Fig 2 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Phosphokinase array analysis of STA-ET.7.2 cells after treatment with clofarabine and CD99 antibody. (A) Phosphokinase screening of cells treated with clofarabine (0.6 μM) and DMSO (upper pair) or CD99 antibody (15 μg/ ml), and IgM (15 μg/ml) (lower pair). Protein coordinates of the kinase array are given in S1 Fig; (B) Analysis of band intensity after treatment with clofarabine and CD99 antibody is given. Red color indicates increased phosphorylation, black color indicates no change and green color indicates decreased phosphorylation compared to control in each group. ERK1/2, MSK1/2, CREB, c-Jun, HSP60, Hck and STAT5 phosphorylation levels were increased while STAT3 and AMPKα1 were decreased for both treatment groups. https://doi.org/10.1371/journal.pone.0253170.g002
Source publication
Clofarabine, an FDA approved purine analog, is used in the treatment of relapsed or refractory acute lymphoblastic leukemia. Clofarabine acts by inhibiting DNA synthesis. We demonstrated that clofarabine may have a novel function though inhibiting CD99, a transmembrane protein highly expressed on Ewing Sarcoma (ES) cells. CD99 is a validated target...
Contexts in source publication
Context 1
... positive result required a signal in both protein spots. Clofarabine treatment showed increased phosphorylation of 15 proteins, and decreased phosphorylation of 17 proteins (Fig 2A, upper panel). CD99 targeting antibody (clone [HO36-1.1]) ...
Context 2
... increased phosphorylation of 16 proteins and decreased phosphorylation of 3 proteins when compared to the negative control total IgM antibody. We focused on the phosphorylation events that were upregulated or down regulated by both clofarabine and anti-CD99 treatments (Fig 2B). We concluded that if a specific phosphorylation event is induced by both clofarabine and anti-CD99 treatments, it has a higher probability of being directly regulated by CD99 protein on the plasma membrane. ...
Citations
Acute myeloid leukaemia (AML) is a fatal and refractory haematologic cancer that primarily affects adults. It interferes with bone marrow cell proliferation. Patients have a 5 years survival rate of less than 30% despite the availability of several treatments, including chemotherapy, allogeneic haematopoietic stem cell transplantation (Allo‐HSCT), and receptor antagonist drugs. Allo‐HSCT is the mainstay of acute myeloid leukaemia treatment. Although it does work, there are severe side effects, such as graft‐versus‐host disease (GVHD). In recent years, chimeric antigen receptor (CAR)‐T cell therapies have made significant progress in the treatment of cancer. These engineered T cells can locate and recognize tumour cells in vivo and release a large number of effectors through immune action to effectively kill tumour cells. CAR‐T cells are among the most effective cancer treatments because of this property. CAR‐T cells have demonstrated positive therapeutic results in the treatment of acute myeloid leukaemia, according to numerous clinical investigations. This review highlights recent progress in new targets for AML immunotherapy, and the limitations, and difficulties of CAR‐T therapy for AML.
Ewing Sarcoma (ES) is a cancer of bone and soft tissues affecting mostly children and young adults. Aggressive progression and poor prognosis of this malignancy call for novel and targeted treatments. CD99 is a transmembrane protein that is abundantly expressed on ES cells and is a diagnostic marker for the disease. ES cells are selectively sensitive to CD99 inhibition compared to most normal cells and other tumors. Therefore, CD99 is a good molecular target for ES treatment. Clofarabine and cladribine are two FDA approved drugs that are administered for their inhibitory acts on DNA synthesis to treat relapsed or refractory acute lymphoblastic and myeloid leukemia. They have also been shown to directly bind to CD99 and inhibit ES growth through a distinct mechanism. In the current study, we designed, synthesized and tested new ES specific derivatives of both drugs that would continue to target CD99 but with expected reduction in cellular membrane permeability and rendered unsuitable for inhibiting DNA synthesis. By using commercially available clofarabine and cladribine purine nucleoside analogs, we modified the primary alcohol moiety at the deoxyribose C-5' terminal site to suppress phosphorylation and thus inhibition of subsequent DNA synthesis pathways. In addition, we incorporated a variety of polar groups in the ribose and purine rings to reduce membrane permeability and investigated the effects of configurational changes in the sugar moiety. Among 26 new derivatives, we identified two compounds, BK50164 and BK60106, that cause cell death specifically in ES primarily due to inhibition of CD99 but not via inhibition of DNA synthesis. These findings provide a road map for the future development selective CD99 inhibitors for targeted treatment of ES.
The CD99 gene encodes a transmembrane protein that is involved in cell differentiation, adhesion, migration, and protein trafficking. CD99 is differentially expressed on the surface of hematopoietic cells both in the myeloid and lymphoid lineages. CD99 has two isoforms, the long and short isoforms that play different roles depending on the cellular context. There has been extensive evidence supporting the role of CD99 in myeloid and lymphoblastic leukemias. Here we review research findings related to the CD99 in malignant hematopoiesis. We also summarize the significance of CD99 as a therapeutic target in hematological malignancies.
