Tspan8, CD44v6 and alpha6beta4 are biomarkers of migrating pancreatic cancer‐initiating cells

• Published in: International journal of cancer 2013-07, Vol.133 (2), p.416-426
• Main Authors: Wang, Haobin, Rana, Sanyukta, Giese, Nathalia, Büchler, Markus W., Zöller, Margot
• Format: Article
• Language: English
• Subjects: Adenocarcinoma; Adenocarcinoma - metabolism; Animal tumors. Experimental tumors; Animals; Biological and medical sciences; Biomarkers; Biomarkers, Tumor - blood; Cancer; cancer‐initiating cells; CD44 variant isoforms; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cells; Exosomes - metabolism; Experimental tumors, general aspects; Gastroenterology. Liver. Pancreas. Abdomen; Gene Expression Regulation, Neoplastic; holoclones; Humans; Hyaluronan Receptors - blood; Integrin alpha6beta4 - blood; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical diagnosis; Medical sciences; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Metastasis; Neoplasm Transplantation; Pancreatic cancer; Pancreatic Neoplasms - metabolism; spheroid growth; tetraspanins; Tetraspanins - blood; Tumors
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.28044

Pancreatic adenocarcinoma (PaCa) being the deadliest cancer is partly due to early metastatic spread. Thus, we searched for PaCa‐initiating cell (PaCIC) markers with emphasis on markers contributing to metastatic progression. PaCIC were enriched from long‐term and freshly established lines by repeated selection for spheroid or holoclone growth in advance of evaluating PaCIC markers. Sphere and holoclone formation steeply increased by recloning and remained stable thereafter. Cells not forming spheres or holoclones died on recloning. PaCIC enrichment in spheres and holoclones was accompanied by increased motility, anchorage independence and upregulated CXCR4 expression. After subcutaneous injection in NOD/SCID mice tumorigenicity and, impressively, recovery of metastasizing tumor cells in peripheral blood, spleen, bone marrow, lung and pancreas was strongly increased in spheres and holoclones. PaCIC enrichment in spheres and holoclones was accompanied, besides CXCR4, by upregulated CD44v6, alpha6beta4, weakly CD133 and tetraspanin Tspan8 expression. Notably, CD44v6, alpha6beta4, CXCR4 and Tspan8 expressing PaCa cells had a growth advantage in vivo and became dominating in migrating and in distant organs settled tumor cells. This is the first report showing that CD44v6, alpha6beta4, Tspan8 and CXCR4 are biomarkers in PaCIC allowing for long‐term survival, expansion and migration in immunocompromised mice. The stability of the percentage of PaCIC in long‐term and freshly established lines after a roughly 8‐fold enrichment by cloning indicates PaCIC, though required for long‐term survival, concomitantly depending on support by non‐CIC. What's new? An effective method for the early diagnosis of pancreatic cancer, a rapidly progressing disease, is urgently needed. While one possible approach entails the development of an exosome‐based serum test, suitable markers have yet to be identified and characterized. Here, four pancreatic cancer initiating cell (PaCIC) markers, CD44v6, alpha6beta4, CXCR4, and Tspan8, were found to be up‐regulated in locally growing tumors in NOD/SCID mice and in metastasizing tumor cells cultured ex vivo. The markers' strong expression on PaCIC and their recovery in exosomes suggests that they may be useful for pancreatic cancer diagnosis.