Master of Science
Dr. Neil Gelman and Dr. Donna Goldhawk
Using magnetic resonance imaging, relaxation rate measurements were
performed in cancer cells overexpressing a magnetotactic bacterial gene, MagA.
Measurements of magnetic resonance relaxation rates in this expression
system is important for optimizing cell detection and specificity, for developing
quantification methods, and for refinement of gene-based iron contrast using
magnetosome associated genes. We measured the total transverse
relaxation rate (R2*), its irreversible and reversible components (R2 and R2′,
respectively) and the longitudinal relaxation rate (R1) in MDA-MB-435 tumor cells.
Clonal lines overexpressing MagA were cultured in the presence and absence of
iron supplementation, and mounted in a spherical phantom for relaxation rate
measurements at 3Tesla. In addition to MR measures, cellular changes in iron
were evaluated by inductively-coupled plasma mass spectrometry. Values of R2*
and R2ʹ were significantly higher (p < .01, accounting for multiple comparisons)
in iron-supplemented, MagA- expressing cells compared to unsupplemented
cells. R2* provided the greatest absolute difference and R2′ showed the greatest
relative difference, consistent with the notion that R2′ may be a more specific
indicator of iron-based contrast than R2, as has been observed in brain tissue.
R2 differences between the supplemented and non-supplement MagA-
expressing cells showed a trend (p < .05) toward significance. R1 differences
between these conditions were not significant. For parental cells, no significant
differences between iron-supplemented and unsupplemented cells were
observed in any of the relaxation rates. The results highlight the
potential of magnetotactic bacterial gene expression for detecting labeled cells.
Sengupta, Anindita, "MRI Relaxation Rates: A Quantitative Approach to Track Tumour Cells Expressing MagA" (2014). Electronic Thesis and Dissertation Repository. 2161.