Antitumor effects of genetically engineered stem cells expressing yeast cytosine deaminase in lung cancer brain metastases via their tumor-tropic properties

Abstract

Abstract. Although mortality related with primary tumors is approximately 10%, metastasis leads to 90% of cancerassociated death. The majority of brain metastases result from lung cancer, but the metastatic mechanism remains unclear. In general, chemotherapy for treating brain diseases is disrupted by the brain blood barrier (BBB). As an approach to improve treatment of lung cancer metastasis to the brain, we employed genetically engineered stem cells (GESTECs), consisting of neural stem cells (NSCs) expressing a suicide gene. Cytosine deaminase (CD), one of the suicide genes, originating from bacterial (bCD) or yeast (yCD), which can convert the nontoxic prodrug, 5-fluorocytosine (5-FC), into 5-fluorouracil (5-FU), can inhibit cancer cell growth. We examined the therapeutic efficacy and migratory properties of GESTECs expressing yCD, designated as HB1.F3.yCD, in a xenograft mouse model of lung cancer metastasis to the brain. In this model, A549 lung cancer cells were implanted in the right hemisphere of the mouse brain, while CM-DiI pre-stained HB1.F3.yCD cells were implanted in the contralateral brain. Two days after the injection of stem cells, 5-FC was administered via intraperitoneal injection. The tumor-tropic effect of HB1.F3.yCD was evident by fluorescent analysis, in which red-colored stem cells migrated to the lung tumor mass of the contralateral brain. By histological analysis of extracted brain, the therapeutic efficacy of HB1.F3.yCD in the presence of 5-FC was confirmed by the reduction in density and aggressive tendency of lung cancer cells following treatment with 5-FC, compared to a negative control or HB1.F3.yCD injection without 5-FC. Taken together, these results indicate that HB1. F3.yCD expressing a suicide gene may be a new therapeutic strategy for lung cancer metastases to the brain in the presence of a prodrug. IntroductionMetastasis is an insidious movement of cancer cells from primary tumor sites to distant organs and tissues, including the brain, liver, and bones, via blood and lymphatic vessels. Metastasis accounts for over 90% of lethality in cancer patients (1). Particularly, brain metastasis is the most common intracranial neoplasm and arises in 10-40% of all cancer patients (2). Because metastases in the brain may rapidly compromise central nervous system (CNS) function, it is a significant cause of cancer-related morbidity and mortality worldwide (3). The most common origins of brain metastases include primary cancers of the lung, breast and skin (4). Lung cancer, the most prevalent cancer in men, is the leading cause of cancer-related death in the developed world (5). Of all malignancies, primary lung cancer has the highest incidence for brain metastasis and approximately 40% of all patients with lung cancer develop brain metastasis, followed by breast cancer (6). For treating these brain metastases, therapies usually include surgery, chemotherapy, and radiotherapy, but these therapies have many side effects in the nervous system (7). Therefore, brain metastasis is a very critic...

Development and application of neural stem cells for treating various human neurological diseases in animal models

“…CE can convert the prodrug CPT-11 to the toxic compound SN-38 [66]. Yi et al also investigated the effect of NSCs expressing the yeast CD (yCD) gene in an animal model of metastatic lung cancer [67]. Expression of yCD appears to be far more effective for converting 5-FC into 5-FU compared to bacterial CD, both in vitro and in vivo [68].…”

Frontiers in Suicide Gene Therapy of Cancer

“…The human embryonic stem cells, mesenchymal stem cells, as well as the induced stem cells are bioengineered to deliver therapeutics. Some of them they have affinity for targeting gliomas, while the others towards breast cancer metastasis to the brain; all after intravenous injection [135–148]. This feature makes them perfect vectors for carrying therapeutic genes.…”

“…Adding valproic acid significantly enhances activity of thymidine kinases [142]. The stem cells are being tested for their potential for carrying the suicidal genes also into variety of other tumors [135–148]. …”

“…HSV-TK is effectively used in cancer suicide gene therapy by expression in targeted cells to exert intracellular effects outlined above [15–19, 22–24]. Alternatively, TK is also secreted into the extracellular fluids by genetically engineered cells [135–148]. Thereafter, it is internalized by surrounding cancer cells to cause their death.…”

Effects of Genetically Engineered Stem Cells Expressing Cytosine Deaminase and Interferon-Beta or Carboxyl Esterase on the Growth of LNCaP Prostate Cancer Cells

“…An extensive proliferative potential and inherent capacity to target tumors make stem cells a unique tool as cellular vehicles for targeted-gene protocols [22,23]. An efficient gene delivery system using stem cells maximizes the anti-tumor effects of transduced suicide genes or anti-tumor cytokine genes such as IFN-β [24]. Stem cell tumor tropism results from the migration of these cells to tumor cells or sites.…”