Dipeptidylpeptidase IV (CD26) defines leukemic stem cells (LSC) in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a stem cell (SC) neoplasm characterized by the BCR/ABL1 oncogene. Although mechanisms of BCR/ABL1-induced transformation are well-defined, little is known about effector-molecules contributing to malignant expansion and the extramedullary spread of leukemic SC (LSC) in CML. We have identified the cytokine-targeting surface enzyme dipeptidylpeptidase-IV (DPPIV/CD26) as a novel, specific and pathogenetically relevant biomarker of CD34+/CD38─ CML LSC. In functional assays, CD26 was identified as target enzyme disrupting the SDF-1-CXCR4-axis by cleaving SDF-1, a chemotaxin recruiting CXCR4+ SC. CD26 was not detected on normal SC or LSC in other hematopoietic malignancies. Correspondingly, CD26+ LSC decreased to low or undetectable levels during successful treatment with imatinib. CD26+ CML LSC engrafted NOD-SCID-IL-2Rγ−/− (NSG) mice with BCR/ABL1+ cells, whereas CD26─ SC from the same patients produced multilineage BCR/ABL1– engraftment. Finally, targeting of CD26 by gliptins suppressed the expansion of BCR/ABL1+ cells. Together, CD26 is a new biomarker and target of CML LSC. CD26 expression may explain the abnormal extramedullary spread of CML LSC, and inhibition of CD26 may revert abnormal LSC function and support curative treatment approaches in this malignancy

Extensive pleural and pericardial effusion in chronic myeloid leukemia during treatment with dasatinib at 100 mg or 50 mg daily

Dasatinib is considered an effective drug in imatinib-resistant chronic myeloid leukemia. Although reported to be well-tolerated, severe events such as pleural or pericardial effusion have been reported at 140 mg daily. We examined our chronic myeloid leukemia patients treated with dasatinib at 100 mg or 50 mg daily and identified 4 of 13 patients who developed marked effusion formation. In 2 patients, grade III/IV pleural and/or pericardial effusions were recorded. All 4 patients had received previous anti-leukemia therapy but none had pre-existing cardiac or pulmonary diseases. In 3 patients, dasatinib had to be discontinued despite treatment with diuretics and glucocorticosteroids. In conclusion, dasatinib-treated chronic myeloid leukemia patients are at risk for the development of pleural and pericardial effusions even when the drug is administered at 100 mg or 50 mg daily. Therefore, all patients should be examined for pre-existing comorbidity and risk factors before starting dasatinib and all should have repeated chest X-rays during long-term dasatinib therapy

Identification of CD203c as a New Basophil-Specific Flow-Marker in Ph⁺ Chronic Myeloid Leukemia

Basophilia is a crucial prognostic variable in Ph-chromosome-positive chronic myeloid leukemia (CML). The ectoenzyme CD203c is an activation-linked surface antigen that is expressed specifically on basophil-committed progenitor cells and mature basophils. We examined the expression of CD203c on progenitors and/or basophils in 21 healthy donors and 44 patients with CML. As expected, the numbers of CD203c+ blood leukocytes were significantly higher in CML patients compared to controls (percentage of CD203c+ cells among viable cells in CML at diagnosis: 4.19 ± 3.68% vs. controls: 0.53 ± 0.23%, p + cells at diagnosis correlate with the disease-related risk-profile. Incubation of CML basophils with an anti-IgE-antibody resulted in further upregulation of CD203c. After successful treatment with imatinib and/or other BCR::ABL1 inhibitors leading to major or complete molecular responses, the numbers of CD203c+ basophils decreased substantially in our CML patients compared to pre-treatment values. Together, CD203c is overexpressed on CML basophils, is further upregulated by IgE receptor cross-linking, and may serve as a biomarker to quantify basophilia in patients with CML at diagnosis and during therapy