Tyrosine kinases in KMT2A/MLL-rearranged acute leukemias as potential therapeutic targets to overcome cancer drug resistance

Aim: The main goal of this study was to elucidate at the transcript level the tyrosine kinase expression profiles of primary leukemia cells from mixed lineage leukemia 1 gene rearranged (KMT2A/MLL-R⁺) acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) patients. Methods: We evaluated protein tyrosine kinase (PTK) gene expression profiles of primary leukemic cells in KMT2A/MLL-R⁺ AML and ALL patients using publicly available archived datasets. Results: Our studies provided unprecedented evidence that the genetic signatures of KMT2A/MLL-R⁺ AML and ALL cells are characterized by transcript-level overexpression of specific PTK. In infants, children and adults with KMT2A/MLL-R⁺ ALL, as well as pediatric patients with KMT2A/MLL-R⁺ AML, the gene expression levels for FLT3, BTK, SYK, JAK2/JAK3, as well as several SRC family PTK were differentially amplified. In adults with KMT2A/MLL-R⁺ AML, the gene expression levels for SYK, JAK family kinase TYK2, and the SRC family kinases FGR and HCK were differentially amplified. Conclusion: These results provide new insights regarding the clinical potential of small molecule inhibitors of these PTK, many of which are already FDA/EMA-approved for other indications, as components of innovative multi-modality treatment platforms against KMT2A/MLL-R⁺ acute leukemias.

Epigenetic Modifications in Acute Lymphoblastic Leukemia: From Cellular Mechanisms to Therapeutics

BACKGROUND

Epigenetic modification pattern is considered as a characteristic feature in blood malignancies. Modifications in the DNA methylation modulators are recurrent in lymphoma and leukemia, so that the distinct methylation pattern defines different types of leukemia. Generally, the role of epigenetics is less understood, and most investigations are focused on genetic abnormalities and cytogenic studies to develop novel treatments for patients with hematologic disorders. Recently, understanding the underlying mechanism of acute lymphoblastic leukemia (ALL), especially epigenetic alterations as a driving force in the development of ALL opens a new era of investigation for developing promising strategy, beyond available conventional therapy.

OBJECTIVE

This review will focus on a better understanding of the epigenetic mechanisms in cancer development and progression, with an emphasis on epigenetic alterations in ALL including, DNA methylation, histone modification, and microRNA alterations. Other topics that will be discussed include the use of epigenetic alterations as a promising therapeutic target in order to develop novel, well-suited approaches against ALL.

CONCLUSION

According to the literature review, leukemogenesis of ALL is extensively influenced by epigenetic modifications, particularly DNA hyper-methylation, histone modification, and miRNA alteration.

Novel Therapies in Acute Lymphoblastic Leukemia

PURPOSE OF REVIEW

Treatment options for patients with acute lymphoblastic leukemia (ALL) beyond standard chemotherapy have grown significantly in recent years. In this review, we highlight new targeted therapies in ALL, with an emphasis on immunotherapy.

RECENT FINDINGS

Major advances include antibody-based therapies, such as naked monoclonal antibodies, antibody-drug conjugates and bispecific T cell engaging (BiTE) antibodies, as well as adoptive cellular therapies such as chimeric antigen receptor (CAR) T cells. Apart from the above immunotherapeutic approaches, other targeted therapies are being employed in Philadelphia chromosome-positive (Ph+) ALL, Philadelphia-like (Ph-like) ALL, and T cell ALL. These new treatment strategies are changing the treatment landscape of ALL and challenging the current standard of care. Clinical trials will hopefully help determine how to best incorporate these novel therapies into existing treatment algorithms.

Identification of spleen tyrosine kinase as a potential therapeutic target for esophageal squamous cell carcinoma using reverse phase protein arrays

The vast majority of esophageal cancers in China, India and Iran are esophageal squamous cell carcinomas (ESCC). A timely diagnosis provides surgical removal as the main therapeutic option for patients with ESCC. Currently, there are no targeted therapies available for ESCC. We carried out reverse phase protein array-based protein expression profiling of seven ESCC-derivedcell lines and a non-neoplastic esophageal epithelial cell line (Het-1A) to identify differentially expressed proteins in ESCC. SYK non-receptortyrosine kinase was overexpressed in six out of seven ESCC cell lines that were used in the study. We evaluated the role of SYK in ESCC using the pharmacological inhibitor entospletinib (GS-9973) and siRNA-based knock down studies. Entospletinib is a selective inhibitor of SYK, which is currently being evaluated in phase II clinical trials for hematological malignancies. Using in vivo subcutaneous tumor xenografts in mice, we demonstrate that treatment with entospletinib significantly inhibits tumor growth. Further clinical studies are needed to prove the efficacy of entospletinib as a targeted therapeutic agent for treating ESCC.

Identification of spleen tyrosine kinase as a potential therapeutic target for esophageal squamous cell carcinoma using reverse phase protein arrays

The vast majority of esophageal cancers in China, India and Iran are esophageal squamous cell carcinomas (ESCC). A timely diagnosis provides surgical removal as the main therapeutic option for patients with ESCC. Currently, there are no targeted therapies available for ESCC. We carried out reverse phase protein array-based protein expression profiling of seven ESCC-derivedcell lines and a non-neoplastic esophageal epithelial cell line (Het-1A) to identify differentially expressed proteins in ESCC. SYK non-receptortyrosine kinase was overexpressed in six out of seven ESCC cell lines that were used in the study. We evaluated the role of SYK in ESCC using the pharmacological inhibitor entospletinib (GS-9973) and siRNA-based knock down studies. Entospletinib is a selective inhibitor of SYK, which is currently being evaluated in phase II clinical trials for hematological malignancies. Using in vivo subcutaneous tumor xenografts in mice, we demonstrate that treatment with entospletinib significantly inhibits tumor growth. Further clinical studies are needed to prove the efficacy of entospletinib as a targeted therapeutic agent for treating ESCC.

CD19-antigen specific nanoscale liposomal formulation of a SYK P-site inhibitor causes apoptotic destruction of human B-precursor leukemia cells

We report the anti-leukemic potency of a unique biotargeted nanoscale liposomal nanoparticle (LNP) formulation of the spleen tyrosine kinase (SYK) P-site inhibitor C61. C61-loaded LNP were decorated with a murine CD19-specific monoclonal antibody directed against radiation-resistant CD19-receptor positive aggressive B-precursor acute lymphoblastic leukemia (ALL) cells. The biotargeted C61-LNP were more potent than untargeted C61-LNP and consistently caused apoptosis in B-precursor ALL cells. The CD19-directed C61-LNP also destroyed B-precursor ALL xenograft cells and their leukemia-initiating in vivo clonogenic fraction. This unique nanostructural therapeutic modality targeting the SYK-dependent anti-apoptotic blast cell survival machinery shows promise for overcoming the clinical radiochemotherapy resistance of B-precursor ALL cells.

Liposomal Nanoparticles of a Spleen Tyrosine Kinase P-Site Inhibitor Amplify the Potency of Low Dose Total Body Irradiation Against Aggressive B-Precursor Leukemia and Yield Superior Survival Outcomes in Mice

This study was designed to improve the efficacy of radiation therapy against radiation-resistant leukemia. We report that the potency of low dose radiation therapy against B-precursor acute lymphoblastic leukemia (BPL) can be markedly enhanced by combining radiation with a liposomal nanoparticle (LNP) formulation of the SYK-P-site inhibitor C61 (“C61-LNP”). C61-LNP plus low dose total body irradiation (TBI) was substantially more effective than TBI alone or C61-LNP alone in improving the event-free survival outcome NOD/SCID mice challenged with an otherwise invariably fatal dose of human ALL xenograft cells derived from relapsed BPL patients. C61-LNP plus low dose TBI also yielded progression-free survival, tumor-free survival and overall survival outcomes in CD22ΔE12 × BCR–ABL double transgenic mice with advanced stage, radiation-resistant BPL with lymphomatous features that were significantly superior to those of mice treated with TBI alone or C61-LNP alone.

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Liposomal nanoparticles of C61 kill radiation-resistant leukemia cells

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Liposomal nanoparticles of C61 potentiate TBI against human leukemia cells

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Liposomal nanoparticles of C61 plus TBI improve the survival outcome of leukemic mice.

A PREVIOUSLY UNKNOWN UNIQUE CHALLENGE FOR INHIBITORS OF SYK ATP-BINDING SITE: ROLE OF SYK AS A CELL CYCLE CHECKPOINT REGULATOR

The identification of SYK as a molecular target in B-lineage leukemia/lymphoma cells prompted the development of SYK inhibitors as a new class of anti-cancer drug candidates. Here we report that induction of the SYK gene expression in human cells causes a significant down-regulation of evolutionarily conserved genes associated with mitosis and cell cycle progression providing unprecedented evidence that SYK is a master regulator of cell cycle regulatory checkpoint genes in human cells. We further show that SYK regulates the G₂ checkpoint by physically associating with and inhibiting the dual-specificity phosphatase CDC25C via phosphorylation of its S216 residue. SYK depletion by RNA interference or treatment with the chemical SYK inhibitor prevented nocodazole-treated human cell lines from activating the G₂ checkpoint via CDC25C S216-phosphorylation and resulted in polyploidy. Our study provides genetic and biochemical evidence that spleen tyrosine kinase (SYK) has a unique role in the activation of the G₂ checkpoint in both non-lymphohematopoietic and B-lineage lymphoid cells. This previously unknown role of SYK as a cell cycle checkpoint regulator represents an unforeseen and significant challenge for inhibitors of SYK ATP binding site.

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SYK is a cell cycle regulatory kinase that phosphorylates CDC25C at S216

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SYK is a master regulator of cell cycle regulatory checkpoint genes in human cells

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Inhibitors of SYK ATP binding site may increase the risk for secondary cancer

Selective X-ray contrast enhancement of the spleen of living mice mediated by gold nanorods

Gold nanomaterials (AuNPs) represent a promising new class of contrast agents for X-ray computed tomographic (CT) imaging in both research and clinical settings. These materials exhibit superior X-ray absorption properties compared with other iodinated agents, and thus require lower injection doses. Gold is nonimmunogenic and therefore contributes to safety profile in living specimens. Unfortunately, most reports on the use of AuNPs as X-ray CT enhancers only demonstrate marginal enhancement of the intended anatomical structure. In this study, we demonstrate the dramatic properties of gold nanorods (GNR) to serve as robust X-ray CT contrast-enhancing agent for selective imaging of the spleen. These organ-specific uptake properties were delineated by performing longitudinal CT imaging of living mice that were dosed with GNR at 2 day intervals. Rapid uptake in spleen was noted within 12 h of first systemic administration with a change in contrast enhancement of 90 Hounsfield units (ΔHU = 90) and with two subsequent injections a total contrast enhancement of over 200 HU was observed. The resulting images provide excellent contrast that will enable the detailed anatomical visualization and study of a range of pre-clinical models of spleen disease including infection and cancer.

Nanopharmacology in translational hematology and oncology

Nanoparticles have displayed considerable promise for safely delivering therapeutic agents with miscellaneous therapeutic properties. Current progress in nanotechnology has put forward, in the last few years, several therapeutic strategies that could be integrated into clinical use by using constructs for molecular diagnosis, disease detection, cytostatic drug delivery, and nanoscale immunotherapy. In the hope of bringing the concept of nanopharmacology toward a viable and feasible clinical reality in a cancer center, the present report attempts to present the grounds for the use of cell-free nanoscale structures for molecular therapy in experimental hematology and oncology.

Pediatric relapsed or refractory leukemia: new pharmacotherapeutic developments and future directions

Over the past 50 years, numerous advances in treatment have produced dramatic increases in the cure rates of pediatric leukemias. Despite this progress, the majority of children with relapsed leukemia are not expected to survive. With current chemotherapy regimens, approximately 15 % of children with acute lymphoblastic leukemia and 45 % of children with acute myeloid leukemia will have refractory disease or experience a relapse. Advances in the treatment of pediatric relapsed leukemia have not mirrored the successes of upfront therapy, and newer treatments are desperately needed in order to improve survival in these challenging patients. Recent improvements in our knowledge of cancer biology have revealed an extensive number of targets that have the potential to be exploited for anticancer therapy. These advances have led to the development of a number of new treatments that are now being explored in children with relapsed or refractory leukemia. Novel agents seek to exploit the same molecular aberrations that contribute to leukemia development and resistance to therapy. Newer classes of drugs, including monoclonal antibodies, tyrosine kinase inhibitors and epigenetic modifiers are transforming the treatment of patients who are not cured with conventional therapies. As the side effects of many new agents are distinct from those seen with conventional chemotherapy, these treatments are often explored in combination with each other or combined with conventional treatment regimens. This review discusses the biological rationale for the most promising new agents and the results of recent studies conducted in pediatric patients with relapsed leukemia.

SYK as a New Therapeutic Target in B-Cell Precursor Acute Lymphoblastic Leukemia

The identification of SYK as a master regulator of apoptosis controlling the activation of the PI3-K/AKT, NFκB, and STAT3 pathways—three major anti-apoptotic signaling pathways in B-lineage leukemia/lymphoma cells—prompts the hypothesis that rationally designed inhibitors targeting SYK may overcome the resistance of malignant B-lineage lymphoid cells to apoptosis and thereby provide the foundation for more effective multi-modality treatment regimens for poor prognosis B-precursor acute lymphoblastic leukemia (BPL). In recent preclinical proof-of-concept studies, a liposomal nanoparticle (LNP) formulation of a SYK substrate-binding site inhibitor, known as C61, has been developed as a nanomedicine candidate against poor prognosis and relapsed BPL. This nanoscale formulation of C61 exhibited a uniquely favorable pharmacokinetics and safety profile in mice, induced apoptosis in radiation-resistant primary leukemic cells taken directly from BPL patients as well as in vivo clonogenic BPL xenograft cells, destroyed the leukemic stem cell fraction of BPL blasts, and exhibited potent in vivo anti-leukemic activity in xenograft models of aggressive BPL. Further development of C61-LNP may provide the foundation for new and effective treatment strategies against therapy-refractory BPL.

Protein kinase inhibitors against malignant lymphoma

INTRODUCTION

Tyrosine kinases (TKs) are intimately involved in multiple signal transduction pathways regulating survival, activation, proliferation and differentiation of lymphoid cells. Deregulation or overexpression of specific oncogenic TKs is implicated in maintaining the malignant phenotype in B-lineage lymphoid malignancies. Several novel targeted TK inhibitors (TKIs) have recently emerged as active in the treatment of relapsed or refractory B-cell lymphomas that inhibit critical signaling pathways, promote apoptotic mechanisms or modulate the tumor microenvironment.

AREAS COVERED

In this review, the authors summarize the clinical outcomes of newer TKIs in various B-cell lymphomas from published and ongoing clinical studies and abstracts from major cancer and hematology conferences.

EXPERT OPINION

Multiple clinical trials have demonstrated that robust antitumor activity can be obtained with TKIs directed toward specific oncogenic TKs that are genetically deregulated in various subtypes of B-cell lymphomas. Clinical success of targeting TKIs is dependent upon on identifying reliable molecular and clinical markers associated with select cohorts of patients. Further understanding of the signaling pathways should stimulate the identification of novel molecular targets and expand the development of new therapeutic options and individualized therapies.

Development of a pharmacodynamic assay based on PLCγ2 phosphorylation for quantifying spleen tyrosine kinase (SYK)-Bruton's tyrosine kinase (BTK) signaling

Spleen tyrosine kinase (SYK) and Bruton's tyrosine kinase (BTK) are key mediators in coupling cell surface receptors, such as the B-cell receptor (BCR), to downstream signaling events affecting diverse biological functions. There is therefore tremendous interest in the development of pharmacological inhibitors targeting the SYK-BTK axis for the treatment of inflammatory disorders and hematological malignancies. A good pharmacodynamic (PD) assay, ideally a blood-based assay that measures proximal events, is warranted for evaluation of such inhibitors. In platelets, collagen-induced activation of membrane glycoprotein GPVI is dependent on the SYK-BTK axis. Here, we report the development of a novel immunoassay that uses the dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA) to measure GPVI-mediated phosphorylation of phospholipase C γ2 (PLCγ2), a direct substrate of SYK and BTK, in platelets. The assay was validated using SYK or BTK inhibitors and generated IC50 correlated with those from the BCR-induced B-cell activation assay. Furthermore, this assay showed good stability and uniformity over a period of 24 h in different donors. Interestingly, compound IC50 values using blood from patients with rheumatoid arthritis were slightly higher compared with those produced using samples from healthy donors. This novel platelet PLCγ2 phosphorylation-based immunoassay should serve as a promising PD assay for preclinical and clinical development of inhibitors targeting the SYK-BTK axis.

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.

Hedgehog pathway inhibitors: a patent review (2009--present)

INTRODUCTION

The hedgehog (Hh) pathway is a developmental signaling pathway that plays a key role in directing cellular growth and tissue patterning during embryonic development. Dysregulation of Hh signaling has been linked to the development of a variety of human tumors, and numerous drug development programs in both academia and industry are actively exploring inhibitors of the pathway as anti-cancer agents.

AREAS COVERED

This review surveys the recent patent literature (2009 - 2012) for Hh pathway inhibitors as treatments for a variety of human malignancies.

EXPERT OPINION

To date, all of the pathway inhibitors that have entered clinical trials and the majority of compounds identified via high-throughput screens target smoothened (Smo), a transmembrane protein that is essential for pathway signaling. While these compounds have shown initial promise in preclinical and clinical trials, several mechanisms of resistance to Smo inhibitors have been identified. Even with this knowledge, the majority of small-molecule pathway inhibitors disclosed in the recent patent literature directly target Smo. The continued identification of Hh pathway inhibitors that function either upstream or downstream is warranted not only to combat these emerging resistance mechanisms, but also to help elucidate the various cellular mechanisms that control both normal and oncogenic pathway signaling.

Serum spleen tyrosine kinase and vascular endothelial growth factor-C levels predict lymph node metastasis of oesophageal squamous cell carcinoma

OBJECTIVES

Lymph node involvement is a key feature and an independent prognostic factor of oesophageal squamous cell carcinoma. However, an accurate and robust assay to predict the lymphatic spread of oesophageal squamous cell carcinoma is unavailable. The purpose of this study was to determine whether serum vascular endothelial growth factor-C (VEGF-C) and spleen tyrosine kinase levels are potential markers of lymph node metastasis in patients with oesophageal squamous cell carcinoma.

METHODS

In the study, 108 patients with oesophageal squamous cell carcinoma and 24 healthy subjects participated. Serum spleen tyrosine kinase and VEGF-C concentrations were examined by enzyme-linked immunosorbent assays.

RESULTS

Patients with oesophageal squamous cell carcinoma had significantly elevated VEGF-C and decreased spleen tyrosine kinase in serum when compared with normal controls (P < 0.05). Pearson's correlation analysis revealed that serum spleen tyrosine kinase was negatively correlated with the serum VEGF-C level in oesophageal squamous cell carcinoma patients (r = -0.453, P = 0.000). In addition, surgical resections of the oesophageal tumour profoundly brought both serum spleen tyrosine kinase and VEGF-C closer to the normal range at 2 weeks after operation (P < 0.05). Statistical analysis showed that enhanced serum VEGF-C and reduced spleen tyrosine kinase significantly correlated with the stage of regional lymph node metastasis, tumour size and the status of primary tumour extension, but not with other clinicopathological features of the patients (P < 0.05).

CONCLUSIONS

Our data suggest that both serum spleen tyrosine kinase and VEGF-C levels are valuable in the preoperative evaluation of lymph node metastasis in patients with oesophageal squamous cell carcinoma.

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.

Tyrosine kinase inhibitors as potential drugs for B-cell lymphoid malignancies and autoimmune disorders

INTRODUCTION

In the last few years, several tyrosine kinase inhibitors (TKIs) have been synthesized and become available for preclinical studies and clinical trials. This article summarizes recent achievements in the mechanism of action, pharmacological properties, and clinical activity and toxicity, as well as the emerging role of TKIs in lymphoid malignancies, allergic diseases, and autoimmune disorders.

AREAS COVERED

A literature review was conducted of the MEDLINE database PubMed for articles in English. Publications from 2000 through January 2012 were scrutinized. The search terms used were Bruton's tyrosine kinase (Btk) inhibitors, PCI-32765, GDC-0834, LFM-A13, AVL-101, AVL-292, spleen tyrosine kinase (Syk) inhibitors, R343, R406, R112, R788, fostamatinib, BAY-61-3606, C-61, piceatannol, Lyn, imatinib, nilotinib, bafetinib, dasatinib, GDC-0834, PP2, SU6656 in conjunction with lymphoid malignancy, NHL, CLL, autoimmune disease, allergic disease, asthma, and rheumatoid arthritis. Conference proceedings from the previous 5 years of the American Society of Hematology, European Hematology Association, American Society of Clinical Oncology, and ACR/ARHP Annual Scientific Meetings were searched manually. Additional relevant publications were obtained by reviewing the references from the chosen articles.

EXPERT OPINION

The use of TKIs, especially inhibitors of Btk, Syk, and Lyn, is a promising new strategy for targeted treatment of B-cell lymphoid malignancies, autoimmune disorders and allergic diseases. However, definitive data from ongoing and future clinical trials will aid in better defining the status of TKIs in the treatment of these disorders.

Targeting Mantle Cell Lymphoma with Anti-SYK Nanoparticles

The pentapeptide mimic 1,4-bis(9-O-dihydroquinidinyl)phthalazine / hydroquinidine 1,4-phathalazinediyl diether ("compound 61") (C-61) is the first reported inhibitor targeting the P-site of SYK. Here we report a nanotechnology platform to target C-61 to mantle cell lymphoma (MCL) cells. Liposomal nanoparticles (NP) loaded with C-61 were prepared using the standard thin film evaporation method. The entrapment of C-61 was obtained using the pH gradient procedure with lactobionic acid (LBA) being used as a low pH buffer inside the NP. Formulation F6A was selected as a lead candidate for further biological testing. The average diameter, zeta potential and C-61 content of the F6A NP was 40 nm, 0.1 mV, and 12.6 mg/ml, respectively. F6A induces apoptosis in SYK⁺ but not SYK^- leukemia/lymphoma cells. We also evaluated the cytotoxic activity of F6A in the context of an in vitro artificial bone marrow assay platform based on a 3D scaffold with inverted colloidal crystal geometry mimicking the structural topology of actual bone marrow matrix. The ability of C-61 to induce apoptosis in ALL-1 cells was not adversely affected by the scaffolds. F6A, but not the drug-free NP formulation F6B, caused apoptosis of MCL cell lines MAVER-1 and MINO within 24h. Further development of rationally designed SYK inhibitors and their nanoscale formulations may provide the foundation for therapeutic innovation against a broad spectrum of lymphoid malignancies, including MCL.

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 48 h 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.