Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 13, Issue 2, 2013

Actinidia chinensis Planch. is a famous Chinese herbal medicine to treat many diseases such as cancers. Triterpenes, polyphenols and anthraquinones are normally considered as the main constituents for its effects. In this study, eleven known triterpenes were isolated from the root of Actinidia chinensis., and were examined for its antiangiogenic activities. Their structures were elucidated by comprehensive spectroscopic methods, including IR, UV, HR-ESI-MS, and 1D and 2D NMR techniques. The eleven compounds are following: 2α,3α,19-trihydroxyurs-12-en-28-oic acid (1), 2α,3β-dihydroxyurs-12-en-28-oic acid (2), 2α,3α,23-trihydroxyurs-12-en-28-oic acid (3), asiatic acid (4), ursolic acid (5), 2α,3β,19,24-tetrahydroxyurs-12-en-28-oic acid (6), 2α,3β,19-trihydroxyolean-12-en-28-oic acid (7), 2α,3α,24-trihydroxyolean-12-en-28-oic acid (8), oleanolic acid (9), 3β-O-acetyloleanolic acid (10), 2α,23-dihydroxylmicromeric acid (11). All these compounds were evaluated with respect to their antiangiogenic activities utilizing the assays of human umbilical vein endothelial cells (HUVEC) proliferation and tube formation and Ursolic acid (used as control) and compounds 2, 3, 4, and 8 exhibited significant, dose-dependently, antiangiogenic activity in the tested concentration range. Our findings suggest that antitumor action of Actinidia chinensis Planch. is partly via inhibiting tumor angiogenesis by triterpenes, and compounds 2, 3, 4, and 8 as the novel potential antiangiogenic agents are worthy of further translational research.

Metastasis of tumor cells from primary tumor and growth at secondary sites are the major cause of mortality in cancer patients. This event may occur years and even decades after successful removal of the primary tumor and adjuvant therapy. Relapse and metastasis are universally existed in various malignancies. This phenomenon is attributed to a small amount of residual tumor cells remained in host for years, which is called as dormancy. Tumor dormancy is characterized by the balanced cell proliferation and cell death, immune evasion from host, non-angiogenic feature, insufficiency of metastatic capacity, cell cycle arrest as well as resistant to conventional chemotherapy. The molecular expressing profile suggested that dormancy is a state of quiescent cancer stem-like cells (CSCs), which are more resistant to chemotherapy and targeted therapy. Hitherto, the progression on tumor dormancy is relatively slow because there are no proper experimental models and biomarkers for identifying the dormant cells. It is no doubt that clarifying the regulatory mechanism of enter or exit of dormancy will help scientists to develop targeted strategy for eliminating dormant tumor cells, and then hinder the distant relapse and metastasis for various malignancies. This review focuses on tumor dormancy, the association of tumor dormancy with CSCs and strengthens the angiogenic switch for enter or exit of dormancy. It enlightens researchers to explore and develop more specific targeted drugs for clearance of the relapse danger.

In case-control profiling studies, increasing the sample size does not always improve statistical power because the variance may also be increased if samples are highly heterogeneous. For instance, tumor samples used for gene expression assay are often heterogeneous in terms of tissue composition or mechanism of progression, or both; however, such variation is rarely taken into account in expression profiles analysis. We use a prostate cancer prognosis study as an example to demonstrate that solely recruiting more patient samples may not increase power for biomarker detection at all. In response to the heterogeneity due to mixed tissue, we developed a sample selection strategy termed Stepwise Enrichment by which samples are systematically culled based on tumor content and analyzed with t-test to determine an optimal threshold for tissue percentage. The selected tissue-percentage threshold identified the most significant data by balancing the sample size and the sample homogeneity; therefore, the power is substantially increased for identifying the prognostic biomarkers in prostate tumor epithelium cells as well as in prostate stroma cells. This strategy can be generally applied to profiling studies where the level of sample heterogeneity can be measured or estimated.

Recently, the advancement of nanotechnology has had a significant impact on clinical therapeutics. Advances in biocompatible drug carriers using organic/inorganic nanoparticles have enabled safer and more efficient delivery of anti-cancer agents. In particular, nanoparticles designed and fabricated by sophisticated processes can (as drug carriers) deliver precise doses of multiple anti-cancer agents to target cancer cells, improving therapeutic efficacy and minimizing side effects. In addition, a comprehensive understanding of cancer biology, chemo-resistance, cancer relapse, and metastasis is essential for successful development of combination therapy using nanoparticles. In this review, we discuss the species of functional nanoparticles for delivery of anti-cancer agents and their potential to improve chemotherapeutic indices via combination therapy. We also discuss novel therapeutic strategies using functional nanoparticles developed through multidisciplinary collaboration for combination chemotherapy.

Neoadjuvant chemotherapy is provided to patients with locally advanced breast cancer. Its main objective is to bring about a complete pathologic response which is correlated with long term patient survival, a clinical end point of preoperative chemotherapy. Besides, it may downsize the tumor, enabling breast conserving or limited mastectomy. Preoperative chemotherapy also provides the opportunity of assessing the chemosensitivity of the tumor in vivo so that postoperative chemotherapy is tailored according to the outcome of the neoadjuvant chemotherapy. Pathological complete response is considered when there is complete eradication of the local regional disease. Residual disease in the primary focus and/or axilla after preoperative chemotherapy is associated with poor prognosis. Standard preoperative and postoperative specimen collection, handling, processing, and examination are essential components of proper evaluation and reporting of pathologic response to neoadjuvant chemotherapy.

Background and Aim: To determine the correlation of histopathological classification and patient outcomes, we performed a meta-analysis of histological subtypes on postoperative survival in gastric cancer. Methods: A dataset composed of 11073 gastric cancers from 21 publications, combined with our cohort was included in the metaanalysis. We evaluated the association between the 5-year survival rate and the subtypes of gastric cancer based on histological grading or Lauren classification. All literatures were from Pubmed and Embase (up to December 2011). Results: In our cohort from Shanghai Ruijin Hospital, the differentiated gastric cancer revealed a significantly higher accumulative 5-year survival rate, compared to that in poor-differentiated cases (62.6% vs 44.8%, P<0.001). Intestinal-type gastric cancer shown a higher accumulative 5-year survival rate, compared to that in diffuse-type cases (61.7% vs 41.1%, P<0.001). In overall meta-analysis, the poordifferentiated gastric cancer significantly increased the postoperative 5-year death risk, compared to the differentiated cases (OR=1.24, 95% CI 1.13-1.36, P<0.001). The 5-year death risk was increased in the diffuse-type cases relative to the intestinal-type cases (OR=1.29, 95% CI 1.11-1.49, P<0.001). Conclusions: Gastric cancer with a differentiated histology or intestinal-type shows a better prognosis than individual with a poordifferentiated histology or a diffuse-type. Accurate histologic classification is desirable for gastric cancer handling.

Background: Neutropenia and diarrhea are the common dose-limiting toxicities of irinotecan, and uridine diphosphate glucuronosyltransferases (UGTs) gene polymorphisms are considered to be one of the predictive markers of irinotecan related toxicities. This study aims to investigate the association between UGT1A1 gene polymorphisms and irinotecan related toxicities in Chinese Han gastrointestinal cancer patients receiving FOLFIRI regimen chemotherapy. Methods: A total of 94 gastrointestinal cancer patients with metastasis (72 colon and rectum, 20 stomach, 1 pancreas and 1 duodenum), were enrolled from 2007 to 2010 in Shanghai Ruijin Hospital. All patients received standard dosage of FOLFIRI regimen (irinotecan 180mg/m2 d1, CF 200mg/m2 d1-d2, 5-FU 400mg/m2 d1-d2, followed by continuous infusion of 5-FU 600mg/m2 for 22h d1-d2, every 2 weeks). UGT1A1 gene polymorphisms (*60 -3279T>G, *93 -3156G>A, *28 -53TA6>TA7, *6 211G>A) were detected by direct sequencing of DNA extracted from peripheral blood. The incidence of neutropenia, diarrhea, and time to severe toxicity were recorded. The relationship between UGT1A1 gene polymorphisms and toxicities was analyzed. Results: The frequencies of UGT1A1*60 (-3279 G/G), UGT1A1*93 (-3156 A/A), UGT1A1*28 (-53 7/7) and UGT1A1*6 (211 A/A) homozygote were 6.4% (6/94), 1.1% (1/94), 1.1% (1/94) and 2.1% (2/94), respectively. The incidences of grade 3/4 neutropenia and diarrhea were 53.2% (50/94) and 12.8% (12/94), respectively. Comparing those with wild type, patients with UGT1A1*28 or *93 allele had significantly high risk of grade 3/4 diarrhea (6/7, 7/7 vs. 6/6: 27.8% vs. 9.2%, OR=3.791, P=0.034; G/A, A/A vs. G/G: 29.4% vs. 9.1%, OR=4.167, P=0.023). No relationship was found between UGT1A1 allele polymorphism and grade 3/4 neutropenia. The baseline serum total bilirubin was elevated in UGT1A1*28, *93 allele carriers and *60 homozygote, but with no relationship with severe toxicities. Conclusion: In Chinese Han gastrointestinal cancer patients receiving standard FOLFIRI regimen, UGT1A1*28 or *93 allele carriers may have high risk of severe diarrhea.

Epigenetic alterations have been implicated in the development and progression of human cancer. It is noteworthy that epigenetic modifications, in contrast to genetic mutations, are intrinsically reversible. This triggers an impressive interest of researchers in treatment of cancer patients via targeting epigenetic mechanisms, leading to subsequent intensive investigations of epigenetic drugs as a novel therapeutic intervention. DNA methylation, the major form of epigenetic modifications, is catalyzed by the maintenance DNA methyltransferase (DNMT) 1 and/or the de novo methyltransferases DNMT3A and DNMT3B. Aberrant expression of DNMTs and disruption of DNA methylation are closely associated with multiple forms of cancer, although the exact mechanisms underlying this link remain elusive. An array of tumor suppressor genes (TSGs) frequently sustain promoter hypermethylation, which results in epigenetic silencing of these genes and makes cancer cells acquire growth advantages. DNA demethylating agents, re-activating TSGs via inhibiting hypermethylation of their promoter regions, are currently being tested in clinical trials, and several of them are already applied in clinics. DNA demethylating agents, used either alone or in combination with other agents, such as chemotherapeutic drugs and the histone deacetylase inhibitors, have shown to be effective in treatment of cancer, although only in a small set of patients. In this review, we examine and discuss the most recent advances in epigenetic therapy of cancer, with a focus on DNA demethylating agents.

Adrenocortical carcinoma (ACC) is a rare but typically aggressive malignancy. Radical surgery remains the potentially curative option. However, about one third of patients initially present with distant metastases. Regarding to chemotherapy, mitotane alone or in combination with cytotoxic drugs should be the first selection. Meanwhile, a phase lll clinical trial of etoposide, doxorubicin, cisplatin plus mitotane or streptozotocin plus mitotane is currently undergoing worldwide. The study on molecular pathogenesis of ACC is progressing. A lot of targeted therapies are also enrolled in preclinical investigations and clinical trials, including small-molecule tyrosine kinase inhibitors, antiangiogenic compounds. This article introduced the conventional chemotherapy, newly developed targeted therapy for advanced ACC.

Depression is the most common psychiatric syndrome in cancer patients and adversely affects anti-cancer immune system and life quality of patients. Antidepressant desipramine (DMI) is clinically prescribed in the auxiliary treatment of cancer patients. Increasing evidences suggest that DMI has a broad spectrum of target-off biological effects, such as anticancer properties. Our previous study revealed that DMI at the clinical relevant concentrations could induce CHOP-dependent apoptotic death in C6 glioma cells. In this study, we further explored the pro-autophagic effect of DMI in C6 glioma cells and its underlying mechanism. Treatment with DMI could induce autophagic cell death characterized by the formation of autophagosome and the elevated level of autophagic protein Beclin-1 and cellular redistribution of marker LC3. Meanwhile, DMI inhibited the activation of PI3K-AKT-mTOR pathway which is considered as a negative regulator of autophagy. Furthermore, DMI activated PERK-eIF2α and ATF6 of endoplasmic reticulum (ER) stress pathway, while knockdown of PERK with the PERK-specific short interfering RNA (siRNA) could obviously attenuate the autophagy. The results strongly suggested that DMI could induce autophagy through the PERK-ER stress pathway in C6 glioma cells. Our findings provided new insights into another beneficial potential of antidepressant DMI in the adjuvant therapy of cancer.

Pancreatic ductal adenocarcinoma (PDAC) is an almost lethal disease. Thus, it is important to better understand its genetic progression from normal cells through precancerous lesions pancreatic intraepithelial neoplasia (PanIN) to invasive pancreatic cancer. Carriers of a germline mutation in BRCA2 have an increased risk of developing PDAC when compared with the general population. The purpose of our study was to examine the role of BRCA2 dysfuction in the progression of PDAC. Here we generated a novel in vitro model of pancreatic carcinogenesis. Cancerous PanIN-BR1 cells were established by stable transduction with lentiviral-mediated BRCA2 RNA interference in PanIN cell isolated from mice with oncogenic KrasG12D. Our data showed that silencing of BRCA2 promoted cell proliferation, migration and invasion in vitro. The tumorigenic potential of PanIN-BR1 were assessed by xenograft tumor formation in BALB/c nude mice. The expression of PCNA , Snail and Slug in the tumor xenografts was detected by immunohistochemistry. The staining for PCNA, Snail and Slug in PanIN-BR1-formed xenograft tissue was significantly more intense than PanIN-formed xenograft tissue. Microarray assay was also performed. Based on gene expression profiling and further validation by real-time PCR and Western Blot, we found that the expression of Cyclinb2, Cyclina2, Twist1, Wisp1 and Cxcr4 revealed a significant increase in the PanIN-BR1 cells, however, the expression of p15, p16 and Wisp2 showed a significant decrease in the PanIN-BR1 cells, compared to the PanIN cells. Collectively, these data reported here demonstrate that BRCA2 may be a promising therapeutic targets for PDAC progression.

MicroRNAs (miRNAs) and promoter hypermethylation are vital epigenetic mechanisms for transcriptional inactivation of tumor suppressor. IRX1 is a newly identified tumor suppressor gene and hypermethylation involves the decreased expression in gastric cancer. However, the microRNA regulatory mechanism on IRX1 expression is still unclear. In this study, we report an IRX1-targeting miRNA-544, which directly targets 3'-UTR of IRX1 gene by luciferase reporter assay. miR-544 suppresses the protein expression of IRX1 gene by Western blot and immunocytochemistry. Ectopic expression of miR-544 promotes cell proliferation and cell cycle progression significantly in vitro on gastric cancer cells. The study suggests that miR-544 is an oncogenic microRNA in gastric cancer. Over expression of miR-544 contributes to the inactivation and low-expression of IRX1 in gastric cancer. These findings are helpful for clarifying the molecular mechanisms involved in gastric carcinogenesis and indicate that miR-544 is a key regulator in switching cell cycle on or off. miR-544 may be a potential molecular target in miRNA-based strategy on gastric cancer.

Mesothelin, a glycosylphosphatidylinositol (GPI) anchored cell surface protein, is a potential target for antibody-based cancer therapy due to its high expression in mesothelioma, ovarian cancer, pancreatic cancer, cholangiocarcinoma and other cancers. The SS1P immunotoxin and MORAb-009 (amatuximab), a chimeric monoclonal antibody, are currently being evaluated in clinical trials. In this review, we discuss the role of mesothelin in cancer progression and provide new insights into mesothelin-targeted cancer therapy. Recent studies highlight three mechanisms by which mesothelin plays a role in cancer progression. First, mesothelin may aid in the peritoneal implantation and metastasis of tumors through its interaction with mucin MUC16 (also known as CA125). Second, mesothelin may promote cancer cell survival and proliferation via the NF-κB signaling pathway. Finally, mesothelin expression promotes resistance to certain chemotherapy drugs such as TNF-α, paclitaxel, and a combination of platinum and cyclophosphamide. However, its cancerspecific expression makes mesothelin a potential target for monoclonal antibody therapy. New human monoclonal antibodies targeting mesothelin have been isolated by phage display technology and may provide opportunities for novel cancer therapy.

The investigation of chemotherapeutic agents for the treatment of cancer since the early 1940s has resulted in the discovery of over 50 drugs till date. However, most of these drugs result in severe side effects causing physical and mental trauma to patients. In order to eliminate the side effects, search for better and safer drugs has been ongoing for several decades, which has resulted in the discovery of anti-cancer properties of many phytochemicals. Polyphenols represent a unique class of phytochemicals that possess excellent anti- oxidant, anti-inflammatory properties and also modulate cell signalling pathways leading to anti-cancer effects. However, the use of these compounds as anti-cancer agents is not as effective and hence combinations of chemotherapeutic drugs with these molecules have been attempted. Promising results in in vitro and in vivo experiments while using combinations of polyphenols and chemotherapeutic agents open up new avenues for the discovery of the ideal drug combinations for cancer therapy. This review highlights the efficacy of the combination of phytochemicals with synthetic anti-neoplastic drugs over the conventional combinations of anti-neoplastic drugs and the possible interventions in the clinical settings. The review also discusses the inclusion of polyphenols in emerging therapeutic modalities like nanotechnology and photodynamic therapy.

The discovery of cis-platin and its second and third generation analogues created a hope in cancer chemotherapy. Cis-platin and its second generation analogue carboplatin have been used for the treatment of some cancers from a long time. The third generation analogues have superior anti-cancer profiles for curing a few cancers. Unfortunately, certain side effects such as renal impairment, neurotoxicity and ototoxicity etc. are associated with these drugs. But, combination therapy makes these analogues more effective with fewer side effects. In addition, the results of some ongoing clinical trials will make the safety profile clear in near future. The present article describes the current status of cis-platin and its analogues in cancer chemotherapy. In addition, special emphasis has been made on cis-platin discovery, development of second (carboplatin, oxaliplatin, nedaplatin) and third (lobaplatin, heptalatin) generation analogues, comparison of their chemotherapies, mechanism of action, therapeutic status, recent developments and chronology. Moreover, attempts have been made to describe the future perspectives of these drugs in the cancer treatment.

The potential of flavonoids to act as anti-tumor agents has been recognized but not fully understood because flavonoids are acting at several stages in cancer progression with distinct structure-function relationships. A whole family of structurally different flavonoids is herein described by reviewing some critical aspects of their pro-oxidant behavior in vitro/vivo and in cell systems by which they may work as antioxidants. Different classes of flavonoids (chalcones, flavones, isoflavones, flavanols, flavanones and anthocyanins) are synthetically mimicked using natural product structure-antioxidant activity relationships that are relevant for their enhanced function against cancer as well as severe inflammation conditions under which an increased oxidative stress is often implicated. In the context of the common mechanisms of flavonoid action, clinical data on benefits of flavonoids in fighting against cancer are discussed. A structural basis needed to improve antioxidant activity of these agents is elaborated in more detail.

Metformin is a biguanide derivative which is widely prescribed as an oral drug for diabetes mellitus type 2. This old molecule has recently received a new attention because of its therapeutic properties in oncology, that seem to be independent of its action on glycemia homeostasis. The reappraisal of its pharmacological effects was supported by delineation of signaling pathways and more recently clinical trials. Numerous epidemiological studies showed that diabetics have an increased risk of several types of cancer and cancer mortality. Complex relationship between cancer and type 2 diabetes is going to be unraveled and recent observations revealed a significant action of metformin, but not other anti-diabetic agents, on cancer cells. As metformin may act as an anticancer drug through inhibition of mTOR, it might have greater benefice than suggested by insulin lowering alone. This review summarizes major publications on the link between cancer and metformin underscoring new implications of this chemical drug in oncology field. New perspectives about utilization of this molecule in clinical oncological routine, are described, particularly for patients without disturbance of glucose homeostasis. As the epithelial mesenchymal transition (EMT) seems implicated into invasive process and metastasis in cancer, and as metformin is able to inhibit EMT pathways, it is important to highlight cellular mechanisms of metformin.

Acute myeloid leukemia (AML) is a challenging neoplasm that despite therapeutic advances requires efforts to overcome the multidrug resistance (MDR) phenotype, the major cause of relapse. The pterocarpanquinone LQB-118 is a new compound that induces apoptosis in leukemia cells. The objective of this work was to analyze the role of LQB-118 in inhibiting the inhibitor of apoptosis proteins (IAPs), XIAP and survivin, as well as in modulating the subcellular localization of NFκB, in comparison with idarubicin. LQB- 118 was more effective in inducing apoptosis than idarubicin in both AML Kasumi-1 cell line and cells from patients despite their MDR phenotype. LQB-118-induced apoptosis was accompanied by a marked inhibition of IAPs, and cytoplasmatic NFκB subcellular localization. On the other hand, idarubicin increased the IAPs expression and translocated NFκB to the nucleus. The inhibition profile of survivin induced by LQB-118 was comparable to the survivin inhibition profile when we investigated the efficiency of survivin-small interfering RNA (siRNA) treatment. LQB-118 as well as survivin-siRNA contributed similarly to the increase in apoptosis rate of Kasumi-1 cells. The data indicated that there is a functional interaction between the survivin, XIAP and NFκB, which appears to be involved in idarubicin resistance of Kasumi-1 cells. The efficacy of LQB-118 to induce cell death through inhibiting survivin suggests that this IAP may be involved in the chemoresistance phenotype in AML cells. Our findings suggest that LQB-118 might be a promising therapeutic approach for AML patients through survivin downregulation.

Multidrug resistance has became the major obstacle to cancer chemotherapy. Recent studies suggest that quercetin could enhance the response of tumors to chemotherapy although the mechanism by which quercetin enhances the sensitivity of tumor cells to chemical drugs remains elusive. Therefore, in this study, we examined the effects of quercetin on doxorubicin cytotoxicity in human breast cancer cells and investigated the underlying mechanisms. MCF-7 and MCF-7/ dox cells were exposed to doxorubicin, quercetin, or combination of both agents for 36 hours. Cell proliferation, cell invasion, intracellular doxorubicin concentration and expression of hypoxia-inducible factor-1 alpha (HIF-1α) and P-glycoprotein (P-gp) were then assessed. Quercetin had little effect on cell proliferation at concentrations less than 0.7 μM. Compared to treatment with doxorubicin alone, combined treatment with doxorubicin and quercetin (0.7 μM) significantly inhibited cell proliferation and invasion and suppressed the expression of HIF-1α and P-gp. Quercetin (0.7 μM) increased the intracellular doxorubicin concentration and enhanced doxorubicin cytotoxicity as 1.49-fold in MCF-7 cells and 1.98-fold in MCF-7/dox cells. These data suggest that quercetin can increase the chemosensitivity of breast cancer cells to doxorubicin.

The different steps of the topoisomerase I catalytic cycle have been analyzed in the presence of the plant alkaloid thaspine (1- (2-(Dimethylamino)ethyl)-3,8-dimethoxychromeno[5,4,3-cde]chromene-5,10-dione), known to induce apoptosis in colon carcinoma cells. The experiments indicate that thaspine inhibits both the cleavage and the religation steps of the enzyme reaction. The inhibition is reversible and the effect is enhanced upon pre-incubation. Molecular docking simulations of thaspine over topoisomerase I, in the presence or absence of the DNA substrate, show that thaspine, when interacting with the enzyme alone in the closed or in the open state, can bind in proximity of the active residues preventing the cleavage reaction, whilst when docked with the enzyme-DNA cleavable complex intercalates between the DNA bases in a way similar to that found for camptothecin, explaining its religation inhibition. These results unequivocally demonstrate that thaspine targets human topoisomerase I .

A novel process for the preparation of two ketomethylenic antifolates, 2-(2-{4-[(2,4-diamino-pteridin-6-ylmethyl)-amino]- phenyl}-2-oxo-ethyl) pentanedioic acid and 2-(2-{4-[(2,4-diamino-pteridin-6-ylmethyl)-methyl-amino]-phenyl}-2-oxo-ethyl) pentanedioic acid is described herein. Both compounds were compared with methotrexate as inhibitors of human dihydrofolate reductase and thymidylate synthase. The in-vitro and in-vivo results suggest that these novel antifolate inhibitors could potentially constitute effective therapeutic molecules in the treatment of certain cancers and might present a lower toxicity profile than methotrexate.

Oxaliplatin is an agent that is used extensively in gastrointestinal cancer chemotherapy. The agent's major dose-limiting toxicity is peripheral neuropathy that can manifest as a chronic or an acute syndrome. Oxaliplatin-induced acute neuropathy is purportedly caused by an alteration of the biophysical properties of voltage-gated sodium channels. However, sodium channel blockers have not been successful at preventing acute neuropathy in the clinical setting. We report intra-axonal recordings from the isolated rat sciatic nerve preparation under the effect of oxaliplatin. The depolarization phase of single action potentials remains intact with a duration of 0.52 ± 0.02 ms (n=68) before and 0.55 ± 0.01 ms (n=68) after 1-5 h of exposure to 150 μM oxaliplatin (unpaired t-test, P>0.05) whereas there is a significant broadening of the repolarization phase (2.16 ± 0.10 ms, n=68, before and 5.90 ± 0.32 ms after, n=68, unpaired t-test, P<0.05). Apart from changes in spike shape, oxaliplatin also had drastic concentration- and time-dependent effects on the firing responses of fibers to short stimuli. In the intra-axonal recordings, three groups of firing patterns were indentified. The first group shows bursting (internal frequency 90 - 130 Hz, n=88), the second shows a characteristic plateau (at -19.27±2.84 mV, n=31, with durations ranging from 45 - 140 ms depending on the exposure time), and the third combines a plateau and a bursting period. Our results implicate the voltage-gated potassium channels as additional oxaliplatin targets, opening up new perspectives for the pharmacological prevention of peripheral neuropathy.