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The hostile hypoxic microenvironment takes primary responsibility for the rapid expansion of breast cancer tumors. However, the underlying mechanism is not fully understood. Here, using RNA sequencing (RNA-seq) analysis, we identified a hypoxia-induced long noncoding RNA (lncRNA) KB-1980E6.3, which is aberrantly upregulated in clinical breast cancer tissues and closely correlated with poor prognosis of breast cancer patients. The enhanced lncRNA KB-1980E6.3 facilitates breast cancer stem cells (BCSCs) self-renewal and tumorigenesis under hypoxic microenvironment both in vitro and in vivo. Mechanistically, lncRNA KB-1980E6.3 recruited insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) to form a lncRNA KB-1980E6.3/IGF2BP1/c-Myc signaling axis that retained the stability of c-Myc mRNA through increasing binding of IGF2BP1 with m6A-modified c-Myc coding region instability determinant (CRD) mRNA. In conclusion, we confirm that lncRNA KB-1980E6.3 maintains the stemness of BCSCs through lncRNA KB-1980E6.3/IGF2BP1/c-Myc axis and suggest that disrupting this axis might provide a new therapeutic target for refractory hypoxic tumors.

Myocardial remodeling is a major contributor in the development of heart failure (HF) after myocardial infarction (MI). Integrin-linked kinase (ILK), LIM-only adaptor PINCH-1, and α-parvin are essential components of focal adhesions (FAs), which are highly expressed in the heart. ILK binds tightly to PINCH-1 and α-parvin, which regulates FA assembly and promotes cell survival via the activation of the kinase Akt. Mice lacking ILK, PINCH or α-parvin have been shown to develop severe defects in the heart, suggesting that these proteins play a critical role in heart function. Utilizing failing human heart tissues (dilated cardiomyopathy, DCM), we found a 2.27-fold (p<0.001) enhanced expression of PINCH, 4 fold for α-parvin, and 10.5 fold (p<0.001) for ILK as compared to non-failing (NF) counterparts. No significant enhancements were found for the PINCH isoform PINCH-2 and parvin isoform β-parvin. Using a co-immunoprecipitation method, we also found that the PINCH-1-ILK-α-parvin (PIP) complex and Akt activation were significantly up-regulated. These observations were further corroborated with the mouse myocardial infarction (MI) and transaortic constriction (TAC) model. Thymosin beta4 (Tβ4), an effective cell penetrating peptide for treating MI, was found to further enhance the level of PIP components and Akt activation, while substantially suppressing NF-κB activation and collagen expression—the hallmarks of cardiac fibrosis. In the presence of an Akt inhibitor, wortmannin, we show that Tβ4 had a decreased effect in protecting the heart from MI. These data suggest that the PIP complex and activation of Akt play critical roles in HF development. Tβ4 treatment likely improves cardiac function by enhancing PIP mediated Akt activation and suppressing NF-κB activation and collagen-mediated fibrosis. These data provide significant insight into the role of the PIP-Akt pathway and its regulation by Tβ4 treatment in post-MI.

Citrate, a substance being related to de novo fatty acid synthesis and tricarboxylic acid (TCA) cycle, has a pivotal role in cell survival. However, the molecular mechanisms that regulate intracellular citrate in triple-negative breast cancer (TNBC), especially under hypoxic condition, remain poorly understood. Here we find that hypoxia (1% O 2 ) induces DNA damage-independent ATM activation (oxidized ATM) and suppression of oxidized ATM reduces intracellular citrate via decreasing the levels of phosphofructokinase (PFKP) and citrate synthase (CS), two key glucose metabolism-associated enzymes. Mechanistically, PFKP is regulated by HIF1A at the translational level, whereas CS is of posttranscriptional regulation by UBR5-mediated ubiquitination. Interestingly, accumulation of citrate in cytoplasm or exogenous citrate significantly enhances cell migration, invasion, and metastasis of hypoxic TNBC cells in vitro and in mice xenografts. The underlying mechanism mainly involves citrate-stimulated activation of the AKT/ERK/MMP2/9 signaling axis. Our findings unravel a novel function of oxidized ATM in promoting migration, invasion, and metastasis of TNBC.

Back ground Pro-inflammatory cytokine tumor necrosis factor α (TNFα) induces β-adrenergic receptor (βAR) desensitization, but mechanisms proximal to the receptor in contributing to cardiac dysfunction are not known. Methods and Results Two different pro-inflammatory transgenic mouse models with cardiac overexpression of Myotrophin (a pro-hypertrophic molecule) or TNFα showed that TNFα alone is sufficient to mediate βAR desensitization as measured by cardiac adenylyl cyclase activity. M-mode echocardiography in these mouse models showed cardiac dysfunction paralleling βAR desensitization independent of sympathetic overdrive. TNFα-mediated βAR desensitization that precedes cardiac dysfunction is associated with selective upregulation of G-protein coupled receptor kinase 2 (GRK2) in both the mouse models. In vitro studies in β2 AR overexpressing HEK 293 cells showed significant βAR desensitization, GRK2 upregulation and recruitment to the βAR complex following TNFα. Interestingly, inhibition of PI3K abolished GRK2-mediated βAR phosphorylation and GRK2 recruitment upon TNFα. Furthermore, TNFα-mediated βAR phosphorylation was not blocked with βAR antagonist propranolol. Additionally, TNFα administration in transgenic mice with cardiac overexpression of Gβγ sequestering peptide βARK-ct could not prevent βAR desensitization or cardiac dysfunction showing that GRK2 recruitment to the βAR is Gβγ independent. siRNA knock down of GRK2 resulted in loss of TNFα-mediated βAR phosphorylation. Consistently, cardiomyocytes from mice with cardiac-specific GRK2 ablation normalized the TNFα-mediated loss in contractility showing that TNFα-induced βAR desensitization is GRK2 dependent. Conclusions TNFα-induced βAR desensitization is mediated by GRK2 and is independent of Gβγ uncovering a hitherto unknown cross-talk between TNFα and βAR function providing the underpinnings of inflammation-mediated cardiac dysfunction.