Specific c-Jun N-Terminal Kinase Inhibitor, JNK-IN-8 Suppresses Mesenchymal Profile of PTX-Resistant MCF-7 Cells through Modulating PI3K/Akt, MAPK and Wnt Signaling Pathways

SIMPLE SUMMARY: Investigation into effective targets of drug resistance is important for identifying novel strategies in cancer therapy. The study aimed to determine the functional role of paclitaxel (PTX) resistance on MCF-7 cell survival related to PI3K/Akt and MAPK pathways. Therefore, we generated PTX-resistant (PTX-res) MCF-7 cells exposed to increasing concentrations of PTX (5–100 nM) over a period of 6 months. Increased cell survival, proliferation, and colony formations were observed in PTX-res MCF-7 cells, while survival inhibition was determined in non-resistant wt cells. PTX-res MCF-7 cells appeared morphologically different from wt cells with their star-like shape which showed the mesenchymal characteristics of cells. Active PI3K/Akt signaling and increased motility were confirmed by upregulation of the EMT pathway members in PTX-res MCF-7 cells. We suggested that the active Akt signaling was related to the upregulated stress-mediated activation of MAPK signaling members, as shown by the significant p38 and SAPK/JNK activation in our results. To sensitize PTX-res MCF-7 cells we treated wt and PTX-res MCF-7 cells with specific c-Jun N-terminal kinase inhibitor, JNK-IN-8, and significant suppression on p38, SAPK/JNK expression was observed. Wnt signaling was highly affected by JNK inhibition. We concluded that JNK inhibition is a potential target to reverse PTX-resistance related to Wnt signaling. ABSTRACT: Paclitaxel (PTX) is a widely used chemotherapeutic agent in the treatment of breast cancer, and resistance to PTX is a common failure of breast cancer therapy. Therefore, understanding the effective molecular targets in PTX-resistance gains importance in identifying novel strategies in successful breast cancer therapy approaches. The aim of the study was to investigate the functional role of PTX resistance on MCF-7 cell survival and proliferation related to PI3K/Akt and MAPK pathways. The generated PTX-resistant (PTX-res) MCF-7 cells showed enhanced cell survival, proliferation, and colony formation potential with decreased cell death compared to wt MCF-7 cells. PTX-res MCF-7 cells exhibited increased motility profile with EMT, PI3K/Akt, and MAPK pathway induction. According to the significant SAPK/JNK activation in PTX-res MCF-7 cells, specific c-Jun N-terminal kinase inhibitor, JNK-IN-8 is shown to suppress the migration potential of cells. Treatment of JNK inhibitor suppressed the p38 and SAPK/JNK and Vimentin expression. However, the JNK inhibitor further downregulated Wnt signaling members in PTX-res MCF-7 cells. Therefore, the JNK inhibitor JNK-IN-8 might be used as a potential therapy model to reverse PTX-resistance related to Wnt signaling.