Juan Fernández-García

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.

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

Patients with colorectal cancer (CRC) frequently develop liver metastases^1-3. The prognosis of these patients is skewed by the histopathological heterogeneity of their liver metastases^4,5. Patients with 'replacement' metastases have a 5-year overall survival of less than 44.2%, compared with 73.4% in patients with 'encapsulated' (previously known as desmoplastic) metastases⁵; yet there are currently no approved therapies targeting replacement liver metastases. Here we show that treatment-naive patients with CRC with liver steatosis have an increased occurrence of replacement metastases compared with patients without steatosis. Mechanistically, we find that steatosis-promoted fatty acid oxidation increases formation of replacement metastases by increasing MYC stability through acetylation. In turn, MYC activates proline synthesis, fuelling collagen production, enabling growth of replacement metastases. Targeting MYC, P5CS or COL1A1 suppresses the occurrence and growth of replacement metastases in patient-derived organoids, mouse or patient-derived xenograft models. Spatial metabolite and protein analyses of liver metastases from patients with CRC further support this mechanism. In conclusion, we provide a mechanistic understanding of the emergence of liver metastases with poor prognosis in treatment-naive patients with CRC, identifying potential targets for therapeutic intervention.

Lipid accumulation in the tumor microenvironment is a hallmark of solid tumors, with increased palmitate (PA) availability fostering tumor progression. Although PA’s direct effects on cancer cells are well described, its impact on CD8 T cells [cytotoxic T lymphocytes (CTLs)] remains unclear. Here, we show that PA irreversibly impairs CTL mitochondrial metabolism, leading to the loss of effector functions and compromised antitumor immunity. PA-induced mitochondrial dysfunction reduced histone acetylation and chromatin accessibility, suppressing transcription of genes involved in T cell replication and effector programs. We identified sphingosine kinase 2 (SPHK2) as a key mediator of PA-induced dysfunction, with pharmacological inhibition of SPHK2 restoring mitochondrial fitness, rescuing CTL effector function, and promoting antitumor activity. These findings uncover a distinct mechanism by which PA drives immune evasion in tumors and highlight SPHK2 as a potential therapeutic target to enhance T cell–based immunotherapies.

Acetylation is frequently dysregulated in cancer, and both acetyltransferase and deacetylase inhibitors are being evaluated at various stages of preclinical and clinical development. However, how the expression of acetyltransferases and deacetylases is regulated remains often elusive. We focused on the lysine acetyltransferase 2A (KAT2A) as it is important in multiple cancer indications with a clinical inhibitor in development. We discovered that KAT2A expression is regulated by palmitoylation in breast cancer-derived metastases. Specifically, we find that the palmitoyltransferase DHHC20 (gene name ZDHHC20) palmitoylates transmembrane 4L six family member 1 (TM4SF1) promoting its plasma membrane localization. This in turn fosters phosphorylation of the signal transducer and activator of transcription 3 (STAT3), which we identify as a transcriptional regulator of KAT2A. Accordingly, Zdhhc20 and Tm4sf1 silencing as well as expression of a Tm4sf1 double palmitoylation mutant decreases lung metastasis growth, which is rescued by Kat2a expression. We detect evidence of this palmitoylation-induced regulation of KAT2A in lung metastasis samples from patients with breast cancer. Thus, we show that palmitoylation can orchestrate the expression of a global acetylation regulator in lung metastases.

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.