RPL21 and pachyonychia congenita: Several ribosomal protein (RPs) genes (RPL39, RPL21, etc.)were up-regulated in PC cells with long-term suppression of proto-oncogene KRAS. Due to the role of KRAS in the progression of PC, the upregulation of these RPs genes as the compensation of KRAS knockdown suggests that they are possibly critical for PC cells development and survival.