DROSHA and neoplasm: Although loss of 22q13.31 may account for reduced expression of Let-7b in some tumours, it would not account for the effects observed with other Let-7 alleles, which are distributed over 8 loci and are more likely to be de-regulated in trans. Defects in miRNA processing machinery, including reduced levels of Dicer (DICER1) and Drosha (RNASEN), have been linked to poor outcome in HG-SOC [27], however, higher expression of DICER1 was observed in the C5 subtype (Figure S2).