Recognition of different antigens of mistletoe extracts by anti-mistletoe lectin antibodies

NCCAM/NCI Phase 1 Study of Mistletoe Extract and Gemcitabine in Patients with Advanced Solid Tumors

PURPOSE

European Mistletoe (Viscum album L.) extracts (mistletoe) are commonly used for cancer treatment in Europe. This phase I study of gemcitabine (GEM) and mistletoe in advanced solid cancers (ASC) evaluated: (1) safety, toxicity, and maximum tolerated dose (MTD), (2) absolute neutrophil count (ANC) recovery, (3) formation of mistletoe lectin antibodies (ML ab), (4) cytokine plasma concentrations, (5) clinical response, and (6) pharmacokinetics of GEM.

METHODS

DESIGN

increasing mistletoe and fixed GEM dose in stage I and increasing doses of GEM with a fixed dose of mistletoe in stage II. Dose limiting toxicities (DLT) were grade (G) 3 nonhematologic and G4 hematologic events related to platelets and granulocytes only [corrected]; MTD was reached with 2 DLTs in one dosage level. Response in stage IV ASC was assessed with descriptive statistics. Statistical analyses examined clinical response/survival and ANC recovery.

RESULTS

DLTs were G4 neutropenia, G4 thrombocytopenia, G4 acute renal failure, and G3 cellulitis, attributed to mistletoe. GEM 1300 mg/m(2) [corrected] and mistletoe 250 mg combined were the MTD. Of 44 patients, 24 developed nonneutropenic fever and flu-like syndrome. GEM pharmacokinetics were unaffected by mistletoe. All patients developed ML3 IgG antibodies. ANC showed a trend to increase between baseline and cycle 2 in stage I dose escalation. 6% of patients showed partial response, 42% stable disease. Median survival was 200 days. Compliance with mistletoe injections was high.

CONCLUSION

GEM plus mistletoe is well tolerated. No botanical/drug interactions were observed. Clinical response is similar to GEM alone.

Mistletoe and gemcitabine in patients with advanced cancer: a model for the phase I study of botanicals and botanical-drug interactions in cancer therapy

Plant extracts of the European mistletoe (MTE), Viscum album, the most widely used cancer treatment in Germany, have been used in European countries as sole intervention or as adjunct to conventional cancer therapies for more than 80 years. Preclinical data suggest immunostimulatory and cytotoxic effects of MTE. While the clinical efficacy of MTE in cancer is being investigated, toxicity and potential interactions of MTE with standard chemotherapeutic agents are unknown. Gemcitabine is an approved antimetabolite chemotherapeutic agent effective as single agent in patients with solid tumors (ST). The documented metabolism and pharmacokinetics of gemcitabine make this agent well suited for the study of botanical-chemotherapy drug interactions (BDIA) in cancer. Based on reports of altered drug metabolism associated with botanical preparations, research into BDIA has intensified. The phase I, 2-stage, dose-escalation study outlined here will test MTE with gemcitabine as a paradigm for the phase I investigation of botanical-drug combination treatments in patients with advanced ST. The protocol including the following components has been reviewed and approved by the National Cancer Institute Institutional Review Board (IRB), the National Naval Medical Center IRB, and the Navy Clinical Investigation Program (study 02-074): (1) use of a standardized MTE, approved by the Food and Drug Administration for investigational use; (2) independent verification of key MTE components considered biologically active; (3) identification of contaminants and adulterants; (4) pharmacokinetics of gemcitabine and its principal metabolites before and upon exposure to MTE; (5) safety and toxicity data collection; (6) assays of plasma ML antibody production in vivo; and (7) pharmacodynamic studies of the botanical-drug combination.

Synergism between rViscumin and cisplatin is not dependent on ERCC-1 expression

Interactions between recombinant mistletoe lectin (rViscumin) and anticancer drugs were investigated in vitro. rViscumin enhanced the cytotoxic effects of vincristine, mafosfamide, idarubicin and cisplatin in the human leukemia cell lines K562 and KG1a. In human marrow progenitor cells, rViscumin inhibited colony formation and did not exert any protective activity against cisplatin-induced inhibition of clonogenicity. Quantitative real-time reverse transcription polymerase chain reaction analysis revealed that cisplatin treatment of K562 cells resulted in a 1.9-fold increase in mRNA expression of the nucleotide excision repair gene ERCC-1. This upregulation was not prevented when cells were post-incubated with rViscumin. Our study provides evidence that rViscumin is capable of enhancing cytotoxicity of anticancer agents in vitro. This synergism appears to be independent of transcriptional activity of DNA repair relevant genes.

Mistletoe and cancer: controversies and perspectives

Extracts and preparations from the tree parasitic plant mistletoe (Viscum album L.) have been used in the treatment of cancer for decades. Numerous preclinical and in vitro studies have reported immunostimulatory, cytotoxic, and proapoptotic effects. Translation of these effects into clinical response continues to pose a problem. While a number of clinical studies have found improvement in quality of life (QOL), data on the efficacy of mistletoe to prolong survival are conflicting and of variable quality. Clinical trial data regarding the toxicity and pharmacokinetics of mistletoe components with known in vitro or preclinical activity are lacking. Mistletoe is a widely used form of complementary and alternative medicine (CAM) for cancer treatment, and research into its use poses the challenges of translation of preclinical data into demonstrable clinical efficacy and investigating CAM approaches as a component of complex cancer treatment systems.