Biology subjects

Croci, O.

Publications and source records attributed to Croci, O..

4 recordsLinked to original sources

bioRxiv2024

CDK12 controls transcription at damaged genes and prevents MYC-induced transcription-replication conflicts

Oncogene-induced replicative stress is a potent tumor-suppressive mechanism that must be kept in check for cancer cells to thrive. Thus, the identification of genes and pathways involved in replicative stress is key to understand cancer evolution and to identify prospective therapeutic targets. Here, we investigated factors that modulate replicative stress upon deregulation of the MYC oncogene. We identified the cyclin-dependent kinase CDK12 as selectively required to prevent transcription-replication conflicts and the activation of a cytotoxic DNA-damage response (DDR). At the mechanistic level, CDK12 was recruited to damaged genes by PARP-dependent DDR-signaling and elongation-competent RNAPII. Once recruited, CDK12 repressed transcription by preventing the association of CDK9 with RNAPII. Either loss or chemical inhibition of CDK12 led to DDR-resistant transcription at damaged genes. Genome-wide profiling revealed that loss of CDK12 exacerbated transcription-replication conflicts in MYC-overexpressing cells and led to the accumulation of double-strand DNA breaks (DSBs), occurring preferentially between early- replicating regions and transcribed genes, organized in a co-directional head-to-tail orientation. Overall, our data demonstrate that CDK12 protects genome integrity by repressing transcription of damaged genes, which is required for proper resolution of DSBs at oncogene-induced transcription-replication conflicts. This provides a rationale that explains both how CDK12 deficiency can promote tandem duplications of early-replicated regions during tumor evolution, and how CDK12 targeting can exacerbate replicative-stress in tumors.

cancer biology↗

bioRxiv2022

Oxidative stress potentiates the therapeutic action of a mitochondrial complex I inhibitor in MYC-driven B-cell lymphoma

MYC is a key oncogenic driver and an adverse prognostic factor in multiple types of cancer, including diffuse large B-cell lymphoma (DLBCL). Yet, MYC activation also endows cancer cells with a series of metabolic dependencies, which can provide strategic points for targeted pharmacological intervention. We recently reported that targeting the mitochondrial electron transport chain (ETC) complex I with the small molecule inhibitor IACS-010759 selectively killed MYC-overexpressing lymphoid cells. Here, we unravel the mechanistic basis for this synthetic-lethal interaction and exploit it to improve the anti-tumoral effects of ETC inhibition. In a mouse B-cell line, MYC hyperactivation and IACS-010759 treatment added up to induce oxidative stress, with consequent depletion of reduced glutathione and lethal disruption of redox homeostasis. This effect could be enhanced by targeted pharmacological intervention, with either inhibitors of NADPH production through the pentose phosphate pathway, or with ascorbate (vitamin C), known to contribute pro-oxidant effects when administered at high doses. In these conditions, ascorbate synergized with IACS-010759 to kill MYC-overexpressing cells in vitro and reinforced its therapeutic action against human B-cell lymphoma xenografts. Hence, ETC inhibition and high-dose ascorbate might improve the outcome of patients affected by high-grade lymphomas and other MYC-driven cancers. Key point #1MYC and the ETC complex I inhibitor IACS-010759 elicit different reactive oxygen species (ROS) that cooperate to disrupt redox homeostasis. Key point #2Further boosting of oxidative stress with high doses of ascorbate increases the killing of MYC-driven lymphoma xenografts by IACS-010759.

cancer biology↗

bioRxiv2021

GZMKhigh CD8+ T effector memory cells are associated with CD15high neutrophil abundance in early-stage colorectal tumors and predict poor clinical outcome.

Tumor contexture has emerged as a major prognostic determinant and tumor infiltrating CD8+ T cells have been associated with a better prognosis in several solid tumors, including early-stage colorectal cancer (CRC). However, the tumor immune infiltrate is highly heterogeneous and understanding how the interplay between different immune cell compartments impacts on the clinical outcome is still in its infancy. Here, we describe in a prospective cohort a novel CD8+ T effector memory population, which is characterized by high levels of Granzyme K (GZMKhigh CD8+ TEM) and is correlated with CD15high tumor infiltrating neutrophils. We provide both in vitro and in vivo evidence of the role of stromal cell-derived factor 1 (CXCL12/SDF-1) in driving functional changes on neutrophils at the tumor site, promoting their retention and increasing the crosstalk with CD8+ T cells. Mechanistically, as a consequence of the interaction with neutrophils, CD8+ T cells are skewed towards a CD8+ TEM phenotype and produce high levels of GZMK, which in turn decreases E-cadherin pathway. The correlations of GZMKhigh CD8+ TEM and neutrophils with both tumor progression in mice and early relapse in CRC patients demonstrate the role of GZMKhigh CD8+ TEM in promoting malignancy. Indeed, a gene signature defining GZMKhigh CD8+ TEM was associated with worse prognosis on a larger independent cohort of CRC patients and a similar analysis was extended to lung cancer (TCGA). Overall, our results highlight the emergence of GZMKhigh CD8+ TEM in early-stage CRC tumors as a hallmark driven by the interaction with neutrophils, which could implement current patient stratification and be targeted by novel therapeutics.

immunology↗

bioRxiv2019

MYC-associated factor MAX is an essential regulator of the clock core network

The circadian transcriptional network is based on a competition between transcriptional activator and repressor complexes regulating the rhythmic expression of clock-controlled genes. We show here that the MYC-Associated factor X, MAX, plays a repressive role in this network and operates through its MYC-independent binding to E-box-containing regulatory regions within the promoters of circadian BMAL1 targets. This clock function of MAX is essential for maintaining a proper circadian rhythm but separated by the role of MAX as a partner of MYC in controlling cell proliferation. We also identified MAX Network Transcriptional repressor, MNT, as a fundamental partner of MAX-mediated circadian regulation. Collectively, our data indicate that MAX is an integral part of the core molecular clock and keeps the balance between positive and negative elements of the molecular clock machinery. Accordingly, alteration of MAX transcriptional complexes may contribute to circadian dysfunction in pathological contexts.

molecular biology↗