Inhibition of Glutamine Cellular Uptake Contributes to the Cytotoxic Effect of Xanthohumol in Triple-Negative Breast Cancer Cells

Abstract

Breast cancer constitutes the most incident cancer and one of the most common causes of cancer-related death. “Glutamine addiction”, an important metabolic feature of cancer cells, is dependent on supply of this amino acid from external sources. In this study, the effect of several polyphenols (catechin, epicatechin, EGCG, catechin:lysine, naringenin, hesperidin, malvidin, delphinidin, kaempferol, quercetin, rutin, myricetin, resveratrol, xanthohumol, and chrysin) upon glutamine (³H-GLN) uptake by human breast epithelial adenocarcinoma cell lines with distinct characteristics (MCF-7 and MDA-MB-231) was assessed.

Several polyphenols interfere with ³H-GLN uptake by both cell lines. Xanthohumol markedly decreases total and Na⁺-dependent ³H-GLN uptake and showed a cytotoxic and anti-proliferative effect in MDA-MB-231 cells. Xanthohumol is as an uncompetitive inhibitor of Na⁺-dependent ³H-GLN uptake and inhibits GPNA (L-γ-glutamyl-p-nitroanilide)-sensitive, both ASCT2 (alanine, serine, cysteine transporter 2)-mediated and non-ASCT2-mediated ³H-GLN uptake. Xanthohumol does not interfere with the transcription rates of ASCT2. The cytotoxic effect of xanthohumol, but not its anti-proliferative effect, is GPNA-sensitive and related to ASCT2 inhibition. Combination of xanthohumol with the breast cancer chemotherapeutic agent doxorubicin results in an additive anti-proliferative, but not cytotoxic effect.

We conclude that targeting glutamine uptake might constitute a potential interesting strategy for triple-negative breast cancer.

Acknowledgments

We thank Dr. J. Stephenne (BePharBel Manufacturing, Courcelles, Belgium) for providing Cat:Lys. We also thank Carlos Reguenga (FMUP; Departamento de Biomedicina – Unidade de Biologia Experimental, Faculdade de Medicina Universidade do Porto, Porto, Portugal) for the help with the siRNA transfection procedures.

Credit Authorship Contribution Statement

Francisca Carmo: Investigation, Writing – original draft. Cláudia Silva: Investigation. Fátima Martel: Conceptualization, Formal analysis, Supervision, Visualization, Writing - review & editing.

Data Available on Request from the Authors

The data that support the findings of this study are available from the corresponding author, F. Martel, upon reasonable request.

Disclosure Statement

The authors report no conflict of interest.

Additional information

Funding

This work was supported by Fundação para a Ciência e a Tecnologia (UID/BIM/04293/2013).