The concept of the cancer stem cell (CSC) is neither new nor without controversy. It is important to study these cells since they are often hypothesized to be androgen insensitive and resistant to chemotherapeutics. Therefore, finding reliable markers for identifying and targeting these cells has become increasingly attractive. The hyaluronic acid receptor, CD44, is associated with a wide variety of cell types, including CSCs. CD44 has many different isoforms which can be categorized as belonging to one of two groups; one expressing different combinations of 10 variant extracellular exons (CD44v), and the other only expressing standard exons found in all isoforms, but none of the 10 variant exons (CD44s). CD44s is typically associated with the mesenchymal stem cell niche, while the various CD44v forms are related to hematopoietic stem cells and increased cell adhesion. However, both CD44s and CD44v have been linked to the CSC niche and cancer progression. Similar to CD44, the aldehyde dehydrogenases (ALDH) superfamily expression is also associated with CSCs and cancer progression. Previously, our laboratory demonstrated that epithelial cancer cells undergo an EMT upon exposure to M2 macrophages. In order to obtain a purely epithelial PCa population, our laboratory isolated a single cell clone of PC3 that had high E-cadherin expression, denoted PC3-Epi. PC3-Epi cells were then incubated with M2 macrophages, which caused a stable EMT to occur after only a few days in culture, denoted PC3-EMT. Our finding demonstrate that these PC3 clones exhibit numerous CSC characteristics, such as high ALDH activity, CD44 expression and cell plasticity. FACS analysis of CD44 isoform expression show distinct CSC subpopulations within these PC3-Epi and PC3-EMT cell types. These subpopulations showed the ability to recapitulate the presorted parental population after being returned to culture. This data suggests not only that the PC3 cell line displays numerous CSC characteristics, but also that distinct CSC subpopulations may exist.

Note: This abstract was not presented at the meeting.

Citation Format: James R. Hernandez, Steven M. Mooney, Gonzalo Torga, James E. Verdone, Kenneth J. Pienta. CD44 isoform expression illuminates multiple CSC subpopulations in PC3. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1394. doi:10.1158/1538-7445.AM2015-1394