Acriflavine Inhibits Acquired Drug Resistance by Blocking the Epithelial-to-Mesenchymal Transition and the Unfolded Protein Response

Abstract

Epithelial-to-mesenchymal transition (EMT) is linked to tumor invasion, drug resistance and aggressive disease and this is largely dependent on the cell's microenvironment. Acriflavine (ACF) is an old antibacterial drug recently also suggested as anticancer agent and HIF inhibitor. We wanted to study the effect of acriflavine on EMT in different human cancer models. Pancreatic cancer cells (Panc-1) were exposed to TGF-β1 or cobalt chloride (to mimick severe hypoxia) to induce EMT. For our third model we exposed HepG2 liver cancer cells to sorafenib which resulted in development of acquired drug resistance with strong features of EMT and aggressive behavior. These models were morphologically and functionally (invasion assay) characterized. Markers of EMT were determined using qRT-PCR and Western blotting. Transcriptome analysis was performed following gene expression determination and combining the iRegulon tool and Gene Set Enrichment Analysis (GSEA). We made the following observations: (1) acriflavine inhibited EMT based on changes in cell morphology, invasive capacities and markers of EMT (at protein and gene expression level). (2) Transcriptome analysis revealed potent inhibition of ATF4 target genes and of the unfolded protein response. We showed that acriflavine blocked eIF2a phosphorylation and reduced ATF4 translation thereby inhibiting the PERK/eIF2a/ATF4 UPR pathway. (3) ACF restored drug sensitivity of cells that obtained acquired resistance. Conclusions: We identified acriflavine as a potent inhibitor of EMT and the UPR, thereby re-sensitizing the cancer cells to antineoplastic drugs.

Activating Transcription Factor 4 Modulates TGFβ-Induced Aggressiveness in Triple-Negative Breast Cancer via SMAD2/3/4 and mTORC2 Signaling

“…Numerous stress types induce the ISR-regulated ATF4 activation mediated by p-eIF2a (4). The ISR controlled by PERK-GCN2/eIF2a/ATF4 mediates EMT and metastasis (10,11,13), tumorigenesis (9,14), and chemoresistance (16,17). In nonstressing conditions and presence of TGFb1, we found that the ISR did not drive ATF4 expression for all the cell lines tested herein; however, it was important in SUM159PT and MDA-MB-231 cells.…”

“…ATF4 is a transcription factor belonging to the ATF/cyclic adenosine monophosphate response element binding protein (ATF/CREB) family, overexpressed in tumors, including breast cancer and TNBC (6)(7)(8). ATF4 regulates tumor growth, autophagy, drug resistance, and metastasis during ISR through PERK and GCN2 pathways (9)(10)(11)(12)(13)(14)(15)(16)(17). Independent of the cellular stress, ATF4 regulates cell metabolism (8,18,19), osteoblast differentiation (20), drug resistance (21), invasion, and metastasis in esophageal squamous cell carcinoma (22).…”

Starvation and Pseudo-Starvation as Drivers of Cancer Metastasis through Translation Reprogramming

“…Increased PERK activity in breast cancer is considered a key feature of cells with an epithelial-to-mesenchymal (EMT)-related phenotype (Feng et al, 2014). Significantly, suppressing the PERK/eIF2a/ ATF4 axis in pancreatic cancer cells using acriflavine led to inhibition of morphological EMT and invasion as well as reversal of acquired drug resistance (Dekervel et al, 2017). eIF2a phosphorylation is also a driver of increased invasiveness in chronic myeloid leukemia (Podszywalow-Bartnicka et al, 2016).…”

The ATP-dependent chromatin remodelling enzyme Uls1 prevents Topoisomerase II poisoning

“…However, a previous large-scale chemogenetic screen identified ACF as a drug that specifically kills uls1 Δ yeast (26) and we confirmed the potent toxicity of ACF (Fig 1A). ACF has been described as having antibacterial (27), antimalarial (28) and anti-cancer properties (29). This broad range of activity is likely due to the fact that ACF inhibits type II topoisomerase activity in vitro (28, 30).…”