TGF-β-Induced TMEPAI Promotes Epithelial–Mesenchymal Transition in Doxorubicin-Treated Triple-Negative Breast Cancer Cells via SMAD3 and PI3K/AKT Pathway Alteration

Abstract

Introduction Epithelial–mesenchymal transition (EMT) and overexpression of drug efflux transporters have been reported to cause doxorubicin resistance. Our previous study indicated that TMEPAI (transmembrane prostate androgen-induced protein) attenuated doxorubicin sensitivity in triple-negative breast cancer cells. However, how TMEPAI contributes to doxorubicin resistance in TNBC remains unclear. Thus, the present study aimed to elucidate the mechanism of TMEPAI in doxorubicin resistance in triple-negative breast cancer cells. Methods We used BT549, triple-negative cells wild type (WT), and BT549 TMEPAI knock-out. Both cells were treated with TGF-β 2 ng/mL for 24 hours, followed by TGF-β 2 ng/mL and doxorubicin 12.9 nM for another 24 hours. Afterward, the cells were harvested and counted. Cells were further lysed and used for RT-PCR and Western blot analysis. We determined the expression levels of proliferation, apoptosis, EMT markers, and drug efflux transporters. Additionally, we investigated the expressions of PI3K as well as SMAD3 and AKT phosphorylation. Results TNBC cells were shown to be less sensitive to doxorubicin in the presence of TMEPAI. TMEPAI was shown to alleviate the mRNA expressions of apoptosis markers: Bax, Bcl2, Caspase-3, and Caspase-9. Our results indicated that the presence of TMEPAI greatly amplifies EMT and increases drug efflux transporter expressions after doxorubicin treatment. Furthermore, our findings demonstrated that TMEPAI reduced the action of doxorubicin in inhibiting SMAD3 phosphorylation. TMEPAI was also shown to modify the effect of doxorubicin by reducing PI3K expressions and Akt phosphorylation in triple-negative breast cancer cells. Conclusion Our findings indicate that TMEPAI promotes EMT and drug efflux transporters at least in part by shifting doxorubicin action from SMAD3 phosphorylation reduction to PI3K/AKT inhibition in triple-negative breast cancer cells.

Revisiting Epithelial Carcinogenesis

“…Moreover in a pre-clinical model of TNBC was demonstrated a causal relationship between therapy-induced senescence and the generation of chemoresistant stem-like populations (208). Also consistent, TNBC cells exposed to doxorubicin induce the EMT transcription factors to increase their resistance to treatments (209). Tumors conformed mostly by triple-negative cells are the most lethal subtype of breast cancer and lack effective therapeutic options (198).…”

The progressive trend of modeling and drug screening systems of breast cancer bone metastasis

“…Also, TGF- β regulates connective tissue growth factor (CTGF)/IL-11 [ 50 ], CXCR4/MMP-1 [ 51 ], and cyclooxygenase (COX)-2 [ 52 ]. Of note, TGF-β has the principal role in the epithelial-mesenchymal transition (EMT) of breast cancer cells [ 53 ].…”

Prostate transmembrane androgen inducible protein 1 (PMEPA1): regulation and clinical implications

“…A study examining the role of adriamycin in triple-negative breast cancer cells (TNBC) suggested that PMEPA1-positive cells had a higher phosphorylation profile of PI3K and AKT ( 22 ). Several different molecular mechanisms have been established of how PMEPA1 regulates the PI3K-AKT-mTOR signaling pathway (summarized in Figure 1 ).…”