Intrinsic susceptibility MRI identifies tumors with ALKF1174L mutation in genetically-engineered murine models of high-risk neuroblastoma

Abstract

The early identification of children presenting ALK(F1174L)-mutated neuroblastoma, which are associated with resistance to the promising ALK inhibitor crizotinib and a marked poorer prognosis, has become a clinical priority. In comparing the radiology of the novel Th-ALK(F1174L)/Th-MYCN and the well-established Th-MYCN genetically-engineered murine models of neuroblastoma using MRI, we have identified a marked ALK(F1174L)-driven vascular phenotype. We demonstrate that quantitation of the transverse relaxation rate R2* (s(-1)) using intrinsic susceptibility-MRI under baseline conditions and during hyperoxia, can robustly discriminate this differential vascular phenotype, and identify MYCN-driven tumors harboring the ALK(F1174L) mutation with high specificity and selectivity. Intrinsic susceptibility-MRI could thus potentially provide a non-invasive and clinically-exploitable method to help identifying children with MYCN-driven neuroblastoma harboring the ALK(F1174L) mutation at the time of diagnosis.

Figure 1. Radiological comparison of the Th-ALK^F1174L/Th-MYCN and Th-MYCN mice with abdominal neuroblastoma.

A) Anatomical transverse T₂-weighted MR images acquired with a rapid acquisition with refocused echoes (RARE) sequence and B) anatomical transverse T₂*-weighted MR images acquired at increasing gradient echo times as indicated, from representative presenting with abdominal neuroblastoma. C) Note the rapidly decaying tumor signal intensity in the Th-MYCN mouse, compared to the more sustained tumor signal observed in the Th-ALK^F1174L/Th-MYCN mouse.

Figure 2. Identification of tumors harboring the ALK^F1174L mutation in MYCN-driven transgenic mice with intrinsic susceptibility MRI.

A) Anatomical transverse T₂*-weighted MR images acquired at TE = 6.8 and 15.6 ms from representative Th-ALK^F1174L/Th-MYCN and Th-MYCN mice with abdominal neuroblastoma during initial air breathing, and at TE = 15.6 ms after 5 minutes of continuous inhalation of 100% oxygen. B) Corresponding parametric tumor transverse relaxation rate R₂* maps calculated during initial air breathing and after 3 minutes of continuous inhalation of 100% oxygen. C) Resulting parametric tumor ΔR₂*_oxygen-air (R₂*_oxygen−R₂*_air) maps. D) Tumor R₂* during initial air breathing, E) tumor R₂* after 5 minutes of breathing 100% oxygen, and F) tumor ΔR₂*_oxygen-air (R₂*_oxygen−R₂*_air) were determined from Th-ALK^F1174L/Th-MYCN and Th-MYCN mice with abdominal neuroblastoma. Individual data points represent the mean of the median values determined from all three imaging slices for each animal, as well as the mean ±1 s.e.m, p, Student's 2-tailed unpaired t-test with a 5% level of significance.

Figure 3. Pathological comparison of tumors from Th-ALK^F1174L/Th-MYCN and Th-MYCN mice with abdominal neuroblastoma.

A) Gross pathology, B) composite images, and C) high magnification (x200) images from hematoxylin and eosin stained sections. Note the presence of large hemorrhagic regions filled with aggregated erythrocytes (*, blood lakes) extravasated from blood vessels (arrowed) in the tumor from the Th-MYCN mouse. D) Composite fluorescence images of uptake of the perfusion marker Hoechst 33342 into tumors from Th-ALK^F1174L/Th-MYCN and Th-MYCN mice with abdominal neuroblastoma. E) Quantitation of Hoechst 33342 uptake revealed significantly lower functionally perfused vasculature in tumors of Th-ALK^F1174L/Th-MYCN mice (n = 5) compared with tumors in Th-MYCN mice (n = 5). Data are mean ±1 s.e.m, p, Student's 2-tailed unpaired t-test with a 5% level of significance.