Huntingtin-associated protein 1: a potential biomarker of breast cancer

Research advances in huntingtin-associated protein 1 and its application prospects in diseases

Huntingtin-associated protein 1 (HAP1) was the first protein discovered to interact with huntingtin. Besides brain, HAP1 is also expressed in the spinal cord, dorsal root ganglion, endocrine, and digestive systems. HAP1 has diverse functions involving in vesicular transport, receptor recycling, gene transcription, and signal transduction. HAP1 is strongly linked to several neurological diseases, including Huntington's disease, Alzheimer's disease, epilepsy, ischemic stroke, and depression. In addition, HAP1 has been proved to participate in cancers and diabetes mellitus. This article provides an overview of HAP1 regarding the tissue distribution, cell localization, functions, and offers fresh perspectives to investigate its role in diseases.

Identification and validation of 5-methylcytosine-associated genes in diffuse large B-cell lymphoma

5-methylcytosine modifications play a significant role in carcinogenesis; however, studies exploring 5-methylcytosine-related genes in diffuse large B-cell lymphoma patients are lacking. In this study, we aimed to understand the potential role and clinical prognostic impact of 5-methylcytosine regulators in diffuse large B-cell lymphoma and identify a prognostic biomarker based on 5-methylcytosine-associated genes. Gene expression profiles and corresponding clinical information of diffuse large B-cell lymphoma patients and normal controls were obtained from The Cancer Genome Atlas, Gene Expression Omnibus, and Genotype-Tissue Expression databases. Diffuse large B-cell lymphoma was divided into three clusters according to the 5-methylcytosine regulators, and differentially expressed genes were screened among the three clusters. Univariate Cox and Lasso-Cox regression analyses were used to screen prognostic genes and construct a prognostic risk model. Kaplan-Meier curve analysis, univariate and multivariate Cox regression analyses, and time-dependent receiver operator characteristic curve analysis were used to evaluate prognostic factors. GSVA was used to enrich potential pathways associated with 5-methylcytosine modification patterns. SsGSEA and CIBERSORT were used to assess immune cell infiltration. Six 5-methylcytosine-related genes (TUBB4A, CD3E, ZNF681, HAP1, IL22RA2, and POSTN) were used to construct a prognostic risk model, which was proved to have a good predictive effect. In addition, univariate and multivariate Cox regression risk scores were independent prognostic factors for diffuse large B-cell lymphoma. Further analysis showed that the 5-methylcytosine risk score was significantly correlated with immune cell infiltration and immune checkpoint of diffuse large B-cell lymphoma. Our study reveals for the first time a potential role for 5-methylcytosine modifications in diffuse large B-cell lymphoma, provides novel insights for future studies on diffuse large B-cell lymphoma, and offers potential prognostic biomarkers and therapeutic targets for patients with diffuse large B-cell lymphoma.

Huntingtin Interacting Proteins and Pathological Implications

Huntington's disease (HD) is caused by an expansion of a CAG repeat in the gene that encodes the huntingtin protein (HTT). The exact function of HTT is still not fully understood, and previous studies have mainly focused on identifying proteins that interact with HTT to gain insights into its function. Numerous HTT-interacting proteins have been discovered, shedding light on the functions and structure of HTT. Most of these proteins interact with the N-terminal region of HTT. Among the various HTT-interacting proteins, huntingtin-associated protein 1 (HAP1) and HTT-interacting protein 1 (HIP1) have been extensively studied. Recent research has uncovered differences in the distribution of HAP1 in monkey and human brains compared with mice. This finding suggests that there may be species-specific variations in the regulation and function of HTT-interacting proteins. Understanding these differences could provide crucial insights into the development of HD. In this review, we will focus on the recent advancements in the study of HTT-interacting proteins, with particular attention to the differential distributions of HTT and HAP1 in larger animal models.

Huntingtin-associated protein 1 is a potential tumor suppressor for gastric cancer

BACKGROUND

Gastric cancer is heterogeneous cancer and the causes of this disease are complex. New diagnostic and therapeutic targets are urgently needed to explore. Huntingtin-associated protein 1 (HAP1) is directly related to Huntington's disease (HD). However, patients with Huntington's disease have a lower incidence of cancer. Therefore, we are committed to studying the correlation between HAP1 and gastric carcinogenesis and development.

METHODS AND RESULTS

Immunohistochemical staining, western blot analysis, and RT-qPCR were conducted to explore the localization and expression of HAP1 in gastric cancer. To study the biological significance of HAP1, we overexpressed HAP1 in both MKN28 and AGS cell lines by lentivirus infection. To explore the role of HAP1 in cell proliferation, the cells counting assay, EdU incorporation assay, and colony formation assay were carried out. We performed the wound healing assay and transwell assay to study the cell migration and invasion. To further investigate whether HAP1 could regulate gastric cancer cell death during glucose deprivation, Annexin V-FITC/PI staining was performed. In our study, we elucidated that HAP1 was downregulated in gastric cancer. What's more, overexpressing HAP1 inhibited cell proliferation, cell migration and invasion, and triggered apoptosis during glucose deprivation. More importantly, the antitumor properties and mechanisms of HAP1 have been elucidated further in gastric cancer.

CONCLUSIONS

Taken together, the available evidence implies that HAP1 may serve as a potential tumor suppressor, making it a significant target in preventing and treating gastric cancer. This research provides a theoretical basis for the early diagnosis, clinical targeted therapy, and prognosis evaluation of gastric cancer.

A seven-autophagy-related gene signature for predicting the prognosis of differentiated thyroid carcinoma

Background

Numerous studies have implicated autophagy in the pathogenesis of thyroid carcinoma. This investigation aimed to establish an autophagy-related gene model and nomogram that can help predict the overall survival (OS) of patients with differentiated thyroid carcinoma (DTHCA).

Methods

Clinical characteristics and RNA-seq expression data from TCGA (The Cancer Genome Atlas) were used in the study. We also downloaded autophagy-related genes (ARGs) from the Gene Set Enrichment Analysis website and the Human Autophagy Database. First, we assigned patients into training and testing groups. R software was applied to identify differentially expressed ARGs for further construction of a protein-protein interaction (PPI) network for gene functional analyses. A risk score-based prognostic risk model was subsequently developed using univariate Cox regression and LASSO-penalized Cox regression analyses. The model’s performance was verified using Kaplan-Meier (KM) survival analysis and ROC curve. Finally, a nomogram was constructed for clinical application in evaluating the patients with DTHCA. Finally, a 7-gene prognostic risk model was developed based on gene set enrichment analysis.

Results

Overall, we identified 54 differentially expressed ARGs in patients with DTHCA. A new gene risk model based on 7-ARGs (CDKN2A, FGF7, CTSB, HAP1, DAPK2, DNAJB1, and ITPR1) was developed in the training group and validated in the testing group. The predictive accuracy of the model was reflected by the area under the ROC curve (AUC) values. Univariate and multivariate Cox regression analysis indicated that the model could independently predict the prognosis of patients with THCA. The constrained nomogram derived from the risk score and age also showed high prediction accuracy.

Conclusions

Here, we developed a 7-ARG prognostic risk model and nomogram for differentiated thyroid carcinoma patients that can guide clinical decisions and individualized therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02590-6.

Immunohistochemical expression and neurochemical phenotypes of huntingtin-associated protein 1 in the myenteric plexus of mouse gastrointestinal tract

Huntingtin-associated protein 1 (HAP1) is a neural huntingtin interactor and being considered as a core molecule of stigmoid body (STB). Brain/spinal cord regions with abundant STB/HAP1 expression are usually spared from neurodegeneration in stress/disease conditions, whereas the regions with little STB/HAP1 expression are always neurodegenerative targets. The enteric nervous system (ENS) can act as a potential portal for pathogenesis of neurodegenerative disorders. However, ENS is also a neurodegenerative target in these disorders. To date, the expression of HAP1 and its neurochemical characterization have never been examined there. In the current study, we determined the expression of HAP1 in the ENS of adult mice and characterized the morphological relationships of HAP1-immunoreactive (ir) cells with the markers of motor neurons, sensory neurons, and interneurons in the myenteric plexus using Western blotting and light/fluorescence microscopy. HAP1-immunoreaction was present in both myenteric and submucosal plexuses of ENS. Most of the HAP1-ir neurons exhibited STB in their cytoplasm. In myenteric plexus, a large number of calretinin, calbindin, NOS, VIP, ChAT, SP, somatostatin, and TH-ir neurons showed HAP1-immunoreactivity. In contrast, most of the CGRP-ir neurons were devoid of HAP1-immunoreactivity. Our current study is the first to clarify that HAP1 is highly expressed in excitatory motor neurons, inhibitory motor neurons, and interneurons but almost absent in sensory neurons in myenteric plexus. These suggest that STB/HAP1-ir neurons are mostly Dogiel type I neurons. Due to lack of putative STB/HAP1 protectivity, the sensory neurons (Dogiel type II) might be more vulnerable to neurodegeneration than STB/HAP1-expressing motoneurons/interneurons (Dogiel type I) in myenteric plexus.

Biological functions and potential therapeutic applications of huntingtin-associated protein 1: progress and prospects

Huntington disease (HD) is a single-gene autosomal dominant inherited neurodegenerative disease caused by a polyglutamine expansion of the protein huntingtin (HTT). Huntingtin-associated protein 1 (HAP1) is the first protein identified as an interacting partner of huntingtin, which is directly associated with HD. HAP1 is mainly expressed in the nervous system and is also found in the endocrine system and digestive system, and then involves in the occurrence of the related endocrine diseases, digestive system diseases, and cancer. Understanding the function of HAP1 could help elucidate the pathogenesis that HTT plays in the disease process. Therefore, this article attempts to summarize the latest research progress of the role of HAP1 and its application for diseases in recent years, aiming to clarify the functions of HAP1 and its interacting proteins, and provide new research ideas and new therapeutic targets for the treatment of cancer and related diseases.

Immunohistochemical relationships of huntingtin-associated protein 1 with enteroendocrine cells in the pyloric mucosa of the rat stomach

Huntingtin-associated protein 1 (HAP1) is a neuronal cytoplasmic protein that is predominantly expressed in the brain and spinal cord. In addition to the central nervous system, HAP1 is also expressed in the peripheral organs including endocrine system. Different types of enteroendocrine cells (EEC) are present in the digestive organs. To date, the characterization of HAP1-immunoreactive (ir) cells remains unreported there. In the present study, the expression of HAP1 in pyloric stomach in adult male rats and its relationships with different chemical markers for EEC [gastrin, marker of gastrin (G) cells; somatostatin, marker of delta (D) cells; 5-HT, marker of enterochromaffin (EC) cells; histamine, marker of enterochromaffin-like (ECL) cells] were examined employing single- or double-labelled immunohistochemistry and with light-, fluorescence- or electron-microscopy. HAP1-ir cells were abundantly expressed in the glandular mucosa but were very few or none in the surface epithelium. Double-labelled immunofluorescence staining for HAP1 and markers for EECs showed that almost all the G-cells expressed HAP1. In contrast, HAP1 was completely lacking in D-cells, EC-cells or ECL-cells. Our current study is the first to clarify that HAP1 is selectively expressed in G-cells in rat pyloric stomach, which probably reflects HAP1's involvement in regulation of the secretion of gastrin.

Integration of transcriptome and cistrome analysis identifies RUNX1-target genes involved in pancreatic cancer proliferation

The extremely high proliferation rate of tumor cells contributes to pancreatic cancer (PC) progression. Runt-related transcription factor 1(RUNX1), a key factor in hematopoiesis that was correlated with tumor progression. However, the role of RUNX1 in PC proliferation was still unclear. We found that RUNX1 was significantly upregulated in PC tissues and its expression was negatively associated with prognosis of PC patients in a multicenter analysis according to immunohistochemical (IHC). RUNX1 downregulation in PC resulted in a significantly reduced cell proliferation rate, which was consistent with in vivo subcutaneous tumor formation assay results. RNA-seq and ChIP-seq results revealed that a portion of target genes, including HAP1, GPRC5B, PTPN21, VHL and EN2, were regulated by RUNX1, a finding successfully validated by ChIP-qPCR, qRT-PCR and Western blot. Subsequently, IHC and proliferation assays showed these target genes to be dysregulated in PC, affecting tumor growth. Our data suggest that RUNX1 plays an oncogenic role in tumor proliferation and is a potential prognostic biomarker and therapeutic target for PC.

Cancer: From Wild-Type to Mutant Huntingtin

Huntingtin (HTT) is a scaffold protein mostly known because it gives rise to the severe and incurable inherited neurological disorder Huntington’s disease (HD) when mutated. The Huntingtin gene (HTT) carries a polymorphic trinucleotide expansion of CAGs in exon 1 that ranges from 9 to 35 in the non-HD affected population. However, if it exceeds 35 CAG repeats, the altered protein is referred to as mutant HTT and leads to the development of HD. Given the wide spectrum of severe symptoms developed by HD individuals, wild-type and mutant HTT have been mostly studied in the context of this disorder. However, HTT expression is ubiquitous and several peripheral symptoms in HD have been described, suggesting that HTT is of importance, not only in the central nervous system (CNS), but also in peripheral organs. Accordingly, HTT and mutant HTT may interfere with non-brain-related diseases. Correlative studies have highlighted a decreased cancer incidence in the HD population and both wild-type and mutant HTT have been implicated in tumor progression. In this review, we describe the current evidence linking wild-type and mutant HTT to cancer and discuss how CAG polymorphism, HTT function, and partners may influence carcinogenesis and metastatic progression.

Expression and Localization of Huntingtin-Associated Protein 1 (HAP1) in the Human Digestive System

BACKGROUND

Huntingtin-associated protein 1 (HAP1) is a neuronal protein that is predominantly expressed in neurons in the brain. HAP1 is critical for maintenance of neuronal survival as well as regulation of food intake and body weight in animals. In addition to the critical
role of HAP1 in the central nervous system, HAP1 is also found in endocrine cells, raising an interesting issue of whether HAP1 is expressed in the digestive system.

AIMS

To examine the expression and localization of HAP1 in the human gastrointestinal tract and to compare the differences of the HAP1 expression between benign and malignant tissues in the digestive system.

METHODS

We used Western blot and immunohistochemistry to examine the expression and distribution of HAP1 in the human gastrointestinal tract tissues.

RESULTS

We observed that the presence of HAP1-positive cells in the gastrointestinal tract was not uniform with immunohistochemistry staining. Western blot revealed that only one isoform (75KD) HAP1 was present in the human gastrointestinal system. Interestingly, the expression of HAP1 was higher in the stomach than other regions of the gastrointestinal tract and was at the lowest level in the intestine. We also found that HAP1 was unlikely altered in benign gastric polyps, but was downregulated in pancreatic cancer.

CONCLUSIONS

This is the first study showing the differential expression and location of HAP1 in the human digestive system. These findings suggested that HAP1 may have cell-type-dependent function in the gastrointestinal tract and may serve as a diagnostic marker for pancreatic cancer.

Huntingtin-associated protein 1: Eutherian adaptation from a TRAK-like protein, conserved gene promoter elements, and localization in the human intestine

Background

Huntingtin-associated Protein 1 (HAP1) is expressed in neurons and endocrine cells, and is critical for postnatal survival in mice. HAP1 shares a conserved “HAP1_N” domain with TRAfficking Kinesin proteins TRAK1 and TRAK2 (vertebrate), Milton (Drosophila) and T27A3.1 (C. elegans). HAP1, TRAK1 and TRAK2 have a degree of common function, particularly regarding intracellular receptor trafficking. However, TRAK1, TRAK2 and Milton (which have a “Milt/TRAK” domain that is absent in human and rodent HAP1) differ in function to HAP1 in that they are mitochondrial transport proteins, while HAP1 has emerging roles in starvation response. We have investigated HAP1 function by examining its evolution, and upstream gene promoter sequences. We performed phylogenetic analyses of the HAP1_N domain family of proteins, incorporating HAP1 orthologues (identified by genomic synteny) from 5 vertebrate classes, and also searched the Dictyostelium proteome for a common ancestor. Computational analyses of mammalian HAP1 gene promoters were performed to identify phylogenetically conserved regulatory motifs.

Results

We found that as recently as marsupials, HAP1 contained a Milt/TRAK domain and was more similar to TRAK1 and TRAK2 than to eutherian HAP1. The Milt/TRAK domain likely arose post multicellularity, as it was absent in the Dictyostelium proteome. It was lost from HAP1 in the eutherian lineage, and also from T27A3.1 in C. elegans. The HAP1 promoter from human, mouse, rat, rabbit, horse, dog, Tasmanian devil and opossum contained common sites for transcription factors involved in cell cycle, growth, differentiation, and stress response. A conserved arrangement of regulatory elements was identified, including sites for caudal-related homeobox transcription factors (CDX1 and CDX2), and myc-associated factor X (MAX) in the region of the TATA box. CDX1 and CDX2 are intestine-enriched factors, prompting investigation of HAP1 protein expression in the human duodenum. HAP1 was localized to singly dispersed mucosal cells, including a subset of serotonin-positive enterochromaffin cells.

Conclusion

We have identified eutherian HAP1 as an evolutionarily recent adaptation of a vertebrate TRAK protein-like ancestor, and found conserved CDX1/CDX2 and MAX transcription factor binding sites near the TATA box in mammalian HAP1 gene promoters. We also demonstrated that HAP1 is expressed in endocrine cells of the human gut.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-016-0780-3) contains supplementary material, which is available to authorized users.

HAP1 gene expression is associated with radiosensitivity in breast cancer cells

OBJECTIVES

The purpose of this study was to investigate the relationship between huntingtin-associated protein1 (HAP1) gene and radiation therapy of breast cancer cells.

METHODS

HAP1 gene was transfected into breast cancer MCF-7 cells, which was confirmed by quantitative reverse transcription-polymerase chain reaction analysis (qRT-PCR) and Western blot in vitro. The changes of cell radiosensitivity were assessed by colony formation assay. Apoptosis were examined by flow cytometry. The expressions of two radiation-induced genes were evaluated by Western blot. Tumor growth was investigated in nude mice xenograft models in vivo.

RESULTS

Our data showed that HAP1 gene expression was significantly increased in HAP1-transfected MCF-7 cells in comparison with the parental cells or negative control cells. The survival rate in MCF-7/HAP1 cells was significantly decreased after irradiation (0, 2, 4, 6, 8Gy), compared to cells in MCF-7 and MCF-7/Pb groups in vitro. HAP1 gene increased apoptosis in MCF-7 cells after irradiation. Additionally, the tumor volume and weight in MCF-7/HAP1+RT group were observably lower than in MCF-7/HAP1 group and MCF-7/Pb+RT group.

CONCLUSION

The present study indicated that HAP1 gene expression was related to the radiosensitivity of breast cancer cells and may play an important role in the regulation of cellular radiosensitivity.

Proteomic approaches in biomarker discovery: new perspectives in cancer diagnostics

Despite remarkable progress in proteomic methods, including improved detection limits and sensitivity, these methods have not yet been established in routine clinical practice. The main limitations, which prevent their integration into clinics, are high cost of equipment, the need for highly trained personnel, and last, but not least, the establishment of reliable and accurate protein biomarkers or panels of protein biomarkers for detection of neoplasms. Furthermore, the complexity and heterogeneity of most solid tumours present obstacles in the discovery of specific protein signatures, which could be used for early detection of cancers, for prediction of disease outcome, and for determining the response to specific therapies. However, cancer proteome, as the end-point of pathological processes that underlie cancer development and progression, could represent an important source for the discovery of new biomarkers and molecular targets for tailored therapies.