Biology subjects

Tangudu, N. K.

Publications and source records attributed to Tangudu, N. K..

4 recordsLinked to original sources

bioRxiv2024

αKG-mediated carnitine synthesis promotes homologous recombination via histone acetylation

Homologous recombination (HR) deficiency enhances sensitivity to DNA damaging agents commonly used to treat cancer. In HR-proficient cancers, metabolic mechanisms driving response or resistance to DNA damaging agents remain unclear. Here we identified that depletion of alpha-ketoglutarate (KG) sensitizes HR-proficient cells to DNA damaging agents by metabolic regulation of histone acetylation. KG is required for the activity of KG-dependent dioxygenases (KGDDs), and prior work has shown that changes in KGDD affect demethylases. Using a targeted CRISPR knockout library consisting of 64 KGDDs, we discovered that Trimethyllysine Hydroxylase Epsilon (TMLHE), the first and rate-limiting enzyme in de novo carnitine synthesis, is necessary for proliferation of HR-proficient cells in the presence of DNA damaging agents. Unexpectedly, KG-mediated TMLHE-dependent carnitine synthesis was required for histone acetylation, while histone methylation was affected but dispensable. The increase in histone acetylation via KG-dependent carnitine synthesis promoted HR-mediated DNA repair through site- and substrate-specific histone acetylation. These data demonstrate for the first time that HR-proficiency is mediated through KG directly influencing histone acetylation via carnitine synthesis and provide a metabolic avenue to induce HR-deficiency and sensitivity to DNA damaging agents.

cancer biology↗

bioRxiv2023

Paracrine effects of the senescence-associated secretory phenotype decrease cancer cell adhesion

Cellular senescence, characterized by a stable cell cycle arrest, is a well-documented consequence of several widely used chemotherapeutics that has context-dependent roles in cancer. Although senescent cells are non-proliferative, they remain biologically active and secrete a complex and diverse array of factors collectively known as the se-nescence-associated secretome (SAS), which exerts pro-tumorigenic effects. Here, we aimed to mechanistically investigate how the SAS contributes to metastatic dissemination of high grade serous ovarian cancer (HGSOC) using standard-of-care cisplatin as a se-nescence inducer. Our findings demonstrate that the cisplatin-induced SAS enhances the dissemination of HGSOC in vivo without affecting cell proliferation or viability. We found that the SAS facilitates cell detachment, an effect that is mediated by a metabolic com-ponent. Using a metabolically focused CRISPR knockout screen, we identified complex I as the key driver of SAS-mediated cell detachment in bystander cells and validated that inhibition of complex I activity decreases HGSOC dissemination in vivo. Mechanistically, this effect was driven by SAS-mediated inhibition of an NAD+-SIRT-SREBP axis, leading to decreased plasma membrane cholesterol that increased cell detachment. Excitingly, we found that fructose is the key SAS component upstream of the NAD+-SIRT-SREBP-cholesterol axis mediating increased detachment of bystander cells, and a high fructose diet increases HGSOC dissemination in vivo. These findings reveal that the cisplatin-induced SAS reprograms the metabolic microenvironment in HGSOC, driving cancer cell detachment and promoting metastatic dissemination in a paracrine fashion. They also point to a previously unrecognized pro-tumorigenic effect of the SAS that may contribute to the high recurrence rate of HGSOC patients.

cancer biology↗

bioRxiv2023

ATR promotes mTORC1 activation via de novo cholesterol synthesis in p16-low cancer cells

DNA damage and cellular metabolism exhibit a complex interplay characterized by bidirectional feedback mechanisms. Key mediators of the DNA damage response and cellular metabolic regulation include Ataxia Telangiectasia and Rad3-related protein (ATR) and the mechanistic Target of Rapamycin Complex 1 (mTORC1), respectively. Previous studies have established ATR as a regulatory upstream factor of mTORC1 during replication stress; however, the precise mechanisms by which mTORC1 is activated in this context remain poorly defined. Additionally, the activity of this signaling axis in unperturbed cells has not been extensively investigated. Here, we demonstrate that ATR promotes mTORC1 activity across various cellular models under basal conditions. This effect is particularly enhanced in cells following the loss of p16, which we have previously associated with hyperactivation of mTORC1 signaling and here found have increased ATR activity. Mechanistically, we found that ATR promotes de novo cholesterol synthesis and mTORC1 activation through the upregulation of lanosterol synthase (LSS), independently of both CHK1 and the TSC complex. Furthermore, the attenuation of mTORC1 activity resulting from ATR inhibition was rescued by supplementation with lanosterol or cholesterol in multiple cellular contexts. This restoration corresponded with enhanced localization of mTOR to the lysosome. Collectively, our findings demonstrate a novel connection linking ATR and mTORC1 signaling through the modulation of cholesterol metabolism.

cancer biology↗

bioRxiv2023

De novo purine metabolism is a metabolic vulnerability of cancers with low p16 expression

p16 is a tumor suppressor encoded by the CDKN2A gene whose expression is lost in [~]50% of all human cancers. In its canonical role, p16 inhibits the G1-S phase cell cycle progression through suppression of cyclin dependent kinases. Interestingly, p16 also has roles in metabolic reprogramming, and we previously published that loss of p16 promotes nucleotide synthesis via the pentose phosphate pathway. Whether other nucleotide metabolic genes and pathways are affected by p16/CDKN2A loss and if these can be specifically targeted in p16/CDKN2A-low tumors has not been previously explored. Using CRISPR KO libraries in multiple isogenic human and mouse melanoma cell lines, we determined that many nucleotide metabolism genes are negatively enriched in p16/CDKN2A knockdown cells compared to controls. Indeed, many of the genes that are required for survival in the context of low p16/CDKN2A expression based on our CRISPR screens are upregulated in p16 knockdown melanoma cells and those with endogenously low CDKN2A expression. We determined that cells with low p16/Cdkn2a expression are sensitive to multiple inhibitors of de novo purine synthesis, including anti-folates. Tumors with p16 knockdown were more sensitive to the anti-folate methotrexate in vivo than control tumors. Together, our data provide evidence to reevaluate the utility of these drugs in patients with p16/CDKN2A-low tumors as loss of p16/CDKN2A may provide a therapeutic window for these agents.

cancer biology↗