The Role of Receptor Activity Modifying Protein 1 in Prostate Cancer

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.