Department of Oncology and Metabolism, The University of Sheffield, Sheffield, South Yorkshire S10 2TN, UNITED KINGDOM.
Prostate cancer affects 1 in 8 men in the UK. Treatment options for advanced prostate cancer patients with hormone refractory and metastatic disease are limited and therefore investigations are required to identify novel therapeutic targets. Receptor activity modifying protein 1 (RAMP1) is a vital component for many different G protein-coupled receptors (GPCRs) from the calcitonin peptide family. It also has been linked with the clinical progression of prostate cancer and found to be an important driver of tumour growth in prostate cancer cell lines.
To further investigate the role of RAMP1 in prostate cancer, CRISPR/Cas9 was used to generate RAMP1 knockouts in a PC3 cell line. RAMP1 knockouts were validated using endpoint and quantitative PCR with Sanger sequencing. These RAMP1 knockouts were then tested in vitro and showed to have significant reductions in cell viability, invasion, adhesion and colony formation abilities. Increased levels of apoptosis were also found in RAMP1 knockouts. In vivo, deletion of RAMP1 resulted in almost complete inhibition of subcutaneous tumour growth. Immunohistochemistry staining revealed no differences in markers for Ki67 and CD31, respectively suggesting alternative causes for tumour growth inhibition. Treatment with human CGRP antagonists had no effect on tumour growth. These results may suggest that RAMP1 is acting in a CGRP-independent manner. Analysis of downstream signaling pathways in RAMP1 KO cells also revealed an association with Akt and STAT3.
These results show that RAMP1 may be vital for the survival of aggressive prostate cancer cells and that this protein plays an important role in the development of tumour growth. Although it remains unknown through which mechanism RAMP1 is promoting prostate cancer, the dysregulation of phosphorylated Akt and STAT3 implicates RAMP1 as an important instigator of oncogenic pathways associated with promoting hormone refractory and metastatic prostate cancer. Future investigations may focus on which GPCR RAMP1 is acting with to promote prostate cancer and whether this receptor protein can be targeted therapeutically to aid advanced prostate cancer patients.