SIX2 Effects on Wilms Tumor Biology

Area of Science:

• Nephrology
• Developmental Biology
• Cancer Biology

Background:

• Wilms tumor (WT) blastema shares gene expression with developing kidney cap mesenchyme (CM).
• SIX2 transcription factor is crucial for CM self-renewal and active in WT blastema, but its role in WT is unclear.
• WT blastema is considered the stem cell population of Wilms tumor.

Purpose of the Study:

• To investigate the functional significance of SIX2 in Wilms tumor (WT) biology.
• To test the hypothesis that SIX2 confers a survival pathway to WT blastema, the putative WT stem cell.
• To determine SIX2's effects on WT cell growth, signaling, and gene expression.

Main Methods:

• Overexpression of wild-type SIX2 in the human WT cell line (WiT49).
• Validation of the SIX2 overexpression model.
• Evaluation of SIX2 effects on anchorage-independent growth, proliferation, invasiveness, and canonical WNT pathway signaling.

Main Results:

• SIX2 overexpression significantly enhanced anchorage-independent growth and early-passage proliferation in WiT49 cells.
• SIX2 generally repressed TCF/LEF-dependent canonical WNT signaling.
• SIX2 significantly heightened canonical WNT signaling through the survivin promoter, maintaining stem state.

Conclusions:

• SIX2 overexpression enhances cell survival in a human WT cell line.
• SIX2 shifts WNT/β-catenin signaling balance away from differentiation and towards stem cell survival.
• SIX2 plays a critical role in maintaining the stem-like state of Wilms tumor blastema.