NR2C2 and renal cell carcinoma: Among several likely candidates, including TR4-siRNAs [25, 26], miRNAs [22], TR4 potential antagonists/agonists including tretinoin (Hu et al. unpublished data), and metformin [27] that can suppress the TR4 function, we found that adding TR4-shRNA (See Fig. 1f, g), metformin or tretinoin (up to 10 μM), could also result in increasing the sunitinib sensitivity to better suppress the RCC OSRC-2 cell growth (Fig. 6a, b, Supplementary Fig. 2a, b).