MICAL-L2, as an estrogen-responsive gene, is involved in ER-positive breast cancer cell progression and tamoxifen sensitivity via the AKT/mTOR pathway.

Endocrine treatment, particularly tamoxifen, has shown significant improvement in the prognosis of patients with estrogen receptor-positive (ER-positive) breast cancer. However, the clinical utility of this treatment is often hindered by the development of endocrine resistance. Therefore, a comprehensive understanding of the underlying mechanisms driving ER-positive breast cancer carcinogenesis and endocrine resistance is crucial to overcome this clinical challenge. In this study, we investigated the expression of MICAL-L2 in ER-positive breast cancer and its impact on patient prognosis. We observed a significant upregulation of MICAL-L2 expression in ER-positive breast cancer, which correlated with a poorer prognosis in these patients. Furthermore, we found that estrogen-ERβ signaling promoted the expression of MICAL-L2. Functionally, our study demonstrated that MICAL-L2 not only played an oncogenic role in ER-positive breast cancer tumorigenesis but also influenced the sensitivity of ER-positive breast cancer cells to tamoxifen. Mechanistically, as an estrogen-responsive gene, MICAL-L2 facilitated the activation of the AKT/mTOR signaling pathway in ER-positive breast cancer cells. Collectively, our findings suggest that MICAL-L2 could serve as a potential prognostic marker for ER-positive breast cancer and represent a promising molecular target for improving endocrine treatment and developing therapeutic approaches for this subtype of breast cancer.

Wen P ，Li J ，Wen Z ，Guo X ，Ma G ，Hu S ，Xu J ，Zhao H ，Li R ，Liu Y ，Wang Y ，Gao J ... -  《-》

Adipocyte-conditioned medium induces tamoxifen resistance by activating PI3K/Akt/mTOR pathway in estrogen receptor-positive breast cancer cells.

Resistance to endocrine therapy is a major clinical challenge in estrogen receptor (ER)-positive breast cancer. Obesity is associated with the clinical response to ER-positive breast cancers; however, the mechanism underlying obesity-induced resistance to endocrine therapy in ER-positive breast cancers remains unclear. In this study, we investigated the molecular mechanisms underlying obesity-induced resistance to tamoxifen (TAM), an anti-estrogen agent, in the ER-positive breast cancer cell line MCF-7 using differentiated adipocyte-conditioned medium (D-CM). Treatment of the cells with D-CM promoted TAM resistance by reducing TAM-induced apoptosis. The expression levels of the ERα target genes were higher in D-CM-treated cells than those in untreated ones. In contrast, when the cells were cultured in the presence of TAM, the expression levels were decreased, with or without D-CM. Moreover, the expression of the markers for cancer stem-like cells (CSCs) and mammosphere formation was enhanced by co-treating with D-CM and TAM, compared with TAM alone. The phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway was activated in MCF-7 cells by D-CM treatment, even in the presence of TAM. Inhibition of the PI3K/Akt/mTOR pathway decreased the expression levels of the CSC markers, suppressed mammosphere formation, and resensitized to TAM via inducing apoptosis in D-CM-treated cells. These results indicate that the conditioned medium of differentiated adipocytes promoted TAM resistance by inducing the CSC phenotype through activation of the PI3K/Akt/mTOR pathway in ER-positive breast cancer cells. Thus, the PI3K/Akt/mTOR pathway may be a therapeutic target in obese patients with ER-positive breast cancers.

Nakatsuji M ，Fujimori K 《-》

Overcoming endocrine resistance due to reduced PTEN levels in estrogen receptor-positive breast cancer by co-targeting mammalian target of rapamycin, protein kinase B, or mitogen-activated protein kinase kinase.

Fu X ，Creighton CJ ，Biswal NC ，Kumar V ，Shea M ，Herrera S ，Contreras A ，Gutierrez C ，Wang T ，Nanda S ，Giuliano M ，Morrison G ，Nardone A ，Karlin KL ，Westbrook TF ，Heiser LM ，Anur P ，Spellman P ，Guichard SM ，Smith PD ，Davies BR ，Klinowska T ，Lee AV ，Mills GB ，Rimawi MF ，Hilsenbeck SG ，Gray JW ，Joshi A ，Osborne CK ，Schiff R ... -  《-》

Luminal breast cancer cell lines overexpressing ZNF703 are resistant to tamoxifen through activation of Akt/mTOR signaling.

Zhang X ，Mu X ，Huang O ，Xie Z ，Jiang M ，Geng M ，Shen K ... -  《PLoS One》

CSNK1G2 differently sensitizes tamoxifen-induced decrease in PI3K/AKT/mTOR/S6K and ERK signaling according to the estrogen receptor existence in breast cancer cells.

Nguyen Hoang AT ，Hoe KL ，Lee SJ 《PLoS One》