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Targeting aromatase deprives ER+ breast cancers of estrogens and is an effective therapeutic approach for these tumors. However, drug resistance is an unmet clinical need. Lipidomic analysis of long-term estrogen-deprived (LTED) ER+ breast cancer cells, a model of aromatase inhibitor resistance, revealed enhanced intracellular lipid storage. Functional metabolic analysis showed that lipid droplets together with peroxisomes, which we showed to be enriched and active in the LTED cells, controlled redox homeostasis and conferred metabolic adaptability to the resistant tumors. This reprogramming was controlled by acetyl-CoA-carboxylase-1 (ACC1), whose targeting selectively impaired LTED survival. However, the addition of branched- and very long–chain fatty acids reverted ACC1 inhibition, a process that was mediated by peroxisome function and redox homeostasis. The therapeutic relevance of these findings was validated in aromatase inhibitor–treated patient-derived samples. Last, targeting ACC1 reduced tumor growth of resistant patient-derived xenografts, thus identifying a targetable hub to combat the acquisition of estrogen independence in ER+ breast cancers. Editor's summary: Aromatase inhibitors prevent estrogen production and can be effective against ER+ breast cancer, but subsequent tumor metabolic adaptation often thwarts treatment efficacy. Bacci et al. report that acetyl-CoA-carboxylase-1 (ACC1) promotes lipid mobilization in estrogen-deprived breast cancer cells, leading to anti-estrogen therapy resistance. Pharmacologically targeting ACC1 in patient-derived, treatment-resistant xenograft models reduced tumor growth and increased mouse survival. This work indicates that targeting ACC1 may be an avenue to resensitize ER+ breast cancer to endocrine-based therapies. —Catherine Charneski [ABSTRACT FROM AUTHOR]

Tumor recurrence is the leading cause of breast cancer-related death. Recurrences are largely driven by cancer cells that survive therapeutic intervention. This poorly understood population is referred to as minimal residual disease. Here, using mouse models that faithfully recapitulate human disease together with organoid cultures, we have demonstrated that residual cells acquire a transcriptionally distinct state from normal epithelium and primary tumors. Gene expression changes and functional characterization revealed altered lipid metabolism and elevated ROS as hallmarks of the cells that survive tumor regression. These residual cells exhibited increased oxidative DNA damage, potentiating the acquisition of somatic mutations during hormonal-induced expansion of the mammary cell population. Inhibition of either cellular fatty acid synthesis or fatty acid transport into mitochondria reduced cellular ROS levels and DNA damage, linking these features to lipid metabolism. Direct perturbation of these hallmarks in vivo, either by scavenging ROS or by halting the cyclic mammary cell population expansion, attenuated tumor recurrence. Finally, these observations were mirrored in transcriptomic and histological signatures of residual cancer cells from neoadjuvant-treated breast cancer patients. These results highlight the potential of lipid metabolism and ROS as therapeutic targets for reducing tumor recurrence in breast cancer patients., Introduction Despite advances in detection and therapy, breast cancer remains the second leading cause of cancer-related death in women. Mortality is largely due to tumor recurrence following initial therapeutic intervention [...]

Regulation of the Saccharomyces cerevisiae HO promoter has been shown to require the recruitment of chromatin-modifying and -remodeling enzymes. Despite this, relatively little is known about what changes to chromatin structure occur during the course of regulation at HO. Here, we used indirect end labeling in synchronized cultures to show that the chromatin structure is disrupted in a region that spans bp -600 to -1800 relative to the transcriptional start site. Across this region, there is a loss of canonical nucleosomes and a reduction in histone DNA cross-linking, as monitored by chromatin immunoprecipitation. The ATPase Snf2 is required for these alterations, but the histone acetyltransferase Gcn5 is not. This suggests that the SWI/SNF complex is directly involved in nucleosome removal at HO. We also present evidence indicating that the histone chaperone Asf1 assists in this. These observations suggest that SWI/SNF-related complexes in concert with histone chaperones act to remove histone octamers from DNA during the course of gene regulation. [ABSTRACT FROM AUTHOR]

Focuses on the generation of superhelical torsion by ATP-dependent chromatin remodeling activities. Alteration of chromatin structure during gene regulation; Ability to distort DNA shared by the yeast SWI/SNF complex; Biochemical activity shared by all Snf2p-related ATPase motors.

Tumor recurrence is now the leading cause of breast cancer-related death. These recurrences are believed to arise from residual cancer stem cells that survive initial therapeutic intervention. Therefore, a comprehensive understanding of cancer stem cell biology is needed to generate more effective therapies. Here we investigate the association between dysregulation of lipid metabolism and breast cancer stem cells. Focusing specifically on lipid droplets, we found that the lipid droplet number correlates with stemness in a panel of breast cell lines. Using a flow cytometry-based method developed for this study, we establish a means to isolate cells with augmented lipid droplet loads from total populations and show that they are enriched in cancer stem cells. Furthermore, pharmacological targeting of fatty acid metabolism reveals a metabolic addiction in a subset of cell lines. Our results highlight a key role for the lipid metabolism in the maintenance of the breast cancer stem cell pool, and as such, suggest it as a potential therapeutic target. [ABSTRACT FROM AUTHOR]

Targeting aromatase deprives ER + breast cancers of estrogens and is an effective therapeutic approach for these tumors. However, drug resistance is an unmet clinical need. Lipidomic analysis of long-term estrogen-deprived (LTED) ER + breast cancer cells, a model of aromatase inhibitor resistance, revealed enhanced intracellular lipid storage. Functional metabolic analysis showed that lipid droplets together with peroxisomes, which we showed to be enriched and active in the LTED cells, controlled redox homeostasis and conferred metabolic adaptability to the resistant tumors. This reprogramming was controlled by acetyl-CoA-carboxylase-1 (ACC1), whose targeting selectively impaired LTED survival. However, the addition of branched- and very long-chain fatty acids reverted ACC1 inhibition, a process that was mediated by peroxisome function and redox homeostasis. The therapeutic relevance of these findings was validated in aromatase inhibitor-treated patient-derived samples. Last, targeting ACC1 reduced tumor growth of resistant patient-derived xenografts, thus identifying a targetable hub to combat the acquisition of estrogen independence in ER + breast cancers.

Cancers feature substantial intratumoral heterogeneity of genetic and phenotypically distinct lineages. Although interactions between coexisting lineages are emerging as a potential contributor to tumor evolution, the extent and nature of these interactions remain largely unknown. We postulated that tumors develop ecological interactions that sustain diversity and facilitate metastasis. Using a combination of fluorescent barcoding, mathematical modeling, metabolic analysis, and in vivo models, we show that the Allee effect, i.e., growth dependency on population size, is a feature of tumor lineages and that cooperative ecological interactions between lineages alleviate the Allee barriers to growth in a model of triple-negative breast cancer. Soluble metabolite exchange formed the basis for these cooperative interactions and catalyzed the establishment of a polyclonal community that displayed enhanced metastatic dissemination and outgrowth in xenograft models. Our results highlight interclonal metabolite exchange as a key modulator of tumor ecology and a contributing factor to overcoming Allee effect-associated growth barriers to metastasis.

Next-generation Trop-2-targeted therapy against advanced cancers is hampered by expression of Trop-2 in normal tissues. We discovered that Trop-2 undergoes proteolytic activation by ADAM10 in cancer cells, leading to the exposure of a previously inaccessible protein groove flanked by two N-glycosylation sites. We designed a recognition strategy for this region, to drive selective cancer vulnerability in patients. Most undiscriminating anti-Trop-2 mAbs recognize a single immunodominant epitope. Hence, we removed it by deletion mutagenesis. Cancer-specific, glycosylation-prone mAbs were selected by ELISA, bio-layer interferometry, flow cytometry, confocal microscopy for differential binding to cleaved/activated, wild-type and glycosylation site-mutagenized Trop-2. The resulting 2G10 mAb family binds Trop-2-expressing cancer cells, but not Trop-2 on normal cells. We humanized 2G10 by state-of-the-art complementarity determining region grafting/re-modeling, yielding Hu2G10. This antibody binds cancer-specific, cleaved/activated Trop-2 with Kd < 10-12 mol/L, and uncleaved/wtTrop-2 in normal cells with Kd 3.16×10-8 mol/L, thus promising an unprecedented therapeutic index in patients. In vivo, Hu2G10 ablates growth of Trop-2-expressing breast, colon, prostate cancers, but shows no evidence of systemic toxicity, paving the way for a paradigm shift in Trop-2-targeted therapy., (©2023 American Association for Cancer Research.)

Tumor recurrence is now the leading cause of breast cancer-related death. These recurrences are believed to arise from residual cancer stem cells that survive initial therapeutic intervention. Therefore, a comprehensive understanding of cancer stem cell biology is needed to generate more effective therapies. Here we investigate the association between dysregulation of lipid metabolism and breast cancer stem cells. Focusing specifically on lipid droplets, we found that the lipid droplet number correlates with stemness in a panel of breast cell lines. Using a flow cytometry-based method developed for this study, we establish a means to isolate cells with augmented lipid droplet loads from total populations and show that they are enriched in cancer stem cells. Furthermore, pharmacological targeting of fatty acid metabolism reveals a metabolic addiction in a subset of cell lines. Our results highlight a key role for the lipid metabolism in the maintenance of the breast cancer stem cell pool, and as such, suggest it as a potential therapeutic target.

Background: DNA vaccines provide high tolerability and safety but commonly suffer from suboptimal immunogenicity. We previously reported that a plasmid vector (pATRex), encoding the DNA sequence for the von Willebrand I/A domain of the tumor endothelial marker-8 (TEM8) when given in combination with plasmid-encoded tumor antigens acted as a powerful molecular adjuvant enhancing immunity against breast and melanoma tumors., Aims: In the present study we addressed two unsolved issues; would the adjuvant action of pATRex extend to a DNA vaccine against infectious disease and, if so, what is the mechanistic basis for pATRex adjuvant action?, Results: Here we show in a murine malaria vaccine model that co-administration of pATRex potentiates antibody production elicited by an intramuscular injection of plasmid encoding Plasmodium yoelii merozoite surface protein 4/5 (PyMSP4/5). pATRex enhanced the B-cell response and induced increased IgG1 production consistent with TH2 polarization of the DNA vaccine response. To explore the mechanism of adjuvant action, cells were transfected in vitro with pATRex and this resulted in formation of insoluble intracellular aggregates and apoptotic cell death. Using a structural modeling approach we identified a short peptide sequence (α3-β4) within ATRex responsible for protein aggregation and confirmed that transfection of cells with plasmid encoding this self-assembling peptide similarly triggered intracellular aggregates, caspase activation and cell death., Conclusion: Plasmids encoding aggregation-promoting domains induce formation of insoluble intracellular aggregates that trigger caspase activation and apoptotic cell death leading to activation of the innate immune system thereby acting as genetic adjuvants.

Nuclear receptors, including the androgen receptor (AR), regulate target cell transcription through interaction with auxiliary proteins to modify chromatin structure. We describe herein a novel AR-interacting protein, termed ARIP4, that has structural features typical of the SNF2-like protein family. With regard to the Snf2 domain, the closest homolog of ARIP4 is the ATRX protein. ARIP4 is a nuclear protein and comprises 1466 amino acids. It interacts with AR in vitro and in cultured yeast and mammalian cells. ARIP4 can be labeled with 8-azido-[gamma-32P]ATP and exhibits DNA-dependent ATPase activity. Like several ATP-dependent chromatin remodeling proteins, ARIP4 generates superhelical torsion within linear DNA fragments in an ATP-dependent manner. With a stably integrated target promoter, ARIP4 elicits a modest enhancement of AR-dependent transactivation. In transient cotransfection assays, ARIP4 modulates AR function in a promoter-dependent manner; it enhances receptor activity on minimal promoters, but does not activate more complex promoters. ARIP4 mutants devoid of ATPase activity fail to alter DNA topology and behave as trans-dominant negative regulators of AR function in transient assays.