Time-dependent changes in proliferation, DNA damage and clock gene expression in hepatocellular carcinoma and healthy liver of a transgenic mouse model.

Hepatocellular carcinoma (HCC) is highly resistant to anticancer therapy and novel therapeutic strategies are needed. Chronotherapy may become a promising approach because it may improve the efficacy of antimitotic radiation and chemotherapy by considering timing of treatment. To date little is known about time-of-day dependent changes of proliferation and DNA damage in HCC. Using transgenic c-myc/transforming growth factor (TGFα) mice as HCC animal model, we immunohistochemically demonstrated Ki67 as marker for proliferation and γ-H2AX as marker for DNA damage in HCC and surrounding healthy liver (HL). Core clock genes (Per1, Per2, Cry1, Cry2, Bmal 1, Rev-erbα and Clock) were examined by qPCR. Data were obtained from samples collected ex vivo at four different time points and from organotypic slice cultures (OSC). Significant differences were found between HCC and HL. In HCC, the number of Ki67 immunoreactive cells showed two peaks (ex vivo: ZT06 middle of day and ZT18 middle of night; OSC: CT04 and CT16). In ex vivo samples, the number of γ-H2AX positive cells in HCC peaked at ZT18 (middle of the night), while in OSC their number remained high during subjective day and night. In both HCC and HL, clock gene expression showed a time-of-day dependent expression ex vivo but no changes in OSC. The expression of Per2 and Cry1 was significantly lower in HCC than in HL. Our data support the concept of chronotherapy of HCC. OSC may become useful to test novel cancer therapies.

Improving Drug Penetrability with iRGD Leverages the Therapeutic Response to Sorafenib and Doxorubicin in Hepatocellular Carcinoma.

iRGD is a derivative of the integrin-binding peptide RGD, which selectively increases the penetrability of tumor tissue to various coadministered substances in several preclinical models. In this study, we investigated the ability of iRGD to improve the delivery of sorafenib and doxorubicin therapy in hepatocellular carcinoma (HCC) using established mouse models of the disease. A contrast-enhanced MRI method was developed in parallel to assess the in vivo effects of iRGD in this setting. We found that iRGD improved the delivery of marker substances to the tumors of HCC-bearing mice about three-fold without a parallel increase in normal tissues. Control peptides lacking the critical CendR motif had no effect. Similarly, iRGD also selectively increased the signal intensity from tumors in Gd-DTPA-enhanced MRI. In terms of antitumor efficacy, iRGD coadministration significantly augmented the individual inhibitory effects of sorafenib and doxorubicin without increasing systemic toxicity. Overall, our results offered a preclinical proof of concept for the use of iRGD coadministration as a strategy to widen the therapeutic window for HCC chemotherapy, as monitored by Gd-DTPA-enhanced MRI as a noninvasive, clinically applicable method to identify iRGD-reactive tumors.