Proteomic exploration of pain markers in human dorsal root ganglia from spine tumor patients

Introduction: 90% of spine tumors develop metastases with debilitating complications such as sensorimotor complications, neurological deficits, and intractable pain due to epidural spinal cord compression or local nerve root compression. Despite growing literature on nerve-cancer crosstalk, spine tumor patients lack adequate, non-opioid analgesics, as pain management remains secondary to cancer treatment paradigms. Thus, there is a distinct need to profile patient dorsal root ganglia (DRG) to identify potential molecular signatures of cancer-induced pain. Our objective is to demonstrate the ability to generate a protein atlas of human dorsal root ganglia (DRG) from spine tumor patients for proteomic studies to compare molecular markers and the cancer-pain microenvironments of tumor-associated DRGs to their paired histopathologically “normal” DRGs.

Methods: Patients undergoing spine surgery with the Department of Neurosurgery at Duke University were consented for tissue collection. 17 human DRG pairs (one cancer adjacent DRG and one normal DRG from the same patient) were obtained from the thoracic spine of spine tumor patients. DRG pairs were embedded in OCT, sectioned into scrolls, and homogenized to generate protein lysates for downstream standard library prep for proteomics sequencing using the 10X genomics platform. Downstream analysis was performed using differential expression analysis by two-tailed tests. Post-hoc corrections were performed using the Benjamini-Hochberg correction.

Results: Over 10,000 unique proteins were identified between cancer-associated DRGs and paired healthy DRGs. Additional statistical corrections using the Benjamini-Hochberg correction streamlined targeted hits to 900 DEPs. Cancer DRGs showed upregulation in proteins associated with DNA damage, while normal DRGs showed upregulation in proteins associated with normal neuronal function.

Conclusion : Our feasibility pilot generated the highest reported proteome coverage in nerve tissue reported in literature to date. Applications of this protocol can aid in identifying cancer-pain specific analgesic targets and prognostication markers to treatment or analgesic response in spine tumor patients.