Insulin-like growth factor 1 receptor (IGF1R) is a prevalent signaling pathway in human cancer that supports cell growth/survival and thus contributes to aggressive biological behavior. Much work has ...gone into development of IGF1R inhibitors; however, candidate agents including small molecule tyrosine kinase inhibitors and blocking antibodies have yet to fulfill their promise clinically. Understanding cellular features that define sensitivity versus resistance are important for effective patient selection and anticipation of outgrowth of a resistant clone. We previously identified an important role for IGF signaling in T-cell acute lymphoblastic leukemia (T-ALL) relying primarily upon genetically defined mouse models. We present here an assessment of IGF1R dependence in human T-ALL using a broad panel of 27 established cell lines that capture a spectrum of the genetic variation that might be encountered in clinical practice. We observed that a subset of cell lines are sensitive to IGF1R inhibition and are characterized by high levels of surface IGF1R expression and PTEN positivity. Interestingly, lentiviral expression or knock-down of PTEN in PTEN-negative/positive cell lines, respectively, had limited effects on their response to IGF1R inhibition, suggesting that PTEN contributes to, but does not define IGF dependence. Additionally, we characterize downstream PI3K/AKT signaling as dominant over RAS/RAF/MEK/ERK in mediating growth and/or survival in this context. Finally, we demonstrate that IGF and interleukin-7 (IL-7) fulfill non-overlapping roles in supporting T-ALL growth. These findings are significant in that they reveal cellular features and downstream mechanisms that may determine the response of an individual patient's tumor to IGF1R inhibitor therapy.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Descriptive sequencing of human leukemia samples has revealed the diversity and combinatorial complexity of oncogenic effector genes which can occur within all or just a subset of tumor cells. With ...the aim of deconvoluting the individual contributions of T-cell acute lymphoblastic leukemia (T-ALL) oncogenes, we employed our recently developed synthetic model of human T-ALL (Kusakabe et al, 2019) to perform a systematic analysis of transcriptional signatures associated with each of the four oncogenes used in our model. We identified synthetic leukemias to cluster based on two gene signatures which resembled distinct stages in T-cell development and had marked variation in MYCN expression, with its highest expression found on the more “immature” cluster. All synthetic leukemias carried activated NOTCH1, which is best known for upregulating MYC, but not MYCN. By analyzing publicly available RNA sequencing datasets, we found MYCN to be highly expressed in early T-cell progenitors (ETPs) and T-ALLs of more immature phenotype.
To assess oncogene “addiction” to MYCN, cell lines and primary synthetic leukemias were transduced with shRNAs or sgRNAs to knock-down (KD) or knock-out (KO) MYCN, respectively. By both approaches, bulk cell growth and/or clonogenic activity were reduced in KD/KO cells as compared to controls, supporting their functional dependence on MYCN. MYCN overexpression resulted in increased clonogenic activity and differentiation delay of NOTCH1-transduced cells in vitro but was still insufficient to generate leukemia in vivo. We are currently exploring other genes with similar expression patterns to MYCN to identify upstream/downstream mediators of MYCN dependence in this context. Our results emphasize stage-specific oncogene dependencies and identify alternate therapeutic targets in T-ALLs with high MYCN expression.
The Wnt signaling pathway has been shown to play important roles in normal hematopoietic stem cell biology and in the development of both acute and chronic myelogenous leukemia. Its role in ...maintaining established leukemia stem cells, which are more directly relevant to patients with disease, however, is less clear. To address what role Wnt signaling may play in T-cell acute lymphoblastic leukemia (T-ALL), we used a stably integrated fluorescent Wnt reporter construct to interrogate endogenous Wnt signaling activity in vivo. In this study, we report that active Wnt signaling is restricted to minor subpopulations within bulk tumors, that these Wnt-active subsets are highly enriched for leukemia-initiating cells (LICs), and that genetic inactivation of β-catenin severely reduces LIC frequency. We show further that β-catenin transcription is upregulated by hypoxia through hypoxia-inducible factor 1α (Hif1α) stabilization, and that deletion of Hif1α also severely reduces LIC frequency. Of note, the deletion of β-catenin or Hif1α did not impair the growth or viability of bulk tumor cells, suggesting that elements of the Wnt and Hif pathways specifically support leukemia stem cells. We also confirm the relevance of these findings to human disease using cell lines and patient-derived xenografts, suggesting that targeting these pathways could benefit patients with T-ALL.
•A real-time, integrated fluorescent Wnt reporter marks rare leukemia stem cells in T-ALL.•Deletion of β-catenin or Hif1α reduces LIC frequency in established tumors, but does not affect the growth of bulk cells.
Cyclin-dependent kinase 10 (CDK10), a CDC2-related kinase, is highly expressed in colorectal cancer. Its role in the pathogenesis of colorectal cancer is unknown. This study examines the function of ...CDK10 in colorectal cancer, and demonstrates its role in suppressing apoptosis and in promoting tumor growth
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Modulation of CDK10 expression in colorectal cancer cell lines demonstrates that CDK10 promotes cell growth, reduces chemosensitivity and inhibits apoptosis by upregulating the expression of Bcl-2. This effect appears to depend on its kinase activity, as kinase-defective mutant colorectal cancer cell lines have an exaggerated apoptotic response and reduced proliferative capacity.
, inhibiting CDK10 in colorectal cancer following intratumoral injections of lentivirus-mediated CDK10 siRNA in a patient-derived xenograft mouse model demonstrated its efficacy in suppressing tumor growth. Furthermore, using a tissue microarray of human colorectal cancer tissues, the potential for CDK10 to be a prognostic biomarker in colorectal cancer was explored. In tumors of individuals with colorectal cancer, high expression of CDK10 correlates with earlier relapse and shorter overall survival. The findings of this study indicate that CDK10 plays a role in the pathogenesis in colorectal cancer and may be a potential therapeutic target for treatment.
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T-cell acute lymphoblastic leukemia (T-ALL) can affect any age group; however, disease outcome is worse in older patients. Aging has been described to be accompanied by an increase in the body's ...proinflammatory status, a phenomenon referred as “inflammaging”. By analysing two T-ALL transcriptome datasets, we have found that inflammation pathways are upregulated in older patients, whereas younger patients present upregulation of cell cycle pathways, suggesting that inflammaging is also recapitulated in T-ALL. Here, we hypothesize that T-ALL oncogenes can cooperate with specific cytokines/stimuli and their signaling pathways to create distinct leukemic phenotypes. To test this, human cord blood CD34+ cells were transduced with different T-ALL oncogenes and grown in co-culture with stromal cells under different pro-inflammatory conditions. We observed that most of the transduced cells had their cell growth negatively affected by the proinflammatory conditions, although some oncogene combinations showed more tolerance to these conditions than others. Activated NOTCH1+TLX3 transduced cells represented the only gene combination that showed significantly higher cell growth in the presence of interferon-gamma (IFNγ) when compared to non-transduced cells in the same culture. IL-15 and IFNγ potentiated differentiation arrest observed with certain oncogene combinations. Normal uncommitted T-cell progenitors (CD7+CD5+CD44+CD1a-) responded to IL-15 via STAT5 and AKT phosphorylation, and this response was enhanced by chronic treatment with IL-15. Our results suggest that proinflammatory conditions can alter the effect of certain oncogenes on T-cell progenitors and influence leukemogenesis, potentially leading to distinct biological behaviors of resulting leukemias. These findings may lead to identification of cytokine dependencies associated with particular T-ALL genetic subtypes.
•Noncanonical interactions of β-catenin with FOXO3 transcription factor promote LIC activity in early T-cell precursor ALL.•β-Catenin– and FOXO3-dependent gene signature identifies LIC-enriched ...CD82+CD117+ cell subsets, highly selected in MRD.
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T-cell acute lymphoblastic leukemia (T-ALL) is a T-cell malignancy characterized by cell subsets and enriched with leukemia-initiating cells (LICs). β-Catenin modulates LIC activity in T-ALL. However, its role in maintaining established leukemia stem cells remains largely unknown. To identify functionally relevant protein interactions of β-catenin in T-ALL, we performed coimmunoprecipitation followed by liquid chromatography–mass spectrometry. Here, we report that a noncanonical functional interaction of β-catenin with the Forkhead box O3 (FOXO3) transcription factor positively regulates LIC-related genes, including the cyclin-dependent kinase 4, which is a crucial modulator of cell cycle and tumor maintenance. We also confirm the relevance of these findings using stably integrated fluorescent reporters of β-catenin and FOXO3 activity in patient-derived xenografts, which identify minor subpopulations with enriched LIC activity. In addition, gene expression data at the single-cell level of leukemic cells of primary patients at the time of diagnosis and minimal residual disease (MRD) up to 30 days after the standard treatments reveal that the expression of β-catenin– and FOXO3-dependent genes is present in the CD82+CD117+ cell fraction, which is substantially enriched with LICs in MRD as well as in early T-cell precursor ALL. These findings highlight key functional roles for β-catenin and FOXO3 and suggest novel therapeutic strategies to eradicate aggressive cell subsets in T-ALL.
T cell acute lymphoblastic leukemia (T-ALL) is an aggressive cancer of immature T cells that often shows aberrant activation of Notch1 and PI3K-Akt pathways. Although mutations that activate PI3K-Akt ...signaling have previously been identified, the relative contribution of growth factor-dependent activation is unclear. We show here that pharmacologic inhibition or genetic deletion of insulin-like growth factor 1 receptor (IGF1R) blocks the growth and viability of T-ALL cells, whereas moderate diminution of IGF1R signaling compromises leukemia-initiating cell (LIC) activity as defined by transplantability in syngeneic/congenic secondary recipients. Furthermore, IGF1R is a Notch1 target, and Notch1 signaling is required to maintain IGF1R expression at high levels in T-ALL cells. These findings suggest effects of Notch on LIC activity may be mediated in part by enhancing the responsiveness of T-ALL cells to ambient growth factors, and provide strong rationale for use of IGF1R inhibitors to improve initial response to therapy and to achieve long-term cure of patients with T-ALL.
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