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Although extramedullary manifestations (EMs) are frequent in patients with acute myeloid leukemia (AML), they are often not detected during clinical workup and neither imaging- nor molecularly based diagnostic strategies are established to reveal their existence. Still, the detection of EM is essential for therapeutic decision-making, as EM present with aggressive and resistant disease and since mutational profiling might render patients within a different risk category, requiring personalized therapeutic strategies. Here, we report the case of an AML patient presenting with AML bone marrow (BM) infiltration and molecularly distinct EM at time of diagnosis followed by multiple EM relapses while undergoing several intensive chemotherapies including allogeneic hematopoietic cell transplantations (alloHCTs). 18 Fluorodesoxy-glucose positron emission tomography ( 18 FDG-PET)-imaging revealed EM sites in the mediastinum, duodenum, skin, and in retroperitoneal tissue, whereas recurrent BM biopsies showed continuous cytomorphologic and cytogenetic remission after alloHCT. To investigate the molecular background of the aggressive character of extramedullary disease and its differential treatment response, we performed amplicon-based next generation sequencing. An exon 4 (c.497_498insGA) frameshift RUNX1 mutation was exclusively found in all of the patient’s EM sites, but not in the BM or in peripheral blood samples at time of EM reoccurrence. In addition, we detected an exon 13 (c.3306G>T) ASXL1 point mutation only in the retroperitoneal tumor tissue at the time of the fourth relapse. In contrast to the patient’s intermediate-risk BM AML at diagnosis according to ELN2017, EM sites showed molecular adverse-risk features implicating intensified strategies like cellular therapies. Notably, disease relapse could only be detected by imaging throughout the course of disease. This case demonstrates both the necessity of continuous molecular profiling of EM to reveal differential molecular composition of EM and BM-derived AML, supposedly leading to divergent susceptibility to established therapies, as well as recurrent 18 FDG-PET-imaging for detecting residual disease and assessment of treatment response in case of EM AML.

Abstract Understanding the role of neuropilin 2 (NRP2) in prostate cancer cells as well as in the bone microenvironment is pivotal in the development of an effective targeted therapy for the treatment of prostate cancer bone metastasis. We observed a significant upregulation of NRP2 in prostate cancer cells metastasized to bone. Here, we report that targeting NRP2 in cancer cells can enhance taxane-based chemotherapy with a better therapeutic outcome in bone metastasis, implicating NRP2 as a promising therapeutic target. Since, osteoclasts present in the tumor microenvironment express NRP2, we have investigated the potential effect of targeting NRP2 in osteoclasts. Our results revealed NRP2 negatively regulates osteoclast differentiation and function in the presence of prostate cancer cells that promotes mixed bone lesions. Our study further delineated the molecular mechanisms by which NRP2 regulates osteoclast function. Interestingly, depletion of NRP2 in osteoclasts in vivo showed a decrease in the overall prostate tumor burden in the bone. These results therefore indicate that targeting NRP2 in prostate cancer cells as well as in the osteoclastic compartment can be beneficial in the treatment of prostate cancer bone metastasis.