Bone cancer induced dynamic changes of A-type K+ channels in dorsal root ganglion neurons. Diclofenac antagonized bone cancer pain by upregulating peripheral A-type K+ channels.

Cancer pain is one of the most severe types of chronic pain, and the most common cancer pain is bone cancer pain. The treatment of bone cancer pain remains a clinical challenge. Here, we report firstly that A-type K+ channels in dorsal root ganglion (DRG) are involved in the neuropathy of rat bone cancer pain and are a new target for diclofenac, a nonsteroidal anti-inflammatory drug that can be used for therapy for this distinct pain. There are dynamically functional changes of the A-type K+ channels in DRG neurons during bone cancer pain. The A-type K+ currents that mainly express in isolectin B4-positive small DRG neurons are increased on post-tumor day 14 (PTD 14), then faded but still remained at a higher level on PTD 21. Correspondingly, the expression levels of A-type K+ channel Kv1. 4, Kv3. 4, and Kv4. 3 showed time-dependent changes during bone cancer pain. Diclofenac enhances A-type K+ currents in the DRG neurons and attenuates bone cancer pain in a dose-dependent manner. The analgesic effect of diclofenac can be reversed or prevented by A-type K+ channel blocker 4-AP or pandinotoxin-Kα, also by siRNA targeted against rat Kv1. 4 or Kv4. 3. Repeated diclofenac administration decreased soft tissue swelling adjacent to the tumor and attenuated bone destruction. These results indicate that peripheral A-type K+ channels were involved in the neuropathy of rat bone cancer pain. Targeting A-type K+ channels in primary sensory neurons may provide a novel mechanism-based therapeutic strategy for bone cancer pain.