Photo courtesy of Dr Uckun
An engineered protein can enhance the effects of radiation and even overcome radiation resistance to treat B-precursor acute lymphoblastic leukemia (ALL), according to research published in EBioMedicine.
The protein, CD19L-sTRAIL, is a fusion of the CD19 ligand protein, which seeks out and binds to leukemia cells, with soluble TRAIL, a protein that can amplify the potency of radiation if it can be anchored on the membrane of leukemia cells.
Researchers found that CD19L-sTRAIL augmented the potency of radiation therapy even against the most aggressive and radiation-resistant forms of leukemia.
“Even very low doses of radiation were highly effective in mice challenged with aggressive human leukemia cells, when it was combined with [CD19L-sTRAIL],” said Fatih M. Uckun, MD, PhD, of The Saban Research Institute of Children’s Hospital Los Angeles in California.
“Due to its ability to selectively anchor to the surface of leukemia cells via its CD19L portion, CD19L-sTRAIL was 100,000-fold more potent than sTRAIL and consistently killed aggressive leukemia cells taken directly from children with ALL—not only in the test tube but also in mice.”
The researchers found that a combination of low-dose total body irradiation (TBI) and CD19L-sTRAIL greatly improved event-free survival (EFS) in mice that had received a typically fatal dose of cells from a patient with relapsed B-precursor ALL.
The median EFS for mice treated with CD19L-sTRAIL plus low-dose TBI was 72 days, which was significantly longer than the EFS for untreated control mice (17 days, P<0.0001), mice that received TBI alone (64 days, P=0.0014), mice that received CD19L-sTRAIL alone (20 days, P=0.0022), and mice that received a combination of vincristine, dexamethasone, and PEG-asparaginase (17 days, P=0.0033).
Dr Uckun and his colleagues noted that none of the mice that received CD19L-sTRAIL and TBI experienced a toxic death or signs of treatment-related toxicity.
The team also found that TBI plus CD19L-sTRAIL improved progression-free survival (PFS) in CD22ΔE12xBCR-ABL double transgenic mice with radiation-resistant, advanced stage, CD19+ murine B-precursor ALL with lymphomatous features.
The mean PFS was 24.0 ± 4.0 days for mice that received CD19L-sTRAIL plus TBI, which was significantly longer than the PFS for control mice (0 ± 0 days, P<0.0001), mice that received CD19L-sTRAIL alone (3.4 ± 0.9 days, P=0.0003), and mice that received TBI alone (9.0 ± 4.6 days, P=0.020).
Based on these results, Dr Uckun and his colleagues believe that incorporating CD19L-sTRAIL into the pre-transplant TBI regimens of patients with very high-risk B-precursor ALL could improve survival after hematopoietic stem cell transplant.
“We are hopeful that the knowledge gained from this study will open a new range of effective treatment opportunities for children with recurrent leukemia,” Dr Uckun said.
