Tumor growth assay

C57BL/6 J mice were obtained from the colony of the National Institute of Oncology, Budapest. Animal welfare and experimental procedures were performed in accordance with the related regulations of the ARRIVE guidelines [12] and with the animal welfare regulations of the host institute (permission number: 22.1/722/3/2010). For the tumor growth assay, subconfluent B16F0, B16F0-pcDNA4/TO, or B16F0-pcDNA4/TO-hPRL3 cells were harvested in PBS. 6 × 10⁵ cells was inoculated subcutaneously in a volume of 0.1 ml into the dorsal flanks of 8-week-old syngenic C57BL/6 J mice, as described previously [13]. Tumor size was measured three times a week with a caliper and expressed in mm³, using the formula for the volume of a prolate ellipsoid (length x width² x π/6), as described previously [14].