TFE3 fusions drive expression of CD44 and SPP1 in Translocation Renal Cell Carcinoma

Xp11.2 translocation RCC [Xp11.2 tRCC]) is an underdiagnosed and aggressive subtype of RCC with few specific or targeted therapies. The transmembrane glycoprotein CD44 is an emerging target in many advanced malignancies, and with its ligand OPN ( SPP1 ), is a crucial driver of cancer progression, stemness, metastasis, and immune suppression. Here we show that common TFE3 -fusions [including SFPQ-TFE3, PRCC-TFE3, ASPSCR1-TFE3 , and NONO-TFE3 ] are associated with upregulated expression of CD44 and SPP1, as observed in multiple human and murine bulk transcriptomic studies and a murine tRCC snRNA-Seq dataset. CD44 and/or SPP1 protein expression were also upregulated in murine models of transgenic tRCC kidneys and urine specimens, patient-derived cell lines and human tRCC cases, by immunoblotting and/or IHC. Transient deletion of CD44 was associated with profound and specific suppression of tRCC cell line growth, with decreased mTOR signaling. These data suggest that CD44 and/or SPP1 may potentially drive tumorigenesis in tRCC.