Showing identical restriction pattern with pure pUbC-S/MAR plasmid (+), following restriction digest with SpeI enzyme. M: 1-kbp ladder (Hyperladder I, Bioline). doi:10.1371/journal.pone.0047920.gcases the plasmid copy number is calculated to be about one to three vector copies/cell, consistent with previous reports demonstrating a relatively low copy number of S/MAR vector of less than 10 copies/cell [18,25,29]. 
In addition, maintenance of the transgenic marker gene was also shown by PCR analysis on DNA isolated from “cultured” MIA-PaCa2 and Huh7 cells (Figure 4D, lanes 1 and 4) and from two different sites of tumour tissue at 35 days after delivery (Figure 4D, lanes 2,3 for Huh7 and lanes 5,6 for MIA-PaCa2). A PCR product of the expected size, 1091 bps, was generated from DNA of all sources indicating that the pUbC-S/MAR plasmid wasmaintained in both the Huh7 and MIA-PaCa2 cells and throughout the tumour derived from these cells after injection into NOD-SCID mice. This verifies the presence of the pUbC-S/ MAR plasmid both in vitro and in vivo.DiscussionThis work represents the development of murine tumour models derived from two different cell lines. Significantly, this study shows for the first time the establishment of genetically marked murine models of pancreatic and hepatocellular carcino-S/MAR Vectors for In Vivo Tumour Modellingmas using a non-viral episomal plasmid vector. Both HCC and PaCa have high incidences; HCC is the fifth most common form of cancer in the world and accounts for 80?0 of primary liver cancer [30] while there are around 42470 individuals diagnosed with pancreatic cancer each year in the United States with less than a 20 one-year survival rate [31]. Given the prevalence of these diseases, it is vital that an effective method be developed to improve the disease detection and prognosis. The generation of an effective genetically marked murine tumour model for HCC and PaCa is an important step in this process as it will enable the effects of Solvent Yellow 14 potential therapeutics to be more easily and accurately monitored and will therefore enable more reliable data when developing novel anticancer drugs. Attempts to generate genetically marked tumours previously have had limitations, such as the risk of integration with viral vectors and potential insertional mutagenesis. Furthermore the genotoxicity of viral vectors can considerably alter the characteristics of its recipient cell and subsequent daughter cells. When creating tumour xenografts, the fewer alterations made to the original tumour cells the better the representation of the cancer model. Therefore the development of non-viral vectors in cancer research to minimise these adverse effects are crucial. Our previous work has shown strong sustained episomal Peptide M price luciferase expression in vivo, from a pDNA expression system comprising an S/MAR element and a mammalian promoter in the murine liver [11,20,21]. Tracking of the luciferase transgene over time in a single animal without the need for sacrificing animals indicates the utility of this vector in genetically marked tumour cells to track the development of a tumour model simply by in vivo imaging. As shown here, the S/MAR vector enables stable transfection of cancer cells and subsequent development of HCC and PaCa tumour xenografts. This paper describes the first demonstration of the functional use of an S/MAR vector to stably transfect cancer cells to genetically mark tumours in vivo. Previous studies in vitro have sho.Showing identical restriction pattern with pure pUbC-S/MAR plasmid (+), following restriction digest with SpeI enzyme. M: 1-kbp ladder (Hyperladder I, Bioline). doi:10.1371/journal.pone.0047920.gcases the plasmid copy number is calculated to be about one to three vector copies/cell, consistent with previous reports demonstrating a relatively low copy number of S/MAR vector of less than 10 copies/cell [18,25,29]. In addition, maintenance of the transgenic marker gene was also shown by PCR analysis on DNA isolated from “cultured” MIA-PaCa2 and Huh7 cells (Figure 4D, lanes 1 and 4) and from two different sites of tumour tissue at 35 days after delivery (Figure 4D, lanes 2,3 for Huh7 and lanes 5,6 for MIA-PaCa2). A PCR product of the expected size, 1091 bps, was generated from DNA of all sources indicating that the pUbC-S/MAR plasmid wasmaintained in both the Huh7 and MIA-PaCa2 cells and throughout the tumour derived from these cells after injection into NOD-SCID mice. This verifies the presence of the pUbC-S/ MAR plasmid both in vitro and in vivo.DiscussionThis work represents the development of murine tumour models derived from two different cell lines. Significantly, this study shows for the first time the establishment of genetically marked murine models of pancreatic and hepatocellular carcino-S/MAR Vectors for In Vivo Tumour Modellingmas using a non-viral episomal plasmid vector. Both HCC and PaCa have high incidences; HCC is the fifth most common form of cancer in the world and accounts for 80?0 of primary liver cancer [30] while there are around 42470 individuals diagnosed with pancreatic cancer each year in the United States with less than a 20 one-year survival rate [31]. Given the prevalence of these diseases, it is vital that an effective method be developed to improve the disease detection and prognosis. The generation of an effective genetically marked murine tumour model for HCC and PaCa is an important step in this process as it will enable the effects of potential therapeutics to be more easily and accurately monitored and will therefore enable more reliable data when developing novel anticancer drugs. Attempts to generate genetically marked 
tumours previously have had limitations, such as the risk of integration with viral vectors and potential insertional mutagenesis. Furthermore the genotoxicity of viral vectors can considerably alter the characteristics of its recipient cell and subsequent daughter cells. When creating tumour xenografts, the fewer alterations made to the original tumour cells the better the representation of the cancer model. Therefore the development of non-viral vectors in cancer research to minimise these adverse effects are crucial. Our previous work has shown strong sustained episomal luciferase expression in vivo, from a pDNA expression system comprising an S/MAR element and a mammalian promoter in the murine liver [11,20,21]. Tracking of the luciferase transgene over time in a single animal without the need for sacrificing animals indicates the utility of this vector in genetically marked tumour cells to track the development of a tumour model simply by in vivo imaging. As shown here, the S/MAR vector enables stable transfection of cancer cells and subsequent development of HCC and PaCa tumour xenografts. This paper describes the first demonstration of the functional use of an S/MAR vector to stably transfect cancer cells to genetically mark tumours in vivo. Previous studies in vitro have sho.
