Euphorbia helioscopia L. inhibits lung tumorigenesis through alleviating exhausted T cell induced by chronic inflammation

Ethnopharmacological relevance: Euphorbia helioscopia L. (ZQ) is a very effective traditional Chinese medicine for treating pneumonia and lung cancer. However, the effects and mechanisms by which ZQ prevents lung tumorigenesis in the presence of chronic inflammation remain unexplored.

Aim: To examine the effects and mechanisms of ZQ in alleviating chronic inflammation-induced T cell exhaustion and inhibiting lung tumorigenesis.

Methods: A mice model of lung tumorigenesis under chronic inflammation conditions was established by repeated administration of lipopolysaccharide (LPS) and exposure to the tobacco carcinogen nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Mice were treated with ZQ ( 0.9, 1.8, and 3.6 g/kg/day) for 25 weeks. Lung pathology and tumor incidence were assessed, and inflammatory cytokine levels in bronchoalveolar lavage fluid (BALF) and serum were measured. Additionally, the proportions of CD3⁺ T, CD4⁺ T, and CD8⁺ T cells and their inhibitory receptors expression were evaluated. In vitro, T cell exhaustion models were induced using inflammatory-conditioned media, followed by treatment with ZQ (0.5, 2, 8 μg/mL). T cell exhaustion markers and characteristics were analyzed, and molecular mechanisms were explored using RNA sequencing and Immunoblotting analysis.

Results: In vivo, ZQ significantly reduced inflammatory infiltration and lung damage, tumor incidence, number, size, and lung and spleen indices in mice. It also markedly lowered the levels of pro-inflammatory cytokines and immunosuppressive cytokines in BALF and serum. Additionally, ZQ improved the proportions of CD3⁺ T, CD4⁺ T, and CD8⁺ T cells and significantly decreased the expression of inhibitory receptors on CD4⁺ T and CD8⁺ T cells in the lung tissues and spleen. In vitro, ZQ effectively alleviated T cell exhaustion induced by the inflammatory environment, marked by reduced expression of inhibitory receptors, increased cytokine secretion, improved proliferation, and enhanced tumoricidal activity. RNA sequencing revealed that ZQ significantly downregulated the JAK-STAT signaling and upregulated stemness-associated pathways. Immunoblotting results indicated that treatment with ZQ markedly reduced the phosphorylation of Signal transducer and activator of transcription 3 (STAT3) and increased the expression of T cell factor -1/7 (TCF1/7).

Conclusion: ZQ inhibits lung tumorigenesis in LPS/NNK-treated mice through alleviating exhausted T cells induced by chronic inflammation, which is attributed to the suppression of STAT3 activation and the maintenance of stemness characteristics in T cells. These findings provide experimental evidence for the potential use of ZQ in preventing and treating lung tumourigenesis in patients with chronic inflammation and the clinical management of lung cancer patients with concomitant chronic inflammation.