Flash Talk and Poster Presentation 36th Lorne Cancer Conference 2024

Dual proteomic and transcriptomic screening reveals PCSK9 as a novel co-target in metastatic pancreatic ductal adenocarcinoma. (#205)

Shona Ritchie 1 2 , Katie Gordon 1 2 , Victoria Tyma 1 2 , Ying Fei Liew 1 2 , Cecilia Chambers 1 2 , Kendelle Murphy 1 2 , Julia Hartmann 1 2 , Astrid Magenau 1 2 , Anna Howell 1 2 , Alice Tran 1 2 , Julia Yin 1 2 , Sai Vara Prasad Chitti 3 , Australian Pancreatic Genome Initiative 1 2 , Australian Pancreatic Matrix Atlas 1 2 , Sue Clark 1 2 , Thomas Grewal 4 , Benjamin Parker 5 , Max Nobis 6 , Owen Sansom 7 8 , Jennifer P Morton 7 8 , Lisa Horvarth 1 2 9 , Suresh Mathivanin 3 , Ruth Pidsley 1 2 , David Herrmann 1 2 , Thomas Cox 1 2 , Marina Pajic 1 2 , Brooke Pereira 1 2 , Paul Timpson 1 2
  1. Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  2. St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
  3. Biochemistry and Genetics, La Trobe University, Melbourne, VIC, Australia
  4. Schools of Life and Environmental Sciences, the Charles Perkin Centre, the University of Sydney, Sydney, NSw, Australia
  5. School of Biomedical Sciences, University of Melbourne, Melbourne, VIC, Australia
  6. Intravital Imaging Expertise Center, VIB-KU Leuven Center for Cancer Biology, Leuven, Belgium
  7. Cancer Research UK Beatson Institute, Glasgow, Scotland, UK
  8. Wolfson Wohl Cancer Research Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, Scotland
  9. Chris O’Brien Lifehouse, Sydney, NSW, Australia

Pancreatic ductal adenocarcinoma cancer (PDAC) is a lethal malignancy with a 5-year survival rate of less than 11%[1]. It is characterised by a high metastatic burden and therapy resistance, highlighting the urgent need for innovative treatments. Using RNA sequencing and mass spectrometry proteomics, we robustly profiled the transcriptome, secretome and exosome proteomic profile of PDAC tumours from two GEMMs that closely recapitulate human disease. Through this integrated analysis, we have identified proprotein convertase subtilisin/kexin type 9 (PCSK9) is significantly overexpressed and secreted in PDAC tumours from the highly-metastatic KPC[2] vs. the poorly-metastatic KPflC[3] GEMM.

PCSK9, primarily known to have a role in cholesterol metabolism[4], has recently been described to have diverse functions in other cancers, affecting proliferation[5], apoptosis[6], immunoregulation[7, 8], and stromal cell biology[9]. Here, we show that PCSK9 is significantly upregulated by metastatic PDAC cells, confirmed by western blotting, ELISA, RT-qPCR, and IHC analyses of KPC tumours. Additionally, IHC analyses of PDAC patient tumour microarrays from the Australian Pancreatic Cancer Genome Initiative and International Cancer Genome Consortium (APGI/ICGC) cohorts revealed that high PCSK9 is significantly associated with poorer overall survival, prompting us to further explore PCSK9 as a clinically-relevant target. 

Using 3D organotypic matrix models, we show that targeting PCSK9 both i) genetically and ii) pharmacologically significantly impedes cancer cell invasion. Utilising PCSK9 inhibitors, including clinically-available evolocumab (Amgen®) and small molecule inhibitor PF-846 (Pfizer), we also show that targeting PCSK9 in this context significantly improved response to standard-of-care chemotherapy, gemcitabine/Abraxane (gem/Ab), evidenced by decreased ki67, increased cleaved-caspase 3 and increased yH2AX staining.

In subcutaneous PDAC models, both evolocumab and PF-846 in combination with gem/Ab significantly decreased tumour volume and increased survival compared to gem/Ab monotherapy. Strikingly, multiphoton microscopy of fluorescent ubiquitination-based cell cycle indicator (FUCCI) cell cycle reporter-expressing PDAC tumours demonstrated significant cell cycle stalling with PCSK9 inhibitors ± gem/Ab compared to gem/Ab monotherapy, indicating an enhanced chemotherapy response.

Overall, this work identifies PCSK9 as a novel ‘druggable’ target in PDAC and presents a potential opportunity to repurpose FDA/TGA-approved inhibitor evolocumab in PDAC. Ongoing work involves the assessment of PCSK9 inhibitors ± gem/Ab in clinically-relevant PDX models of PDAC.

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