Src kinases in Ph+ lymphoblastic leukemia

GZD824 suppresses the growth of human B cell precursor acute lymphoblastic leukemia cells by inhibiting the SRC kinase and PI3K/AKT pathways

Available therapeutic options for advanced B cell precursor acute lymphoblastic leukemia (pre-B ALL) are limited. Many lead to neutropenia, leaving patients at risk of life-threatening infections and result in bad outcomes. New treatment options are needed to improve overall survival. We previously showed that GZD824, a novel BCR-ABL tyrosine kinase inhibitor, has anti-tumor activity in Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia cells and tumor models. Here, we show that GZD824 decreases cell viability, induces cell-cycle arrest, and causes apoptosis in pre-B ALL cells. Furthermore, Ph– pre-B ALL cells were more sensitive to GZD824 than Ph+ pre-B ALL cells. GZD824 consistently reduced tumor loads in Ph– pre-B ALL xenografts but failed to suppress Ph+ pre-B ALL xenografts. GZD824 decreased phosphorylation of SRC kinase, STAT3, RB and C-myc. It also downregulated the expression of BCL-XL, CCND1 and CDK4 and upregulated expression of CCKN1A. Expression of IRS1 was decreased in GZD824-treated pre-B ALL cells, blocking the PI3K/AKT pathway. These data demonstrate that GZD824 suppresses pre-B ALL cells through inhibition of the SRC kinase and PI3K/AKT pathways and may be a potential therapeutic agent for the management of pre-B ALL.

Determinant of factors associated with child health outcomes and service utilization in Ghana: multiple indicator cluster survey conducted in 2011

Background

The effects of National Health Insurance Scheme in Ghana and its impact on child health outcome and service utilization cannot be underestimated. Despite the tremendous improvement in child health care in Ghana, there are still some challenges in relation to how National health insurance membership, socioeconomic status and other demographic factors impacts on child health outcomes. The study seeks to determine the association between NHIS membership, socio-economic status, geographic location and other relevant background factors, on child health service utilization and outcomes.

Methods

Secondary data from the Multiple Indicator Cluster Survey conducted in 2011 was used. Multivariate analysis based on Binary Logistic Regression Models and Multiple linear regression techniques was applied to determine factors associated with child health outcomes and service utilization. Collection of best models was based on Hosmer-Lemeshow Goodness-Of-Fit as one criterion of fit and the Akaike Information Criterion.

Results

Controlling for confounding effect of socioeconomic status, age of the child, mothers education level and geographic location, the odds of a child developing anemia for children with National Health Insurance Scheme Membership is 65.2% [95% CI: 52.9-80.2] times less than children without National Health Insurance Scheme Membership. The odds of being fully immunized against common childhood illnesses for children with NHIS membership is 2.3[95% CI: 1.4-3.7] times higher than children without National Health Insurance Scheme Membership. There was no association between National Health Insurance Scheme Membership and stunted growth in children.

Conclusions

National Health Insurance Scheme Membership was found to be related to child health service utilization (full immunization) of children under five a child’s anemia status. Children with NHIS are more likely to be fully immunized against common childhood diseases and are less likely to develop anemia. Stunted growth of children was not associated with National Health Insurance Scheme Membership. Health Education on the registration and the use of the National Health Insurance should be made a national priority to enable the Ministry of Health achieve routine Immunization targets and to reduce to the bearers minimum prevalence of anemia.

Robustness and accuracy of functional modules in integrated network analysis

MOTIVATION

High-throughput molecular data provide a wealth of information that can be integrated into network analysis. Several approaches exist that identify functional modules in the context of integrated biological networks. The objective of this study is 2-fold: first, to assess the accuracy and variability of identified modules and second, to develop an algorithm for deriving highly robust and accurate solutions.

RESULTS

In a comparative simulation study accuracy and robustness of the proposed and established methodologies are validated, considering various sources of variation in the data. To assess this variation, we propose a jackknife resampling procedure resulting in an ensemble of optimal modules. A consensus approach summarizes the ensemble into one final module containing maximally robust nodes and edges. The resulting consensus module identifies and visualizes robust and variable regions by assigning support values to nodes and edges. Finally, the proposed approach is exemplified on two large gene expression studies: diffuse large B-cell lymphoma and acute lymphoblastic leukemia.

BCR-ABL1-independent PI3Kinase activation causing imatinib-resistance

BACKGROUND

The BCR-ABL1 translocation occurs in chronic myeloid leukemia (CML) and in 25% of cases with acute lymphoblastic leukemia (ALL). The advent of tyrosine kinase inhibitors (TKI) has fundamentally changed the treatment of CML. However, TKI are not equally effective for treating ALL. Furthermore, de novo or secondary TKI-resistance is a significant problem in CML. We screened a panel of BCR-ABL1 positive ALL and CML cell lines to find models for imatinib-resistance.

RESULTS

Five of 19 BCR-ABL1 positive cell lines were resistant to imatinib-induced apoptosis (KCL-22, MHH-TALL1, NALM-1, SD-1, SUP-B15). None of the resistant cell lines carried mutations in the kinase domain of BCR-ABL1 and all showed resistance to second generation TKI, nilotinib or dasatinib. STAT5, ERK1/2 and the ribosomal S6 protein (RPS6) are BCR-ABL1 downstream effectors, and all three proteins are dephosphorylated by imatinib in sensitive cell lines. TKI-resistant phosphorylation of RPS6, but responsiveness as regards JAK/STAT5 and ERK1/2 signalling were characteristic for resistant cell lines. PI3K pathway inhibitors effected dephosphorylation of RPS6 in imatinib-resistant cell lines suggesting that an oncogene other than BCR-ABL1 might be responsible for activation of the PI3K/AKT1/mTOR pathway, which would explain the TKI resistance of these cells. We show that the TKI-resistant cell line KCL-22 carries a PI3Kα E545G mutation, a site critical for the constitutive activation of the PI3K/AKT1 pathway. Apoptosis in TKI-resistant cells could be induced by inhibition of AKT1, but not of mTOR.

CONCLUSION

We introduce five Philadelphia-chromosome positive cell lines as TKI-resistance models. None of these cell lines carries mutations in the kinase domain of BCR-ABL1 or other molecular aberrations previously indicted in the context of imatinib-resistance. These cell lines are unique as they dephosphorylate ERK1/2 and STAT5 after treatment with imatinib, while PI3K/AKT1/mTOR activity remains unaffected. Inhibition of AKT1 leads to apoptosis in the imatinib-resistant cell lines. In conclusion, Ph+ cell lines show a form of imatinib-resistance attributable to constitutive activation of the PI3K/AKT1 pathway. Mutations in PIK3CA, as observed in cell line KCL-22, or PI3K activating oncogenes may undelie TKI-resistance in these cell lines.

Stem cell and kinase activity-independent pathway in resistance of leukaemia to BCR-ABL kinase inhibitors

BCR-ABL tyrosine kinase inhibitors, such as imatinib (Gleevec) are highly effective in treating human Philadelphia chromosome-positive (Ph⁺) chronic myeloid leukaemia (CML) in chronic phase but not in terminal acute phase; acquired drug resistance caused mainly by the development of BCR-ABL kinase domain mutations prevents cure of the leukaemia. In addition, imatinib is ineffective in treating Ph⁺ B-cell acute lymphoblastic leukaemia (B-ALL) and CML blast crisis, even in the absence of the kinase domain mutations. This type of drug resistance that is unrelated to BCR-ABL kinase domain mutations is caused by the insensitivity of leukaemic stem cells to kinase inhibitors such as imatinib and dasatinib, and by activation of a newly-identified signalling pathway involving SRC kinases that are independent of BCR-ABL kinase activity for activation. This SRC pathway is essential for leukaemic cells to survive imatinib treatment and for CML transition to lymphoid blast crisis. Apart from BCR-ABL and SRC kinases, stem cell pathways must also be targeted for curative therapy of Ph⁺ leukaemia.

Src kinase signaling in leukaemia

Role of Src kinases in acute lymphoblastic leukaemia has been recently demonstrated in leukaemia mouse model. Retained activation of Src kinases by the BCR-ABL oncoprotein in leukaemic cells following inhibition of BCR-ABL kinase activity by imatinib indicates that Src activation by BCR-ABL is independent of BCR-ABL kinase activity and provides an explanation for reduced effectiveness of the BCR-ABL kinase activity inhibitors in Philadelphia chromosome-positive acute lymphoblastic leukaemia. Simultaneous inhibition of kinase activity of both BCR-ABL and Src kinases results in long-term survival of mice with acute lymphoblastic leukaemia. Leukaemic stem cells exist in acute lymphoblastic leukaemia, and complete eradication of this group of cells would provide a curative therapy for this disease.

Src kinases as targets for B cell acute lymphoblastic leukaemia therapy

The participation of Src kinases in the induction of BCR-ABL-induced B cell acute lymphoblastic leukaemia (B-ALL), but not chronic myeloid leukaemia (CML), demonstrates cell type-specific signalling in Philadelphia chromosome-positive (Ph+) leukaemias. Different therapeutic strategies are therefore needed for B-ALL and CML. Activation of Src kinases is independent of BCR-ABL kinase activity for activation. Thus, Src kinases provide a mechanism for resistance to the BCR-ABL kinase inhibitors and potential targets for B-ALL therapy. Simultaneous targeting of both BCR-ABL and Src kinases may benefit human B-ALL patients. Leukaemic stem cells may exist in Ph+ B-ALL, and eradication of this group of cells would provide a curative method for this disease.

The development of imatinib as a therapeutic agent for chronic myeloid leukemia

Imatinib has revolutionized drug therapy of chronic myeloid leukemia (CML). Preclinical studies were promising but the results of clinical trials by far exceeded expectations. Responses in chronic phase are unprecedented, with rates of complete cytogenetic response (CCR) of more than 40% in patients after failure of interferon-α (IFN) and more than 80% in newly diagnosed patients, a level of efficacy that led to regulatory approval in record time. While most of these responses are stable, resistance to treatment after an initial response is common in more advanced phases of the disease. Mutations in the kinase domain (KD) of BCR-ABL that impair imatinib binding have been identified as the leading cause of resistance. Patients with CCR who achieve a profound reduction of BCR-ABL mRNA have a very low risk of disease progression. However, residual disease usually remains detectable with reverse transcription–polymerase chain reaction (RT-PCR), indicating that disease eradication may pose a significant challenge. The mechanisms underlying the persistence of minimal residual disease are unknown. In this manuscript, we review the preclinical and clinical development of imatinib for the therapy of CML, resistance and strategies that may help to eliminate resistant or residual leukemia.