Abstract 981: A genetic-metabolic axis of metastatic liver organotropism
Authors: Rogava Meri , Melms Johannes C. , Davis Stephanie , Hug Clemens , Ngo Bryan , Lee Michael J. , Ho Patricia , Amin Amit Dipak , Wang Yiping , Chen Sean , Ge William , Liu David , Tüting Thomas , Röcken Martin , Eigentler Thomas K. , Bakhoum Samuel F. , Molotkov Andrei , Mintz Akiva , Cantley Lewis C. , Sorger Peter K. , Izar Benjamin 
Published: June 2022

Abstract
Genomic and adaptive determinants of organ-specific metastasis are poorly understood. A model of sequential acquisition of divergent somatic mutations is insufficient to explain metastasis. Liver metastasis (LM) occurs frequently and is associated with a poor prognosis and reduced therapy response in several cancers, including in patients with melanoma and lung cancer. To identify drivers of metastatic niches, we used a syngeneic mouse melanoma model which recapitulates genomic, metastatic and therapy response patterns seen in patients. We performed a large-scale in vivo CRISPR-Cas9 knockout screen and identified perturbations that promote LM, but not primary tumor growth or metastasis to other organs (e.g. lung). The “top hit” in this screen associated with LM was loss Pip4k2c. We generated Pip4k2cKO cells and show that in otherwise isogenic melanoma cell lines, loss of Pip4k2c led to increased baseline and insulin-induced activation of the PI3K/AKT pathway, and increased invasive capacity. Rescuing Pip4k2cKO with full-length (Pip4k2cRec) or allosteric domain deficient (Pip4k2cAD) Pip4k2c ORFs, we show that hyperactivation of the PI3K/AKT pathway in is mediated by loss of the allosteric domain function, and not loss of the kinase domain of Pip4k2c. Treatment with different PI3K inhibitors effectively abrogated the pathway, but was partly bypassed in the presence of insulin in Pip4k2cKO and Pip4k2cAD, but not parental or Pip4k2cRec cells. Upon tail vein injection, Pip4k2cKO cells produced a significantly increased LM burden compared to parental cells, and this effect was rescued in Pip4k2cRec but not Pip4k2cAD, further affirming that loss of allosteric domain was required for this phenotype. We reasoned that Pip4k2cKO cells preferentially colonized the liver by co-opting the insulin-rich milieu in this organ. To test this, we used shRNA targeted against the insulin receptor (Insr) generated Pip4k2cKO/InsrshIR and showed that Insr was required but not sufficient to enhance LM burden. Given the promising in vitro activity of PI3K inhibitors, we next tested whether these could abrogate LM in vivo. Surprisingly, we found a substantial increase in LM burden in mice with Pip4k2cKO-bearing LM treated with PI3K inhibition compared to vehicle treated animals. We show that this paradoxical observation was due to host-mediated increased in glucose and insulin in response to PI3K inhibitor, which promoted a forward loop of increased liver metastasis. Breaking this loop with either ketogenic diet or treatment with a SGLT2 inhibitor in turn rescued increased these host responses and resulted in reduced LM burden in combination with PI3K inhibition. In summary, we identify a novel mechanism of metastatic liver organotropism and pharmacological and dietary combinations to reduced liver metastatic burden. Given the expanding use of PI3K inhibitors, our findings may have important clinical implications.
Citation Format: Meri Rogava, Johannes C. Melms, Stephanie Davis, Clemens Hug, Bryan Ngo, Michael J. Lee, Patricia Ho, Amit Dipak Amin, Yiping Wang, Sean Chen, William Ge, David Liu, Thomas Tüting, Martin Röcken, Thomas K. Eigentler, Samuel F. Bakhoum, Andrei Molotkov, Akiva Mintz, Lewis C. Cantley, Peter K. Sorger, Benjamin Izar. A genetic-metabolic axis of metastatic liver organotropism [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 981.