Identification of ATP8B1 as a Tumor Suppressor Gene for Colorectal Cancer and Its Involvement in Phospholipid Homeostasis

Flipping the script: Advances in understanding how and why P4-ATPases flip lipid across membranes

Type IV P-type ATPases (P4-ATPases) are a family of transmembrane enzymes that translocate lipid substrates from the outer to the inner leaflet of biological membranes and thus create an asymmetrical distribution of lipids within membranes. On the cellular level, this asymmetry is essential for maintaining the integrity and functionality of biological membranes, creating platforms for signaling events and facilitating vesicular trafficking. On the organismal level, this asymmetry has been shown to be important in maintaining blood homeostasis, liver metabolism, neural development, and the immune response. Indeed, dysregulation of P4-ATPases has been linked to several diseases; including anemia, cholestasis, neurological disease, and several cancers. This review will discuss the evolutionary transition of P4-ATPases from cation pumps to lipid flippases, the new lipid substrates that have been discovered, the significant advances that have been achieved in recent years regarding the structural mechanisms underlying the recognition and flipping of specific lipids across biological membranes, and the consequences of P4-ATPase dysfunction on cellular and physiological functions. Additionally, we emphasize the requirement for additional research to comprehensively understand the involvement of flippases in cellular physiology and disease and to explore their potential as targets for therapeutics in treating a variety of illnesses. The discussion in this review will primarily focus on the budding yeast, C. elegans, and mammalian P4-ATPases.

Type IV P-Type ATPases: Recent Updates in Cancer Development, Progression, and Treatment

Adaptations of cancer cells for survival are remarkable. One of the most significant properties of cancer cells to prevent the immune system response and resist chemotherapy is the altered lipid metabolism and resulting irregular cell membrane composition. The phospholipid distribution in the plasma membrane of normal animal cells is distinctly asymmetric. Lipid flippases are a family of enzymes regulating membrane asymmetry, and the main class of flippases are type IV P-type ATPases (P4-ATPases). Alteration in the function of flippases results in changes to membrane organization. For some lipids, such as phosphatidylserine, the changes are so drastic that they are considered cancer biomarkers. This review will analyze and discuss recent publications highlighting the role that P4-ATPases play in the development and progression of various cancer types, as well as prospects of targeting P4-ATPases for anti-cancer treatment.

Investigation of Gene Networks in Three Components of Immune System Provides Novel Insights into Immune Response Mechanisms against Edwardsiella tarda Infection in Paralichthys olivaceus

As a quintessential marine teleost, Paralichthys olivaceus demonstrates vulnerability to a range of pathogens. Long-term infection with Edwardsiella tarda significantly inhibits fish growth and even induces death. Gills, blood, and kidneys, pivotal components of the immune system in teleosts, elicit vital regulatory roles in immune response processes including immune cell differentiation, diseased cell clearance, and other immunity-related mechanisms. This study entailed infecting P. olivaceus with E. tarda for 48 h and examining transcriptome data from the three components at 0, 8, and 48 h post-infection employing weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network analysis. Network analyses revealed a series of immune response processes after infection and identified multiple key modules and key, core, and hub genes including xpo1, src, tlr13, stat1, and mefv. By innovatively amalgamating WGCNA and PPI network methodologies, our investigation facilitated an in-depth examination of immune response mechanisms within three significant P. olivaceus components post-E. tarda infection. Our results provided valuable genetic resources for understanding immunity in P. olivaceus immune-related components and assisted us in further exploring the molecular mechanisms of E. tarda infection in teleosts.

Genome-wide analyses characterize shared heritability among cancers and identify novel cancer susceptibility regions

BACKGROUND

The shared inherited genetic contribution to risk of different cancers is not fully known. In this study, we leverage results from 12 cancer genome-wide association studies (GWAS) to quantify pairwise genome-wide genetic correlations across cancers and identify novel cancer susceptibility loci.

METHODS

We collected GWAS summary statistics for 12 solid cancers based on 376 759 participants with cancer and 532 864 participants without cancer of European ancestry. The included cancer types were breast, colorectal, endometrial, esophageal, glioma, head and neck, lung, melanoma, ovarian, pancreatic, prostate, and renal cancers. We conducted cross-cancer GWAS and transcriptome-wide association studies to discover novel cancer susceptibility loci. Finally, we assessed the extent of variant-specific pleiotropy among cancers at known and newly identified cancer susceptibility loci.

RESULTS

We observed widespread but modest genome-wide genetic correlations across cancers. In cross-cancer GWAS and transcriptome-wide association studies, we identified 15 novel cancer susceptibility loci. Additionally, we identified multiple variants at 77 distinct loci with strong evidence of being associated with at least 2 cancer types by testing for pleiotropy at known cancer susceptibility loci.

CONCLUSIONS

Overall, these results suggest that some genetic risk variants are shared among cancers, though much of cancer heritability is cancer-specific and thus tissue-specific. The increase in statistical power associated with larger sample sizes in cross-disease analysis allows for the identification of novel susceptibility regions. Future studies incorporating data on multiple cancer types are likely to identify additional regions associated with the risk of multiple cancer types.

ATP8B1: A prognostic prostate cancer biomarker identified via genetic analysis

BACKGROUND

Controlling the asymmetric distribution of phospholipids across biological membranes plays a pivotal role in the life cycle of cells; one of the most important contributors that maintain this lipid asymmetry are phospholipid-transporting adenosine triphosphatases (ATPases). Although sufficient information regarding their association with cancer exists, there is limited evidence linking the genetic variants of phospholipid-transporting ATPase family genes to prostate cancer in humans.

METHODS

In this study, we investigated the association of 222 haplotype-tagging single-nucleotide polymorphisms (SNPs) in eight phospholipid-transporting ATPase genes with cancer-specific survival (CSS) and overall survival (OS) of 630 patients treated with androgen-deprivation therapy (ADT) for prostate cancer.

RESULTS

After multivariate Cox regression analysis and multiple testing correction, we found that ATP8B1 rs7239484 was remarkably associated with CSS and OS after ADT. A pooled analysis of multiple independent gene-expression datasets demonstrated that ATP8B1 was under-expressed in tumor tissues and that a higher ATP8B1 expression was associated with a better patient prognosis. Moreover, we established highly invasive sublines using two human prostate cancer cell lines to mimic cancer progression traits in vitro. The expression of ATP8B1 was consistently downregulated in both highly invasive sublines.

CONCLUSION

Our study indicates that rs7239484 is a prognostic factor for patients treated with ADT and that ATP8B1 can potentially attenuate prostate cancer progression.

Higher Neutrophil-to-Lymphocyte Ratio (NLR) Is a Preoperative Inflammation Biomarker of Poor Prognosis in HIV-Infected Patients with Colorectal Cancer: A Retrospective Study

Background

The serum systemic inflammation biomarkers are known predictors of colorectal cancer (CRC) patient prognosis. However, their significance in human immunodeficiency virus (HIV)-infected patients with CRC has not been studied. To address this gap, we conducted a retrospective study to evaluate the prognostic value of preoperative systemic inflammation biomarkers in HIV-infected patients with CRC.

Methods

The study enrolled 57 patients with colorectal cancer (CRC) and HIV who underwent surgery at the Shanghai Public Health Clinical Center between January 2015 and December 2021. Preoperative tests were conducted, and systemic inflammation biomarkers were measured. The patients were categorized into two groups using the optimal cut-off value. The Kaplan-Meier method and the log-rank test were used to determine overall survival (OS) and progression-free survival (PFS). Multivariate analysis was performed using the Cox proportional regression model. A time-dependent receiver operating characteristic (t-ROC) was used to compare the prognostic abilities of the biomarkers.

Results

The study included 57 HIV-infected CRC patients, with a median age of 60 and a follow-up time ranging from 3 to 86 months. Of the patients, 49 were male and 8 were female. The cumulative three-year OS and PFS rates were 55.0% and 45.0%, respectively. The optimal cut-off value for preoperative NLR was found to be 2.8, which was significantly correlated with lower CD8+ T and CD3+ T lymphocyte counts. Multivariate Cox regression analysis revealed that a low NLR was an independent predictor of better OS and PFS (OS: HR = 0.094, 95% CI: 0.02-0.45, P=0.003; PFS: HR = 0.265, 95% CI: 0.088-0.8, P=0.019). The time-dependent receiver operating characteristic (t-ROC) analysis showed that NLR was a superior systemic inflammation biomarker for predicting the prognosis of HIV-infected CRC patients throughout the observation period.

Conclusion

The preoperative neutrophil-to-lymphocyte ratio (NLR), an easily measurable immune biomarker, may provide useful prognostic information in HIV-infected colorectal cancer (CRC) patients.

Modulation of ATP8B1 gene expression in colorectal cancer cells suggest its role as a tumor suppressor

AIM

The study aims to understand the role of tumor suppressor genes in colorectal cancer initiation and progression.

BACKGROUND

Sporadic colorectal cancer (CRC) develops through distinct molecular events. Loss of the 18q chromosome is a conspicuous event in the progression of adenoma to carcinoma. There is limited information regarding the molecular effectors of this event. Earlier, we had reported ATP8B1 as a novel gene associated with CRC. ATP8B1 belongs to the family of P-type ATPases (P4 ATPase) that primarily function to facilitate the translocation of phospholipids.

OBJECTIVE

In this study, we attempt to implicate the ATP8B1 gene located on chromosome 18q as a tumor suppressor gene.

METHODS

Cells culture, Patient data analysis, Generation of stable ATP8B1 overexpressing SW480 cell line, Preparation of viral particles, Cell Transduction, Generation of stable ATP8B1 knockdown HT29 cell line with CRISPR/Cas9, Generation of stable ATP8B1 knockdown HT29 cell line with shRNA, Quantification of ATP8B1 gene expression, Real-time cell proliferation and migration assays, Cell proliferation assay, Cell migration assay, Protein isolation and western blotting, Endpoint cell viability assay, Uptake and efflux of sphingolipid, Statistical and computational analyses.

RESULTS

We studied indigenous patient data and confirmed the reduced expression of ATP8B1 in tumor samples. CRC cell lines were engineered with reduced and enhanced levels of ATP8B1, which provided a tool to study its role in cancer progression. Forced reduction of ATP8B1 expression either by CRISPR/Cas9 or shRNA was associated with increased growth and proliferation of CRC cell line - HT29. In contrast, overexpression of ATP8B1 resulted in reduced growth and proliferation of SW480 cell lines. We generated a network of genes that are downstream of ATP8B1. Further, we provide the predicted effect of modulation of ATP8B1 levels on this network and the possible effect on fatty acid metabolism-related genes.

CONCLUSION

Tumor suppressor gene (ATP8B1) located on chromosome 18q could be responsible in the progression of colorectal cancer. Knocking down of this gene causes an increased rate of cell proliferation and reduced cell death, suggesting its role as a tumor suppressor. Increasing the expression of this gene in colorectal cancer cells slowed down their growth and increased cell death. These evidences suggest the role of ATP8B1 as a tumor suppressor gene.

ATP8B1 Knockdown Activated the Choline Metabolism Pathway and Induced High-Level Intracellular REDOX Homeostasis in Lung Squamous Cell Carcinoma

Simple Summary

We found that low expression of ATP8B1 was associated with poor prognosis, and involved in the dysregulation of glutathione (GSH) synthesis and choline metabolism in lung squamous cell carcinoma (LUSC) samples of The Cancer Genome Atlas (TCGA) and Tianjin Medical University Cancer Institute and Hospital (TJMUCH) cohort. We further constructed ATP8B1 knockdown of LUSC cell lines H520^SH-ATP8B1 and SK-MES-1^SH-ATP8B1 to investigate how ATP8B1 knockdown promoted cell proliferation, migration, and invasion in vitro and in vivo via upregulation of the CHKA-dependent choline metabolism pathway. We identified that ATP8B1 knockdown and CHKA upregulation can lead to mitochondrial dysfunction and high reduction-oxidation (REDOX) homeostasis, which may be involved in the roles of cardiolipin in maintaining mitochondrial dynamics and phospholipid homeostasis. Therefore, we proposed ATP8B1 as a novel predictive biomarker in LUSC and targeting ATP8B1-driven specific metabolic disorder might be a promising therapeutic strategy for LUSC.

Abstract

The flippase ATPase class I type 8b member 1 (ATP8B1) is essential for maintaining the stability and polarity of the epithelial membrane and can translocate specific phospholipids from the outer membrane to the inner membrane of the cell. Although ATP8B1 plays important roles in cell functions, ATP8B1 has been poorly studied in tumors and its prognostic value in patients with lung squamous cell carcinoma (LUSC) remains unclear. By investigating the whole genomic expression profiles of LUSC samples from The Cancer Genome Atlas (TCGA) database and Tianjin Medical University Cancer Institute and Hospital (TJMUCH) cohort, we found that low expression of ATP8B1 was associated with poor prognosis of LUSC patients. The results from cellular experiments and a xenograft-bearing mice model indicated that ATP8B1 knockdown firstly induced mitochondrial dysfunction and promoted ROS production. Secondly, ATP8B1 knockdown promoted glutathione synthesis via upregulation of the CHKA-dependent choline metabolism pathway, therefore producing and maintaining high-level intracellular REDOX homeostasis to aggravate carcinogenesis and progression of LUSC. In summary, we proposed ATP8B1 as a novel predictive biomarker in LUSC and targeting ATP8B1-driven specific metabolic disorder might be a promising therapeutic strategy for LUSC.