HNRNPD and lung carcinoma: To assess which AU-rich element binding proteins (AUBPs) could mediate regulation of PD-L1 expression downstream of RAS signaling, we performed a selected siRNA screen of likely candidate genes, AUF1, KSRP, HuR, and TTP (also known as tristetraprolin or ZFP36), in three RAS mutant lung cancer cell lines (Figures 3A–3C).