Targeting gastrin releasing peptide receptor, somatostatin receptor 2 may improve care for breast cancer
In either primary or metastatic breast cancer, targeting the somatostatin receptor 2 and the gastrin releasing peptide receptor for nuclear imaging or treatment may improve care, a new study reports.
A total of 74 samples of primary breast cancer, which were fixed in formalin and embedded in paraffin, were retrospectively selected. Similarly, 77 corresponding metastases were also selected from a database. Six flash frozen samples of primary tumours and regional lymph nodes were also included.
Trained pathologists examined each sample to determine malignancy and the percentage of tumour cells. For inclusion, samples had to have enough tumour tissue, come with appropriate clinico-pathological data and have good quality RNA for the downstream RT-qPCR procedures.
After applying the criteria, 60 primary tumour-metastases pairs of samples remained. These were subjected to RT-qPCR to measure the expression of the somatostatin receptor 2 and gastrin releasing peptide receptor mRNA. Expressions were correlated with clinico-pathological factors and compared between primary tumours and metastases.
From the experiments, it was found that the radioligands of both somatostatin receptor 2 and gastrin releasing peptide receptor bound to the tumour tissue in a fashion correlated to their expression levels, as measured by their mRNA expression.
Interestingly, oestrogen receptor 1-positive tumours were found to be significantly correlated with elevated expression levels of the somatostatin receptor 2 and gastrin releasing peptide receptor mRNA (p<0.001 for both).
The expression of the gastrin releasing peptide receptor mRNA was not found to be significantly different between primary tumour samples and corresponding paired metastases samples.
For the most part, the expression levels of the somatostatin receptor 2 mRNA also showed no significant difference between the primary tumour samples and the paired metastases. However, metastases to the liver (p=0.02) and the ovary (p=0.03) showed significantly lower expressions of the somatostatin receptor 2 mRNA.
The findings showed that both the somatostatin receptor 2 and gastrin releasing peptide receptor, when targeted either for imaging or for treatment, may improve care of both primary and metastatic breast cancers.