TBX3 and breast cancer: Our data indicate that SIRT6-OE suppresses the expression of TBX3. To test whether direct TBX3 loss is sufficient to mimic SIRT6-OE, we induced siRNA-mediated knockdown of TBX3 in both BT474 (Fig. 8A–E) and BCM-4888 (Fig. S13) human breast cancer cells.