Abstract PR001: Development and characterization of novel pre-clinical models of SFPQ-TFE3-driven renal cell carcinoma
Authors: de Aragao Mendes Adrianna Amaral , Liu Hans , Woo Juhyung , Asrani Kaushal , Rosenberg Avi , Argani Pedram , Lotan Tamara 
Published: August 2023

Abstract
Translocation Renal Cell Carcinomas (tRCC) are characterized by gene fusions that drive expression of chimeric TFE3 (Xp11.2) or TFEB (6p21.2). We developed and characterized a mouse model and inducible cell line expressing the SFPQ-TFE3 gene fusion to aid in biomarker and therapy development for this tumor type. We generated a murine knock-in model at the Rosa26 locus expressing the human SFPQ (exons 1-9) -TFE3 (exons 5-10) fusion gene downstream of a lox-stop-lox (LSL) sequence, under control of a chicken beta-actin promoter, on the C57BL/6 background. We crossed these LSL-SFPQ-TFE3 mice with the Cdh16-Cre model to induce SFPQ-TFE3 expression in renal epithelial cells. As an in vitro companion model, we generated HEK293 cells with stable doxycycline-inducible expression of the identical SFPQ-TFE3 fusion using the Flp-In T-RExTM system (SFPQ-TFE3-HEK293).Cdh16-Cre;LSL-SFPQ-TFE3 mice had reduced survival compared to the wild-type mice (p&lt;0.0001) and none survived past P19. At P1, Cdh16-Cre;LSL-SFPQ-TFE3 mice had scattered mild tubular dilation, with strong nuclear TFE3 protein expression in distal tubules and collecting ducts that was absent in controls. By P15, Cdh16-Cre;LSL-SFPQ-TFE3 kidneys were 30% larger than wild-type mice (p&lt;0.0001), with diffuse and strong nuclear expression of TFE3 throughout the majority of renal tubules. At this timepoint, Cdh16-Cre;LSL-SFPQ-TFE3 kidneys had prominent intratubular proliferation of renal epithelial cells, occasionally occluding the lumen, with diffuse psammomatous intraluminal calcification and mild patchy tubular dilatation. Glomerular morphology and size were not significantly different between the two groups at P15. However, the Cdh16-Cre;LSL-SFPQ-TFE3 mice had a lower density of glomeruli compared to the wild-type controls (5 glomeruli/mm² vs 50 glomeruli/mm²; p=0.03), potentially reflecting tubular expansion or aberrant glomerulogenesis. Wild-type and Cdh16-Cre;LSL-SFPQ-TFE3 mice exhibited similar tubular proliferative rate at P1 as assessed by Ki67. By P7, Cdh16-Cre;LSL-SFPQ-TFE3 mice showed significantly higher expression of Ki67 (p=0.03) but by P15, Ki67 index was lower (p=0.004) in the Cdh16-Cre;LSL-SFPQ-TFE3 mice compared to controls. Interestingly, by 48 hours after doxycycline induction, SFPQ-TFE3-HEK293 cells showed significantly decreased proliferation by MTT assay compared to the same cells without doxycycline treatment or to the parental Flp-In line treated with doxycycline (p=0.0002). A novel transgenic model for SFPQ-TFE3-driven tRCC shows early postnatal lethality, likely due to renal failure, precluding aging of these mice for tumor development. Though tubular proliferation is initially increased with SFPQ-TFE3 expression, Ki-67 expression is reduced by P15, paralleling the reduction in growth seen in inducible SFPQ-TFE3-HEK293 cells. These data suggest that SFPQ-TFE3 expression may paradoxically result in oncogene-induced senescence or cell cycle arrest in renal cells and further studies are underway to test this hypothesis.
Citation Format: Adrianna Amaral de Aragao Mendes, Hans Liu, Juhyung Woo, Kaushal Asrani, Avi Rosenberg, Pedram Argani, Tamara Lotan. Development and characterization of novel pre-clinical models of SFPQ-TFE3-driven renal cell carcinoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr PR001.