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PI3K/AKT pathway is activated by miRNA-22 in the proliferative CLL subset (mRNA)

ABSTRACT: Understanding the crosstalk between malignant B-cells and their milieu could provide clues on the molecular and clinical biology of Chronic Lymphocytic Leukemia (CLL). Aiming to generate novel therapeutic strategies, different groups have studied different CLL proliferative fractions. We previously, identified one of these proliferative subsets in the peripheral blood from progressive unmutated CLL patients. Since the presence of this small subset appears to be a hallmark of a proliferative disease in which B lymphocytes are being constitutively activated in the proliferative centers of these patients, we performed gene expression analysis comparing the global mRNA and microRNAs expression of this leukemic subpopulation. Our results suggest that the proliferative behaviour of this fraction appears to depend on microRNA-22 over-expression, which induces PTEN downregulation and PI3K/AKT pathway activation. Transfection experiments demonstrated that miR-22 overexpression in CLL B-cells switches on PI3K/AKT leading to FOXO1 inactivation, p27-Kip1 downregulation, and overexpression of Survivin and Ki-67 proteins. We also demonstrated that this pathway could be triggered by microenvironment signals like CD40L/IL4 and more importantly, that this regulatory loop is also present in lymph nodes from progressive UM patients. Altogether, these results underline the key role of PI3K/AKT pathway in the generation of the CLL proliferative pool and provide rationale for the usage of PI3K inhibitors.

ORGANISM(S): Homo sapiens

PROVIDER: GSE53236 | GEO | 2014/05/15

SECONDARY ACCESSION(S): PRJNA231485

REPOSITORIES: GEO

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Project description:Hyperactivation of the PI3K/AKT pathway is observed in most NSCLCs, promoting proliferation, migration and resistance to therapy. AKT can be activated through several mechanisms that include loss of the negative regulator PTEN, activating mutations of the catalytic subunit of the positive regulator phosphatydil-inositol-3â phosphate kinase (PIK3CA) and/or mutations of AKT1 itself. However, whereas the effects of AKT activation on mRNAs and proteins in the cell are fairly clear, the role of miRNAs as downstream targets of activated PI3K/AKT signalling is still poorly defined so far. To identify miRNAs that are targets of constitutive signalling of PI3K/AKT in lung cancer cells, we performed miRNA profiling of human lung epithelial cells expressing active mutant AKT1 (E17K), active mutant PI3KCA (E545K) or that are silenced for PTEN. We identified 28 differentially expressed miRNAs (8 up-regulated, 20 down-regulated) that were common to BEAS-AKT1-E17K, BEAS-PIK3CA-E545K and BEAS-shPTEN cells. Among the 8 up-regulated miRNAs that were common to all the alterations, the miRNA most consistently up-regulated by activation of the PI3K/AKT pathway in BEAS-2B cells was miR-196a. The results reported here demonstrate that miR-196a acts as oncogene downstream the PI3K/AKT pathway, mediating the proliferative, pro-migratory and tumorigenic activity of this pathway in NSCLC cells by targeting FoxO1 and p27 expression. By adoptive expression of miR-196a in BEAS-2B cells, we demonstrated that miR-196a stimulates anchorage-dependent and -independent proliferation, migration and tumorigenicity in BEAS-2B cells. On the other hand, by use of antimir-196a in NCI-H460 cells to silence the endogenous expression of miR-196a, we demonstrate that miR-196a plays a pivotal role in mediating the stimulation of proliferation, migration and tumorigenicity induced by aberrant activation of PI3K/AKT signalling. Accordingly, we found that miR-196a was significantly overexpressed in human NSCLC-derived cell lines (n=6) and primary lung cancer samples (n=28). Finally, based on predicted binding sites for miR-196a by microRNA analysis software, we found that miR-196a affects protein levels of FoxO1 and p27 in NSCLC cells.

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PI3K/AKT pathway is activated by miRNA-22 in the proliferative CLL subset (mRNA)

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