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Published on: May 27, 2011
Infectivity enhanced, hTERT promoter-based conditionally replicative adenoviruses are useful for SCLC treatment
Junji Uchino1, Koichi Takayama, Akiko Harada
1Research Institute for Diseases of the Chest, Graduate School of Medical Sciences, Kyushu University, Maidashi, Fukuoka, Japan.
Abstract:
Treatment of advanced small-cell lung cancer (SCLC) remains one of the major challenges in current medicine because of the high morbidity and mortality of the disease. Advanced stage lung cancer is refractory to conventional therapies and it also has an extremely poor prognosis. As a result, new therapeutic approaches are needed. Telomere maintenance to the regulation of replicative lifespan strongly implies that alterations in telomere biology play an important role during malignant transformation. Cancers that exhibit high levels of telomerase activity, such as all of the SCLC, were examined in a previous study. In this study, we turned the expression of human telomerase reverse transcriptase (hTERT) by tumors to a therapeutic advantage using a conditionally replication-competent adenovirus (CRAd) in which the expression of E1 (early region 1) is controlled by the hTERT promoter. This virus achieved good levels of viral replication in SCLC cells and induced a substantial anticancer effect in vitro and in vivo. As a further enhancement, the cancer cell killing effect was improved with a tropism modification of the virus to express the knob domain of Ad3 (serotype 3 adenovirus), and this improved infectivity for cancer cells. Conversely, the hTERT promoter has low activity in normal tissues, and the CRAd caused no damage to normal lung fibroblast cells. Since the telomerase activity is common in many types of cancers, these CRAds may be applicable to a wide range of tumors. We concluded that the use of hTERT promoter-based CRAds may be a potentially effective strategy for cancer treatment.
Insights
New conditionally replicating adenoviruses (CRAds) target human telomerase reverse transcriptase (hTERT) in small-cell lung cancer (SCLC) cells. This targeted approach shows significant anticancer effects in vitro and in vivo with minimal impact on normal cells.
Area of Science:
- Oncolytic virology
- Cancer biology
- Gene therapy
Background:
- Advanced small-cell lung cancer (SCLC) presents significant treatment challenges due to therapy resistance and poor prognosis.
- Telomere maintenance, regulated by human telomerase reverse transcriptase (hTERT), is crucial in malignant transformation and highly active in SCLC.
- Existing therapies for advanced SCLC are often ineffective, necessitating novel therapeutic strategies.
Purpose of the Study:
- To develop and evaluate a novel oncolytic adenovirus therapy targeting hTERT expression in SCLC.
- To assess the efficacy and safety of a conditionally replication-competent adenovirus (CRAd) engineered with an hTERT promoter.
Main Methods:
- Engineered a CRAd where viral E1 gene expression is controlled by the hTERT promoter, enabling tumor-specific replication.
- Enhanced viral infectivity by modifying tropism to express the Ad3 knob domain.
- Evaluated viral replication, anticancer effects in vitro and in vivo, and toxicity in normal lung fibroblast cells.
Main Results:
- The hTERT promoter-driven CRAd demonstrated significant replication in SCLC cells.
- Substantial in vitro and in vivo anticancer effects were observed.
- Tropism modification enhanced cancer cell infectivity and killing efficacy.
- The CRAd showed minimal damage to normal lung fibroblast cells due to low hTERT activity in healthy tissues.
Conclusions:
- hTERT promoter-based CRAds represent a promising and potentially effective therapeutic strategy for SCLC.
- The tumor-specific targeting mechanism offers a favorable safety profile.
- This approach may be applicable to a wide range of cancers exhibiting high telomerase activity.
