Autotaxin in Breast Cancer: Role, Epigenetic Regulation and Clinical Implications

Profiling of serum metabolome of breast cancer: multi-cancer features discriminate between healthy women and patients with breast cancer

Introduction

The progression of solid cancers is manifested at the systemic level as molecular changes in the metabolome of body fluids, an emerging source of cancer biomarkers.

Methods

We analyzed quantitatively the serum metabolite profile using high-resolution mass spectrometry. Metabolic profiles were compared between breast cancer patients (n=112) and two groups of healthy women (from Poland and Norway; n=95 and n=112, respectively) with similar age distributions.

Results

Despite differences between both cohorts of controls, a set of 43 metabolites and lipids uniformly discriminated against breast cancer patients and healthy women. Moreover, smaller groups of female patients with other types of solid cancers (colorectal, head and neck, and lung cancers) were analyzed, which revealed a set of 42 metabolites and lipids that uniformly differentiated all three cancer types from both cohorts of healthy women. A common part of both sets, which could be called a multi-cancer signature, contained 23 compounds, which included reduced levels of a few amino acids (alanine, aspartate, glutamine, histidine, phenylalanine, and leucine/isoleucine), lysophosphatidylcholines (exemplified by LPC(18:0)), and diglycerides. Interestingly, a reduced concentration of the most abundant cholesteryl ester (CE(18:2)) typical for other cancers was the least significant in the serum of breast cancer patients. Components present in a multi-cancer signature enabled the establishment of a well-performing breast cancer classifier, which predicted cancer with a very high precision in independent groups of women (AUC>0.95).

Discussion

In conclusion, metabolites critical for discriminating breast cancer patients from controls included components of hypothetical multi-cancer signature, which indicated wider potential applicability of a general serum metabolome cancer biomarker.

Methylation signatures as biomarkers for non-invasive early detection of breast cancer: A systematic review of the literature

BACKGROUND

Early detection of breast cancer would help alleviate the burden of treatment for early-stage breast cancer and help patient prognosis. There is currently no established gene panel that utilizes the potential of DNA methylation as a molecular signature for the early detection of breast cancer. This systematic review aims to identify the optimal methylation biomarkers for a non-invasive liquid biopsy assay and the gaps in knowledge regarding biomarkers for early detection of breast cancer.

METHODS

Following the PRISMA-ScR method, Pubmed and Google Scholar was searched for publications related to methylation biomarkers in breast cancer over a five-year period. Eligible publications were mined for key data fields such as study aims, cohort demographics, types of breast cancer studied, technologies used, and outcomes. Data was analyzed to address the objectives of the review.

RESULTS

Literature search identified 112 studies of which based on eligibility criteria, 13 studies were included. 28 potential methylation gene targets were identified, of which 23 were methylated at the promoter region, 1 was methylated in the body of the gene and 4 were methylated at yet to be identified locations.

CONCLUSIONS

Our evaluation shows that at minimum APC, RASSFI, and FOXA1 genes would be a promising set of genes to start with for the early detection of breast cancer, based on the sensitivity and specificity outlined in the studies. Prospective studies are needed to optimize biomarkers for broader impact in early detection of breast cancer.

Autotaxin and Lysophosphatidate Signaling: Prime Targets for Mitigating Therapy Resistance in Breast Cancer

Overcoming and preventing cancer therapy resistance is the most pressing challenge in modern breast cancer management. Consequently, most modern breast cancer research is aimed at understanding and blocking these therapy resistance mechanisms. One increasingly promising therapeutic target is the autotaxin (ATX)-lysophosphatidate (LPA)-lipid phosphate phosphatase (LPP) axis. Extracellular LPA, produced from albumin-bound lysophosphatidylcholine by ATX and degraded by the ecto-activity of the LPPs, is a potent cell-signaling mediator of tumor growth, invasion, angiogenesis, immune evasion, and resistance to cancer treatment modalities. LPA signaling in the post-natal organism has central roles in physiological wound healing, but these mechanisms are subverted to fuel pathogenesis in diseases that arise from chronic inflammatory processes, including cancer. Over the last 10 years, our understanding of the role of LPA signaling in the breast tumor microenvironment has begun to mature. Tumor-promoting inflammation in breast cancer leads to increased ATX production within the tumor microenvironment. This results in increased local concentrations of LPA that are maintained in part by decreased overall cancer cell LPP expression that would otherwise more rapidly break it down. LPA signaling through six G-protein-coupled LPA receptors expressed by cancer cells can then activate virtually every known tumorigenic pathway. Consequently, to target therapy resistance and tumor growth mediated by LPA signaling, multiple inhibitors against the LPA signaling axis are entering clinical trials. In this review, we summarize recent developments in LPA breast cancer biology, and illustrate how these novel therapeutics against the LPA signaling pathway may be excellent adjuncts to extend the efficacy of evolving breast cancer treatments.

Diagnostic value of serum autotaxin level in colorectal cancer

Background: Autotaxin (ATX) is a nucleotide enzyme linked to cell growth, differentiation and migration. This study investigated serum levels of ATX in colorectal cancer (CRC). Methods: The study involved stage I-III CRC diagnosed between December 2020 and 2021, excluding those with neoadjuvant or adjuvant therapy, or metastasis. Healthy volunteers were controls. Serum ATX levels were measured by ELISA and compared. Results: This study included 129 patients (91 in the patient group and 38 in the control group). The optimal cutoff value of ATX for CRC was 169.98 ng/ml, and sensitivity, specificity, positive likelihood ratio and negative likelihood ratio were 91.2% (95% CI: 89.4-96.2), 78.9% (95% CI: 62.7-90.4), 4.33 and 0.11, respectively. Conclusion: The serum ATX level is a useful biomarker for CRC.

ENPP2 inhibitor improves proliferation in AOM/DSS-induced colorectal cancer mice via remodeling the gut barrier function and gut microbiota composition

In our previous multicenter study, we delineated the inherent metabolic features of colorectal cancer (CRC). Therein, we identified a member of the ectonucleotide pyrophosphatase/ phosphodiesterase family (ENPP2) as a significant differential metabolite of CRC. In this study, the role of ENPP2 in CRC has been demonstrated using established in vitro and in vivo models including ENPP2 gene knockdown, and use of the ENPP2 inhibitor, GLPG1690. We found that CRC proliferation was decreased after either ENPP2 gene knockdown or use of ENPP2 inhibitors. We further evaluated the role of GLPG1690 in AOM/DSS-induced CRC mice via intestinal barrier function, macrophage polarization, inflammatory response and microbial homeostasis. Results of immunofluorescence staining and Western blotting showed that GLPG1690 can restore gut-barrier function by increasing the expression of tight junction proteins, claudin-1, occludin and ZO-1. M2 tumor-associated macrophage polarization and colonic inflammation were attenuated after treatment with GLPG1690 using the Azoxymethane/Dextran Sodium Sulfate (AOM/DSS) model. Moreover, 16 S rDNA pyrosequencing and metagenomic analysis showed that GLPG1690 could alleviate gut dysbiosis in mice. Furthermore, administration of GLPG1690 with antibiotics as well as fecal microbiota transplantation assays demonstrated a close link between the efficacy of GLPG1690 and the gut microbiota composition. Finally, results of metabolomic analysis implicated mainly the gut microbiota-derived metabolites of aromatic amino acids in CRC progression. These findings may provide novel insights into the development of small-molecule ENPP2 inhibitors for the treatment of CRC.

High expression of ENPP2 is an independent predictor of poor prognosis in liver cancer

Ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2) has been identified as a potential biomarker in lung and prostate cancers; however, its expression and clinical relevance in hepatocellular carcinoma (HCC) remain incompletely understood. This study comprehensively assessed ENPP2 expression in pan-cancer using bioinformatics. We analyzed the expression of ENPP2 mRNA in primary liver cancer and adjacent tissues of patients with HCC using data from the TCGA database. Cox regression and Kaplan-Meier methods were used to identify clinicopathological factors associated with survival, and the diagnostic value of ENPP2 expression was evaluated using receiver operating characteristic curve analysis. We also validated our findings by performing real-time PCR on clinical liver cancer samples. Furthermore, we conducted gene set enrichment analysis using the Cancer Genome Atlas dataset to gain additional insights into the biological significance of ENPP2 in HCC. High ENPP2 expression in HCC patients is associated with gender and clinical stage, and is a significant prognostic factor for worse outcomes. ENPP2 expression is an independent risk factor for progression-free and disease-specific survival in both cohorts, suggesting its potential as an HCC biomarker. ENPP2's diagnostic value in HCC patients was confirmed by the area under the receiver operating characteristic curve, which was 0.806. real-time PCR analysis validated the higher expression of ENPP2 in clinical liver cancer tissues. Gene set enrichment analysis identified pathways enriched in HCC patients with high ENPP2 expression, including those related to the cell cycle, MTOR and T cell receptor signaling, and phosphatidylinositol signaling systems. We have demonstrated that ENPP2 is highly expressed in HCC and is a potential independent molecular marker for the diagnosis and prognosis of HCC.

Autotaxin production in the human breast cancer tumor microenvironment mitigates tumor progression in early breast cancers

Autotaxin (ATX) is a secreted enzyme that produces extracellular lysophosphatidate in physiological wound healing. ATX is overexpressed in many cancers to promote growth, metastasis, and treatment resistance. However, ATX expression is very low in breast cancer cells, and is instead secreted by the tumor microenvironment (TME). Paracrine ATX expression, and its effects on tumor progression, has not been robustly studied in human breast tumors. In this study, ATX expression was analyzed in over 5000 non-metastatic breast cancers from databases TCGA, METABRIC and GSE96058, dichotomized by the median. Gene set enrichment analysis (GSEA) and the xCell algorithm investigated biological functions of ATX and correlation to TME cell populations. TME ATX production was verified by single cell RNA sequencing. The highest ATX expression occurred in endothelial cells and cancer-associated fibroblasts (P<0.0001). High tumor ATX expression correlated to increased adipocyte, fibroblast, and endothelial cell fractions (P<0.01), and GSEA demonstrated enriched immune system, tumor suppressor, pro-survival, stemness, and pro-inflammatory signaling in multiple gene sets. Tumor mutational burden was decreased, Ki67 scores were decreased, tumor infiltrating immune cell populations increased, and immune cytolytic activity scores increased (all P<0.01) for ATX-high tumors. Overall survival trends favored ATX-high tumors (hazard ratios 0.75-0.80). In summary, in human breast cancers, ATX is produced by the TME, and in non-metastatic tumors, high levels correlate with an anti-tumor phenotype. Because pre-clinical models use aggressive pro-metastatic cell lines where ATX-mediated signaling promotes tumorigenesis, further research is required to verify an anti-to-pro-tumor phenotype switch with breast cancer progression and/or treatment resistance.

Hypoxia Increases ATX Expression by Histone Crotonylation in a HIF-2α-Dependent Manner

Autotaxin (ATX), the key enzyme that generates lysophosphatidic acid (LPA) from lysophosphatidylcholine (LPC), is involved in tumorigenesis through the ATX-LPA axis and is regarded as a valuable target in tumor therapy. Hypoxia is a major feature of solid tumors and contributes to tumor development with striking alterations in the gene expression profile. Here, we show that hypoxia induces ATX expression in a hypoxia-inducible factor (HIF) 2α-dependent fashion in human colon cancer SW480 cells. HIF-2α is directly bound to specific hypoxia response elements (HREs) in the ATX promoter. Under hypoxic conditions, knockout or inhibition of ATX suppressed the migration of SW480 cells, which could be rescued by the addition of LPA, suggesting that the induction of ATX during hypoxia promotes cancer cell migration through the ATX-LPA axis. Further studies showed that ATX expression was induced by HIF-2α through recruiting p300/CBP, which led to crotonylation but not acetylation of histone H3 in the ATX promoter region during hypoxia. Moreover, elevation of cellular histone crotonylation levels could induce ATX expression under normoxic conditions. In conclusion, our findings reveal that ATX is induced in SW480 cells during hypoxia by histone crotonylation in a HIF-2α-dependent manner, while as a novel mechanism of ATX expression regulation, the upregulation of ATX expression by histone crotonylation is not confined to hypoxia.