Gene Expression Analysis of Aggressive Adult Xp11.2 Translocation Renal Cell Carcinoma at Clinical Stage T1N0M0 to Identify Potential Prognostic and Therapeutic Biomarkers

Xp11.2 translocation renal cell carcinoma (tRCC), involving transcription factor E3 (TFE3) gene fusions, is a rare and aggressive RCC variant when present in adults and has been recently recognized as a unique entity in RCC. Biomarkers and treatment guidelines do not exist for patients with aggressive Xp11.2 tRCC. The aim was to identify and evaluate therapeutic biomarkers for aggressive Xp11.2 tRCC. RNA sequencing was performed using formalin-fixed, paraffin-embedded tissues from 11 adult patients with clinical T1N0M0 Xp11.2 tRCC, including three patients with aggressive characteristics (recurrence or cancer-specific death after nephrectomy). Thirty genes were differentially expressed between the aggressive and non-aggressive groups, even after adjustment, and were associated with KEGG pathways related to the aggressiveness of Xp11.2 tRCC. PIK3R2, involved in various KEGG pathways, including the PI3K/AKT/mTOR pathway, was overexpressed in the Xp11.2 tRCC cell lines UOK120 and UOK146. The PI3K pathway inhibitor LY294002 showed a significant therapeutic benefit. This study provides the first candidate biomarker, PIK3R2, for aggressive clinical T1N0M0 Xp11.2 tRCC. Furthermore, this study is the first to recommend a targeted drug, LY294002, for aggressive Xp11.2 tRCC based on the molecular pathophysiology.