They examined how well the cells grew in the transformation and expansion process. A “pass” was considered a fivefold expansion in response to CD3/CD28 exposure for 7 days. Normal donor cells typically expand 20- to 30-fold in this time.
Only T cells taken from ALL and Wilms tumor patients before chemotherapy achieved a pass, Dr. Barrett said. Most of the ALL expansions (80%) and half of the Wilms tumor expansions passed. “We noted very poor CAR T-cell potential in all the other tumor types – less than a 30% pass. We noted a decline in potential with cumulative chemotherapy in all cases, though this was particularly significant in children less than 3 years old.”
The team also used RNA profiling to look at the cells’ metabolic pathways. Dr. Barrett noted that T cells are highly metabolically adaptable, capable of using several different fuel types and switching from one to another. Glucose and fatty acids are frequent fuels. Most of the cells from patients with solid tumors exhibited a glycolytic metabolism, while cells from patients with ALL and Wilms tumor appeared to rely more on fatty acids.
“One is not inherently worse than the other,” he said. “But glycolysis appears to be a bad thing when we’re trying to turn them into CAR T cells. Those T cells were too exhausted to do anything.”