No abstract

Resistance to imatinib represents an important scientific and clinical issue in chronic myelogenous leukemia. In the present study, the effects of the novel inhibitor SKI-606 on various models of resistance to imatinib were studied. SKI-606 proved to be an active inhibitor of Bcr-Abl in several chronic myelogenous leukemia cell lines and transfectants, with IC 50 values in the low nanomolar range, 1 to 2 logs lower than those obtained with imatinib. Cells expressing activated forms of KIT or platelet-derived growth factor receptor (PDGFR), two additional targets of imatinib, were unaffected by SKI-606, whereas activity was found against PIM2. SKI-606 retained activity in cells where resistance to imatinib was caused by BCR-ABL gene amplification and in three of four Bcr-Abl point mutants tested. In vivo experiments confirmed SKI-606 activity in models where resistance was not caused by mutations as well as in cells carrying the Y253F, E255K, and D276G mutations. Modeling considerations attribute the superior activity of SKI-606 to its ability to bind a conformation of Bcr-Abl different from imatinib. (Cancer Res 2006; 66(23): 11314-22)

These data indicate that the continuous block of the oncogenic tyrosine kinase of Bcr/Abl protein is needed to produce important biologic effects in vivo.

The molecular pathogenesis of tumors arising from the thyroid follicular epithelial cells, including papillary (PTC) and follicular thyroid carcinoma (FTC), is only partially understood, and the role of tumor suppressor genes has not yet been assessed. The metallothionein (MT) gene family encodes a class of metal-binding proteins involved in several cellular processes, and their expression is often deregulated in human tumors. Recently, downregulation of MT gene expression in PTC has been reported, suggesting a possible oncosuppressor role of this gene family in the pathogenesis of thyroid tumors. To further explore this possibility, we performed expression and functional studies. Analysis of microarray data of thyroid tumors of different histologic types showed that several MT genes were downregulated with respect to normal tissue. The microarray data were corroborated by quantitative PCR experiments, showing downregulation of MTs in PTC and FTC, but to a greater extent in papillary carcinoma. The expression of MTs was also investigated at the protein level by immunohistochemistry; the results were consistent with the microarray data, showing general downregulation in tumor samples, which was more evident in PTC. The functional consequence of MT downregulation was addressed employing an experimental model made of the PTC-derived K1 cell line in which MT1G expression is repressed by promoter methylation. Restoration of MT1G expression by cDNA transfection affected growth rate and in vivo tumorigenicity of K1 cells, indicating an oncosuppressor role for MT1G in thyroid papillary tumorigenesis. Several tumor types, differing in biological and clinical behavior, originate from the thyroid epithelial follicular cells. They include well-differentiated, indolent papillary thyroid and follicular thyroid carcinomas (PTC and FTC), as well as extremely aggressive anaplastic carcinoma. 1 Studies performed in several laboratories, including ours, have demonstrated that distinct molecular events are associated with specific tumor types. 2 FTC is characterized by the PAX8/ PPARg rearrangement and activating mutations of RAS genes. 1 PTC is associated with rearrangements involving the RET and NTRK1 tyrosine kinase receptors, 2 and the V600E BRAF-activating mutation. [3][4][5] More recently, microarray studies have identified several genes that might be important in the molecular pathogenesis and the malignant progression of thyroid cancer and could be used as diagnostic or prognostic molecular markers. These candidate genes are involved in several different processes, such as cell adhesion, cell cycle progression, mitogenic control and tumorigenesis. [6][7][8][9][10] In spite of that, the molecular pathogenesis of thyroid cancer is still incomplete; in particular, a role of tumor suppressor genes has not yet been assessed. Metallothioneins (MTs) are low-molecular weight proteins of 6-7 kDa, with high content of cysteine (30%) and complete absence of aromatic amino acids and histidine 11 capable of binding heavy metals with hig...

Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted protein involved in several cellular processes, including proliferation, senescence and apoptosis. Loss of IGFBP7 expression is a critical step in the development of human tumors, including melanoma and colon cancer. By microarray gene expression studies, we have detected downregulation of IGFBP7 gene expression in follicular and papillary thyroid tumors in comparison with normal thyroid tissue. Evaluation of publicly available PTC microarray gene expression data sets confirmed, in a consistent fraction of tumors, the downregulation of IGFBP7 transcript levels. The functional consequence of IGFBP7 downregulation was addressed in the PTCderived NIM1 cell line in which IGFBP7 expression is repressed by promoter hypermethylation. Exposure to soluble IGFBP7 protein or restoration of IGFBP7 expression by complementary DNA transfection reduced growth rate, migration, anchorage-independent growth and tumorigenicity of NIM1 cells. We show that the effects of IGFBP7 are related to apoptosis. Our data suggest that loss of IGFBP7 expression has a functional role in thyroid carcinogenesis, and it may represent a possible basis for therapeutic strategies.

Adenovirus-transduced CD34 IntroductionGenetically modified stem/progenitor cells represent an innovative approach for delivery of anticancer molecules. 1,2 Because of their homing properties, systemically injected stem/progenitor cells could infiltrate both primary and metastatic tumor sites, thus allowing tumor-specific targeting 3-9 and potentially overcoming limitations inherent to the pharmacokinetic profile of soluble drugs. [10][11][12] Soluble tumor necrosis factor (TNF)-related apoptosisinducing ligand (sTRAIL) is a proapoptotic member of the TNF superfamily of death receptor ligands. A variety of preclinical data show that sTRAIL is a cancer cell-specific molecule exerting a remarkable antitumor activity in vitro [13][14][15][16][17][18] and in vivo in athymic nude mice or in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. 13,19,20 Phase 1/2 clinical trials have demonstrated a good toxicity profile for sTRAIL but limited evidence of antitumor activity probably because of short exposure of tumor cells to low drug concentrations. 21 Because of sTRAIL's short half-life, 13,20,22 it seems unlikely that the recommended sTRAIL dose of 8 mg/kg body weight will allow prolonged exposure of tumor cells at high drug concentrations. 21 Strategies to enhance the therapeutic activity of sTRAIL include combining it with conventional chemotherapy 23 or with new agents, such as histone deacetylase inhibitors that up-regulate TRAIL-R1 and/or TRAIL-R2, resulting in a synergistic induction of apoptosis in both sTRAIL-sensitive and -resistant tumor cells. 24 Alternatively, cell-based vehiculation of the full-length, membranebound (m)TRAIL has been proposed. 11 Neural or mesenchymal stem cell-mediated mTRAIL delivery has been investigated in solid tumors. 9,[25][26][27][28] More recently, we demonstrated that intravenous injection of mTRAIL-expressing CD34 ϩ cells (CD34-TRAIL ϩ cells) efficiently act as mTRAIL-presenting vehicles and exert a potent antitumor activity in NOD/SCID mice bearing systemic multiple myeloma and non-Hodgkin lymphoma xenografts. [29][30][31] Using a subcutaneous multiple myeloma model in NOD/SCID mice, the present study aimed at investigating the antitumor mechanism(s) of mTRAIL-expressing cells by analyzing homing properties of CD34-TRAIL ϩ cells as well as the degree and distribution of tumor cell death and tumor vascular damage. To analyze the antivascular activity of CD34-TRAIL ϩ cells, we used an in vivo staining assay of tumor vasculature. 32 The imaging software ImageJ (National Institutes of Health), equipped with appropriately designed macros to specifically quantify parameters of tumor cell and tumor vascular damage, allowed the processing The online version of this article contains a data supplement.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. For personal use only. on May 11, 2018. by guest www.blood...

Papillary thyroid carcinoma (PTC) arises from the thyroid follicular epithelium and represents the most frequent thyroid malignancy. PTC is associated with gene rearrangements generating RET/PTC and TRK oncogenes, and to the BRAFV600E activating point mutation. A role of tumor-suppressor genes in the pathogenesis of PTC has not been assessed yet. The tissue inhibitor of metalloproteinase-3 (TIMP3) gene, encoding a metalloproteinases inhibitor and capable of inhibiting growth, angiogenesis, invasion and metastasis of several cancers, was found to be silenced by promoter methylation in a consistent fraction of PTCs, in association with tumor aggressiveness and BRAFV600E mutation, thus suggesting an oncosuppressor role. To explore this possibility, in this study we performed gene expression and functional studies. Analysis of gene expression data produced in our laboratory as well as meta-analysis of publicly available data sets confirmed the downregulation of TIMP3 gene expression in PTC with respect to normal thyroid. The functional consequences of TIMP3 downregulation were investigated in the PTC-derived NIM1 cell line, in which the expression of TIMP3 is silenced. Restoration of TIMP3 expression by exposure to soluble TIMP3 protein or by complementary DNA transfection had no effect on the growth rate of NIM1 cells. Instead, it affected the adhesive, migratory and invasive capabilities of NIM1 cells by modulating several proteins involved in these processes. A striking effect was observed in vivo, as TIMP3 reduced the tumorigenicity of NIM1 cells by repressing angiogenesis and macrophage infiltration. Our data indicate that the loss of TIMP3 expression exerts a functional role in the pathogenesis of PTC.

Retinoids are natural and synthetic analogs of vitamin A involved in the control of cell differentiation and proliferation. In animal models these compounds can prevent epithelial and mesenchymal tumor formation and inhibit the growth of different tumors (Moon et al., 1994). The inhibition of cell proliferation can be due to a differentiative effect, leading to loss of the neoplastic phenotype andfor to a direct effect on cell proliferation (Gudas, 1992). These compounds have been shown to exert their effects through retinoic acid nuclear receptors (RAR and RXR), which are ligand-regulated transcriptional factors. Following retinoid binding, RARs and RXRs transactivate the expression of genes presumably involved in the synthesis of proteins that promote differentiation and/or inhibit cell growth (Pemrick el al., 1994).Recently, particular attention has been directed to fenret- The neoplasm is a major cause of female cancer death since most women at diagnosis have advanced-stage disease and a poor prognosis. The major obstacle in the curative treatment is that the cancer is often resistant to chemotherapy. Preliminary clinical data suggest a chemopreventive effect of 4HPR in ovarian cancer since a significant reduction of ovarian cancer incidence has been observed during treatment with 4HPR in breast cancer patients (De Palo et aL, 1995). In pre-clinical studies we have shown that 4HPR has a therapeutic effect in a human ovarian carcinoma xenograft, the IGROV-1 tumor, and that it potentiates the activity of cisplatin in the treatment of the same tumor (Formelli and Cleris, 1993).We studied the effects of 4HPR on the in vitro growth of human ovarian carcinoma cell lines to investigate the mechanisms of the anti-proliferative activity of the retinoid. We examined whether the growth inhibition caused by 4HPR is related to perturbations of the cell cycle and to induction of apoptosis. Moreover, since the investigated ovarian carcinoma cell lines show different sensitivities to 4HPR, we measured intracellular drug content and RAR mRNA expression to establish possible correlations with cell sensitivity. Finally, we tested whether it is possible, through a combined treatment with 4HPR, to potentiate the activity of cisplatin, the most effective cytotoxic agent used in clinical therapy of ovarian carcinoma. MATERIAL AND METHODS Cell lines, culture conditions and drugsThe following human ovarian carcinoma cell lines were