Tracing and targeting cancer stem cells: New venture for personalized molecular cancer therapy

Table 1 Hallmarks of using cancer stem cell-related markers

Problems	Potential solutions
CSC-related markers may not be specific by their own for a certain type of tumor	Combined used of different markers may be the solution
Some of CSC-related markers may be down-regulated or suppressed in a given tumor due to different genetic or epigenetic regulatory mechanisms	Using of distinct markers or a combination them
Splice variants of some CSC-related markers may render detection difficult	The exact splice variant should be considered for the detection
Markers can be detected using one method (e.g., FACS), but not with other methods (e.g., immunohistochemistry)	Stringent selection of related markers might be required
Different tumors have clonal variation and heterogeneous cell population. Less malignant clones may harbor CSCs that express different markers. Therefore, CSC-related markers may be differentially regulated within different clone or be completely missed	Using more specific and sensitive methods, isolate more enriched CSC populations
Many of reported CSC-related markers are not validated, since they derived from cell-line or mouse model studies	Markers should be validated in xenotransplants or primary human materials

CSC: Cancer stem cell; FACS: Fluorescence-activated cell sorting.