Harmine and Piperlongumine Revert TRIB2-Mediated Drug Resistance.

Susana Machado,Inês Grenho,Isabel Duarte,Bruno Santos,Andreia Silva,Fátima Sánchez-Cabo,Wolfgang Link,Diego Megias,Ana Dopazo,Bibiana I Ferreira,Victor Mayoral-Varo,Ana Luísa De Sousa-Coelho

doi:10.3390/cancers12123689

Abstract

Simple SummaryPoor survival and treatment failure of patients with cancer are mainly due to resistance to therapy. Tribbles homologue 2 (TRIB2) has recently been identified as a protein that promotes resistance to several anti-cancer drugs. In this study, RNA sequencing and bioinformatics analysis were used with the aim of characterizing the impact of TRIB2 on the expression of genes and developing pharmacological strategies to revert these TRIB2-mediated changes, thereby overcoming therapy resistance. We show that two naturally occurring alkaloids, harmine and piperlongumine, inverse the gene expression profile produced by TRIB2 and sensitize cancer cells to anti-cancer drugs. Our data suggest that harmine and piperlongumine or similar compounds might have the potential to overcome TRIB2-mediated therapy resistance in cancer patients.Therapy resistance is responsible for most relapses in patients with cancer and is the major challenge to improving the clinical outcome. The pseudokinase Tribbles homologue 2 (TRIB2) has been characterized as an important driver of resistance to several anti-cancer drugs, including the dual ATP-competitive PI3K and mTOR inhibitor dactolisib (BEZ235). TRIB2 promotes AKT activity, leading to the inactivation of FOXO transcription factors, which are known to mediate the cell response to antitumor drugs. To characterize the downstream events of TRIB2 activity, we analyzed the gene expression profiles of isogenic cell lines with different TRIB2 statuses by RNA sequencing. Using a connectivity map-based computational approach, we identified drug-induced gene-expression profiles that invert the TRIB2-associated expression profile. In particular, the natural alkaloids harmine and piperlongumine not only produced inverse gene expression profiles but also synergistically increased BEZ235-induced cell toxicity. Importantly, both agents promote FOXO nuclear translocation without interfering with the nuclear export machinery and induce the transcription of FOXO target genes. Our results highlight the great potential of this approach for drug repurposing and suggest that harmine and piperlongumine or similar compounds might be useful in the clinic to overcome TRIB2-mediated therapy resistance in cancer patients.

Highlights

Many cancer patients fail to respond to anti-cancer treatment due to intrinsic or acquired resistance, widely described for various types of cancer [1]
Our results show that several small-molecule compounds, including harmine (HAR) and piperlongumine (PIP), can affect Tribbles homologue 2 (TRIB2)-mediated transcriptional signatures and, in line with this observation, can induce the nuclear translocation of FOXO3 and its consequent activation
By comparing U2OS TRIB2-overexpressing cells with mock-transfected cells in basal conditions and upon BEZ235 treatment, we obtained four lists of differentially expressed genes (DEGs) (Figure 1A), in which DEG5 and DEG6 are a subset of DEG1 and differentially regulated by TRIB2 overexpression (DEG2), respectively

Summary

Introduction

Many cancer patients fail to respond to anti-cancer treatment due to intrinsic or acquired resistance, widely described for various types of cancer [1]. Resistance to anti-cancer therapy is the major obstacle to improving the clinical outcome for cancer patients and to reap the full benefits of targeted therapies and immunotherapies. Identification of the molecular mechanisms involved in drug resistance is of great clinical and economic importance. We have previously characterized a novel molecular mechanism of therapy resistance in melanoma mediated by the kinase-like protein Tribbles homologue 2 (TRIB2) [2]. The human TRIB1, -2 and -3 orthologues contain a catalytically impaired pseudokinase domain, and instead of directly phosphorylating target proteins, they act as adaptors in signaling pathways for important cellular processes. We identified TRIB2 in a genetic screening aimed at the identification of repressor proteins of FOXO transcription factors [8], the major downstream transcriptional effectors of the PI3K/AKT pathway [9]. Our studies identified TRIB2 as a novel oncogene and as a biomarker in melanoma [8], whose expression correlates with disease stage [10]

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