br Table br IC concentrations g ml of the Iscucin
IC50 concentrations (μg/ml) of the Iscucin® preparations compared to Actinomycin-D from diﬀerent cancer cell lines.
ML-1 contents (ng/ml) at the IC50 concentrations of the Iscucin® preparations.
lung cancer cervix cancer glioma renal cell cancer colorectal cancer
Fig. 1. IC50 concentrations (ng/ml) of ML-1 and ricin at diﬀerent human cancer cell lines.
In order to investigate common perception that ML-1 is the most active substance in mistletoes and responsible for cell growth inhibition (Büssing and Schnietzel, 1999; Elluru et al., 2006; Heidecke and Meyer, 2005; van Huyen et al., 2002), isolated ML-1 was tested. As result, ML-1 showed a concentration dependent eﬀect: IC50 levels ranged from 1 to 56 ng/ml depending on the respective cell line (Fig. 1). Büssing et al. (2004) reported an inhibition of tumor cell growth by 5 ng/ml ML. In a previous investigation with a panel of 26 human tumor cell lines, IC50 values of 1 – 70 ng/ml were found (Kelter and Fiebig, 2006). These values correspond to the results in the present study. In contrast to the Iscucin® plant preparations, Caki-2 had only a low sensitivity towards ML-1.
IC50 concentrations of ricin ranged from 29 to 191 ng/ml (Fig. 1). Thus, ML-1 was much more eﬀective than ricin in the cell lines in-vestigated. These results diﬀer from previous reports of the leukemia T-cell line Molt-4, on which ricin was 16 times more cytotoxic than on ML (Doser et al., 1989). Franz et al. (1986 b) and Creppy et al. (1981) reported that toxic damage of healthy liver HA-1077 occurred at ML or ricin concentrations of 10,000 ng/ml.
In comparison with the reference substance Actinomycin-D, ML-1 was also more eﬀective. Beztsinna et al. (2018) showed that ML was more eﬀective in multidrug resistant mammacarcinoma cell line in contrast to commonly used chemotherapeutic drugs.
The eﬀectiveness of mistletoe preparations to inhibit the cell growth correlates mostly with the content of ML (Büssing and Schnietzel, 1999; Elluru et al., 2006; Heidecke and Meyer, 2005; van Huyen et al., 2002). To figure out whether the IC50 concentrations of the Iscucin®
DLD-1, colorectal cancer
Caki-2, renal cell cancer
HeLa, cervix cancer
Iscucin® Pini Iscucin® Abietis Iscucin® Mali Iscucin® Populi Iscucin® Crataegi Iscucin® Tiliae Iscucin® Salicis
Fig. 2. IC50 concentrations of Iscucin® preparations and their contents of ML-1 (ELISA) and VT-A (HPLC-UV).
The preparations have diﬀerent contents of ML and VT. Iscucin® Salicis and Tiliae have high, Crataegi, Populi and Mali middle and Abietis and Pini low content of ML-1. The contents of ML-1 range from 928 to 17,006 ng/ml. The highest value of VT was measured in Iscucin® Crataegi by HPLC-UV. The range of VT in the Iscucin® preparation was – 49 μg/ml.
The IC50 concentrations of the Iscucin® preparations correlate with their ML-1 content. In general very strong antiproliferative eﬀects were found with Iscucin® Salicis and Tiliae treatment. Strong eﬀects were seen with Iscucin® Crataegi, Mali and Populi. Iscucin® Abietis and Iscucin® Pini showed considerably weaker eﬀects.
HeLa, cervix cancer
Caki-2, renal cell cancer
DLD-1, colorectal cancer F SK-N-SH, neuroblastoma
Fig. 3. IC50 dilution factors of three concentrations of ML-1 and the Iscucin® preparations in comparison. Graphs show the classification of the Iscucin® preparations and the investigated ML-1 concentrations to three ML-1 content sectors: 1) Salicis, Tiliae, ML-1 20,000 ng/ml (high ML-1 content);
The comparison in the three diﬀerent sectors shows that the mistletoe preparations are much more potent than ML-1, especially at Caki-2 (C), followed by HCC827 (A) and LN229 (D).
Fig. 4. Eﬀect of VT-A 48.4 μg/ml and purothionin 48.4 μg/ml on lung cancer cell line HCC827. VT-A (A) and purothionin (B) in the highest tested concentration of 48.4 μg/ml had no eﬀect on the cell viability of the most sensitive tumor cell line (HCC827, lung cancer) in this investigation.
preparations correlate with their ML-1 content, the latter were mea-sured and are shown in Fig. 2. The contents of ML-1 in the Iscucin® preparations ranged from 928 to 17,006 ng/ml Iscucin® Salicis and Tiliae having the highest and Iscucin® Pini the lowest value. Determining the ML-1 contents at the IC50 concentrations, it became obvious that they were nearly the same in the Iscucin® preparation from all host trees, which suggests that the ML-1 is responsible for the antiproliferative
eﬀect on the human tumor cells (Table 3). It is remarkable that the ML-1 content of the IC50 concentration of Iscucin® Pini was lower than those of the other extracts. However, only Iscucin® Pini contains 5,7-di-methoxy-4′-hydroxyflavanone and three quercetin derivates as phenolic compounds (Gärtner et al., 2015, 2016). Quercetin and 5,7-dimethoxy-4′-hydroxyflavanone have antioxidant and also antitumoral properties (Fantini et al., 2015; Jeong et al., 2008; Kiekow et al., 2016; Klappan,