This was also the case when lymphocytes were co-cultured with polarized HepG2-CD81 hepatoblastoma 3D spheroids, which form functional MRP2+ bile canaliculi (Mee et al., 2009), and with Huh-7 hepatocellular carcinoma cells, which form a monolayer in 2D culture. Here, CD81 is linked to hepatocellular carcinoma.