The folate receptor alpha (FRα) is highly expressed in ovarian cancer and not in normal tissues. An FRα binding peptide C7 (Met-His-Thr-Ala-Pro-Gly-Trp-Gly-Tyr-Arg-Leu-Ser, MHTAPGWGYRLS)  was found to bind to FRα expressing cells. This tumor-targeting peptide was proved by both phage homing experiment and fluorescence imaging.

Tumor Targeting of Conjugated Synthetic Peptides
1. The FITC conjugated peptide FITC-MHTAPGWGYRLS was dissolved in PBS.
2. The peptide was injected intravenously into a tumor-bearing nude mouse.
3. After 2 h, tumor and other organ tissues were harvested and analyzed using a fluorescence imaging system.

Cell internalization of Synthesized Peptide
1. Cells were seeded in 24 well plates containing coverslips and incubated for 24 hours in medium with FBS.
2. FITC conjugated peptide was incubated with the cells for 4 hours at 37 °C.
3. The cells were washed once with PBS and fixed in 4% paraformaldehyde.
4. Cells were washed three times with PBS and stained with DAPI for 20 min at room temperature.
5. Internalized fluorescent signals were imaged with a confocal microscope.

This tumor-specific peptide could be a potent and selective ligand for FRα. It has a great potential for delivery of cancer therapeutics or imaging agents to FRα expressing tumors.

Reference: Scientific Reports, volume 8, Article number: 8426 (2018)