CSC can be identified and isolated via cell surface or internal markers that are over-expressed in these cells. We have identified and continue to discover new CSCs markers that enable us to quantify the number of CSCs in patient biopsies as well as separate these cells away from the the bulk tumor population in order to interrogate them on a single-cell level
Model of PaCSC autofluorescent vesicle formation. ABCG2 is translated in the ER as a six transmembrane domain nonfunctional monomer containing a NBD (nucleotide binding domain). ABCG2 is subsequently folded and glycosylated in the ER (1), and transported through the Golgi (2) to the plasma membrane where it localizes as a functional transporter (3). In general, misfolded ABCG2 undergoes ER-associated degradation (ERAD). Recently, however, it has been shown that over-expression of the E3 ubiquitin-ligase co-factor Derlin-1, can suppress ER to Golgi transport of ABCG2, resulting in ER retention. We hypothesize that in CSCs, ABCG2 is not only over expressed, but it is retained in the ER via a Derlin-1 mediated process, and as a consequence ABCG2-coated ER-derived vesicles form (4). These vesicles can then act as intracellular sink for riboflavin (5), a natural substrate for ABCG2, resulting in the formation of the CSC autofluorescent vesicle.
CSC biomarkers. Human pancreatic cancer stem cells can be identified using cell surface markers (EpCAM, CD133, CD44, CXCR4, ABCG2, CCR7) as well as functional markers (ALDH1). We have added to this list by identifying additional cell surface markers, such as CD47, P2X7R, FPR2 and ANTXR, as well as functional markers, such as riboflavin accumulation in ABCG2-coated vesicle (i.e. autofluorescence).
While no one marker or combination of markers can identify all of the CSC populations present within a tumor at a given time, we hope that by identifying new markers, we can fine tune our ability to identify and isolate these cells.
Our laboratory is work towards this goal by using new approaches to scan the surface of CSCs in search of new CSC markers.