latter. Conclusion: This marker could predict the efficacy of adjuvant chemotherapy for resected lung adenocarcinoma patients.

Prognostic significance of gene amplification of ACTN4 in stage I and II oral tongue cancer

Despite complete resection of the early stage of oral tongue cancer by partial glossectomy, late cervical lymph node metastasis is frequently observed. Gene amplification of ACTN4 (protein name: actinin-4) is closely associated with the metastatic potential of various cancers. This retrospective study was performed to demonstrate the potential usefulness of ACTN4 gene amplification as a prognostic biomarker in patients with stage I/II oral tongue cancer. Fifty-four patients with stage I/II oral tongue cancer were enrolled retrospectively, in accordance with the reporting recommendations for tumour marker prognostic studies (REMARK) guidelines. The copy number of ACTN4 and the protein expression of actinin-4 were evaluated by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC), respectively. The overall survival time of patients with gene amplification of ACTN4 was significantly shorter than that of patients without gene amplification (P=0.0010, log-rank test). Gene amplification of ACTN4 was a significant independent risk factor for death in patients with stage I/II oral tongue cancer (hazard ratio 6.08, 95% confidence interval 1.66-22.27). Gene amplification of ACTN4 is a potential prognostic biomarker for overall survival in oral tongue cancer.

A Two-Gene Prognostic Classifier for Early-Stage Lung Squamous Cell Carcinoma in Multiple Large-Scale and Geographically Diverse Cohorts

INTRODUCTION

There are no validated molecular methods that prospectively identify patients with surgically resected lung squamous cell carcinoma (SCC) at high risk for recurrence. By focusing on the expression of genes with known functions in development of lung SCC and prognosis, we sought to develop a robust prognostic classifier of early-stage lung SCC.

METHODS

The expression of 253 genes selected by literature search was evaluated in microarrays from 107 stage I/II tumors. Associations with survival were evaluated by Cox regression and Kaplan-Meier survival analyses in two independent cohorts of 121 and 91 patients with SCC, respectively. A classifier score based on multivariable Cox regression was derived and examined in six additional publicly available data sets of stage I/II lung SCC expression profiles (n = 358). The prognostic value of this classifier was evaluated in meta-analysis of patients with stage I/II (n = 479) and stage I (n = 326) lung SCC.

RESULTS

Dual specificity phosphatase 6 gene (DUSP6) and actinin alpha 4 gene (ACTN4) were associated with prognostic outcome in two independent patient cohorts. Their expression values were utilized to develop a classifier that identified patients with stage I/II lung SCC at high risk for recurrence (hazard ratio [HR] = 4.7, p = 0.018) or cancer-specific mortality (HR = 3.5, p = 0.016). This classifier also identified patients at high risk for recurrence (HR = 2.7, p = 0.008) or death (HR = 2.2, p = 0.001) in publicly available data sets of stage I/II and in meta-analysis of stage I patients.

CONCLUSIONS

We have established and validated a prognostic classifier to inform clinical management of patients with lung SCC after surgical resection.

Translational Research and Plasma Proteomic in Cancer

Proteomics is a recent field of research in molecular biology that can help in the fight against cancer through the search for biomarkers that can detect this disease in the early stages of its development. Proteomic is a speedily growing technology, also thanks to the development of even more sensitive and fast mass spectrometry analysis. Although this technique is the most widespread for the discovery of new cancer biomarkers, it still suffers of a poor sensitivity and insufficient reproducibility, essentially due to the tumor heterogeneity. Common technical shortcomings include limitations in the sensitivity of detecting low abundant biomarkers and possible systematic biases in the observed data. Current research attempts are trying to develop high-resolution proteomic instrumentation for high-throughput monitoring of protein changes that occur in cancer. In this review, we describe the basic features of the proteomic tools which have proven to be useful in cancer research, showing their advantages and disadvantages. The application of these proteomic tools could provide early biomarkers detection in various cancer types and could improve the understanding the mechanisms of tumor growth and dissemination.

NHERF1 regulates actin cytoskeleton organization through modulation of α-actinin-4 stability

The actin cytoskeleton is composed of a highly dynamic network of filamentous proteins, yet the molecular mechanism that regulates its organization and remodeling remains elusive. In this study, Na(+)/H(+) exchanger regulatory factor (NHERF)-1 loss-of-function and gain-of-function experiments reveal that polymerized actin cytoskeleton (F-actin) in HeLa cells is disorganized by NHERF1, whereas actin protein expression levels exhibit no detectable change. To elucidate the molecular mechanism underlying actin cytoskeleton disorganization by NHERF1, a combined 2-dimensional electrophoresis-matrix-assisted laser desorption/ionization-time of flight mass spectrometry approach was used to screen for proteins regulated by NHERF1 in HeLa cells. α-Actinin-4, an actin cross-linking protein, was identified. Glutathione S-transferase pull-down and coimmunoprecipitation studies showed the α-actinin-4 carboxyl-terminal region specifically interacted with the NHERF1 postsynaptic density 95/disc-large/zona occludens-1 domain. The NHERF1/α-actinin-4 interaction increased α-actinin-4 ubiquitination and decreased its expression levels, resulting in actin cytoskeleton disassembly. Our study identified α-actinin-4 as a novel NHERF1 interaction partner and provided new insights into the regulatory mechanism of the actin cytoskeleton by NHERF1.

The biological role of actinin-4 (ACTN4) in malignant phenotypes of cancer

Invasion and metastasis are malignant phenotypes in cancer that lead to patient death. Cell motility is involved in these processes. In 1998, we identified overexpression of the actin-bundling protein actinin-4 in several types of cancer. Protein expression of actinin-4 is closely associated with the invasive phenotypes of cancers. Actinin-4 is predominantly expressed in the cellular protrusions that stimulate the invasive phenotype in cancer cells and is essential for formation of cellular protrusions such as filopodia and lamellipodia. ACTN4 (gene name encoding actinin-4 protein) is located on human chromosome 19q. ACTN4 amplification is frequently observed in patients with carcinomas of the pancreas, ovary, lung, and salivary gland, and patients with ACTN4 amplifications have worse outcomes than patients without amplification. In addition, nuclear distribution of actinin-4 is frequently observed in small cell lung, breast, and ovarian cancer. Actinin-4, when expressed in cancer cell nuclei, functions as a transcriptional co-activator. In this review, we summarize recent developments regarding the biological roles of actinin-4 in cancer invasion.