Cytotoxicity Of Oxaliplatin Research Articles

THE HDAC INHIBITOR SODIUM PHENYLBUTYRATE ENHANCES THE CYTOTOXICITY INDUCED BY 5-FLUOROURACIL, OXALIPLATIN, AND IRINOTECAN IN COLORECTAL CANCER CELL LINES

Objective: The main objective of this study was to evaluate the ability of sodium phenylbutyrate (NaPB) to enhance the cytotoxicity of 5-fluorouracil, oxaliplatin, and irinotecan against colorectal cancer cell lines expressing wild-type and mutant p53.Methods: The antiproliferative effect of NaPB alone or in combination with 5-fluorouracil, oxaliplatin, or irinotecan in HCT-116 and HT-29 colorectal cancer cell lines was investigated using the MTT cell proliferation assay. IC50 values were calculated using Compusyn Software 1.0 (Combosyn Inc.). Synergy values (R) were calculated using the ratio of IC50 of each primary drug alone divided by combination IC50s. For each two pairs of experiments, student’s t-test was used for analysis. In combination studies, one-way ANOVA test; Tukey post-hoc testing was performed using R 3.3.2 software. P-value<0.05 was considered significant.Results: NaPB inhibited the growth of HCT-116 and HT-29 cell lines in a dose-dependent manner (IC50s 4.7 mmol, and 10.1 mmol, respectively). HT-29 cell lines (mutant p53) were more sensitive to NaPB at low concentrations (<4 mmol). Moreover, the addition of NaPB to HCT-116 and HT-29 with 5-fluorouracil, oxaliplatin, or irinotecan synergistically induced the antiproliferative effect (R>1.6, p-value<0.05).Conclusion: NaPB enhanced the cytotoxicity of conventional chemotherapy against colorectal cancer cell lines harboring wild-type or mutant p53. Thus NaPB is a promising potential adjuvant chemotherapy in colorectal cancer.

Wogonin exacerbates the cytotoxic effect of oxaliplatin by inducing nitrosative stress and autophagy in human gastric cancer cells

BackgroundGastric cancer remains one of the leading cause of death in the world. Drug combinations are potential approaches to provide more efficient treatments that minimize side effects. PurposeWe investigated the pharmacological effects of the combination of wogonin with oxaliplatin on gastric cancer cells in vitro and in vivo. Methods and ResultsIn the present study, we found that wogonin enhanced the cytotoxicity of oxaliplatin; the drug combination resulted in strong synergistic inhibition of the cell viability in BGC-823 cells and in a zebrafish xenograft model. Interestingly, the combined treatment of wogonin and oxaliplatin modulated the expression of phospho-JNK (Thr183/Tyr185), phospho-ULK1 (Ser555) and the formation of LC3II. Confocal imaging data consistently showed that wogonin exacerbates the oxaliplatin-induced dissipation of the mitochondrial membrane potential (ΔΨm) and formation of peroxynitrite in BGC-823 cells. Moreover, wogonin allows a reduction in oxaliplatin dose when they are combined; therefore, it is a relevant strategy for reducing the side effects of oxaliplatin while achieving the same response. ConclusionThese results suggest that wogonin can be a potential therapeutic candidate for enhancing the efficacy of oxaliplatin in gastric cancer treatment.

Ginsenoside Rg3 targets cancer stem cells and tumor angiogenesis to inhibit colorectal cancer progression in vivo.

Anti-angiogenic therapy has been successfully applied to treat colorectal cancer (CRC). Ginsenoside Rg3, derived from the Chinese herb ginseng, has anti-vascularization effects and can inhibit tumor growth and metastasis, and can sensitize cancer cells to chemotherapy. Therefore, in the present study, we investigated whether Rg3 could be appropriate for CRC treatment. Growth of CRC cells was assessed by an MTT (methyl thiazolyl tetrazolium) assay in vitro and using orthotopic xenograft models in vivo. mRNA expression was evaluated using real-time PCR. Protein levels were tested by western blotting, flow cytometry and immunohistochemistry. Migration was determined using a wound-healing assay. Stemness was further confirmed using a plate clone formation assay. We found that Rg3 repressed the growth and stemness of CRC cells both in vitro and in vivo. Rg3 also impaired the migration of CRC cells in vitro. Rg3 downregulated the expressions of angiogenesis-related genes, and repressed the vascularization of CRC xenografts. In addition, Rg3 strengthened the cytotoxicity of 5-Fluorouracil and oxaliplatin against orthotopic xenografts in vivo. Moreover, Rg3 downregulated the expressions of B7-H1 and B7-H3, high expressions of which were associated with reduced overall survival (OS) of CRC patients. Hence, Rg3 not only repressed the growth and stemness of CRC cells, but could also remodel the tumor microenvironment through repressing angiogenesis and promoting antitumor immunity. Therefore, Rg3 could be a novel therapeutic for the CRC treatment.

Reversion of resistance to oxaliplatin by inhibition of p38 MAPK in colorectal cancer cell lines: involvement of the calpain / Nox1 pathway.

Oxaliplatin is a major treatment for metastatic colorectal cancer, however its effectiveness is greatly diminished by the development of resistances. Our previous work has shown that oxaliplatin efficacy depends on the reactive oxygen species (ROS) produced by Nox1. In this report, we investigated Nox1 involvement in the survival mechanisms of oxaliplatin resistant cell lines that we have selected. Our results show that basal ROS production by Nox1 is increased in resistant cells. Whereas the transitory Nox1-dependent production of superoxide contributes to the cytotoxicity of oxaliplatin in sensitive cells, oxaliplatin treatment of resistant cells leads to a decrease in the production of superoxide associated with an increase of H2O2 and a decreased cytotoxicity of oxaliplatin. We have shown that calpains regulate differently Nox1 according to the sensitivity of the cells to oxaliplatin. In sensitive cells, calpains inhibit Nox1 by cleaving NoxA1 leading to a transient ROS production necessary for oxaliplatin cytotoxic effects. In contrast, in resistant cells calpain activation is associated with an increase of Nox1 activity through Src kinases, inducing a strong and maintained ROS production responsible for cell survival. Using a kinomic study we have shown that this overactivation of Nox1 results in an increase of p38 MAPK activity allowing the resistant cells to escape apoptosis. Our results show that the modulation of Nox1 activity in the context of anticancer treatment remains complex. However, a strategy to maximize Nox1 activation while inhibiting the p38 MAPK-dependent escape routes appears to be an option of choice to optimize oxaliplatin efficiency.

Deficiency of gap junction composed of connexin43 contributes to oxaliplatin resistance in colon cancer cells.

Although comprehensive strategies in the treatment of colorectal cancer have been developed for a number of years, the five-year survival rate of metastatic colon cancer remains less than 10%. Oxaliplatin, a commonly used chemotherapeutic agent for metastatic colon cancer, improves the response rate of patients and prolongs patients' progression-free survival. However, the generation of resistance limits the clinical application of oxaliplatin, and the mechanisms of this remain unclear. The present study mainly investigated the effect of the gap junction (GJ) composed of connexin43 (Cx43) on oxaliplatin cytotoxicity in colon cancer cells. Three different methods with distinct mechanisms were used to change the function of Cx43 GJs, including cell culture at different densities, pretreatment with a specific inhibitor or enhancer, and special gene knockdown, to observe the cytotoxicity of oxaliplatin and the level of reactive oxygen species (ROS) mediated by Cx43 GJs. The results revealed that the cytotoxicity of oxaliplatin and the level of ROS were decreased with the downregulation of Cx43 GJ function, but exacerbated with the upregulation of Cx43 GJ function. Moreover, ROS scavenging with N-acetyl-L-cysteine and apocynin decreased the cytotoxicity of oxaliplatin. We concluded that the loss of GJ composed of Cx43 contributed to the resistance of oxaliplatin in colon cancer cells, and the mechanism was associated with intracellular ROS alternation.

Abstract 1188: Sodium phenylbutyrate has an antineoplastic effect and enhances the cytotoxicity of 5-fluorouracil and irinotecan in colorectal cancer cell lines

Abstract Colorectal cancer is the third most common cancer in the world and it is the second leading cause of cancer-related deaths in the United States. About 25% of colorectal cancer cases present with metastases at time of diagnosis and 50% of patients who undergo surgery will ultimately develop metastatic disease. Consequently, adjuvant chemotherapy is required in many cases and it aims to prevent tumor progression and metastasis. Resistance to chemotherapy is the biggest obstacle in the treatment path of advanced colorectal cancer. Thus, highlighting the urgent need for the identification of new therapeutic agents that can enhance the cytotoxicity of the currently approved anticancer drugs. Sodium phenylbutyrate (NaPB), a salt of a short chain fatty acid that is used for treatment of urea cycle disorders, is under investigation for its antineoplastic potential. NaPB acts as a histone deacetylase inhibitor and it has been shown to be associated with reduced ER stress and enhanced JNK signaling pathway. This indicates that NaPB may enhance the cytotoxicity of the currently approved agents for colorectal cancer including oxaliplatin, 5-fluorouracil, and irinotecan. The aims of this study were to identify the antineoplastic potential of NaPB in colorectal cell lines, and to identify its effect on the cytotoxicity of oxaliplatin, 5-fluorouracil, and irinotecan. MTT proliferation assay showed that NaPB possessed a concentration dependent killing effect against HCT-116 and HT-29 colorectal cancer cell line (IC50 values were 5 and 10 mM respectively). Moreover, at clinically achievable and nontoxic concentration (2.5 mM), NaPB showed a synergistic effect in HCT-116 on 5-fluorouracil (R=14.176, p=0.006), on irinotecan (R=53.86, p=0.0117), and on oxaliplatin (R=20, p=0.004), but resulted in extensive cytotoxicity when used at 5 mM and 10 mM. In HT-29 cells, NaPB at concentrations 5 mM and 10 mM, showed a synergistic effect on 5-fluorouracil (R=5.5, p<0.001; and R=125, p<0.001 respectively), on irinotecan (R=5.7, p=0.016; and R=21.3, p=0.018 respectively), and on oxaliplatin (R=2.4, p=0.003; and R=3, p=0.002 respectively). The addition of NaPB at concentration of 20 mM to the previous drugs resulted in profound cytotoxic effect toward HT-29 cells. As a conclusion, NaPB is a promising new adjuvant antineoplastic agent that can be used to enhance the cytotoxicity of 5-fluorouracil, irinotecan, and oxaliplatin in colorectal cancer. Citation Format: Maha Al-Keilani, Ruba Darweesh. Sodium phenylbutyrate has an antineoplastic effect and enhances the cytotoxicity of 5-fluorouracil and irinotecan in colorectal cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1188. doi:10.1158/1538-7445.AM2017-1188

The Cytoprotective Effect of Crocin on Oxaliplatin Treated VERO cell line In Vitro Study

AbstractBackgroundCancer is a disease characterized by a shifted in the control mechanism that governs cell survival, proliferation and differentiation.There are many types of treatment to the cancer like surgery, radiation, chemotherapy, immunotherapy and others. Each of these above treatments has its indication effect and has Sid effect and / or adverse effect. The chemotherapy is one type of this treatment to the cancer that have the indication effect, side effect and adverse effect. There are many type of chemotherapeutic agent that used for this type of cancer one of them it is platinum compound (cisplatin, oxaliplatin and others).There are two types of limitation in the use of these agents one of them is the side effect which is neurotoxicity, Ototoxicity, nephrotoxicity, and etc. and the second one is the resistance of cancer cells to these agents.Aim of the studyTaste the cytoprotection effect of Crocin on oxaliplatin treated VERO cell lineMaterial and methods:-By using the tissue culture techniques which is a newly used techniques to check the cytotoxicity of many compound and the expected mechanism of action these techniques made a good jump in the research in many fieldIn this study we use VERO cell line and after exposure of this cell line firstly to different concentrations of oxaliplatin ( 1, 0.5, 0.25 and 0.125 mg/ml) for 48hr, secondly to different concentrations of Crocin (0.5, 0.25 and 0.125 mg/ ml ) for 48hr. And thirdly to mix concentrations of oxaliplatin and Crocin in 48hr for the VERO cell line and measure the cytotoxicity of these exposures by crystal violet test (C.V. test) to show and compare the effect of these agents specially the Crocin.The oxaliplatin has cytotoxic effect, its inhibitory concentration 50% (IC50) in 48hr is (0.031mg/ml) which is the maximum cytotoxic effect in vitro. While the Crocin don’t have cytotoxic effect at this tested concentration and for this cell line. After mixed different concentration of Crocin with different concentration of oxaliplatin the cytotoxicity of oxaliplatin reduce significantly.Conclusion:-From our study we can conclude the following:-The Crocin has cytoprotective effect. The Crocin has no anti tumor and anti proliferative activity within these tasted concentration and this cell line

Connexin 43 enhances oxaliplatin cytotoxicity in colorectal cancer cell lines.

Oxaliplatin, a platinum-based chemotherapeutic agent, is an important first-line drug in the treatment of colorectal cancers, but drug resistance causes treatment failure. It has been reported that gap junctional communication can enhance the cytotoxicity of platinum drugs. The gap junction formed of connexin proteins provides a direct pathway for electrical and metabolic cell-cell interaction. The voltage-dependent gating of gap junction allows small hydrophilic molecules and ions to permeate to adjacent cells. Connexin 43 is a diagnostic marker for cancer therapy and the predominant connexin isoform in many cell types. The purpose of this study was to investigate the role of connexin 43 in oxaliplatin activity by using colorectal cancer cell lines. LoVo and HCT116 cell lines were used for analysis. Connexin 43 expression was confirmed by western blot and immunocytochemistry. MTT, western blot, "Parachute" dye-coupling assays and reactive oxygen species measurement were used to detect cytotoxicity and the inhibition of connexin 43 expression induced by oxaliplatin. Results showed that connexin 43 enhanced oxaliplatin cytotoxicity through gap junctional communication function and high concentration of oxaliplatin inhibited connexin 43 expression to counteract its cytotoxicity. This study suggested that connexin 43 could be considered a molecular target of oxaliplatin activity in colorectal cancer.

Copper transporter 1 in human colorectal cancer cell lines: Effects of endogenous and modified expression on oxaliplatin cytotoxicity

Oxaliplatin-based chemotherapy is the mainstay for the treatment of advanced colorectal cancer. Copper transporter proteins have been implicated in the transport of platinum-based anticancer drugs, but their expression in human colorectal cancer cell lines and roles in controlling their sensitivity to oxaliplatin are not well studied or understood. The endogenous and modified expression of copper uptake transporter 1 (hCTR1) was studied in a panel of human colorectal cancer cell lines (DLD-1, SW620, HCT-15 and COLO205) with ~20-fold variation in oxaliplatin sensitivity. hCTR1 protein was expressed more abundantly than ATP7A and ATP7B proteins, but with broadly similar levels and patterns of expression across four colorectal cancer cell lines. In a colorectal cancer cell-line background (DLD-1), stable transfection of the hCtr1 gene enhanced hCTR1 protein expression and increased the sensitivity of the cells to the cytotoxicity of copper and oxaliplatin. Treatment with copper chelators (ammonium tetrathiomolybdate, bathocuproinedisulfonic acid and D-penicillamine) increased expression of hCTR1 protein in DLD-1 and SW620 cells, and potentiated the cytotoxicity of oxaliplatin in DLD-1 but not SW620 cells. Treatment with copper chloride altered neither the expression of copper transporters nor cytotoxicity of oxaliplatin in colorectal cancer lines. In conclusion, human colorectal cancer cell lines consistently express hCTR1 protein despite their variable sensitivity to oxaliplatin. Genetic or pharmacological modification of hCTR1 protein expression may potentiate oxaliplatin sensitivity in some but not all colorectal cancer cell lines.

Supramolecular Chemotherapy: Cooperative Enhancement of Antitumor Activity by Combining Controlled Release of Oxaliplatin and Consuming of Spermine by Cucurbit[7]uril.

Supramolecular chemotherapy is aimed to employ supramolecular approach for regulating the cytotoxicity and improving the efficiency of antitumor drugs. In this paper, we demonstrated a new example of supramolecular chemotherapy by utilizing the clinical antitumor drug, oxaliplatin, which is the specific drug for colorectal cancer treatment. Cytotoxicity of oxaliplatin to the colorectal normal cell could be significantly decreased by host-guest complexation between oxaliplatin and cucurbit[7]uril (CB[7]). More importantly, oxaliplatin-CB[7] exhibited cooperatively enhanced antitumor activity than oxaliplatin itself. On the one hand, the antitumor activity of oxaliplatin can reappear by competitive replacement of spermine from oxaliplatin-CB[7]; on the other hand, CB[7] can consume the overexpressed spermine in tumor environments, which is essential for tumor cell growth. These two events can lead to the cooperatively enhanced antitumor performance. Supramolecular chemotherapy can be applied to treat with spermine-overexpressed tumors. It is highly anticipated that this strategy may be employed in many other clinical antitumor drugs, which opens a new horizon of supramolecular chemotherapy for potential applications in clinical antitumor treatments.

Effects of Hypericum perforatum extract on oxaliplatin-induced neurotoxicity: in vitro evaluations.

Hypericum perforatum L. has been used for centuries as a natural remedy for the treatment of many disorders. Neuropathic pain is a common side effect of oxaliplatin-based chemotherapy and often the cause of therapy discontinuation. Thanks to its anti-inflammatory and analgesic effects, the use of H. perforatum may be a novel therapeutic strategy for neuropathy. The aim of this paper was to evaluate the effect of H. perforatum hydrophilic extract on an in vitro model of oxaliplatin-induced neurotoxicity. The antioxidant potential of extract was first evaluated in cell-free models by the thiobarbituric acid-reactive substances assay and nitro blue tetrazolium oxidation test; the ability of H. perforatum extract to reduce oxaliplatin-induced caspase-3 activity in rat astrocytes and its potential interference with the cytotoxic effects of oxaliplatin in a colorectal cancer in vitro model (HT-29 cells) were also evaluated. The extract showed a significant antioxidant effect and was able to reduce caspase-3 activity in rat astrocytes. Of note, the extract alone exerted a cytotoxic effect in HT-29 cells and did not reduce the cytotoxicity of oxaliplatin in HT-29 cells. These data suggest that H. perforatum could be used as a novel therapeutic strategy for counteracting chemotherapy-induced neuropathy.

Sufentanil attenuates oxaliplatin cytotoxicity via inhibiting connexin 43‑composed gap junction function.

Comprehensive strategies for the treatment of colorectal cancer (CRC) have become increasingly important. One of the most important factors is pain relief. Therefore, patients with CRC are concurrently treated with analgesics and chemotherapeutic agents; however, the effects of analgesics on the therapeutic activity of chemotherapeutic agents remain largely unknown. The present study investigated the effects of three widely used analgesics in clinics: Fentanyl, remifentanil and sufentanil, on the cytotoxicity of oxaliplatin, a commonly used chemotherapeutic agent for CRC. Furthermore, the underlying mechanisms of those effects in association with connexin 43 (Cx43)‑composed gap junction (GJ) function were analyzed. The Lovo, Colo320, HCT116 and HT29 human CRC cell lines, with or without Cx43 expression, were used to examine the effects of the three analgesics on the cytotoxicity of oxaliplatin. The results demonstrated that in the cell lines expressing Cx43 (Lovo and Colo320), the cytotoxicity of oxaliplatin was attenuated and Cx43 GJ function was inhibited. Sufentanil, not fentanyl or remifentanil, inhibited Cx43 GJ function effectively, and reduced the cytotoxicity of oxaliplatin. In contrast, these effects were not observed in the other two colon cancer cell lines not expressing Cx43 (HCT116 and HT29). These results suggested that alternation of Cx43 GJ function may regulate the cytotoxicity of oxaliplatin in regard to CRC. Furthermore, sufentanil, not fentanyl or remifentanil, suppressed the cytotoxicity of oxaliplatin through inhibition of Cx43 GJ function. These results may be beneficial for the treatment of CRC and reduction of treatment resistance.

Aqueous extract of Lithospermi radix attenuates oxaliplatin-induced neurotoxicity in both in vitro and in vivo models.

BackgroundOxaliplatin can induce peripheral neuropathy (OXIPN) as an adverse side effect in cancer patients. Until now, no effective preventive or therapeutic drug has been developed; therefore, the dose-limiting factor of OXIPN is still an obstacle in the use of oxaliplatin to treat cancer patients. In the present study, we report for the first time that the aqueous extract of Lithospermi radix (WLR) can attenuate the OXIPN in both in vitro and in vivo neuropathic models.MethodsThe protective effect of WLR on OXIPN was evaluated in vitro by quantifying nerve growth factor (NGF)-stimulated neurite outgrowth in PC12 cells treated with a combination of oxaliplatin and WLR. The neuroprotective potential of WLR was further confirmed by measuring the changes in nociceptive sensitivities to external mechanical stimuli in neuropathic animals induced by oxaliplatin. Histological and immunohistochemical studies were further done to examine the effect of WLR in mouse spinal cords and footpads.ResultsOxaliplatin-induced neurotoxicity in NGF-stimulated PC12 cells. It could reduce the lengths and branching numbers of neuritis in NGF-stimulated PC12 cells. Co-treatment of WLR rescued the differentiated PC12 cells from the neurotoxicity of oxaliplatin. In a chronic OXIPN animal model, administration of oxaliplatin i.p. induced enhanced nociceptive sensitivity to mechanical stimuli (25.0 to 72.5 % of response rate) along with spinal activation of microglias and astrocytes and loss of intraepidermal nerve fibers in footpads, which is remarkably suppressed by oral administration of WLR (67.5 to 35 % of response rate at the end of experiment). Cytotoxicity of oxaliplatin determined in human cancer cells was not affected irrespective of the presence of WLR.ConclusionsIn conclusion, we demonstrated that WLR can attenuate OXIPN in both in vitro and in vivo experimental models, which may be in part attributed to its anti-inflammatory activity in the spinal cord and its neuroprotective potential in the peripheral nerve system without affecting the anti-tumor potential of oxaliplatin. Therefore, WLR could be considered as a good starting material to develop a novel therapeutic agent targeting OXIPN. However, further studies should be done to elucidate the underlying mechanism such as molecular targets and active constituent(s) in WLR with neuroprotective potential.

Ursolic acid synergistically enhances the therapeutic effects of oxaliplatin in colorectal cancer

Oxaliplatin is a key drug in chemotherapy of colorectal cancer (CRC). However, its efficacy is unsatisfied due to drug resistance of cancer cells. In this study, we tested whether a natural agent, ursolic acid, was able to enhance the efficacy of oxaliplatin for CRC. Four CRC cell lines including SW480, SW620, LoVo, and RKO were used as in vitro models, and a SW620 xenograft mouse model was used in further in vivo study. We found that ursolic acid inhibited proliferation and induced apoptosis of all four cells and enhanced the cytotoxicity of oxaliplatin. This effect was associated with down-regulation of Bcl-xL, Bcl-2, survivin, activation of caspase-3, 8, 9, and inhibition of KRAS expression and BRAF, MEK1/2, ERK1/2, p-38, JNK, AKT, IKKα, IκBα, and p65 phosphorylation of the MAPK, PI3K/AKT, and NF-κB signaling pathways. The two agents also showed synergistic effects against tumor growth in vivo. In addition, ursolic acid restored liver function and body weight of the mice treated with oxaliplatin. Thus, we concluded that ursolic acid could enhance the therapeutic effects of oxaliplatin against CRC both in vitro and in vivo, which offers an effective strategy to minimize the burden of oxaliplatin-induced adverse events and provides the groundwork for a new clinical strategy to treat CRC.

Structural study on the interactions of oxaliplatin and linear DNA.

Damage to cellular DNA is believed to determine the cytotoxicity of oxaliplatin. However, high resolution structures formed by oxaliplatin and different linear DNA remain unclear. This study characterized, the key structures of different linear DNA in the platination process by UV absorption spectra and atomic force microscopy (AFM). Bathochromic shift and hyperchromicity in UV spectra after addition of oxaliplatin revealed that it can disrupt base stacking of DNA in the platination process. AFM results of different linear DNA indicated that, the platination process can induce DNA change from an extended conformation to the network structure with many kinks and finally to the compact particles, or toroids with increasing the incubation time. All AFM results confirmed that, platination of different linear DNA by oxaliplatin is a time depended process. The present AFM results provide, structural evidence about the interactions between oxaliplatin and different linear DNA containing multiple targets. SCANNING 38:880-888, 2016. © 2016 Wiley Periodicals, Inc.

Abstract A159: Dianhydrogalactitol (VAL-083) enhances activity of platinum drugs in non-small cell lung cancer

Abstract Non-small cell lung cancer (NSCLC) is treated with surgery followed by chemotherapy with either tyrosine kinase inhibitors (TKIs) or platinum-based regimens, but long term prognosis is poor. Dianhydrogalactitol (VAL-083) is a bi-functional alkylating agent with proven activity against NSCLC in preclinical and clinical studies. VAL-083 is approved for the treatment of lung cancer in the Peoples Republic of China (PRC, Approval No. Guayo Zhunzi H45021133); however, clinical use has been limited by lack of mechanistic data. Here we aimed to investigate in vitro i) the role of p53 status in VAL-083 activity, ii) VAL-083 cytotoxicity in a panel of NSCLC cell lines, iii) the combination of VAL-083 with cisplatin or oxaliplatin in NSCLC cells. We further studied the combination of VAL-083 with cisplatin in NSCLC in vivo. Dependence on p53 status was investigated in isogenic HCT-116p53-/- and HCT-116p53+/+ models. VAL-083, cisplatin and oxaliplatin cytotoxicity was tested in a panel of 9 human NSCLC cell lines: 4 wt, 4 mutant and 1 null for p53. The combination potential for VAL-083 with cisplatin or oxaliplatin was investigated in 3 human NSCLC cell lines; H460 (p53wt), A549 (p53wt) and H1975 (p53mut) by determining superadditivity and synergy using the criteria of combination index (CI)<1. Cytotoxicity was monitored on day 5 with the MTT assay. The in vivo activity of VAL-083 (2, 2.5, or 3 mg/kg i.p.) in combination with cisplatin (2 mg/kg i.v.) was tested in Rag2 mice bearing A549 xenograft tumors. Studies in HCT-116 models showed that loss of p53 increased resistance to cisplatin and oxaliplatin by 3- and 6-fold, respectively, while resistance to VAL-083 was <2-fold, suggesting a more p53-independent mechanism for VAL-083. As single agents, VAL-083, cisplatin and oxaliplatin showed good cytotoxicity in all NSCLC cell lines, with TKI-resistant cell line H460 as the most sensitive (IC50 < 0.5 uM). The combination of VAL-083 with cisplatin or oxaliplatin in H460, A549 and H1975 cells demonstrated significant super-additivity (p<0.05) and synergism (CI < 1) for both combinations in all 3 cell lines. This strongly favors non-overlapping mode of action between the platinum drugs and VAL-083 and demonstrates synergism in TKI-resistant cell lines. In the in vivo model, tumor growth delays of 11, 18 and 25 days were observed for cisplatin combined with 2, 2.5 or 3 mg/kg VAL-083, respectively, while no tumour growth delay was seen between untreated and cisplatin. The median survival time was increased by 2 days for cisplatin alone, while VAL-083 (2, 2.5 and 3 mg/kg) combined with cisplatin increased survival by 17, 17, and 14 days, respectively. In conclusion, when combined with cisplatin or oxaliplatin, VAL-083 demonstrates superadditivity/synergy against NSCLC cells, independent of their p53 status. Further, VAL-083 in combination with cisplatin significantly increased median survival in vivo. These results strongly suggest a potential for VAL-083 as part of combination treatment with platinum drugs for NSCLC, including drug-resistant phenotypes. A clinical trial is planned under the context of the existing PRC approval to investigate these observations in a clinical setting. Results, if favorable, will support expanded clinical use of VAL-083 in PRC and will serve as the basis for global development of VAL-083 as a potentially important chemotherapeutic agent in the treatment of NSCLC. Citation Format: Anne Steino, Jeffrey A. Bacha, Guanghan He, Sarath Kanekal, Nancy Dos Santos, Shun Lu, Dennis M. Brown, Zahid H. Siddik. Dianhydrogalactitol (VAL-083) enhances activity of platinum drugs in non-small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A159.

Impaired gap junctions in human hepatocellular carcinoma limit intrinsic oxaliplatin chemosensitivity: A key role of connexin 26

Hepatocellular carcinoma (HCC) is generally believed to have low sensitivity to chemotherapeutic agents including oxaliplatin (OXA). Studies have demonstrated that gap junctions (GJs) composed of connexin (Cx) proteins have the potential to modulate drug chemosensitivity in multiple tumor cells. In the present study, we investigated the characteristics of Cx and GJs in HCC at both histologic and cytologic levels, and the effects of GJ and its effective components on OXA cytotoxicity in HCC cells in vitro. Immunohistochemistry was performed in 76 HCCs and 20 normal liver tissues to detect and locate the expression of Cx26, Cx32 and Cx43. At cytologic levels, the expression and localization of Cxs were evaluated by RT-PCR, western blot and immunofluorescence assay, respectively. The GJ function between adjacent cells was detected using dye transfer assay. The role of GJs in the modulation of OXA toxicity in HCC cells was explored using pharmacologic and molecular biologic methods. We found that Cx expression in HCC tissues was significantly lower than in normal liver tissues, and the 'internalization' from cell membrane to cytoplasm was remarkable. In vitro experiments revealed the presence of functional GJs in the SMMC-7721 HCC cells due to a small amount of Cx protein along the plasma membrane at cell-cell contacts. Regulation of this part of GJs positively influenced OXA cytotoxicity. Using RNA interference, only specific inhibition of Cx26 but not Cx32 or Cx43 reduced OXA cytotoxicity. Conversely, Cx26 overexpression by transfection of Cx26 plasmid DNA enhanced OXA cytotoxicity. This study demonstrated that during hepatocarcinogenesis, the reduced expression and internalization of Cx proteins impaired the GJ function, which further attenuated OXA cytotoxicity. Impaired GJ function may contribute to low intrinsic chemosensitivity of HCC cells to OXA, mediated by Cx26.

Celecoxib antagonizes the cytotoxicity of oxaliplatin in human esophageal cancer cells by impairing the drug influx

It has been demonstrated that COX-2-selective inhibitor celecoxib shows synergy with oxaliplatin for suppressing tumor growth. However, the benefit of adding celecoxib to oxaliplatin-based regimen in human esophageal cancer is largely unknown. In the present study, we demonstrated that celecoxib antagonized oxaliplatin-induced cytotoxicity and apoptosis independent of COX-2 inhibition in human esophageal cancer cells. Celecoxib decreased cellular oxaliplatin accumulation and Pt-DNA adduction formation due to reduced drug influx. Celecoxib alone or combined with oxaliplatin substantially reduced the expression of organic cation transporter 2 (OCT2). To this end, OCT2 knockdown was sufficient to reduce oxaliplatin uptake, connecting OCT2 expression to oxaliplatin accumulation. Moreover, oxaliplatin combined with celecoxib also showed no beneficial effect when compared with monotherapy in esophageal cancer cell-xenografted nude mice. To conclude, our data provide evidence that the addition of celecoxib to oxaliplatin-containing regimens for patients with OCT2-expressing cancers should be cautious.

Inhibition of JNK Sensitizes Hypoxic Colon Cancer Cells to DNA-Damaging Agents.

We showed previously that in HT29 colon cancer cells, modulation of hypoxia-induced stress signaling affects oxaliplatin cytotoxicity. To further study the significance of hypoxia-induced signaling through JNK, we set out to investigate how modulation of kinase activities influences cellular responses of hypoxic colon cancer cells to cytotoxic drugs. In a panel of cell lines, we investigated effects of pharmacologic and molecular inhibition of JNK on sensitivity to oxaliplatin, SN-38, and 5-FU. Combination studies for the drugs and JNK inhibitor CC-401 were carried out in vitro and in vivo. Hypoxia-induced JNK activation was associated with resistance to oxaliplatin. CC-401 in combination with chemotherapy demonstrates synergism in colon cancer cell lines, although synergy is not always hypoxia specific. A more detailed analysis focused on HT29 and SW620 (responsive), and HCT116 (nonresponsive) lines. In HT29 and SW620 cells, CC-401 treatment results in greater DNA damage in the sensitive cells. In vivo, potentiation of bevacizumab, oxaliplatin, and the combination by JNK inhibition was confirmed in HT29-derived mouse xenografts, in which tumor growth delay was greater in the presence of CC-401. Finally, stable introduction of a dominant negative JNK1, but not JNK2, construct into HT29 cells rendered them more sensitive to oxaliplatin under hypoxia, suggesting differing input of JNK isoforms in cellular responses to chemotherapy. These findings demonstrate that signaling through JNK is a determinant of response to therapy in colon cancer models, and support the testing of JNK inhibition to sensitize colon tumors in the clinic.

Abstract 3873: Improving the effectiveness of chemotherapy by combining compounds that suppress drug-induced microsatellite instability

Abstract Many chemotherapeutic agents damage DNA and induce DNA damage response (DDR) signaling, resulting in growth arrest or apoptosis. DNA mismatch repair (MMR) system not only maintains genomic stability but also participates in DDR signaling. MMR deficiency leads to genetic hypermutability, manifested as microsatellite instability (MSI), and contributes to cancer pathogenesis and drug resistance. MSI has been linked to chemotherapy and therapy-related secondary cancer. Therefore, it is important to prevent drug-induced MSI to increase the effectiveness of chemotherapy while reducing cancer mortality. The purpose of this study is to characterize the MSI-inducing ability of individual chemotherapeutic agents and identify small compounds that suppress drug-induced MSI. In a human colorectal cancer cell model, all tested drugs individually induced the instability of reporter and endogenous microsatellites while reducing steady-state levels of certain MMR proteins. Relatively, oxaliplatin induced a higher MSI frequency than many tested drugs such as 5-FU. It is known that MMR-deficient tumors are resistant to 5-FU and not oxaliplatin. We then screened a commercially available library for small compounds that suppress oxaliplatin-induced MSI using a dual-fluorescent MSI reporter. We found that the majority of compounds were capable of reducing oxaliplatin-induced MSI. However, they also undesirably decreased the cytotoxicity of oxaliplatin. On the other hand, a small number of compounds such as I-6 and II-13 suppressed oxaliplatin-induced MSI with or without an improvement of drug cytotoxicity. Relative to oxaliplatin alone, co-treatment of 1 μM oxaliplatin with 6-10 μM compound II-13 decreased drug-induced MSI frequency by 45-70% without significantly affecting the cytotoxicity of oxaliplatin. Co-treatment of oxaliplatin with 4-10 μM compound I-6, however, decreased both drug-induced MSI and cell numbers by 50-78% in a dose-dependent manner. To our surprise, compounds such as II-13 suppressed MSI induced by oxaliplatin but not by 5-FU. In conclusion, individual drugs displayed different MSI-inducing abilities whereas MSI-suppressing compounds appear to be drug-specific. Further identification and validation of MSI-suppressing compounds specific for 5-FU or leucovorin, for example, would improve the effectiveness of combination chemotherapy such as FOLFOX. Citation Format: Christina L. Chang, Li-Yan Huang, Chang-Lin Wu, Jhih-Ying Chi. Improving the effectiveness of chemotherapy by combining compounds that suppress drug-induced microsatellite instability. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3873. doi:10.1158/1538-7445.AM2015-3873