Clin Cancer Res. 2014 Nov 1;20(21):5558-69. doi: 10.1158/1078-0432.CCR-14-1138. Epub 2014 Sep 4.

Galectin-1 mediates radiation-related lymphopenia and attenuates NSCLC radiation response.

Kuo P¹, Bratman SV¹, Shultz DB¹, von Eyben R¹, Chan C¹, Wang Z², Say C¹, Gupta A¹, Loo BW Jr¹, Giaccia AJ¹, Koong AC¹, Diehn M¹, Le QT³.

Author information

1: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
2: University of California, San Diego School of Medicine, La Jolla, California.
3: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California. qle@stanford.edu.

Abstract

PURPOSE:

Radiotherapy can result in lymphopenia, which has been linked to poorer survival. Here, we test the hypothesis that radiotherapy-induced lymphopenia is mediated by a tumor-secreted factor, Galectin-1 (Gal-1), which possesses T-cell proapoptotic activities.

EXPERIMENTAL DESIGN:

Matched Gal-1 wild-type (WT) or null mice were implanted with Lewis lung carcinoma (LLC-1) that either expressed Gal-1 or had Gal-1 stably downregulated. Tumors were irradiated locally and circulating Gal-1 and T cells were measured. Tumor growth, lung metastasis, intratumoral T-cell apoptosis, and microvessel density count were quantified. Thiodigalactoside (TDG), a Gal-1 inhibitor, was used to inhibit Gal-1 function in another group of mice to validate the observations noted with Gal-1 downregulation. Lymphocyte counts, survival, and plasma Gal-1 were analyzed in cohorts of radiotherapy-treated lung [non-small cell lung cancer (NSCLC)] and head and neck cancer patients.

RESULTS:

LLC irradiation increased Gal-1 secretion and decreased circulating T cells in mice, regardless of host Gal-1 expression. Inhibition of tumor Gal-1 with either shRNA or thiodigalactoside ablated radiotherapy-induced lymphopenia. Irradiated shGal-1 tumors showed significantly less intratumoral CD8(+) T-cell apoptosis and microvessel density, which led to marked tumor growth delay and reduced lung metastasis compared with controls. Similar observations were made after thiodigalactoside treatment. Radiotherapy-induced lymphopenia was associated with poorer overall survival in patients with NSCLC treated with hypofractionated radiotherapy. Plasma Gal-1 increased whereas T-cell decreased after radiation in another group of patients.

CONCLUSIONS:

Radiotherapy-related systemic lymphopenia appeared to be mediated by radiotherapy-induced tumor Gal-1 secretion that could lead to tumor progression through intratumoral immune suppression and enhanced angiogenesis.