E Pozzi

Mitochondrial Dysfunction in Chemotherapy-Induced Peripheral Neuropathy (CIPN)

The mitochondrial dysfunction has a critical role in several disorders including chemotherapy-induced peripheral neuropathies (CIPN). This is due to a related dysregulation of pathways involving calcium signalling, reactive oxygen species and apoptosis. Vincristine is able to affect calcium movement through the Dorsal Root Ganglia (DRG) neuronal mitochondrial membrane, altering its homeostasis and leading to abnormal neuronal excitability. Paclitaxel induces the opening of the mitochondrial permeability transition pore in axons followed by mitochondrial membrane potential loss, increased reactive oxygen species generation, ATP level reduction, calcium release and mitochondrial swelling. Cisplatin and oxaliplatin form adducts with mitochondrial DNA producing inhibition of replication, disruption of transcription and morphological abnormalities within mitochondria in DRG neurons, leading to a gradual energy failure. Bortezomib is able to modify mitochondrial calcium homeostasis and mitochondrial respiratory chain. Moreover, the expression of a certain number of genes, including those controlling mitochondrial functions, was altered in patients with bortezomib-induced peripheral neuropathy.

Peripheral neuropathy induced by microtubule-targeted chemotherapies: insights into acute injury and long-term recovery

Chemotherapy-induced peripheral neuropathy (CIPN) is a major cause of disability in cancer survivors. CIPN investigations in preclinical model systems have focused on either behaviors or acute changes in nerve conduction velocity (NCV) and amplitude, but greater understanding of the underlying nature of axonal injury and its long-term processes is needed as cancer patients live longer. In this study, we used multiple independent endpoints to systematically characterize CIPN recovery in mice exposed to the antitubulin cancer drugs eribulin, ixabepilone, paclitaxel, or vinorelbine at MTDs. All of the drugs ablated intraepidermal nerve fibers and produced axonopathy, with a secondary disruption in myelin structure within 2 weeks of drug administration. In addition, all of the drugs reduced sensory NCV and amplitude, with greater deficits after paclitaxel and lesser deficits after ixabepilone. These effects correlated with degeneration in dorsal root ganglia (DRG) and sciatic nerve and abundance of Schwann cells. Although most injuries were fully reversible after 3-6 months after administration of eribulin, vinorelbine, and ixabepilone, we observed delayed recovery after paclitaxel that produced a more severe, pervasive, and prolonged neurotoxicity. Compared with other agents, paclitaxel also displayed a unique prolonged exposure in sciatic nerve and DRG. The most sensitive indicator of toxicity was axonopathy and secondary myelin changes accompanied by a reduction in intraepidermal nerve fiber density. Taken together, our findings suggest that intraepidermal nerve fiber density and changes in NCV and amplitude might provide measures of axonal injury to guide clinical practice.Significance: This detailed preclinical study of the long-term effects of widely used antitubulin cancer drugs on the peripheral nervous system may help guide clinical evaluations to improve personalized care in limiting neurotoxicity in cancer survivors. Cancer Res; 78(3); 817-29. ©2017 AACR.

Susceptibility of different mouse strains to oxaliplatin peripheral neurotoxicity: Phenotypic and genotypic insights

Peripheral neurotoxicity is one of the most distressing side effects of oxaliplatin therapy for cancer. Indeed, most patients that received oxaliplatin experience acute and/or chronic severe sensory peripheral neuropathy. However, despite similar co-morbidities, cancer stage, demographics and treatment schedule, patients develop oxaliplatin-induced peripheral neurotoxicity with remarkably different severity. This suggests individual genetic variability, which might be used to glean the mechanistic insights into oxaliplatin neurotoxicity. We characterized the susceptibility of different mice strains to oxaliplatin neurotoxicity investigating the phenotypic features of neuropathy and gene expression profiles in dorsal root ganglia of six genetically different mice strains (Balb-c, C57BL6, DBA/2J, AJ, FVB and CD1) exposed to the same oxaliplatin schedule. Differential gene expression in dorsal root ganglia from each mice strain were assayed using a genome-wide expression analysis and selected genes were validated by RT-PCR analysis. The demonstration of consistent differences in the phenotypic response to oxaliplatin across different strains is interesting to allow the selection of the appropriate strain based on the pre-defined read-out parameters. Further investigation of the correlation between gene expression changes and oxaliplatin-induced neurotoxicity phenotype in each strain will be useful to deeper investigate the molecular mechanisms of oxaliplatin neurotoxicity.

Neurofilament light chain as disease biomarker in a rodent model of chemotherapy induced peripheral neuropathy

Abstract The objective of this study is to test the feasibility of using serum neurofilament light chain (NfL) as a disease biomarker in Chemotherapy Induced Peripheral Neuropathy (CIPN) since this easy accessible biological test may have a large impact on clinical management and safety of cancer patients. We performed this preclinical study using a well‐characterized rat model based on repeated administration of the cytostatic drug vincristine (VCR, 0.2 mg/kg intravenously via the tail vein once/week for 4 times). Serial NfL serum concentration was measured using the in‐house Simoa NfL assay and peripheral neuropathy onset was measured by sensory and motor nerve conduction studies. Serum NfL measure in untreated and VCR‐treated rats demonstrated a steady, and significant increase during the course of VCR administration, with a final 4‐fold increase with respect to controls (p < .001) when sign of axonopathy and loss of intraepidermal nerve fibers were clearly evident and verified by behavioral, neurophysiological and pathological examination. This simple monitoring approach based on serum NfL concentration measures may be easily translated to clinical practice and should be considered as a putative marker of CIPN severity in a typical oncology outpatient setting. Further studies are needed to validate its utility in cancer patients treated with different neurotoxic drugs.

Ghrelin agonist HM01 attenuates chemotherapy-induced neurotoxicity in rodent models

ABSTRACT Chemotherapy‐Induced Peripheral Neurotoxicity (CIPN) is often dose‐limiting and impacts life quality and survival of cancer patients. Ghrelin agonists have neuroprotectant effects and may have a role in treating or preventing CIPN. We evaluated the CNS‐penetrant ghrelin agonist HM01 in three experimental models of CIPN at doses of 3–30 mg/kg p.o. daily monitoring orexigenic properties, nerve conduction, mechanical allodynia, and intra‐epidermal nerve fiber density (IENFD). In a cisplatin‐based study, rats were dosed daily for 3 days (0.5 mg/kg i.p.) + HM01. Cisplatin treatment induced mechanical hypersensitivity which was significantly reduced by HM01. In a second study, oxaliplatin was administered to mice (6 mg/kg i.p. 3 times/week for 4 weeks) resulting in significant digital nerve conduction velocity (NCV) deficits and reduction of IENFD. Concurrent HM01 dose dependently prevented the decline in NCV and attenuated the reduction in IENFD. Pharmacokinetic studies showed HM01 accumulation in the dorsal root ganglia and sciatic nerves which reached concentrations > 10 fold that of plasma. In a third model, HM01 was tested in preventive and therapeutic paradigms in a bortezomib‐based rat model (0.2 mg/kg i.v., 3 times/week for 8 weeks). In the preventive setting, HM01 blocked bortezomib‐induced hyperalgesia and IENFD reduction at all doses tested. In the therapeutic setting, significant effect was observed, but only at the highest dose. Altogether, the robust peripheral nervous system penetration of HM01 and its ability to improve multiple oxaliplatin‐, cisplatin‐, and bortezomib‐induced neurotoxicities suggest that HM01 may be a useful neuroprotective adjuvant for CIPN.

Oxaliplatin-Induced Peripheral Neurotoxicity: Morphological Characterization In Different Mouse Strains

Oxaliplatin is one of the most effective anticancer drug, particularly employed in the treatment of colorectal cancer, but one of the major limitation in its use is peripheral neurotoxicity. Oxaliplatin induced peripheral neurotoxicity (OIPN) has a high incidence and is frequently long lasting or permanent. Neuropathy is characterized by distal sensory impairment initially in the legs, then extending to the arms. A prominent manifestation of sensitive damage is ataxia. Besides chronic neurotoxicity, many patients experience an acute, rapidly developing cold-induced sensory neuropathy, usually resolving within one week. OIPN clinical manifestations reflect the involvement of dorsal root ganglia (DRG) as primary target of the drug toxicity. Although this assumption is largely accepted and some pathogenetic hypothesis have been proposed, mechanisms at the basis of OIPN need to be clearly defined. OIPN may vary in frequency and severity among different cancer patients despite equal treatment schedules. A genetic susceptibility for more severe oxaliplatin-induced peripheral neurotoxicity (OIPN) has been suggested but never confirmed. Therefore we designed a study to assess the phenotypic differences induced by oxaliplatin treatment in six different mice strains (Balb c, AJ, C57Bl6, FVB, DBA, CD1) aiming at identifying the more and less severely affected. Animals were treated with OHP 3.5 mg/Kg/iv twice weekly x 4 weeks and evaluated before and after treatment. In all strains we performed a multimodal characterization of its neurotoxicity through morphological and morphometrical assessment in caudal nerve and DRG at light and electron microscopy, intra-epidermal nerve fibers density quantification, evaluation of mechanical and cold allodynia/hypoaesteshesia, caudal and digital nerve conduction velocity, activity of wide dynamic range (WDR) neurons of the spinal dorsal horn. Our preliminary data suggest that all the strains show signs of OIPN but not the same modifications in the parameters examined. We will show these results with particular attention to morphological data. This study suggests that genetic variability might have a role in the type and severity of OHP-induced peripheral damage.