ChRCC is characterized by dramatic chromosomal copy number (CN) changes. Currently, no model is available to precisely elucidate the molecular drivers of this rare tumor. HNF1B is a master regulator of gene expression, and both mutated HNF1B and downregulated HNF1B protein levels have previously been described in ChRCC.
We queried The Cancer Genome Atlas ChRCC database and analyzed tissue microarray data to determine the relative levels of HNF1B in ChRCC versus other RCC subtypes, and assessed the prognostic impact of dual HNF1B and TP53 loss. We knocked out Hnf1b in proliferating murine embryo fibroblasts (MEFs) and human ACHN cells and measured the effect on gene and protein expression of checkpoint regulatory proteins, spindle integrity, and aneuploidy. We then performed dual knockdown of HNF1B and TP53 and assessed cellular behavior.
We found that HNF1B transcript and HNF1B protein were downregulated in the majority of ChRCC in TCGA, and the magnitude of HNF1B loss is unique to ChRCC. Additionally, we observed a strong correlation between reduction of HNF1B expression and aneuploidy in ChRCC patients. In MEF cells deficient in Hnf1b, we observed the development of aneuploidy. Hnf1b deficiency also reduced spindle checkpoint protein (MAD2L1, BUB1B) and cell cycle checkpoint protein (RB1 and p27) expression, and altered chromatin access of Mad2l1, Bub1b and Rb1 genes. Coordinate loss of Bub1b and Rb1 recapitulated the polynuclearity and larger cell size seen with Hnf1b depletion. TCGA data also showed that TP53 is mutated in 33% of ChRCC whose HNF1B expression was repressed, and the combination of HNF1B loss with TP53 mutation was associated with poor prognosis. The combination of HNF1B loss with TP53 inactivation led to increased cell proliferation and increased aneuploidy, providing evidence that coordinate loss of HNF1B and TP53 may enhance cellular survival and engender an aggressive ChRCC tumor phenotype.
HNF1B deficiency is a major driver of chromosomal instability in ChRCC and lethality is associated with subsequent TP53 loss. Further development of model systems with combined HNF1B/TP53 loss will accelerate the development of treatments specific for ChRCC.
Clinical trial identification
Legal entity responsible for the study
UT MD Anderson Cancer Center
National Institutes of Health
All authors have declared no conflicts of interest.