Project description:CDK4/6 inhibition is the standard of care for estrogen receptor positive (ER+) breast cancer, although cytostasis is frequently observed, and new treatment strategies that enhance efficacy are required. We performed a genome-wide CRISPR screen to identify genetic determinants of CDK4/6 inhibitors sensitivity. Multiple genes involved in oxidative stress and ferroptosis modulated palbociclib sensitivity. Depletion or inhibition of GPX4 increased sensitivity to palbociclib in ER+ breast cancer models, and sensitised triple negative breast cancer models to palbociclib, with GPX4 null xenografts being highly sensitive to palbociclib. Palbociclib induced oxidative stress and disordered lipid metabolism with lipid peroxidation, leading to a ferroptosis-sensitive state. Lipid peroxidation relied on a peroxisome AGPAT3-dependent pathway in ER+ breast cancer models, rather than the classical ACSL4 pathway. Our data demonstrate that CDK4/6 inhibition creates vulnerability to ferroptosis that could be exploited through combination with GPX4 inhibitors, enhancing sensitivity to CDK4/6 inhibition in breast cancer.
Project description:Acute Pten loss initiates prostate tumorigenesis characterized by cellular senescence response. Here we examine the cellular senescence response in epithelial individual cells, by single-cell RNA sequencing (scRNAseq) in Ptenpc-/- and Ptenpc-/-; Timp1-/- GEMMs. ScRNAseq analysis determines a cluster of senescent cells expressing the senescence-related genes. A significant positive correlation is observed between the senescence score and Bcl2 expression. This provides the rational for targeting senescent cells using Bcl2 inhibitor.
Project description:Nrf1 is a transcription factor that is highly conserved and reacts to oxidative, proteotoxic and endoplasmic reticulum stress in cells; nonetheless, its function in the context of acute kidney injury (AKI) remains unclear. Using a model of cisplatin-induced nephrotoxicity in vitro and in vivo, we found that the expression of Nrf1, which is expressed at high levels in renal tubular cells, was significantly downregulated after cisplatin treatment. Proximal tubule-specific Nrf1 knockout worsened and Nrf1 overexpression attenuated cisplatin-induced (CI)-AKI. RNA sequencing analysis revealed that Nrf1 overexpression decreased the number of transcripts involved in cell death, specifically those associated with ferroptosis, after cisplatin treatment. Furthermore, ferroptosis responses, characterized by increased lipid peroxidation and iron content and decreased FPN, XCT and glutathione peroxidase 4 levels, were attenuated in Nrf1-overexpressing HK-2 cells but worsened in Nrf1-knockout mice and Nrf1-knockdown HK-2 cells. Moreover, lipidomic and RNA sequencing results indicated that Nrf1 regulated the levels of polyunsaturated fatty acids (PUFAs) and inhibited the expression of ACSL4. Additionally, ChIP experiments revealed that Nrf1 bound to the promoter region of ACSL4, thereby inhibiting its transcription. Furthermore, inhibitors of ACSL4 significantly reduced the sensitivity of HK-2 cells to ferroptosis induced by Nrf1 knockdown. Collectively, these findings suggest that Nrf1 is a novel target for inhibiting ferroptosis in renal tubule cells by suppressing the transcription and expression of ACSL4, thereby reducing PUFA levels. Consequently, activators developed for Nrf1 may hold therapeutic potential in the treatment of patients with CI-AKI.
Project description:Understanding mechanisms that determine the response of cells to ferroptotic stress is a timely issue that has significant ramifications for biology and pathology. We investigated these mechanisms in the context of breast cancer where tumors are comprised of diverse populations of cancer cells that differ in their ferroptosis sensitivity. Using single-cell RNA-sequencing, we determined that cancer cell populations with luminal differentiation are more resistant to ferroptosis than other cells within a heterogeneous tumor. Subsequent bioinformatic analysis and experimentation revealed that GATA3, a transcription factor that promotes luminal differentiation, has a causal role in ferroptosis resistance in luminal breast cancer cells. In pursuit of the mechanism involved, we found that GATA3 represses the expression of integrin β1 and its downstream signaling cascade. This observation led us to demonstrate that integrin β1 signaling is necessary for sensitivity to ferroptosis in basal breast cancer cells because it regulates a FAK/ROCK pathway that sustains the expression of ACSL4, a lipid-modifying enzyme that is essential for ferroptosis. The repression of integrin β1 by GATA3 inhibits this signaling pathway rendering cells ferroptosis resistant. Together, these data provide insight into mechanisms of ferroptosis sensitivity and resistance that are linked to the cell biology and signaling pathways of the diverse types of cells present in breast tumors.
Project description:Identification of IDH mutations has uncovered the crucial role played by metabolism in glioma-genesis. Oncolytic herpes virus (oHSV) therapy initiates direct tumor debulking by tumor lysis and also activates antitumor immunity however little is known about the role of glioma metabolism in determining oHSV efficacy. Here we identified that oHSV therapy rewired central carbon metabolism with increased glucose utilization towards oxidative phosphorylation and shuttled glutamine towards reductive carboxylation in IDH wildtype (wt) glioma. The switch in metabolism resulted in increased lipid synthesis, and cellular ROS. PKC induced ACSL4 in oHSV treated cells led to lipid peroxidation and ferroptosis. Ferroptosis was critical to launch an antitumor immune response important for efficacy. Mutant IDH (IDHR132H) gliomas are incapable of reductive carboxylation and hence ferroptosis. Pharmacological blockade of IDHR132H induced ferroptosis and antitumor immunity. This study provides a rationale to treat high grade IDHR132H glioma patients under oHSV treatment with IDHR132H inhibitor.
Project description:Ferroptosis is a form of regulated necrotic cell death controlled by glutathione peroxidase 4 (GPX4). At present, mechanisms that could predict sensitivity and/or resistance and that may be exploited to modulate this form of cell death are needed. We applied two independent approaches, a genome-wide CRISPR-based genetic screen and microarray analysis of ferroptosis-resistant cell lines to uncover acyl-CoA synthetase long-chain family member 4 (Acsl4) as an essential component for ferroptosis execution.