RB1 deficiency defines an aggressive tumor state with limited therapeutic options. Osteosarcoma represents a clinically relevant model of RB1 deficient malignancy, as RB1 alterations are among the most frequent genomic events in this tumor type. However, the non cell cycle vulnerabilities created by RB1 loss remain incompletely understood. We therefore used osteosarcoma to identify therapeutic dependencies associated with RB1 deficiency. Through high-throughput compound screening, we identified a selective vulnerability of RB1-deficient tumor cells to VCP inhibition. NMS-873 and other VCP-targeting compounds preferentially suppressed RB1 deficient cells across two-dimensional cultures, three-dimensional spheroids, patient-derived organoids, and in vivo tumor models. Mechanistically, VCP inhibition exacerbated proteostasis stress and activated endoplasmic reticulum stress responses in RB1-deficient cells. We further found that VCP function was regulated by glutamine-dependent acetylation, with lysine 615 serving as a dominant acetylation site that modulated sensitivity to VCP inhibition. Glutamine restriction phenocopied, whereas glutamine supplementation partially rescued, the effects of NMS-873 on VCP acetylation and tumor cell growth. Clinical and transcriptomic analyses further linked VCP expression and protein-folding stress programs to aggressive disease features. Together, these findings identify glutamine regulated VCP acetylation as a metabolic proteostasis dependency in RB1-deficient tumors and nominate VCP inhibition as a therapeutic strategy for this difficult-to-target tumor state.
Bing-Hui Yang, Ying Cao, Yi-Ning Tao et al.· bioRxiv· 0 citations
Background: Human epidermal growth factor receptor 2 (HER2)-positive breast cancer exhibits high metastatic potential, linked not only to intrinsic cancer cell traits but also to critical crosstalk with the tumor microenvironment. However, the coevolutionary mechanisms between cancer cells and multiple stromal subpopulations in driving distant metastasis remain poorly understood. Therefore, this study aimed to explore the microenvironmental regulatory mechanisms of breast tumor-initiating cells and their roles in HER2-positive breast cancer metastasis. Methods: Integrated multi-omics analyses (spatial transcriptomics, metabolomics, spatial in situ analysis, and proteomics) were used to identify novel cell subpopulations and their interactions. High-throughput sequencing of exosomal microRNAs (miRNAs) and single-nucleus RNA from the same tissue was performed to explore the molecular mechanisms underlying cell crosstalk. In vitro experiments were conducted to verify the interaction between stromal cells and prominin 1 (PROM1)+ SMAD family member 5 (SMAD5)+ cells. In vivo murine breast cancer models were established to confirm the role of stromal subpopulations in pulmonary metastasis, and parabiosis assays were carried out to compare key cell subpopulations between tumor-bearing mice and normal mice. Clinical samples were analyzed to correlate key cell subpopulations with clinicopathological features and prognosis. Results: A breast tumor-initiating subpopulation, PROM1+ SMAD5+ cells, and its interactions with stromal cells, specifically adiponectin (ADIPOQ)+ notch receptor 4 (NOTCH4)+ adipocytes and decorin (DCN)+ transmembrane 4 L six family member 1 (TM4SF1)+ fibroblasts, were identified by integrated multi-omics analyses. Mechanistically, these 2 stromal subpopulations delivered functional miRNAs and mediated coatomer protein complex subunit alpha (COPA)-dependent epidermal growth factor receptor (EGFR) activation in PROM1+SMAD5+ cells, thereby triggering the EGFR–SMAD5–cytochrome P450 family 3 subfamily A member 4 (CYP3A4) axis to induce partial epithelial–mesenchymal transition (pEMT) and metastasis. Additionally, stroma-secreted exosomal miR-671-3p down-regulated Claudin1 in PROM1+SMAD5+ cells, promoting their evolution into PROM1+SMAD5+Claudin1− subpopulations with enhanced stemness and metastatic potential. In vivo experiments confirmed that the 2 stromal subpopulations markedly promoted pulmonary metastasis, and the 3 identified subpopulations preferentially accumulated in the primary tumors, lymph nodes, and pulmonary metastatic lesions of tumor-bearing mice. Clinically, these 3 subpopulations form a “trinity niche”, whose aggregation associated with HER2 positivity, high malignancy, and lymph node/pulmonary metastasis, and predicted poor prognosis. Conclusion: This study clarified the microenvironmental regulation of breast tumor-initiating cells and provided new insights into precision therapy.
Huijing Yin, Wei Wang, Jing Ge et al.· Cancer Communications· 0 citations
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