Hazel M. Quinn

Supplementary Figure 3 from LOX Inhibition Disrupts a Collagen–Integrin–MYC Axis to Suppress Progression of Invasive Lobular Carcinoma

Supplementary Figure 1 from LOX Inhibition Disrupts a Collagen–Integrin–MYC Axis to Suppress Progression of Invasive Lobular Carcinoma

Invasive lobular carcinoma (ILC) accounts for 15% of breast cancers yet lacks specific therapy because ILCs are underrepresented in clinical trials and preclinical models are lacking. In this study, we established intraductal xenograft models to test whether the clinical pan-lysyl-oxidase inhibitor PXS-5505, now in phase I/IIa trials for myelofibrosis, can exploit the collagen-rich matrix dependency in ILC created by CDH1 loss. PXS-5505 remodeled fibrillar collagen and halted tumor expansion and metastatic seeding across estrogen receptor–positive and triple-negative models without systemic toxicity. Genome-wide CRISPR screens revealed ITGAV and ITGB5 as synthetic lethal partners of CDH1, and LOX inhibition downregulated their expression, together with MYC, NF-κB, and AP-1 transcriptional programs. Collagen fiber density/alignment and MYC/AP-1 gene signatures served as pharmacodynamic readouts of drug activity. These data uncover a tractable extracellular matrix–integrin–MYC axis in ILC and nominate PXS-5505, alone or with endocrine therapy, for window-of-opportunity trials in this understudied breast cancer subtype. Significance: A clinical stage LOX inhibitor slows tumor progression and alters multiple molecular endpoints in invasive lobular carcinoma, providing a translatable therapeutic strategy for this frequent breast cancer subtype currently lacking specific therapies.

Summary: More than two‐thirds of cancer‐related deaths are attributable to metastases. In some tumor types metastasis can occur up to 20 years after diagnosis and successful treatment of the primary tumor, a phenomenon termed late recurrence. Metastases arise from disseminated tumor cells (DTCs) that leave the primary tumor early on in tumor development, either as single cells or clusters, adapt to new environments, and reduce or shut down their proliferation entering a state of dormancy for prolonged periods of time. Dormancy has been difficult to track clinically and study experimentally. Recent advances in technology and disease modeling have provided new insights into the molecular mechanisms orchestrating dormancy and the switch to a proliferative state. A new role for epithelial‐mesenchymal transition (EMT) in inducing plasticity and maintaining a dormant state in several cancer models has been revealed. In this review, we summarize the major findings linking EMT to dormancy control and highlight the importance of pre‐clinical models and tumor/tissue context when designing studies. Understanding of the cellular and molecular mechanisms controlling dormant DTCs is pivotal in developing new therapeutic agents that prevent distant recurrence by maintaining a dormant state.

Targeting cancer stem cells (CSC) can serve as an effective approach toward limiting resistance to therapies. While basal-like (triple-negative) breast cancers encompass cells with CSC features, rational therapies remain poorly established. We show here that the receptor tyrosine kinase Met promotes YAP activity in basal-like breast cancer and find enhanced YAP activity within the CSC population. Interfering with YAP activity delayed basal-like cancer formation, prevented luminal to basal transdifferentiation, and reduced CSC. YAP knockout mammary glands revealed a decrease in β-catenin target genes, suggesting that YAP is required for nuclear β-catenin activity. Mechanistically, nuclear YAP interacted with β-catenin and TEAD4 at gene regulatory elements. Proteomic patient data revealed an upregulation of the YAP signature in basal-like breast cancers. Our findings demonstrate that in basal-like breast cancers, β-catenin activity is dependent on YAP signaling and controls the CSC program. These findings suggest that targeting the YAP/TEAD4/β-catenin complex offers a potential therapeutic strategy for eradicating CSCs in basal-like breast cancers.Significance:These findings show that YAP cooperates with β-catenin in basal-like breast cancer to regulate CSCs and that targeting this interaction may be a novel CSC therapy for patients with basal-like breast cancer.