P53 inactivation drives breast cancer brain metastasis via cell-autonomous and astrocyte-dependent increase of fatty acid metabolism

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Kathrin Laue1,*, Sabina Pozzi2*, Johanna Zerbib1, Rebecca Bertolio3, Yonatan Eliezer1, Yael Cohen-Sharir1, Tom Winkler1,  Manuel Caputo3, Alessia A. Ricci4, Lital Adler5,  Rami Khoury2, Giuseppe Longobardi2, Rachel Slutsky1, Alicia I. Leikin-Frenkel6,7, Shai Ovadia8,9, Katharina Lange1, Alessandra Rustighi3,10, Silvano Piazza3, Andrea Sacconi11, Rayna Y. Magesh12, Faith N. Keller12, Jean Berthelet13,14, Alexander Schäffer15, Ron Saad1, Sahar Israeli Dangoor2, Karolina Szczepanowska16, Iris Barshack6,17, Yang Liao13,  Sergey Malitsky18, Alexander Brandis18, Thomas Broggini19,20, Marcus Czabanka19,20, Wei Shi13,  Delphine Merino13,14,21,22, Emma V. Watson12, Giovanni Blandino11, Ayelet Erez5, Ruth Ashery-Padan8, Hind Medyouf15,23,, Luca Bertero4, Giannino Del Sal3,10,24, Ronit Satchi-Fainaro2,25# and Uri Ben-David1,#
 

1 Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel.  2 Department of Physiology and Pharmacology, Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel. 3 International Centre for Genetic Engineering and Biotechnology (ICGEB), Area Science Park-Padriciano, 34149 Trieste, Italy. 4 Pathology Unit, Department of Medical Sciences, University of Turin, Turin, Italy. 5 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel. 6 Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel. 7 The Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Ramat-Gan, Israel. 8 Department of Human Molecular Genetics and Biochemistry, Faculty of Medical & Health Sciences and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel. 9 European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany. 10 Department of Life Sciences, University of Trieste, 34127 Trieste, Italy.  11 Translational Oncology Research Unit, Regina Elena National Cancer Institute, Rome, Italy. 12 Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA, USA. 13 Olivia Newton-John Cancer Research Institute, Melbourne, Australia. 14 School of Cancer Medicine, La Trobe University, Melbourne, Australia. 15 Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, Frankfurt am Main, Germany. 16 IMol Polish Academy of Sciences, 02-247 Warsaw, Poland. 17 Institute of Pathology, Sheba Medical Center, Tel HaShomer, Ramat Gan, Israel. 18 Life Science Core Facility, Weizmann Institute of Science, Rehovot, Israel. 19 Department of Neurosurgery, University Hospital Frankfurt, Goethe University Frankfurt, 60528 Frankfurt am Main, Germany. 20 Frankfurt Cancer Institute, Goethe University, Frankfurt am Main, Germany. 21 Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia. 22 Department of Medical Biology, Faculty of Medicine, Dentistry, and Health Science, The University of Melbourne, Parkville, Australia. 23 University Hospital Aachen, RWTH, Aachen, Germany. 24 IFOM ETS, The AIRC Institute of Molecular Oncology, Milan, Italy. 25 Sagol School of Neurosciences, Tel Aviv University, Tel Aviv 6997801, Israel.   * Equally-contributing first authors # Co-corresponding senior authors: ronitsf@tauex.tau.ac.il; ubendavid@tauex.tau.ac.il

 

Brain metastasis (BM) is a dire prognosis across cancer types. It is largely unknown why some tumors metastasize to the brain whereas others do not. We analyzed genomic and transcriptional data from clinical samples of breast cancer BM (BCBM) and found that nearly all of them carried p53-inactivating genetic alterations through mutations, copy-number loss, or both. Importantly, p53 pathway activity was already perturbed in primary tumors giving rise to BCBM, often by loss of the entire 17p chromosome-arm. Experimentally, p53 knockout was sufficient to drastically increase BCBM formation and growth in vivo, providing a causal link between p53 inactivation and brain tropism. Mechanistically, p53 inactivation upregulated SCD1 expression and increased fatty acid synthesis (FAS), which is known to be required for brain-metastasizing cancer cells. Knockout of SCD1 was sufficient to abolish the growth advantage of p53-deficient cells in the brain. Molecularly, p53 suppressed SCD1 expression by binding to its promoter, and by downregulating its novel co-activator DEPDC1. FAS was further enhanced by astrocytes in a p53-dependent manner, as expression of FAS genes, including SCD1, was elevated upon exposure of BC cells to astrocyte-conditioned medium. Moreover, metabolomic analyses revealed that astrocytes secreted FAS substrates that were more efficiently metabolized into monounsaturated fatty acids (MUFAs) by SCD1 in p53-deficient BC cells. Consequently, astrocytes enhanced the survival, proliferation and migration of BC cells in a p53-dependent manner. Lastly, p53-deficient cells were more sensitive than p53-competent cells to FAS inhibitors in vitro, in vivo, and ex vivo, and patient-derived BCBM organotypic cultures were responsive to SCD1 inhibition. In summary, our study identifies p53 inactivation as a driver of BCBM; reveals a p53-dependent effect of astrocytes on BC behavior; and highlights FAS as an underlying, therapeutically-targetable molecular mechanism.