Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide; its incidence is increasing in the United States. Depending on disease extent and underlying liver status, patients may be treated with local, locoregional, and/or systemic therapy. Recent data indicates that radiotherapy (RT) can play a meaningful role in the management of HCC. Here, we review published experiences using RT for HCC, including the use of radiosensitizers and stereotactic RT. We discuss methods for performing preclinical studies of RT for HCC and biomarkers of response. As a part of the HCC Working Group, an informal committee of the National Cancer Institute’s Radiation Research Program, we suggest how RT should be implemented in the management of HCC and identify future directions for the study of RT in HCC.

The treatment of inherited metabolic liver diseases by hepatocyte transplantation (HT) would be greatly facilitated if the transplanted normal hepatocytes could be induced to proliferate preferentially over the host liver cells. We hypothesized that preparative hepatic irradiation (HIR) should inhibit host hepatocyte proliferation in response to partial hepatectomy (PH). Normal nonirradiated hepatocytes transplanted in this setting should have a selective growth advantage over the host liver cells and should progressively repopulate the liver. To test this hypothesis, we transplanted 5 million hepatocytes from normal Wistar-Roman High Avoidance (RHA) rats into the livers of congeneic bilirubin-uridine 5’-diphosphoglucuronate glucuronosyltransferase (UGT1A1)-deficient jaundiced Gunn rats by intrasplenic injection after one of the following treatments: (1) 68% PH, (2) HIR (50 Gy), or (3) HIR + PH. In rats receiving either PH or HIR alone before HT, serum bilirubin concentrations declined by 25% to 30% in 28 weeks. In contrast, serum bilirubin levels were normalized completely in rats receiving HIR + PH before HT. Massive repopulation of the Gunn rat liver by the UGT1A1-positive Wistar-RHA hepatocytes was shown by UGT1A1 enzyme assay, immunoblot analysis, and immunohistochemical staining of the recipient liver. High-performance liquid chromatography analysis of the bile collected from Gunn rats 5 months after PH, HIR, and HT showed normalization of the pigment profile, with bilirubin diglucuronide and monoglucuronide as the predominant pigments. In conclusion, a preparative regimen of HIR + PH results in massive repopulation of the liver with functionally normal transplanted hepatocytes, resulting in complete correction of a metabolic deficiency. Noninvasive strategies to replace PH for providing proliferative stimuli to the transplanted cells should make this regimen valuable in augmenting the effects of HT for the treatment of liver diseases.

Evolutionarily conserved serum microRNAs predict radiation-induced fatality in nonhuman primates.

Methylthio-DADMe-immucillin-A (MT-DADMe-ImmA) is an 86-pm inhibitor of human 5′-methylthioadenosine phosphorylase (MTAP). The sole function of MTAP is to recycle 5′-methylthioadenosine (MTA) to S-adenosylmethionine. Treatment of cultured cells with MT-DADMe-ImmA and MTA inhibited MTAP, increased cellular MTA concentrations, decreased polyamines, and induced apoptosis in FaDu and Cal27, two head and neck squamous cell carcinoma cell lines. The same treatment did not induce apoptosis in normal human fibroblast cell lines (CRL2522 and GM02037) or in MCF7, a breast cancer cell line with an MTAP gene deletion. MT-DADMe-ImmA alone did not induce apoptosis in any cell line, implicating MTA as the active agent. Treatment of sensitive cells caused loss of mitochondrial inner membrane potential, G₂/M arrest, activation of mitochondria-dependent caspases, and apoptosis. Changes in cellular polyamines and MTA levels occurred in both responsive and nonresponsive cells, suggesting cell-specific epigenetic effects. A survey of aberrant DNA methylation in genomic DNA using a microarray of 12,288 CpG island clones revealed decreased CpG island methylation in treated FaDu cells compared with untreated cells. FaDu tumors in a mouse xenograft model were treated with MT-DADMe-ImmA, resulting in tumor remission. The selective action of MT-DADMe-ImmA on head and neck squamous cell carcinoma cells suggests potential as an agent for treatment of cancers sensitive to reduced CpG island methylation.

Human endogenous retroviruses (HERVs) are transcribed in many cancers including prostate cancer. Human endogenous retrovirus K (HERV-K) of the HML2 subtype is the most recently integrated and most intact retrovirus in the human genome, with many of the viral genomes encoding full- or partial-length viral proteins. To assess transcripts of HERV-K in prostate cancer cell lines and identify the specific HERV-K elements in the human genome that are transcribed, reverse transcriptase-PCR (RT-PCR) and cDNA sequencing were undertaken. Strand-specific RT-PCR, plasmid subcloning, and cDNA sequencing detected the presence of HERV-K(HML2) coding strand transcripts within four prostate cell lines (LNCaP, DU145, PC3, and VCaP). RT-PCR across splice junctions revealed splicing variants for env gene mRNA in three cell lines, two involving previously undescribed alternative splice sites. To determine the HERV-K loci from which the transcripts arose, RepeatMasker was used to compile a list of over 200 HERV-K internal genome segment fragments and over 1,000 HERV-K solo long terminal repeat (LTR) fragments in the human genome. Surprisingly, the sequences identified from internal positions of the viral genome were mostly smaller segments, while the LTRs were relatively intact. Possible reasons for this are discussed. The transcripts in the cell lines tested, arose from several HERV-K loci, with some proviruses being detected in multiple cell lines and others in only one of the four used. In some instances, transcripts from viral antisense strands was also detected. In addition, transcripts from both strands of solo LTRs were detected. These data show that transcripts from HERV-K loci commonly occur in prostate cancer cell lines and that transcription of either strand can occur. They also emphasize the importance of single nucleotide level analysis to identify the specific, individual HERV-K loci that are transcribed, and indicate that HERV-K expression in prostate cancer warrants further study.