Induction of STK11-dependent cytoprotective autophagy in breast cancer cells upon honokiol treatment

Abstract

Cancer cells hijack autophagy pathway to evade anti-cancer therapeutics. Many molecular signaling pathways associated with drug-resistance converge on autophagy induction. Honokiol (HNK), a natural phenolic compound purified from Magnolia grandiflora, has recently been shown to impede breast tumorigenesis and, in the present study, we investigated whether breast cancer cells evoke autophagy to modulate therapeutic efficacy and functional networks of HNK. Indeed, breast cancer cells exhibit increased autophagosomes-accumulation, MAP1LC3B-II/LC3B-IIconversion, expression of ATG proteins as well as elevated fusion of autophagosomes and lysosomes upon HNK treatment. Breast cancer cells treated with HNK demonstrate significant growth inhibition and apoptotic induction, and these biological processes are blunted by macroautophagy/autophagy. Consequently, inhibiting autophagosome formation, abrogating autophagosome-lysosome fusion or genetic-knockout of BECN1 and ATG7 effectively increase HNK-mediated apoptotic induction and growth inhibition. Next, we explored the functional impact of tumor suppressor STK11 in autophagy induction in HNK-treated cells. STK11-silencing abrogates LC3B-II-conversion, and blocks autophagosome/lysosome fusion and lysosomal activity as illustrated by LC3B-Rab7 co-staining and DQ-BSA assay. Our results exemplify the cytoprotective nature of autophagy invoked in HNK-treated breast cancer cells and put forth the notion that a combined strategy of autophagy inhibition with HNK would be more effective. Indeed, HNK and chloroquine (CQ) show synergistic inhibition of breast cancer cells and HNK-CQ combination treatment effectively inhibits breast tumorigenesis and metastatic progression. Tumor-dissociated cells from HNK-CQ treated tumors exhibit abrogated invasion and migration potential. Together, these results implicate that breast cancer cells undergo cytoprotective autophagy to circumvent HNK and a combined treatment with HNK and CQ can be a promising therapeutic strategy for breast cancer.

Current methods to analyze lysosome morphology, positioning, motility and function

“…This results in the release of bright fluorescent fragments (Figure 4), allowing the visualization of the lysosomal/ autophagic degradation capacity. 77 Some applications of the DQ-BSA probe are the discovery of cancer therapeutics 78,79 or the identification of compounds promoting lysosomal function in cellular models of LSDs. 80 In this assay, cells are incubated with DQ-BSA (10 μg/mL for 2 hours), fixed and the number and intensity of DQ-BSA puncta quantified.…”

Dissecting the Gene Expression Networks Associated with Variations in the Major Components of the Fatty Acid Semimembranosus Muscle Profile in Large White Heavy Pigs

“…Intriguingly, in the present study, we found several genes involved in the autophagy regulation being downregulated in samples with high palmitic acid. In particular, in addition to MFN2, high palmitic and palmitoleic acid contents in SM were associated with a downregulation of the genes La Ribonucleoprotein 1, Translational Regulator (LARP1), RNA Binding Motif Protein 14 (RBM14), and Serine/Threonine Kinase 11 (STK11), which are all genes whose expression activates autophagy [56][57][58]. Also, the gene Leucine Rich Repeat Kinase 2 (LRRK2), upregulated in the samples with high IMF, palmitic, palmitoleic, and oleic acids, has been implicated in the literature as a modulator of the autophagy process [59].…”

AKF-D52, a Synthetic Phenoxypyrimidine-Urea Derivative, Triggers Extrinsic/Intrinsic Apoptosis and Cytoprotective Autophagy in Human Non-Small Cell Lung Cancer Cells

“…The balance between cell survival and cell death is an important factor contributing to the maintenance of cellular homeostasis. Notably, autophagy contributes to the control of cell homeostasis, inducing either cell survival (cytoprotective autophagy) [ 51 , 52 ] or cell death (autophagic cell death) [ 53 , 54 ]. In the present study, we observed that AKF-D52 treatment triggers autophagy by increasing AVOs’ formation and LC3-II accumulation, coupled with a reduction in the expression of p62 in A549 and NCI-H358 cells.…”