Sanjive Qazi

Inducing apoptosis in chemotherapy‐resistant B‐lineage acute lymphoblastic leukaemia cells by targeting HSPA5, a master regulator of the anti‐apoptotic unfolded protein response signalling network

We present previously unknown evidence that the immunoglobulin heavy chain binding protein BIP/HSPA5, also known as glucose regulated protein (GRP)78, serving as a pivotal component of the pro‐survival axis of the unfolded protein response (UPR) signalling network, is abundantly expressed in relapsed B‐lineage acute lymphoblastic leukaemia (ALL) and contributes to chemotherapy resistance of leukaemic B‐cell precursors. The resistance of B‐lineage ALL cells to the standard anti‐leukaemic drug vincristine was overcome by the HSPA5 inhibitor epigallocatechin gallate, which inhibits the anti‐apoptotic function of HSPA5 by targeting its ATP‐binding domain. Notably, chemotherapy‐resistant B‐lineage ALL cells underwent apoptosis within 48u2003h of exposure to a doxorubicin‐conjugated cell‐penetrating cyclic anti‐HSPA5 peptide targeting surface‐expressed HSPA5 molecules on leukaemia cells. The identification of the HSPA5 as a chemoresistance biomarker and molecular target for B‐lineage ALL may lead to new anti‐leukaemic treatment strategies that are much needed.

Targeting SYK kinase-dependent anti-apoptotic resistance pathway in B-lineage acute lymphoblastic leukaemia (ALL) cells with a potent SYK inhibitory pentapeptide mimic.

The present study found that the pentapeptide mimic C‐61, targeting the substrate binding P‐site of SYK tyrosine kinase acted as a potent inducer of apoptosis in chemotherapy‐resistant SYK‐expressing primary leukemic B‐cell precursors taken directly from relapsed B‐precursor leukaemia (BPL) patients (but not SYK‐deficient infant pro‐B leukaemia cells), exhibited favourable pharmacokinetics in mice and non‐human primates, and eradicated in vivo clonogenic leukaemia cells in severe combined immunodeficient mouse xenograft models of chemotherapy‐resistant human BPL at dose levels non‐toxic to mice and non‐human primates. These in vitro and in vivo findings provide proof of principle for effective treatment of chemotherapy‐resistant BPL by targeting SYK‐dependent anti‐apoptotic blast cell survival machinery with a SYK P‐Site inhibitor. Further development of C‐61 may provide the foundation for therapeutic innovation against chemotherapy‐resistant BPL.

Serine phosphorylation by SYK is critical for nuclear localization and transcription factor function of Ikaros

Ikaros is a zinc finger-containing DNA-binding protein that plays a pivotal role in immune homeostasis through transcriptional regulation of the earliest stages of lymphocyte ontogeny and differentiation. Functional deficiency of Ikaros has been implicated in the pathogenesis of acute lymphoblastic leukemia, the most common form of childhood cancer. Therefore, a stringent regulation of Ikaros activity is considered of paramount importance, but the operative molecular mechanisms responsible for its regulation remain largely unknown. Here we provide multifaceted genetic and biochemical evidence for a previously unknown function of spleen tyrosine kinase (SYK) as a partner and posttranslational regulator of Ikaros. We demonstrate that SYK phoshorylates Ikaros at unique C-terminal serine phosphorylation sites S358 and S361, thereby augmenting its nuclear localization and sequence-specific DNA binding activity. Mechanistically, we establish that SYK-induced Ikaros activation is essential for its nuclear localization and optimal transcription factor function.

Polo‐like‐kinase 1 (PLK1) as a molecular target to overcome SYK‐mediated resistance of B‐lineage acute lymphoblastic leukaemia cells to oxidative stress

SYK tyrosine kinase has emerged as a master regulator of cellular resistance to oxidative stress (OS) by mediating the activation of the anti‐apoptotic nuclear factor κB and phosphatidylinositol‐3 kinase/AKT pathways after OS exposure. Here, we present unprecedented experimental evidence that polo‐like kinase 1 (PLK1) is the upstream regulator of SYK in B‐lineage acute lymphoblastic leukaemia (ALL) cells. Selective inhibition of PLK‐1 with the leflunomide metabolite analogue α‐cyano‐β‐hydroxy‐β‐methyl‐N‐[4‐(trifluoromethoxy) phenyl]‐propenamide/LFM‐A12 abolished the resistance of B‐lineage ALL cells to OS by preventing the activation of the anti‐apoptotic SYK signal transduction pathway. Notably, LFM‐A12 treatments at non‐cytotoxic concentrations resulted in marked augmentation of clonogenic death in resistant human B‐lineage ALL cell lines challenged with OS. Further, LFM‐A12 augmented OS‐induced apoptosis of chemotherapy‐resistant primary leukaemic cells from relapsed B‐lineage ALL patients in vitro and markedly potentiated the in vivo anti‐leukaemic activity of total body irradiation (TBI) against leukaemia‐initiating cells in severe combined immunodeficient mouse xenograft models of B‐lineage ALL. This study is the first to identify PLK1 as a regulator of SYK tyrosine kinase and a molecular target to overcome SYK‐mediated resistance of B‐lineage ALL cells to OS.

Spleen tyrosine kinase as a molecular target for treatment of leukemias and lymphomas

Spleen tyrosine kinase (SYK) has emerged as a potential molecular target for the treatment of B-lineage leukemias and lymphomas. Here, we provide an overview of the current state of knowledge regarding the regulatory signaling function of SYK and its role in the pathogenesis of B-lineage lymphoid malignancies, available methods and drug candidates for targeting SYK, as well as compelling preclinical and clinical evidence regarding the clinical potential of inhibiting SYK. The further development of rationally designed SYK inhibitors may provide the foundation for therapeutic innovation against B-lineage leukemias and lymphomas.

Bruton's tyrosine kinase as a molecular target in treatment of leukemias and lymphomas as well as inflammatory disorders and autoimmunity

Importance of the field: Brutons tyrosine kinase (BTK) has emerged as a new anti-apoptotic molecular target for the treatment of B-lineage leukemias and lymphomas. Preclinical and early clinical results indicate that BTK inhibitors may be useful in the treatment of leukemias and lymphomas. BTK inhibitors may also be helpful in prevention and treatment of thromboembolic complications as well as inflammatory disorders. Areas covered in this review: We provide a comprehensive review of the target diseases for which the use of BTK inhibitors may be helpful as well as the activity profiles of BTK inhibitors. What the reader will gain: We review the currently available translational research, biomarker as well as patent literature regarding BTK molecular target and BTK inhibitors. Take home message: BTK inhibitors may provide the foundation for therapeutic innovation against B-lineage leukemias/lymphomas, inflammatory disorders and autoimmunity.

Nanoscale liposomal formulation of a SYK P-site inhibitor against B-precursor leukemia

We report preclinical proof of principle for effective treatment of B-precursor acute lymphoblastic leukemia (ALL) by targeting the spleen tyrosine kinase (SYK)-dependent antiapoptotic blast cell survival machinery with a unique nanoscale pharmaceutical composition. This nanoscale liposomal formulation (NLF) contains the pentapeptide mimic 1,4-Bis (9-O dihydroquinidinyl) phthalazine/hydroquinidine 1,4-phathalazinediyl diether (C61) as the first and only selective inhibitor of the substrate binding P-site of SYK. The C61 NLF exhibited a very favorable pharmacokinetic and safety profile in mice, induced apoptosis in primary B-precursor ALL blast cells taken directly from patients as well as in vivo clonogenic ALL xenograft cells, destroyed the in vivo clonogenic fraction of ALL blast cells, and, at nontoxic dose levels, exhibited potent in vivo antileukemic activity against patient-derived ALL cells in xenograft models of aggressive B-precursor ALL. Our findings establish SYK as an attractive molecular target for therapy of B-precursor ALL. Further development of the C61 NLF may provide the foundation for therapeutic innovation against therapy-refractory B-precursor ALL.

Effects of Aryl Substituents on the Anti-HIV Activity of the Arylphosphoramidate Derivatives of Stavudine

We compared the anti-HIV activity of 13 phenyl phosphate derivatives of stavudine (2′,3′-didehydro-2′,3′-dideoxythymidine/d4T) by examining their ability to inhibit HIV-1 replication in human peripheral blood mononuclear cells. Our results show that the introduction of electron-withdrawing substituents enhances the activity of these phosphoramidate derivatives. The rate of chemical hydrolysis under alkaline conditions (but not the lipophilicity) predicted the potency of the compounds.

Gene expression profiles of infant acute lymphoblastic leukaemia and its prognostically distinct subsets

This study compared the gene expression profiles of primary leukaemic cells from infants versus children with acute lymphoblastic leukaemia (ALL). Our analyses provided unprecedented evidence that remarkably different pathognomonic transcriptomes dominate the biology of infant versus paediatric high risk ALL. The genetic signature of infant ALL is characterized by concomitant overexpression of mitogenic and anti‐apoptotic genes, some of which have been associated with early relapse in ALL. Our study demonstrated that primary leukaemia cells from infant ALL patients expressed significantly higher levels of genes for cytokines that mediate their biological effects through stimulation of the JAK‐STAT signal transduction pathway including interleukin 1a, interleukin 1b, interleukin 2, and interleukin 7. We further showed that the JAK/STAT signalling pathway is constitutively active in CD10− infant ALL cells and treatment with a JAK3 inhibitor or a pan‐JAK kinase inhibitor effectively triggered their apoptosis. These findings identified JAK3 as an attractive molecular target for disrupting the constitutively deregulated anti‐apoptotic STAT3 and STAT5 signalling pathways in infant ALL cells.

Incidence and biological significance of IKZF1/Ikaros gene deletions in pediatric Philadelphia chromosome negative and Philadelphia chromosome positive B-cell precursor acute lymphoblastic leukemia

In recent years, there have been a series of contradictory reports based on studies that employed single-nucleotide polymorphism (SNP) arrays regarding the incidence and prognostic significance of IKZF1 deletions in primary leukemic cells from pediatric patients with high-risk B-cell precursor ALL (