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, the 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 a 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 the delivery of cancer therapeutics or imaging agents to express tumors.

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