Cancer gene therapy: developments to 2000

Oxymatrine induces apoptosis in human cervical cancer cells through guanine nucleotide depletion

Oxymatrine is an alkaloid obtained primarily from Sophora roots and has been shown to show anticancer effects in various cancers. However, the cellular and molecular effects of this agent on cervical cancer have been poorly characterized. Here, we investigated the antitumor effect of oxymatrine on a human cervical cancer cell line (HeLa). Our results showed that application of oxymatrine significantly inhibited the cell growth and tumorigenesis in a dose-dependent manner and induced apoptosis through caspase-dependent pathways as determined using flow cytometry and TUNEL staining analysis. To define the proteins potentially related to the mechanisms of action, proteomic analysis was utilized to detect proteins altered by oxymatrine. As the downregulated gene, inosine monophosphate dehydrogenase type II (IMPDH2) was responsible for oxymatrine-induced mitochondrial-related apoptosis. Moreover, oxymatrine depleted intracellular guanosine 5'-triphosphate (GTP) levels by effective IMPDH inhibition. Functional analyses further showed that oxymatrine and tiazofurin, an inhibitor of IMPDH2, sensitized resistant HeLa/DDP cells to cisplatin. In addition, the expression of IMPDH2 in cervical cancer was significantly higher than that in the normal cervical epithelium. Taken together, these findings suggest that targeting of IMPDH2 by potential pharmacological inhibitors, oxymatrine in combination with chemotherapy, might be a promising means of overcoming chemoresistance in cervical cancer with high IMPDH2 expression, and may thus provide new insights into the mechanism of oxyamtrine-induced anticancer effects.

Treatment of colon cancer cells using the cytosine deaminase/5-fluorocytosine suicide system induces apoptosis, modulation of the proteome, and Hsp90beta phosphorylation

The bacterial cytosine deaminase (CD) gene, associated with the 5-fluorocytosine (5FC) prodrug, is one of the most widely used suicide systems in gene therapy. Introduction of the CD gene within a tumor induces, after 5FC treatment of the animal, a local production of 5-fluorouracil resulting in intratumor chemotherapy. Destruction of the gene-modified tumor is then followed by the triggering of an antitumor immune reaction resulting in the regression of distant wild-type metastasis. The global effects of 5FC on colorectal adenocarcinoma cells expressing the CD gene were analyzed using the proteomic method. Application of 5FC induced apoptosis and 19 proteins showed a significant change in 5FC-treated cells compared with control cells. The up-regulated and down-regulated proteins include cytoskeletal proteins, chaperones, and proteins involved in protein synthesis, the antioxidative network, and detoxification. Most of these proteins are involved in resistance to anticancer drugs and resistance to apoptosis. In addition, we show that the heat shock protein Hsp90beta is phosphorylated on serine 254 upon 5FC treatment. Our results suggest that activation of Hsp90beta by phosphorylation might contribute to tumor regression and tumor immunogenicity. Our findings bring new insights into the mechanism of the anticancer effects induced by CD/5FC treatment.

The role of oncology nurses in gene therapy

In February 2001, the Human Genome Project international consortium announced the publication of a draft sequence and initial analysis of the human genome. Although a definitive count of human genes must await further experimental and computational analysis, scientists now estimate that the human genome contains 30000-35000 genes--a much smaller number than initially estimated. The advances in treatment which will result from this research and our improved understanding of cancer at a molecular level will rapidly change the management of cancer. Gene therapy represents one new approach to treatment, but is currently still experimental. This article reviews the important role of the oncology nurse as a member of the multidisciplinary team caring for patients who receive gene therapy as part of a clinical trial.