Chromosomal instability (CIN) and epigenetic alterations have been implicated in tumor progression and metastasis; yet how these two hallmarks of cancer are related remains poorly understood. By integrating genetic, epigenetic, and functional analyses at the single cell level, we show that progression of uveal melanoma (UM), the most common intraocular primary cancer in adults, is driven by loss of Polycomb Repressive Complex 1 (PRC1) in a subpopulation of tumor cells. This leads to transcriptional de-repression of PRC1-target genes and mitotic chromosome segregation errors. Ensuing CIN leads to the formation of rupture-prone micronuclei, exposing genomic double-stranded DNA (dsDNA) to the cytosol. This provokes tumor cell-intrinsic inflammatory signaling, mediated by aberrant activation of the cGAS-STING pathway. PRC1 inhibition promotes nuclear enlargement, induces a transcriptional response that is associated with significantly worse patient survival and clinical outcomes, and enhances migration that is rescued upon pharmacologic inhibition of CIN or STING. Thus, deregulation of PRC1 can promote tumor progression by inducing CIN and represents an opportunity for early therapeutic intervention.

The systemic metabolic shifts that occur during aging and the local metabolic alterations of a tumor, its stroma and their communication cooperate to establish a unique tumor microenvironment (TME) fostering cancer progression. Here, we show that methylmalonic acid (MMA), an aging-increased oncometabolite also produced by aggressive cancer cells, activates fibroblasts in the TME, which reciprocally secrete IL-6 loaded extracellular vesicles (EVs) that drive cancer progression, drug resistance and metastasis. The cancer-associated fibroblast (CAF)-released EV cargo is modified as a result of reactive oxygen species (ROS) generation and activation of the canonical and noncanonical TGFβ signaling pathways. EV-associated IL-6 functions as a stroma-tumor messenger, activating the JAK/STAT3 and TGFβ signaling pathways in tumor cells and promoting pro-aggressive behaviors. Our findings define the role of MMA in CAF activation to drive metastatic reprogramming, unveiling potential therapeutic avenues to target MMA at the nexus of aging, the tumor microenvironment and metastasis.

Lung adenocarcinoma (LUAD) and small cell lung cancer (SCLC) are thought to originate from different epithelial cell types in the lung. Intriguingly, LUAD can histologically transform into SCLC following treatment with targeted therapies. Here we designed models to follow the conversion of LUAD to SCLC and found the barrier to histological transformation converges on tolerance to Myc, which we implicate as a lineage-specific driver of the pulmonary neuroendocrine cell. Histological transformations are frequently accompanied by activation of the Akt pathway. Manipulating this pathway permitted tolerance to Myc as an oncogenic driver, producing rare, stem-like cells, transcriptionally resembling the pulmonary basal lineage. These findings suggest histological transformation may require the plasticity inherent to the basal stem cell, enabling tolerance to previously incompatible oncogenic driver programs.

Chromosomal instability (CIN) is a cancer hallmark associated with cancer metastasis and immune evasion. Yet, it is unclear how CIN modulates the tumor-microenvironment (TME). Here we show that CIN results in a protumor TME with enrichment of immune-suppressive macrophages, a granulocytic infiltrate, and exhausted T cells. Using ContactTracing, a newly developed computational tool to infer conditionally dependent cell-cell interactions from single cell RNA sequence data, we identify tumor ligands induced by the ER stress response in cancer cells as central mediators of immune suppression. Mechanistically, CIN-dependent chronic activation of the cytosolic DNA sensing cGAS-STING pathway promotes ER-stress-dependent transcription. Suppression of CIN or depletion of cancer cell STING reduces ER-stress and restores CIN-induced changes on the TME. Correspondingly, chronic STING activation in human breast cancer patients is associated with reduced tumor infiltrating lymphocytes and increased metastasis. Remarkably, pharmacologic inhibition of chronically active STING or depletion of downstream ER stress signaling suppresses metastasis in syngeneic models of melanoma, breast, and colorectal cancers, thereby demonstrating a viable therapeutic strategy for chromosomally unstable cancers. Citation Format: Jun Li, Melissa Hubisz, Ethan Earlie, Mercedes A. Duran, Emanuele Lettera, Su M. Phyu, Amit D. Amin, Matthew Deyell, Erina Kamiya, Karolina Budre, Julie-Ann Cavallo, Christopher Garris, Hannah Wen, Benjamin Izar, Eileen Parkes, Ashley Laughney, Samuel Bakhoum. Chromosomal instability shapes the tumor microenvironment through a chronic ER-stress response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3822.

The systemic metabolic shifts that occur during aging and the local metabolic alterations of a tumor, its stroma and their communication cooperate to establish a unique tumor microenvironment (TME) that fosters cancer progression. Here, we show that methylmalonic acid (MMA), an aging-increased oncometabolite that is also produced by aggressive cancer cells, activates fibroblasts in the TME, which reciprocally secrete IL-6 loaded extracellular vesicles (EVs) that drive cancer progression, drug resistance and metastasis. The cancer-associated fibroblast (CAF)-released EV cargo is modified as a result of reactive oxygen species (ROS) generation and activation of the canonical and noncanonical TGFβ signaling pathways in CAFs. EV-associated IL-6 functions as a stroma-tumor messenger that activates the JAK/STAT3 and TGFβ signaling pathways in tumor cells and promote an epithelial-to-mesenchymal transition (EMT) and drug resistance in vitro, and metastatic progression in vivo. Our findings reveal the role of MMA in the activation of CAFs to drive metastatic reprogramming, unveiling multiple potential therapeutic avenues to target MMA at the nexus of aging, the tumor microenvironment and metastasis.

Liver metastasis (LM) occurs frequently in patients with melanoma and is associated with a poor prognosis and reduced therapy response. To identify drivers of metastatic niches, we used a syngeneic mouse melanoma model which recapitulates genomic, metastatic and therapy response patterns seen in patients, and performed a large-scale in vivo CRISPR-Cas9 knockout screen, which identified perturbations that strongly promoted liver but not lung metastasis. The “top hit” in this screen associated with LM was loss Pip4k2c. Mechanistically, loss of Pip4k2c sensitized both mouse and human melanoma to insulin-mediated PI3K/AKT pathway activation. Interestingly, this observation was dependent on the allosteric but not kinase domain activity. Treatment with different PI3K inhibitors abrogated the pathway in vitro, but was partly bypassed in the presence of insulin. As expected, loss of Pip4k2c was associated with significant increase in LM but not lung-metastatic burden in both syngeneic and patient-derived xenograft models, and this phenotype was rescued by reconstitution of full-length, but not allosteric domain deficient Pip4k2c constructs. We reasoned that Pip4k2cKO cells preferentially colonized the liver by co-opting the insulin-rich milieu in this organ. To test this, we generated Pip4k2c-/-/InsrshIR-KD and showed that Insr was required but not sufficient to enhance LM burden. Surprisingly, treatment with PI3K inhibition in vivo resulted in increased and not decreased LM burden as we had expected. PET-CT imaging of animals treated with PI3K revealed increased glucose uptake in LM in the presence of PI3K inhibition. We therefore reasoned that paradoxical activation due to host-mediated increase in glucose and insulin in response to PI3K inhibitor, may results in increased homing and metastasis to the liver. In further in vivo experiments, we showed that breaking this loop with either SGLT2 inhibitor or ketogenic diet circumvented host responses and resulted in reduced LM burden, while having no effect on lung metastasis burden. To further substantiate these findings, we performed single cell RNA-seq of concurrent liver and lung metastasis bearing mice which revealed strong tumor-intrinsic enrichment of central carbon metabolism. Lastly, analysis of 243 human liver vs extra-hepatic metastases across 75 cancers and addition of newly generated RNA-seq data of additional melanoma LM, revealed concordant pathways enrichment of glycolysis and oxidative phosphorylation LM. Together, we identify an axis of liver-metastatic organotropism that can be abrogated with a combination of PI3K inhibition and SGLT2-inhibition or concurrent ketogenic diet. Citation Format: Meri Rogava, Tyler Joseph Aprati, Wei-Yu Chen, Johannes Melms, Clemens Hug, Amit Dipak Amin, Bryan Ngo, Michae l Lee, Patricia Ho, Yiping Wang, Stephen Tang, Ethan Earlie, Sean Chen, Thomas Tüting, Martin Röcken, Thomas K. Eigentler, Samuel F. Bakhoum, Andrei Molotkov, Akiva Mintz, Dirk Schadendorf, Lewis C. Cantley, Peter K. Sorger, Ashley Laughney, David Liu, Benjamin Izar. A genetic-metabolic circuit of liver-specific metastatic organotropism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3514.

The importance of metabolic reprogramming in cancer has been long demonstrated by the association of systemic metabolic changes, such as aging, diet and exercise, with cancer outcomes. These systemic shifts, combined with local metabolic alterations within the tumor microenvironment (TME), can all cooperate to foster an environment conducive to cancer progression. In cells derived from primary and metastatic patient tumors, we found that mesenchymal-like cells displayed dysregulated propionate metabolism, leading to increased accumulation and secretion of methylmalonic acid (MMA), a novel aging-induced oncometabolite. This tumor cell-secreted MMA, in addition to increased MMA in the serum of elderly individuals, combine to form high local accumulation of MMA in the TME. We discovered that MMA acts on fibroblasts in the TME, activating them to cancer-associated fibroblasts (CAFs). MMA modifies the cargo of CAF-secreted extracellular vesicles (EVs), which function as a messenger to tumor cells, further promoting epithelial-to-mesenchymal transition, drug resistance, and increased metastasis in vivo. Here, we reveal a novel function of MMA in cancer, demonstrating for the first time that tumor-secreted MMA recruits the tumor microenvironment to drive cancer progression and metastatic reprogramming. Citation Format: Vivien Low, Zhongchi Li, Ashley Laughney, Wenbing Jin, Noah Dephoure, Valbona Luga, Ethan Earlie, Bobak Parang, Chunjun Guo, Lewis Cantley, John Blenis. Methylmalonic acid in TME signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3175.