Evaluating mesothelin as an immunotherapeutic target for endogenous T cells

Our plain-English summary of Evaluating mesothelin as an immunotherapeutic target for endogenous T cells, by K. Koukoulias, R. Yanagisawa, A.G. Torres Chavez, et al (Frontiers in Immunology, 2026).

The study

• Authors: K. Koukoulias, R. Yanagisawa, A.G. Torres Chavez, P.G. Papayanni, Y. Velazquez, H.S. Lee, S. Vasileiou, A.M. Leen
• Journal: Frontiers in Immunology
• Published: 2026;17:1853409
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Mesothelin (MSLN) is a GPI-anchored cell surface glycoprotein that is overexpressed in various solid tumors, including mesothelioma, triple-negative breast cancer, colon, ovarian and pancreatic cancer, with restricted normal tissue expression.

Methods: To explore the immunogenicity and immunotherapeutic potential of MSLN to T cells with native receptor specificity, 29 individuals of diverse HLA backgrounds were interrogated for T cell activity against MSLN.

Results: Twenty one (72%) subjects (21/29) mounted a specific T cell response when repetitively challenged with MSLN antigen. Reactive cells were Th1-polarized, polyfunctional, predominantly detected in the CD8+ T cell compartment and cytotoxic toward autologous and MSLN+/HLA-matched tumor cell lines in conventional 2D in vitro assays. Furthermore, these cells produced anti-tumor effects in a novel 3D tumor spheroid model system established to evaluate the potency of reactive cells against tumors including pancreatic, cervical, and colorectal cancer and mesothelioma.

Conclusions: These preclinical findings lay the groundwork for further exploration of MSLN as a potential immunotherapeutic target for T cells via the native T cell receptor.

Copyright © 2026 Koukoulias, Yanagisawa, Torres Chavez, Papayanni, Velazquez, Lee, Vasileiou and Leen.

In plain English

This laboratory study did not examine asbestos exposure. Researchers in Houston tested whether people's own T cells, a type of immune cell, can recognize mesothelin, a protein abundant on several cancers including mesothelioma. Blood cells from 29 healthy donors of varied tissue types were repeatedly stimulated with mesothelin fragments. Cells from 21 of the 29 donors developed a mesothelin-specific response, mostly in CD8+ T cells. In 18 donors, these T cells killed the donors' own mesothelin-loaded cells (median 55% specific lysis, range 26-90%, with 40 T cells per target cell). They also killed partially matched cancer cell lines that naturally make mesothelin. In three-dimensional tumor clusters grown from a pancreatic and a cervical cancer line, the T cells reduced tumor signal. Of 153 mesothelin fragments, 44 triggered a response in at least one donor. The authors concluded that these preclinical findings lay the groundwork for further study of mesothelin as a T cell target. They noted that most work used healthy donors' cells rather than patients' cells, and that mesothelin is also present in the pleura, peritoneum and pericardium.

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 (in vitro) study using donor blood cells and human cancer cell lines, including 2D cell-killing assays and a 3D tumor spheroid model
• Who was studied: Blood cells from 29 healthy adult donors of diverse HLA (tissue) types at Baylor College of Medicine, Houston. Also a panel of purchased human cancer cell lines, including the mesothelioma lines NCI-H2052, NCI-H2452 and NCI-H28, and 9 primary pancreatic tumor samples. Study dates are not given.
• Exposure: No asbestos or fiber exposure was studied. In the laboratory, donor T cells were repeatedly stimulated with mixtures of overlapping mesothelin (MSLN) peptides presented on dendritic cells.
• Main results:
  • Mesothelin was detected on 64% of NCI-H2052 and 94% of NCI-H2452 mesothelioma cells. The mesothelioma line NCI-H28 served as a negative control. Seven of 9 primary pancreatic tumor samples were MSLN-positive.
  • T cell lines from 21 of the 29 healthy donors showed anti-mesothelin activity, defined as more than 50 IFN-gamma spot-forming cells per 2x10^5 input cells.
  • In the 21 responders, reactivity was mainly in CD8+ T cells: 17% (plus or minus 4.1) CD8+ IFN-gamma-producing cells versus 3.5% (plus or minus 2) CD4+ IFN-gamma-producing cells.
  • In 18 donors, the T cells killed the donors' own mesothelin-loaded cells: median 55% specific lysis, range 26-90%, at a 40:1 effector-to-target ratio, P less than 0.0001. Killing was reduced by MHC class I blocking antibodies but not by MHC class II blocking antibodies.
  • The T cells also killed partially HLA-matched cancer cell lines that naturally express mesothelin. The lines used as targets included the mesothelioma line NCI-H2452.
  • In 3D tumor spheroids grown from the pancreatic line CFPAC-1 and the cervical line MS751, mesothelin-specific T cells reduced tumor fluorescence. Data were shown from one representative donor.
  • Of 153 mesothelin peptides, 44 (29%) triggered a response in at least one of the 21 responding donors. Eleven peptides were recognized by 3 or more donors, and peptide #30 was recognized by 12 donors.
• The authors' conclusion: The authors concluded that these preclinical findings lay the groundwork for further exploration of mesothelin as a potential target for T cell therapy using the native T cell receptor.
• Limitations the authors state:
  • Expansion and testing were done mainly with cells from healthy individuals, not patients with mesothelin-expressing tumors. The authors stated it cannot be inferred that such cells can be grown from patients or would be as active.
  • Mesothelin is also expressed in normal pleura, peritoneum and pericardium, which is a safety concern. The in vitro safety testing against normal cells was described as data not shown.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelin, Glycoprotein, Mesothelioma, Reactive Mesothelial Hyperplasia, Colorectal Cancer.

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• JNJ-79032421, a Novel Membrane-Restricted Mesothelin-Targeting T Cell-Engaging Bispecific Antibody for the Treatment of Mesothelin-Positive Cancers — K. Smans, T. Nesspor, et al. (2026)
• Anetumab ravtansine: a novel mesothelin-targeting antibody-drug conjugate cures tumors with heterogeneous target expression favored by bystander effect — S. Golfier, C. Kopitz, et al. (2014)
• Evaluating therapeutic plasma exchange and protease inhibitors as mechanisms to reduce soluble mesothelin — K.E.R. Smith, J.R. Ayers-Ringler, et al. (2025)
• Mesothelin as a target for cervical cancer therapy — K. Jöhrens, L. Lazzerini, et al. (2019)
• Mesothelin Immunotherapy for Cancer: Ready for Prime Time? — R. Hassan, A. Thomas, et al. (2016)

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