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E-cadherin loss induces autocrine activation of oncogenic growth factor signalling in metastatic lobular breast cancer.

ABSTRACT: Background: Despite the fact that loss of E-cadherin is causal to the development and progression of invasive lobular breast cancer (ILC), no targeted therapy is available to treat this major breast cancer subtype. This study is aimed at identifying clinically targetable pathways that are aberrantly active downstream of E-cadherin loss in ILC. Methods: Reverse-phase protein array (RPPA) analyses were performed in the context of E-cadherin loss using mouse and human breast cancer cells. A combination of mRNA sequencing, conditioned medium growth assays and CRISPR-Cas9 knock-out experiments were performed to identify and validate activation of oncogenic pathways in ILC. Human ILC samples were employed to validate activation by immunohistochemistry on tissue micro-arrays. Finally, we assessed the effect of pathway inhibition using anoikis resistance and anchorage-dependent growth in vitro. Results: We demonstrate that E-cadherin loss leads to increased activation of FAK and PI3K/AKT signalling. Autocrine activation of growth factor receptor signalling and its downstream PI3K/AKT hub was a direct consequence of E-cadherin loss, independent of activating mutations in either PIK3CA, AKT or PTEN. Analysis of human ILC samples confirmed pathway activity, and pharmacological inhibition of AKT using AZD5363 and MK2206 resulted in robust inhibition of cell growth and survival of ILC cells in anchorage-dependent and independent conditions. Moreover, our results indicate a role for intracellular FAK in the regulation of ILC anoikis resistance. Conclusion: Our data demonstrate that E-cadherin loss evokes additional PI3K/AKT activation independent of oncogenic mutations in this pathway. We propose clinical intervention of PI3K/AKT in ILC based on functional E-cadherin inactivation, irrespective of activating pathway mutations.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE81977 | GEO | 2019/03/22

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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E-cadherin loss induces autocrine activation of oncogenic growth factor signalling in metastatic lobular breast cancer.

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