Quantification of early gait development: Expanding the application of Catwalk technology to an infant rhesus macaque model

BACKGROUND

Understanding gait development is essential for identifying motor impairments in neurodevelopmental disorders. Defining typical gait development in a rhesus macaque model is critical prior to characterizing abnormal gait. The goal of this study was to 1) explore the feasibility of using the Noldus Catwalk to assess gait in infant rhesus macaques and 2) provide preliminary normative data of gait development during the first month of life.

NEW METHOD

The Noldus Catwalk was used to assess gait speed, dynamic and static paw measurements, and interlimb coordination in twelve infant rhesus macaques at 14, 21, and 28 days of age. All macaque runs were labeled as a diagonal or non-diagonal walking pattern.

RESULTS

Infant rhesus macaques primarily used a diagonal (mature) walking pattern as early as 14 days of life. Ten infant rhesus macaques (83.3%) were able to successfully walk across the Noldus Catwalk at 28 days of life. Limited differences in gait parameters were observed between timepoints because of the variability within the group at 14, 21, and 28 days.

COMPARISON WITH EXISTING METHODS

No prior gait analysis system has been used to provide objective quantification of gait parameters for infant macaques.

CONCLUSIONS

The Catwalk system can be utilized to quantify gait in infant rhesus macaques less than 28 days old. Future applications to infant rhesus macaques could provide a better understanding of gait development and early differences within various neurodevelopmental disorders.

CXCR4 allows T cell acute lymphoblastic leukemia to escape from JAK1/2 and BCL2 inhibition through CNS infiltration

Targeting the JAK/STAT and BCL2 pathways in patients with relapsed/refractory T cell acute lymphoblastic leukemia (T-ALL) may provide an alternative approach to achieve clinical remissions. Ruxolitinib and venetoclax show a dose-dependent effect on T-ALL individually, but combination treatment reduces survival and proliferation of T-ALL in vitro. Using a xenograft model, the combination treatment fails to improve survival, with death from hind limb paralysis. Despite on-target inhibition by the drugs, histopathology demonstrates increased leukemic infiltration into the central nervous system (CNS) as compared to liver or bone marrow. Liquid chromatography-tandem mass spectroscopy shows that ruxolitinib and venetoclax insufficiently cross into the CNS. The addition of the CXCR4 inhibitor plerixafor with ruxolitinib and venetoclax reduces clinical scores and enhances survival. While combination therapy with ruxolitinib and venetoclax shows promise for treating T-ALL, additional inhibition of the CXCR4-CXCL12 axis may be needed to maximize the possibility of complete remission.

Dietary administration of alpha-tocopheryloxyacetic acid induces CD4+ T cell activation and prolongs survival in murine rhabdomyosarcoma

Relapsed sarcomas remain essentially incurable for most children with cancer. Alpha-Tocopheryloxyacetic acid (αTEA) is a scalable semi-synthetic derivative of alpha-tocopherol that has shown promising activity preclinically and clinically in adult cancer, but has not yet been studied in pediatric sarcoma. We hypothesized that αTEA would mediate anti-tumor effects in rhabdomyosarcoma (RMS) by modulating the immunosuppressive milieu. Treatment of murine M3-9-M RMS in vitro with αTEA (2.5–100uM) resulted in increased apoptosis by flow cytometry (Annexin V+/7AAD+) and Incucyte analysis (Annexin V+) within 24 hours (p < 0.05). Using an established orthotopic luciferase+ M3-9-M in vivo RMS model, αTEA-supplemented chow administered for 21 days significantly reduced tumor volume (p < 0.001) and bioluminescence (p < 0.05) by 28 days, resulting in a significant prolongation of survival compared to matched control chow (p < 0.05), up to 4 weeks after the feed was stopped. Analysis of spleens from RMS mice fed αTEA-supplemented diets showed an increased percentage of Ki-67+ and IFNγ+CD4+ T cells (p < 0.01) at the end of treatment as compared to recipients of the control diet. In addition, a decrease in the percentage of CD11b+Arg-1+ (p < 0.01) and PD-L1+ (p < 0.05) cells within the spleen were observed in αTEA-treated RMS tumor-bearing mice. RNA-Seq analysis of RMS tumors is underway to explore changes in αTEA vs. control-treated mice. These results suggest that αTEA causes direct induction of apoptosis of RMS in vitro and in vivo, leading to prolonged survival through enhanced CD4+ T cell stimulation and reduced myeloid cell-mediated immunosuppression in RMS-bearing mice. Further investigation of αTEA as an immunomodulating agent is warranted.

Abstract 2975: CXCR4 blockade of T cell acute lymphoblastic leukemia causes systemic disease in an NSG model allowing ruxolitinib and venetoclax to synergistically treat cancer burden

T-cell acute lymphoblastic leukemia (T-ALL) is a hematologic malignancy that accounts for 25% of adult and 15% of pediatric acute lymphoblastic leukemia (ALL) cases. Relapsed or refractory T-ALL is difficult to salvage with chemotherapy, which causes long-term toxicity, and is often fatal. The JAK/STAT and BCL-2 pathways are upregulated in T-ALL and promote increased T-ALL proliferation and survival. Currently, targeted therapies of the JAK/STAT and BCL-2 pathways have not been investigated in combination. I propose that dual inhibition of the JAK/STAT and BCL-2 pathways, with ruxolitinib and venetoclax respectively, will lead to maximal T-ALL cell death. Jurkat cells were treated with single doses of ruxolitinib (0.156µM - 5µM) or venetoclax (1.56nM - 50nM) in vitro, and analyzed by trypan blue exclusion, MTT and flow cytometry at 24, 48 and 72h post-treatment. Results demonstrate decreased proliferation by MTT, decreased viability by trypan blue exclusion, and increased apoptosis by flow cytometry for the three highest doses of ruxolitinib (1.25µM, 2.5µM and 5µM) and venetoclax (12.5nM, 25nM and 50nM). A synergistic effect was achieved for all three assays at 48 and 72h when cells were treated with a combination dose of ruxolitinib (1.25µM) and venetoclax (25nM; CI<1). This optimal in vitro combined dose significantly decreased proliferation (p<0.0001) and viability (p<0.0001) of Jurkat cells compared to vehicle and single drug treatment groups. Jurkat-GFP cells were injected intravenously into NSG mice to mimic a systemic in vivo xenograft model of T-ALL, and followed for clinical scores and survival. End organs were analyzed for GFP+CD45+ cells by flow cytometry and GFP+ cells by immunohistochemistry (IHC). Compared to single treatments of ruxolitinib and venetoclax, all mice treated with ruxolitinib and/or venetoclax combination therapy developed hind-limb paralysis and died of CNS disease in the spinal cord and brain as shown by IHC. This suggests for the first time that ruxolitinib or venetoclax cannot penetrate the blood brain barrier (BBB). LC-MS-MS studies were performed to confirm that ruxolitinib and venetoclax cannot penetrate the BBB. Previously published data suggests that T-ALL exploits the CXCR4-CXCL12 chemokine pathway to relapse into the CNS. Jurkat cells were analyzed by flow cytometry and showed high expression of the CXCR4 surface receptor while NSG brain tissue showed presence of CXCL12 mRNA and protein by in situ hybridization (ISH) and western blot analysis. Antibody blockade of CXCR4 in vivo prevented the migration of Jurkat cells into the CNS and suggests that disruption of the CXCR4-CXCL12 pathway will result in a systemic model of T-ALL that could allow for ruxolitinib and venetoclax to eliminate T-ALL at primary sites of disease.

Citation Format: Kirsti L. Walker, Sabrina A. Kabakov, Fen Zhu, Sydney L. Olson, Lixin Rui, Christian M. Capitini. CXCR4 blockade of T cell acute lymphoblastic leukemia causes systemic disease in an NSG model allowing ruxolitinib and venetoclax to synergistically treat cancer burden [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2975.