Tunnelling nanotube-like intercellular projections are druggable mediators of cancer-niche crosstalk

Intercellular connections (ICCs) used by cancer cells to interact with their microenvironment have remained underexplored. Here, we develop 3D co-culture organoids to investigate the role of ICCs in drug resistance. We create an animal-component-free bone marrow-mimicking Vitronectin–Alginate–Laminin (VAL) hydrogel, which exhibits viscoelastic properties representative of the human bone marrow (BM). VAL hydrogels support the culture of mesenchymal stroma cells (MSCs), the engraftment and expansion of patient-derived acute lymphoblastic leukaemia (ALL) cells, and consequently form 3D co-culture organoids. We find that ALL therapies, such as dexamethasone and BCL2 inhibition (using ABT-199), or their combination, induce the formation of tunnelling nanotube (TNT)-like projections between ALL cells and MSCs. These TNT-like protrusions are absent in the presence of the N-cadherin antagonist ADH-1. Ultimately, we reveal a triple drug combination of dexamethasone, ABT-199 and ADH-1 to be efficacious in killing ALL cells. The dexamethasone-ABT-199-ADH-1 combination shows high efficacy in different high-risk patient-derived xenograft-ALL samples. In summary, we present ALL-BM-tissue-like organoids and use them to provide insights into disrupting cancer-MSC TNT-like ICCs to enhance drug efficacy.