Abstract 2449: Superoxide regulates protumoral p16-driven senescence in the bone marrow microenvironment of acute myeloid leukemia
Authors: Hellmich Charlotte , Abdul-Aziz Amina , Marlein Christopher , Sun Yu , Shafat Manar , Collins Angela , Piddock Rachel , Campisi Judith , Bowles Kristian , Rushworth Stuart 
Published: August 2018

Abstract
Acute myeloid leukemia (AML) is primarily a disease of the elderly and depends on the bone marrow microenvironment. The aging bone marrow accumulates senescent cells, characterized by an irreversible arrest of cell proliferation and the secretion of numerous pro-inflammatory cytokines, chemokines and growth factors, termed the secretary associated senescence profile (SASP). Previously we showed that AML is capable of reprogramming bone marrow stromal cells (BMSC) and induces oxidative stress in the BMSC (via superoxide) to support blast survival and proliferation. Here, we hypothesize that AML derived superoxide induces a senescent aging phenotype in the BMSC, generating a SASP in the BMSC which then feed back to promote AML blast proliferation in the bone marrow niche. We isolated primary AML cells and BMSCs from the bone marrow of patients attending our clinic. To assess senescence of BMSC we measured p16 mRNA and protein levels and senescence associated β-Galactosidase activity. Primary AML was engrafted into NSG mice and CD105+ / CD45- cells (BMSC) were sorted and analysed for SASP. We transplanted syngeneic AML blasts (generated from lineage negative cells transduced with the oncogene MN1) into p16-3MR, WT C57Bl/6 and NOX2 (CYBB) deficient mice. Patient samples were taken in accordance with the Declaration of Helsinki and animal studies performed under approval of the UK Home Office. We report that human AML cells induce SASP in vivo as measured by RT-PCR of sorted BMSC cells from NSG mice engrafted with human AML. Next, we engrafted p16-3MR mice with MN1 cells and flow cytometry analysis of isolated BSMC (CD105+ CD45-) showed AML cells induce micro-environment senescence in vivo. Furthermore, depletion of p16 positive stromal cells through treating MN1 engrafted p16-3MR animals with ganciclovir significantly increased survival of MN1 engrafted mice compared with animals treated with vehicle control. In addition, we show that MN1 AML cells, transplanted into NOX2 deficient mice, generate high levels of superoxide in the bone marrow, which results in oxidative stress in the BMSC. Finally NOX2-KD in MN1 AML reduces BMSC senescence in the BM of p16-3MR recipient mice and results in improved animal survival. Here we show that the AML derived superoxide induces a senescent phenotype in the bone marrow micro-environment which then feeds back to enhance the growth capacity of AML. Targeting the senescent microenvironment may therefore provide novel therapeutic approaches for the treatment of this disease in the future.
Citation Format: Charlotte Hellmich, Amina Abdul-Aziz, Christopher Marlein, Yu Sun, Manar Shafat, Angela Collins, Rachel Piddock, Judith Campisi, Kristian Bowles, Stuart Rushworth. Superoxide regulates protumoral p16-driven senescence in the bone marrow microenvironment of acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2449.