Expression profiles dysplastic and neoplastic rat liver lesions

Predisposition to hepatocarcinogenesis is under polygenic control. We analyzed gene expression patterns of dysplastic liver nodules (DN) and hepatocellular carcinoma (HCC) chemically-induced in F344 and BN rats, respectively susceptible and resistant to hepatocarcinogenesis, to evaluate effector mechanisms of predisposition genes, and commonalties between transcription signatures of rat and human liver lesions. Gene expression profiles were determined by microarray analysis and validated by quantitative RT-PCR and Western blot. Cluster analysis revealed two distinctive gene expression patterns, the first of which included normal liver of F344 and BN rats and BN rat nodules, and the second one F344 nodules and HCC of both strains. Expression of 91 and 55 genes of DN and HCC, respectively, showed significant interstrain differences. Considering genes mostly associated with cell proliferation we identified a signature predicting DN evolution to HCC. Notably, expression of oncosuppressors Csmd1, Dmbt, Dusp1, and Gnmt ,in DN, and Bhmt, Dmbt1, Dusp1, Gadd45g, Gnmt, Napsa, Pp2ca, and Ptpn13, in HCC, was higher in BN than F344 rats. Comparative genomics approach, using gene expression data from rat lesions, and human HCC with different prognosis (based on survival length), revealed expression patterns of BN and F344 lesions close to those of human HCCs with better and poorer prognosis, respectively, suggesting that similar molecular events contribute to create a phenotype prone to progression in rats and human lesions. In conclusion, we identified a molecular signature of DN prone to progress to HCC and suggest that oncosuppressor genes are determinants of the genetically transmitted resistance to hepatocarcinogenesis.肝细胞癌易感性受多基因调控。本研究分别以对肝细胞癌易感的F344大鼠、以及对其具有抵抗性的BN大鼠为模型，分析化学诱导的发育异常性肝结节（dysplastic liver nodules, DN）与肝细胞癌（hepatocellular carcinoma, HCC）的基因表达模式，旨在解析易感性基因的效应机制，并探究大鼠与人类肝脏病变的转录特征共性。基因表达谱通过微阵列分析进行检测，并经定量实时逆转录聚合酶链反应（quantitative RT-PCR）与蛋白质印迹（Western blot）验证。聚类分析显示两类显著不同的基因表达模式：第一类包含F344与BN大鼠的正常肝脏组织，以及BN大鼠的肝结节；第二类则包含F344大鼠的肝结节与两种品系大鼠的肝细胞癌组织。分别对应发育异常性肝结节与肝细胞癌的91个、55个基因的表达水平，在两个大鼠品系间存在显著差异。针对与细胞增殖高度相关的基因开展分析后，本研究鉴定出可预测发育异常性肝结节向肝细胞癌进展的分子特征。值得注意的是，在发育异常性肝结节中表达的抑癌基因Csmd1、Dmbt、Dusp1及Gnmt，以及在肝细胞癌中表达的抑癌基因Bhmt、Dmbt1、Dusp1、Gadd45g、Gnmt、Napsa、Pp2ca与Ptpn13，其在BN大鼠体内的表达水平均显著高于F344大鼠。本研究采用比较基因组学方法，结合大鼠肝脏病变的基因表达数据与不同预后（基于生存时长）的人类肝细胞癌样本数据，发现BN与F344大鼠的病变组织表达模式分别接近于预后较好与预后较差的人类肝细胞癌样本，这提示在大鼠与人类肝脏病变中，相似的分子事件共同促成了易进展的表型。综上，本研究鉴定出可预测发育异常性肝结节向肝细胞癌进展的分子特征，并提出抑癌基因是遗传介导的肝细胞癌抵抗性的决定性因素。