Lauren E. Ta

Transient Receptor Potential Vanilloid 1 is essential for cisplatin-induced heat hyperalgesia in mice

BackgroundCisplatin is primarily used for treatment of ovarian and testicular cancer. Oxaliplatin is the only effective treatment for metastatic colorectal cancer. Both are known to cause dose related, cumulative toxic effects on the peripheral nervous system and thirty to forty percent of cancer patients receiving these agents experience painful peripheral neuropathy. The mechanisms underlying painful platinum-induced neuropathy remain poorly understood. Previous studies have demonstrated important roles for TRPV1, TRPM8, and TRPA1 in inflammation and nerve injury induced pain.ResultsIn this study, using real-time, reverse transcriptase, polymerase chain reaction (RT-PCR), we analyzed the expression of TRPV1, TRPM8, and TRPA1 induced by cisplatin or oxaliplatin in vitro and in vivo. For in vitro studies, cultured E15 rat dorsal root ganglion (DRG) neurons were treated for up to 48 hours with cisplatin or oxaliplatin. For in vivo studies, trigeminal ganglia (TG) were isolated from mice treated with platinum drugs for three weeks. We show that cisplatin and oxaliplatin-treated DRG neurons had significantly increased in TRPV1, TRPA1, and TRPM8 mRNA expression. TG neurons from cisplatin treated mice had significant increases in TRPV1 and TRPA1 mRNA expression while oxaliplatin strongly induced only TRPA1. Furthermore, compared to the cisplatin-treated wild-type mice, cisplatin-treated TRPV1-null mice developed mechanical allodynia but did not exhibit enhancement of noxious heat- evoked pain responses. Immunohistochemistry studies showed that cisplatin-treated mice had no change in the proportion of the TRPV1 immunopositive TG neurons.ConclusionThese results indicate that TRPV1 and TRPA1 could contribute to the development of thermal hyperalgesia and mechanical allodynia following cisplatin-induced painful neuropathy but that TRPV1 has a crucial role in cisplatin-induced thermal hyperalgesia in vivo.

Clinical Course of Oxaliplatin-Induced Neuropathy: Results From the Randomized Phase III Trial N08CB (Alliance)

PURPOSE Given that the clinical course of oxaliplatin-induced neuropathy is not well defined, the current study was performed to better understand clinical parameters associated with its presentation. METHODS Acute and chronic neuropathy was evaluated in patients receiving adjuvant FOLFOX (fluorouracil, leucovorin, and oxaliplatin) on study N08CB (North Central Cancer Treatment Group, Alliance). Acute neuropathy was assessed by having patients complete daily questionnaires for 6 days with each cycle of FOLFOX. Before each dose of FOLFOX and as long as 18 months after chemotherapy cessation, chronic neurotoxicity was assessed with use of the 20-item, European Organisation for Research and Treatment of Cancer quality-of-life questionnaire for patients with chemotherapy-induced peripheral neuropathy. RESULTS Three hundred eight (89%) of the 346 patients had at least one symptom of acute neuropathy with the first cycle of FOLFOX; these symptoms included sensitivity to touching cold items (71%), sensitivity to swallowing cold items (71%), throat discomfort (63%), or muscle cramps (42%). Acute symptoms peaked at day 3 and improved, although they did not always resolve completely between treatments. These symptoms were about twice as severe in cycles 2 through 12 as they were in cycle 1. For chronic neurotoxicity, tingling was the most severe symptom, followed by numbness and then pain. During chemotherapy, symptoms in the hands were more prominent than they were in the feet; by 18 months, symptoms were more severe in the feet than they were in the hands. Patients with more severe acute neuropathy during the first cycle of therapy experienced more chronic sensory neurotoxicity (P < .0001). CONCLUSION Acute oxaliplatin-induced neuropathy symptoms do not always completely resolve between treatment cycles and are only half as severe on the first cycle as compared with subsequent cycles. There is a correlation between the severities of acute and chronic neuropathies.

A novel and selective poly (ADP-ribose) polymerase inhibitor ameliorates chemotherapy-induced painful neuropathy.

Background Chemotherapy-induced neuropathy is the principle dose limiting factor requiring discontinuation of many chemotherapeutic agents, including cisplatin and oxaliplatin. About 30 to 40% of patients receiving chemotherapy develop pain and sensory changes. Given that poly (ADP-ribose) polymerase (PARP) inhibition has been shown to provide neuroprotection, the current study was developed to test whether the novel PARP inhibitor compound 4a (analog of ABT-888) would attenuate pain in cisplatin and oxaliplatin-induced neuropathy in mice. Results An established chemotherapy-induced painful neuropathy model of two weekly cycles of 10 intraperitoneal (i.p.) injections separated by 5 days rest was used to examine the therapeutic potential of the PARP inhibitor compound 4a. Behavioral testing using von Frey, paw radiant heat, cold plate, and exploratory behaviors were taken at baseline, and followed by testing at 3, 6, and 8 weeks from the beginning of drug treatment. Conclusion Cisplatin-treated mice developed heat hyperalgesia and mechanical allodynia while oxaliplatin-treated mice exhibited cold hyperalgesia and mechanical allodynia. Co-administration of 50 mg/kg or 25 mg/kg compound 4a with platinum regimen, attenuated cisplatin-induced heat hyperalgesia and mechanical allodynia in a dose dependent manner. Similarly, co-administration of 50 mg/kg compound 4a attenuated oxaliplatin-induced cold hyperalgesia and mechanical allodynia. These data indicate that administration of a novel PARP inhibitor may have important applications as a therapeutic agent for human chemotherapy-induced painful neuropathy.

Pilot study of minocycline for the prevention of paclitaxel-associated neuropathy: ACCRU RU221408I.

220 Background: Paclitaxel is associated with both an acute pain syndrome (P-APS) and chronic chemotherapy-induced peripheral neuropathy (CIPN). Preliminary animal data suggest that minocycline may be effective for the prevention of chemotherapy-induced neurotoxicity. The purpose of this pilot study was to investigate the efficacy of minocycline for the prevention of CIPN and P-APS. METHODS Patients with breast cancer were enrolled prior to initiating neoadjuvant or adjuvant weekly paclitaxel for 12 weeks. They were randomized to receive minocycline 200mg on day 1 followed by 100mg twice daily or a placebo, with the same dosing schedule. Patients completed (1) an acute pain syndrome questionnaire daily during chemotherapy, and (2) the EORTC QLQ-CIPN20 questionnaire at baseline, prior to each dose of paclitaxel, and monthly for 6 months post treatment. The primary goal was to obtain pilot data regarding the possible effect of minocycline on the prevention of paclitaxel-induced CIPN and P-APS, to determine if conducting a larger phase III placebo-controlled trial was indicated. Scores obtained from patient questionnaires were converted to a 0-100 scale, where higher scores = better quality of life. RESULTS Forty-seven patients were randomized, 45 of which were evaluable, with a mean age of 55. There were no remarkable differences noted between the two groups for the overall sensory score of the EORTC-CIPN 20 or its individual sub-questions, which evaluated tingling, numbness, or shooting burning pain in hands and feet. However, there was a significant difference in the daily average AUC pain score attributed to P-APS, favoring minocycline (median 96.0 vs 84.3; p = 0.02). Correspondingly, patients receiving minocycline used less opioid pain medications for control of P-APS (0% vs 23%, P = 0.05). Not only were no increased toxicities reported with minocycline, but there was an apparent improvement in fatigue (median AUC 76.7 vs 59.0; P = 0.02). CONCLUSIONS Based on the results of this pilot study, minocycline did not appear to be beneficial for the prevention of CIPN, but did look promising for reducing P-APS. Further study of this effect may be warranted. CLINICAL TRIAL INFORMATION NCT02297412.

Neuropathic Pain: From Mechanism to Clinical Application

A lesion or disease affecting the somatosensory system can cause a wide range of pathophy‐ siologic symptoms including mild or severe chronic pain. Due to the diversity of etiologies giving rise to nervous system damage that generates neuropathic pain, it has become a ubiquitous health concern without respect for geographic or socioeconomic boundaries [1]. Within the developing world, infectious diseases [2-4] and trauma [5] are the most common sources of neuropathic pain syndromes. The developed world, in contrast, suffers more frequently from diabetic polyneuropathy (DPN) [6, 7], post herpetic neuralgia (PHN) from herpes zoster infections [8], and chemotherapy-induced peripheral neuropathy (CIPN) [9, 10]. There is relatively little epidemiological data regarding the prevalence of neuropathic pain within the general population, but a few estimates suggest it is around 7-8% [11, 12]. Despite the widespread occurrence of neuropathic pain, treatment options are limited and often ineffective, leaving many to live with the persistent agony and psychosocial burden associated with chronic pain [13, 14].