Exploiting Temporal Collateral Sensitivity in Tumor Clonal Evolution.

The prevailing approach to addressing secondary drug resistance in cancer focuses on treating the resistance mechanisms at relapse. However, the dynamic nature of clonal evolution, along with potential fitness costs and cost compensations, may present exploitable vulnerabilities-a notion that we term "temporal collateral sensitivity." Using a combined pharmacological screen and drug resistance selection approach in a murine model of Ph(+) acute lymphoblastic leukemia, we indeed find that temporal and/or persistent collateral sensitivity to non-classical BCR-ABL1 drugs arises in emergent tumor subpopulations during the evolution of resistance toward initial treatment with BCR-ABL1-targeted inhibitors. We determined the sensitization mechanism via genotypic, phenotypic, signaling, and binding measurements in combination with computational models and demonstrated significant overall survival extension in mice. Additional stochastic mathematical models and small-molecule screens extended our insights, indicating the value of focusing on evolutionary trajectories and pharmacological profiles to identify new strategies to treat dynamic tumor vulnerabilities.

Sestd1 Encodes a Developmentally Dynamic Synapse Protein That Complexes With BCR Rac1-GAP to Regulate Forebrain Dendrite, Spine and Synapse Formation.

SEC14 and Spectrin domain-1 (Sestd1) is a synapse protein that exhibits a striking shift from the presynaptic to postsynaptic space as neurons mature postnatally in the mouse hippocampus. Hippocampal pyramidal neurons from mice with global genetic deletion of Sestd1 have reduced dendrite arbors, spines, and excitatory synapses. Electrophysiologically this correlates with cell-autonomous reductions in both AMPA- and NMDA-excitatory postsynaptic currents in individual hippocampal neurons from which Sestd1 has been deleted in vivo. These neurodevelopmental and functional deficits are associated with increased activation of the Rho family GTPases Rac1 and RhoA. Co-immunoprecipitation and mass spectrometry reveal that the Breakpoint Cluster Region protein, a Rho GTPase activating protein (GAP), forms complexes with Sestd1 in brain tissue. This complements earlier findings that Sestd1 can also partner with other Rho family GAPs and guanine nucleotide exchange factors. Our findings demonstrate that Sestd1 is a developmentally dynamic synaptic regulator of Rho GTPases that contributes to dendrite and excitatory synapse formation within differentiating pyramidal neurons of the forebrain.

Co-encapsulation of anti-BCR-ABL siRNA and imatinib mesylate in transferrin receptor-targeted sterically stabilized liposomes for chronic myeloid leukemia treatment.

Chronic myeloid leukemia (CML) is triggered by the BCR-ABL oncogene. Imatinib is the first-line treatment of CML; however imatinib resistance and intolerance have been detected in many patients. Therefore, new therapeutic approaches are required. The present work aimed at the development and application of transferrin receptor (TrfR) targeted liposomes co-encapsulating anti-BCR-ABL siRNA and imatinib at different molar ratios. The encapsulation yields and drug loading of each molecule was evaluated. Anti-leukemia activity of the developed formulations co-encapsulating siRNA and imatinib and of the combination of Trf-liposomes carrying siRNA and free imatinib under two different treatment schedules of pre-sensitization was assessed. The results obtained demonstrate that the presence of imatinib significantly decreases the encapsulation yields of siRNA, whereas imatinib encapsulation yields are increased by the presence of siRNA. Cytotoxicity assays demonstrate that the formulations co-encapsulating siRNA and imatinib promote a 3.84-fold reduction on the imatinib IC(50) (from 3.49 to 0.91 µM), whereas a 8.71-fold reduction was observed for the pre-sensitization protocols (from 42.7 to 4.9 nM). It was also observed that the formulations with higher siRNA to imatinib molar ratios promote higher cell toxicity. Thus, the present work describes a novel triple targeting strategy with one single system: cellular targeting (through the targeting ligand, transferrin) and molecular targeting at the BCR-ABL mRNA and Bcr-Abl protein level.

Dual-modal label-free genosensor based on hemoglobin@gold nanocluster stabilized graphene nanosheets for the electrochemical detection of BCR/ABL fusion gene.

For the first time, we have successfully synthesized stable graphene nanosheets from graphite powder through sonication in the hemoglobin-capped gold nanoclusters (Hb@AuNCs) solution for biosensing application. This approach, as a simple method for the exfoliation and fragmentation of graphite in a nanocluster solution, enabled us to produce stable aqueous graphene dispersions at low cost and without the need for hazardous chemicals or tedious experimental procedures. In this method, Hb@AuNCs were used not only as stabilizing agent of graphene through non-covalent bonding, but also as dispersing agent of few-layer graphene nanosheets. The Hb@AuNCs stabilized graphene (Hb@AuNCs-G) was characterized by high resolution transmission electron microscopy (HRTEM), zeta-sizer and Raman spectroscopy. Then, the graphene nanosheets were applied as a novel versatile electrochemical platform for ultrasensitive biosensing of short DNA species of chronic myelogenous leukemia (CML) based on the "signal off" and "signal on" strategies. For this purpose, a single strand DNA (ssDNA) was immobilized on the Hb@AuNCs-G/AuNPs modified electrode surface and acted as the biorecognition element. Methylene blue (MB), as the signaling probe, was then intercalated into the ssDNA. The intercalated MB was liberated upon interaction with the synthetic complementary DNA (cDNA, target), thereby resulting in the apparent reduction of MB redox signal. This designed "signal off" sensing system enabled the voltammetric determination of the target cDNA over a dynamic linear range (DLR) of 0.1 fM to 10 pM with a limit of detection (LOD) of 0.037 fM. In the "signal on" strategy, the response to the cDNA was detected by monitoring the change in the electron transfer resistance (Rct) using the ferro/ferricyanide system as a redox probe. The charge transfer resistance of the probe was found to increase linearly with increasing concentration of target cDNA in the range of 0.1 fM-10 pM with a limit of detection of 0.030 fM. Finally, the selectivity and feasibility of genosensor was evaluated by the analysis of derived nucleotides from mismatched sequences and the clinical samples of patients with leukemia as real samples, respectively.

Detection and quantification of the Bcr/Abl chimeric protein on biochips using LDI-TOF MS.

The Bcr/Abl chimeric protein was captured by two antibodies, anti-Bcr on gold nanoparticles (AuNPs) and anti-Abl on a biochip, in a sandwich assay format. The presence of the Bcr/Abl in cells was then verified by amplified LDI-TOF MS signals, and relative amounts were quantified using AuNPs coated with deuterated alkanethiols as an internal standard.

Diagnosing myelodysplastic/myeloproliferative neoplasms: laboratory testing strategies to exclude other disorders.

INTRODUCTION: The 2008 World Health Organization classification of myeloid neoplasms includes the diagnostic category, myelodysplastic/myeloproliferative neoplasms (MDS/MPN), which encompasses those rare clonal myeloid proliferations that at initial presentation, show overlapping myeloproliferative and myelodysplastic features, making classification as either a myelodysplastic syndrome (MDS) or myeloproliferative neoplasm (MPN) problematic. There are four main subcategories, chronic myelomonocytic leukemia (CMML), atypical chronic myeloid leukemia, BCR-ABL1-negative (aCML), juvenile myelomonocytic leukemia (JMML), and myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U), which also includes the provisional entity, refractory anemia with ring sideroblasts associated with marked thrombocytosis (RARS-T). Notably, the morphological features typical of MDS/MPNs are not specific and can be seen in other myeloid neoplasms at presentation or as part of disease progression or transformation. METHODS AND RESULTS: This review presents a laboratory approach to diagnosing MDS/MPNs in adults that allows for the exclusion of other disorders that may be otherwise indistinguishable. Ancillary studies including cytochemistry, immunohistochemistry, flow cytometry, and genetic testing are discussed. CONCLUSION: The most appropriate classification of myeloid neoplasms presenting with hybrid myelodysplastic/myeloproliferative features requires a comprehensive clinical and laboratory assessment with careful integration of the morphological, immunophenotypic, genetic, and clinical characteristics.