The iron load of lipocalin-2 (LCN-2) defines its pro-tumour function in clear-cell renal cell carcinoma.

We aimed at clarifying the role of lipocalin-2 (LCN-2) in clear-cell renal cell carcinoma (ccRCC). Since LCN-2 was recently identified as a novel iron transporter, we explored its iron load as a decisive factor in conferring its biological function.

LCN-2 expression was analysed at the mRNA and protein level by using immunohistochemistry, RNAscope® and qRT-PCR in patients diagnosed with clear-cell renal cell carcinoma compared with adjacent healthy tissue. We measured LCN-2-bound iron by atomic absorption spectrometry from patient-derived samples and applied functional assays by using ccRCC cell lines, primary cells, and 3D tumour spheroids to verify the role of the LCN-2 iron load in tumour progression.

LCN-2 was associated with poor patient survival and LCN-2 mRNA clustered in high- and low-expressing ccRCC patients. LCN-2 protein was found overexpressed in tumour compared with adjacent healthy tissue, whereby LCN-2 was iron loaded. In vitro, the iron load determines the biological function of LCN-2. Iron-loaded LCN-2 showed pro-tumour functions, whereas iron-free LCN-2 produced adverse effects.

We provide new insights into the pro-tumour function of LCN-2. LCN-2 donates iron to cells to promote migration and matrix adhesion. Since the iron load of LCN-2 determines its pro-tumour characteristics, targeting either its iron load or its receptor interaction might represent new therapeutic options.

British journal of cancer. 2019 Nov 27 [Epub ahead of print]

Claudia Rehwald, Matthias Schnetz, Anja Urbschat, Christina Mertens, Julia K Meier, Rebekka Bauer, Patrick Baer, Sofia Winslow, Frederik C Roos, Klaus Zwicker, Arnaud Huard, Andreas Weigert, Bernhard Brüne, Michaela Jung

Institute of Biochemistry I, Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany., Institute for Biomedicine, Aarhus University, C. F. Møllers Allé 6, 8000, Aarhus, Denmark., Division of Nephrology, Department of Internal Medicine III, Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany., Clinic of Urology, Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany., Institute of Biochemistry I, Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany. .