Brezin, L. | bioRxiv Science

bioRxiv2026

Dynamic flux balance analysis of cancer metabolism using expression-based human cell line models

Aberrant metabolism that supports dysregulated growth is a key feature of cancer. Flux balance analysis, a computational approach that can predict genome-scale metabolic rates based on stoichiometry and mass conservation, has proven valuable in the prediction of pathway utilization and possible drug targets in cancer cells, but deep insight into growth dynamics under physiologically relevant conditions has been limited. To address this gap, we revisited the human metabolism model and its integration of gene-expression data, and we implemented simulations of metabolism in multiple cancer cell lines using static and dynamic flux balance analysis. Our models predict a substantial dependence of intracellular and exchange fluxes, and of the timing of resource utilization, on growth media and specific cell-line makeup. Secretions include lactate and other metabolites that could contribute to shaping the tumor microenvironment. Despite these differences in flux phenotypes, virtual genetic knockout screens predict high similarity of lethality across cell lines and media, and suggest a handful of possible cell-line specific targets. We finally demonstrate the power of dynamic simulations by setting virtual competition assays, which form the foundation for future extensions into dynamic simulations of tumor-stromal interactions in spatially-structured environment.

systems biology↗

bioRxiv2021

Crisscross multilayering of cell sheets

Simple hydrostatic skeletons such as the Hydras consist of two stacked layers of cells perpendicularly oriented. Although this crisscross architecture can be recapitulated in vitro, little is known on the formation of such multilayers starting from a monolayer. In the present article, we show that bilayering of myoblasts results from the organization and activity of the cells originally in the monolayer which can be described as a contractile active nematic. As expected, most of the +1/2 topological defects that are associated with this nematic order self-propel. However, a subpopulation of these defects remains immobile. Perpendicular bilayering occurs exclusively at these motionless defects. Indeed, cells located at the head of these defects converge toward the (immobile) core and accumulate there until they start migrating on top of the tail of the first layer while the tail cells migrate in the opposite direction under the head cells. Since the cells keep their initial orientations, the two stacked layers end up perpendicularly oriented. This concerted process leading to a bilayer is dependent on the apical secretion of Extra Cellular Matrix (ECM) by the cells. Indeed, we evidence the presence of ECM between the cell layers and at the apical surface of the topmost layer. ECM molecules are oriented in the direction of the cells that produce them, which may guide the migration of the subsequent cell layers on their apical side. Significance StatementHydrostatic skeletons such as that of the Hydra consist of two stacked layers of cells perpendicularly oriented whose coordinated contraction allows for complex movements. Such crisscross organization is also observed with myoblasts in culture. Confluent monolayers organize in well-aligned domains between which topological defects position themselves. Although these singularities are generally self-propelled, a fraction of them remains motionless. Perpendicular bilayering occurs exclusively at these particular pinned defects. Cells first accumulate at the head of the defects until they split in two perpendicular layers migrating in an antiparallel way on top of each other. Such a concerted process is highly dependent on the precise organization of the cell-secreted Extra Cellular Matrix (ECM).

biophysics↗