Validation of tissue-specific promoter-driven tumor-targeting trans-splicing ribozyme system as a multifunctional cancer gene therapy device in vivo.

A trans-splicing ribozyme that can specifically reprogram human telomerase reverse transcriptase (hTERT) RNA was previously suggested as a useful tool for tumor-targeted gene therapy. In this study, we applied transcriptional targeting with the RNA replacement approach to target liver cancer cells by combining a liver-selective promoter with an hTERT-mediated cancer-specific ribozyme. To validate effects of this system in vivo, we constructed an adenovirus encoding for the hTERT-targeting trans-splicing ribozyme under the control of a liver-selective phosphoenolpyruvate carboxykinase promoter. We observed that intratumoral injection of this virus produced selective and efficient regression of tumors that had been subcutaneously inoculated with hTERT-positive liver cancer cells in mice. Importantly, the trans-splicing reaction worked equally well in a nude mouse model of hepatocarcinoma-derived peritoneal carcinomatosis, inducing the highly specific expression of a transgene, and moreover, the efficient regression of the hTERT-positive liver tumors with minimal liver toxicity when systemically delivered with the adenovirus. In addition to the observed hTERT-dependent therapeutic gene induction, significant reductions in the levels of hTERT RNA (approximately 75%) were also observed. In conclusion, this study demonstrates that a cancer-specific RNA replacement approach using trans-splicing ribozyme with a tissue-selective promoter represents a promising strategy for cancer treatment.