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Direct activation of PP2A for the treatment of tyrosine kinase inhibitor–resistant lung adenocarcinoma
Rita Tohmé, … , Jaya Sangodkar, Goutham Narla
Rita Tohmé, … , Jaya Sangodkar, Goutham Narla
Published February 21, 2019
Citation Information: JCI Insight. 2019;4(4):e125693. https://doi.org/10.1172/jci.insight.125693.
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Research Article Oncology Therapeutics

Direct activation of PP2A for the treatment of tyrosine kinase inhibitor–resistant lung adenocarcinoma

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Abstract

Although tyrosine kinase inhibitors (TKIs) have demonstrated significant efficacy in advanced lung adenocarcinoma (LUAD) patients with pathogenic alterations in EGFR, most patients develop acquired resistance to these agents via mechanisms enabling the sustained activation of the PI3K and MAPK oncogenic pathways downstream of EGFR. The tumor suppressor protein phosphatase 2A (PP2A) acts as a negative regulator of these pathways. We hypothesize that activation of PP2A simultaneously inhibits the PI3K and MAPK pathways and represents a promising therapeutic strategy for the treatment of TKI-resistant LUAD. After establishing the efficacy of small molecule activators of PP2A (SMAPs) in a transgenic EGFRL858R model and TKI-sensitive cell lines, we evaluated their therapeutic potential in vitro and in vivo in TKI-resistant models. PP2A activation resulted in apoptosis, significant tumor growth inhibition, and downregulation of PI3K and MAPK pathways. Combination of SMAPs and TKI afatinib resulted in an enhanced effect on the downregulation of the PI3K pathway via degradation of the PP2A endogenous inhibitor CIP2A. An improved effect on tumor growth inhibition was observed in a TKI-resistant xenograft mouse model treated with a combination of both agents. These collective data support the development of PP2A activators for the treatment of TKI-resistant LUAD.

Authors

Rita Tohmé, Sudeh Izadmehr, Sai Gandhe, Giancarlo Tabaro, Sanjay Vallabhaneni, Ava Thomas, Neal Vasireddi, Neil S. Dhawan, Avi Ma’ayan, Neelesh Sharma, Matthew D. Galsky, Michael Ohlmeyer, Jaya Sangodkar, Goutham Narla

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Figure 1

PP2A activation inhibits lung tumor development in an EGFR-driven TKI-sensitive non–small cell lung carcinoma transgenic model.

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PP2A activation inhibits lung tumor development in an EGFR-driven TKI-se...
(A) Expression of TRE-EGFRL858R was induced with doxycycline, and mice were administered either vehicle control or 100 mg/kg of SMAP every 48 hours. (B) Axial images obtained using MRI before and after treatment with vehicle control or SMAP. (C) H&E-stained sections of lung samples. (D) Quantification of H&E results. (E) Quantification of MRI results. (F) Immunohistochemical staining to detect apoptosis (TUNEL) and proliferation. Scale bar: 100 µm. (G) Quantification of TUNEL. (H) Quantification of PCNA. (I) Immunohistochemical staining of pERK and pAKT. Scale bar: 20 µm. Respective quantifications are represented as mean ± SD. *P < 0.05; ***P < 0.001.

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