GHRH antagonist MIA-602 reduces tumor invasion marker MMP-2 in human papillary thyroid cancer cells
Background
Papillary thyroid cancer (PTC) is the most common endocrine cancer. While many cases are treatable, aggressive or refractory forms require new therapeutic approaches. Recent research has identified the presence of receptors for pituitary-type growth hormone-releasing hormone (pGHRH-R) in various human cancers, including prostate and brain cancers, suggesting this pathway could be a therapeutic target. However, the expression and role of pGHRH-R in thyroid malignancies had not been investigated. This study explored whether PTC cells express pGHRH-R and its splice variant, SV1, and if blocking this receptor system with a GHRH antagonist could inhibit cancer cell invasion and proliferation.
Study Design
The study utilized seven human cell lines, including both normal thyroid and papillary thyroid cancer (PTC) tumor cells, in an in vitro setting. These cells were treated with a GHRH antagonist, MIA-602, to assess its anti-proliferation and anti-invasion potential. A control group of cells was treated with a vehicle solution for comparison. The primary endpoints were the expression levels of pGHRH-R and SV1, the activity of the tumor invasion marker matrix metalloproteinase-2 (MMP-2), and overall cell proliferation rates. The effects were compared between treated tumor cells and vehicle-treated tumor cells, as well as between treated normal cells and vehicle-treated normal cells.
Results
Both normal thyroid cells and papillary thyroid cancer (PTC) cells express the pituitary-type GHRH receptor (pGHRH-R) and its splice variant (SV1). Treatment with the GHRH antagonist MIA-602 significantly increased the expression of pGHRH-R and SV1 in tumor cells compared to vehicle-treated tumor cells, which the authors suggest may alter intracellular signaling sensitivity. Importantly, MIA-602 treatment did not affect cell proliferation rates in either normal or cancerous thyroid cells. The key finding was the impact on a marker of tumor invasion:
GHRH antagonist treatment of tumor cells also reduced activity of the tumor invasion marker, matrix metalloproteinase (MMP)-2, compared to tumor cells exposed to vehicle only. Crucially, the expression of
pGHRH-RandSV1, as well asMMP-2activity, remained completely unaffected in normal thyroid cells following treatment with the GHRH antagonist.
Key Findings
- Pituitary-type GHRH receptors (pGHRH-R) and their splice variant (SV1) are expressed in both normal and papillary thyroid cancer (PTC) cells.
- The GHRH antagonist MIA-602 reduced the activity of matrix metalloproteinase-2 (MMP-2), a tumor invasion marker, in PTC cells.
- MIA-602 treatment did not affect MMP-2 activity or pGHRH-R/SV1 expression in normal thyroid cells.
- The GHRH antagonist did not alter cell proliferation rates in either normal or cancerous thyroid cells.
- Treatment with MIA-602 increased the expression of pGHRH-R and SV1 in tumor cells, but not in normal cells.
Why It Matters
These findings suggest a potential therapeutic role for GHRH antagonists in managing aggressive forms of papillary thyroid cancer, particularly those resistant to conventional treatments. The key implication is the selectivity of the antagonist's effect: it reduces a key marker of tumor invasion (MMP-2) in cancer cells while leaving normal thyroid tissue unharmed. This selective action could translate into a therapy with a favorable side-effect profile, targeting cancer progression without damaging healthy thyroid function. The study provides a rationale for further investigation into GHRH antagonists as a targeted therapy for PTC. While this is an early in vitro study, it establishes a clear mechanism of action that could be explored in preclinical animal models and eventually human trials for refractory thyroid cancer.
ghrh
cancer
thyroid cancer
oncology
in vitro
cell study
