Toshihiro Higashi

Serological expression cloning of antigens eliciting a humoral immune response to a syngeneic mouse sarcoma identified pem (mouse placenta and embryonic expression gene) as a new member of the cancer/testis family. To identify the human homologue of pem, mouse pem sequences and pem-related expressed sequence tags from human testis were used as PCR primers for amplification using human testis cDNA. However, rather than pem, another gene, designated OY-TES-1, was isolated and found to be the human homologue of proacrosin binding protein sp32 precursor originally identified in mouse, guinea pig, and pig. OY-TES-1 maps to chromosome 12p12-p13 and contains 10 exons. Southern blot analysis suggests the presence of two OY-TES-1-related genes in the human genome. In normal tissues, OY-TES-1 mRNA was expressed only in testis, whereas in malignant tissues, a variable proportion of a wide array of cancers, including bladder, breast, lung, liver, and colon cancers, expressed OY-TES-1. Serological survey of 362 cancer patients with a range of different cancers showed antibody to OY-TES-1 in 25 patients. No OY-TES-1 sera reactivity was found in 20 normal individuals. These findings indicate that OY-TES-1 is an additional member of the cancer/testis family of antigens and that OY-TES-1 is immunogenic in humans.

Serum amino acid concentrations in cirrhotic patients with and without hepatocellular carcinoma (HCC) were investigated. Elevation of serum aromatic amino acids (AAA) and methionine levels observed in cirrhotic patients without malignancy was not apparent in cirrhotic cases with HCC, and thus the ratio of branched chain amino acids (BCAA) to AAA was not so diminished in the latter cases. Development of hepatic encephalopathy in cirrhotic patients with HCC led to only a slight change in the serum aminogram characteristic of hepatic failure. In patients who underwent operations, tissue amino acid compositions of hepatocellular, gastric, and colon cancers were compared with each other and their respective surrounding epithelia. Amino acid contents in the tumor tissue were generally higher than those in the respective nontumorous parts, especially in the case of HCC. The methionine, tyrosine, and phenylalanine contents in HCC were much higher than in cirrhotic or normal liver. Serum aminograms in rats with ethionine-induced HCC were similar to those in cirrhotic patients with HCC. Amino acid contents in HCC were much higher than those in the surrounding cirrhotic liver tissue of rats. Serum and liver tyrosine and isoleucine contents rose significantly in rats 5 to 6 weeks after the initiation of a 0.25% ethionine-containing diet. After the 20th week of the experiment, by which time well-differentiated HCC had developed, liver tyrosine and isoleucine contents increased whereas serum isoleucine concentrations decreased. The results suggest that the serum amino acid patterns characteristic of cirrhotic patients with HCC may result from the increased consumption of amino acids by HCC. Determinations of the amino acid levels are also useful for estimating the prognosis and discovering imminent hepatic encephalopathy in cirrhotic patients with HCC.

To determine the role of telomere-mediated gene stability in hepatocarcinogenesis, we examined the telomere length of human liver with or without chronic liver diseases and hepatocellular carcinomas (HCC). The mean telomere restriction fragment (TRF) length of normal liver (n = 13), chronic hepatitis (n = 11), liver cirrhosis (n = 24) and HCC (n = 24) was 7.8 +/- 0.2, 7.1 +/- 0.3, 6.4 +/- 0.2 and 5.2 +/- 0.2 kb, respectively (mean +/- standard error). TRF length decreased with a progression of chronic liver diseases and that in HCC was significantly shorter than that in other chronic liver diseases (p < 0.05). The ratios of TRF length of HCC to that of corresponding surrounding liver of well differentiated (n = 7), moderately differentiated (n = 10) and poorly differentiated (n = 4) HCCs were 0.83 +/- 0.06, 0.75 +/- 0.05 and 0.98 +/- 0.09, respectively. The ratio of poorly differentiated HCC was significantly higher than that of moderately differentiated HCC (p < 0.05). A comparison between the size and telomere length ratio of moderately differentiated HCCs revealed a decrease of the ratio with size until it reached 50 mm in diameter. In contrast, the ratio increased as the size enlarged over 50 mm. These findings suggest that the gene stability of the liver cells mediated by the telomere is reduced as chronic liver disease progresses and that telomerase is activated in poorly differentiated HCC and moderately differentiated HCC over 50 mm in diameter.