UPF1 and nonpapillary renal cell carcinoma: However, the RNA immunoprecipitation assay by pull-down of TWIST1 mRNA using biotin-conjugated antisense oligonucleotide revealed that ectopic expression of wild-type TANAR could effectively diminish TWIST1 mRNA-UPF1 interaction in ccRCC, while their interaction was increased after knocking down TANAR (Fig. 6a–d).