Reverse transcriptase inhibition potentiates target therapy in BRAF-mutant melanomas: effects on cell proliferation, apoptosis, DNA-damage, ROS induction and mitochondrial membrane depolarization

Luigi Fattore,Gerardo Botti,Sabrina Castellano,Gennaro Ciliberto,Rita Mancini,Paolo A. Ascierto,Debora Malpicci,Ciro Milite,Gianluca Sbardella

doi:10.1186/s12964-020-00633-7

Abstract

Target therapies based on BRAF and MEK inhibitors (MAPKi) have changed the therapeutic landscape for metastatic melanoma patients bearing mutations in the BRAF kinase. However, the emergence of drug resistance imposes the necessity to conceive novel therapeutic strategies capable to achieve a more durable disease control. In the last years, retrotransposons laying in human genome have been shown to undergo activation during tumorigenesis, where they contribute to genomic instability. Their activation can be efficiently controlled with reverse transcriptase inhibitors (RTIs) frequently used in the treatment of AIDS. These drugs have demonstrated anti-proliferative effects in several cancer models, including also metastatic melanoma. However, to our knowledge no previous study investigated the capability of RTIs to mitigate drug resistance to target therapy in BRAF-mutant melanomas. In this short report we show that the non-nucleoside RTI, SPV122 in combination with MAPKi strongly inhibits BRAF-mutant melanoma cell growth, induces apoptosis, and delays the emergence of resistance to target therapy in vitro. Mechanistically, this combination strongly induces DNA double-strand breaks, mitochondrial membrane depolarization and increased ROS levels. Our results shed further light on the molecular activity of RTI in melanoma and pave the way to their use as a novel therapeutic option to improve the efficacy of target therapy.7fN6r4qRQJy_8CfHGxK4XPVideo Graphical abstract

Highlights

Combination therapy with BRAF and MEK inhibitors (MAPKi) has become standard of care for melanoma patients harboring BRAF-V600 mutations [1, 2]
SPV122 + BRAF/MEK inhibitors (MAPKi) reduce cell proliferation, induce apoptosis, and cell cycle blockade and delay drug resistance in BRAF-mutant melanoma cells in vitro SPV122 and its stereoisomers have demonstrated the capability to inhibit cell proliferation and to induce differentiation in A379 melanoma cells. Those effects reproduced those observed with other nonnucleoside RT inhibitors (NNRTIs), like efavirenz or after RNA interference (RNAi)-mediated silencing of the RT-encoding Long Interspersed Nuclear Element1 (LINE-1) elements [27,28,29]
Cells were treated with efavirenz and SPV122 or stavudine and zidovudine starting from 100 μM and diluted 1:2 for 10 times

Summary

Introduction

Combination therapy with BRAF and MEK inhibitors (MAPKi) has become standard of care for melanoma patients (approximately 50%) harboring BRAF-V600 mutations [1, 2]. A challenging field of cancer research is the possibility to take advantage of reverse transcriptase (RT) inhibitors [12], normally used against retroviruses like HIV-1 for the therapy of AIDS [13]. The rationale for this approach lays on the existence in our genome of retrotransposons, i.e. genetic sequences able to copy themselves into an RNA intermediate and to insert elsewhere in host DNA [14]. In most adult human tissues, telomerase activity is low or undetectable Their up-regulation is a critical event in over 90% of cancers but the molecular mechanisms underpinning TERT activation are not completely understood [22]

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Conclusion