CHECKPOINT IMMUNOTHERAPY ENHANCES PACLITAXEL-INDUCED NEUROPATHIC PAIN

Introduction: The checkpoint immunotherapy with PD-1/PD-L1 inhibitors has achieved satisfactory clinical efficacy for the treatment of solid tumors. However, not all patients are sensitive to immune checkpoint blockade. In this context, the increasing clinical uses in combination with classical chemotherapy agents, as paclitaxel, have been associated with promising responses. Nonetheless, an increase in the incidence of dose-limiting side effects, such as peripheral neuropathy, in which the pathological mechanism in this combined regime is completely unknown, has been observed. Aim: To investigate the effect of immune checkpoint inhibition in the development of paclitaxel-induced peripheral neuropathy. Methodology: Mice were treated with anti-PD-L1 (200 ug), paclitaxel (8mg/ kg), or anti-PD-L1 plus paclitaxel every other day for a total of 4 injections. In another experiment, recombinant PD-L1 (10ug, i.p.) was injected 1 h before formalin or paclitaxel (8 mg/kg, i.p.). The mechanical withdrawal threshold was tested by von Frey hairs. The mice spinal cord, dorsal root ganglion (DRGs), and sciatic nerve tissue were collected to analyze the genic expression of pdl1, tnf, il6, cx3cr1, ccl2, iba and gfap by RT-PCR. The expression of PD-1 in the nervous system was analyzed by immunofluorescence. Furthermore, bone-marrow-derived macrophages from WT and tlr4 knockout mice were stimulated with LPS (100ng/mL) or paclitaxel (30uM). After 24 h the expression of PD-L1 and inflammatory markers (TNF, IL-6 and IL-10) were also analyzed. Results: The combined therapy with anti-PD-L1 plus paclitaxel increased mechanical allodynia and chronic neuropathy development compared to the group treated only with paclitaxel. This effect was associated with higher expression of inflammatory markers (tnf, il6, il1, cx3cr1 and ccl2) in nervous tissue. Notably, we demonstrate that the normal neural tissues including DRG express PD-1. Mechanistically, we demonstrated that paclitaxel induces the expression of PD-L1 on nervous tissue and in macrophages via TLR4. These results suggest that PD-L1/PD-1 axis in the nervous system can potentially inhibit acute and chronic pain. Confirming this hypothesis, we observed that the injection of PD-L1 evoked analgesia in mice submitted to formalin-induced inflammatory pain and paclitaxel. Conclusion: We demonstrated that checkpoint immunotherapy could enhance paclitaxel-induced neuropathic pain by suppressing PD-L1/PD-1 antinociceptive signaling