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Microenvironmental autophagy promotes tumour growth.

Nature (2017-01-13)
Nadja S Katheder, Rojyar Khezri, Fergal O'Farrell, Sebastian W Schultz, Ashish Jain, Mohammed M Rahman, Kay O Schink, Theodossis A Theodossiou, Terje Johansen, Gábor Juhász, David Bilder, Andreas Brech, Harald Stenmark, Tor Erik Rusten
ABSTRACT

As malignant tumours develop, they interact intimately with their microenvironment and can activate autophagy, a catabolic process which provides nutrients during starvation. How tumours regulate autophagy in vivo and whether autophagy affects tumour growth is controversial. Here we demonstrate, using a well characterized Drosophila melanogaster malignant tumour model, that non-cell-autonomous autophagy is induced both in the tumour microenvironment and systemically in distant tissues. Tumour growth can be pharmacologically restrained using autophagy inhibitors, and early-stage tumour growth and invasion are genetically dependent on autophagy within the local tumour microenvironment. Induction of autophagy is mediated by Drosophila tumour necrosis factor and interleukin-6-like signalling from metabolically stressed tumour cells, whereas tumour growth depends on active amino acid transport. We show that dormant growth-impaired tumours from autophagy-deficient animals reactivate tumorous growth when transplanted into autophagy-proficient hosts. We conclude that transformed cells engage surrounding normal cells as active and essential microenvironmental contributors to early tumour growth through nutrient-generating autophagy.

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Trypsin-EDTA solution, 10 ×, sterile-filtered, BioReagent, suitable for cell culture, 5.0 g porcine trypsin and 2 g EDTA • 4Na per liter of 0.9% sodium chloride