Advances in treatment of chronic myelogenous leukemia--new treatment options with tyrosine kinase inhibitors

Alterations in cellular metabolisms after TKI therapy for Philadelphia chromosome-positive leukemia in children: A review

Incidence rates of chronic myeloid leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) are lower but more aggressive in children than in adults due to different biological and host factors. After the clinical application of tyrosine kinase inhibitor (TKI) blocking BCR/ABL kinase activity, the prognosis of children with CML and Ph+ ALL has improved dramatically. Yet, off-target effects and drug tolerance will occur during the TKI treatments, contributing to treatment failure. In addition, compared to adults, children may need a longer course of TKIs therapy, causing detrimental effects on growth and development. In recent years, accumulating evidence indicates that drug resistance and side effects during TKI treatment may result from the cellular metabolism alterations. In this review, we provide a detailed summary of the current knowledge on alterations in metabolic pathways including glucose metabolism, lipid metabolism, amino acid metabolism, and other metabolic processes. In order to obtain better TKI treatment outcomes and avoid side effects, it is essential to understand how the TKIs affect cellular metabolism. Hence, we also discuss the relevance of cellular metabolism in TKIs therapy to provide ideas for better use of TKIs in clinical practice.

Unilateral Macular Choroidal Neovascularization; a Rare Manifestation in Chronic Myelogenous Leukemia

Purpose:

To report a case of chronic myelogenous leukemia (CML) treatment with imatinib mesylate in the remission phase who developed unilateral macular choroidal neovascularization (CNV).

Methods:

A 45-year-old male marketer with a 5-year history of CML treated with imatinib mesylate presented with 2 months history of progressive vision loss and metamorphopsia in the right eye.

Results:

Fundus examination of the right eye revealed grey-white elevated retinal lesion with indistinct borders in the macula and retinal telangiectasia in the temporal macula. Fluorescein angiography (FA) and optical coherence tomography angiography (OCTA) confirmed the presence of CNV in the right eye. After treatment with anti-vascular endothelial growth factor (anti-VEGF), macular CNV regressed significantly.

Conclusion:

Macular CNV must be kept in mind as a rare ophthalmic manifestation of patients with CML under treatment with imatinib even in the remission phase.

Targeting Kaposi's Sarcoma-Associated Herpesvirus ORF21 Tyrosine Kinase and Viral Lytic Reactivation by Tyrosine Kinase Inhibitors Approved for Clinical Use

Kaposi's sarcoma-associated herpesvirus (KSHV) is the cause of three human malignancies: Kaposi's sarcoma, primary effusion lymphoma, and the plasma cell variant of multicentric Castleman disease. Previous research has shown that several cellular tyrosine kinases play crucial roles during several steps in the virus replication cycle. Two KSHV proteins also have protein kinase function: open reading frame (ORF) 36 encodes a serine-threonine kinase, while ORF21 encodes a thymidine kinase (TK), which has recently been found to be an efficient tyrosine kinase. In this study, we explore the role of the ORF21 tyrosine kinase function in KSHV lytic replication. By generating a recombinant KSHV mutant with an enzymatically inactive ORF21 protein, we show that the tyrosine kinase function of ORF21/TK is not required for the progression of the lytic replication in tissue culture but that it is essential for the phosphorylation and activation to toxic moieties of the antiviral drugs zidovudine and brivudine. In addition, we identify several tyrosine kinase inhibitors, already in clinical use against human malignancies, which potently inhibit not only ORF21 TK kinase function but also viral lytic reactivation and the development of KSHV-infected endothelial tumors in mice. Since they target both cellular tyrosine kinases and a viral kinase, some of these compounds might find a use in the treatment of KSHV-associated malignancies.IMPORTANCE Our findings address the role of KSHV ORF21 as a tyrosine kinase during lytic replication and the activation of prodrugs in KSHV-infected cells. We also show the potential of selected clinically approved tyrosine kinase inhibitors to inhibit KSHV TK, KSHV lytic replication, infectious virion release, and the development of an endothelial tumor. Since they target both cellular tyrosine kinases supporting productive viral replication and a viral kinase, these drugs, which are already approved for clinical use, may be suitable for repurposing for the treatment of KSHV-related tumors in AIDS patients or transplant recipients.

Cellular and molecular alterations induced by low‑dose fisetin in human chronic myeloid leukemia cells

The present study aimed to evaluate the cellular and molecular effects of low concentrations of the flavonoid, fisetin, on K562 human chronic myeloid leukemia cells, in the context of both potential anti-proliferative and anti-metastatic effects. Thiazolyl blue tetrazolium bromide assay, Trypan blue exclusion assay, Annexin V/propidium iodide test, cell cycle analysis, Transwell migration and invasion assays, the fluorescence staining of β-catenin and F-actin as well as reverse transcription-quantitative polymerase chain reaction were performed to achieve the research goal. Furthermore, the nature of the interaction between fisetin and arsenic trioxide in the K562 cells was analyzed according to the Chou-Talalay median-effect method. We found that low concentrations of fisetin had not only a negligible effect on the viability and apoptosis of the K562 cells, but also modulated the mRNA levels of selected metastatic-related markers, accompanied by an increase in the migratory and invasive properties of these cancer cells. Although some markers of cell death were significantly elevated in response to fisetin treatment, these were counterbalanced through anti-apoptotic and pro-survival signals. With decreasing concentrations of fisetin and arsenic trioxide, the antagonistic interactions between the 2 agents increased. On the whole, the findings of this study suggest that careful consideration should be taken when advising cancer patients to take fisetin as a dietary supplement and when considering fisetin as a potential candidate for the treatment of chronic myeloid leukemia. Further more detailed studies are required to confirm our findings.

CD117/c-kit in Cancer Stem Cell-Mediated Progression and Therapeutic Resistance

Metastasis is the primary cause of cancer patient morbidity and mortality, but due to persisting gaps in our knowledge, it remains untreatable. Metastases often occur as patient tumors progress or recur after initial therapy. Tumor recurrence at the primary site may be driven by a cancer stem-like cell or tumor progenitor cell, while recurrence at a secondary site is driven by metastatic cancer stem cells or metastasis-initiating cells. Ongoing efforts are aimed at identifying and characterizing these stem-like cells driving recurrence and metastasis. One potential marker for the cancer stem-like cell subpopulation is CD117/c-kit, a tyrosine kinase receptor associated with cancer progression and normal stem cell maintenance. Further, activation of CD117 by its ligand stem cell factor (SCF; kit ligand) in the progenitor cell niche stimulates several signaling pathways driving proliferation, survival, and migration. This review examines evidence that the SCF/CD117 signaling axis may contribute to the control of cancer progression through the regulation of stemness and resistance to tyrosine kinase inhibitors.

Synergistic Induction of Apoptosis by Quercetin and Curcumin in Chronic Myeloid Leukemia (K562) Cells

Chronic myeloid leukemia is a major hematopoietic malignancy characterized by expansion of myeloid cells. In this study, we have investigated whether quercetin, curcumin and their combination induce apoptosis and inhibit growth of K562 cells. We have observed that quercetin and curcumin combination induced apoptosis accompanied by increased ROS and decreased GSH levels as well as loss of mitochondrial membrane potential. Our mRNA and protein expression results suggested that cytochrome c was released from mitochondria causing PARP and caspase-9 cleavages, the hallmarks of mitochondrial apoptotic pathway. We believe that triggering of apoptosis is mostly via mitochondrial pathway and ROS generation may induce impairment of mitochondrial membrane potential. The use of quercetin and curcumin combination potentiates individual apoptotic effects of the polyphenols and reduces their effective dose thereby preventing potential toxic effects on normal cells. Additional preclinical studies and clinical trials are certainly required to further validate their usefulness as potent anticancer agents.

Cryptotanshinone acts synergistically with imatinib to induce apoptosis of human chronic myeloid leukemia cells

Imatinib resistance has emerged as a significant clinical problem in chronic myeloid leukemia (CML) treatment. In this study, we investigated the effect and mechanism of combination treatment with imatinib and cryptotanshinone (CPT) in CML cells. Cotreatment with imatinib and CPT showed a significant synergistic killing effect in both imatinib sensitive and resistant CML cell lines, as well as primary CML cells. Furthermore, combination treatment induced apoptosis significantly, as indicated by increases in apoptotic cell fraction and activities of proapoptotic proteins. Subsequent studies revealed that CPT significantly inhibited Bcr/Abl protein expression, as well as phosphorylation expression levels of signal transducer and activator of transcription 3 (STAT3), mammalian target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E (eIF4E), which are critical mediators of Bcr/Abl transformation. Furthermore, CPT in combination with imatinib dramatically decreased the activity of the Bcr/Abl pathway in both K562 and K562-R cells. Our results demonstrated that CPT increased imatinib-induced apoptosis in a Bcr/Abl dependent manner, suggesting a novel strategy for the treatment of CML.

Geminin overexpression promotes imatinib sensitive breast cancer: a novel treatment approach for aggressive breast cancers, including a subset of triple negative

Breast cancer is the second leading cause of cancer-related deaths in women. Triple negative breast cancer (TNBC) is an aggressive subtype that affects 10–25% mostly African American women. TNBC has the poorest prognosis of all subtypes with rapid progression leading to mortality in younger patients. So far, there is no targeted treatment for TNBC. To that end, here we show that c-Abl is one of several tyrosine kinases that phosphorylate and activate geminin’s ability to promote TNBC. Analysis of >800 breast tumor samples showed that geminin is overexpressed in ∼50% of all tumors. Although c-Abl is overexpressed in ∼90% of all tumors, it is only nuclear in geminin overexpressing tumors. In geminin-negative tumors, c-Abl is only cytoplasmic. Inhibiting c-Abl expression or activity (using imatinib or nilotinib) prevented geminin Y150 phosphorylation, inactivated the protein, and most importantly converted overexpressed geminin from an oncogene to an apoptosis inducer. In pre-clinical orthotopic breast tumor models, geminin-overexpressing cells developed aneuploid and invasive tumors, which were suppressed when c-Abl expression was blocked. Moreover, established geminin overexpressing orthotopic tumors regressed when treated with imatinib or nilotinib. Our studies support imatinib/nilotonib as a novel treatment option for patients with aggressive breast cancer (including a subset of TNBCs)-overexpressing geminin and nuclear c-Abl.

An adaptive Src-PDGFRA-Raf axis in rhabdomyosarcoma

Alveolar rhabdomyosarcoma (aRMS) is a very aggressive sarcoma of children and young adults. Our previous studies have shown that small molecule inhibition of Pdgfra is initially very effective in an aRMS mouse model. However, slowly evolving, acquired resistance to a narrow-spectrum kinase inhibitor (imatinib) was common. We identified Src family kinases (SFKs) to be potentiators of Pdgfra in murine aRMS primary cell cultures from mouse tumors with evolved resistance in vivo in comparison to untreated cultures. Treating the resistant primary cell cultures with a combination of Pdgfra and Src inhibitors had a strong additive effect on cell viability. In Pdgfra knockout tumors, however, the Src inhibitor had no effect on tumor cell viability. Sorafenib, whose targets include not only PDGFRA but also the Src downstream target Raf, was effective at inhibiting mouse and human tumor cell growth and halted progression of mouse aRMS tumors in vivo. These results suggest that an adaptive Src-Pdgfra-Raf-Mapk axis is relevant to PDGFRA inhibition in rhabdomyosarcoma.

Galectin-3 (Gal-3) induced by leukemia microenvironment promotes drug resistance and bone marrow lodgment in chronic myelogenous leukemia

Bone marrow (BM) microenvironment (BMME) constitutes the sanctuary for leukemic cells. In this study, we investigated the molecular mechanisms for BMME-mediated drug resistance and BM lodgment in chronic myelogenous leukemia (CML). Gene-expression profile as well as signal pathway and protein analyses revealed that galectin-3 (Gal-3), a member of the β-gal-binding galectin family of proteins, was specifically induced by coculture with HS-5 cells, a BM stroma cell-derived cell line, in all five CML cell lines examined. It was also found that primary CML cells expressed high levels of Gal-3 in BM. Enforced expression of Gal-3 activated Akt and Erk, induced accumulation of Mcl-1, and promoted in vitro cell proliferation, multidrug resistance to tyrosine kinase inhibitors for Bcr-Abl and genotoxic agents as a result of impaired apoptosis induction, and chemotactic cell migration to HS-5-derived soluble factors in CML cell lines independently of Bcr-Abl tyrosine kinase. The conditioned medium from Gal-3-overexpressing CML cells promoted in vitro cell proliferation of CML cells and HS-5 cells more than did the conditioned medium from parental cells. Moreover, the in vivo study in a mice transplantation model showed that Gal-3 overexpression promoted the long-term BM lodgment of CML cells. These results demonstrate that leukemia microenvironment-specific Gal-3 expression supports molecular signaling pathways for disease maintenance in BM and resistance to therapy in CML. They also suggest that Gal-3 may be a candidate therapeutic target to help overcome BMME-mediated therapeutic resistance.

c-Abl and Arg are activated in human primary melanomas, promote melanoma cell invasion via distinct pathways, and drive metastatic progression

Despite 35 years of clinical trials, there is little improvement in 1-year survival rates for patients with metastatic melanoma, and the disease is essentially untreatable if not cured surgically. The paucity of chemotherapeutic agents that are effective for treating metastatic melanoma indicates a dire need to develop new therapies. Here, we found a previously unrecognized role for c-Abl and Arg in melanoma progression. We demonstrate that the kinase activities of c-Abl and Arg are elevated in primary melanomas (60%), in a subset of benign nevi (33%) and in some human melanoma cell lines. Using siRNA and pharmacological approaches, we show that c-Abl/Arg activation is functionally relevant because it is requiredfor melanoma cell proliferation, survival and invasion. Significantly, we identify the mechanism by which activated c-Abl promotes melanoma invasion by showing that it transcriptionally upregulates matrix metalloproteinase-1 (MMP-1), and using rescue approaches we demonstrate that c-Abl promotes invasion through a STAT3 → MMP-1 pathway. Additionally, we show that c-Abl and Arg are not merely redundant, as active Arg drives invasion in a STAT3-independent manner, and upregulates MMP-3 and MT1-MMP, in addition to MMP-1. Most importantly, c-Abl and Arg not only promote in vitro processes important for melanoma progression, but also promote metastasis in vivo, as inhibition of c-Abl/Arg kinase activity with the c-Abl/Arg inhibitor, nilotinib, dramatically inhibits metastasis in a mouse model. Taken together, these data identify c-Abl and Arg as critical, novel, drug targets in metastatic melanoma, and indicate that nilotinib may be useful in preventing metastasis in patients with melanomas harboring active c-Abl and Arg.

Disruption of Bcr-Abl coiled coil oligomerization by design

Oligomerization is an important regulatory mechanism for many proteins, including oncoproteins and other pathogenic proteins. The oncoprotein Bcr-Abl relies on oligomerization via its coiled coil domain for its kinase activity, suggesting that a designed coiled coil domain with enhanced binding to Bcr-Abl and reduced self-oligomerization would be therapeutically useful. Key mutations in the coiled coil domain of Bcr-Abl were identified that reduce homo-oligomerization through intermolecular charge-charge repulsion yet increase interaction with the Bcr-Abl coiled coil through additional salt bridges, resulting in an enhanced ability to disrupt the oligomeric state of Bcr-Abl. The mutations were modeled computationally to optimize the design. Assays performed in vitro confirmed the validity and functionality of the optimal mutations, which were found to exhibit reduced homo-oligomerization and increased binding to the Bcr-Abl coiled coil domain. Introduction of the mutant coiled coil into K562 cells resulted in decreased phosphorylation of Bcr-Abl, reduced cell proliferation, and increased caspase-3/7 activity and DNA segmentation. Importantly, the mutant coiled coil domain was more efficacious than the wild type in all experiments performed. The improved inhibition of Bcr-Abl through oligomeric disruption resulting from this modified coiled coil domain represents a viable alternative to small molecule inhibitors for therapeutic intervention.

How genetic variation affects patient response and outcome to therapy for psoriasis

Psoriasis is a prevalent chronic inflammatory condition that affects the skin. There are many treatments available for psoriasis but they are not universally effective and some have associated toxicities. Pharmacogenetics and pharmacogenomics explore the relationship between individual genetic variation and drug effect to allow targeted 'personalized' therapy for patients. There has been very limited pharmacogenetic research regarding psoriasis, with most limited to small retrospective case-control studies looking at single-nucleotide polymorphisms in candidate genes involved in drug pharmacokinetics. We review the pharmacogenetic investigation of treatments for psoriasis to date, including emerging pharmacogenomic studies. In addition, we discuss how such genetic data could be incorporated into routine clinical practice and future areas for development in this field.

Results of allogeneic hematopoietic stem cell transplantation for chronic myelogenous leukemia patients who failed tyrosine kinase inhibitors after developing BCR-ABL1 kinase domain mutations

Hematopoietic stem cell transplantation (HSCT) is effective therapy for patients with chronic myelogenous leukemia (CML) but is now mostly indicated for patients who develop resistance to tyrosine kinase inhibitors (TKIs), which can be associated with point mutations in BCR-ABL1. We reviewed the outcomes of imatinib-resistant CML patients (chronic phase, n = 34; accelerated phase [AP], n = 9; and blast phase [BP], n = 4) who underwent HSCT and had BCR-ABL1 sequencing. Mutations were found in 19 patients (40%); 15 of 19 had advanced CML (AP + BP + second chronic phase). Patients with mutations were more likely to transform to AP/BP at time of imatinib failure (69% vs 35%, P = .03). Forty-two patients (89%) responded to HSCT: 32 (68%) had at least a major molecular response. The 2-year event-free survival was 36% and 58% (P = .05) for the mutant and nonmutant groups, respectively; and the 2-year overall survival was 44% and 76% (P = .02), respectively. HSCT is an important salvage option for TKI-resistant patients with or without BCR-ABL1 mutations. Patients with mutations were more likely to develop advanced disease and had worse outcomes after HSCT. HSCT should be considered early for patients deemed to have a low probability of responding to second-generation TKI.