This research was done on mice, using the mice's own cancer cells (and reprogramming them), found that the engineered cells moved toward the mice's cancer in the brain then targeted and killed the recurrent and metastatic cancer. They target "cell surface receptors specific to the tumor site" (2)
Corresponding author Khalid Shah MS, PhD, director of the Center for Stem Cell Therapeutics and Imaging (CSTI) in the BWH Department of Neurosurgery and faculty at Harvard Medical School and Harvard Stem Cell Institute (HSCI), "Cell-based therapies hold tremendous promise for delivering therapeutic agents to tumors and may provide treatment options where standard therapy has failed. With our technique, we show it is possible to reverse-engineer a patient's own cancer cells and use them to treat cancer. We think this has many implications and could be applicable across all cancer cell types." This has shown to help the survival rate of these mice and may one day help humans.
This new research will in my opinion will only help broaden the tools for ending cancer. I also have a feeling this kind of re-engineering can be used not only for cancer cells but maybe for infectious diseases as well.