In vivo expansion of a CD9+ decidual-like NK cell subset following autologous hematopoietic stem cell transplantation.

Autologous hematopoietic stem cell transplantation (autoHSCT) is a treatment option for hematological disorders and pediatric solid tumors. After an autoHSCT, natural killer (NK) cells are the first lymphocyte subset returning to normal levels. To uncover global changes during NK cell reconstitution after autoHSCT, we performed RNA-sequencing on NK cells before and after autoHSCT. Results showed profound changes in the gene expression profile of NK cells immediately after autoHSCT. Several biological processes including cell cycle, DNA replication and the mevalonate pathway were enriched. Significantly, we observed that following autoHSCT, NK cells acquired a decidual-like gene expression profile, including the expression of CD9. By using multiparametric flow cytometry, we confirmed the expansion of NK cells expressing CD9 immediately after autoHSCT, which exhibited higher granzyme B and perforin expression levels than CD9- NK cells. These results provide insights into the physiopathology of NK cells during their reconstitution after autoHSCT.Supported by the following grants: AECC-Spanish Association Against Cancer (PROYE16074- BORR) and Health Department, Basque Government (2021333006). GA-P is the recipient of a predoctoral contract funded by AECC-Spanish Association Against Cancer (PRDVZ21440ASTA). DP-A is a recipient of a fellowship from the AECC-Spanish Association Against Cancer (PPLAB212164POLA), AA-I and GA-P are recipient of a fellowship from the Jesús de Gangoiti Barrera Foundation (FJGB20/007, FJGB21/001 and FJBG21/005). IT is recipient of a predoctoral contract funded by the Department of Education, Basque Government (PRE_2021_2_0215). OZ is the recipient of a postdoctoral contract funded by ‘‘Instituto de Salud Carlos III-Contratos Sara Borrell 2017 (CD17/00128)’’ and the European Social Fund (ESF)-The ESF invests in your future. FB is an Ikerbasque Research Professor, Ikerbasque, Basque Foundation for Science.S

IL-12/15/18-induced cell death and mitochondrial dynamics of human NK cells

Natural killer (NK) cells are lymphocytes with potent antitumor functions and, consequently, several NK cell-based strategies have been developed for cancer immunotherapy. A remarkable therapeutic approach is the adoptive transfer of NK cells stimulated with IL-12, IL-15 and IL-18. This cytokine stimulation endows NK cells with properties that resemble immunological memory and, for this reason, they are known as cytokine-induced memory-like (CIML) NK cells. Very promising results have been reported in clinical trials and yet, there are still unknown aspects of CIML NK cells. Here, we have conducted a preliminary study of their mitochondrial dynamics. Our results show that upon IL-12/15/18 stimulation the viability of NK cells decreased and an increment in mitochondrial superoxide levels was observed. In addition, we found that mitochondria appeared slightly elongated and their cristae density decreased following IL-12/15/18 stimulation, possibly in a process mediated by the low levels of optic atrophy type 1 (OPA1) protein. Interestingly, although mitophagy was slightly impaired, an increase in autophagic flux was observed, which might explain the reduced viability and the accumulation of unfit mitochondria. Our findings could be of relevance in order to design new strategies intended to improve the mitochondrial fitness of IL-12/15/18-stimulated NK cells with the aim of improving their therapeutic efficacy