Advanced pancreatic ductal adenocarcinoma - Complexities of treatment and emerging therapeutic options

Figure 2 Pathways involved in ribosome biogenesis. The first rate limiting step in ribosome biogenesis is the transcription of the rRNA genes by Pol I which forms a multiprotein transcription complex at the rDNA promotor[62]. Green arrows indicate up stream regulators which exert positive effects on the Pol I transcription complex including multiple pathways such as PI3K/AKT/mTOR, RAS/RAF/MEK and Myc which functions as the “master regulator” for cell growth[64]. The mature rRNAs together with ribosomal proteins assemble into the 40 and 60S ribosomal subunits, which then form the functional 80S ribosome[62]. Transcription of the rDNA repeat is negatively influenced by p53 (as shown by the red line) to ensure that cell growth/proliferation is tightly regulated.