Stromal cell protein kinase C-beta inhibition enhances chemosensitivity in B cell malignancies and overcomes drug resistance

Park, E., Chen, J., Moore, A., Mangolini, M., Santoro, A., Boyd, J. R., Schjerven, H., Ecker, V., Buchner, M., Williamson, J. C., Lehner, P. J., Gasparoli, L., Williams, O., Bloehdorn, J., Stilgenbauer, S., Leitges, M., Egle, A., Schmidt-Supprian, M., Frietze, S., Ringshausen, I. (2020). Sci Transl Med 12.

DOI:10.1126/scitranslmed.aax9340(link is external)


Overcoming drug resistance remains a key challenge to cure patients with acute and chronic B cell malignancies. Here, we describe a stromal cell–autonomous signaling pathway, which contributes to drug resistance of malignant B cells. We show that protein kinase C (PKC)–β–dependent signals from bone marrow–derived stromal cells markedly decrease the efficacy of cytotoxic therapies. Conversely, small-molecule PKC-β inhibitors antagonize prosurvival signals from stromal cells and sensitize tumor cells to targeted and nontargeted chemotherapy, resulting in enhanced cytotoxicity and prolonged survival in vivo. Mechanistically, stromal PKC-β controls the expression of adhesion and matrix proteins, required for activation of phosphoinositide 3-kinases (PI3Ks) and the extracellular signal–regulated kinase (ERK)–mediated stabilization of B cell lymphoma–extra large (BCL-XL) in tumor cells. Central to the stroma-mediated drug resistance is the PKC-β–dependent activation of transcription factor EB, regulating lysosome biogenesis and plasma membrane integrity. Stroma-directed therapies, enabled by direct inhibition of PKC-β, enhance the effectiveness of many antileukemic therapies.