Biology subjects

Hassan, O.

Publications and source records attributed to Hassan, O..

5 recordsLinked to original sources

bioRxiv2024

BUB1 regulates non-homologous end joining pathway to mediate radioresistance in triple-negative breast cancer

BackgroundTriple-negative breast cancer (TNBC) is a highly aggressive form of breast cancer subtype often treated with radiotherapy (RT). Due to its intrinsic heterogeneity and lack of effective targets, it is crucial to identify novel molecular targets that would increase RT efficacy. Here we demonstrate the role of BUB1 (cell cycle Ser/Thr kinase) in TNBC radioresistance and offer a novel strategy to improve TNBC treatment. MethodsGene expression analysis was performed to look at genes upregulated in TNBC patient samples compared to other subtypes. Cell proliferation and clonogenic survivals assays determined the IC50 of BUB1 inhibitor (BAY1816032) and radiation enhancement ratio (rER) with pharmacologic and genomic BUB1 inhibition. Mammary fat pad xenografts experiments were performed in CB17/SCID. The mechanism through which BUB1 inhibitor sensitizes TNBC cells to radiotherapy was delineated by {gamma}-H2AX foci assays, BLRR, Immunoblotting, qPCR, CHX chase, and cell fractionation assays. ResultsBUB1 is overexpressed in BC and its expression is considerably elevated in TNBC with poor survival outcomes. Pharmacological or genomic ablation of BUB1 sensitized multiple TNBC cell lines to cell killing by radiation, although breast epithelial cells showed no radiosensitization with BUB1 inhibition. Kinase function of BUB1 is mainly accountable for this radiosensitization phenotype. BUB1 ablation also led to radiosensitization in TNBC tumor xenografts with significantly increased tumor growth delay and overall survival. Mechanistically, BUB1 ablation inhibited the repair of radiation-induced DNA double strand breaks (DSBs). BUB1 ablation stabilized phospho-DNAPKcs (S2056) following RT such that half-lives could not be estimated. In contrast, RT alone caused BUB1 stabilization, but pre-treatment with BUB1 inhibitor prevented stabilization (t1/2, [~]8 h). Nuclear and chromatin-enriched fractionations illustrated an increase in recruitment of phospho- and total-DNAPK, and KAP1 to chromatin indicating that BUB1 is indispensable in the activation and recruitment of non-homologous end joining (NHEJ) proteins to DSBs. Additionally, BUB1 staining of TNBC tissue microarrays demonstrated significant correlation of BUB1 protein expression with tumor grade. ConclusionsBUB1 ablation sensitizes TNBC cell lines and xenografts to RT and BUB1 mediated radiosensitization may occur through NHEJ. Together, these results highlight BUB1 as a novel molecular target for radiosensitization in women with TNBC.

cancer biology↗

bioRxiv2024

BUB1 inhibition sensitizes lung cancer cell lines to radiotherapy and chemoradiotherapy

BackgroundLung cancer is a major public health concern, with high incidence and mortality. Despite advances in targeted therapy and immunotherapy, microtubule stabilizers (paclitaxel, docetaxel), DNA intercalating platinum drugs (cisplatin) and radiation therapy continue to play a critical role in the management of locally advanced and metastatic lung cancer. Novel molecular targets would provide opportunities for improving the efficacies of radiotherapy and chemotherapy. HypothesisWe hypothesize that BUB1 (Ser/Thr kinase) is over-expressed in lung cancers and that its inhibition will sensitize lung cancers to chemoradiation. MethodsBUB1 inhibitor (BAY1816032) was combined with platinum (cisplatin), microtubule poison (paclitaxel), a PARP inhibitor (olaparib) and radiation in cell proliferation and radiation sensitization assays. Biochemical and molecular assays were used to evaluate their impact on DNA damage signaling and cell death mechanisms. ResultsBUB1 expression assessed by immunostaining of lung tumor microarrays (TMAs) confirmed higher BUB1 expression in NSCLC and SCLC compared to that of normal tissues. BUB1 overexpression in lung cancer tissues correlated directly with expression of TP53 mutations in non-small cell lung cancer (NSCLC). Elevated BUB1 levels correlated with poorer overall survival in NSCLC and small cell lung cancer (SCLC) patients. A BUB1 inhibitor (BAY1816032) synergistically sensitized lung cancer cell lines to paclitaxel and olaparib. Additionally, BAY1816032 enhanced cell killing by radiation in both NSCLC and SCLC. Molecular changes following BUB1 inhibition suggest a shift towards pro-apoptotic and anti-proliferative states, indicated by altered expression of BAX, BCL2, PCNA, and Caspases 9 and 3. ConclusionA direct correlation between BUB1 protein expression and overall survival was shown. BUB1 inhibition sensitized both NSCLC and SCLC to various chemotherapies (cisplatin, paclitaxel) and targeted therapy (PARPi). Furthermore, we present the novel finding that BUB1 inhibition sensitized both NSCLC and SCLC to radiotherapy and chemoradiation. Our results demonstrate BUB1 inhibition as a promising strategy to sensitize lung cancers to radiation and chemoradiation therapies.

cancer biology↗

bioRxiv2024

Heterochromatin spreading in cancer cells through HDAC7 mediated histone H3.3 landscape reprogramming.

Class IIa histone deacetylases (HDACs) are a family of enzymes with minimal histone deacetylase activity but can function as multi-protein interaction hubs. Here we demonstrate the expression of HDAC7, a Class IIa HDAC family member, in glioblastoma tumor tissue from 84 patients, patient-derived glioma stem cells (GSCs) from six patients, and pediatric diffuse pontine glioma (DIPG) cells from three patients. HDAC7 binds to Histone H3.3 and interacts with H3.3 and HIRA on chromatin. Targeted downregulation of HDAC7 expression with a subtype-specific siRNA inhibits the interaction of H3.3 with HIRA while increasing the association of H3.3 with DAXX and H3K9me3. This results in H3.3 being deposited on H3K9me3+/DAPI+ heterochromatin nuclear foci. Inhibition of HDAC7 triggers H3K9me3+ heterochromatin spreading, increased H3K9me3 binding in the cancer genome, and significant alterations in gene expression. Using single molecule DNA fiber approach, we show that HDAC7 inhibition results in a significant increase in replication fork speed without affecting fork symmetry. This altered replication fork speed leads to replication stress, evidenced by phosphorylation of RPA2 and impact on global DNA synthesis, resulting in reduced EdU incorporation. Finally, HDAC7 depletion leads to reduced BRCA2 expression and increased sensitivity of cancer cells to DNA damaging agents. Taken together, these studies uncover the involvement of HDAC7 in the euchromatic H3.3 chaperone network and the effect of HDAC7 depletion on chromatin dynamics, inducing epigenetic restriction and DNA damage in cancer cells.

cancer biology↗

bioRxiv2021

A conserved trans regulatory loop involving an odorant binding protein controls male mating behavior in flies

Y chromosomes have male-limited inheritance, which favors the fixation of alleles that affect spermatogenesis, courtship, and other male-specific traits. Y-linked male-beneficial alleles can also have female-deleterious (sexually antagonistic) effects because they never experience direct selection in females. However, determining the mechanisms underlying these male-beneficial effects is challenging because it can require studying Y-linked alleles while they still segregate as polymorphism. We used a Y chromosome polymorphism in the house fly, Musca domestica, to address this challenge. Two common male-determining Y chromosomes (YM and IIIM) segregate as stable polymorphisms in natural house fly populations, and they differentially affect multiple traits, including male courtship performance. We performed a meta-analysis of RNA-seq data and identified differentially expressed genes encoding odorant binding proteins (in the Obp56h family) as candidate causal agents in the courtship differences. The Obp56h genes are not found on either the YM or IIIM chromosomes, suggesting that they must be regulated in trans by one of the house fly sex chromosomes. Using a network analysis and allele-specific expression measurements, we identified multiple genes on the house fly IIIM chromosome that could serve as trans inhibitors of Obp56h gene expression. One of those genes is homologous to D. melanogaster CG2120, which encodes a transcription factor that binds both up- and down-stream of Obp56h. We found that up-regulation of CG2120 in D. melanogaster nervous tissues reduces copulation latency, consistent with this transcription factor acting as a negative regulator of Obp56h expression. We propose the name speed date (spdt) for CG2120, with the house fly homolog named Md-spdt. The expression of spdt across D. melanogaster development and tissues suggests that evolution of higher expression in neurons may be constrained by pleiotropic or sexual antagonistic effects. We hypothesize that a cis-regulatory allele that increases expression of Md-spdt on the IIIM chromosome exists because Y-linkage of this allele releases it from those constraints. This provides evidence for a molecular mechanism by which a Y-linked gene can evolve a male-beneficial function regardless of the negative effects on females.

evolutionary biology↗

bioRxiv2020

Olfactory transmucosal SARS-CoV-2 invasion as port of Central Nervous System entry in COVID-19 patients

The newly identified severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, a pandemic respiratory disease presenting with fever, cough, and often pneumonia. Moreover, thromboembolic events throughout the body including the central nervous system (CNS) have been described. Given first indication for viral RNA presence in the brain and cerebrospinal fluid and in light of neurological symptoms in a large majority of COVID-19 patients, SARS-CoV-2-penetrance of the CNS is likely. By precisely investigating and anatomically mapping oro- and pharyngeal regions and brains of 32 patients dying from COVID-19, we not only describe CNS infarction due to cerebral thromboembolism, but also demonstrate SARS-CoV-2 neurotropism. SARS-CoV-2 enters the nervous system via trespassing the neuro-mucosal interface in the olfactory mucosa by exploiting the close vicinity of olfactory mucosal and nervous tissue including delicate olfactory and sensitive nerve endings. Subsequently, SARS-CoV-2 follows defined neuroanatomical structures, penetrating defined neuroanatomical areas, including the primary respiratory and cardiovascular control center in the medulla oblongata.

neuroscience↗