Papillary renal cell carcinoma (pRCC) represents the second most common kidney cancer and can be distinguished from other types based upon its unique histologic architecture and specific pattern of genomic alterations. Sporadic Type1 pRCC is almost universally driven by focal or chromosomal amplification of the receptor tyrosine kinase MET, though the specific mode of its activation is unclear. While the MET receptors found in human tumor specimens appear highly active, those found on the surface of in vitro cultured tumor cells are only weakly activated in the absence of exogenous hepatocyte growth factor (HGF) ligand. Furthermore, pRCC cells cultured in standard two-dimensional conditions with serum fail to respond functionally to MET knockdown or the selective MET inhibitor capmatinib despite clear evidence of kinase inhibition at the molecular level. To better model pRCC in vitro, we developed a three-dimensional (3D) coculture system in which renal tumor cells are layered on top of primary fibroblasts in a fashion that mimics the papillary architecture of human tumors. In this 3D spheroid model, the tumor cells survive and proliferate in the absence of serum due to trophic support of HGF-producing fibroblasts. Unlike tumor cells grown in monoculture, the proliferation of cocultured tumor cells is sensitive to capmatinib and parallels inhibition of MET kinase activity. These findings demonstrate the importance of stromal fibroblasts in pRCC and indicate that accurate in vitro representation of this disease requires the presence of both tumor and fibroblast cells in a structured coculture model.
American journal of physiology. Renal physiology. 2021 May 24 [Epub ahead of print]
Kylee A Rosette, Stephen M Lander, Calvin VanOpstall, Brendan David Looyenga
Department of Chemistry & Biochemistry, grid.253573.5Calvin University, Grand Rapids, MI 49546 USA.