Unveiling new therapeutic targets for esophageal cancer treatment through single-cell transcriptomics: pH-responsive nanobubbles enhance the efficacy of 125I radiotherapy.

OBJECTIVE: This study investigates the mechanisms underlying the enhancement of radiosensitivity in esophageal carcinoma (ESCC) cells through the coupling of pH-responsive nanobubbles with Nivolumab, a CD8(+) T cell activator. METHODS: Single-cell transcriptomics analysis was used to identify radiation-sensitive cancer cells in ESCC tissues. An in situ mouse model of ESCC was established to study the effects of radiation therapy on CD8(+) T cells using high-throughput sequencing. Machine learning algorithms were employed to identify key genes associated with ESCC. CRISPR/Cas9 technology was used to knock out key genes, while lentivirus was used to overexpress them. In vitro assays were conducted to evaluate the impact of these key genes on CD8(+) T cell activity, proliferation, migration, invasion, apoptosis, and sensitivity to radiation therapy. Nanobubbles conjugated with antibodies were prepared and their uptake by CD8(+) T cells was observed. A humanized mouse model of ESCC was used to assess the effectiveness of the nanobubbles in enhancing CD8(+) T cell activity and cytotoxicity. RESULTS: The analysis revealed a close relationship between tumor cell radiosensitivity and CD8(+) T cells. The key gene PD-1 was found to play a resistant role in the response to radiation therapy. PD-1 inhibited the activity and cytotoxicity of CD8(+) T cells in ESCC tissues. The development of pH-responsive nanobubbles conjugated with Nivolumab (αPD1-O(2)-nivolumab (NB), enhanced CD8(+) T cell cytotoxicity and increased the sensitivity of ESCC cells to radiation therapy. The release of oxygen by the nanobubbles further improved the efficacy of Nivolumab. In vivo experiments confirmed that αPD1-O(2)-NB increased CD8(+) T cell activity and cytotoxicity, thereby improving the sensitivity of ESCC cells to radiation therapy. CONCLUSION: PD-1 promotes resistance to radiation therapy in ESCC cells by suppressing the activity and cytotoxicity of CD8(+) T cells. pH-responsive αPD1-O(2)-NB enhance CD8(+) T cell activity and improve the sensitivity of ESCC cells to radiation therapy. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12951-025-03552-2.