Promising cytotoxic activity profile of fermented wheat germ extract (Avemar®) in human cancer cell lines

Abstract

Fermented wheat germ extract (FWGE) is currently used as nutrition supplement for cancer patients. Limited recent data suggest antiproliferative, antimetastatic and immunological effects which were at least in part exerted by two quinones, 2-methoxy benzoquinone and 2,6-dimethoxybenzquinone as ingredients of FWGE. These activity data prompted us to further evaluate the in vitro antiproliferative activity of FWGE alone or in combination with the commonly used cytotoxic drugs 5-FU, oxaliplatin or irinotecan in a broad spectrum of human tumor cell lines. We used the sulforhodamine B assay to determine dose response relationships and IC50-values were calculated using the Hill equation. Drug interaction of simultaneous and sequential drug exposure was estimated using the model of Drewinko and potential clinical activity was assessed by the model of relative antitumor activity (RAA). Apoptosis was detected by DNA gel electrophoresis.FWGE induced apoptosis and exerted significant antitumor activity in a broad spectrum of 32 human cancer cell lines. The highest activity was found in neuroblastoma cell lines with an average IC50 of 0.042 mg/ml. Furthermore, IC50-range was very narrow ranging from 0.3 mg/ml to 0.54 mg/ml in 8 colon cancer cell lines. At combination experiments in colon cancer cell lines when FWGE was simultaneously applied with either 5-FU, oxaliplatin or irinotecan we observed additive to synergistic drug interaction, particularly for 5-FU. At sequential drug exposure with 5-FU and FWGE the observed synergism was abolished.Taken together, FWGE exerts significant antitumor activity in our tumor model. Simultaneous drug exposure with FWGE and 5-FU, oxaliplatin or irinotecan yielded in additive to synergistic drug interaction. However, sequential drug exposure of 5-FU and FWGE in colon cancer cell lines appeared to be schedule-dependent (5-FU may precede FWGE).Further evaluation of FWGE as a candidate for clinical combination drug regimens appeared to be warranted.

Figure 1

Illustration of IC₅₀ of FWGE as a mean graph. IC₅₀ of at least 3 independent experiments per cell line were averaged and summarized as a mean graph for better comparison of the different activity. The average IC₅₀ is 0.33 mg/ml. The highest activity of FWGE was found on neuroblastoma and ovarian cancer cell lines. It's interesting to note that the IC₅₀-values of the 8 human CRC cell lines included in this screen range close to the average IC₅₀.

Figure 2

Induction of apoptosis by FWGE. A representative panel of human tumor cell lines was treated with an IC₉₀ of FWGE for 48 h and floating cells were harvested by centrifugation for DNA extraction. DNA was seperated by DNA gel electrophoresis and stained with ethidium bromide subsequently. Typical DNA laddering indicative for apoptosis was visualized by UV light illumination.

Figure 3

Synergy between FWGE and 5-FU in human colon cancer cell line HCT15. Plots represent the average of 3 independent experiments. The hypothetical curve was calculated as described by Drewinko et al. [16]. Synergy is indicated by the hypothetical curve which runs above the combination curve.