HAX-1 inhibits apoptosis in prostate cancer through the suppression of caspase-9 activation

Molecular functions of HAX1 during disease progress

HCLS1-associated protein X-1 (HAX1) is a newly discovered multifunctional cell regulatory protein that is widely expressed in cells and has a close relationship with multiple cellular proteins. HAX1 plays important roles in various processes, including the regulation of apoptosis, maintenance of mitochondrial membrane potential stability and calcium homeostasis, occurrence and development of diseases, post-transcriptional regulation of gene expression, and host immune response after viral infection. In this article, we have reviewed the research progress on the biological functions of HAX1, thereby laying a theoretical foundation for further exploration of its underlying mechanisms and targeted application.

Non-coding RNA transcripts, incredible modulators of cisplatin chemo-resistance in bladder cancer through operating a broad spectrum of cellular processes and signaling mechanism

Bladder cancer (BC) is a highly frequent neoplasm in correlation with significant rate of morbidity, mortality, and cost. The onset of BC is predominantly triggered by environmental and/or occupational exposures to carcinogens, such as tobacco. There are two distinct pathways by which BC can be developed, including non-muscle-invasive papillary tumors (NMIBC) and non-papillary (or solid) muscle-invasive tumors (MIBC). The Cancer Genome Atlas project has further recognized key genetic drivers of MIBC along with its subtypes with particular properties and therapeutic responses; nonetheless, NMIBC is the predominant BC presentation among the suffering individuals. Radical cystoprostatectomy, radiotherapy, and chemotherapy have been verified to be the common therapeutic interventions in metastatic tumors, among which chemotherapeutics are more conventionally utilized. Although multiple chemo drugs have been broadly administered for BC treatment, cisplatin is reportedly the most effective chemo drug against the corresponding malignancy. Notwithstanding, tumor recurrence is usually occurred following the consumption of cisplatin regimens, particularly due to the progression of chemo-resistant trait. In this framework, non-coding RNAs (ncRNAs), as abundant RNA transcripts arise from the human genome, are introduced to serve as crucial contributors to tumor expansion and cisplatin chemo-resistance in bladder neoplasm. In the current review, we first investigated the best-known ncRNAs, i.e. microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs), correlated with cisplatin chemo-resistance in BC cells and tissues. We noticed that these ncRNAs could mediate the BC-related cisplatin-resistant phenotype through diverse cellular processes and signaling mechanisms, reviewed here. Eventually, diagnostic and prognostic potential of ncRNAs, as well as their therapeutic capabilities were highlighted in regard to BC management.

HAX1 is a novel binding partner of Che-1/AATF. Implications in oxidative stress cell response

HAX1 is a multifunctional protein involved in the antagonism of apoptosis in cellular response to oxidative stress. In the present study we identified HAX1 as a novel binding partner for Che-1/AATF, a pro-survival factor which plays a crucial role in fundamental processes, including response to multiple stresses and apoptosis. HAX1 and Che-1 proteins show extensive colocalization in mitochondria and we demonstrated that their association is strengthened after oxidative stress stimuli. Interestingly, in MCF-7 cells, resembling luminal estrogen receptor (ER) positive breast cancer, we found that Che-1 depletion correlates with decreased HAX1 mRNA and protein levels, and this event is not significantly affected by oxidative stress induction. Furthermore, we observed an enhancement of the previously reported interaction between HAX1 and estrogen receptor alpha (ERα) upon H2O2 treatment. These results indicate the two anti-apoptotic proteins HAX1 and Che-1 as coordinated players in cellular response to oxidative stress with a potential role in estrogen sensitive breast cancer cells.

CircGFPT1 regulates the growth and apoptosis of esophageal squamous cell carcinoma through miR-142-5p/HAX1 axis

BACKGROUND

Currently, multiple circular RNAs (circRNAs) have been verified to act as essential regulators in the progression of esophageal squamous cell carcinoma (ESCC). However, there is no study regarding the role of circGFPT1 in the progression of cancers including ESCC. We aimed to investigate the role of circGFPT1 in ESCC progression.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to measure the expression of circGFPT1, miR-142-5p and HS1-associated protein X-1 (HAX1). 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and 5-ethynyl-2'-deoxyuridine (EdU) assays were employed to evaluate cell proliferation. Cell migration and invasion were detected by wound-healing and transwell assays. Flow cytometry analysis was conducted to assess cell apoptosis. The protein expression of E-cadherin, N-cadherin, Vimentin, C-caspase3, HAX1 and nuclear proliferation marker (Ki67) was analyzed by western blot or immunohistochemistry assay.

RESULTS

CircGFPT1 was up-regulated in ESCC tissues and cells. Silencing of circGFPT1 repressed cell proliferation and induced cell apoptosis in ESCC cells. CircGFPT1 acted as a sponge of miR-142-5p. The effects of circGFPT1 knockdown on ESCC cell proliferation and apoptosis were reversed by miR-142-5p inhibition. HAX1 was confirmed to be a target gene of miR-142-5p. CircGFPT1 knockdown inhibited HAX1 expression by targeting miR-142-5p. Additionally, circGFPT1 knockdown hampered tumorigenesis in vivo.

CONCLUSION

CircGFPT1 promoted ESCC cell growth and repressed apoptosis by up-regulating HAX1 through sponging miR-142-5p.

Long Noncoding RNA Cytoskeleton Regulator RNA Suppresses Apoptosis in Hepatoma Cells by Modulating the miR-125a-5p/HS1-Associated Protein X-1 Axis to Induce Caspase-9 Inactivation

Background/Aims

The involvement of long noncoding RNAs in the carcinogenesis of hepatocellular carcinoma (HCC) has been well documented by substantial evidence. However, whether cytoskeleton regulator RNA (CYTOR) could affect the progression of HCC remains unclear.

Methods

The relative expression of CYTOR, miR-125a-5p and HS1-associated protein X-1 (HAX-1) mRNA in HCC cells were determined via quantitative real-time polymerase chain reaction. The viability of treated HCC cells was measured by Cell Counting Kit-8 assay. Cell apoptosis was estimated by flow cytometry analysis, assessment of caspase-9 activity and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining, and Western blot of apoptosis-related proteins. The interplay between CYTOR or HAX-1 and miR-125a-5p was validated by dual-luciferase reporter assay.

Results

CYTOR was upregulated and miR-125a-5p was downregulated in HCC cells. CYTOR silencing inhibited cell proliferation and promoted cell apoptosis in HepG2 and SMMC-7721 cells. miR-125a-5p was sponged and negatively regulated by CYTOR, and HAX-1 was directly targeted and negatively modulated by miR-125a-5p. Overexpression of miR-125a-5p enhanced the repressive effects of CYTOR knockdown on HCC cells, and knockdown of HAX-1 enhanced the inhibitory effects of miR-125a-5p mimics on HCC cells.

Conclusions

CYTOR silencing facilitates HCC cell apoptosis in vitro via the miR-125a-5p/HAX-1 axis.

HAX1: A versatile, intrinsically disordered regulatory protein

HAX1 is a relatively small, ubiquitously expressed, predominantly mitochondrial, intrinsically disordered protein. It has been implicated in the regulation of apoptosis, cell migration, calcium cycling, proteostasis, angiogenesis, autophagy and translation. A wide spectrum of functions, numerous interactions and still elusive molecular mechanisms of action make HAX1 an intriguing subject of research. Moreover, HAX1 is involved in the pathogenesis of diseases; its deficiency leads to neutropenia and its overexpression is associated with cancer. In this review we aim to describe the characteristics of HAX1 gene and protein, and comprehensively discuss its multiple functions, highlighting the emerging role of HAX1 in protection from stress and apoptosis through maintaining cellular proteostasis and homeostasis.

MicroRNAs as the pivotal regulators of cisplatin resistance in head and neck cancers

Although, there is a high rate of good prognosis in early stage head and neck tumors, about half of these tumors are detected in advanced stages with poor prognosis. A combination of chemotherapy, radiotherapy, and surgery is the treatment option in head and neck cancer (HNC) patients. Although, cisplatin (CDDP) as the first-line drug has a significant role in the treatment of HNC patients, CDDP resistance can be observed in a large number of these patients. Therefore, identification of the molecular mechanisms involved in CDDP resistance can help to reduce the side effects and also provides a better therapeutic management. MicroRNAs (miRNAs) as the post-transcriptional regulators play an important role in drug resistance. Therefore, in the present review we investigated the role of miRNAs in CDDP response of head and neck tumors. It has been reported that the miRNAs exerted their roles in CDDP response by regulation of signaling pathways such as WNT, NOTCH, PI3K/AKT, TGF-β, and NF-kB as well as apoptosis, autophagy, and EMT process. The present review paves the way to suggest a non-invasive miRNA based panel marker for the prediction of CDDP response among HNC patients. Therefore, such diagnostic miRNA based panel marker reduces the CDDP side effects and improves the clinical outcomes of these patients following an efficient therapeutic management.

Targeting hypoxia-induced tumor stemness by activating pathogen-induced stem cell niche defense

Tumor hypoxia and oxidative stress reprograms cancer stem cells (CSCs) to a highly aggressive and inflammatory phenotypic state of tumor stemness. Previously, we characterized tumor stemness phenotype in the ATP Binding Cassette Subfamily G Member 2 (ABCG2)–positive migratory side population (SPm) fraction of CSCs exposed to extreme hypoxia followed by reoxygenation. Here, we report that post-hypoxia/reoxygenation SPm+/ABCG2+ CSCs exerts defense against pathogen invasion that involves bystander apoptosis of non-infected CSCs. In an in vitro assay of cancer cell infection by Bacillus Calmette Guerin (BCG) or mutant Mycobacterium tuberculosis (Mtb) strain 18b (Mtb-m18b), the pathogens preferentially replicated intracellular to SPm+/ABCG2+ CSCs of seven cell lines of diverse cancer types including SCC-25 oral squamous cancer cell line. The conditioned media (CM) of infected CSCs exhibited direct anti-microbial activity against Mtb and BCG, suggesting niche defense against pathogen. Importantly, the CM of infected CSCs exhibited marked in vitro bystander apoptosis toward non-infected CSCs. Moreover, the CM-treated xenograft bearing mice showed 10- to 15-fold reduction (p < 0.001; n = 7) in the number of CSCs residing in the hypoxic niches. Our in vitro studies indicated that BCG-infected SPm+/ABCG2+ equivalent EPCAM+/ABCG2+ CSCs of SCC-25 cells underwent pyroptosis and released a high mobility group box protein 1 (HMGB1)/p53 death signal into the tumor microenvironment (TME). The death signal can induce a Toll-like receptor 2/4–mediated bystander apoptosis in non-infected CSCs by activating p53/MDM2 oscillation and subsequent activation of capase-3–dependent intrinsic apoptosis. Notably, SPm+/ABCG2+ but not SP cells undergoing bystander apoptosis amplified the death signal by further release of HMGB1/p53 complex into the TME. These results suggest that post-hypoxia SPm+/ABCG2+ CSCs serve a functional role as a tumor stemness defense (TSD) phenotype to protect TME against bacterial invasion. Importantly, the CM of TSD phenotype undergoing bystander apoptosis may have therapeutic uses against CSCs residing in the hypoxic niche.

Hax-1 Regulates Radiation-Induced Mitochondrial-Dependent Apoptosis of Uveal Melanoma Cells through PI3K/AKT/eNOS Pathway

Uveal melanoma is an aggressive skin cancer that remains insurmountable and is accompanied by inferior prognostic results. The proliferative and survival mechanisms of uveal melanoma cells need to be further investigated to improve the treatment of uveal melanoma. According to reports, HAX-1 is an antiapoptotic protein vital for multiple malignancies. Nevertheless, the role and causal link of HAX-1 in uveal melanoma are still elusive. The survival diversity of uveal melanoma sufferers with diverse haX-1 expressing levels was studied by TCGA database. Patients in the risk_high group exhibited greater levels of HAX-1 in contrast to the risk_low group, and individuals with higher HAX-1 levels displayed inferior survival times. The outcomes of CCK-8 and clonogenesis revealed that the proliferative rate of haX-1 knockout cells was slower. The result of scratch experiment shows that the ability of scratch recovery after HAX-1 is reduced. Transwell migration and tumor cell pelletization experiments showed that siHAX-1 significantly reduced cell migration and tumor cell pelletization. After haX-1 was knocked out, the loss of MMP was decreased, the transfer of CyT C was elevated, and the protein expression of Bax, Caspase 3, and Bcl2 was elevated, suggesting that mitochondria-induced apoptosis was increased. Sihax-1 treatment remarkably decreased the phosphonation of phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR)/endothelial NO synthase (eNOS) in mum-2B and C918. Pretreatment with LY294002 significantly restored iHAX-1-induced decline in PI3K/AKT/mTOR/eNOS phosphorylation. Therefore, our results suggest that haX-1 induces radiation-dependent apoptosis of UM cells via the PI3K/AKT/eNOS signal path.

Anti-apoptotic HAX-1 suppresses cell apoptosis by promoting c-Abl kinase-involved ROS clearance

The anti-apoptotic protein HAX-1 has been proposed to modulate mitochondrial membrane potential, calcium signaling and actin remodeling. HAX-1 mutation or deficiency results in severe congenital neutropenia (SCN), loss of lymphocytes and neurological impairments by largely unknown mechanisms. Here, we demonstrate that the activation of c-Abl kinase in response to oxidative or genotoxic stress is dependent on HAX-1 association. Cellular reactive oxygen species (ROS) accumulation is inhibited by HAX-1-dependent c-Abl activation, which greatly contributes to the antiapoptotic role of HAX-1 in stress. HAX-1 (Q190X), a loss-of-function mutant responsible for SCN, fails to bind with and activate c-Abl, leading to dysregulated cellular ROS levels, damaged mitochondrial membrane potential and eventually apoptosis. The extensive apoptosis of lymphocytes and neurons in Hax-1-deficient mice could also be remarkably suppressed by c-Abl activation. These findings underline the important roles of ROS clearance in HAX-1-mediated anti-apoptosis by c-Abl kinase activation, providing new insight into the pathology and treatment of HAX-1-related hereditary disease or tumorigenesis.

Immunohistochemical Evaluation of PARP and Caspase-3 as Prognostic Markers in Prostate Carcinomas

Prostate cancer is the second most common neoplasm among men, with a high mortality rate in advanced stages. Poly (ADP-ribose) polymerase (PARP) plays an important role in repair to DNA damage, being associated with resistance to tumor cell death. Conversely, Caspase-3 is a crucial mediator of programmed cell death, being highly expressed in apoptotic cells. The aim of the present study was to characterize the expression of PARP and Caspase-3 by immunohistochemistry in patients with advanced prostate cancer. PARP and Caspase-3 were independently correlated to patients' evolution, in accordance with the classification of prognostic groups. The increase in PARP expression was positively correlated with tumor patients with poor prognosis (P < 0.0001). In contrast, a decrease in Caspase-3 expression was identified in patients with poor prognosis, when compared with prostate cancer patients with good prognosis (P = 0.0007). Numerically, 92.3% of patients previously classified with poor prognosis showed higher PARP expression, while 93.75% of patients previously classified with good prognosis showed higher levels of Caspase-3. We conclude that PARP and Caspase-3 are potential prognostic markers for prostate cancer patients with different prognosis.

HAX1 maintains the glioma progression in hypoxia through promoting mitochondrial fission

HCLS1‐associated protein X‐1 (HAX1), an anti‐apoptotic molecular, overexpresses in glioma. However, the role of HAX1 in glioma cell surviving in hypoxic environment remains unclear. Western blotting, qRT‐PCR, Transwell assay, TUNEL assay, wounding healing assay, clone formation, tumour xenograft model and immunohistochemical staining were used to investigate the role of HAX1 in glioma. HAX1 regulated by HIF‐1α was increased in glioma cells cultured in hypoxia. Silencing of HAX1 could cause an increased apoptosis of glioma cells cultured in hypoxia. Silencing of HAX1 also decreased the proliferation, migration and invasion of glioma cells cultured in hypoxia. Increased mitochondrial fission could prevent glioma cells from the damage induced by HAX1 knockdown in hypoxia. Furthermore, HAX1 was found to regulate glioma cells through phosphorylated AKT/Drp signal pathway. In conclusion, our study suggested that HAX1 promoted survival of glioma cells in hypoxic environment via AKT/Drp signal pathway. Our study also provided a potential therapeutic target for glioma.

Caspase-9: A Multimodal Therapeutic Target With Diverse Cellular Expression in Human Disease

Caspase-9, a cysteine-aspartic protease known for its role as an initiator of intrinsic apoptosis, regulates physiological cell death and pathological tissue degeneration. Its nonapoptotic functions, including regulation of cellular differentiation/maturation, innate immunity, mitochondrial homeostasis, and autophagy, reveal a multimodal landscape of caspase-9 functions in health and disease. Recent work has demonstrated that caspase-9 can drive neurovascular injury through nonapoptotic endothelial cell dysfunction. CASP9 polymorphisms have been linked with various cancers, neurological disorders, autoimmune pathologies and lumbar disc disease. Clinical reports suggest alterations in caspase-9 expression, activity or function may be associated with acute and chronic neurodegeneration, retinal neuropathy, slow-channel myasthenic syndrome, lumbar disc disease, cardiomyopathies, atherosclerosis and autoimmune disease. Healthy tissues maintain caspase-9 activity at low basal levels, rendering supraphysiological caspase-9 activation a tractable target for therapeutic interventions. Strategies for selective inhibition of caspase-9 include dominant negative caspase-9 mutants and pharmacological inhibitors derived from the XIAP protein, whose Bir3 domain is an endogenous highly selective caspase-9 inhibitor. However, the mechanistic implications of caspase-9 expression and activation remain indeterminate in many pathologies. By assembling clinical reports of caspase-9 genetics, signaling and cellular localization in human tissues, this review identifies gaps between experimental and clinical studies on caspase-9, and presents opportunities for further investigations to examine the consequences of caspase activity in human disease.

Magnolin Inhibits Proliferation and Invasion of Breast Cancer MDA-MB-231 Cells by Targeting the ERK1/2 Signaling Pathway

The aim of this study was to evaluate the effects of Magnolin (MGL) on inhibition of human breast cancer cells, and explore the underlying molecular mechanisms. The viability of the treated cells was assessed with the Cell Counting Kit-8 (CCK-8) assay, and the proliferation was analyzed in terms of EdU uptake, colony formation, and flow cytometry. The in vitro invasion and migration were determined by the transwell and wound healing assays respectively. The mRNA and protein levels of relevant factors was evaluated by quantitative real-time PCR and Western blotting respectively. MGL significantly decreased the viability and promoted apoptosis of MDA-MB-231 cells, along with reducing EdU incorporation rate as well as the colony forming capacity compared to the untreated control cells. In addition, the in vitro invasion and migration were also significantly inhibited by MGL. Furthermore, MGL suppressed the phosphorylation of MEK1/2, extracellular signal-regulated kinase (ERK)1/2 and significantly downregulated the expression of cyclin-dependent kinase 1 (CDK1), the anti-apoptotic B-cell lymphoma 2 (BCL2) and metastasis-associated matrix metalloproteases (MMPs) 2 & 9, and upregulated the cleaved caspases 3 and 9. After ERK was completely inhibited with the small interfering RNA (siRNA), MGL had no effect on these factors, indicating that ERK is essential for MGL action in breast cancer. In conclusion, MGL inhibits proliferation and invasion of and induces apoptosis in breast cancer cells through the ERK pathway.

HTLV-1 viral oncoprotein HBZ contributes to the enhancement of HAX-1 stability by impairing the ubiquitination pathway

Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus that causes adult T-cell leukemia (ATL). The viral protein HTLV-1 basic leucine-zipper factor (HBZ), which is constitutively expressed in all ATL patient cells, contributes toward the development of ATL; however, the underlying mechanism has not been elucidated yet. Here, we identified HS-1-associated protein X-1 (HAX-1) as a novel binding partner of HBZ. Interestingly, HAX-1 specifically associated with HBZ-US, but not HBZ-SI, in the cytoplasm. HBZ suppressed the polyubiquitination levels of HAX-1 protein by inhibiting the association HAX-1 with F-box protein 25 (FBXO25), which is a member of the SCF E3 ubiquitin ligase complex, and promoted the stabilization of HAX-1 levels. In fact, the protein levels of HAX-1 were significantly increased in HTLV-1 infected and the overexpressing HBZ in uninfected T-cell lines. Enhanced HAX-1 correlated well to suppression of caspase 9 processing, suggesting that HBZ may contribute to the enhancement of antiapoptotic function for HAX-1. Our results revealed a role for HBZ on HAX-1 stabilization by abrogating the ubiquitination-mediated degradation pathway, which may play an important role in understanding the potential mechanisms of HTLV-1 related pathogenesis.

Weighted gene coexpression network analysis identifies hub genes related to KRAS mutant lung adenocarcinoma

The aim of current study was to use Weighted Gene Coexpression Network Analysis (WGCNA) to identify hub genes related to the incidence and prognosis of KRAS mutant (MT) lung adenocarcinoma (LUAD).We involved 184 stage IIB to IV LUAD samples and 59 normal lung tissue samples from The Cancer Genome Atlas (TCGA) database. The R package "limma" was used to identify differentially expressed genes (DEGs). WGCNA and survival analyses were performed by R packages "WGCNA" and "survival," respectively. The functional analyses were performed by R package "clusterProfiler" and GSEA software. Network construction and MCODE analysis were performed by Cytoscape_v3.6.1.Totally 2590 KRAS MT specific DEGs were found between LUAD and normal lung tissues, and 10 WGCNA modules were identified. Functional analysis of the key module showed the ribosome biogenesis related terms were enriched. We observed the expression of 8 genes were positively correlated to the worse survival of KRAS MT LUAD patients, the 7 of them were validated by Kaplan-Meier plotter database (kmplot.com/) (thymosin Beta 10 [TMSB10], ribosomal Protein S16 [RPS16], mitochondrial ribosomal protein L27 [MRPL27], cytochrome c oxidase subunit 6A1 [COX6A1], HCLS1-associated protein X-1 [HAX1], ribosomal protein L38 [RPL38], and ATP Synthase Membrane Subunit DAPIT [ATP5MD]). The GSEA analysis found mTOR and STK33 pathways were upregulated in KRAS MT LUAD (P < .05, false discovery rate [FDR] < 0.25).In summary, our study firstly used WGCNA to identify hub genes in the development of KRAS MT LUAD. The identified prognostic factors would be potential biomarkers in clinical use. Further molecular studies are required to confirm the mechanism of those genes in KRAS MT LUAD.

Novel Role of HAX-1 in Neurons Protection After Spinal Cord Injury Involvement of IRE-1

Spinal cord injury (SCI) is one of the diseases with high probability of causing disability in human beings, and there is no reliable treatment at present. Neuronal apoptosis is a vital component of secondary injury and plays a critical role in the development of neurological dysfunction after spinal cord injury. In this study, we found that the expression and distribution of HAX-1 in neurons increased 1 day after SCI. PC12 cells overexpressing HAX-1 showed decreased apoptosis and PC12 cells are more likely to undergo apoptosis after down-regulating HAX-1, which was confirmed via TUNEL experiments. We found GRP94 showed the same trend as HAX-1 in expression and interacted with HAX-1 and IRE-1 in both spinal cord tissue and PC12 cells, and this interaction seems to be enhanced after SCI. When the expression of HAX-1 was up-regulated, GRP94 also increased, but IRE-1 did not change at all. Further studies showed that overexpression of HAX-1 decreased the expression of pIRE-1, rather than IRE-1, and downstream proteins of the IRE signaling pathway (Caspase12, pJNK and CHOP) were significantly reduced, and vice versa. In animals treated with HAX-1 expressing adenovirus there are more neuronal cells remaining in the damaged spinal cord tissue, and hindlimb motor function of rats was significantly improved. So, we speculate that HAX-1 might play a role in protecting neurons from apoptosis after SCI by regulating the IRE-1 signaling pathway via promoting the dissociation of GRP94 from IRE-1. This may provide a theoretical basis and a potential therapeutic target for clinical improvement of neural function recovery after SCI.

HAX1 impact on collective cell migration, cell adhesion, and cell shape is linked to the regulation of actomyosin contractility

HAX1 protein is involved in the regulation of apoptosis, cell motility and calcium homeostasis. Its overexpression was reported in several tumors, including breast cancer. This study demonstrates that HAX1 has an impact on collective, but not single-cell migration, thus indicating the importance of cell–cell contacts for the HAX1-mediated effect. Accordingly, it was shown that HAX1 knockdown affects cell–cell junctions, substrate adhesion, and epithelial cell layer integrity. As demonstrated here, these effects can be attributed to the modulation of actomyosin contractility through changes in RhoA and septin signaling. Additionally, it was shown that HAX1 does not influence invasive potential in the breast cancer cell line, suggesting that its role in breast cancer progression may be linked instead to collective invasion of the epithelial cells but not single-cell dissemination.

Hematopoietic-substrate-1 associated protein X-1 (HAX-1) regulates liver cancer cells growth, metastasis, and angiogenesis through Akt

The aim of this study was to investigate the effects and mechanisms of hematopoietic-substrate-1-associated protein X-1 (HAX-1) on liver cancer cells. Information on HAX-1 from liver cancer patients was analyzed by the Cancer Genome Atlas (TCGA) program. Cell migration and invasion abilities were respectively tested by scratch assay and transwell assay. Tube formation assay was applied to detect angiogenesis protein and mRNA was determined using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. We found that the median month survival of HAX-1 overexpressing liver cancer patients was shorter than that of HAX-1 normal liver cancer patients. HAX-1 was overexpressed in liver cancer tissues and cells, and HAX-1 overexpression promoted the liver cancer cells growth, migration, and invasion, whereas silencing HAX-1 produced the opposite results. Inhibition of Akt by LY294002 reversed the migration and invasion abilities of liver cancer cells, and inhibited the ability of cells growth and angiogenesis. Silencing PIK3CA enhanced the inhibitory effects of HAX-1 silencing on the viability, migration, and invasion of liver cancer cells. HAX-1 affected liver cancer cells metastasis and angiogenesis by affecting Akt phosphorylation and FOXO3A expression.

Targeting Mitochondrial Structure Sensitizes Acute Myeloid Leukemia to Venetoclax Treatment

The BCL2 family plays important roles in acute myeloid leukemia (AML). Venetoclax, a selective BCL2 inhibitor, has received FDA approval for the treatment of AML. However, drug resistance ensues after prolonged treatment, highlighting the need for a greater understanding of the underlying mechanisms. Using a genome-wide CRISPR/Cas9 screen in human AML, we identified genes whose inactivation sensitizes AML blasts to venetoclax. Genes involved in mitochondrial organization and function were significantly depleted throughout our screen, including the mitochondrial chaperonin CLPB. We demonstrated that CLPB is upregulated in human AML, it is further induced upon acquisition of venetoclax resistance, and its ablation sensitizes AML to venetoclax. Mechanistically, CLPB maintains the mitochondrial cristae structure via its interaction with the cristae-shaping protein OPA1, whereas its loss promotes apoptosis by inducing cristae remodeling and mitochondrial stress responses. Overall, our data suggest that targeting mitochondrial architecture may provide a promising approach to circumvent venetoclax resistance. SIGNIFICANCE: A genome-wide CRISPR/Cas9 screen reveals genes involved in mitochondrial biological processes participate in the acquisition of venetoclax resistance. Loss of the mitochondrial protein CLPB leads to structural and functional defects of mitochondria, hence sensitizing AML cells to apoptosis. Targeting CLPB synergizes with venetoclax and the venetoclax/azacitidine combination in AML in a p53-independent manner.See related commentary by Savona and Rathmell, p. 831.This article is highlighted in the In This Issue feature, p. 813.

Inhibition of HAX-1 by miR-125a reverses cisplatin resistance in laryngeal cancer stem cells

Chemoresistance is a major obstacle in chemotherapy of laryngeal carcinoma. Recently, studies indicate that cancer stem cells are responsible for chemotherapy failure. In addition, microRNAs play important roles in tumor initiation, development and multidrug resistance. In the present study, we found that the expression of microRNA-125a was decreased in laryngeal carcinoma tissues and Hep-2 laryngeal cancer stem cells (Hep-2-CSCs). MicroRNA-125a gain-of-function significantly increased the sensitivity of Hep-2-CSCs to cisplatin in vitro and in vivo. Combination with microRNA-125a mimics can decrease the half maximal inhibitory concentration of Hep-2-CSCs to cisplatin. Mechanically, we found that microRNA-125a reverses cisplatin resistance in Hep-2-CSCs by targeting Hematopoietic cell-specific protein 1-associated protein X-1 (HAX-1). Inhibition of HAX-1 by microRNA-125a significantly promotes the cisplatin-induced apoptosis in Hep-2-CSCs through mitochondrial pathway. In addition, multidrug resistance of Hep-2-CSCs to vincristine, etoposide and doxorubicin was greatly improved after the cells were transfected with microRNA-125a mimics. These dates strongly suggested the promotion of microRNA-125a/HAX-1 axis on chemotherapy of laryngeal carcinoma.

Identification of the Functional Autophagy-Regulatory Domain in HCLS1-Associated Protein X-1 That Resists Against Oxidative Stress

HCLS1 Associated Protein X-1 (HAX1) promotes cell survival through attenuation of the damaged signals from endoplasmic reticulum and mitochondria, which are known as prominent intracellular compartments for the autophagic process under stress conditions. This study investigates whether autophagy can be upregulated in response to HAX1 overexpression and identifies the functional motif in HAX1 responsible for the autophagic induction. Autophagosome accumulation, mitochondrial membrane potential (Δψm), and apoptosis were assessed in HEK293 cells post transduction with full-length or truncated HAX1-encoding genes, while empty vector-transduced cells served as control. Upon the oxidative stress, the enhanced autophagy induction was observed in cells overexpressing HAX1, as well as HAX1 truncations that encode peptide segments ranging from amino acids 127-180 (AA127-180). This protective response was further supported by flow cytometry and Western Blot results, in which oxidative stress-induced Δψm dissipation and the programmed cell death were suppressed in HAX1-overexpressing cells, associated with reduced DNA fragmentation and decreased Caspase-9 cleavage. Interestingly, the HAX1-induced autophagy response was abrogated when AA127-180 was removed, compromising the antiapoptotic effects upon oxidative stress. Overall, these data indicate that autophagy induction is involved in HAX1-induced cell protective mechanism, and AA127-180 serves as the functional autophagy-regulatory domain of this antiapoptotic protein.

HAX-1 Protects Glioblastoma Cells from Apoptosis through the Akt1 Pathway

Glioblastoma is the most common malignant tumor in central nervous system (CNS), and it is still insurmountable and has a poor prognosis. The proliferation and survival mechanism of glioma cells needs to be explored further for the development of glioma treatment. Hematopoietic-substrate-1 associated protein X-1 (HAX-1) has been reported as an anti-apoptosis protein that plays an important role in several malignant tumors. However, the effect and mechanism of HAX-1 in glioblastomas remains unknown. This study aimed to investigate the effect of HAX-1 in glioblastoma cells and explore the mechanism. The results of clone formation and Edu proliferation assay showed slower multiplication in HAX-1 knock-out cells. Flow cytometry showed cell cycle arrest mainly in G0/G1 phase. Apoptosis due to oxidative stress was increased after HAX-1 was knocked out. Western-blot assay exhibited that the levels of p21, Bax, and p53 proteins were significantly raised, and that the activation of the caspase cascade was enhanced in the absence of HAX-1. The degradation rate and ubiquitination of p53 declined because of the decrease in phosphorylation of proteins MDM2 and Akt1. Co-immunoprecipitation (Co-IP) and immunefluorescent co-localization assays were performed to test the influence of HAX-1 on the interaction between Akt1 and Hsp90, which is crucial for the activity of Akt1. In conclusion, this novel study suggested that HAX-1 could affect the Akt1 pathway through Hsp90. The knock-out of HAX-1 leads to the inactivity of the Ak1t/MDM2 axis, which leads to increased levels of p53, and finally generates cell cycle arrest and results in the apoptosis of glioblastoma cells.

Caspase-9: structure, mechanisms and clinical application

As the most intensively studied initiator caspase, caspase-9 is a key player in the intrinsic or mitochondrial pathway which is involved in various stimuli, including chemotherapies, stress agents and radiation. Caspase-9 is activated on the apoptosome complex to remain catalytic status and is thought of involving homo-dimerization monomeric zymogens. Failing to activate caspase-9 has profound physiological and pathophysiological outcomes, leading to degenerative and developmental disorders even cancer. To govern the apoptotic commitment process appropriately, plenty of proteins and small molecules involved in regulating caspase-9. Therefore, this review is to summarize recent pertinent literature on the comprehensive description of the molecular events implicated in caspase-9 activation and inhibition, as well as the clinical trials in progress to give deep insight into caspase-9 for suppressing cancer. We hope that our concerns will be helpful for further clinical studies addressing the roles of caspase-9 and its regulators demanded to identify more effective solutions to overcome intrinsic apoptosis-related diseases especially cancer.

Analysis of the expression of HAX-1 gene in human glioma

Glioma, as the most common aggressive malignant tumor in the central nervous system, is still an insurmountable issue in neural diseases. The proliferation and survival mechanism of glioma cells need to be explored further for the development of glioma treatment. Hematopoietic cell-specific protein 1 associated protein X-1 (HAX-1) is well known for its anti-apoptotic effect. It was reported to play an important role in several malignant tumors. However, the effect of HAX-1 in glioma still remains unknown. This study aimed to investigate the expression of HAX-1 in glioma and the correlation between HAX-1 and the clinicopathological characteristics and prognosis of glioma. Quantitative reverse transcription polymerase chain reaction and Western blot analysis showed that HAX-1 was overexpressed in glioma cell lines compared with normal human astrocytes. This trend was confirmed by comparing the expression of HAX-1 in glioma tissues and nontumorous tissues. The study also analyzed the correlation between the expression of HAX-1 and clinicopathological characteristics of glioma and found the expression of HAX-1 to be highly related to the differentiation and World Health Organization stage of glioma tissues. The survival analysis revealed that HAX-1 was an independent prognostic factor. In conclusion, this novel study suggested that the overexpression of HAX-1 might contribute to the malignant progression of glioma.

Chemoresistance is associated with overexpression of HAX-1, inhibition of which resensitizes drug-resistant breast cancer cells to chemotherapy

Acquired resistance to standard chemotherapy is the common and critical limitation for cancer therapy. Hematopoietic cell-specific protein 1-associated protein X-1 (HAX-1) has been reported to be upregulated in numerous cancers. However, the role of HAX-1 in oncotherapy remains unclear. In this study, we established MDA-MB-231 cell lines which were resistant to cisplatin (MDA-MB-231/CR) or doxorubicin (MDA-MB-231/DR) to study the chemoresistance in breast cancer. As a result, the HAX-1 which is an apoptosis-associated protein was observed to be overexpressed in both MDA-MB-231/CR and MDA-MB-231/DR compared with the routine MDA-MB-231 cells. Moreover, knockdown of HAX-1 via RNA interference decreased IC50 level of cisplatin by 70.91% in MDA-MB-231/CR cells, and the IC50 level of doxorubicin was decreased by 76.46% in MDA-MB-231/DR cells when the HAX-1 was downregulated. Additionally, we found that the knockdown of HAX-1 induced the release of cytochrome C from mitochondria, resulting in the activation of caspases. Taken together, our study indicates that the overexpression of HAX-1 is essential in the development of chemoresistance in breast cancer. Furthermore, we identify that HAX-1 may become the target for cancer therapy.

MicroRNA-223 Increases the Sensitivity of Triple-Negative Breast Cancer Stem Cells to TRAIL-Induced Apoptosis by Targeting HAX-1

Drug resistance remains a significant challenge in the treatment of triple-negative breast cancer (TNBC). Recent studies have demonstrated that this drug resistance is associated with a group of cells known as cancer stem cells (CSCs), which are believed to determine the sensitivity of tumor cells to cancer treatment. MicroRNAs (miRNAs) are small, non-coding RNAs that play significant roles in normal and cancer cells. MiR-223 reportedly acts as a tumor suppressor in a range of cancers. However, the role of miR-223 in TNBC, especially in triple-negative breast cancer stem cells (TNBCSCs), remains unknown. Here, we found that miR-223 expression was down-regulated in CD44⁺CD24^-/low TNBCSCs compared with non-CSCs. Furthermore, we found that miR-223 overexpression resensitized TNBCSCs to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. The HAX-1 gene, which is located in the mitochondria and functions as an anti-apoptotic protein, was found to be directly regulated by miR-223 in MDA-MB-231 cells. We demonstrated that miR-223 overexpression promoted TRAIL-induced apoptosis through the mitochondria/ROS pathway. In conclusion, our results suggest that miR-223 increases the sensitivity of TNBCSCs to TRAIL-induced apoptosis by targeting HAX-1. Our findings have improved our understanding of the role of miR-223 in TNBC and may contribute to TNBC treatment.