erastin and Triple-Negative-Breast-Neoplasms

Triple-negative breast cancer (TNBC) is a highly malignant type of breast cancer and lacks effective therapy. Targeting cysteine-dependence is an emerging strategy to treat the mesenchymal TNBC. However, many TNBC cells are non-mesenchymal and unresponsive to cysteine deprivation. To overcome such resistance, three selective HDAC6 inhibitors (Tubacin, CAY10603, and Tubastatin A), identified by epigenetic compound library screening, can synergize with cysteine deprivation to induce cell death in the non-mesenchymal TNBC. Despite the efficacy of HDAC6 inhibitor, knockout of HDAC6 did not mimic the synthetic lethality induced by its inhibitors, indicating that HDAC6 is not the actual target of HDAC6 inhibitor in this context. Instead, transcriptomic profiling showed that tubacin triggers an extensive gene transcriptional program in combination with erastin, a cysteine transport blocker. Notably, the zinc-related gene response along with an increase of labile zinc was induced in cells by the combination treatment. The disturbance of zinc homeostasis was driven by PKCγ activation, which revealed that the PKCγ signaling pathway is required for HDAC6 inhibitor-mediated synthetic lethality. Overall, our study identifies a novel function of HDAC6 inhibitors that function as potent sensitizers of cysteine deprivation and are capable of abolishing cysteine-independence in non-mesenchymal TNBC.

Topics: Anilides; Carbamates; Cell Death; Cell Line, Tumor; Cysteine; Enzyme Activation; Epithelial Cells; Female; Gene Knockout Techniques; HEK293 Cells; Histone Deacetylase 6; Histone Deacetylase Inhibitors; Homeostasis; Humans; Hydroxamic Acids; Indoles; Neoplasm Proteins; Oxazoles; Piperazines; Protein Kinase C; Small Molecule Libraries; Transcription, Genetic; Transcriptome; Triple Negative Breast Neoplasms; Zinc

Ferroptosis is an iron-dependent, lipid peroxide-driven cell death caused by inhibition of the cystine/glutamate transporter, which is of importance for the survival of triple-negative breast cancer (TNBC) cells. Erastin is a low molecular weight chemotherapy drug that induces ferroptosis; however, poor water solubility and renal toxicity have limited its application. Exosomes, as drug delivery vehicles with low immunogenicity, high biocompatibility and high efficiency, have attracted increasing attention in recent years. Herein, we developed a formulation of erastin-loaded exosomes labeled with folate (FA) to form FA-vectorized exosomes loaded with erastin (erastin@FA-exo) to target TNBC cells with overexpression of FA receptors. The characterization, drug release, internalization and anti-tumor effect in vitro of erastin@FA-exo were determined. Erastin@FA-exo could increase the uptake efficiency of erastin into MDA-MB-231 cells; compared with erastin@exo and free erastin, erastin@FA-exo has a better inhibitory effect on the proliferation and migration of MDA-MB-231 cells. Furthermore, erastin@FA-exo promoted ferroptosis with intracellular depletion of glutathione and reactive oxygen species overgeneration. Western blot analyses revealed that erastin@FA-exo suppressed expression of glutathione peroxidase 4 (GPX4) and upregulated expression of cysteine dioxygenase (CDO1). We conclude that targeting and biocompatibility of exosome-based erastin preparations provide an innovative and powerful delivery platform for anti-cancer therapy.

Topics: Cell Death; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Cysteine Dioxygenase; Drug Delivery Systems; Exosomes; Folic Acid; Gene Expression Regulation, Neoplastic; Glutathione Peroxidase; Humans; Phospholipid Hydroperoxide Glutathione Peroxidase; Piperazines; Reactive Oxygen Species; Triple Negative Breast Neoplasms