Treatment of chronic myeloid leukemia with imatinib mesylate

Combination of imatinib and clotrimazole enhances cell growth inhibition in T47D breast cancer cells

Imatinib mesylate (IM), a tyrosine kinase inhibitor, is used as targeted cancer therapy. However, mono-targeting by IM does not always achieve full tumor eradication and thus it is recommended to combine IM with other anticancer agents. Clotrimazole (CLT) is an antifungal azole derivative with promising anticancer effects due to inhibiting the activity of glycolytic enzymes. The present study aimed to evaluate the effect of combining CLT with IM on breast cancer cell line in an attempt to establish effective new combination. T47D human breast cancer cell line was treated with different concentrations of IM and/or CLT for 48 h. IM-CLT interaction was determined by isobologram equation and combination index. Cell viability was confirmed by measuring LDH activity. As indicators of glycolysis inhibition, the expression of hexokinase-2 (HK-2) and 6-phosphofructo-1-kinase (PFK-1) plus the activity of intracellular lactate dehydrogenase (LDH) and pyruvate kinase (PK) were determined. In addition, glucose consumption and adenosine triphosphate (ATP) production were measured. Moreover, nitric oxide (NO), vascular endothelial growth factor (VEGF) and hypoxia inducible factor-α (HIF-α) were also determined as they are modulators for glycolysis. This study demonstrated that IM or CLT synergistically inhibited cell growth in T47D as shown by combination and dose reduction indices. The combination of 15 μM IM and 20 μM CLT significantly decreased glucose consumption, activity of both PK and intracellular LDH, while increased leaked LDH, VEGF and NO in the medium compared to each drug alone. Furthermore the combination decreased gene expression of HK-2, PFK-1 and ATP content compared to the control. In conclusion, the synergistic effect of CLT on IM cytotoxicity in T47D cell line maybe mediated through inhibition of glycolysis and increasing both NO and VEGF. Further studies are required to confirm the efficiency and safety of this combination.

Biological properties of melanoma and endothelial cells after plasmid AMEP gene electrotransfer depend on integrin quantity on cells

The data on the biological responsiveness of melanoma and endothelial cells that are targeted by Antiangiogenic MEtargidin Peptide (AMEP) are limited; therefore, the antiproliferative, antimetastatic and antiangiogenic effects of AMEP were investigated in murine melanoma and human endothelial cells after plasmid AMEP gene electrotransfer into the cells in vitro. Plasmid AMEP, a plasmid coding for the disintegrin domain of metargidin targeting specific integrins, had cytotoxic and antiproliferative effects on murine melanoma and human endothelial cells. Among the metastatic properties of cells, migration, invasion and adhesion were investigated. Plasmid AMEP strongly affected the migration of murine melanoma and human endothelial cell lines and also affected the invasion of highly metastatic murine melanoma B16F10 and human endothelial cell lines. There was no effect on cell adhesion on Matrigel(TM) or fibronectin in all cell lines. The antiangiogenic effect was shown with tube formation assay, where human microvascular endothelial cell line (HMEC-1) proved to be more sensitive to plasmid AMEP gene electrotransfer than the human umbilical vein endothelial cell line (HUVEC). The study indicates that antiproliferative and antimetastatic biological responses to gene electrotransfer of plasmid AMEP in murine melanoma cells were dependent on the integrin quantity on melanoma cells and not on the expression level of AMEP. The strong antiangiogenic effect expressed in human endothelial cell lines was only partly dependent on the quantity of integrins and seemed to be plasmid AMEP dose dependent.

Apoptotic effect of imatinib on human colon adenocarcinoma cells: influence on actin cytoskeleton organization and cell migration

Imatinib mesylate (STI571) is the first member of a new class of agents that act by inhibiting specific tyrosine kinases, rather than killing all rapidly dividing cells. This drug is usually used in the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. It was recognized to inhibit activity of kinases such as Bcr/Abl, platelet-derived growth factor receptor, and c-kit. These proteins play important roles in cell growth, motility, and survival. Therefore, studies on the biological effects of imatinib on different cellular models are very important. Human colon adenocarcinoma LS180 cell line was used in the studies presented. Cells were exposed to 0.1-100 μM imatinib for 24 and 48 h. Dose-dependent decreases in cell viability and morphological changes were observed. Moreover, the apoptotic effect of imatinib (10 μM, 50 μM) after 24 h of exposure was demonstrated as evaluated by translocation of phosphatidylserine to external membrane leaflet and by increased activity of caspase-3. Special attention was focused on imatinib influence on actin cytoskeleton organization and migration ability of LS180 cells. Distinct alterations in actin cytoskeleton architecture occurred in response to drug treatment, accompanied by appearance of filamentous actin aggregates and decrease in actin polymerization state. These changes were correlated with remarkable decrease in cell migration capacity. In summary, our data clearly demonstrate that imatinib induces apoptosis and inhibits human colon adenocarcinoma cell migration. Therefore, this drug may have potential in colon cancer therapy in the future.

Changing paradigm of the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia

In the pre-imatinib era, the treatment outcome of patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(+) ALL) was dismal. Complete remission was generally achieved only in about 50% to 60% of patients, and allogeneic hematopoietic stem cell transplantation (allo-HSCT), when feasible in younger patients, was virtually the sole curative modality. Imatinib has changed the situation dramatically, however, in combination with conventional chemotherapy or with corticosteroid alone, producing about 95% complete remission and thus increasing the number of patients undergoing allo-HSCT. Currently, the overall survival of patients who have undergone allo-HSCT exceeds 50%, and a considerable proportion of patients for whom allo-HSCT is not feasible are predictably curable. The next question is how to prevent relapse, which is observed not only in more than half of patients for whom allo-HSCT is not feasible but also in a considerable number of patients after allo-HSCT. Thus, improvement of postremission therapy is crucial. Whether intensive chemotherapy with currently available cytotoxic drugs contributes to the prevention of relapse is questionable, because intensive chemotherapy alone in the pre-imatinib era nearly always failed to cure this disease. Promising partners to be combined with imatinib or with a second-generation tyrosine kinase inhibitor (TKI) will be corticosteroids and vincristine. New TKIs such as dasatinib should be incorporated into the early phase of postremission therapy. Recognizing the small number of patients with Ph(+) ALL, intergroup or international studies are necessary to develop the best postremission therapy. In the near future, it is hoped that Ph(+) ALL will become one of the leukemias for which allo-HSCT is offered only for relapsed or extremely high-risk patients.

Evaluation of imatinib mesylate in the treatment of pulmonary arterial hypertension

Imatinib mesylate is a small molecule inhibitor that selectively inhibits the PDGF receptor kinase as well the cKIT and Abl kinases, among other targets. Various studies have implicated the PDGF pathway in the pathogenesis of pulmonary arterial hypertension (PAH). Inhibition with imatinib mesylate has shown efficacy in human case reports and experimental models of PAH. Results from a Phase II trial of imatinib mesylate in PAH did not meet the primary end point but showed improvement in several secondary end points and in a subgroup analysis. As suggested by this study as well as a few case reports, imatinib may be effective in a subset of patients with more severe disease. However, this remains to be further validated through a Phase III study, which is already underway. In conclusion, it appears that imatinib mesylate may hold promise as an adjunct drug in PAH therapy, especially since it is directed at a pathway not previously targeted.

Systematic antigenic profiling of hematopoietic antigens on ovarian carcinoma cells identifies membrane proteins for targeted therapy development

OBJECTIVE

We studied ovarian cancers for the expression of membrane markers of hematopoietic origin.

STUDY DESIGN

We used flow cytometry to systematically characterize the expression of more than 30 hematologic antigens on ovarian carcinoma cell lines and to assess their stability under estrogen exposure. The expression of the antigens was validated by a bioinformatics survey and immunohistochemical staining of ovarian cancer specimens.

RESULTS

Several antigens were expressed by the majority of the cells, such as CD15, CD71, and CD138, whereas others were found on small and distinct cellular subpopulations. The expression patterns of the different markers were unaffected by estrogen exposure, indicating their stability.

CONCLUSION

The antigens described in our work may serve as potential targets for new and existing targeted drugs.

Response prediction to a multitargeted kinase inhibitor in cancer cell lines and xenograft tumors using high-content tyrosine peptide arrays with a kinetic readout

Multitargeted kinase inhibitors have shown clinical efficacy in a range of cancer types. However, two major problems associated with these drugs are the low fraction of patients for which these treatments provide initial clinical benefit and the occurrence of resistance during prolonged therapy. Several types of predictive biomarkers have been suggested, such as expression level and phosphorylation status of the major targeted kinase(s), mutational status of the kinases involved and of key components of the downstream signaling cascades, and gene expression signatures. In this work, we describe the development of a response prediction platform that does not require prior knowledge of the relevant kinases targeted by the inhibitor; instead, a phosphotyrosine peptide profile using peptide arrays with a kinetic readout is derived in lysates in the presence and absence of a kinase inhibitor. We show in a range of cell lines and in xenograft tumors that this approach allows for the stratification of responders and nonresponders to a multitargeted kinase inhibitor.

Potential of imatinib mesylate as a novel treatment for pulmonary fibrosis

Pulmonary fibrosis is a disease characterized by progressive scarring of the lungs, with idiopathic pulmonary fibrosis (IPF) being the most aggressive form. The diagnosis of IPF is made after other conditions are excluded and is based on a characteristic clinical presentation, radiographic features and, sometimes, pathologic specimen. Existing IPF drug regimens, including corticosteroids and cytotoxic medications, are generally ineffective. To date, only lung transplantation has been shown to improve mortality in carefully selected patients. Multiple therapeutic agents have been investigated but none have proven to be successful. Novel drugs are constantly being sought in an attempt to find a therapy that halts or reverses this disease. Imatinib mesylate is used for chronic myelogenous leukemia and gastrointestinal stromal tumors. It also has antifibrotic properties, as demonstrated in several studies using mouse models of pulmonary fibrosis. Currently, trials are underway to investigate its efficacy in human subjects with IPF.

Secondary mutations in the kinase domain of the KIT gene are predominant in imatinib-resistant gastrointestinal stromal tumor

Although imatinib showed high activity for advanced gastrointestinal stromal tumor (GIST) and improved the prognosis of GIST patients, resistance to the drug appears with prolonged use. Mechanisms of acquired resistance are still under investigation. In the present study, we carried out histologic and genetic analysis of 45 secondary resistant lesions obtained from 25 Japanese GIST patients treated with imatinib. All resistant lesions showed viable tumor cells expressing KIT protein, whereas imatinib-sensitive lesions did not. All pre-imatinib samples have KIT mutations either in exon 9 (n = 3) or exon 11 (n = 22), identified in the KIT gene of corresponding resistant tumors. In addition to primary mutations, 33 out of 45 tumors (73%) showed secondary KIT mutations in the kinase domain of the KIT gene. Secondary mutations are missense mutations and are mostly located in the kinase domains of the same allele to the primary mutations (cis-position). Resistant lesions showed monoclonal development of tumor cells. Taken together, additional cis-positioned mutations in the kinase domains are a major cause of secondary resistance to imatinib in Japanese GIST patients.

Novel dual targeting strategy with vandetanib induces tumor cell apoptosis and inhibits angiogenesis in malignant pleural mesothelioma cells expressing RET oncogenic rearrangement

Malignant pleural mesothelioma (MPM) is an aggressive malignancy with a poor prognosis, therefore development of novel effective therapies is urgent. In the present study, we investigated the therapeutic efficacy of vandetanib (ZD6474), an inhibitor of VEGFR-2, EGFR and RET tyrosine kinases, in an orthotopic model of MPM. We found that a human MPM cell line, EHMES-10, expressed RET/PTC3 oncogenic rearrangement and a large amount of VEGF. Vandetanib induced the apoptosis and inhibited the proliferation of EHMES-10 cells in vitro (IC(50)=0.3 microM). Once-daily oral treatment with vandetanib inhibited tumor angiogenesis, and reduced significantly the growth of thoracic tumors and the production of pleural effusions, resulting in the prolonged survival of mice in EHMES-10 orthograft model. In contrast, the selective EGFR tyrosine kinase inhibitor, gefitinib, had no effect against EHMES-10 cells both in vitro and in vivo. Our results suggest that using vandetanib to target RET-dependent tumor cell proliferation and survival and VEGFR-2-dependent tumor angiogenesis may be promising against MPM expressing RET oncogenic rearrangement and VEGF.

A systematic interaction map of validated kinase inhibitors with Ser/Thr kinases

Protein kinases play a pivotal role in cell signaling, and dysregulation of many kinases has been linked to disease development. A large number of kinase inhibitors are therefore currently under investigation in clinical trials, and so far seven inhibitors have been approved as anti-cancer drugs. In addition, kinase inhibitors are widely used as specific probes to study cell signaling, but systematic studies describing selectivity of these reagents across a panel of diverse kinases are largely lacking. Here we evaluated the specificity of 156 validated kinase inhibitors, including inhibitors used in clinical trials, against 60 human Ser/Thr kinases using a thermal stability shift assay. Our analysis revealed many unexpected cross-reactivities for inhibitors thought to be specific for certain targets. We also found that certain combinations of active-site residues in the ATP-binding site correlated with the detected ligand promiscuity and that some kinases are highly sensitive to inhibition using diverse chemotypes, suggesting them as preferred intervention points. Our results uncovered also inhibitor cross-reactivities that may lead to alternate clinical applications. For example, LY333'531, a PKCbeta inhibitor currently in phase III clinical trials, efficiently inhibited PIM1 kinase in our screen, a suggested target for treatment of leukemia. We determined the binding mode of this inhibitor by x-ray crystallography and in addition showed that LY333'531 induced cell death and significantly suppressed growth of leukemic cells from acute myeloid leukemia patients.

Plasma pharmacokinetics and CYP3A12-dependent metabolism of c-kit inhibitor imatinib in dogs

Imatinib is a highly selective tyrosine kinase inhibitor, and is used for the treatment of chronic myeloid leukaemia (CML) and gastrointestinal stromal tumours (GISTs) in humans. The aim of this study is to determine the in vitro and in vivo pharmacokinetics of imatinib in dogs and which cytochrome P450 (CYPs) contribute to its metabolism. Imatinib was administered orally or intravenously to dogs and the time of the peak concentration (T(max)) of imatinib was 4-9 h. The mean half-life was 622 +/- 368 min, and the AUC was 1256 +/- 809 microM * min after oral administration. The range of C0 of intravenously injected dogs was 12-24 microM. The half-life and AUC after intravenous injection were 206 +/- 112 min and 1026 +/- 371 microM * min, respectively. Recombinant system of dog CYP3A12 and CYP2C21 showed that CYP3A12 contributed to the metabolism of imatinib. The inhibition of CYP3A-dependent activity using a rat anti-CYP3A antibody or ketoconazole revealed that CYP3A12 plays a major role in the metabolism of imatinib in dog liver microsomes.

Molecular insight in cancer treatment and prevention

This article explores the impact of new insights in the biology of cancer on the treatment and the prevention of this disease. There are two types of targeted cancer treatment, afforded by the molecular profile of cancer. One concerns the use of agents targeted on a specific component of the cancer cells (e.g., CD20 in lymphoma) or on a specific survival function of the cancer cell (growth-factor-receptor interaction; transduction cascade). The other concerns the recognition of tumors that are more or less likely to benefit from cytotoxic chemotherapy according to their genomic or proteomic profile. Cancer prevention may benefit from new molecular insight in cancer biology as these processes allow early diagnosis of cancer, identification of patients at risk for cancer, and may provide intermediate markers for chemoprevention studies.