TY - JOUR T1 - Ecological interactions in breast cancer: Cell facilitation promotes growth and survival under drug pressure JF - bioRxiv DO - 10.1101/2021.02.01.429214 SP - 2021.02.01.429214 AU - Rena Emond AU - Jason I. Griffiths AU - Vince Kornél Grolmusz AU - Aritro Nath AU - Jinfeng Chen AU - Eric F. Medina AU - Rachel S. Sousa AU - Frederick R. Adler AU - Andrea H. Bild Y1 - 2022/01/01 UR - http://biorxiv.org/content/early/2022/09/28/2021.02.01.429214.abstract N2 - The interplay of positive and negative interactions between drug sensitive and resistant cells influences the effectiveness of treatment in heterogeneous cancer cell populations. In a study of isogenic estrogen receptor positive (ER+) breast cancer cell lineages sensitive and resistant to ribociclib-induced CDK4/6 inhibition in mono- and co-culture, we find that sensitive cells grow and compete more effectively in the absence of treatment. During treatment with ribociclib, sensitive cells survive and proliferate better when grown together with resistant cells than when grown in monoculture, termed facilitation in ecology. Both liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays and single cell RNA-sequencing (scRNAseq) indicate that resistant cell production of estradiol, a highly active estrogen metabolite, is the mechanism of facilitation. Higher estradiol production by resistant cells drives a shift in sensitive cell phenotype to a resistant cell state in coculture. Adding estradiol in monoculture provides sensitive cells with increased resistance to therapy, and cancels facilitation in coculture. Mathematical modeling quantifies the strength of competition and facilitation and predicts that blocking facilitation has the potential to control both resistant and sensitive cell populations and inhibit the emergence of a refractory population.Competing Interest StatementThe authors have declared no competing interest. ER -