Characterization of TRIB2 mediated drug resistance and its validation as a novel diagnostic marker

Funder

Organizational Unit

Publications

TRIB2 confers resistance to anti-cancer therapy by activating the serine/threonine protein kinase AKT

Publication . Hill, Richard; Madureira, Patricia; Ferreira, Bibiana; Baptista, Inês; Machado, S.; Colaco, Laura; dos Santos, Marta; Liu, Ningshu; Dopazo, Ana; Ugurel, Selma; Adrienn, Angyal; Kiss-Toth, Endre; Isbilen, Murat; Gure, Ali O.; Link, Wolfgang

Intrinsic and acquired resistance to chemotherapy is the fundamental reason for treatment failure for many cancer patients. The identification of molecular mechanisms involved in drug resistance or sensitization is imperative. Here we report that tribbles homologue 2 (TRIB2) ablates forkhead box O activation and disrupts the p53/MDM2 regulatory axis, conferring resistance to various chemotherapeutics. TRIB2 suppression is exerted via direct interaction with AKT a key signalling protein in cell proliferation, survival and metabolism pathways. Ectopic or intrinsic high expression of TRIB2 induces drug resistance by promoting phospho-AKT (at Ser473) via its COP1 domain. TRIB2 expression is significantly increased in tumour tissues from patients correlating with an increased phosphorylation of AKT, FOXO3a, MDM2 and an impaired therapeutic response. This culminates in an extremely poor clinical outcome. Our study reveals a novel regulatory mechanism underlying drug resistance and suggests that TRIB2 functions as a regulatory component of the PI3K network, activating AKT in cancer cells.

2017-03Journal article

Open Access

Characterization of TRIB2 mediated drug resistance and its validation as a novel diagnostic marker

Publication . Machado, Susana da Costa Silva; Link, Wolfgang; Ferreira, Bibiana

Intrinsic and acquired resistance to conventional and targeted chemotherapeutics is the fundamental reason for treatment failure in many cancer patients. Identifying molecular mechanisms involved in drug resistance or sensitization to targeted therapy is of enormous clinical importance. Critical transcription factors such as forkhead box O (FOXO) proteins and p53 have been shown to mediate the action of multiple anti-cancer drugs. Our lab discovered a novel mechanism of drug resistance facilitated by TRIB2 by activating AKT and, consequently, the inactivation of both FOXO and p53. Furthermore, this lab has established TRIB2 as a potential biomarker for melanoma, and its expression correlated with disease stage (I-IV). As TRIB2 may potentially be used as a biomarker and confers resistance to several standard front-line therapeutics to treat melanoma, these results are extremely relevant for the clinical management of melanoma. While accounting for less than 5% of all skin cancer patients, melanoma is the deadliest form of skin cancer, responsible for over 90% of all skin cancer deaths. Furthermore, metastatic melanoma incidence has increased over the past three decades, with a mortality rate that continues to rise faster than almost all other cancers. Genetic analyses of melanoma have uncovered several key pathways in disease onset and progression, most prominently are the Ras/Raf/MEK/ERK and the PI3K/AKT/FOXO signalling pathways. In the decades 70 and 80, the established treatment for metastatic melanoma included high-dose interleukin-2 or dacarbazine (DTIC) administration associated with response rates of between 10-20% with severe side effects during treatment. The limited success prompted investigators to further characterize and understand the disease, leading to the development of immunotherapy, namely immune checkpoint inhibitors (pembrolizumab, nivolumab and ipilimumab), and targeted therapy, namely the BRAF inhibitors vemurafenib and dabrafenib and the MEK inhibitor trametinib, which are approved to treat melanoma patients with mutated BRAF (about 50% of patients). Simultaneously, several PI3K, AKT, mTOR, and MEK inhibitors have been tested in clinical trials but, intrinsic or acquired resistance limits the efficacy of all these treatments. Our lab has previously shown that the tumour suppressor FOXO is the central downstream transcriptional mediator of the PI3K/AKT pathway after PI3K inhibition, which is in accordance with other studies that also show that FOXOs are crucial for the anti-cancer action of several drugs, in particular, PI3K pathway inhibitors. Therefore, proteins capable of inactivating FOXO factors are good candidates for mediating tumour formation, progression and resistance to these agents. Strikingly, our lab previously established TRIB2 as an oncogenic protein that suppresses FOXO factors in melanoma and induces resistance to the dual PI3K/mTOR inhibitor BEZ235 (dactolisib). We hypothesize that TRIB2 mediates therapy resistance by altering the gene expression profile of the cells, and we can pharmacologically reverse these effects of TRIB2. 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. The natural alkaloids harmine and piperlongumine produced inverse gene expression profiles and synergistically increased BEZ235-induced cell toxicity. Notably, both agents promote FOXO nuclear translocation without interfering with the nuclear export machinery and induce 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 help overcome TRIB2-mediated therapy resistance in cancer patients.

2021-11-19Doctoral thesis

Open Access