Papers of the Week

Most patients with head and neck squamous cell carcinoma (HNSCC) experience pain and pain is associated with a poor prognosis. Despite the frequency and severity of HNSCC pain, current treatments fail to adequately control pain. Cancer-derived small extracellular vesicles (sEVs, size 30-150 nm) are well-positioned to be a mediator of communication between cancer cells and neurons. We hypothesize that cancer-derived sEVs contribute to cancer pain. Mouse oropharyngeal cells were retrovirally transduced to stably express HPV16 viral oncogenes, E6 and E7, H-Ras and luciferase and therefore called mEERL cells. Implantation of mEERL cells into WT mice induces evoked and spontaneous pain. Administration of the sEV release inhibitor GW4869 attenuates the pain in tumor-bearing mice. Additionally, blocking sEV release specifically in the cancer cells, by deleting Rab27a and Rab27b, two proteins required for exosome release, significantly delayed the development of pain hypersensitivity. To test whether cancer-derived sEVs are sufficient to induce pain, we isolated sEVs from mEERL culture and injected them subcutaneously. Injection of isolated sEVs triggers pain hypersensitivity in both sexes. NSAID ketoprofen has no effect on sEVs-induced pain hypersensitivity. In contrast blocking nociceptor neuron activity with the membrane-impermeant lidocaine derivate QX-314 alleviates sEVs-induced pain hypersensitivity. In primary culture of trigeminal ganglion neurons, addition of cancer-derived sEVs induces expression of the neuronal injury marker activating transcription factor 3 (ATF3) and calcium influx measured by calcium imaging in Trpv1 :GCaMP6 mice. Given that sEVs activate TRPV1+ neurons (mostly nociceptors), we examine the impact of TRP1V1+ neuron ablation on cancer pain. Chemical ablation of TRPV1+ neurons by resiniferatoxin (RTX) treatment prevents the development of evoked and spontaneous pain in tumor-bearing mice. Finally, to further explore the potential mechanism of nociception triggered by sEVs, we used published human RNA-sequencing data to investigate the change in gene expression in human cultured sensory neurons exposed to sEVs. Ingenuity pathways analysis (IPA) identified several pathways linked to the initiation of translation, a pathway known to contribute to nociception and neuroplasticity associated with chronic pain. Pharmacological inhibition of translation by rapamycin (mTOR inhibitor), and narciclasine (AMPK activator), alleviates and prevents pain in tumor-bearing mice respectively. In summary, our study shows that cancer-derived sEVs directly activate TRPV1+ neurons to trigger cancer pain and identify new actionable pharmacological targets.