Abstract
Survival rates for acute lymphoblastic leukemia (ALL), the most common childhood cancer, are now
close to 90%, but survivors of childhood cancer are at an increased risk for long term cognitive deficits,
particularly affecting executive function (e.g., attention, planning, inhibitory control, cognitive flexibility).
The chemotherapeutic agent methotrexate (MTX) is used to treat most ALL patients, and is closely
associated with executive function deficits. Thus a pressing need exists to define the mechanisms that link
MTX exposure to cognitive dysfunction, to guide development of intervention strategies to protect the
developing brain, reduce symptoms and optimize quality of life in ALL survivors, during childhood,
adolescence, young and full adulthood.
To that end, we have developed a translationally relevant mouse model of leukemia survival that
combines cancer exposure (mouse leukemic cell line (L1210 cells) with contemporary chemotherapeutic
drugs (vincristine and MTX, with leucovorin rescue) administered during early life. PFC development
extends through adolescence, which renders this area of the brain particularly vulnerable to early life
chemotherapy. Providing a solid premise for the proposed experiments, our mouse model recapitulates
executive function deficits observed in ALL patients. Additionally, in response to early life cancer +
chemotherapy, we have found an increase in the proinflammatory molecules IL-1 and CCL2, as well as a
decrease in white matter associated genes within the PFC. In Aim 1, single cell RNA sequencing will be
used to define the effects of cancer and/or chemotherapy on the transcriptional profile of the PFC.
MTX disrupts folate metabolism to inhibit cell growth, but this disruption also leads to increased levels
of the proinflammatory metabolite, homocysteine (HCY), in both plasma and cerebrospinal fluid. Increased
HCY can drive inflammation, oxidative stress and is associated with both white and gray matter damage,
as well as cognitive impairment. Further executive function deficits have also been linked to altered
synaptic function, and microglia, a brain resident immune cell, can contribute to synapse elimination via
the CD11b(CR3)-C3 phagocytic pathway. Therefore, we hypothesize that MTX-driven increased HCY
levels will lead to neuroinflammation and oxidative stress, leading to gray and white matter damage, and
altered synaptic pruning in the prefrontal cortex, which underlie deficits in executive function.
To test this hypothesis, HCY-lowering strategies (folate and B vitamin supplementation, or the
antioxidant, N-acetylcysteine amide) will be evaluated in Aim 2. Aim 3 will test the necessity of IL-1 activity
while Aim 4 will test the necessity of microglia in mediating the chemotherapy-associated cognitive
deficits, as well as neuroinflammation and oxidative stress, leading to gray and white matter damage, and
altered synaptic pruning in the prefrontal cortex
