PLoS ONE: Breast Cancer Stem-Like Cells Are Inhibited by a Non-Toxic Aryl Hydrocarbon Receptor Agonist

Breast Cancer Stem-Like Cells Are Inhibited by a Non-Toxic Aryl Hydrocarbon Receptor Agonist

Cancer stem cells (CSCs) have increased resistance to cancer chemotherapy. They can be enriched as drug-surviving CSCs (D-CSCs) by growth with chemotherapeutic drugs, and/or by sorting of cells expressing CSC markers such as aldehyde dehydrogenase-1 (ALDH). CSCs form colonies in agar, mammospheres in low-adherence cultures, and tumors following xenotransplantation in Scid mice. We hypothesized that tranilast, a non-toxic orally active drug with anti-cancer activities, would inhibit breast CSCs.

We examined breast cancer cell lines or D-CSCs generated by growth of these cells with mitoxantrone. Tranilast inhibited colony formation, mammosphere formation and stem cell marker expression. Mitoxantrone-selected cells were enriched for CSCs expressing stem cell markers ALDH, c-kit, Oct-4, and ABCG2, and efficient at forming mammospheres. Tranilast markedly inhibited mammosphere formation by D-CSCs and dissociated formed mammospheres, at pharmacologically relevant concentrations. It was effective against D-CSCs of both HER-2+ and triple-negative cell lines. Tranilast was also effective in vivo, since it prevented lung metastasis in mice injected i.v. with triple-negative (MDA-MB-231) mitoxantrone-selected cells. The molecular targets of tranilast in cancer have been unknown, but here we demonstrate it is an aryl hydrocarbon receptor (AHR) agonist and this plays a key role. AHR is a transcription factor activated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polycyclic aromatic hydrocarbons and other ligands. Tranilast induced translocation of the AHR to the nucleus and stimulated CYP1A1 expression (a marker of AHR activation). It inhibited binding of the AHR to CDK4, which has been linked to cell-cycle arrest. D-CSCs expressed higher levels of the AHR than other cells. Knockdown of the AHR with siRNA, or blockade with an AHR antagonist, entirely abrogated the anti-proliferative and anti-mammosphere activity of tranilast. Thus, the anti-cancer effects of tranilast are AHR dependent.

We show that tranilast is an AHR agonist with inhibitory effects on breast CSCs. It is effective against CSCs of triple-negative breast cancer cells selected for anti-cancer drug resistance. These results suggest it might find applications in the treatment of breast cancer.



Gérald J. Prud'homme1,2*, Yelena Glinka1,2, Anna Toulina1,2, Olga Ace1,2, Venkateswaran Subramaniam1,2, Serge Jothy1,2

1 Department of Laboratory Medicine and Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, Canada, 2 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada

Abstract

Background

Cancer stem cells (CSCs) have increased resistance to cancer chemotherapy. They can be enriched as drug-surviving CSCs (D-CSCs) by growth with chemotherapeutic drugs, and/or by sorting of cells expressing CSC markers such as aldehyde dehydrogenase-1 (ALDH). CSCs form colonies in agar, mammospheres in low-adherence cultures, and tumors following xenotransplantation in Scid mice. We hypothesized that tranilast, a non-toxic orally active drug with anti-cancer activities, would inhibit breast CSCs.

Methodology/Findings

We examined breast cancer cell lines or D-CSCs generated by growth of these cells with mitoxantrone. Tranilast inhibited colony formation, mammosphere formation and stem cell marker expression. Mitoxantrone-selected cells were enriched for CSCs expressing stem cell markers ALDH, c-kit, Oct-4, and ABCG2, and efficient at forming mammospheres. Tranilast markedly inhibited mammosphere formation by D-CSCs and dissociated formed mammospheres, at pharmacologically relevant concentrations. It was effective against D-CSCs of both HER-2+ and triple-negative cell lines. Tranilast was also effective in vivo, since it prevented lung metastasis in mice injected i.v. with triple-negative (MDA-MB-231) mitoxantrone-selected cells. The molecular targets of tranilast in cancer have been unknown, but here we demonstrate it is an aryl hydrocarbon receptor (AHR) agonist and this plays a key role. AHR is a transcription factor activated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polycyclic aromatic hydrocarbons and other ligands. Tranilast induced translocation of the AHR to the nucleus and stimulated CYP1A1 expression (a marker of AHR activation). It inhibited binding of the AHR to CDK4, which has been linked to cell-cycle arrest. D-CSCs expressed higher levels of the AHR than other cells. Knockdown of the AHR with siRNA, or blockade with an AHR antagonist, entirely abrogated the anti-proliferative and anti-mammosphere activity of tranilast. Thus, the anti-cancer effects of tranilast are AHR dependent.

Conclusion/Significance

We show that tranilast is an AHR agonist with inhibitory effects on breast CSCs. It is effective against CSCs of triple-negative breast cancer cells selected for anti-cancer drug resistance. These results suggest it might find applications in the treatment of breast cancer.

Citation: Prud'homme GJ, Glinka Y, Toulina A, Ace O, Subramaniam V, et al. (2010) Breast Cancer Stem-Like Cells Are Inhibited by a Non-Toxic Aryl Hydrocarbon Receptor Agonist. PLoS ONE 5(11): e13831. doi:10.1371/journal.pone.0013831

Editor: Andy T. Y. Lau, University of Minnesota, United States of America

Received: June 24, 2010; Accepted: October 18, 2010; Published: November 3, 2010

Copyright: © 2010 Prud'homme et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This study was funded by the Canadian Breast Cancer Research Alliance (grant # 020644; URL: www.breast.cancer.ca), the Ontario Institute for Cancer Research (Province of Ontario, Canada; grant # 05NOV194; URL: www.oicr.on.ca), the Canadian Institutes of Health Research (grant # III 94588; URL: www.cihr-irsc.gc.ca), and the Li Ka Shing Knowledge Institute and Keenan Research Centre of St. Michael's Hospital (Toronto, Canada) (URL: www.stmichaelshospital.com). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

* E-mail: prudhommeg@smh.ca

full-text:
PLoS ONE: Breast Cancer Stem-Like Cells Are Inhibited by a Non-Toxic Aryl Hydrocarbon Receptor Agonist




ONCOLOGÍA
Un fármaco para el asma consigue frenar la expansión del cáncer de mama en ratones
Actualidad Ultimas noticias - JANOes
JANO.es · 04 Noviembre 2010 10:02

Una investigación canadiense descubre que tranilast reduce el crecimiento del tumor canceroso primario en un 50% y evita su expansión a los pulmones.

Un fármaco utilizado habitualmente en Japón y Corea para tratar el asma detiene la expansión de las células del cáncer de mama que suelen ser resistentes a la quimioterapia, según un estudio del Hospital Saint Michael de la Universidad de Toronto, en Canadá, que se publica en la revista PLoS ONE.

Según explica Gerald Prud'homme, director del estudio, "tranilast, un fármaco aprobado para su uso en Japón y Corea del Sur y que no se utiliza en Canadá o Estados Unidos se ha utilizado durante más de dos décadas para tratar el asma y otros trastornos alérgicos, incluidos la rinitis alérgica y la dermatitis atópica. Ahora, nuestro estudio es el primero en descubrir que no sólo se detiene la expansión del cáncer de mama, sino también cómo el fármaco se dirige a las células de cáncer de mama".

Los investigadores produjeron células madre de cáncer de mama, que dan lugar a otras células cancerígenas, en el laboratorio. Las células fueron inyectadas en dos grupos de ratones, incluyendo un grupo, que también fue tratado con tranilast. Los científicos descubrieron que el fármaco reducía el crecimiento del tumor canceroso primario en un 50% y evitaron la expansión del cáncer a los pulmones. El equipo también identificó una molécula en las células cancerígenas que se une a tranilast y parece ser la responsable de este efecto anticancerígeno.

Tranilast se une a una molécula conocida como receptor de hidrocarburo aryl (AHR), que regula el crecimiento celular y algunos aspectos de la inmunidad. Esto hace al fármaco beneficioso para tratar las alergias, enfermedades inflamatorias y el cáncer.

"Por primera vez fuimos capaces de mostrar que tranilast es prometedor para el tratamiento del cáncer de mama en niveles comúnmente tolerados por pacientes que usan el fármaco para otros trastornos médico. Estos resultados son muy alentadores y estamos ampliando nuestros estudios. Se necesitan más estudios para determinar si el fármaco es eficaz contra diferentes tipos de cánceres de mama y otros cánceres, y su interacción con los fármacos anticancerígenos", concluye Prud'homme.


PLoS ONE 5(11), e13831; doi:10.1371/journal.pone.0013831
PLoS ONE: Breast Cancer Stem-Like Cells Are Inhibited by a Non-Toxic Aryl Hydrocarbon Receptor Agonist

Hospital Saint Michael
St. Michael's

Actualidad Ultimas noticias - JANOes - Un farmaco para el asma consigue frenar la expansion del cancer de mama en ratones - JANO.es - ELSEVIER