Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

A CRISPR-KO whole genome screen identifies factors and pathways that influence the tumour suppressive activity of androgen receptor agonist DHT in estrogen receptor positive breast cancer (#201)

Alex Pace 1 , Carmela Ricciardelli 1 2 , Wayne Tilley 1 , Theresa Hickey 1 , Amy Dwyer 1
  1. Dame Roma Mitchell Cancer Research Laboratories, University of Adelaide, Adelaide, Sa, Australia
  2. The Reproductive Cancer Group, University of Adelaide, Adelaide, SA, Australia

 

We have demonstrated that androgen receptor (AR) agonists durably suppress ER+ breast cancer growth in pre-clinical models [1] and have demonstrated efficacy of an AR agonist for treatment of advanced ER+ breast cancer [2]. Herein, we aimed to identify candidate factors and pathways that influence the tumour suppressive function of AR agonists inn ER+ breast cancer with view to finding novel combination treatment strategies or biomarkers of response.

An unbiased whole-genome CRISPR-CAS9 knockout (KO) screen using the Brunello library [3] was performed in T-47D ER+ AR+ breast cancer cells to identify genes that enhanced or antagonised inhibition of growth following treatment with an endogenous AR agonist, 5α–dihydrotestosterone (DHT, n = 4 biological replicates). The CRISPR-KO screen identified 26 significant sgRNA depletions (KO enhanced DHT-mediated growth suppression; e.g., TFAP2C, SREBF1) and 13 enrichments (KO reduced DHT-mediated growth suppression; e.g., CDK13, RARA). Network analysis using the METASCAPE platform [4] identified pathways necessary for AR activity (e.g. regulation of transcriptional elongation by CDK12/13) or that enhanced AR activity (e.g. lipid metabolism). To date, we found that treatment with a selective CDK12/13 inhibitor (SR-4835) mitigated the anti-proliferative effect of DHT in two ER+AR+ breast cancer cell lines (T-47D, ZR-75-1), validating one of the screen results. In accordance with these findings, loss of CDK12/13 or cofactor cyclin-K, was associated with AR antagonist resistance in prostate cancer [5]. Hence, deficiency in CDK12/13 signalling may be a biomarker of poor response to AR agonist drugs in ER+ breast cancers.

In summary, this project identified multiple candidate factors that are necessary for optimal AR tumour suppression or may enhance this activity in ER+ breast cancers. Further validation of CDK13 and other candidates is underway to characterise the effect of these factors on AR-mediated tumour suppression in this disease.  

  1. Hickey, T.E., et al., The androgen receptor is a tumor suppressor in estrogen receptor–positive breast cancer. Nature Medicine, 2021. 27(2): p. 310-320.
  2. Palmieri, C., et al., Activity and safety of enobosarm, a novel, oral, selective androgen receptor modulator, in androgen receptor-positive, oestrogen receptor-positive, and HER2-negative advanced breast cancer (Study G200802): a randomised, open-label, multicentre, multinational, parallel design, phase 2 trial. The Lancet Oncology, 2024. 25(3): p. 317-325.
  3. Sanson, K.R., et al., Optimized libraries for CRISPR-Cas9 genetic screens with multiple modalities. Nature Communications, 2018. 9(1): p. 5416.
  4. Zhou, Y., et al., Metascape provides a biologist-oriented resource for the analysis of systems-level datasets. Nature Communications, 2019. 10(1): p. 1523.
  5. Sun, R., et al., CYCLIN K down-regulation induces androgen receptor gene intronic polyadenylation, variant expression and PARP inhibitor vulnerability in castration-resistant prostate cancer. Proc Natl Acad Sci U S A, 2022. 119(39): p. e2205509119.