Novel conditionally replicating adenovirus-mediated efficient detection of circulating tumor cells in lung cancer patients.

Circulating tumor cells (CTCs) are present in the blood of cancer patients from the early stage of cancer development, and their presence has been correlated with patient prognosis and treatment responses. Accordingly, CTCs have been attracting attention as a novel biomarker for early detection of cancer and monitoring of treatment responses. However, since patients typically have only a few CTCs per milliliter of blood, development of an accurate and highly sensitive CTC detection method is crucial. We previously developed a CTC detection method using a novel conditionally replicating adenovirus (Ad) that expresses green fluorescence protein (GFP) in a tumor cell-specific manner by expressing the E1 gene using a tumor-specific human telomerase reverse transcriptase (hTERT) promoter (rAdF35-142T-GFP). CTCs were efficiently detected using rAdF35-142T-GFP, but GFP expression levels in the CTCs and production efficiencies of rAdF35-142T-GFP were relatively low. In this study, in order to overcome these problems, we developed four types of novel GFP-expressing conditionally replicating Ads and examined their ability to visualize CTCs in the blood samples of lung cancer patients. Among the four types of novel recombinant Ads, the novel conditionally replicating Ad containing the 2A peptide and the GFP gene downstream of the E1A gene and the adenovirus death protein (ADP) gene in the E3 region (rAdF35-E1-2A-GFP-ADP) mediated the highest number of GFP-positive cells in the human cultured tumor cell lines. Titers of rAdF35-E1-2A-GFP-ADP were significantly higher (about 4-fold) than those of rAdF35-142T-GFP. rAdF35-E1-2A-GFP-ADP and rAdF35-142T-GFP efficiently detected CTCs in the blood of lung cancer patients at similar levels. GFP+/CD45- cells (CTCs) were found in 10 of 17 patients (58.8%) for both types of recombinant Ads.

Treatment of Human Pancreatic Cancers Following Local and Systemic Administration of Oncolytic Adenovirus Serotype 35.

BACKGROUND/AIM: Oncolytic adenoviruses (Ads) (OAds) are gaining attention as an effective remedy for pancreatic cancer. Most OAds are based on human Ad serotype 5 (Ad5) (OAd5); however, two major drawbacks of OAd5 have been reported. Expression of coxsackievirus-adenovirus receptor, a primary infection receptor of Ad5, is often decreased on malignant tumor cells, including pancreatic cancers. More than 60% of adults have neutralizing antibodies against Ad5. Previously, we developed an OAd composed of Ad serotype 35 (Ad35) (OAd35). Ad35 recognizes CD46, which is often up-regulated on pancreatic cancers. In addition, only 20% or fewer adults have anti-Ad35 neutralizing antibodies. MATERIALS AND METHODS: We examined the tumor cell lysis activities of OAd35 in the four human pancreatic cancer cell lines in the presence and absence of human serum. The tumor growth suppression effects of OAd35 after local and systemic administration were evaluated in nude mice bearing human pancreatic tumors. RESULTS: OAd35 showed higher levels of tumor cell lysis activities than OAd5 in the human pancreatic cancer cell lines AsPC-1 and BxPC-3. Although the in vitro tumor cell lysis activities of OAd5 against MIA PaCa-2 and PANC-1 cells were strongly attenuated in the presence of human serum, OAd35 mediated comparable levels of tumor cell lysis in the presence and absence of human serum. Systemic administration of OAd5 did not mediate significant growth inhibition against the subcutaneous BxPC-3 tumor. On the other hand, OAd35 significantly suppressed tumor growth. CONCLUSION: OAd35 would be suitable as an alternative anticancer agent for pancreatic cancer.