Biology subjects

Natesan, R.

Publications and source records attributed to Natesan, R..

7 recordsLinked to original sources

bioRxiv2026

NNMT Loss Drives Cancer Progression by enhancing SAM availability for mTORC1 Signaling and Chromatin Methylation

Aberrant epigenetic reprogramming together with dysregulated mTOR signaling are hallmarks of cancer, where altered chromatin methylation and nutrient-sensing pathways cooperate to drive tumor progression. S-adenosylmethionine (SAM), the universal methyl donor, is essential for these processes, yet how tumors sustain elevated SAM availability to support oncogenic transmethylation reactions remains poorly defined. Here, using prostate cancer (PCa) as a model system, we identify nicotinamide N-methyltransferase (NNMT) as a critical metabolic-epigenetic regulator and tumor suppressor. Using a prostate-specific Nnmt knockout mouse model, we demonstrate that NNMT loss accelerates PCa progression, particularly in the context of Pten deletion, resulting in infiltrating carcinoma and reduced survival. Mechanistically, NNMT functions as a "SAM-sink," and its loss increases intracellular SAM abundance, thereby activating mTORC1 signaling through SAMTOR-dependent sensing and broadly enhancing chromatin methylation. In human PCa, recurrent genomic deletions of NNMT occur in up to 7% of cases, and NNMT protein expression is largely absent in primary tumors and metastases. NNMT-deficient PCa cells exhibit elevated SAM:SAH ratios, increased histone methylation, and heightened mTORC1 activity, enabling sustained tumor growth even under dietary methionine-restriction (MR). Notably, combined MR and pharmacologic mTORC1 inhibition synergistically suppresses the growth of NNMT-deficient tumors, revealing a previously unrecognized therapeutic vulnerability. Collectively, these findings establish NNMT as a key tumor suppressor that constrains SAM-driven epigenetic and signaling programs in PCa and suggest a rational, diet-based therapeutic strategy for advanced cancers with NNMT loss.

cancer biology↗

bioRxiv2026

Modeling Microbiome Modulation of Tumor Metabolic Networks to Predict Synergistic Therapies

Differences in microbiome composition profoundly influence drug response, yet methods to model the metabolic interplay between tumors, microbes, and therapeutics remain limited. We present a generalizable framework combining machine-learning and genome-scale metabolic modeling to prioritize combination therapies for colorectal cancer (CRC) in the presence of Fusobacterium nucleatum (Fn) and other pathogenic, probiotic, and commensal microbes. Trained on 6,514 drug combinations in microbe-free CRC cell lines, the model predicted synergistic combinations in both microbe-free and microbe-associated contexts and generalized to immunotherapy-associated conditions. Predictions were validated using an asymmetric co-culture system that mimics the colons normoxic-anaerobic gradient, confirming synergistic combinations in HCT116 cells with Fn, including drugs not typically used in CRC therapy. Mechanistic analysis and targeted pharmacological perturbations revealed phospho-inositol metabolism and cysteine transport as key determinants of Fn-dependent drug synergy. Together, this work introduces a scalable, microbiome-aware framework to enable discovery of context-specific combination therapies.

bioinformatics↗

bioRxiv2022

Setd2 inactivation sensitizes lung adenocarcinoma to inhibitors of oxidative respiration and mTORC1 signaling

SETD2 is a tumor suppressor that is frequently inactivated in several cancer types. The mechanisms through which SETD2 inactivation promotes cancer are unclear, and whether targetable vulnerabilities exist in these tumors is unknown. Here we identify heightened mTORC1-associated gene expression programs and functionally higher levels of oxidative metabolism and protein synthesis as prominent consequences of Setd2 inactivation in KRAS-driven mouse models of lung adenocarcinoma. Blocking oxidative respiration and mTORC1 signaling abrogates the high rates of tumor cell proliferation and tumor growth specifically in SETD2-deficient tumors. Our data nominate SETD2 deficiency as a functional marker of sensitivity to clinically actionable therapeutics targeting oxidative respiration and mTORC1 signaling.

cancer biology↗

bioRxiv2021

Oncofusion-driven de novo enhancer assembly promotes malignancy in Ewing sarcoma via aberrant expression of the stereociliary protein LOXHD1

Ewing Sarcoma (EwS) is a highly aggressive tumor of bone and soft tissues that mostly affects children and adolescents. The pathognomonic oncofusion EWSR1-ETS (EWSR1-FLI1/EWSR1-ERG) transcription factors drive EwS by orchestrating an oncogenic transcription program through de novo enhancers. Pharmacological targeting of these oncofusions has been challenged by unstructured prion-like domains and common DNA binding domains in the EWSR1 and ETS protein, respectively. Alternatively, identification and characterization of mediators and downstream targets of EWSR1-FLI1 dependent or independent function could offer novel therapeutic options. By integrative analysis of thousands of transcriptome datasets representing pan-cancer cell lines, primary cancer, metastasis, and normal tissues, we have identified a 32 gene signature (ESS32 - Ewing Sarcoma Specific 32) that could stratify EwS from pan-cancer. Of the ESS32, LOXHD1 - that encodes a stereociliary protein, was the most exquisitely expressed gene in EwS. CRISPR-Cas9 mediated deletion or silencing of EWSR1-FLI1 bound upstream de novo enhancer elements in EwS cells led to the loss of LOXHD1 expression and altered the EWSR1-FLI1, MYC, and HIF1 pathway genes, resulting in decreased proliferation and invasion in vitro and in vivo. These observations implicate LOXHD1 as a novel biomarker and a major determinant of EwS metastasis and open up new avenues for developing LOXHD1-targeted drugs or cellular therapies for this deadly disease.

cancer biology↗

bioRxiv2020

Targeting androgen regulation of TMPRSS2 and ACE2 as a therapeutic strategy to combat COVID-19

Epidemiological data showing increased severity and mortality of COVID-19 in men suggests a potential role for androgen in SARS-CoV-2 infection. Here, we present evidence for the transcriptional regulation of SARS-CoV-2 host cell receptor ACE2 and TMPRSS2 by androgen in mouse and human cells. Additionally, we demonstrate the endogenous interaction between TMPRSS2 and ACE2 in human cells and validate ACE2 as a TMPRSS2 substrate. Further, Camostat - a TMPRSS2 inhibitor, blocked the cleavage of pseudotype SARS-CoV-2 surface Spike without disrupting TMPRSS2-ACE2 interaction. Thus providing evidence for the first time a direct role of TMPRSS2 in priming the SARS-CoV-2 Spike, required for viral fusion to the host cell. Importantly, androgen-deprivation, anti-androgens, or Camostat attenuated the SARS-CoV-2 S-mediated cellular entry. Together, our data provide a strong rationale for clinical evaluations of TMPRSS2 inhibitors, androgen-deprivation therapy/androgen receptor antagonists alone or in combination with antiviral drugs as early as clinically possible to prevent COVID-19 progression.

molecular biology↗

bioRxiv2020

Thymidylate synthase drives the phenotypes of epithelial-to-mesenchymal transition in non-small cell lung cancer

BackgroundEpithelial-to-mesenchymal transition (EMT) enhances motility, stemness and chemoresistance of carcinomas and is an important determinant of metastasis. Little is known about how various pathways coordinate to elicit EMTs different functional aspects. Even lesser has been studied in this context in non-small cell lung cancer (NSCLC), where EMT is a key event during early tumorigenesis. Thymidylate synthase (TS), a proliferation enzyme, has been previously correlated with EMT transcription factor ZEB1 in NSCLC and is associated with resistance against anti-folate chemotherapy. In this study we establish a functional correlation between TS, EMT, chemotherapy and metastasis and identify a network that might propel the TS mediated EMT phenotype. MethodsPublished datasets were analysed to evaluate significance of TS in NSCLC fitness and prognosis. mCherry based promoter reporter assay was used to sort Calu-1 and A549 NSCLC cells in TSHIGH and TSLOW. Metastatic potential of TS knock-down was assayed in syngeneic C57BL/6 mice. ResultsLow TS levels were prognostic and predicted chemotherapy response. NSCLC cell lines with higher TS promoter activity were more mesenchymal-like. RNA-seq from these cells, and shRNA mediated TS knocked down cells, identified EMT as one of the most differentially regulated pathways. EMT transcription factors HOXC6 and HMGA2 were identified as upstream regulator of TS whereas, AXL, SPARC and FOSL1 were identified as downstream effectors. TS knock-down reduced the metastatic colonisation in vivo. ConclusionThese results establish the role of TS as a theranostic NSCLC marker integrating survival, chemo-resistance and EMT, and identifies a regulatory network that could be exploited to target EMT-driven NSCLC.

cancer biology↗

bioRxiv2020

Exploration of endogenous miRNA-200b/c activity and regulation through a functional dual fluorescence reporter

Since their discovery, microRNAs (miRNA)s have been widely studied in almost every aspect of biology and medicine, leading to the identification of important gene regulation circuits and cellular mechanisms. However, investigations are generally focused on the analysis of their downstream targets and biological functions in overexpression and knockdown approaches, while miRNAs endogenous levels and activity remain poorly understood. Here, we used the cellular plasticity-regulating process of epithelial-to-mesenchymal transition (EMT) as a model to show the efficacy of a fluorescent sensor to separate cells with distinct EMT signatures, based on miR-200b/c activity. The system was further combined with a CRISPR-Cas9 screening platform to unbiasedly identify miR-200b/c upstream regulating genes. The sensor allows to infer miRNAs fundamental biological properties, as profiling of sorted cells indicated miR-200b/c as a molecular switch between EMT differentiation and proliferation, and suggested a role for metabolic enzymes in miR-200/EMT regulation. Analysis of miRNAs endogenous levels and activity could lead to a better understanding of their biological role in physiology and disease.

molecular biology↗