Synergistic effect of Dactolisib/Lys05 combination on autophagy in A549 cells.

Effective therapeutic strategies are urgently required to enhance the prognosis of patients suffering from KRAS mutations. Owing to the undruggable nature of KRAS, targeting downstream signaling pathways, namely PI3K/AKT/mTOR, shows antiproliferative and apoptotic effects. Unfortunately, targeting this pathway upregulates autophagy, contributing to reduced drug efficacy. Therefore, it was reasonable to use a combination of kinase inhibitors and autophagy inhibitors to achieve a higher therapeutic benefit. The impact of Dactolisib, a dual PI3K/mTOR inhibitor, and Lys05, a dimeric chloroquine, was tested on the survival of breast cancer MCF-7 and lung cancer A549 cells. The dose selection for the optimal effect of the Dactolisib/Lys05 combination was determined using CompuSyn software. This combinatorial effect was evaluated using various methodologies, such as expression profile analysis for autophagic, proliferative, and apoptotic markers. These effects were corroborated by ELISA, Western blot, and flow cytometry using the Annexin V-FITC apoptosis detection kit. A549 cells treated in a 2:1 ratio of Lys05 and Dactolisib demonstrated a synergistic effect on cell death, proliferation, and apoptotic gene markers, in addition to its effect on autophagic gene and protein markers, showing an enhanced effect compared to monotherapy. Therefore, the PI3K/AKT kinase inhibitor/autophagy inhibitor combination establishes higher therapeutic benefits on A549 cells compared to kinase inhibitor monotherapy.

Sequential Salinomycin Treatment Results in Resistance Formation through Clonal Selection of Epithelial-Like Tumor Cells.

Acquiring therapy resistance is one of the major obstacles in the treatment of patients with cancer. The discovery of the cancer stem cell (CSC)-specific drug salinomycin raised hope for improved treatment options by targeting therapy-refractory CSCs and mesenchymal cancer cells. However, the occurrence of an acquired salinomycin resistance in tumor cells remains elusive. To study the formation of salinomycin resistance, mesenchymal breast cancer cells were sequentially treated with salinomycin in an in vitro cell culture assay, and the resulting differences in gene expression and salinomycin susceptibility were analyzed. We demonstrated that long-term salinomycin treatment of mesenchymal cancer cells resulted in salinomycin-resistant cells with elevated levels of epithelial markers, such as E-cadherin and miR-200c, a decreased migratory capability, and a higher susceptibility to the classic chemotherapeutic drug doxorubicin. The formation of salinomycin resistance through the acquisition of epithelial traits was further validated by inducing mesenchymal-epithelial transition through an overexpression of miR-200c. The transition from a mesenchymal to a more epithelial-like phenotype of salinomycin-treated tumor cells was moreover confirmed in vivo, using syngeneic and, for the first time, transgenic mouse tumor models. These results suggest that the acquisition of salinomycin resistance through the clonal selection of epithelial-like cancer cells could become exploited for improved cancer therapies by antagonizing the tumor-progressive effects of epithelial-mesenchymal transition.