Abstract
Triple-negative breast cancers (TNBCs) are characterized by poor survival, prognosis, and gradual resistance to cytotoxic chemotherapeutics, like doxorubicin (DOX). The clinical utility of DOX is limited by its cardiotoxic and chemoresistant effects that manifest over time. To induce chemoresistance, TNBC rewires oncogenic gene expression and cell signaling pathways. Recent studies have demonstrated that reprogramming of branched-chain amino acids (BCAAs) metabolism facilitates tumor growth and survival. Branched-chain ketoacid dehydrogenase kinase (BCKDK), a regulatory kinase of the rate-limiting enzyme of the BCAA catabolic pathway, is reported to activate RAS/RAF/MEK/ERK signaling to promote tumor cell proliferation. However, it remains unexplored if BCKDK action remodels TNBC proliferation and survival per se and influences susceptibility to DOX-induced genotoxic stress. TNBC cells treated with DOX exhibited reduced BCKDK expression and intracellular BCKAs. Genetic and pharmacological inhibition of BCKDK in TNBC cell lines also showed a similar reduction in intracellular and secreted BCKAs. BCKDK silencing in TNBC cells downregulated mitochondrial metabolism genes, reduced electron complex protein expression, oxygen consumption, and ATP production. Transcriptome analysis of BCKDK silenced cells confirmed dysregulation of mitochondrial metabolic networks and upregulation of the apoptotic signaling pathway. Furthermore, BCKDK inhibition with concurrent DOX treatment exacerbated apoptosis, caspase activity, and loss of TNBC proliferation. Inhibition of BCKDK in TNBC also upregulated sestrin 2 and concurrently decreased mTORC1 signaling and protein synthesis. Overall, loss of BCKDK action in TNBC remodels BCAA flux, reduces protein translation triggering cell death, ATP insufficiency, and susceptibility to genotoxic stress.
Highlights
Triple-negative breast cancers (TNBCs) are an aggressive subtype of breast cancer constituting 10–15% of all breast cancers and are defined by the lack of expression of estrogen receptor (ER), progesterone receptor (PR), and the human epidermal growth factor receptor 2 (HER2) [1]
Since Branched-chain ketoacid dehydrogenase kinase (BCKDK) expression was altered in TNBCs and into branched-chain ketoacids (BCKAs) as well as its impact on TNBC growth and survival regulated by DOX, we examined the impact of altered BCKDK
We investigated the role of BCKDK in TNBC survival and metabolism and examined whether DOX’s anticancer Downregulating BCKDK inhibits proliferation, promotes effect involves targeting the branched-chain amino acids (BCAAs) catabolic pathway
Summary
Triple-negative breast cancers (TNBCs) are an aggressive subtype of breast cancer constituting 10–15% of all breast cancers and are defined by the lack of expression of estrogen receptor (ER), progesterone receptor (PR), and the human epidermal growth factor receptor 2 (HER2) [1]. We investigated the role of BCKDK in TNBC survival and metabolism and examined whether DOX’s anticancer Downregulating BCKDK inhibits proliferation, promotes effect involves targeting the BCAA catabolic pathway. DOX apoptosis, and potentiates DOX-mediated cell death treatment at 2 μM suppressed BCKDK, accelerated intracellular To decipher whether BCKDK silencing alters metabolism and BCKAs clearance and significantly increased mRNA and protein survival of TNBCs, MDA-MB231 cells were treated with either levels of BCAA degradation enzymes in two TNBC cell lines. BCKDK following transfection, while siBDK#1 showed reduced cell count inhibition suppressed mitochondrial function, reduced nascent at 48 h (Fig. S2C), confirming that TNBC requires functional BCKDK protein synthesis, and increased sestrin 2 (SESN2) expression, a for survival and proliferation. DNA damage marker, ataxia-telangiectasia mutated (ATM), suggesting increased genomic instability and apoptosis (Fig. 2A)
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