Biology subjects

Geethadevi, A.

Publications and source records attributed to Geethadevi, A..

6 recordsLinked to original sources

bioRxiv2026

Mirdametinib and abemaciclib cooperate in atypical teratoid rhabdoid tumor to decrease proliferation and suppress tumor growth

Atypical teratoid rhabdoid tumor (ATRT) is a malignant brain tumor of children that has an overall survival of less than 40 percent even with aggressive therapy. We identified upregulation of the mitogen activated protein (MAP) kinase pathway in ATRT. The novel, brain-penetrant MEK inhibitor mirdametinib inhibited the growth of ATRT cell lines in culture at nanomolar concentrations. Mirdametinib suppressed proliferation as measured by BrdU incorporation and induced apoptosis as measured by cPARP and Annexin V staining. Monotherapy with mirdametinib extended the life of mice bearing orthotopic xenografts. Combination therapy with the brain-penetrant cyclin dependent kinase 4/6 inhibitor abemaciclib further suppressed growth and BrdU incorporation in ATRT cell lines representing all molecular subgroups. Mirdametinib and abemaciclib combined to extend survival of mice bearing orthotopic ATRT xenografts. In conclusion, mirdametinib has single agent activity against ATRT and combines with abemaciclib to decrease proliferation and extend survival in orthotopic xenograft models of ATRT.

cancer biology↗

bioRxiv2026

MRPL47 as a Novel Mitochondrial Biomarker for Early Detection and Therapeutic Response in Ovarian Cancer

MRPL47 (Mitochondrial Ribosomal Protein Large Subunit 47) gene in chromosome 3q26 encodes a protein that is part of the large subunit of the mitochondrial ribosome. We observed that MRPL47 is frequently amplified and overexpressed in ovarian cancer samples. Importantly, increased expression of MRPL47 mRNA is associated with high levels of MRPL47 protein in ovarian cancer patients. High expression of MRPL47 is also associated with poor overall and recurrence free survival of ovarian cancer patients. Notably, MRPL47 improved metabolic fitness by enhancing cellular respiration, and glycolysis in cancer cells. Gene set enrichment analysis and target specific knockdown assays revealed that MYC transcription factor regulates MRPL47 expression. Furthermore, MRPL47 was identified very high in the plasma samples of ovarian cancer patients compared to those of healthy volunteers. MRPL47 was also associated with cisplatin resistance, whereas its expression predicted sensitivity to cisplatin therapy. Taken together, we demonstrated that MRPL47 can be used as a diagnostic biomarker for ovarian cancer and other cancers with 3q26 chromosomal amplification.

cancer biology↗

bioRxiv2024

The CoREST complex inhibitor, corin, leads to decreased tumor growth, increased cellular differentiation and extended lifespan in atypical teratoid rhabdoid tumor xenograft models

BackgroundAtypical teratoid rhabdoid tumor (ATRT) is the most common malignant brain tumor in infants, and more than 60% of children with ATRT die from their tumor. ATRT is associated with mutational inactivation/deletion of SMARCB1, a member of the SWI/SNF chromatin remodeling complex, suggesting that epigenetic events play a critical role in tumor development and progression. Moreover, disruption of SWI/SNF allows unopposed activity of epigenetic repressors, which contribute to tumorigenicity. We therefore explored the role of the CoREST repressor complex in ATRT. MethodsWe evaluated the effects of the bifunctional LSD1/HDAC1/2 small molecule CoREST inhibitor, corin, on ATRT tumor cell growth, apoptosis, differentiation, gene expression and chromatin accessibility. ResultsWe found that corin inhibited the growth of ATRT cells regardless of their epigenetic subgroup, and was associated with increased tumor cell apoptosis and differentiation. ATAC-seq showed increases in chromatin accessibility in corin-treated ATRT cells, with changes seen at genes associated with neuronal differentiation and synaptic function. RNA-seq confirmed increased expression of neuronal differentiation genes and decreased DNA replication/cell cycle-associated genes in ATRT cells treated with corin. Corin suppressed orthotopic ATRT tumor growth, leading to significant extension of lifespan. In addition, increased histone acetylation (H3K9ac, H3K27ac) and methylation (H3K4Me1) was seen in corin-treated ATRT orthotopic xenografts, consistent with on-target pharmacodynamics. ConclusionThe CoREST inhibitor, corin, suppresses tumor growth, induces differentiation, and promotes apoptosis in ATRT, leading to significantly increased survival of mice bearing ATRT orthotopic xenografts. Our results suggest a potential application of CoREST complex inhibitors in patients with ATRT. Key PointsO_LICoREST complex inhibition by corin leads to decreased cell growth and increased apoptosis in ATRT C_LIO_LICorin promotes chromatin accessibility and neuronal differentiation in ATRT C_LIO_LICorin inhibits tumor growth and extends lifespan in ATRT animal models C_LI Importance of the StudyLoss of function of SMARCB1 is a hallmark of ATRT which leads to dysfunction of the mammalian SWI/SNF complex and an inability to counteract epigenetic repressor complexes. The CoREST complex functions as a chromatin remodeling complex that represses neuronal differentiation genes during development. Inhibition of the CoREST complex by corin in ATRT leads to decreased tumor cell growth, induction of apoptosis and increased survival of mice bearing ATRT orthotopic xenografts. These changes are associated with increased chromatin accessibility and expression of genes associated with neuronal differentiation. Corin therefore reverses the primary block of differentiation that maintains a stem cell state in ATRT, which contributes to tumorigenesis. These studies significantly improve our understanding of how to therapeutically address the underlying epigenetic drivers of ATRT and support further development of corin for ATRT.

cancer biology↗

bioRxiv2024

CoREST Complex Inhibition Alters RNA Splicing to Promote Neoantigen Expression and Enhance Tumor Immunity

ABSTRACTEpigenetic complexes tightly regulate gene expression and colocalize with RNA splicing machinery; however, the consequences of these interactions are uncertain. Here, we identify unique interactions of the CoREST repressor complex with RNA splicing factors and their functional consequences in tumorigenesis. Using mass spectrometry, in vivo binding assays, and cryo-EM we find that CoREST complex-splicing factor interactions are direct and perturbed by the CoREST complex inhibitor, corin, leading to extensive changes in RNA splicing in melanoma and other malignancies. Using predictive machine learning models and MHC IP-MS, we identify thousands of corin-induced neopeptides derived from unannotated splice sites which generate immunogenic splice-neoantigens. Furthermore, corin reactivates the response to immune checkpoint blockade and promotes dramatic expansion of cytotoxic T cells in an immune cold melanoma model. CoREST complex inhibition thus represents a unique therapeutic opportunity in cancer which creates tumor-associated neoantigens that enhance the immunogenicity of current therapeutics. Statement of SignificanceWe identify a novel role of the CoREST transcriptional repressor complex in regulating pre-mRNA splicing and find that the small molecule inhibitor, corin, promotes alternative splicing events in cancer leading to neoantigen expression and T cell-mediated immunity. This represents a potential approach to promote immunoreactive neoantigen expression in immune-cold tumors.

cancer biology↗

bioRxiv2024

Eukaryotic Translation Initiation Factor Loaded Extracellular Vesicles Promotes Macrophage Cholesterol Metabolism in ovarian cancer

Tumor-driven immune suppression poses a significant impediment to the success of immunotherapy in ovarian cancer. Among the various mechanisms contributing to immune suppression, intracellular communication facilitated by tumor-derived extracellular vesicles (EVs) within the tumor microenvironment (TME) emerges as a pivotal factor influencing tumor growth. We discovered that EVs from both ovarian tumor cell lines and the plasma of ovarian cancer patients are encapsulated with eukaryotic translation initiation factor 4E (eIF4E). Our study revealed a new mechanism showing how these EVs are loaded with eIF4E and its impact on ovarian cancer progression. We also demonstrated that eIF4E-containing EVs (eIF4E-EVs) alter protein translation in macrophages, contributing to anti-tumor immune response. Treatment of macrophages with eIF4E-EVs induces an immunosuppressive phenotype marked by the release of cytokines such as IL-6 and an elevated expression of Programmed death-ligand 1 (PD-L1). Notably, eIF4E-packaged EVs enhance the expression of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) a pivotal enzyme in cholesterol biosynthesis, resulting in increased cholesterol levels within macrophages. Inhibition of HMGCR or reduction of cholesterol in macrophages effectively restores their antitumor activity by decreasing PD-L1 on macrophages. Analysis of tumor tissue from ovarian cancer patients revealed a positive correlation between HMGCR and TAM in ovarian cancer. In summary, we have characterized the mechanism of how eIF4E loaded EVs induced cholesterol synthesis, creating an immunosuppressive environment by upregulating PD-L1 expression in macrophages.

cancer biology↗

bioRxiv2020

RNA-binding protein FXR1 drives cMYC translation by mRNA circularization through eIF4F recruitment in ovarian cancer

BackgroundThe RNA-binding protein FXR1 (fragile X-related protein 1) has been implicated as an important regulator of post-transcriptional changes of mRNAs. However, its role in mRNA circularization and recruitment of eukaryotic translation initiation factors for protein translation remains obscure. Here, we aimed to investigate the molecular mechanisms and potential clinical applications of FXR1 in ovarian cancer growth and progression. MethodsFXR1 copy number variation, mRNA expression, protein levels, and their association with prognosis were determined in clinical datasets. An orthotopic ovarian cancer model and bioluminescence imaging were used for preclinical evaluation of FXR1 in vivo. Reverse phase protein arrays (RPPA) and qPCR arrays were performed to identify FXR1s key targets and downstream effects. SUnSET and polysome profiling were used to determine the translational effects of FXR1. Immunoprecipitation and immunofluorescence were performed to identify the interaction between FXR1 and cMYC mRNA and eIF4F complex. RNA-immunoprecipitation (RIP), RNA electrophoretic mobility shift assays (REMSA), proximity ligation assays (PLA), and biochemical assays were used to identify the specific site on cMYC mRNA to which FXR1 binds to promote mRNA circularization and translation. ResultsWe found that amplification and copy-gain of FXR1 increased the expression of FXR1 mRNA and FXR1 protein in ovarian cancer patients, and these events associated with poor prognosis. We demonstrated that FXR1 binds to AU-rich elements (ARE) within the 3 untranslated region (3UTR) of cMYC. As a consequence, FXR1 binding to cMYC 3UTR leads to the circularization of mRNA and facilitated the recruitment of eukaryotic translation initiation factors (eIFs) to translation start site for improving protein synthesis. ConclusionWe found that FXR1 upregulates a known oncogene, cMYC, by binding to AU-rich elements within the 3UTR, leading to the recruitment of the eIF4F complex for cMYC translation. Our findings uncover a novel mechanism of action of FXR1 in tumorigenesis and provides opportunities to use FXR1 and its downstream effectors as biomarkers or therapeutic targets in ovarian and other cancers.

cancer biology↗