| Popis: |
The sustainable activation of the RAS/MAPK and PI3K/AKT signaling pathways in cancer is promoted by a reduction in the activity of the tumor suppressor protein phosphatase 2A (PP2A). Therefore, a novel therapeutic strategy consists of directly activating PP2A, leading to the simultaneous inhibition of these oncogenic pathways. Our lab has successfully developed first-in-class Small Molecule Activators of PP2A (SMAPs), which induce tumor growth inhibition in vivo. Alterations to the putative drug binding site validate PP2A as the direct target of SMAPs. The putative residues of PP2A-Aa that were interacting with SMAPs K194 E197, and L198 were mutated. H358, a KRAS-driven lung adenocarcinoma cell line, was used to create isogenic cell lines stably overexpressing mutated and wild type PP2A-Aa. SMAP response was investigated in vivo using a xenograft model of H358 isogenic cell lines and it was determined that tumors harboring mutant K194R and L198V PP2A-Aa were resistant to SMAPs treatment. Together, our results suggest that residues K194 and L198 are required for drug binding and subsequent target engagement. On another hand, most lung adenocarcinoma (LUAD) patients acquire resistance to tyrosine kinase inhibitors (TKI) via mechanisms enabling the sustained activation of the MAPK and PI3K oncogenic pathways downstream of the tyrosine kinase EGFR. We hypothesize that activation of PP2A simultaneously inhibits the MAPK and AKT pathways and is a promising therapeutic strategy for TKI-resistant LUAD. TKI-resistant LUAD cell lines were treated with SMAPs. RNAseq kinase enrichment analysis followed by principal component analysis indicated that SMAP treatment induces a gene signature similar to a combination of the selective AKT and MEK inhibitors MK2206 and AZD6244, respectively. The therapeutic potential of PP2A activation in vivo was first evaluated in a transgenic mouse model. SMAP- treated mice showed less diffuse lung cancer and a significant decrease in total nodules. Single-agent SMAP demonstrated significant tumor growth inhibition, as well as ERK and AKT dephosphorylation, in a patient-derived xenograft model. Combination of SMAP and the TKI Afatinib resulted in an enhanced effect on tumor growth inhibition in a H1975 xenograft model. These collective data support the development of PP2A activators for the treatment of TKI-resistant LUAD. |
