Dipeptidylpeptidase 4 promotes survival and stemness of acute myeloid leukemia stem cells.

Leukemic-stem-cell-specific targeting may improve the survival of patients with acute myeloid leukemia (AML) by avoiding the ablative effects of standard regimens on normal hematopoiesis. Herein, we perform an unbiased screening of compounds targeting cell surface proteins and identify clinically used DPP4 inhibitors as strong suppressors of AML development in both murine AML models and primary human AML cells xenograft model. We find in retrovirus-induced AML mouse models that DPP4-deficient AML cell-transplanted mice exhibit delay and reversal of AML development, whereas deletion of DPP4 has no significant effect on normal hematopoiesis. DPP4 activates and sustains survival of AML stem cells that are critical for AML development in both human and animal models via binding with Src kinase and activation of nuclear factor κB (NF-κB) signaling. Thus, inhibition of DPP4 is a potential therapeutic strategy against AML development through suppression of survival and stemness of AML cells.

Occult pulmonary mucosa-associated lymphoid tissue lymphoma presenting as catastrophic antiphospholipid antibody syndrome.

Catastrophic antiphospholipid antibody syndrome (CAPS) is characterized by fulminant thrombosis of the arterial and venous beds of multiple organ systems over a relatively short period of time and with a high mortality rate. Mucosa-associated lymphoid tissue (MALT) lymphoma of the lung has never been reported as a causative or precipitating factor for CAPS in the CAPS registry database. The present study describes a rare case of pulmonary MALT lymphoma of the lung that presented as CAPS. A 19-year-old Hispanic female presented with shortness of breath and abdominal pain. Computed tomography (CT) scans of the chest and abdomen revealed multiple portal vein thromboses and bilateral pulmonary nodules. Within one week of presentation, the patient developed a straight sinus thrombosis and upper extremity deep vein thrombosis, which led to shortness of breath. A biopsy of the lung nodule revealed MALT lymphoma. The present case illustrates a rarely reported pulmonary MALT lymphoma presenting as CAPS in a young female. The patient was successfully treated with 90 mg/m2 bendamustine on days one and two and rituximab 375 mg/m2 on day one of each 28-day cycle. Complete remission of the lung nodules was observed following three cycles of treatment, as visualized by positron emission tomography (PET)/CT scan. Fondaparinux was identified as a feasible anticoagulation drug of choice for this case. At seven months post-treatment, the patient continues to be stable with no further evidence of thrombosis and is currently undergoing rituximab maintenance therapy every six months for two years. A repeat lupus anticoagulant antibody assay turned and remained negative during the clinical follow-up period. A prompt diagnosis and early aggressive treatment is potentially curative and may dramatically decrease the mortality risk. Future studies should explore the role of rituximab in the management of CAPS-associated B-cell lymphoid malignancies.