Doronin, Konstantin

Oncolytic virotherapy makes use of the natural ability of viruses to infect and kill cancer cells. Adenovirus serotype 5 (Ad5) has been approved for use in humans as a therapy for solid cancers. In this study, we have tested whether Ad5 and low-seroprevalence adenoviruses can be used as oncolytics for multiple myeloma (MM). We show that Ad5 productively infects most myeloma cell lines, replicates to various degrees, and mediates oncolytic cell killing in vitro and in vivo. Comparison of Ad5 with low-seroprevalence Ads on primary marrow samples from MM patients revealed striking differences in the abilities of different adenoviral serotypes to kill normal CD138 – cells and CD138 + MM cells. Ad5 and Ad6 from species C and Ad26 and Ad48 from species D all mediated killing of CD138 + cells with low-level killing of CD138 – cells. In contrast, Ad11, Ad35, Ad40, and Ad41 mediated weak oncolytic effects in all of the cells. Comparison of cell binding, cell entry, and replication revealed that Ad11 and Ad35 bound MM cells 10 to 100 times better than other serotypes. However, after this efficient interaction, Ad11 and Ad35 viral DNA was not replicated and cell killing did not occur. In contrast, Ad5, Ad6, Ad26, and Ad48 all replicated 10- to 100-fold in MM cells and this correlated with cell killing. These data suggest that Ad5 and other low-seroprevalence adenoviruses may have utility as oncolytic agents against MM and other hematologic malignancies.

Abstract Liver tropism of systemically delivered adenoviruses (Ad) represents a considerable challenge for their use as anticancer therapeutics. More than 90% of i.v. injected Ad is rapidly taken up by the liver leading to hepatotoxicity, reduced virus uptake by target tumor tissue, and diminished therapeutic efficacy. The lack of clinical activity of systemically given oncolytic Ad demands for better understanding and improvement of virus pharmacokinetics. We studied the effects of Ad “detargeting” from liver macrophages (Kupffer cells) and hepatocytes on toxicity and anticancer efficacy using a nonattenuated oncolytic Ad expressing enhanced green fluorescent protein-firefly luciferase fusion protein (Ad-EGFPLuc). Kupffer cell depletion before i.v. injection of Ad-EGFPLuc increased transgene expression in the liver 40.7-fold on day 3 after the injection indicating compensatory enhancement of hepatocyte transduction due to increased bioavailability of the virus. Pretreatment of mice with the anticoagulant drug warfarin to block blood factor–dependent binding of the virus to hepatocytes markedly reduced luciferase expression in the liver and mediated the corresponding decrease of hepatotoxicity in mice with intact and depleted liver macrophages. Combined depletion of Kupffer cells and pretreatment with warfarin before a single i.v. injection of Ad-EGFPLuc significantly reduced tumor growth and prolonged survival of nude mice bearing subcutaneous xenografts of aggressive human hepatocellular carcinoma. The improved antitumor activity correlated with enhanced transgene expression and virus spread in the tumors. These data suggest that detargeting oncolytic Ad from liver macrophages and hepatocytes is an effective strategy to increase the therapeutic window for therapy against disseminated tumor sites. [Cancer Res 2008;68(14):5896–904]