Biology subjects

Medova, M.

Publications and source records attributed to Medova, M..

3 recordsLinked to original sources

bioRxiv2023

HPV and p53 status as precision determinants of head and neck cancer response to DNA-PKcs inhibition in combination with irradiation

Major risk factors of head and neck squamous cell carcinoma (HNSCC) are tobacco use and human papillomavirus (HPV). HPV E6 oncoprotein leads to the degradation of the p53 protein, whereas HPV-negative cancers are frequently associated with TP53 mutations. Peposertib is a potent and selective, orally administered small-molecule inhibitor of the catalytic subunit of the DNA-dependent kinase (DNA-PKcs), a key regulator of non-homologous end joining (NHEJ). NHEJ inhibition along with irradiation (IR)-induced DNA double-strand breaks has the potential to increase antitumor treatment efficacy. Here, we investigated the responses of HNSCC models with distinct HPV and p53 status to treatments with IR, DNA-PKcs inhibition, and their combination. We observed that IR-induced DNA damage combined with peposertib administration shortly before IR results in decreased cell viability and proliferation and causes DNA repair delay in all the studied HNSCC cell lines. However, our data confirm that the actual cell fate upon this treatment is strongly dependent on cellular p53/HPV status. Cells lacking functional p53 due to its degradation by HPV or due to the presence of a loss-of-function mutation are arrested in the G2 phase of the cell cycle and eliminated by apoptosis whereas p53-proficient HNSCC cell lines undergo senescence. Consequently, HPV+ cancer cell lines and xenografts display stronger and more durable responses and seem to benefit from the combined treatment more than p53-proficient HNSCCs. In conclusion, DNA-PKcs inhibitor peposertib should be further studied as a potential radiosensitizer for HNSCCs, taking into consideration the genetic background and the HPV status of a particular tumor.

cancer biology↗

bioRxiv2021

Tumour mutations in long noncoding RNAs that enhance cell fitness

Long noncoding RNAs (lncRNAs) can act as tumour suppressors or oncogenes to repress/promote tumour cell proliferation via RNA-dependent mechanisms. Recently, genome sequencing has identified elevated densities of tumour somatic single nucleotide variants (SNVs) in lncRNA genes. However, this has been attributed to phenotypically-neutral "passenger" processes, and the existence of positively-selected fitness-altering "driver" SNVs acting via lncRNAs has not been addressed. We developed and used ExInAtor2, an improved driver-discovery pipeline, to map pancancer and cancer-specific mutated lncRNAs across an extensive cohort of 2583 primary and 3527 metastatic tumours. The 54 resulting lncRNAs are mostly linked to cancer for the first time. Their significance is supported by a range of clinical and genomic evidence, and display oncogenic potential when experimentally expressed in matched tumour models. Our results revealed a striking SNV hotspot in the iconic NEAT1 oncogene, which was ascribed by previous studies to passenger processes. To directly evaluate the functional significance of NEAT1 SNVs, we used in cellulo mutagenesis to introduce tumour-like mutations in the gene and observed a consequent increase in cell proliferation in both transformed and normal backgrounds. Mechanistic analyses revealed that SNVs alter NEAT1 ribonucleoprotein assembly and boost subnuclear paraspeckles. This is the first experimental evidence that mutated lncRNAs can contribute to the pathological fitness of tumour cells.

genomics↗

bioRxiv2020

Enhancing CRISPR deletion via pharmacological delay of DNA-PK

CRISPR-Cas9 deletion (CRISPR-del) is the leading approach for eliminating DNA from mammalian cells and underpins a variety of genome-editing applications. Target DNA, defined by a pair of double strand breaks (DSBs), is removed during non-homologous end-joining (NHEJ). However, the low efficiency of CRISPR-del results in laborious experiments and false negative results. Using an endogenous reporter system, we demonstrate that temporary inhibition of DNA-dependent protein kinase (DNA-PK) - an early step in NHEJ - yields up to 17-fold increase in DNA deletion. This is observed across diverse cell lines, gene delivery methods, commercial inhibitors and guide RNAs, including those that otherwise display negligible activity. Importantly, the method is compatible with pooled functional screens employing lentivirally-delivered guide RNAs. Thus, delaying the kinetics of NHEJ relative to DSB formation is a simple and effective means of enhancing CRISPR-deletion.

molecular biology↗