The Effect of Immunotherapy PD-1 Blockade on Acute Bone Cancer Pain: Insights from Transcriptomic and Microbiomic Profiling

Background: The skeletal system ranks as the third most common site for cancer metastasis, often leading to pain with nociceptive and neuropathic features. PD-1-targeting therapeutic antibodies offer effective cancer treatment but can cause treatment-related acute pain. Understanding the mechanisms of this pain and identifying potential interventions is still a challenge. Methods: We created a murine model of bone cancer pain using Lewis lung carcinoma (LLC) cells and subsequently delivered nivolumab treatment intravenously. Changes in pain thresholds were measured, and micro-CT images of the skeletal system were obtained. Furthermore, in a mouse model, we conducted high-throughput sequencing of the spinal cord/colon transcriptome at the acute phase of bone cancer pain, three hours post-immunotherapy, and high-throughput sequencing of the gut microbiota at the conclusion of the 28-day experiment. Immunofluorescence staining and western blot experiments were employed to determine the activation status of spinal cord microglia and the expression of molecules associated with acute pain occurrence. Results: We noted a marked protective impact of PD-1 inhibition on bone degradation initiated by intratibial administration of Lewis lung carcinoma cells. However, during the treatment period, nivolumab administration consistently resulted in the progression of acute pain in mice, independent of PD-L1 expression. Subsequently, using colonic transcriptomics, we identified an immunopathological pattern of the intestinal phenotype during tumor progression and the acute pain phase, marked by notable changes in interleukin and S100 gene families. Additionally, we characterized alterations in gut microbiota composition and function during the post-immunotherapy phase, revealing a significant decline in beneficial bacteria associated with SCFA production, indicating a potential pivotal intervention point. Notably, we confirmed, through immune fluorescence analysis and transcriptome-assisted western blot experiments, that acute pain following immunotherapy primarily involves the activation of spinal cord microglia and enhanced glycolytic metabolism. Conclusions: Our study underscores fundamental connections among gastrointestinal toxicity, microbiota alterations, and acute cancer pain within the context of tumor immunotherapy. This work provides potential targets for the development of novel analgesics (targeting transcriptomic/microbiota factors), which could enhance the efficacy of bone pain management for cancer patients, ultimately improving their quality of life.