We propose ERRP(EGF-Receptor Related Peptide), a novel endogenous-secretory-protein and negative-regulator of EGFR, as a potential dual-receptor-specific target-based-agent. We hypothesize that ERRP inhibits proliferation of non-small-cell-lung-cancer(NSCLC) cells by blocking both EGFR and HER2 receptor activation by competing with the ligands and creating inactive heterodimer.
We studied two NSCLC cells, NCI-H226 (high EGFR low HER2) and NCI-H522 (low EGFR high HER2), non-cancer epithelial cell IEC-6 and fibroblast cell NIH-3T3. Baseline EGFR and HER2 expressions were determined by Western Blots. Time course and dose response for the effect of recombinant ERRP (generated with Drosophila-expression-system) on cell growth was determined with MTT assay. Apoptosis assayed using acridine-orange test. NCI H- 522 cells were transfected with EGFR gene converting it into a cell-line with simultaneous EGFR and HER2 over-expression.
There were dose dependent significant inhibition of cell proliferation in both NSCLC cells in response to ERRP and the effect started at 24 hours and was maximal by 48 hours of incubation and the inhibitory effect persisted as long as 96 hours. Compared to controls, both the cell lines showed a significant increase in apoptosis at 48 hours of incubation with 5 ug/ml ERRP. Compared to IEC-6(non-cancer) and 3T3(EGFR-free-fibroblast) cells, ERRP induced %-inhibition of cell-proliferation was significant in both the NSCLC cell line. However the %-inhibition increased by 25% in the HER2 rich NCI-H522 cell-line when this line was turned dual receptor rich ( both EGFR and Her2) by transfecting EGFR gene.
These in-vitro data confirm ERRP’s targeted dual-receptor-specific effect on cell-growth by inhibiting both EGFR/HER1 and HER 2 mediated activity. The effect is related to competitive blockage of the ligand binding site, creation of inactive heterodimer and may partly be mediated by stimulation of apoptosis.
Targeted chemotherapeutic agents are all specific against single receptor i.e. EGFR or HER2 and are either monoclonal antibodies or tyrosine-kinase-inhibitor particles. ERRP is a potential endogenous agent with activity against both EGFR and HER2 receptors, raising hope of a better tolerable and more effective agent.
A.J. Khan, None.