Calcium binding in cytochrome c peroxidase also occurs in a second site located between the two heme ligands in the monomer; however, unlike the first site, the latter is always occupied and, therefore, pH-independent. Lastly, the interplay among ligands and their role in TCTP dimerization in cells became evident when cells were treated with Wogonoside either ligand or a combination of them and TCTP’s capacity to form oligomers was evaluated. In conclusion, our findings establish the need for a conformational change associated with heme binding and TCTP oligomerization as a strategy to sequester potential deleterious excess of free heme in the cell and its environment when secreted. Although any definitive function for the TCTP-heme is a matter of speculation, there are additional possibilities. For example, TCTP might serve as either storage reservoir of heme or cellular sensor of heme availability for purposes of cellular regulation rather than heme scavenger. Moreover,Wogonin TCTP’s ability to respond to elevated levels of Ca2+ makes this unconventional Ca2+ binding protein a versatile biological switch capable of intervening in various signals. As a result, our model sheds light on the elusive behavior of TCTP in both intra- and extracellular compartments. Cancer stem cells are defined as a unique subpopulation in tumors that possess the ability to initiate tumor growth and sustain self-renewal. It has been proposed that they can cause the heterogeneous lineage of cancer cells that constitute the tumor as well as play an important role in the malignant progression of carcinoma, such as distant metastasis, recurrence, and chemoresistance. CSCs were initially identified in acute myeloid leukemia, but have recently been reported to exist in a wide variety of cancers, including gastric cancer. The identification of CSC markers may open a new therapeutic perspective on the basis of selectively targeting this small population of cells. Recently, it has been reported that CSCs possibly do express their own unique markers, such as aldehyde dehydrogenase 1, CD44, and CD133. However, many of the published markers are not unique to CSCs.