Abnormal Activity Of Sonic Hedgehog Signaling Pathway In Human Lung Cancers And Hepatocellular Carcinomas

Cancer is one of the biggest threat facing human life, study on the mechanism of cancer development is a hotspot and foreland.Lung cancer is the leading cause of cancer-related death, claiming more than 150,000 lives every year in the US alone (which exceeds the combined mortality from breast, prostate, and Colorectal cancers). The incidence of lung cancer has run the first rank of the all the malignancy in the main cities of the China, and the mortality rate has gone beyond the average rate of the world. Patients with advanced stage of lung cancer, which represents 75% of all new cases, have a median survival time of only 10 months.Liver cancer, with hepatocellular carcinoma (HCC) as the major tumor type, is a malignancy of worldwide significance. The mortality rate of lung cancer has run the second rank of the all the malignancy in China, and the mortality rate for year is 20-40/100,000. HCC ranks as the eighth cause of cancer-related death in American men with 14 000 deaths yearly and is the most rapidly increasing type of cancer in the United States. The medical oncology community is largely unprepared for this looming epidemic of HCC. A majority (70-85%) of patients present with advanced or unresectable disease, making the prognosis of HCC dismal, and systemic chemotherapy is quite ineffective in HCC treatment.Sonic Hedgehog signaling pathway play important role in embryo development, tissue polarity and cell proliferation. Also, it has been proved that this important signaling pathway is activated in adult tissue via mutation or some other mechanism, including basal cell carcinoma, lung cancer, gastric cancer, prostate cancer, Colorectal adenocarcimas and pancreas cancer etc. Special inhibit of the pathway would suppress the cancer cell proliferation.This article mainly focus on the role of Sonic Hedgehog signaling pathway in the popular cancers in China, hepatocellular carcinoma and lung cancer.The work is divided into three parts:1. Target gene expression- Gli1, HIP and PTC1transcripts (in situ hybridization and RT-PCR)proteins (Immunohistochemistry and Western blotting)2. Specific alterations (over-expression or gene mutation)SHH, Su(Fu), HIP, PTC1 or Rab233. Requirement of the Hedgehog pathway for cell functionsCell growth, cell invasion or tumor progressionThe study on the involvement of SHH pathway in lung cancer began at 1997, and since then, a mass of evidences showed that it is involved in different kinds of lung cancers via different mechanism. But its frequency remains unknown. The second part of article, the author examined activation of this pathway in lung cancers by in-situ hybridization and immunohistochemistry, and find that less than 10% of the tumors have elevated Hedgehog target gene expression. Some primary tumors were found with no detectable Su(Fu), a negative regulator of the pathway. These data indicate that activation of the Hedgehog pathway is activated in only subsets of lung cancers. And these activity may caused by overexpression of Sonic Hedgehog or lose expression of Su(Fu).After that, the author checked the expression of some important players of SHH pathway in lung cancers, including Smoothened (SMO), Rab23, the downstream target platelet-derived growth factor receptor alpha (PDGFRα), hedgehog interacting protein (HIP) and hepatocyte nuclear factor 3-beta (HNF3β). Also the author detected whether there is any mutation in the 10 exon of SMO, some gain of function mutation of which could cause ligand independent activity.The result indicate that, some (such as SMO, Rab23 and PDGFRα) but not all players of the Hedgehog pathway express in many lung cancer specimens although other Hedgehog target genes are not frequently detected in lung cancer. Loss of HIP expression was found in several cases of lung cancers. In addition, the article report the nucleus location of Rab23 in lung cancer cells. From these data, we suggest that the regulation of SHH pathway may differ from tumor type to tumor type. By PCR-SSCP, nearly all the tumor samples showed a abnormal line, but only one of them have a mutation of SMO exon 10 were found by DNA sequencing. It indicate that the mutation of exon 10 of SMO may not be the main reason of SHH pathway activity in lung cancers. But the abnormal line in tumor samples is still an interesting clue for us.The third part of this article provides evidence to indicate that Hedgehog signaling activation occurs frequently in HCC. The author detected expression of SHH, PTC1 and Gli1 in 115 cases of HCC and in 44 liver tissues adjacent to the tumor. Expression of SHH is detectable in about 60% of HCCs examined. Consistent with this, Hedgehog target genes PTC1 and Gli1 are expressed in over 50% of the tumors, suggesting that the Hedgehog pathway is frequently activated in HCCs. Of five cell lines screened, the author found Hep3B cells with detectable Hedgehog target genes. Specific inhibition of Hedgehog signaling in this cell lines by smoothened (SMO) antagonist, KAAD-cyclopamine, inhibits cell growth and results in apoptosis. In contrast, no effects are observed after these treatments in HCC36 and HepG2 cells, which do not have detectable Hedgehog signaling. Thus, our data indicate that Hedgehog signaling activation is an important event for development of human HCCs.Also the author checked the expression of some important players of SHH pathway in HCC, including Smoothened (SMO), Rab23, the downstream target platelet-derived growth factor receptor alpha (PDGFRα), hedgehog interacting protein (HIP) and hepatocyte nuclear factor 3-beta (HNF3β), and whether there is any mutation in the 10 exon of SMO.The result indicate that, some (such as SMO, Rab23) players of the Hedgehog pathway express in many HCC specimens, but no expression of PDGFRαis detected by in situ hybridization. Loss of HIP expression was found in several cases of lung cancers. Also, Nucleus location of Rab23 is found in HCC cells. From these data, we suggest that the regulation of SHH pathway may differ from lung cancer. By PCR-SSCP, nearly all the tumor samples detected (10) showed an abnormal line, but only one of them have a mutation of SMO exon 10 were found by DNA sequencing.InnovationBy detecting a mass of lung cancer samples, this article gives the first report about the frequency of abnormal activity in lung cancers. For the first time, the author checked the expression of some important players of SHH pathway in lung cancers. For the first time, this article provides evidence to indicate that Hedgehog signaling activation occurs frequently in HCC. Also the article detected the effect of Hedgehog signaling activation on the growth and proliferation of HCC - Hep3B cell line, checked the expression of some important players of SHH pathway in lung cancers.