Biology subjects

Levchenko, A.

Publications and source records attributed to Levchenko, A..

3 recordsLinked to original sources

bioRxiv2019

Pericytes enable effective angiogenesis in the presence of pro inflammatory signals

Angiogenesis frequently occurs in the context of acute or persistent inflammation. The complex interplay of pro-inflammatory and pro-angiogenic cues is only partially understood. Using a new experimental model permitting exposure of developing blood vessel sprouts to multiple combinations of diverse biochemical stimuli and juxtacrine cell interactions, we present evidence that a pro-inflammatory cytokine, tumor necrosis factor (TNF), can have both pro- and anti-angiogenic effects, depending on the dose and the presence of pericytes. In particular, we find that pericytes can rescue and enhance angiogenesis in the presence of otherwise inhibitory high TNF doses. This sharp switch from pro- to anti-angiogenic effect of TNF observed with an escalating dose of this cytokine, as well as the effect of pericytes are explained by a mathematical model trained on the biochemical data. Furthermore, this model was predictive of the effects of diverse combinations of pro-and anti-inflammatory cues, and variable pericyte coverage. The mechanism supports the effect of TNF and pericytes as modulating signaling networks impinging in Notch signaling and specification of the Tip and Stalk phenotypes. This integrative analysis elucidates the plasticity of the angiogenic morphogenesis in the presence of diverse and potentially conflicting cues, with immediate implications for many physiological and pathological settings.

developmental biology↗

bioRxiv2019

YAP controls cell migration and invasion through a Rho-GTPase switch

Delineating the mechanisms controlling the invasive spread of non-diseased and transformed cells is central to understanding diverse processes including cancer progression. Here, we found that Yes-associated protein (YAP), a central transcriptional regulator implicated in controlling organ and body size, modulated a Rho-GTPase switch that drives cellular migration by transactivating the Rac1-GEF protein TRIO through direct modulation of its intronic enhancer. Additionally, YAP and TRIO may promote invasive behavior through putative crosstalk with STAT3 signaling, a potential downstream target. Although we found this YAP-dependent infiltrative program in many cell types, it was particularly enhanced in a patient-specific manner in the most common malignant brain tumor, glioblastoma (GBM), where hyperactivation of the YAP, TRIO, and STAT3 signatures also conferred poor clinical outcome. Our analysis suggests that the YAP-TRIO-Rho-GTPase signaling network identified in this study is a ubiquitous regulator of invasive cell spread in both physiological and pathological contexts.

cancer biology↗

bioRxiv2019

The Evolution of Placental Invasion and Cancer Metastasis are Causally Linked

Among mammals, the extent of placental invasion is correlated with vulnerability to malignancy. Animals with more invasive placentation (e.g. humans) are more vulnerable to malignancy, whereas animals with a non-invasive placenta (e.g. ruminants) are less likely to develop malignant cancer. To explain this correlation, we propose the hypothesis of Evolved Levels of Invasibility (ELI) positing that the permissiveness of stromal tissue to invasion is a unitary character affecting both placental and cancer invasion. We provide evidence for this hypothesis by contrasting invasion of human and bovine cancer and placental cells into a lawn of stromal cells from different species. We find that both bovine endometrial and skin fibroblasts are more resistant to invasion of placental and cancer cells than their human counterparts. Gene expression profiling identified genes with high expression in human but not bovine fibroblasts. Knocking down of a subset of them in human fibroblasts leads to significantly stronger resistance to cancer cell invasion. Comparative analysis of gene expression among mammals suggests that humans evolved higher vulnerability to malignancy than the eutherian ancestor, possibly as a correlate of more invasive placentation, and boroeutherians evolved to decrease stromal invasibility. Identifying the evolutionary determinants of stromal invasibility can provide significant insights to develop rational anti-metastatic therapeutics.

cancer biology↗