Thymidine kinase/ganciclovir and cytosine deaminase/5-fluorocytosine suicide gene therapy-induced cell apoptosis in breast cancer cells

Abstract

The present study was conducted to explore the efficacy of suicide gene therapy with thymidine kinase (TK) in combination with cytosine deaminase (CD) for breast cancer. The expression of CD/TK was detected in the infected cells by RT-PCR. The killing effect on MCF-7 cells following treatment was analyzed by MTT assay. The morphological characteristics of the cells were observed by electron microscopy, and the distribution of the cell cycle was analyzed by flow cytometry. Caspase‑3 and -8 activities were detected by absorption spectrometry. Cytotoxic assays showed that cells transfected with CD/TK became more sensitive to the prodrugs. Morphological features characteristic of apoptosis were noted in the MCF‑7 cells via electron microscopy. The experimental data showed that the proportion of MCF-7 cells during the different phases of the cell cycle varied significantly following treatment with the prodrugs. The activity of caspase‑3 gradually increased following treatment with increasing concentrations of the prodrugs. We conclude that the TK/ganciclovir and CD/5-fluorocytosine suicide gene system used here induces apoptosis in breast cancer cells, and provides a promising treatment modality for breast cancer.

All-trans retinoic acid enhances bystander effect of suicide gene therapy in the treatment of breast cancer

“…Single suicide gene therapy often results in tumor relapse and combination gene therapy may potentially overcome the limitations of single gene therapy and improve the therapeutic efficacy (3,4). Our previous study confirmed that the double suicide gene system (CD/TK) driven by VEGF promoter can inhibit proliferation of human breast cancer cells and induce cancer cells apoptosis in vitro (5) yet even this strategy does not completely eradicate advanced tumors often seen in clinic.…”

Adenoviral-mediated imaging of gene transfer using a somatostatin receptor-cytosine deaminase fusion protein

“… 30 , 31 In addition, the efficacy of this GDEPT approach has been enhanced by creating uracil phophoribosyltransferase fusion genes with CD, thymidine kinase fusion genes with CD, or mutant bCD enzymes to increase the catalytic conversion of 5-FC to 5-FU. 5 , 11 , 12 , 32 , 33 However, one of the major limitations of adenoviral-based gene therapy in general, and specifically CD-based molecular chemotherapy, is the inability to determine the level of in vivo gene transfer non-invasively. Tissue biopsies to determine levels of gene transfer are not ideal because they are invasive, not easily repeated, and are subject to sample variability that does not give a global picture of gene transfer.…”

“…Adenoviral-mediated delivery of CD has demonstrated success in animal models for treating several types of cancer including glioblastoma multiforme, colon, prostate, and breast either alone or in combination with radiation therapy. 4 – 11 In this regard, both the bacterial CD (bCD) and yeast CD (yCD) enzymes have been utilized. The yCD has been shown to have a K m that is 22-fold lower than bCD for 5-FC, but is also more thermolabile than bCD, which may impact gene therapy strategies.…”

A double safety lock tumor-specific device for suicide gene therapy in breast cancer

“…Different approaches have been developed in gene therapy to treat breast cancer, including the transfer of toxic or pro-apoptotic genes. To date, most research into suicide gene therapy in breast cancer has focused on the use of viral vectors [5][6][7][8][9], mainly due to their higher transfection levels. Thus, herpes simplex virus thymidine kinase (HSVtk) gene has been delivered by an adenovirus in combination with ganciclovir as the first and most common strategy used in experimental and clinical studies of suicide gene therapy [10,11].…”