Researchers have developed a method using polymer nanoparticles that that can prohibit the growth of tumor cells.
The scientists at Harvard University coated the polymer nanoparticles with therapeutic antibodies that interfere with the body’s ability to produce what is called the extracellular matrix, a structural scaffolding of proteins and polysaccharides that gives tumor cells a base from which to grow. To produce the same results with antibodies alone would require 30 times the dose, reports Aaron A. Rowe of Chemical & Engineering News. Thus, the researchers say, the polymer nanoparticles could help lead to cancer therapies that have few side effects.
Laboratories have found that interfering with the extracellular matrix can fight tumors. Specifically, by inhibiting the matrix’s enzyme, lysyl oxidase (LOX), the antibodies block the crosslinking of collagen, a major component of the matrix. Without the crosslinking, the scaffolding does not stiffen and tumor growth slows.
Donald Ingber of Harvard thought that the polymer nanoparticles could enhance the effect of the antibodies by concentrating them within tumors. Nanoparticles can accumulate in tumors because they are permeable compared to healthy tissue. “Due to their nanoscale size, they passively enter the tumor but are difficult to wash out,” Ingber says.
The nanoparticles, made from a biodegradable copolymer, were 220 nanometers in size. The researchers then covalently attached the LOX antibodies to the polymer using carbodiimide chemistry.
The Harvard researchers then injected the nanoparticles into mice with mammary tumors. After 12 days, tumors that were treated with the coated nanopolymers were about half the size as those treated with an equivalent dose of LOX antibody without the nanopolymers. Microscope images showed that the tumors without the nanopolymers had collagen fibers that were four times as thick as the ones found in nanoparticle-treated tumors.
Ingber thinks that growth could be retarded further if the nanopolymers could target multiple protein matrices. His colleagues are working on developing such particles.