Gene expression differences between hemangiosarcoma cells in monolayer and non-adherent sphere culture

Abstract

The cancer stem cell (CSC) theory argues that tumors have a subset of cells that initiate, maintain, and expand cancer in an affected patient. Experimental support for this theory comes from studies that identified sub-populations of cells in a tumor that have the capacity to evade common cancer treatments such as chemotherapy and radiation. Additionally, these same cells exclusively retain the capacity to initiate new disease in xenograft studies. The study of these evasive cells was initially challenging as they differentiate in standard serum-containing culture medium where they grow as a monolayer. In the past decade, methods for culturing stem cells using a serum-free medium has allowed CSCs to be maintained, where they form non-adherent multicellular spheres. Here, we cultured canine hemangiosarcoma (HSA) in both a multicellular sphere and standard monolayer system to compare gene expression using real time qRT-PCR. In our system, the monolayer cultures are a useful surrogate for differentiated tumor cells (the bulk of the tumor), while the serum-free sphere-derived cells are a surrogate for in vivo CSC. Here, we investigate differences in gene expression between these two cultures systems. The genes chosen for study have been shown to be up-regulated in CSCs from various other cancers, or normal stem cells, with minimal expression in differentiated cells. We found gene expression differences between cultures conditions which will allow it to be utilized in the study of hemangiosarcoma as well as possibly other cancers with a CSC.