Profiling gene expression changes in hepatocellular carcinomas and the identification of novel tumor markers.

摘要

Primary liver cancer is the fifth most common cancer worldwide and is becoming an increasing clinical concern in the United States. Most patients are diagnosed with hepatocellular carcinoma (HCC) at a stage beyond the reach of current therapies resulting in a one year survival rate of less than 20%. Unlike certain other cancers, such as colon cancer, a mutational model has not yet been developed for liver cancer. A detailed understanding of the molecular changes that occur during liver tumorigenesis is a necessary first step towards developing molecular based treatments and diagnostic screens for HCC. In an effort to identify genes that may be deregulated during hepatocarcinogenesis, I compared gene expression profiles between liver tumors from C3H/HeJ male mice and several normal proliferative states of the liver, such as quiescent, regenerating, and newborn. Oligonucleotide microarrays and representational difference analysis (RDA) were used in combination and allowed the identification of both known and novel genes involved in dedifferentiation, proliferation, and neoplastic progression. In general, a decrease in tumor-specific (i.e.proteases) and immune-related genes was observed in the DEN-induced liver tumors. By representational difference analysis, several genes were identified that showed increased expression in murine liver tumors. Two of these novel genes were cloned and characterized due to their significant differential expression in the DEN-induced liver tumors and their potential as novel markers of HCC. CRG-L1 was cloned from mouse livers and is a putative seven transmembrane protein whose upregulation may be specific to hepatocellular carcinomas. CRG-L2 was cloned from murine liver tumors and the putative protein contains two collagen domains and an olfactomedin domain. The restricted expression of CRG-L2 in murine testis and human placenta make it a putative cancer testis antigen and therefore, a potential diagnostic and immunotherapy target. From my studies, I have shown that the molecular changes in DEN-treated C3H/HeJ mice correlate with human HCC. I have also identified two novel genes, CRG-L1 and CRG-L2, that are upregulated in HCC and may be potential diagnostic markers of HCC.