Quantification of heparin's antimetastatic effect by single-cell force spectroscopy

Area of Science:

• Biophysics
• Cancer Biology
• Pharmacology

Background:

• Cancer cells circulating in the bloodstream activate platelets, forming a protective cloak that promotes metastasis.
• Heparin, an anticoagulant, has shown reduced metastasis rates and improved survival in cancer patients.
• Heparin is hypothesized to suppress metastasis by inhibiting the interaction between platelet P-selectin and cancer cell ligands.

Purpose of the Study:

• To quantify the antimetastatic effect of heparin on the adhesion between platelets and non-small cell lung cancer cells.
• To elucidate the mechanism by which heparin inhibits cancer cell-platelet interactions, specifically focusing on P-selectin.

Main Methods:

• Developed a single-cell force spectroscopy approach to measure adhesion forces between A549 lung cancer cells and activated platelets.
• Quantified adhesion force (F_A) and detachment work (W_D) using force-distance curves.
• Determined heparin's concentration-response relationship and half-maximal inhibitory concentration (IC₅₀), and assessed P-selectin's role using anti-P-selectin antibodies.

Main Results:

• Heparin significantly reduced cancer cell-platelet adhesion, with IC₅₀ values of 8.01 U/mL for F_A and 6.46 U/mL for W_D.
• Maximum adhesion reduction by heparin was approximately 37.5% for F_A and 38.42% for W_D.
• Heparin demonstrated an additional inhibitory effect when used after anti-P-selectin antibody treatment, confirming P-selectin blockage.

Conclusions:

• Heparin exerts an antimetastatic effect primarily by blocking the P-selectin-mediated interaction between cancer cells and platelets.
• Single-cell force spectroscopy provides a robust method for investigating cancer cell-platelet adhesion and the efficacy of blocking agents.
• Quantification of heparin's inhibitory effect supports its therapeutic potential in reducing cancer metastasis.