Positive selection of gene-modified cells increases the efficacy of pancreatic cancer suicide gene therapy

Abstract

Thymidine kinase (TK)-mediated suicide gene therapy has been considered for the treatment of pancreatic cancer. However, despite a bystander effect, the proportion of transduced tumor cells has proven too low to result in efficacy. We propose the use of a drug-selectable marker (MDR1) to enrich TK-expressing cells using chemotherapy. This enrichment or positive selection phase may increase the efficacy of suicide gene therapy. To test this strategy, we generated stable NP18MDR/TK-GFP transfectants and showed docetaxel resistance in vivo. Mixed tumors of MDR/TK-expressing cells and parental NP18 cells were established and docetaxel was used to increase the proportion of TK-expressing cells. After this positive selection phase, suicide gene therapy with ganciclovir was applied. Upon positive selection, the proportion of TK-expressing cells increased from 4% to 22%. Subsequent suicide gene therapy was more effective compared with a control group without positive selection. Starting with 10% of TK-expressing cells the positive-negative selection strategy completely inhibited tumor growth. Taken together, these results suggest that a positive-negative selection strategy based on MDR and TK genes represents an efficient way to increase the proportion of TKexpressing cells in the tumor and the efficacy of TKmediated suicide gene therapy.

Controlling the evolution of resistance

“…The recent work of Martinez-Quintanilla et al [27, 28], seeks to overcome this problem using dynamic evolutionary processes. Together with the susceptibility gene to the apoptosis trigger, they also transfect the cells with a resistance gene, providing resistance to another chemotherapeutic agent.…”

“…In [27, 28], the authors transfect pancreatic carcinoma cell cancer lines with a plasmid containing two separate genes. The first gene, herpes simplex virus thymidine kinase (HSV-TK) encodes an enzyme which makes the host susceptible to the action of the drug ganciclovir.…”

“…In Section 4, we present a review of recent work [59, 21, 23, 22] showing how a dynamic multi-strain model of HIV infection can be used to create dynamic treatment schedules that reduce the risk of sequential treatment failures. In Section 5 we review a new approach in cancer therapy which relies on dynamic evolutionary processes to increase the effectiveness of a transgene therapy for tumor killing [28, 27]. We present a new mathematical model of the two-step treatment procedure described in the in Vitro studies, and demonstrate how two separate methods of clinical implementation will require the use of model-based strategies.…”

Intracellular targeted co-delivery of shMDR1 and gefitinib with chitosan nanoparticles for overcoming multidrug resistance

“…25,26 The shRNA target in MDR1 as the new method of gene-mediated interference could inhibit the selectively targeted MDR1 gene expression, increase the intracellular accumulation of drugs, and restore the sensitivity of cells to the drug, thereby reversing drug resistance. [27][28][29][30] Compared to traditional gene-mediated treatment, gene-loaded nanoparticles (NPs) showed promising advantages due to their nano-size and specific body distribution. 31,32 NPs can be internalized more specifically and efficiently than free therapeutic agents, and, more importantly, NPs can be easily aggregated and accumulated inside tumor tissues for a long time, known as the enhanced permeability and retention effect.…”

Isolation of single, intact chromosomes from single, selected ovarian cancer cells for in situ hybridization and sequencing

“…It is translated into the truncated version of the receptor, which is missing a large portion of its extracellular domain. Therefore, it is an ideal target for developing cancer-specific diagnostics and therapeutics with the particular emphasis on cancer suicide gene therapy (Garg et al, 2010;Malecki and Malecki, 2008;Martinez-Quintanilla et al, 2009;Wang et al, 2011;Wu et al, 2009). …”