Supplementary Figure Legends and Tables list

Supplementary Figure Legends and Tables list

Metastatic disease remains a major cause of cancer-related mortality. Recent studies suggest that dissemination to other organs comes with metabolic changes that allow the metastasizing cancer cells to adapt to new microenvironments. A deeper knowledge of these specific metabolic features and associated vulnerabilities could lead to the development of more effective therapies against metastasis. We used in vivo and ex vivo models of MYC-driven breast tumorigenesis to explore the key metabolic pathways that change when mammary gland tumor cells metastasize to the lung. Stable isotope-resolved metabolomics, mass spectrometry imaging, and single-cell RNA sequencing demonstrated that mammary gland tumor-derived lung metastases have increased synthesis of glutathione fueled by increased cystine uptake. Metastatic cells relied heavily on the availability of extracellular cysteine or cystine, possibly due to downregulated intracellular cysteine synthesis through the transsulfuration pathway. When combined with focal radiotherapy, the amino acid degrader cyst(e)inase effectively reduced metastatic burden in the lungs. Together, these findings show that targeting cystine/cysteine exploits a metabolic dependency that is unique to metastatic cells and acts as a sensitizer to radiotherapy-induced oxidative stress, offering a promising targeted strategy.

Supplementary Figure 1 Surfactant lipids are enriched in the vicinity of lung metastases from patients with breast cancer; Supplementary Figure 2 AT2 cells and surfactant lipids co-localize in the vicinity of metastases from mice; Supplementary Figure 3 Metastases progression increases the enrichment of AT2 cells; Supplementary Figure 4 The metastasis secretome reprograms AT2 cell lipid metabolism by activating SREBP-1; Supplementary Figure 5 Gpam knockdown in cancer cells does not affect 3D spheroid growth in vitro; Supplementary Figure 6 GPAM and FASN inhibition in cancer cells does not affect metastasis formation in vitro and in vivo

Short hairpin RNAs (shRNAs) used to generate knockdown cell lines

Cancer cells that seed in the lung require lipids often produced by alveolar type II (AT2) cells. However, whether overt metastases depend on AT2 cell-derived lipids and whether AT2 cells can be targeted to reduce metastasis growth remains unknown. We discovered that breast cancer-derived lung metastases stimulate the proliferation of AT2 cells in their vicinity and reprogram them into lipid feeder cells in mice and patients using spatial analysis. Mechanistically, the metastasis secretome activates the transcription factor sterol regulatory element-binding transcription factor 1 (SREBP-1) in AT2 cells, enhancing the expression of key de novo lipid synthesis genes, including fatty acid synthase (FASN) and glycerol-3-phosphate acyltransferase 1 (GPAM). Deleting Fasn selectively in AT2 cells or targeting FASN and GPAM systemically significantly impairs lung metastasis growth in mice. In summary, we discovered that overt metastases reprogram AT2 cells and that targeting the lipid metabolism of AT2 cells impairs metastasis growth. SIGNIFICANCE:Current therapies in oncology targeting the cancer or immune cell compartment of tumors show limited efficacy against breast cancer-derived metastases. We discovered that decreasing the lipid metabolism of lung resident AT2 cells is sufficient to impair lung metastasis growth in mice without apparent adverse effects.

Summary: Understanding tumor heterogeneity is a major challenge that was recognized as one of the first Cancer Grand Challenges, with a call to provide solutions to visualize tumor heterogeneity. The Rosetta team took on this challenge, exploiting advances in spatial-omics approaches centered around mass spectrometry imaging to map tumor heterogeneity at the cellular and molecular scales with different levels of resolution. See related article by Bressan et al., p. 16 See related article by Stratton et al., p. 22 See related article by Bhattacharjee et al., p. 28

Cancer Research UK Rosetta Grand Challenge consortium list of members