Expression of Heart Development Protein With EGF-Like Domains 1 (HEG1) Decorated With Low-Sulfated Keratan Sulfate in Human Malignant Pleural Mesothelioma

Our plain-English summary of Expression of Heart Development Protein With EGF-Like Domains 1 (HEG1) Decorated With Low-Sulfated Keratan Sulfate in Human Malignant Pleural Mesothelioma, by K. Nakashima, H. Hoshino, Z. Zhang, et al (Pathology International, 2025).

The study

• Authors: K. Nakashima, H. Hoshino, Z. Zhang, T.O. Akama, N. Kondo, S. Hasegawa, Y. Sekido, M. Fukushima, T. Ishizuka, M. Kobayashi
• Journal: Pathology International
• Published: 2025;75(10):504-512
• Read it: PubMed · Publisher · Free full text

Abstract

The glycoform of heart development protein with EGF-like domains 1 (HEG1) recognized by the SKM9-2 monoclonal antibody is a useful diagnostic marker for malignant pleural mesothelioma (MPM). The putative glycoform includes core 2 O-glycans carrying sialyl poly-N-acetyllactosamine (LacNAc), but sulfation modifications are undetermined. Since sialyl 6-sulfo LacNAc-capped core 2 O-glycans are expressed in MPM and their structure overlaps with low-sulfated keratan sulfate (KS), we asked whether low-sulfated KS is expressed in MPM and whether HEG1 is decorated with low-sulfated KS. We performed immunohistochemical analysis of 41 MPM cases using anti-KS monoclonal antibodies and endoglycosidases, reversed-phase ion-pair high-performance liquid chromatography analysis of KS/sulfated LacNAc isolated from human pleural tissue, and western blot analysis of HEG1·IgG recombinant fusion proteins secreted from low-sulfated KS-expressing human embryonic kidney cells. Most MPM tissues were stained with anti-low-sulfated KS antibodies and staining was eliminated by endo-β-galactosidase and keratanase II but not by peptide-N-glycosidase F. Disaccharide composition analysis revealed that mono-sulfated LacNAc disaccharide and di-sulfated LacNAc disaccharide accounted for 83.1% and 16.9% of pleural KS/sulfated LacNAc, respectively. Western blot analysis of HEG1·IgG glycoforms indicated that HEG1 functions as a core protein for low-sulfated KS. Thus, HEG1 protein decorated with low-sulfated KS is expressed in MPM.

© 2025 The Author(s). Pathology International published by Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.

In plain English

This Japanese laboratory study examined sugars on HEG1, a protein whose sugar-decorated form, recognized by the antibody SKM9-2, is already used to help diagnose malignant pleural mesothelioma. It did not examine asbestos exposure. The authors stained tumor samples from 41 mesothelioma cases from two hospitals with antibodies detecting a sugar chain called low-sulfated keratan sulfate. In epithelioid-type tumors, 21 of 27 cases (77.8%) were positive with one antibody (294-1B1), and all were positive with a second antibody (R-10G). In sarcomatoid-type tumors, none of 11 cases were positive with 294-1B1, and 3 of 11 (27.3%) were positive with R-10G. Normal pleura from autopsies also carried this sugar. In normal pleural tissue, singly sulfated units made up 83.1% and doubly sulfated units 16.9% of the keratan sulfate and related sulfated sugar measured. Enzyme tests indicated the sugar was most likely attached through structures called core 2 O-glycans. Experiments in engineered human kidney cells indicated HEG1 can carry this sugar. The authors concluded that HEG1 in mesothelioma is likely decorated with low-sulfated keratan sulfate and may be a potential target for new treatments.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study: staining of archived tumor tissue with antibodies and enzymes (immunohistochemistry), chemical analysis of normal pleural tissue (HPLC), and cell-culture experiments with an engineered HEG1 protein (western blot)
• Who was studied: Archived tissue blocks from 41 malignant pleural mesothelioma cases from University of Fukui Hospital and Hospital of Hyogo College of Medicine, Japan, plus normal pleural tissue obtained at autopsy from two cadavers
• Exposure: Not studied. Asbestos exposure is mentioned only in the introduction, as the primary cause of malignant pleural mesothelioma. The study examined sugar structures on tumor proteins, not exposure.
• Main results:
  • Epithelioid-type mesothelioma: 21 of 27 cases (77.8%) were positive with antibody 294-1B1, and all cases (100%) were positive with antibody R-10G
  • Sarcomatoid-type mesothelioma: none of 11 cases (0%) were positive with 294-1B1, and 3 of 11 cases (27.3%) were positive with R-10G
  • Staining in mesothelioma for highly sulfated keratan sulfate (antibody 5D4) was negligible
  • In normal human pleural tissue, mono-sulfated and di-sulfated disaccharides made up 83.1% and 16.9%, respectively, of total KS/sulfated LacNAc
  • Enzyme tests led the authors to conclude that the low-sulfated keratan sulfate in the pleura is most likely carried on core 2 O-glycans
  • Western blot of the engineered HEG1 protein made in cells that produce low-sulfated keratan sulfate indicated that HEG1 serves as a carrier (core protein) for this sugar
• The authors' conclusion: The authors concluded that HEG1 protein expressed in malignant pleural mesothelioma is likely decorated with low-sulfated keratan sulfate. They suggested this form of HEG1 may be a potential target for new therapies such as near-infrared photoimmunotherapy, which would require new antibodies and validation in animal models.
• Limitations the authors state:
  • It is not known whether expression of low-sulfated keratan sulfate contributes to malignancy
  • The R-10G antibody also recognizes related structures other than genuine low-sulfated keratan sulfate

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: HEG1, Pleural Mesothelioma, Monoclonal Antibody.

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