Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A phase I clinical trial evaluating the toxicity of orally-administered imatinib mesylate was performed in 9 tumor-bearing cats. Imatinib is a small molecule, tyrosine kinase inhibitor, which selectively blocks the function of overexpressed proteins associated with various malignancies. Cats included in the study had diagnoses of fibrosarcoma, squamous cell carcinoma, and mast cell tumor, and each cat was staged using CBC and serum biochemistry; urinalysis, thoracic radiographs, and abdominal ultrasonography were performed in some cats. Most cats were treated previously by surgery, radiation therapy, chemotherapy, or some combination of these treatments. None of the cats received any concurrent chemotherapy. Six cats were treated with imatinib mesylate at 1-2 mg/kg PO q24h. Dose escalations were made to 2, 4, and 10 mg/kg PO q24h in 5 cats. Two cats started therapy at 10 mg/kg PO q24h, and 1 cat started therapy at 15 mg/kg PO q24h; all 3 cats remained at these dosages. No signs of toxicity, as evaluated by CBC and serum biochemistry, were noted in 8 of the 9 cats, and minimal gastrointestinal toxicity was observed. Due to the low frequency of adverse effects, further evaluation of imatinib is ongoing at a dosage of 10 mg/kg PO q24h.
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PMID:A phase I clinical trial evaluating imatinib mesylate (Gleevec) in tumor-bearing cats. 1635 81

Several activating mutations in the cKIT receptor tyrosine kinase are associated with the development and progression of gastrointestinal stromal tumors (GIST). Treatment of GIST with the tyrosine kinase inhibitor imatinib (Gleevec, STI571; Novartis, Basel, Switzerland) increases patient survival. However, many patients develop resistance to imatinib following initial responses. We sequenced cKIT exons from two patients with GIST after the development of imatinib resistance, revealing a point mutation in kinase domain I (exon 13), Val654Ala, which has been associated previously with relapse and resistance. Molecular modeling of cKIT-imatinib complexes shows that this residue is located in the drug-binding site and that the Val654Ala mutation disrupts drug binding by removing hydrophobic contacts with the central diaminophenyl ring of imatinib. Loss of these contacts results in a destabilizing effect on two key hydrogen bonds between imatinib and Asp310 and Thr670 of cKIT. Calculations based on published crystallography data show an estimated destabilization energy of 2.25 kcal/mol in the Val654Ala cKIT compared with wild type. When present on the same cKIT allele as an oncogenic mutation, the Val654Ala mutation abolishes imatinib-mediated inhibition of cKIT phosphoactivation in vitro. These results highlight some of the structural and functional consequences of the Val654Ala mutation in relapsing imatinib-resistant GIST and emphasize the importance of tumor genetics in drug development and patient-specific cancer treatment regimens.
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PMID:Imatinib binding and cKIT inhibition is abrogated by the cKIT kinase domain I missense mutation Val654Ala. 1637 16

Fourteen patients with metastatic renal cell carcinoma (RCC) were treated on a Phase II trial with imatinib. Eligible patients had histologically confirmed RCC, metastatic and measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST), Karnofsky performance status (KPS) of at least 70%, life expectancy of more than 3 months, and adequate hematological, renal, and liver function. Imatinib was given orally at a dose of 400 mg bid. The most common toxicities were Grade II/III nausea (28%) and Grade II renal insufficiency (14%). All patients had tumor tested by immunohistochemistry (IHC) for KIT protein (CD117, DAKO). One tumor (7%) demonstrated strong, diffuse expression and the rest were negative. No complete or partial responses were observed in 12 evaluable patients treated with imatinib.
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PMID:Phase II trial of imatinib (Gleevec) in patients with metastatic renal cell carcinoma. 1638 Aug 35

Gleevec, a selective tyrosine kinase inhibitor, retarded the growth of anaplastic thyroid cancer cell lines in vitro and in vivo through selective inhibition of ABL tyrosine kinase activity. In the present study, we investigated the ability of Gleevec to modulate the in vitro and in vivo radiation response of anaplastic thyroid cancer cells. Cell growth assays, colony formation assays and xenograft models were used to quantify the radiosensitizing effect of Gleevec in cells of the anaplastic thyroid cancer cell lines ARO and FRO. FACS, Western blotting and histochemical techniques were employed to study the mechanisms of radiation response after exposure to Gleevec. Gleevec (7.0 microM) increased the anti-proliferative effect of radiation on the growth ARO and FRO cells in vitro. Clonogenic analysis demonstrated that Gleevec reduced cell survival after irradiation. Gleevec combined with radiation produced an increase in tumor growth inhibition compared to treatment with either modality alone in mice bearing anaplastic thyroid cancer xenografts. The drug suppressed radiation-induced ABL activation and promoted CDKN1A (p21(cip1)) accumulation in irradiated anaplastic thyroid cancer cells. Gleevec had an additional effect on radiation-induced apoptosis in cells of both cell lines and potentiated the induction of terminal growth arrest accompanied by the expression of senescence-associated beta-galactosidase. The antitumor effect of Gleevec is potentiated in adjunctive therapy with radiation not only due to inhibition of proliferative cell growth with transient cell cycle arrest and apoptosis, but also due to the terminal growth arrest associated with senescence, suggesting that tumor cell senescence is a mechanism for tumor targeting therapy in combination with ionizing radiation.
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PMID:Inhibition of ABL tyrosine kinase potentiates radiation-induced terminal growth arrest in anaplastic thyroid cancer cells. 1639 60

The introduction of imatinib, an orally administered inhibitor of the KIT receptor tyrosine kinase, is prompting revision of the management algorithms that have traditionally guided the treatment of gastrointestinal stromal tumor (GIST). Historically, patients with GISTs have had substantial rates of relapse as well as limited long-term survival even after complete surgical resection of a primary tumor. Imatinib has been shown to induce durable tumor responses in more than half of the patients with malignant metastatic or unresectable GISTs and to halt disease progression in an additional third. These encouraging results have led to the initiation of clinical trials of imatinib as an adjuvant or neoadjuvant therapy with surgery. Until relevant data are reported to provide definitive direction for the management of operable or potentially operable GISTs, treatment decisions must be made on the basis of the available evidence and clinical experience with imatinib. This paper presents selected case studies describing approaches to the combined use of surgery and systemic therapy that have been applied in the treatment of individual GIST patients. The management of GIST in these cases required a coordinated, multidisciplinary approach involving medical oncologists, diagnostic radiologists, gastroenterologists, surgeons, and pathologists.
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PMID:Management of gastrointestinal stromal tumors in the imatinib era: selected case studies. 1640 9

Fanconi's anemia (FA) is an autosomal recessive inherited syndrome with a predisposition to malignancy. The association between FA and solid pediatric tumors is extremely rare. The authors report a rare case of VACTERL syndrome associated with FA and multiple solid pediatric tumors occurring in a very young girl. This child had numerous congenital anomalies (horseshoe kidney, cerebella hypoplasia, microcephaly, sacral agenesis) and esophageal atresia, which was repaired in neonatal period. Such association led quickly to the diagnosis of FA. At age of 11 months, she developed simultaneously a renal tumor in a horseshoe kidney and bilateral adrenal tumors. The left adrenal mass was removed, and partial nephrectomy was performed. Histological analysis concluded to adrenal neuroblastoma and nephroblastoma. We also evaluated the c-kit expression in these tumors to propose a therapeutic alternative to chemotherapy by oral agent STI-571 (Gleevec; Novartis, East Hanover, NJ). Strong cytoplasmic immunostaining of c-kit was found in both tumors. Unfortunately, she quickly developed a posterior cerebellar fossa tumor and died 1 month later. This clinical situation is very rare but suggests that young patients with FA and solid pediatric tumors may belong to a particular subgroup of FA. Further studies are necessary to test if STI-571 treatment could be efficient in such patients with pediatric tumors.
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PMID:Bilateral adrenal neuroblastoma and nephroblastoma occurring synchronously in a child with Fanconi's anemia and VACTERL syndrome. 1641 81

Imatinib (STI571, Gleevec/Glivec) and other small-molecule tyrosine kinase inhibitors are highly effective in the treatment of chronic myeloid leukemia (CML), gastrointestinal stromal tumors and, for example, eosinophilia-associated chronic myeloproliferative disorders. This molecularly targeted approach disrupts abnormal tyrosine kinase dependent signalling pathways, thus providing a preferred treatment option for selected neoplastic disorders with activating mutations of Abelson-, Abl-related-, Kit-, and platelet-derived growth factor receptor A and B genes. Loss of response to imatinib may be due to an acquired resistance of emerging mutant tumor cell clones. Therapy is generally well tolerated. However, toxicities including edema, skin rashes, fatigue, nausea and myelosuppression have been reported. Philadelphia/Bcr-Abl-negative clonal chromosomal abnormalities may develop. Bone marrow trephines obtained from CML patients in complete remission with prolonged pancytopenia secondary to imatinib generally show marrow hypoplasia. Morphological features may be in keeping with either aplastic anemia or myelodysplasia developing in Philadelphia-negative hematopoiesis. Single or multilineage myelodysplasia may be accompanied by an excess of blasts and rarely evolves into acute leukemia in CML patients. Severe adverse hematological effects of imatinib are extremely rare. Current questions involve the molecular mechanisms of hematological side effects of tyrosine kinase inhibitors with special regard to the emergence of distinct aberrant clones.
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PMID:[Hematological side effects of tyrosine kinase inhibition using imatinib]. 1642 5

Imatinib-refractory chronic myelogenous leukemia (CML) patients can experience long-term disease-free survival with myeloablative therapy and allogeneic hematopoietic cell transplantation; however, associated complications carry a significant risk of mortality. Transplantation of autologous hematopoietic cells has a reduced risk of complications, but residual tumor cells in the autograft may contribute to relapse. Development of methods for purging tumor cells that do not compromise the engraftment potential of the normal hematopoietic cells in the autograft has been a long-standing goal. Since primitive CML cells differentiate more rapidly in vitro than their normal counterparts and are also preferentially killed by mafosfamide and imatinib, we examined the purging effectiveness on CD34(+) CML cells using a strategy that combines a brief exposure to imatinib (0.5-1.0 microM for 72 h) and then mafosfamide (30-90 microg/ml for 30 min) followed by 2 weeks in culture with cytokines (100 ng/ml each of stem cell factor, granulocyte colony-stimulating factor and thrombopoietin). Treatment with 1.0 microM imatinib, 60 microg/ml mafosfamide and 14 days of culture with cytokines eliminated BCR-ABL(+) cells from chronic phase CML patient aphereses, while preserving normal progenitors. This novel purging strategy may offer a new approach to improving the effectiveness of autologous transplantation in imatinib-refractory CML patients.
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PMID:A novel triple purge strategy for eliminating chronic myelogenous leukemia (CML) cells from autografts. 1643 11

Imatinib is a tyrosine kinase inhibitor with activity in gastrointestinal stromal tumor and a variety of other solid and hematological malignancies. Studies in vitro and in a mouse model suggested that the imatinib might also be active in malignant Leydig cell tumor. We report on the--to our knowledge--first treatment experiment with imatinib in a patient with metastatic Leydig cell tumor. Unfortunately, the tumor progressed during treatment.
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PMID:Lack of efficacy of imatinib in a patient with metastatic Leydig cell tumor. 1645 Jan 63

Gastrointestinal stromal tumors (GIST) are characterized by a strong KIT receptor activation most often resulting from KIT mutations. In a smaller subgroup of tumors without KIT mutations, analogous activating mutations are found in the platelet-derived growth factor receptor alpha (PDGFRalpha) gene. Both PDGFRalpha and KIT receptors are targets of the tyrosine kinase inhibitor imatinib (Glivec) which has improved the treatment of advanced GISTs significantly. However, a subgroup of tumors show a secondary progress under therapy with imatinib after initial response. One possible mechanism of secondary resistance is the development of newly acquired KIT mutations. In the present study, we evaluated the frequency of such secondary KIT mutations in a series of GIST patients in which tumor tissue was resected under treatment. We examined one to seven different tumor areas in 32 cases (total of 104 samples) and found up to four newly acquired KIT mutations in 14 patients (43.8%). These were always located in exons encoding the first or second tyrosine kinase domain (exon 13, 14, or 17). Mutations were found only in a subset of samples analyzed from each case whereas others retained the wild-type sequence in the same region. There was never more than one new mutation in the same sample. Consistent with a secondary clonal evolution, the primary mutation was always detectable in all samples from each tumor. According to our results, the identification of newly acquired KIT mutations in addition to the primary mutation is dependent on the number of tissue samples analyzed and has high implications for further therapeutic strategies.
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PMID:Polyclonal evolution of multiple secondary KIT mutations in gastrointestinal stromal tumors under treatment with imatinib mesylate. 1706


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