GHRH Antagonist JMR-132 Suppresses Ovarian Cancer Cell Proliferation via EGFR-Akt Pathway
Background
Ovarian cancer remains a highly lethal gynecological malignancy, partly because key mitogenic pathways such as EGFR-Akt continue to drive unchecked tumor proliferation. Standard-of-care therapies often fail to adequately suppress these downstream survival signals, leaving a clinical gap for targeted peptide-based interventions. Growth hormone-releasing hormone (GHRH) and its receptors, particularly splice variants expressed in tumor tissue, have emerged as a druggable axis in several human cancers. The discovery that ovarian cancer cells express splice variant 1 (SV1) of the GHRH receptor positions GHRH antagonists as potential antiproliferative agents in this disease. Crosstalk between the GHRH receptor system and the EGFR/Akt mitogenic cascade provides a mechanistic rationale for targeting this axis to blunt tumor growth and survival.
Study Design
JMR-132 (a novel GHRH antagonist) was tested at 100 nM and across a dose range in two human ovarian cancer cell lines, SKOV3 and CaOV3, both confirmed to express SV1 of the GHRH receptor by RT-PCR. Cell proliferation was measured using the MTT assay in time-dependent and dose-dependent experimental designs. Western blotting assessed protein-level changes in EGFR, phosphorylated Akt (p-Akt), and cleaved caspase-3. siRNA-mediated knockdown of EGFR was employed to establish pathway dependency, and EGF was used as a proliferative stimulus to test whether JMR-132 could attenuate EGF-driven growth and anti-apoptotic signaling.
Results
JMR-132 exerted strong antiproliferative effects on both SKOV3 and CaOV3 cells in a time-dependent and dose-dependent fashion as measured by MTT assay. The compound also induced activation of cleaved caspase-3 in both cell lines in a time- and dose-dependent manner, indicating engagement of the apoptotic cascade. Treatment with JMR-132 significantly decreased EGFR protein levels and reduced phosphorylation of Akt (p-Akt), demonstrating direct suppression of the EGFR-Akt survival pathway.
Treatment of SKOV3 and CaOV3 cells with 100 nM JMR-132 attenuated both proliferation and the anti-apoptotic effect induced by EGF in both cell lines.
Critically, when EGFR expression was knocked down by siRNA, the antiproliferative effect of JMR-132 was abolished in both SKOV3 and CaOV3 cells, providing mechanistic confirmation that JMR-132's activity is dependent — at least in part — on intact EGFR signaling.
Key Findings
- JMR-132 inhibited SKOV3 and CaOV3 proliferation in both time- and dose-dependent fashion via MTT assay.
- JMR-132 increased cleaved caspase-3 in both cell lines in a time- and dose-dependent manner.
- 100 nM JMR-132 blocked EGF-induced proliferation and anti-apoptotic signaling in both cell lines.
- JMR-132 significantly decreased EGFR protein levels and reduced p-Akt phosphorylation.
- siRNA knockdown of EGFR abolished the antiproliferative effect of JMR-132 in both cell lines.
Why It Matters
GHRH antagonists like JMR-132 may represent a mechanistically distinct antiproliferative strategy for ovarian cancers expressing SV1 of the GHRH receptor, targeting the EGFR-Akt axis without being a direct EGFR inhibitor. For clinicians, this suggests that receptor splice-variant profiling of ovarian tumors could help identify patients most likely to respond. The functional link to EGFR signaling also opens a potential rationale for combining GHRH antagonists with existing EGFR-targeted therapies, though no combination data are presented here. Translation to clinical use remains early — all current evidence is cell-line based — but the defined dose of 100 nM and the clear pathway dependency provide a foundation for in vivo and eventually clinical investigation.
