Biology subjects

Vlahov, N.

Publications and source records attributed to Vlahov, N..

5 recordsLinked to original sources

bioRxiv2024

A targetable PREX2/RAC1/PI3Kβ signalling axis confers resistance to clinically relevant therapeutic approaches in melanoma

Metastatic melanoma remains a major clinical challenge. Large-scale genomic sequencing of melanoma has identified bona fide activating mutations in RAC1, with mutations of its upstream regulator, the RAC-GEF PREX2, also commonly detected. Crucially, RAC1 mutations are associated with resistance to BRAF-targeting therapies. Despite the role of its homologue PREX1 in melanomagenesis, and evidence that some truncating PREX2 mutations drive increased RAC1 activity, no hotspot mutations have been identified, and the impact of PREX2 mutation remains contentious. Here, we use genetically engineered mouse models and patient-derived BRAFV600E-driven melanoma cell lines to dissect the role of PREX2 in melanomagenesis and response to therapy. We show that while PREX2 is dispensable for the initiation and progression of melanoma, its loss confers sensitivity to clinically relevant therapeutics. Importantly, genetic and pharmacological targeting of the RAC1 effector kinase PI3K{beta} phenocopies PREX2 loss, sensitizing our model systems to therapy. Our data reveal a druggable PREX2/RAC1/PI3K{beta} signalling axis in BRAF-mutant melanoma that could be exploited clinically. Statement of SignificanceMetastatic melanoma remains both a clinical problem, and an opportunity for therapeutic benefit. Co-targeting of the MAPK pathway and the PREX2/RAC1/PI3K{beta} has remarkable efficacy and outperforms monotherapy MAPK targeting in vivo.

cancer biology↗

bioRxiv2023

eIF4A1 is essential for reprogramming the translational landscape of Wnt-driven colorectal cancers

Dysregulated translation is a hallmark of cancer. Targeting the translational machinery represents a therapeutic avenue which is being actively explored. eIF4A inhibitors target both eIF4A1, which promotes translation as part of the eIF4F complex, and eIF4A2, which can repress translation via the CCR4-NOT complex. While high eIF4A1 expression is associated with poor patient outcome, the role of eIF4A2 in cancer remains unclear. Furthermore, the on-target toxicity of targeting specific eIF4A paralogues in healthy tissue is under-explored. We show that while loss of either paralogue is tolerated in the wild-type intestine, eIF4A1 is specifically required to support the translational demands of oncogenic Wnt signalling. Intestinal tumourigenesis is suppressed in colorectal cancer models following loss of eIF4A1 but accelerated following loss of eIF4A2, while eIF4A inhibition with eFT226 mimics loss of eIF4A1 in these models.

cancer biology↗

bioRxiv2023

Metabolic profiling stratifies colorectal cancer and reveals adenosylhomocysteinase as a therapeutic target

With colorectal cancer (CRC) being the second most common cause of cancer-related deaths worldwide1, there is an urgent need for better diagnostic tools and new, more targeted therapies. Here we used genetically engineered mouse models (GEMMs), and multimodal mass spectrometry-based metabolomics to study the impact of common genetic drivers of CRC on the metabolic landscape of the intestine. We show that unsupervised metabolic profiling can stratify intestinal tissues according to underlying genetic alterations, and use mass spectrometry imaging (MSI) to identify tumour, stromal and normal adjacent tissues. By identifying ions that drive variation between normal and transformed tissues, we found dysregulation of the methionine cycle to be a hallmark of APC-mutant CRC, and propose one of its enzymes, i.e. adenosylhomocysteinase (AHCY), as a new therapeutic target. Collectively, we show that the profound genotype-dependent alterations in both lipid and small molecule metabolism in CRC may be exploited for tissue classification with no need for ion identification, and we applied further data analysis to expose a novel metabolic vulnerability of CRC.

cancer biology↗

bioRxiv2021

Rpl24Bst mutation suppresses colorectal cancer by promoting eEF2 phosphorylation via eEF2K

Increased protein synthesis supports the rapid proliferation associated with cancer. The Rpl24Bst mutant mouse reduces the expression of the ribosomal protein RPL24 and has been used to suppress translation and limit tumorigenesis in multiple mouse models of cancer. Here we show that Rpl24Bst also suppresses tumorigenesis and proliferation in a model of colorectal cancer with two common patient mutations, Apc and Kras. In contrast to previous reports, Rpl24Bst mutation has no effect on ribosomal subunit abundance but suppresses translation elongation through phosphorylation of eEF2, reducing protein synthesis by 40% in tumour cells. Ablating eEF2 phosphorylation in Rpl24Bst mutant mice by inactivating its kinase, eEF2K, completely restores the rates of elongation and protein synthesis. Furthermore, eEF2K activity is required for the Rpl24Bst mutant to suppress tumorigenesis. This work demonstrates that elevation of eEF2 phosphorylation is an effective means to suppress colorectal tumorigenesis with two driver mutations. This positions translation elongation as a therapeutic target in colorectal cancer, as well as other cancers where the Rpl24Bst mutation has a tumour suppressive effect in mouse models.

cancer biology↗

bioRxiv2021

RASSF1C oncogene elicits amoeboid invasion, cancer stemness and invasive EVs via a novel SRC/Rho axis

Cell plasticity is a crucial hallmark leading to cancer metastasis. Upregulation of Rho/ROCK pathway drives actomyosin contractility, protrusive forces and contributes to the occurrence of highly invasive amoeboid cells in tumors. Cancer stem cells are similarly associated with metastasis, but how these populations arise in tumors is not fully understood. Here we show that the novel oncogene RASSF1C drives mesenchymal to amoeboid transition and stem cell attributes in breast cancer cells. Mechanistically, RASSF1C activates Rho/ROCK via SRC mediated RhoGDI inhibition, resulting in generation of actomyosin contractility. Moreover, we demonstrate that amoeboid cells display the cancer stem cell markers CD133, ALDH1 and the pluripotent marker Nanog; are accompanied by higher invasive potential in vitro and in vivo; and employ extracellular vesicles to transfer the invasive phenotype to target cells and tissue. Importantly, the underlying RASSF1C driven biological processes concur to explain clinical data: namely, methylation of the RASSF1C promoter correlates with better survival in early stage breast cancer patients. Therefore, we propose the use of RASSF1 gene promoter methylation status as a biomarker for patient stratification.

cancer biology↗