By integrating gene co-expression patterns and causal mediation analyses in the evaluation of transcriptional dysregulation by PRCA risk loci, we identified multiple plausible downstream effects mediated by PRCA risk genes MSMB and HNF1B. Our work provides the foundation for novel hypotheses for further investigation into the functional genetics of PRCA susceptibility and tumor progression. The gene discussed is HNF1B; the disease is neoplasm.