The two faces of myeloproliferative neoplasms: Molecular events underlying lymphoid transformation

Analyses and treatment of simultaneous bi-lineage malignancies of myeloid leukemia and lymphoma: Two case reports and a literature review

The present study reports two cases of concurrently diagnosed T-lymphoblastic lymphoma (T-LBL) and chronic myeloid leukemia (CML). The literature review revealed that myeloid leukemia may appear secondary to Hodgkin lymphoma or non-Hodgkin lymphoma. However, simultaneous bi-lineage hematologic malignancies are rarely seen and the prognosis is worse than single lineage lymphoma or myeloid leukemia. There were no standard therapies. All simultaneous bi-lineage malignancies of myeloid leukemia and lymphoma reported in Pubmed were combined with the present two cases, to analyses its pathogenesis, features and treatment. It was concluded that the prognosis of bi-lineage hematologic malignancies was poor, however allogeneic hematopoietic stem cell transplantation could improve survival (P=0.033).

Platelet-derived growth factor receptors (PDGFRs) fusion genes involvement in hematological malignancies

PURPOSE

To investigate oncogenic platelet-derived growth factor receptor(PDGFR) fusion genes involvement in hematological malignancies, the advances in the PDGFR fusion genes diagnosis and development of PDGFR fusions inhibitors.

METHODS

Literature search was done using terms "PDGFR and Fusion" or "PDGFR and Myeloid neoplasm" or 'PDGFR and Lymphoid neoplasm' or "PDGFR Fusion Diagnosis" or "PDGFR Fusion Targets" in databases including PubMed, ASCO.org, and Medscape.

RESULTS

Out of the 36 fusions detected, ETV6(TEL)-PDGFRB and FIP1L1-PDGFRA fusions were frequently detected, 33 are as a result of chromosomal translocation, FIP1L1-PDGFRA and EBF1-PDGFRB are the result of chromosomal deletion and CDK5RAP2- PDGFRΑ is the result of chromosomal insertion. Seven of the 34 rare fusions have detectable reciprocals.

CONCLUSION

RNA aptamers are promising therapeutic target of PDGFRs and diagnostic tools of PDGFRs fusion genes. Also, PDGFRs have variable prospective therapeutic strategies including small molecules, RNA aptamers, and interference therapeutics as well as development of adaptor protein Lnk mimetic drugs.

The platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) are major players in oncogenesis, drug resistance, and attractive oncologic targets in cancer

The platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) play a key role in signaling pathways in oncogenesis. The overexpression of PDGFs and PDGFRs and the oncogenic alterations of these receptors have been implicated in human cancers and correlated significantly with poor outcomes. This review discusses the biology of the PDGF isoforms and receptors briefly, and their role in oncogenesis. Also, the attractiveness of targeting PDGFs and PDGFRs, based on a wide display of oncologic alterations in cancers, diverse therapeutic strategies, their roles in resistance to cancer treatments with prospects of overcoming drug resistance, and the extent to which validated biomarkers have been developed for effective PDGFs and PDGFRs-based cancer management are discussed.

Expression of the TEL-Syk fusion protein in hematopoietic stem cells leads to rapidly fatal myelofibrosis in mice

The TEL-Syk fusion protein was isolated from a patient with myelodysplasia with megakaryocyte blasts. Expression of TEL-Syk transforms interleukin-3 (IL-3)-dependent Ba/F3 cells in vitro by deregulating STAT5-mediated signal transduction pathways. In vivo, TEL-Syk expression in pre-B cells blocks B cell differentiation, leading to lymphoid leukemia. Here, we demonstrate that TEL-Syk introduced into fetal liver hematopoietic cells, which are then adoptively transferred into lethally irradiated recipients, leads to an aggressive myelodysplasia with myelofibrosis that is lethal in mice by 60–75 days. Expression of TEL-Syk induces a short-lived myeloexpansion that is rapidly followed by bone marrow failure and extreme splenic/hepatic fibrosis accompanied by extensive apoptosis. The disease is dependent on Syk kinase activity. Analysis of serum from TEL-Syk mice reveals an inflammatory cytokine signature reminiscent of that found in the sera from patients and mouse models of myeloproliferative neoplasms. TEL-Syk expressing cells showed constitutive STAT5 phosphorylation, which was resistant to JAK inhibition, consistent with deregulated cytokine signaling. These data indicate that expression of TEL-Syk in fetal liver hematopoietic cells results in JAK-independent STAT5 phosphorylation ultimately leading to a uniquely aggressive and lethal form of myelofibrosis.

Allogeneic Hematopoietic Stem Cell Transplantation for a BCR-FGFR1 Myeloproliferative Neoplasm Presenting as Acute Lymphoblastic Leukemia

Hematopoietic myeloproliferative neoplasms (MPNS) with rearrangements of the receptor tyrosine kinase FGFR1 gene, located on chromosome 8p11, are uncommon and associated with diverse presentations such as atypical chronic myeloid leukemia, acute myeloid leukemia, or an acute T- or B-lymphoblastic leukemia, reflecting the hematopoietic stem cell origin of the disease. A review of MPN patients with the t(8;22) translocation that results in a chimeric BCR-FGFR1 fusion gene reveals that this disease either presents or rapidly transforms into an acute leukemia that is generally unresponsive to currently available chemotherapeutic regimens including tyrosine kinase inhibitors (TKIS). The first case of a rare BCR-FGFR1 MPN presenting in a B-acute lymphoblastic phase who underwent allogeneic hematopoietic stem cell transplantation (HSCT) with a subsequent sustained complete molecular remission is described. Allogeneic HSCT is currently the only available therapy capable of achieving long-term remission in BCR-FGFR1 MPN patients.

Ponatinib suppresses the development of myeloid and lymphoid malignancies associated with FGFR1 abnormalities

Myeloid and lymphoid malignancies associated with FGFR1 abnormalities are characterized by constitutive activated FGFR1 kinase and rapid transformation to acute myeloid leukemia and lymphoblastic lymphoma. Molecular targeted therapies have not been widely used for SCLL. Ponatinib (AP24534), that potently inhibits native and mutant BCR-ABL, also targets the fibroblast growth factor receptor (FGFR) family. Using murine BaF3 cells stably transformed with six different FGFR1 fusion genes, as well as human KG1 cells expressing activated chimeric FGFR1 and five newly established murine SCLL cell lines, we show that Ponatinib (< 50 nM) can effectively inhibit phosphoactivation of the fusion kinases and their downstream effectors, such as PLCγ, Stat5 and Src. Ponatinib also significantly extended survival of mice transplanted with different SCLL cell lines. Ponatinib administered at 30 mg/kg daily also significantly delayed, or even prevented, tumorigenesis of KG1 cells in xenotransplanted mice. Furthermore, we demonstrate that Ponatinib specifically inhibits cell growth and clonogenicity of normal human CD34+ progenitor cells transformed by chimeric FGFR1 fusion kinases. Overall, our data provide convincing evidence to suggest that pharmacologic inhibition of FGFR1 fusion kinases with Ponatinib is likely to be beneficial for patients with SCLL and perhaps for other human disorders associated with dysregulated FGFR1 activity.

Concurrent acute myeloid leukemia and T lymphoblastic lymphoma in a patient with rearranged PDGFRB genes

Concurrent hematologic malignancies are relatively rare. We encountered a case of concurrent acute myeloid leukemia (AML) and T lymphoblastic lymphoma. The bone marrow chromosome analysis showed the karyotype 46, XY, t(5;12)(q33;p13), which indicated presence of PDGFRB gene translocations. Therefore, this disease belongs to the new WHO category of myeloid and lymphoid neoplasms with abnormalities in PDGFRA, PDGFRB and FGFR1 genes. Although such genetic mutations are prone to multi-lineage differentiation, the present case is in fact the first report of concurrent AML and T lymphoblastic lymphoma involving PDGFRB mutations. The patient was treated with cytarabine and daunomycin in combination with high dose dexamethasone. Allogeneic stem cell transplantation was performed after successful remission induction for both entities. The patient eventually died of chronic graft-versus-host-disease related infection. Based on such an experience, we suggest the decision of stem cell transplantation should be weighed carefully against the risks, especially when tyrosine kinase inhibitors are safe and potentially effective in dealing with such entities.

Imatinib and beyond--targeting activated tyrosine kinases in myeloproliferative disorders

Tyrosine kinases (TKs) play a major role in cellular signal transduction. Deregulated TK activity has been observed in solid cancers and hematologic malignancies. Advances in the understanding of the oncogenic activation of TKs led to the identification of new kinase inhibitors with improved potency, specificity, and efficacy. With the advent of imatinib mesylate, a new era in the management of patients with BCR-ABL+ chronic myelogenous leukemia (CML), gastrointestinal stromal tumors, and myeloproliferative neoplasms including chronic myelomonocytic leukemia with PDGFRB gene rearrangements and hypereosinophilic syndrome has begun. CML represents a model for the rational design of TK inhibitors based on the insights into signal transduction pathways. In CML, treatment with imatinib led to an outstanding clinical efficacy with limited toxicity. In BCR-ABL-negative myeloproliferation, the finding of activating point mutations in JAK2 prompted the development of JAK inhibitors to target this activated pathway. Aberrations of epigenetically active genes are the latest finding in the pathogenesis of myeloproliferative disorders and will serve as another target for innovative therapies.