Recurrent DICER1 hotspot mutations in endometrial tumours and their impact on microRNA biogenesis

Abstract

DICER1 plays a critical role in microRNA (miRNA) biogenesis. Recurrent somatic 'hotspot' mutations at the four metal-binding sites within the RNase IIIb domain of DICER1 were identified in ovarian sex cord-stromal tumours and have since been described in other paediatric tumours. In this study, we screened the RNase IIIb domain of DICER1 in 290 endometrial tumours and identified six cases with hotspot mutations, including two cases affected by an atypical G1809R mutation directly adjacent to a metal-binding site. Using Illumina and Sanger targeted resequencing, we observed and validated biallelic DICER1 mutations in several cases with hotspot mutations. Through in vitro DICER1 cleavage assays, small RNA deep sequencing and real-time PCR, we demonstrated that mutations adding a positively charged side chain to residue 1809 have similar detrimental effects on 5p miRNA production to mutations at the metal-binding sites. As expected, 5p miRNAs were globally reduced in tumours and cell lines with hotspot mutations. Pathway analysis of gene expression profiles indicated that genes de-repressed due to loss of 5p miRNAs are strongly associated with pathways regulating the cell cycle. Using a Dicer1-null mouse cell line model, we found that expression of DICER1 hotspot mutants promoted cell proliferation, whereas wild-type (WT) DICER1 inhibited cell proliferation. Furthermore, targets of let-7 family miRNAs are enriched among the up-regulated genes, suggesting that loss of let-7 may be impacting downstream pathways. Our results reveal that DICER1 hotspot mutations are implicated in common malignancies and may constitute a unique oncogenic pathway.

DICER1-related Sertoli-Leydig cell tumor and gynandroblastoma: Clinical and genetic findings from the International Ovarian and Testicular Stromal Tumor Registry

“…The combination of these factors may be responsible for a stronger association between SLCT and DICER1 than was noted in previous reports. 11,15,34–36 None of the individuals with a centrally reviewed diagnosis of JGCT, steroid cell tumor, sex cord-stromal tumor with annual tubules or Sertoli cell tumor had germline DICER1 mutations, although one individual with a germline DICER1 mutation developed undifferentiated ovarian sarcoma and later SLCT. 37 …”

Endometrial adenosarcoma in the setting of a germline DICER1 mutation: A case report

“…Interestingly, the pathology of uterine adenosarcoma shares similarities with PPB and Wilms tumor which are both commonly associated with germline DICER1 mutations. All three tumors demonstrate sarcomatous cells associated with an epithelial component (Chen et al, 2015, Priest et al, 2006). Therefore, it is not surprising that this tumor is associated with a similar genetic predisposition.…”

“…The DICER1 gene product is an endoribonuclease responsible for processing microRNA (miRNA) (Chen et al, 2015). The majority of human genes are regulated by miRNAs.…”

“…The majority of human genes are regulated by miRNAs. Given the key role of miRNA in gene expression, DICER1 is thought to play a large role in tumorigenesis and is oftentimes referred to as a tumor suppressor gene (Chen et al, 2015). …”

“…Chen et al recently demonstrated an association between somatic DICER1 mutations and endometrial carcinomas and carcinosarcomas (Chen et al, 2015). Similarly, Conlon et al found that 2.4% of The Cancer Genome Atlas endometrial carcinoma genomes harbored DICER1 hotspot mutations (Conlon et al, 2016).…”