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Aromatase expression increases the survival and malignancy of estrogen receptor positive breast cancer cells.

Mukhopadhyay KD, Liu Z, Bandyopadhyay A, Kirma NB, Tekmal RR, Wang S, Sun LZ - PLoS ONE (2015)

Bottom Line: This raises the question of how the ERα positive metastatic breast cancer cells survive after they enter blood and lymph circulation, where estrogen level is very low in postmenopausal women.Furthermore, treatment with the aromatase substrate, testosterone, inhibited suspension culture-induced apoptosis whereas an aromatase inhibitor attenuated the effect of testosterone suggesting that suspended circulating ERα positive breast cancer cells may up-regulate intracrine estrogen activity for survival.The increased malignant phenotype was confirmed to be due to aromatase expression as the growth of orthotopic tumors regressed with systemic administration of an aromatase inhibitor.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, United States of America.

ABSTRACT
In postmenopausal women, local estrogen produced by adipose stromal cells in the breast is believed to support estrogen receptor alpha (ERα) positive breast cancer cell survival and growth. This raises the question of how the ERα positive metastatic breast cancer cells survive after they enter blood and lymph circulation, where estrogen level is very low in postmenopausal women. In this study, we show that the aromatase expression increased when ERα positive breast cancer cells were cultured in suspension. Furthermore, treatment with the aromatase substrate, testosterone, inhibited suspension culture-induced apoptosis whereas an aromatase inhibitor attenuated the effect of testosterone suggesting that suspended circulating ERα positive breast cancer cells may up-regulate intracrine estrogen activity for survival. Consistent with this notion, a moderate level of ectopic aromatase expression rendered a non-tumorigenic ERα positive breast cancer cell line not only tumorigenic but also metastatic in female nude mice without exogenous estrogen supplementation. The increased malignant phenotype was confirmed to be due to aromatase expression as the growth of orthotopic tumors regressed with systemic administration of an aromatase inhibitor. Thus, our study provides experimental evidence that aromatase plays an important role in the survival of metastatic ERα breast cancer cells by suppressing anoikis.

No MeSH data available.


Related in: MedlinePlus

Aromatase-mediated inhibition of anoikis.Cells were plated as duplicate in ultra-low attachment 6-well plate for suspension culture. The cells were treated without or with 10 nM testosterone or 1 M letrozole, or both for 16 hr. Cell lysates were then used for apoptosis measurement with an apoptosis detection kit (Roche). Absorbance(A405nm-A490nm) indicates relative apoptosis. The data are presented as mean±SEM of duplicate wells (*p<0.05). One way ANOVA were used to find the significant difference.
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pone.0121136.g004: Aromatase-mediated inhibition of anoikis.Cells were plated as duplicate in ultra-low attachment 6-well plate for suspension culture. The cells were treated without or with 10 nM testosterone or 1 M letrozole, or both for 16 hr. Cell lysates were then used for apoptosis measurement with an apoptosis detection kit (Roche). Absorbance(A405nm-A490nm) indicates relative apoptosis. The data are presented as mean±SEM of duplicate wells (*p<0.05). One way ANOVA were used to find the significant difference.

Mentions: Although transformed cells are resistant to suspension-induced programmed cell death called anoikis, many transformed cell lines still undergo significant apoptosis when suspended in culture. On the other hand, estrogen signaling is known to inhibit apoptosis. Thus, we investigated whether increased aromatase and ERα under suspension culture can inhibit anoikis. By performing the Cell Death Detection ELISA Assay, we found that suspension culture caused anoikis of ZR-75-1/Aro-Cl.10 and CAMA-1 cells (Fig. 4). But this suspension culture induced anoikis was shown to be inhibited by the supplementation of 10 nM testosterone, which is converted to estradiol by aromatase. Conversely, addition of the aromatase inhibitor letrozole blocked the testosterone-induced anoikis inhibition (Fig. 4) suggesting that the enhanced expression of aromatase and ERα in suspension culture likely increased estrogen synthesis and signalling [15–17].


Aromatase expression increases the survival and malignancy of estrogen receptor positive breast cancer cells.

Mukhopadhyay KD, Liu Z, Bandyopadhyay A, Kirma NB, Tekmal RR, Wang S, Sun LZ - PLoS ONE (2015)

Aromatase-mediated inhibition of anoikis.Cells were plated as duplicate in ultra-low attachment 6-well plate for suspension culture. The cells were treated without or with 10 nM testosterone or 1 M letrozole, or both for 16 hr. Cell lysates were then used for apoptosis measurement with an apoptosis detection kit (Roche). Absorbance(A405nm-A490nm) indicates relative apoptosis. The data are presented as mean±SEM of duplicate wells (*p<0.05). One way ANOVA were used to find the significant difference.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383596&req=5

pone.0121136.g004: Aromatase-mediated inhibition of anoikis.Cells were plated as duplicate in ultra-low attachment 6-well plate for suspension culture. The cells were treated without or with 10 nM testosterone or 1 M letrozole, or both for 16 hr. Cell lysates were then used for apoptosis measurement with an apoptosis detection kit (Roche). Absorbance(A405nm-A490nm) indicates relative apoptosis. The data are presented as mean±SEM of duplicate wells (*p<0.05). One way ANOVA were used to find the significant difference.
Mentions: Although transformed cells are resistant to suspension-induced programmed cell death called anoikis, many transformed cell lines still undergo significant apoptosis when suspended in culture. On the other hand, estrogen signaling is known to inhibit apoptosis. Thus, we investigated whether increased aromatase and ERα under suspension culture can inhibit anoikis. By performing the Cell Death Detection ELISA Assay, we found that suspension culture caused anoikis of ZR-75-1/Aro-Cl.10 and CAMA-1 cells (Fig. 4). But this suspension culture induced anoikis was shown to be inhibited by the supplementation of 10 nM testosterone, which is converted to estradiol by aromatase. Conversely, addition of the aromatase inhibitor letrozole blocked the testosterone-induced anoikis inhibition (Fig. 4) suggesting that the enhanced expression of aromatase and ERα in suspension culture likely increased estrogen synthesis and signalling [15–17].

Bottom Line: This raises the question of how the ERα positive metastatic breast cancer cells survive after they enter blood and lymph circulation, where estrogen level is very low in postmenopausal women.Furthermore, treatment with the aromatase substrate, testosterone, inhibited suspension culture-induced apoptosis whereas an aromatase inhibitor attenuated the effect of testosterone suggesting that suspended circulating ERα positive breast cancer cells may up-regulate intracrine estrogen activity for survival.The increased malignant phenotype was confirmed to be due to aromatase expression as the growth of orthotopic tumors regressed with systemic administration of an aromatase inhibitor.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, United States of America.

ABSTRACT
In postmenopausal women, local estrogen produced by adipose stromal cells in the breast is believed to support estrogen receptor alpha (ERα) positive breast cancer cell survival and growth. This raises the question of how the ERα positive metastatic breast cancer cells survive after they enter blood and lymph circulation, where estrogen level is very low in postmenopausal women. In this study, we show that the aromatase expression increased when ERα positive breast cancer cells were cultured in suspension. Furthermore, treatment with the aromatase substrate, testosterone, inhibited suspension culture-induced apoptosis whereas an aromatase inhibitor attenuated the effect of testosterone suggesting that suspended circulating ERα positive breast cancer cells may up-regulate intracrine estrogen activity for survival. Consistent with this notion, a moderate level of ectopic aromatase expression rendered a non-tumorigenic ERα positive breast cancer cell line not only tumorigenic but also metastatic in female nude mice without exogenous estrogen supplementation. The increased malignant phenotype was confirmed to be due to aromatase expression as the growth of orthotopic tumors regressed with systemic administration of an aromatase inhibitor. Thus, our study provides experimental evidence that aromatase plays an important role in the survival of metastatic ERα breast cancer cells by suppressing anoikis.

No MeSH data available.


Related in: MedlinePlus