Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

IL-17-producing γδ T cells and neutrophils conspire to promote breast cancer metastasis

This article has been updated

Abstract

Metastatic disease remains the primary cause of death for patients with breast cancer. The different steps of the metastatic cascade rely on reciprocal interactions between cancer cells and their microenvironment. Within this local microenvironment and in distant organs, immune cells and their mediators are known to facilitate metastasis formation1,2. However, the precise contribution of tumour-induced systemic inflammation to metastasis and the mechanisms regulating systemic inflammation are poorly understood. Here we show that tumours maximize their chance of metastasizing by evoking a systemic inflammatory cascade in mouse models of spontaneous breast cancer metastasis. We mechanistically demonstrate that interleukin (IL)-1β elicits IL-17 expression from gamma delta (γδ) T cells, resulting in systemic, granulocyte colony-stimulating factor (G-CSF)-dependent expansion and polarization of neutrophils in mice bearing mammary tumours. Tumour-induced neutrophils acquire the ability to suppress cytotoxic T lymphocytes carrying the CD8 antigen, which limit the establishment of metastases. Neutralization of IL-17 or G-CSF and absence of γδ T cells prevents neutrophil accumulation and downregulates the T-cell-suppressive phenotype of neutrophils. Moreover, the absence of γδ T cells or neutrophils profoundly reduces pulmonary and lymph node metastases without influencing primary tumour progression. Our data indicate that targeting this novel cancer-cell-initiated domino effect within the immune system—the γδ T cell/IL-17/neutrophil axis—represents a new strategy to inhibit metastatic disease.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Neutrophils promote breast cancer metastasis.
Figure 2: Neutrophils suppress CD8+ T cell activation to facilitate metastasis.
Figure 3: Lymphocyte-derived IL-17 is required for G-CSF-induced neutrophil expansion and phenotype.
Figure 4: IL-1β-activated, IL-17-producing γδ T cells regulate neutrophil expansion, neutrophil phenotype and metastasis.

Accession codes

Primary accessions

Gene Expression Omnibus

Data deposits

RNA-seq data have been deposited in the Gene Expression Omnibus (GEO) under accession number GSE55633. Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests. Readers are welcome to comment on the online version of the paper. Correspondence and requests for materials should be addressed to K.E.dV. (k.d.visser@nki.nl).

Change history

  • 17 June 2015

    The mouse model name in Fig. 1a was corrected.

References

  1. 1

    Quail, D. F. & Joyce, J. A. Microenvironmental regulation of tumor progression and metastasis. Nature Med. 19, 1423–1437 (2013)

    CAS  Article  Google Scholar 

  2. 2

    McAllister, S. S. & Weinberg, R. A. The tumour-induced systemic environment as a critical regulator of cancer progression and metastasis. Nature Cell Biol. 16, 717–727 (2014)

    CAS  Article  Google Scholar 

  3. 3

    Noh, H., Eomm, M. & Han, A. Usefulness of pretreatment neutrophil to lymphocyte ratio in predicting disease-specific survival in breast cancer patients. J. Breast Cancer 16, 55–59 (2013)

    Article  Google Scholar 

  4. 4

    Azab, B. et al. Usefulness of the neutrophil-to-lymphocyte ratio in predicting short- and long-term mortality in breast cancer patients. Ann. Surg. Oncol. 19, 217–224 (2012)

    Article  Google Scholar 

  5. 5

    Granot, Z. et al. Tumor entrained neutrophils inhibit seeding in the premetastatic lung. Cancer Cell 20, 300–314 (2011)

    CAS  Article  Google Scholar 

  6. 6

    Kowanetz, M. et al. Granulocyte-colony stimulating factor promotes lung metastasis through mobilization of Ly6G+Ly6C+ granulocytes. Proc. Natl Acad. Sci. USA 107, 21248–21255 (2010)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Bald, T. et al. Ultraviolet-radiation-induced inflammation promotes angiotropism and metastasis in melanoma. Nature 507, 109–113 (2014)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Derksen, P. W. et al. Somatic inactivation of E-cadherin and p53 in mice leads to metastatic lobular mammary carcinoma through induction of anoikis resistance and angiogenesis. Cancer Cell 10, 437–449 (2006)

    CAS  Article  Google Scholar 

  9. 9

    Doornebal, C. W. et al. A preclinical mouse model of invasive lobular breast cancer metastasis. Cancer Res. 73, 353–363 (2013)

    CAS  Article  Google Scholar 

  10. 10

    Kaplan, R. N. et al. VEGFR1-positive haematopoietic bone marrow progenitors initiate the pre-metastatic niche. Nature 438, 820–827 (2005)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Erler, J. T. et al. Hypoxia-induced lysyl oxidase is a critical mediator of bone marrow cell recruitment to form the premetastatic niche. Cancer Cell 15, 35–44 (2009)

    CAS  Article  Google Scholar 

  12. 12

    Kuonen, F. et al. Inhibition of the Kit ligand/c-Kit axis attenuates metastasis in a mouse model mimicking local breast cancer relapse after radiotherapy. Clin. Cancer Res. 18, 4365–4374 (2012)

    CAS  Article  Google Scholar 

  13. 13

    Hiratsuka, S. et al. MMP9 induction by vascular endothelial growth factor receptor-1 is involved in lung-specific metastasis. Cancer Cell 2, 289–300 (2002)

    CAS  Article  Google Scholar 

  14. 14

    Hiratsuka, S., Watanabe, A., Aburatani, H. & Maru, Y. Tumour-mediated upregulation of chemoattractants and recruitment of myeloid cells predetermines lung metastasis. Nature Cell Biol. 8, 1369–1375 (2006)

    CAS  Article  Google Scholar 

  15. 15

    Pillay, J., Tak, T., Kamp, V. M. & Koenderman, L. Immune suppression by neutrophils and granulocytic myeloid-derived suppressor cells: similarities and differences. Cell. Mol. Life Sci. 70, 3813–3827 (2013)

    CAS  Article  Google Scholar 

  16. 16

    Mazzoni, A. et al. Myeloid suppressor lines inhibit T cell responses by an NO-dependent mechanism. J. Immunol. 168, 689–695 (2002)

    CAS  Article  Google Scholar 

  17. 17

    Young, M. R., Wright, M. A., Matthews, J. P., Malik, I. & Prechel, M. Suppression of T cell proliferation by tumor-induced granulocyte-macrophage progenitor cells producing transforming growth factor-β and nitric oxide. J. Immunol. 156, 1916–1922 (1996)

    CAS  PubMed  Google Scholar 

  18. 18

    Lejeune, P. et al. Nitric oxide involvement in tumor-induced immunosuppression. J. Immunol. 152, 5077–5083 (1994)

    CAS  PubMed  Google Scholar 

  19. 19

    Hamilton, J. A. & Achuthan, A. Colony stimulating factors and myeloid cell biology in health and disease. Trends Immunol. 34, 81–89 (2013)

    CAS  Article  Google Scholar 

  20. 20

    Chung, Y. et al. Critical regulation of early Th17 cell differentiation by interleukin-1 signaling. Immunity 30, 576–587 (2009)

    CAS  Article  Google Scholar 

  21. 21

    Cai, Y. et al. Pivotal role of dermal IL-17-producing γδ T cells in skin inflammation. Immunity 35, 596–610 (2011)

    CAS  Article  Google Scholar 

  22. 22

    Mei, J. et al. Cxcr2 and Cxcl5 regulate the IL-17/G-CSF axis and neutrophil homeostasis in mice. J. Clin. Invest. 122, 974–986 (2012)

    CAS  Article  Google Scholar 

  23. 23

    Sutton, C. E. et al. Interleukin-1 and IL-23 induce innate IL-17 production from gammadelta T cells, amplifying Th17 responses and autoimmunity. Immunity 31, 331–341 (2009)

    CAS  Article  Google Scholar 

  24. 24

    Schwarzenberger, P. et al. Requirement of endogenous stem cell factor and granulocyte-colony-stimulating factor for IL-17-mediated granulopoiesis. J. Immunol. 164, 4783–4789 (2000)

    CAS  Article  Google Scholar 

  25. 25

    Fridlender, Z. G. et al. Polarization of tumor-associated neutrophil phenotype by TGF-β: “N1” versus “N2” TAN. Cancer Cell 16, 183–194 (2009)

    CAS  Article  Google Scholar 

  26. 26

    Han, Y. et al. Prognostic value of chemotherapy-induced neutropenia in early-stage breast cancer. Breast Cancer Res. Treat. 131, 483–490 (2012)

    CAS  Article  Google Scholar 

  27. 27

    Ma, C. et al. Tumor-infiltrating γδ T lymphocytes predict clinical outcome in human breast cancer. J. Immunol. 189, 5029–5036 (2012)

    CAS  Article  Google Scholar 

  28. 28

    Novitskiy, S. V. et al. TGF-β receptor II loss promotes mammary carcinoma progression by Th17 dependent mechanisms. Cancer Discov 1, 430–441 (2011)

    CAS  Article  Google Scholar 

  29. 29

    Chen, W. C. et al. Interleukin-17-producing cell infiltration in the breast cancer tumour microenvironment is a poor prognostic factor. Histopathology 63, 225–233 (2013)

    Article  Google Scholar 

  30. 30

    Sutherland, T. E. et al. Chitinase-like proteins promote IL-17-mediated neutrophilia in a tradeoff between nematode killing and host damage. Nature Immunol. 15, 1116–1125 (2014)

    CAS  Article  Google Scholar 

  31. 31

    de Visser, K. E., Korets, L. V. & Coussens, L. M. De novo carcinogenesis promoted by chronic inflammation is B lymphocyte dependent. Cancer Cell 7, 411–423 (2005)

    CAS  Article  Google Scholar 

  32. 32

    Ciampricotti, M., Hau, C. S., Doornebal, C. W., Jonkers, J. & de Visser, K. E. Chemotherapy response of spontaneous mammary tumors is independent of the adaptive immune system. Nature Med. 18, 344–346 (2012)

    CAS  Article  Google Scholar 

  33. 33

    Girardi, M. et al. Regulation of cutaneous malignancy by γδ T cells. Science 294, 605–609 (2001)

    ADS  CAS  Article  Google Scholar 

  34. 34

    Ciampricotti, M. et al. Development of metastatic HER2+ breast cancer is independent of the adaptive immune system. J. Pathol. 224, 56–66 (2011)

    CAS  Article  Google Scholar 

Download references

Acknowledgements

This work was supported by a Marie Curie Intra-European Fellowship to S.B.C. (BMDCMET 275610); a European Research Council Consolidator award (INFLAMET 615300) to K.E.dV; grants from the Dutch Cancer Society to K.E.dV and J.J. (2011-5004); Worldwide Cancer Research (AICR 11-0677) to K.E.dV; the Netherlands Organization for Scientific Research NWO VIDI (917.96.307) to K.E.dV; and a Dutch Cancer Society/Bas Mulder Award to L.J.A.C.H. (UL2011-5051). We thank J. Borst, T. Schumacher and J. Coquet for discussions. We thank the core facilities at the Netherlands Cancer Institute. We thank L. Coussens for Rag1−/− mice and A. Hayday for Tcrd−/− mice. We thank C. Ries and K. Wartha for technical assistance.

Author information

Affiliations

Authors

Contributions

S.B.C., J.J. and K.E.dV. conceived the ideas and designed the experiments. S.B.C., C.W.D., K.K., J.W., C.H., K.V., N.J.V., M.C., L.J.A.C.H. and K.E.dV. performed the experiments. S.B.C., C.W.D., K.K., J.W., C.H., K.V., N.J.V., L.J.A.C.H. and K.E.dV. analysed the data. S.B.C., K.K. and K.E.dV. wrote the paper.

Corresponding author

Correspondence to Karin E. de Visser.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Systemic neutrophil expansion and accumulation in mammary tumour-bearing KEP mice and the metastasis model.

a, Representative images of neutrophils identified by the 7/4 antibody in lung sections in WT or KEP mice. Scale bar, 50 μm. b, Quantification of neutrophil accumulation per field of view (FOV) in various organs by immunohistochemistry using the 7/4 antibody (n = 6 WT, 9 KEP mice). c, Absolute neutrophil counts in blood of WT and tumour-bearing KEP mice (n = 4 WT, 8 KEP). d, Quantification of neutrophil accumulation in various organs determined by flow cytometry and gated on CD45+ cells. Neutrophils were not detectable in WT mammary glands (n = 5 WT, 7 KEP mice). e, Representative images of Ly6G-stained lung sections and quantification of neutrophil accumulation in the metastasis model. Data were generated from mock-transplanted, non-tumour-bearing mice (0 mm2), or tumour-transplanted recipient mice killed when tumours reached the tumour size shown or when mice exhibited signs of respiratory distress due to pulmonary metastasis. For quantification in lungs with metastases, neutrophils residing inside metastases were excluded. T, pulmonary metastatic lesion. Scale bar, 100 μm (n = 3, 5, 6, 6 and 3 mice for 0, 9, 25, 100 mm2 and metastasis respectively). f, Kinetics of neutrophil accumulation in various organs of the metastasis model by flow cytometry after gating on CD45+ cells. Recipient mice transplanted with KEP tumour pieces were killed at the tumour size shown (n = 6, 5, 6, and 7 mice for 0, 9, 25, 100 mm2 respectively). g, Kinetics of neutrophil proportions in blood (gated on CD45+ cells), before and after surgical removal of their primary tumour (n = 5). All data are mean + s.e.m. *P < 0.05, **P < 0.01, ***P < 0.001 as determined by Mann–Whitney U-test or Kruskal–Wallis test followed by post-hoc Dunn’s test.

Extended Data Figure 2 Neutrophil depletion does not affect primary tumour or metastatic nodule growth.

a, Schematic illustration of the neutrophil depletion experiment in the spontaneous metastasis model. b, Representative dot plots of neutrophils gated on CD45+ cells in blood of control and anti-Ly6G-treated recipient mice. The Gr1 antibody was used here to avoid false-negative results since the anti-Ly6G depleting antibody may mask the Ly6G epitope. CD11b+Gr1high cells were Ly6C+CCR2, indicating that these cells were neutrophils. CD11b+Gr1low cells that were Ly6C+ and CCR2+ represented the monocytic fraction. c, Quantification of neutrophil depletion in blood of control and anti-Ly6G-treated recipient mice at the tumour size indicated (n = 8 control, 5 anti-Ly6G; **P < 0.01 as determined by Mann–Whitney U-test). d, Primary tumour growth kinetics of mice treated as indicated (n = 12 control, 14 anti-Ly6G). e, Representative images of primary tumours in the metastasis model treated as shown and stained with haematoxylin and eosin, cytokeratin 8, vimentin, E-cadherin and CD34. Scale bar, 100 μm. f, Quantification of blood vessels per field of view (FOV) in control and neutrophil-depleted mice by anti-CD34 immunohistochemistry (n = 10). g, Quantification of pulmonary metastatic nodule size in control and neutrophil-depleted mice (n = 9 control, 11 early phase, 14 late phase mice). All data are mean + s.e.m.

Extended Data Figure 3 Subpopulations of neutrophils in mammary tumour-bearing mice are immature.

a, Gating strategy for identification of neutrophils (CD45+CD11b+Ly6G+Ly6C+F4/80 cells), cKIT+ neutrophils and monocytes (CD45+CD11b+Ly6GLy6C+F4/80 cells) by flow cytometry. Blood cells from WT and tumour-bearing KEP mice are shown here. b, Quantification of cKIT+ neutrophil accumulation in various organs determined by flow cytometry after gating on CD45+CD11b+Ly6G+Ly6C+F4/80 cells. cKIT+ neutrophils were not detectable in WT mammary glands (n = 5 WT, 7 KEP; Mann–Whitney U-test). c, cKIT+ neutrophil proportions in various organs of the metastasis model as determined by flow cytometry after gating on CD45+CD11b+Ly6G+Ly6C+F4/80 cells. Mice were killed at the tumour size shown (n = 5, 5, 5, and 8 mice for 0, 9, 25, 100 mm2 respectively; Kruskal–Wallis test followed by post-hoc Dunn’s test). d, Kinetics of cKIT+ neutrophil proportions in blood (gated on CD45+CD11b+Ly6G+Ly6C+F4/80 cells), before and after surgical removal of the primary tumour (n = 5 per group; Mann–Whitney U-test). e, Representative images and quantification of neutrophil nuclear morphology. Ly6G+ cells were isolated from blood of WT and tumour-bearing KEP mice then assessed by Giemsa stain. Hyper-segmented cells were considered mature, whereas all other cells were considered immature. Scale bar, 10 μm. (n = 6 WT, 5 KEP mice; Mann–Whitney U-test). All data are mean + s.e.m. *P < 0.05, **P < 0.01, ***P < 0.001.

Extended Data Figure 4 Neutrophils influence the function and phenotype of CD8+ T cells.

a, Unsupervised hierarchical clustering of RNA-Seq analysis depicting 100 differentially expressed genes between circulating neutrophils from WT and tumour-bearing KEP mice. P value (0.05) was used as cutoff (n = 4 WT, 5 KEP mice). See also Extended Data Table 1 for top 50 genes ranked by fold change. b, Circulating neutrophils from either WT or tumour-bearing KEP mice were incubated with CFSE-labelled splenic CD8+ T cells from WT mice and CD3/CD28 stimulation beads. The iNOS inhibitor, L-NMMA, was added where indicated. After 48 h, CD8+ T cell proliferation was measured by flow cytometry. c, Dot plots depicting live cell-gated CD8+ T cell proportions in lungs of mice in control and neutrophil-depleted mice, killed when transplanted tumours reached 100 mm2. d, Dot plots of effector CD8+ T cell (CD62LCD44+) proportions in lungs of transplanted mammary tumour-bearing mice that were killed when tumours reached 100 mm2. e, IFN-γ expression by CD8+ T cells in lungs of transplanted mammary tumour-bearing mice that were killed when tumours reached 100 mm2. f, Tumour growth kinetics in neutrophil-depleted or combined neutrophil- and CD8+ T-cell-depleted, mammary tumour-transplanted recipient mice, compared with control (n = 13 control, 21 anti-Ly6G, 14 anti-Ly6G/CD8). Data are mean + s.e.m.

Extended Data Figure 5 Cytokine expression levels in tumours and T cells, and their effects on neutrophils.

a, Unsupervised clustering of cytokine expression analysis in WT mammary glands and KEP tumours. Protein lysates were prepared as previously described from whole tissue34 and analysed for expression of various cytokines by Luminex-based assay (n = 5 per group). b, Protein levels of indicated cytokines in WT mammary glands and KEP tumours, determined by Luminex-based cytokine profiling; n.d., not detectable (n = 10 per group; Mann–Whitney U-test). c, d, Quantification of neutrophil and cKIT-expressing neutrophil accumulation in blood as determined by flow cytometry and gated on CD45+ cells. WT (n = 4) or tumour-bearing KEP mice (n = 9) were treated with anti-IL-17 (n = 8) and/or recombinant G-CSF (rG-CSF; n = 4) where indicated (Mann–Whitney U-test or Kruskal–Wallis test followed by post-hoc Dunn’s test). e, Gene expression in circulating neutrophils from WT control (n = 5), rG-CSF-treated WT mice (n = 4), KEP control (n = 10), anti-IL-17-treated (n = 6), anti-IL-17 + rG-CSF-treated KEP mice (n = 4; Mann–Whitney U-test or Kruskal–Wallis test followed by post-hoc Dunn’s test). f, Spleens of three WT mice and three KEP mice were pooled and CD3+ T cells were isolated. These cells were analysed by a real-time PCR array containing 86 different genes. Gene expression changes greater than threefold are shown. Members of the IL-17 signalling pathway are depicted in blue. *P < 0.05, **P < 0.01, ***P < 0.001. All data are mean + s.e.m.

Extended Data Figure 6 Absence of the adaptive immune system reduces metastasis.

a, Graphic representation of mammary tumour latency (left) and tumour growth (right) in lymphocyte-proficient KEP;Rag1+/− and lymphocyte-deficient KEP;Rag1−/− mice (n = 30 per group left panel, 10 mice per group right panel). b, Levels of TGF-β1 in mammary tumours and the plasma of tumour-bearing mice (n = 6 tumour, 3 plasma). c, Quantification of metastatic burden in lungs of recipient WT or Rag1−/− mice that were transplanted with KEP mammary tumour fragments and underwent surgical removal of the primary tumour (n = 6 WT, 4 Rag1−/− mice; **P < 0.01, Mann–Whitney U-test). Data are mean + s.e.m.

Extended Data Figure 7 Depletion of CD4+ T cells does not affect systemic cytokine levels or neutrophil expansion.

a, The proportion of IL-17A+ cells among CD4+ T cells in organs of WT and tumour-bearing KEP mice (n = 6 per group; Mann–Whitney U-test). b, Median fluorescence intensity of IL-17A expression in circulating γδ and CD4+ T cells from tumour-bearing KEP mice, as determined by flow cytometry (n = 11 per group; Wilcoxon matched-pairs test). c, Representative dot plots depicting total neutrophil and cKIT+ proportions in blood of control, anti-CD4- and anti-γδTCR-treated tumour-bearing KEP mice. d, Quantification of total neutrophil and cKIT+ neutrophil proportions in blood of control and anti-CD4-treated tumour-bearing KEP mice (n = 7 per group; Mann–Whitney U-test). e, Serum levels of IL-17A and G-CSF in control and anti-CD4-treated tumour-bearing KEP mice (n = 10 control, 6 anti-CD4; Mann–Whitney U-test). *P < 0.05, **P < 0.01. All data are mean + s.e.m.

Extended Data Figure 8 γδ T cell phenotype in KEP mice and their lack of influence on tumour growth in the metastasis model.

a, γδ T cells from lungs of tumour-bearing KEP mice were analysed by flow cytometry for IL-17, CD27, Vγ1 and Vγ4 expression. Two major populations of γδ T cells were observed including IL-17+CD27 and IL-17CD27+ cells. b, Representative histograms of CCR6, IL-1R1, IL-23R and ROR-γt expression in IL-17+CD27 and IL-17CD27+ γδ T cell populations shown in a. c, Il1β gene expression in various cell populations isolated from transplanted KEP tumours. Tumours from three mice were pooled to form one group. CD45 cells (which include cancer cells, endothelial cells and fibroblasts), CD45+CD11b+F4/80+ macrophages, CD45+CD11b+Ly6G+ neutrophils and CD45+CD11b lymphocytes were sorted from two pooled groups. Real-time PCR was performed on individual cell populations for Il1β expression. Relative expression among different cells is shown. d, Graphic representation of immune cell proportions in KEP tumours (n = 4). e, Primary tumour growth kinetics of control and γδ T cell-depleted tumour transplant recipient mice (n = 13 per group). f, Growth kinetics of primary tumours transplanted into Tcrd+/− (n = 10) and Tcrd−/− mice (n = 6). All data are mean + s.e.m.

Extended Data Figure 9 The γδ T cell/IL-17/neutrophil axis promotes breast cancer metastasis.

Mammary tumours evoke a systemic inflammatory cascade that is initiated by IL-1β production. Tumour-derived IL-1β activates γδ T cells to produce IL-17. Increased systemic IL-17 levels lead to upregulation of G-CSF, which subsequently causes neutrophil expansion and alteration of neutrophil phenotype. These phenotypically altered neutrophils produce iNOS that suppresses the activity of anti-tumour CD8+ T cells. As a result of this systemic inflammatory cascade, the chance that disseminated cancer cells can establish metastases in distant organs is maximized.

Extended Data Table 1 The top 50 most differentially expressed genes between neutrophils from WT and KEP mice

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Coffelt, S., Kersten, K., Doornebal, C. et al. IL-17-producing γδ T cells and neutrophils conspire to promote breast cancer metastasis. Nature 522, 345–348 (2015). https://doi.org/10.1038/nature14282

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing