Now we can test drugs on actual tumors, not 2D sheets of cells.
HeLa cells under a microscope (image not from 3D printing study). Image: Pablo Ramdhor/Flickr
For the first time ever, scientists have 3D printed a cancer tumor in order to study how to kill it.
Growing cancer cells in a laboratory is nothing new—it’s often how new drugs are tested before they hit clinical trials. But those cultures are grown on petri dishes, where they’re unable to become actual “tumors” and are instead simply sheets of 2D cells. That means that a drug might work on cancer cells in a lab, but once it’s tested on an actual tumor, the three dimensional structure of it can throw in some added kinks that makes it ineffective. Wei Sun of Drexel University saw that the 3D printing of living cells has improved enough to make printing of actual tumors a viable possibility.
In a paper published in the Institute of Physics’ journal Biofabrication, Sun describes the advantages of creating actual tumors (that simulate cervical cancer) over testing drugs on single 2D-layers of cells.
“Comparisons of 3D and 2D results reveal that the HeLa cells showed a higher proliferation rate in the printed 3D environment and tended to form cellular spheroids, but formed monolayer cell sheets in the 2D culture. HeLa cells in 3D printed models also showed higher protein expression and higher chemoresistance than those in 2D culture. The results also reveal that the printed 3D models have more simulated tumor characteristics compared with the 2D planar cell culture models.”
For those of you interested in microbial trivia, HeLa cells are named after Henrietta Lacks, the woman from whom the first “immortal” cell line was created for laboratory research. Basically, HeLa cells are the ones we understand best, because they were the first we ever worked with in a lab.
The top series of photos shows a 2D model, the bottom is a 3D model, which is obviously much more developed. Image: Biofabrication.
The results are pretty impressive: In a human body, cancer cells reproduce at an astounding rate, which is what makes cancer so deadly and difficult to treat. Actually killing the cells often isn’t the problem, targeting the tumor is. In a 2D lab scenario, neither of those problems are addressed.
3D printing raises some of its own problems—the actual process is quite violent (on a cellular level)—at first, it was difficult to create living cells in the correct formations without killing many of them. But, eventually, Sun was able to figure out a method in which more than 90 percent of the printed cells remained viable.
The key to studying cancer in a lab is creating what's known as “replicative immortality,” a hallmark of cancer that basically means that, once a tumor starts dividing and growing, it’s not going to stop.
“Enabling replicative immortality is one of the crucial cancer hallmarks, but tumor cell proliferation in 2D plates was inevitably inhibited by the area of the growth surface,” Sun wrote. In the 3D model, that problem is not fully solved, because once the tumor “floats way” from its growth substance, the tumor experiences “abundant cell loss.” But still, the 3D model is much more realistic (and can grow much larger) than a 2D version.
“Compared with the 2D planar culture, the additional dimensionality of 3D culture leads to differences in cell activities, including morphology, proliferation, and gene and protein expression,” Sun wrote. Basically, the tumor behaves more like a tumor. When you’re trying to find a cure for cancer, that’s huge.