These data collectively raise the possibility that the AFP promoter may not activate fused exogenous genes in some of serum AFP-positive HCC cases. On the contrary, frequent expression of the MK gene implies a possible strategy INCB-018424 of MK promoter-based therapy for HCC patients, although the expression is not specific to HCC. The specificity of transcriptional activity by the MK and the AFP promoter has been already demonstrated; both promoters could drive the fused gene in respective MK- or AFP-positive cells but not in MK- or AFP-negative cells (Kanai et al, 1996; Miyauchi et al, 2001). The mechanism of preferential expression of the MK gene in tumours was not fully understood. It could be related with cell growth: forced expression of MK in fibroblasts induced cell transformation (Kadomatsu et al, 1997) and suppressed expression of MK inhibited the tumour growth (Takei et al, 2001).
Recent studies demonstrated feasible application of tumour-specific promoters to oncolytic adenovirus, which could replicate within tumours but not in normal tissues (Heise and Kirn, 2000). The MK promoter-mediated oncolytic adenovirus was not harmful to liver but killed MK-positive tumours (Adachi et al, 2000). These data suggested that MK promoter-based gene therapy could facilitate selective killing of HCC and keep surrounding noncancerous tissues undamaged. The present Northern blot analysis, in fact, implied that MK promoter-mediated gene therapy for HCC would not injure surrounding cirrhosis tissues. Extracorporal intratumoural injection technique could also broaden the application of MK promoter-based therapy for HCC patients.
Since maintenance of residual liver functions is crucial for HCC treatment, the MK promoter could provide an alternative therapeutic approach besides AFP promoter-based Brefeldin_A therapy. The present study suggested that the AFP promoter and the MK promoter are applicable to AFP-high- and AFP-low/nonproducing HCC, respectively, and the feasibility of both kinds of the promoter-based therapy will be investigated in clinical settings. Acknowledgments This work was supported by grants-in-aid for scientific research from the Japan Society for the Promotion of Science (JSPS) and from the Uehara Memorial Foundation. L Yu is supported by the JSPS postdoctoral fellowship. We thank F Hoffman-La Roche (Basel, Switzerland) for their generous gift of GCV.
We have recently reported alterations in muscarinic receptor expression and acetylcholinesterase (AchE) activity in tissues from Sudden Infant Death Syndrome (SIDS) [1], a syndrome for which vagal overactivity has been proposed as a potential risk factor [2].