Authors: Daehong Kim, Giljun Park, Jani Huuhtanen, Sofie Lundgren, Rajiv K. Khajuria, Ana M. Hurtado, Cecilia Muñoz-Calleja, Laura Cardeñoso, Valle Gómez-García de Soria, Tzu Hua Chen-Liang, Samuli Eldfors, Pekka Ellonen, Sari Hannula, Matti Kankainen, Oscar Bruck, Anna Kreutzman, Urpu Salmenniemi, Tapio Lönnberg, Andrés Jerez, Maija Itälä-Remes, Mikko Myllymäki, Mikko A. I. Keränen, Satu Mustjoki
Summary: Graft versus host disease (GvHD) is the main complication of allogeneic hematopoietic stem cell transplantation (HSCT). Here we report studies of a patient with chronic GvHD (cGvHD) carrying persistent CD4+ T cell clonal expansion harboring somatic mTOR, NFKB2, and TLR2 mutations. In the screening cohort (n = 134), we detect the mTOR P2229R kinase domain mutation in two additional cGvHD patients, but not in healthy or HSCT patients without cGvHD. Functional analyses of the mTOR mutation indicate a gain-of-function alteration and activation of both mTORC1 and mTORC2 signaling pathways, leading to increased cell proliferation and decreased apoptosis. Single-cell RNA sequencing and real-time impedance measurements support increased cytotoxicity of mutated CD4+ T cells. High throughput drug-sensitivity testing suggests that mutations induce resistance to mTOR inhibitors, but increase sensitivity for HSP90 inhibitors. Our findings imply that somatic mutations may contribute to aberrant T cell proliferations and persistent immune activation in cGvHD, thereby paving the way for targeted therapies.
Source: Nature Communications, 2020; 11 (1)