X-RAY FLUORESCENCE FOR TRACKING CELL DIFFERENTIATION

The importance of C, H, N, S, and P as essential components of biomolecules and the nutritional value of Ca, Mg, Na, K, P, and Cl are well known. However, the roles of trace elements such as Cr, Co, Cu, I, F, Fe, Mn, Mo, Se and Zn in stem cells and cell differentiation are not known. Cell signaling (Ca), activity of metalloproteins (Cu, Zn, Fe, Mg, Mo, Se, Mn), enzymes (Mg), metallothionines, superoxide dismutase (Cu, Zn), matrix metalloproteinases (Zn) and glycosyltransferases (Mn) depend on molecules that rely on elements to maintain tissue homeostasis. Since tissue homeostasis depends on cell proliferation and differentiation it is expected that there will be a corresponding change in concentration of elements. The possibility of characteristic element concentrations signatures (ECS) provides rational for studying the role of these elements in cell differentiation. The technology that can accomplish this is X-ray fluorescence (XRF). Purpose (a): To analyze using XRF several breast cancer cell lines as a model for changes in cell phenotype and function. To validate these ECSs and begin to compile a database will facilitate non-destructive tracking of stem cell differentiation in vitro and their applications to regenerative medicine. Methods (b): XRF spectroscopy (Bruker, PicoFox) was used to analyze multiple breast cancer cell lines (e.g. MCF10A, T47D, and MCF7) cultured on special discs to determine their ECSs. The ECSs of cell line cells were validated using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results (c): After normalization to phosphorous (P) as a control for all 3 cell lines, MCF7 exhibited increased S, K, and Zn levels, while T47D exhibited increased Ca, Fe, Cl and Cu levels. The changes in the T47D cell line, for example, suggest appropriate correlation to the cancer cell's metabolic and functional properties: (i) higher Ca levels seen in micro-calcification, (ii) higher Fe levels likely due to elevated mitochondrial activity, (iii) higher Cl levels due to increased ion transport and (iv) higher Cu levels related to increased proliferation, possible interaction with Cu-superoxide dismutase, and involvement in growth factor signaling. Conclusions (d): Thus, preliminary testing shows the power of XRF technology to distinguish different cell phenotypes. This provides support for our hypothesis that XRF measurements of ECSs can distinguish cell phenotypes and will be useful tool for future characterization of adult stem cells and their differentiation progeny.