Modulation of cytostatic efficacy of melphalan by glutathione: mechanisms and efficacy

Percutaneous Hepatic Perfusion (PHP) with Melphalan as a Treatment for Unresectable Metastases Confined to the Liver

Unresectable liver metastases of colorectal cancer can be treated with systemic chemotherapy, aiming to limit the disease, extend survival or turn unresectable metastases into resectable ones. Some patients however, suffer from side effects or progression under systemic treatment. For patients with metastasized uveal melanoma there are no standard systemic therapy options. For patients without extrahepatic disease, isolated liver perfusion (IHP) may enable local disease control with limited systemic side effects. Previously, this was performed during open surgery with satisfying results, but morbidity and mortality related to the open procedure, prohibited a widespread application. Therefore, percutaneous hepatic perfusion (PHP) with simultaneous chemofiltration was developed. Besides decreasing morbidity and mortality, this procedure can be repeated, hopefully leading to a higher response rate and improved survival (by local control of disease). During PHP, catheters are placed in the proper hepatic artery, to infuse the chemotherapeutic agent, and in the inferior caval vein to aspirate the chemosaturated blood returning through the hepatic veins. The caval vein catheter is a double balloon catheter that prohibits leakage into the systemic circulation. The blood returning from the hepatic veins is aspirated through the catheter fenestrations and then perfused through an extra-corporeal filtration system. After filtration, the blood is returned to the patient by a third catheter in the right internal jugular vein. During PHP a high dose of melphalan is infused into the liver, which is toxic and would lead to life threatening complications when administered systemically. Because of the significant hemodynamic instability resulting from the combination of caval vein occlusion and chemofiltration, hemodynamic monitoring and hemodynamic support is of paramount importance during this complex procedure.

Percutaneous Isolated Hepatic Perfusion for the Treatment of Unresectable Liver Malignancies

Liver malignancies are a major burden of disease worldwide. The long-term prognosis for patients with unresectable tumors remains poor, despite advances in systemic chemotherapy, targeted agents, and minimally invasive therapies such as ablation, chemoembolization, and radioembolization. Thus, the demand for new and better treatments for malignant liver tumors remains high. Surgical isolated hepatic perfusion (IHP) has been shown to be effective in patients with various hepatic malignancies, but is complex, associated with high complication rates and not repeatable. Percutaneous isolated liver perfusion (PHP) is a novel minimally invasive, repeatable, and safer alternative to IHP. PHP is rapidly gaining interest and the number of procedures performed in Europe now exceeds 200. This review discusses the indications, technique and patient management of PHP and provides an overview of the available data.

Enhancement of melphalan activity by buthionine sulfoximine and electroporation in melanoma cells

Melphalan represents the reference drug for locoregional chemotherapy of melanoma; nevertheless, treatment failure may occur because of resistance to chemotherapy. Refractory melanoma cells show either an increased capability of drug inactivation, which is known to be associated with elevated intracellular levels of glutathione (GSH), or a decreased melphalan uptake. The aim of this study was to explore a biochemical and a biophysical strategy, and their combination, to overcome melphalan resistance in melanoma cells. The biochemical strategy was based on the treatment of melanoma cells with DL-buthionine (S,R)-sulfoximine (BSO) to deplete the GSH levels, thus reducing melphalan inactivation. In the biophysical strategy, cell membrane electroporation was used to increase melphalan uptake. The SK-MEL 28-resistant human melanoma cell line was pretreated with 50 μmol/l BSO for 24 h and then treated with increasing melphalan doses, with or without electroporation. Spectrophotometric quantification of cell viability was used to determine melphalan cytotoxicity. Intracellular total GSH was measured using a kinetic enzymatic assay. BSO induced 3.50-fold GSH depletion in untreated cells and a similar reduction was also maintained in melphalan-treated cells. BSO pretreatment produced a 2.46-fold increase in melphalan cytotoxicity. Electroporation increased melphalan cytotoxicity 1.42-fold. The combination of both BSO pretreatment with melphalan plus electroporation led to a 4.40-fold increase in melphalan cytotoxicity compared with melphalan alone. Pretreatment with BSO and cell membrane permeabilization by electroporation enhanced the cytotoxic activity of melphalan in melanoma cells. Their rational combination deserves further investigation and may improve the efficacy of locoregional chemotherapy of melanoma.

Modulation of cell metabolic pathways and oxidative stress signaling contribute to acquired melphalan resistance in multiple myeloma cells

Alkylating agents are widely used chemotherapeutics in the treatment of many cancers, including leukemia, lymphoma, multiple myeloma, sarcoma, lung, breast and ovarian cancer. Melphalan is the most commonly used chemotherapeutic agent against multiple myeloma. However, despite a 70-80% initial response rate, virtually all patients eventually relapse due to the emergence of drug-resistant tumour cells. By using global proteomic and transcriptomic profiling on melphalan sensitive and resistant RPMI8226 cell lines followed by functional assays, we discovered changes in cellular processes and pathways not previously associated with melphalan resistance in multiple myeloma cells, including a metabolic switch conforming to the Warburg effect (aerobic glycolysis), and an elevated oxidative stress response mediated by VEGF/IL8-signaling. In addition, up-regulated aldo-keto reductase levels of the AKR1C family involved in prostaglandin synthesis contribute to the resistant phenotype. Finally, selected metabolic and oxidative stress response enzymes were targeted by inhibitors, several of which displayed a selective cytotoxicity against the melphalan-resistant cells and should be further explored to elucidate their potential to overcome melphalan resistance.

Oxidative stress induced in rat liver by anticancer drugs doxorubicin, paclitaxel and docetaxel

PURPOSE

Oxidative stress generated by anticancer drugs in non-targeted tissues, is considered as a significant factor responsible for their severe side effects, e.g. cardiotoxicity, neurotoxicity and hepatotoxicity. Lack of data on the effect of concurrent administration of commonly used anticancer drugs: doxorubicin (DOX), paclitaxel (PTX) and docetaxel (DTX) on normal tissue, prompted us to examine the markers of oxidative stress in the liver of rats treated with these drugs.

MATERIAL/METHODS

Male Wistar rats of average weight 200 g were injected intraperitoneally (i.p.) with 10 mg/kg of body weight (b.w.) of DOX, PTX and DTX. The drugs were given alone or in combinations DOX+taxane. The activities of superoxide dismutase (SOD), catalase (CAT), low molecular weight and total thiols and thiobarbituric acid-reactive substances (TBARS) were estimated.

RESULTS

Combination of two drugs generated greater changes than single agents. Concurrent administration of DOX and PTX increased SOD activity and TBARS, decreased the amount of low molecular weight and total thiols, but did not cause any changes in the activity of catalase. Combination of DOX and DTX induced similar changes except for the activity of catalase, which decreased after the treatment. Of the three drugs only DTX significantly decreased the activity of SOD. However, both taxanes increased the activity of catalase. Although a decrease in concentration of -SH groups, depletion of glutathione and an increase of TBARS were observed after treatment with single drugs, the changes were not statistically significant.

CONCLUSION

Concurrent administration of DOX and taxane induced enhanced oxidative stress in comparison to single drugs, which suggests their synergistic prooxidant mode of action in liver.

Recent trends and future perspectives in isolated hepatic perfusion in the treatment of liver tumors

Isolated hepatic perfusion (IHP) involves a method of complete vascular isolation of the liver to enable treatment of liver tumors with high drug doses without systemic toxicity. Recent clinical studies have mainly employed IHP with melphalan with or without tumor necrosis factor-alpha and mild hyperthermia. The results of these studies demonstrate that high response and survival rates can be achieved with IHP. The current status, recent developments and future perspectives of IHP are discussed in this review.

An inverse switch in DNA base excision and strand break repair contributes to melphalan resistance in multiple myeloma cells

Alterations in checkpoint and DNA repair pathways may provide adaptive mechanisms contributing to acquired drug resistance. Here, we investigated the levels of proteins mediating DNA damage signaling and -repair in RPMI8226 multiple myeloma cells and its Melphalan-resistant derivative 8226-LR5. We observed markedly reduced steady-state levels of DNA glycosylases UNG2, NEIL1 and MPG in the resistant cells and cross-resistance to agents inducing their respective DNA base lesions. Conversely, repair of alkali-labile sites was apparently enhanced in the resistant cells, as substantiated by alkaline comet assay, autoribosylation of PARP-1, and increased sensitivity to PARP-1 inhibition by 4-AN or KU58684. Reduced base-excision and enhanced single-strand break repair would both contribute to the observed reduction in genomic alkali-labile sites, which could jeopardize productive processing of the more cytotoxic Melphalan-induced interstrand DNA crosslinks (ICLs). Furthermore, we found a marked upregulation of proteins in the non-homologous end-joining (NHEJ) pathway of double-strand break (DSB) repair, likely contributing to the observed increase in DSB repair kinetics in the resistant cells. Finally, we observed apparent upregulation of ATR-signaling and downregulation of ATM-signaling in the resistant cells. This was accompanied by markedly increased sensitivity towards Melphalan in the presence of ATR-, DNA-PK, or CHK1/2 inhibitors whereas no sensitizing effect was observed subsequent to ATM inhibition, suggesting that replication blocking lesions are primary triggers of the DNA damage response in the Melphalan resistant cells. In conclusion, Melphalan resistance is apparently contributed by modulation of the DNA damage response at multiple levels, including downregulation of specific repair pathways to avoid repair intermediates that could impair efficient processing of cytotoxic ICLs and ICL-induced DSBs. This study has revealed several novel candidate biomarkers for Melphalan sensitivity that will be included in targeted quantitation studies in larger patient cohorts to validate their value in prognosis as well as targets for replacement- or adjuvant therapies.

Structure-activity relationships and mechanism of action of antitumor bis 8-hydroxyquinoline substituted benzylamines

A series of twenty six 8-hydroxyquinoline substituted amines, structurally related to compounds 2 and 3, were synthesized to evaluate the effects of structural changes on antitumor activity and understand their mechanism of action. The studies were performed on a wide variety of cancer cell lines within glioma and carcinoma models. The results obtained from chemical models and biological techniques such as microarrays suggest the following hypothesis that a quinone methide intermediate which does not react with DNA but which gives covalent protein thiol adducts. Micro-array analysis showed that the drugs induce the expression of a variety of stress related genes responsible for the cytotoxic and cytostatic effects in carcinoma and glioblastoma cells respectively. The described analogues could represent new promising anti-cancer candidates with specific action mechanisms, targeting accessible thiols from specific proteins and inducing potent anti-cancer effects.

Drug selection in isolated hepatic perfusion for nonresectable liver tumors: recent trends and perspectives

Isolated hepatic perfusion (IHP) involves a method of complete vascular isolation of the liver to take the advantage of directed intensive chemotherapy that has minimal systemic toxicity. Recent clinical studies mainly employed melphalan with or without tumor necrosis factor alpha (TNF-α), or with hyperthermia in IHP. The results of these studies showed that higher response rates and survival rates could be achieved by IHP than by traditional therapeutics for non-resectable liver tumors. In this article, we discussed the current status, recent developments and future perspectives of drug selection in IHP.

Population pharmacokinetics of melphalan and glutathione S-transferase polymorphisms in relation to side effects

Melphalan is associated with severe side effects such as mucositis, diarrhea, and myelosuppression. We investigated how much the individual severity of these side effects is predicted by pharmacokinetics. In addition, we studied glutathione S-transferase GSTM1, GSTT1, and GSTP1 polymorphisms in relation to adverse events. A high interindividual pharmacokinetic variability was observed in 84 patients. There was a linear correlation between creatinine and melphalan clearance (P=0.0004). Patients treated with a dose > or = 70 mg/m(2) had a 23-fold increased risk to develop mucositis (P<0.001) and a 12-fold increased risk to develop diarrhea (P<0.001) compared with lower doses. The GSTP1 codon 105 polymorphism may be relevant for development of mucositis and the GSTT1 deletion may predict diarrhea, but these findings require confirmation. Melphalan-induced side effects were significantly dependent only on dose. Therapeutic drug monitoring or genotyping for GST does not appear to be very helpful in optimizing therapy with melphalan.

Involvement of NF-κB and glutathione in cytotoxic effects of nitric oxide and taxol on human leukemia cells

Nitric oxide (NO) has been shown to be cytotoxic for normal and transformed cell lines. One of the intracellular targets for NO action is glutathione (GSH). GSH determinates cellular redox potential and modulates several biological events. During oxidative and nitrosative stress, glutathione system imbalance is associated with the upregulation of gamma-glutamylcysteine synthetase (gamma-GCS) expression, which is mediated by nuclear factor kappaB (NF-kappaB). Our previous studies demonstrated a cytotoxic effect of NO and taxol on human lymphoblastic leukemia cells triggered by inhibition of NF-kappaB activity. In this study, we have demonstrated the involvement of GSH in taxol- and NO-induced cytotoxic effects on human CEM leukemia cells. NO- and taxol-induced a depletion of GSH levels in CEM cells, which was potentialized by l-buthionine-S,R-sulfoximine (BSO), an inhibitor of gamma-GCS. BSO induced an increase in nuclear translocation of NF-kappaB. However, when cells were treated with NO or taxol in association with BSO, these compounds inhibited the constitutive activity of NF-kappaB. These results suggest that oxidative and nitrosative damage in lymphoblastic leukemia cells shall be mediated by NO- and taxol-induced GSH depletion as a consequence of preventing GSH synthesis.

L-type amino acid transporter-1 overexpression and melphalan sensitivity in Barrett's adenocarcinoma

The L-type amino acid transporter-1 (LAT-1) has been associated with tumor growth. Using cDNA microarrays, overexpression of LAT-1 was found in 87.5% (7/8) of esophageal adenocarcinomas relative to 12 Barrett's samples (33% metaplasia and 66% dysplasia) and was confirmed in 100% (28/28) of Barrett's adenocarcinomas by quantitative reverse transcription polymerase chain reaction. Immunohistochemistry revealed LAT-1 staining in 37.5% (24/64) of esophageal adenocarcinomas on tissue microarray. LAT-1 also transports the amino acid-related chemotherapeutic agent, melphalan. Two esophageal adenocarcinoma and one esophageal squamous cell line, expressing LAT-1 on Western blot analysis, were sensitive to therapeutic doses of melphalan (P <.001). Simultaneous treatment with the competitive inhibitor, BCH [2-aminobicyclo-(2,1,1)-heptane-2-carboxylic acid], decreased sensitivity to melphalan (P <.05). In addition, confluent esophageal squamous cultures were less sensitive to melphalan (P <.001) and had a decrease in LAT-1 protein expression. Tumors from two esophageal adenocarcinoma cell lines grown in nude mice retained LAT-1 mRNA expression. These results demonstrate that LAT-1 is highly expressed in a subset of esophageal adenocarcinomas and that Barrett's adenocarcinoma cell lines expressing LAT-1 are sensitive to melphalan. LAT-1 expression is also retained in cell lines grown in nude mice providing a model to evaluate melphalan as a chemotherapeutic agent against esophageal adenocarcinomas expressing LAT-1.

Isolated hepatic perfusion for the treatment of colorectal metastases confined to the liver: recent trends and perspectives

Isolated hepatic perfusion (IHP) involves a method of complete vascular isolation of the liver to allow treatment of liver tumours with toxic systemic doses. The recent clinical studies mainly employed IHP with melphalan with or without tumour necrosis factor-alpha (TNF-alpha) and mild hyperthermia. The results of these studies show that high response rates and high survival rates can be achieved by IHP. In this article, the current status, recent developments and future perspectives of IHP are discussed.

Immunohistochemical detection of melphalan–DNA adducts in colon cancer cells in vitro and human colorectal liver tumours in vivo

Melphalan is a chemotherapeutic drug that exerts its cytotoxic effect mainly through the formation of DNA adducts. We report the specific immunohistochemical detection and visualisation of melphalan-DNA adducts using the monoclonal antibody MP5/73 in cultured tumour cells and solid tumour tissue from colorectal liver metastases from patients treated with melphalan. The human colon cancer cell lines HT29, SW480 and SW1116, and the rat colon cancer cell line CC531 were exposed to different concentrations of melphalan. In addition, tumour samples from 17 patients with colorectal liver metastases treated by isolated hepatic perfusion with high dose melphalan (200mg) were collected. Cell lines and tumour samples were stained with the MP5/73 antibody against melphalan-DNA adducts and cell viability was determined by an MTT assay. Melphalan-DNA adducts could be visualised by immunohistochemistry in both cultured cells and solid tumour tissue. A correlation between melphalan exposure concentration, the subsequent melphalan-DNA adduct staining intensity, and melphalan cytotoxicity existed for each individual cell line, but the level of both parameters independently differed between cell lines. Specific staining for melphalan-DNA adducts also was feasible in the human solid tumour tissue. There was considerable variation in melphalan-DNA adduct staining, staining intensity, and distribution in the tumour stroma and the tumour epithelium among the different patients. Melphalan-DNA adducts appeared to be more intense in tumour cells at the border of the tumour nodules than in tumour cells in the centre. Thus, visualisation of melphalan-DNA adducts by immunohistochemistry allows the study of distribution of melphalan-DNA adducts in solid tumours.

Covalent binding to glutathione of the DNA-alkylating antitumor agent, S23906-1

The benzoacronycine derivative, S23906-1, was characterized recently as a novel potent antitumor agent through alkylation of the N2 position of guanines in DNA. We show here that its reactivity towards DNA can be modulated by glutathione (GSH). The formation of covalent adducts between GSH and S23906-1 was evidenced by EI-MS, and the use of different GSH derivatives, amino acids and dipeptides revealed that the cysteine thiol group is absolutely required for complex formation because glutathione disulfide (GSSG) and other S-blocked derivatives failed to react covalently with S23906-1. Gel shift assays and fluorescence measurements indicated that the binding of S23906-1 to DNA and to GSH are mutually exclusive. Binding of S23906-1 to an excess of GSH prevents DNA alkylation. Additional EI-MS measurements performed with the mixed diester, S28053-1, showed that the acetate leaving group at the C1 position is the main reactive site in the drug: a reaction scheme common to GSH and guanines is presented. At the cellular level, the presence of GSH slightly reduces the cytotoxic potential of S23906-1 towards KB-3-1 epidermoid carcinoma cells. The GSH-induced threefold reduction of the cytotoxicity of S23906-1 is attributed to the reduced formation of lethal drug-DNA covalent complexes in cells. Treatment of the cells with buthionine sulfoximine, an inhibitor of GSH biosynthesis, facilitates the formation of drug-DNA adducts and promotes the cytotoxic activity. This study identifies GSH as a reactant for the antitumor drug, S23906-1, and illustrates a pathway by which GSH may modulate the cellular sensitivity to this DNA alkylating agent. The results presented here, using GSH as a biological nucleophile, fully support our initial hypothesis that DNA alkylation is the major mechanism of action of the promising anticancer drug S23906-1.

Melphalan antitumor efficacy and hepatotoxicity: the effect of variable infusion duration in the hepatic artery

The optimum conditions (duration and concentration) of a fixed dose, intra-arterial melphalan infusion in relation to its antitumor effect and toxicity in the liver were investigated in a rat colon tumor model (CC531) of liver metastases. We studied the difference in tumor and liver uptake, as well as antitumor effect and hepatotoxicity after 5- and 20-min hepatic arterial infusion (HAI) of a fixed melphalan dose. Melphalan content in perfusate, liver, and tumor tissue was analyzed by high-performance liquid chromatography. The antitumor effect and hepatotoxicity in rats treated either systemically or with 5- and 20-min HAI, with a fixed dose melphalan (4.4 micromol), were assessed 2 weeks after treatment. No difference in melphalan content of tumor/liver tissue or antitumor effect was observed between rats treated with 5- and 20-min HAI. Hepatotoxicity was strongly affected by perfusion duration/concentration, however. Rats treated with 5-min HAI weighed significantly less, and liver toxicity parameters were significantly increased compared with those of all other groups; eight of nine rats showed severe cholangiofibrosis. Body weights and liver toxicity parameters of the rats treated with 20-min HAI were not statistically different from the control group. In conclusion, duration of HAI with 4.4 micromol of fixed dose melphalan did not affect tumor uptake and antitumor effect, but the resulting increase in melphalan concentration had major impact on hepatobiliary toxicity. Therefore, in a clinical setting, caution should be taken when infusion duration and concentration of melphalan are changed.