GTMB 7 - Gene Therapy & Molecular Biology

Cai et al: Lung cancer gene therapytumor environment (Heuze-Vourc’h et al, 2003). Thesefindings suggest the potential efficacy of COX-2 targetedgene therapy, and offer new targets for the furtherdevelopment of prevention and therapy.3. Galectin-3Galectin-3, a member of the β-galactoside-bindinganimal lectins, was recently identified as a key factor intumor metastasis in NSCLC cancer (Yoshimura et al,2003). Galectin-3 has been implicated in tumor invasionand metastasis (Inohara et al, 1998). Compared withhealthy individuals, Galectin-3 serum levels in patientswith lung cancer and some other cancers weresignificantly elevated, especially in patients withmetastatic disease (Iurisci et al, 2000). In vitroexperiments have suggested that Galectin-3 expressionmay play a role in NSCLC cell motility, invasion, andmetastasis (O’Driscoll et al, 2002). A population (10/30)of the NSCLC samples from cell lines and biopsy tissuewere found to overexpress the Galectin-3 protein at levelsthree times higher than those of normal epithelial cells(Yoshimura et al, 2003). Accordingly, Galectin-3 mayrepresent a novel target molecule in NSCLC therapy.Multiple genes are implicated in lung cancerdevelopment and progression to malignancy. Preliminarystudies have proven the tumor suppressor activity of thesenew candidates, such as ganglioside G(D2) (Yoshida et al,2001; Chen et al, 2003), uteroglobin (Lee et al, 2003) andseveral genes in the human chromosome 3p21.3 (Ji et al,2002). However, further investigation is necessary toresolve a number of uncertainties before human trials canbegin.III. Suicide gene therapyA. HSV-tkAlthough the Herpes simplex virus 1 (HSV)thymidine kinase (tk) suicide gene together withganciclovir (GCV) have been successfully used for the invivo treatment of various solid tumors in recent clinicaltrials, a careful assessment and improvement of theefficacy and safety of such a strategy in different tissues inanimal models of human lung cancer is essential beforethey can be used clinically. With the aim of establishing aneffective therapy for pleural metastasis of lung cancer,liposome-mediated transfer of HSK-tk was performed in anude mice model. Direct eradication together with abystander effect contributed to a therapeutic outcome(Nagamachi et al, 1999). Using an orthotopic lung cancermodel employing immunocompetent mice, Fukunaga et al,(2002) have assessed the therapeutic potential ofadenovirus-mediated HSV-tk. Prolonged survival rateswere obtained in mice treated with adenovirally HSV-tktransfectedtumor cells, and were related to genetransduction efficiencies.In order to obtain the specific transduction of HSVtkinto human lung cancer cells, several tumor-specificpromoters have been evaluated. In vitro and ex vivoexperiments have demonstrated the specific expression ofusing gastrin-releasing peptide (GRP) promoter in SBC5human SCLC cell line, in which GRP mRNA expressionwas detected (Inase et al, 2000). However, anotherexperiment on the same cell line showed that neuronspecific enolase (NSE) was not optimal for use in suicidegene transfer to SCLC cells, although NSE mRNA wasexpressed more abundantly in the SBC3 human SCLC cellline than in other cancer cell lines (Tanaka et al, 2001).Myc-Max response element demonstrated potential forspecific expression of HSV-tk in any myc- overexpressingSCLC cells (Kumagai et al, 1996; Nishino et al, 2001). Invivo injections with Ad-MycTK followed by GCVadministration selectively and markedly suppressed thegrowth of myc-overexpressing tumors established in thesubcuties or in the peritoneal cavity of athymic mice; andin contrast to treatment with Ad-CATK, which conferredstrong but nonspecific expression of HSV-tk, no apparentside effects were observed (Nishino et al, 2001). Theseresults emphasis the importance of cell type-specificpromoter selection to target different subpopulations.Carcinoembryonic antigen (CEA) promoter isanother practical choice to reduce toxicity to normal cells,because CEA is found in lung and other cancers (Konishiet al, 1999; Goto et al, 2001). Goto et al, (2001) exploiteda Cre recombinase(Cre)/loxP system consisting of twoadenoviral vectors (one expressing the Cre gene under thecontrol of the CEA promoter (Ad.CEA-Cre), and the otherthe herpes simplex virus thymidine kinase (HSV-TK)gene) to provide a sutilized Cre recombinase(Cre)/loxPsystem to enhance antitumor effects together with minimaladverse reactions in HSV-tk gene therapy againstdisseminated CEA-producing cancer cells in the peritonealcavity of mice. This provided an effective tool againstdisseminated cancer cells without significant side effects.Modification of the HSV-tk gene itself or theprodrug should offer a practical way of improving thistherapeutic system. Delivery of the HSV-TK mutant TK30in a VSV-G pseudotyped retroviral vector, which wasfound to enhance the efficacy of prodrug therapy, provideda therapeutic efficacy after subsequent GCV application inhuman NSCLC cell lines in a preclinical murinexenotransplant model (Kurdow et al, 2002). Recently, twoHSV-tk mutants transferred by adenoviral vector showedmore tumor growth inhibition than the wild-type whentested in several cell lines, including human lung cancerand in their flank tumor models (Wiewrodt et al, 2003).On the other hand, a novel guanosin analog A-5021, whichcan be used more safely than GCV, demonstratedcytotoxic activity as potent as that of GCV in response toretroviral mediated HSV-tk-transduced human lung cancercell lines, but did not exhibit a inhibitory effect on bonemarrow progenitor cells and colony formation (Hasegawaet al, 2000).B. New targets and approaches1. Hypoxanthine-guanine phosphoribosyltransferaseLike HSV-tk, the newly-discovered enzymehypoxanthine-guanine phosphoribosyl transferase(HGPRT), expressed by the parasite Trypanosoma brucei260