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Targeting aberrant signaling pathways: novel therapeutic approaches for the treatment of acute leukemia
No full textOver the last decades, a significant progress in the understanding of leukemogenesis has been achieved highlighting several of the molecular alterations responsible for leukemia cell proliferation and survival. Despite novel findings, advances in treatment of acute myeloid and lymphoblastic leukemia (AML, ALL) have been quite modest with the prognosis of patients remaining, generally, severe. Therefore, investigation has been prompted towards new targeted approaches focused on the aberrant networks that sustain blast proliferation, survival and drug resistance.
Phosphatidyl-inositol-3 kinases (PI3Ks) belong to a family of evolutionary conserved enzymes that regulates cell omeostasis by transducing signals from the microenvironment to the nucleus through protein kinases such as Akt and the mammalian target of rapamycin (mTOR). Deregulation of the PI3K/Akt/mTOR signaling has been associated with several human cancers, and its constitutive activation is frequently found in AML patients contributing to chemoresistance, disease progression and unfavorable outcome. Over the years, several small molecules that target the PI3K/Akt/mTOR signaling has been investigated showing potential therapeutic efficacy in AML alone and in combination with chemotherapeutic drugs.
Defects in apoptosis signaling which result in evasion from programmed cell death are hallmarks of cancer cells. The Bcl-2 family comprises highly conserved proteins involved in the regulation of apoptosis. Alterations in the expression levels and/or function of Bcl-2 members are widely observed in human neoplasia, including ALL, allowing cancer cells to survive irrespective of physiological or drug-induced death signals. An efficient targeting of the aberrant apoptotic machinery by BH3 mimetics has been recognized as an important strategy to improve actual ALL therapy. However, pre-existing or acquired resistance mechanisms represent a considerable challenge for the clinical use of these molecules.
In this study, two novel therapeutic approaches based on target inhibition of different aberrant signaling pathways in AML and ALL have been investigated.
The first study evaluates the pre-clinical activity of NVP-BKM120 (cited hereafter as BKM120), a novel selective pan-class I PI3K inhibitor, on AML cells. Previous reports have shown that BKM120 exerted cytotoxic effects in vitro and in vivo on several solid tumors and on some hematological malignancies through the selective inhibition of PI3K/Akt/mTOR activity. Conversely, a limited cytotoxicity was observed towards normal cells. Moreover, this compound synergized with well-established chemotherapeutic drugs (i.e. doxorubicin, vincristine) and novel small molecules (i.e. Mek, Bcl-2 and mTOR inhibitors). Our results demonstrate that BKM120 abrogates the activity of the PI3K/Akt/mTOR signaling at low micromolar concentrations, promoting cell growth arrest and a significant apoptosis induction in a dose- and time-dependent manner in AML cells. Conversely, no relevant cytotoxicity is observed on resting or PHA-activated normal mononuclear cells isolated from healthy volunteers. BKM120-induced cytotoxicity is associated with a profound modulation of the metabolic behavior in both cell models and primary samples, particularly reducing the oxidative capabilities and the glycolytic rates of AML cells. In addition, BKM120 synergizes with the glycolytic inhibitor dichloroacetate (DCA), triggering massive apoptosis at lower doses. Finally, in vivo administration of BKM120 to a xenotransplant mouse model of AML significantly inhibits leukemia progression and improves the overall survival of treated mice without inducing any detectble side effects.
In the second study, a novel combined approach to overcome ABT-737 acquired resistance in ALL with the simultaneous inhibition of mTOR pathway by CCI-779 has been explored. It has been shown that activated PI3K/Akt/mTOR pathway decrease ABT-737 effectiveness in cancer cells by upregulating anti-apoptotic Bcl-2 family members (i.e. Mcl-1). Consistently, simultaneous inhibition strongly potentiated cytotoxicity of single agents while exerted only modest toxicity toward normal progenitors in vitro and in vivo. This strategy also triggered apoptosis under hypoxic conditions, thus indicating a potential efficacy even within tumor microenvironment. We demonstrate that co-targeting of Bcl-2 and mTOR strongly sensitized ALL cells to apoptosis, reverting the acquired ABT-737 resistance of cell models and primary samples. Analysis of signaling modulations in newly sensitized ABT-737 resistant cells reveals that ABT-737 plus CCI-779 combination reduces 4EBP1 activation and Mcl-1expression. Since the involvement of proteasomal degradation was excluded, inhibition of 4EBP1-dependent protein translation may be responsible for the synergistic interaction between ABT-737 and CCI-779. However, in some ALL models, Mcl-1 may be not the unique determinant of ABT-737 resistance since knockdown of protein expression by RNA interference does not result in significant changes of cytotoxicity.
Taken together, our results (i) document that BKM120, as single agent or in combination with glycolytic modulators, has a significant anti-leukemic activity towards AML cells, thus supporting its clinical evaluation as a novel targeted agent for this hematological malignancy and (ii) identify a novel therapeutic approach to overcome ABT-737 resistance in ALL, demonstrating the synergistic interaction with the mTOR inhibitor CCI-779 and further clarify the role of Mcl-1 in mediating ABT-737 resistance
Gli utili "occultati" in poste passive fittizie iscritte nel bilancio di un precedente periodo di imposta costituiscono "sempre" sopravvenienze attive
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A liquid biopsy model: Circulating miRNA levels in mice bearing colorectal carcinoma tumor xenografts
No full textMicroRNAs (miRNAs) are deeply involved in tumor onset and progression, either behaving as tumor-promoting miRNAs (oncomiRNAs and metastamiRNAs) or as tumor suppressor miRNAs. This has a very important implication in diagnosis and/or prognosis, including the recent discovery that the pattern of circulating cell-free miRNAs in plasma allows us to perform molecular analyses on these non-invasive liquid biopsies. In order to develop in vivo experimental models for the validation of molecular assays aimed at detecting circulating miRNAs in plasma, we have inoculated nude mice with the HT-29, LS174T and LoVo human colorectal cancer cell lines. Xenotransplanted tumors were allowed to grow up to 0.5 cm3 in size. Blood was drawn at sacrifice, plasma was isolated by low speed centrifugation and was further treated to disrupt exosomes and denaturate miRNA-binding proteins using Qiazol solution. As internal control sequences, equal amount of C. elegans cel-miR-39 was spiked in all samples. Total microRNAs were purified with miRNeasy Serum/Plasma Kit (Qiagen). The levels of miR-141, miR-221 and miR-222 were assessed by Real-Time quantitative PCR (RT-qPCR) and droplet digital PCR (ddPCR). Mice xenotransplanted with HT29 cells displayed 2.3, 1.7 and 4.2 fold-increases in circulating miR-141, miR-221 and miR-222, respectively, compared to control mice. Mice transplanted with LoVo cells displayed increases of lesser magnitude (1.2, 1.7 and 2.2 for miR-141, miR-221 and miR-222), whereas mice transplanted with LS174T displayed a slight increase only for miR-222 (1.3 fold-increase). Circulating miRNAs levels were also correlated with their levels in cultured cells and in exosomes from cultured cells supernatants. Although the number of miRNAs taken into account is limited, these data clearly show, in a strictly controlled setting, that different colorectal carcinoma tumors give rise to very different liquid biopsy miRNA profiles. Therefore, wider panels of xenografts may be useful to recapitulate the clinical variety of colorectal tumors in human patients, estimate the minimal numbers of miRNAs in a diagnostic signature, and validate the overall applicative impact of oncomiRNAs in the liquid biopsy format
Modulation of glycolytic metabolism by dichloroacetate induces apoptosis in acute myeloid leukemia cells
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PI3K inhibition by BKM120 on acute myeloid leukemia: a preclinical study
No full textAcute myeloid leukemia (AML) patients are often characterized by deregulation of various intracellular signaling pathways, including PI3K/Akt/mTOR, which concur to increased cell proliferation and abnormal survival. Stagnation of clinical results, especially in patients not eligible for aggressive treatment, have prompted the investigation on novel targeted therapies. Currently, several PI3K/Akt/mTOR inhibitors, especially those targeting downstream signals, have been investigated in AML. However, reactivation of critical upstream nodes have been associated with reduced activity of these molecules. BKM120 is a novel pan-class I PI3K inhibitor, characterized by a significant cell growth inhibition and apoptosis in a variety of solid tumors. Therefore, we investigated preclinically the activity of BKM120 on several acute leukemia (AL) cell lines and on primary AML samples.
BKM120, kindly provide by Novartis, was tested on different leukemia cell models (U937, HL60, MOLM13) and primar
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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