Vadim Backman

Leveraging chromatin packing domains to target chemoevasion in vivo

Cancer cells exhibit a remarkable resilience to cytotoxic stress, often adapting through transcriptional changes linked to alterations in chromatin structure. In several types of cancer, these adaptations involve epigenetic modifications and restructuring of topologically associating domains. However, the underlying principles by which chromatin architecture facilitates such adaptability across different cancers remain poorly understood. To investigate the role of chromatin in this process, we developed a physics-based model that connects chromatin organization to cell fate decisions, such as survival following chemotherapy. Our model builds on the observation that chromatin forms packing domains, which influence transcriptional activity through macromolecular crowding. The model accurately predicts chemoevasion in vitro, suggesting that changes in packing domains affect the likelihood of survival. Consistent results across diverse cancer types indicate that the model captures fundamental principles of chromatin-mediated adaptation, independent of the specific cancer or chemotherapy mechanisms involved. Based on these insights, we hypothesized that compounds capable of modulating packing domains, termed Transcriptional Plasticity Regulators (TPRs), could prevent cellular adaptation to chemotherapy. We conducted a proof-of-concept compound screen using live-cell chromatin imaging to identify several TPRs that synergistically enhanced chemotherapy-induced cell death. The most effective TPR significantly improved therapeutic outcomes in a patient-derived xenograft model of ovarian cancer. These findings underscore the central role of chromatin in cellular adaptation to cytotoxic stress and present a framework for enhancing cancer therapies, with broad potential across multiple cancer types.

Chromatin Organization Governs Transcriptional Response and Plasticity of Cancer Stem Cells

Abstract Chromatin organization regulates transcription to influence cellular plasticity and cell fate. We explored whether chromatin nanoscale packing domains are involved in stemness and response to chemotherapy. Using an optical spectroscopic nanosensing technology we show that ovarian cancer‐derived cancer stem cells (CSCs) display upregulation of nanoscale chromatin packing domains compared to non‐CSCs. Cleavage under targets and tagmentation (CUT&Tag) sequencing with antibodies for repressive H3K27me3 and active H3K4me3 and H3K27ac marks mapped chromatin regions associated with differentially expressed genes. More poised genes marked by both H3K4me3 and H3K27me3 were identified in CSCs vs. non‐CSCs, supporting increased transcriptional plasticity of CSCs. Pathways related to Wnt signaling and cytokine‐cytokine receptor interaction were repressed in non‐CSCs, while retinol metabolism and antioxidant response were activated in CSCs. Comparative transcriptomic analyses showed higher intercellular transcriptional heterogeneity at baseline in CSCs. In response to cisplatin, genes with low baseline expression levels underwent the highest upregulation in CSCs, demonstrating transcriptional plasticity under stress. Epigenome targeting drugs downregulated chromatin packing domains and promoted cellular differentiation. A disruptor of telomeric silencing 1‐like (Dot1L) inhibitor blocked transcriptional plasticity, reversing stemness. These findings support that CSCs harbor upregulated chromatin packing domains, contributing to transcriptional and cell plasticity that epigenome modifiers can target.