| With great advances in stem cell and tumor biology, more and more evidences indicate that cancer may be maintained by a rare fraction of cancer stem cells (CSCs) that are able to self-renew, differentiate into multiple cell lineages, and drive tumor continuous growth. The existence of CSCs was well documented in many different cancers including acute myeloid leukemia, breast cancer, and brain cancer. Cancer stem cell hypothesis asserts that CSCs share many properties of normal stem cells and thus account for the clinical outcomes such as recurrence, metastasis and multi-drug resistance. Therefore, the isolation and identification of cancer stem cell has been become a new hot spot in tumor research.Hepatocellular carcinoma (HCC) is one of the most common tumors in our country, and is currently the third-leading cause of cancer death among men in China. Although advance of conventional clinical treatment for HCC has been achieved, the mortality has not been improved significantly over the past several decades, which is largely the result of a high rate of recurrence or metastasis after operation. Therefore, it is necessarry to enforce the studies of the molecular mechanisms of hepatocarcinogenesis and the biologic behaviors of HCC.In HCC, morphologically diverse cells express a variety of hepatic lineage markers and share the similar properties with adult stem cell in many characteristics. In fact, many studies have shown that stem/progenitor cells are involved in hepatocarcinogenesis in certain rodent models and activated stem/progenitor cells are present in human HCC. More recently, a CD133~-positive subpopulation of multipotent cells with extensive proliferative and self-renewal abilities was identified as CSCs in several HCC cell lines, and was proven to contribute to the initiation and growth of HCC, supporting the cancer stem cell hypothesis. Furthermore, re-expression of CD133 has been reported in regenerating rat liver, indicating that CD133 is associated with liver cell proliferation, a possible link to HCC. Thus, isolation and identification of CD133~+ CSCs could elucidate the cellular origin of HCC tumor cells, providing insight into the molecular mechanisms of carcinogenesis, recurrence and metastasis of HCC, and a new strategy for HCC therapyObject:1) To investigate the expression of stem cell marker CD133 in HCC, and then examine the potential prognostic value of CD133 expression in patients with HCC;2) To detect the the sensivities of CD133~+ CSCs to chemotherapic drugs. Furthermore, investigate the expression of ABCG2 in CD133~+ CSCs for helping understand the mechanism of drug resistance.Method:1) Sixty-three resected specimens were collected from HCC patients. The expression of CD133 protein was analyzed by immunohistochemistry, and the association of CD133 expression with clinicopathological characteristics, tumor recurrence and survival of the patients was evaluated.2) The expression of CD133 was explored using flow cytometry in HCC cell lines.3) The killing effects of chemotherapic drugs were performed in HuH-7 cell line in vitro.4) The ABCG2 mRNA expression was determined by semi-quantitative reverse transcription-PCR in CD133~+ and CD133~- subpopulations of HuH-7 cell lines.Result:1) Immunohistochemical analysis of 63 HCC tissue specimens revealed that CD133 positive tumor cells were frequently present in HCC. Increased CD133 immunostaining was found in 26 specimens (41.3%).2) Increased CD133 expression levels were correlated with increased tumor grade (P﹤0.01), advanced disease stage (P﹤0.01), and elevated serum alpha-fetoprotein (AFP) levels (P﹤0.05).3) Kaplan–Meier analysis indicated that patients with increased CD133 levels had shorter overall survival (P﹤0.01)and higher recurrence (P=0.01) rates compared to patients with low CD133 expression. Multivariate analyses revealed that increased CD133 expression was an independent prognostic factor for survival(RR=2.443, P=0.017) and tumor recurrence(RR=2.445, P=0.011) in patients with HCC.4) CD133~+ cells are frequently present in alll of HCC cell lines contain and it ranges from 0.1% to 61%.5) The chemosensivity of drugs showed that CD133~- cells were preferential killed after 24h and 48h of incubation with Dox and 5-Fu compared with CD133~+ cells.6) The result of semi-quantitative RT-PCR showed a preferential expression of ABCG2 mRNA in CD133~+ CSCs cells than CD133~- cells(P﹤0.01)).Conclusion:1) These findings suggest that reactivated CD133 positive cells are frequently present in HCC;2) CD133~+ CSCs not only take part in the initiation of hepatocarcinogeneis but also play an import role in the progression of HCC;3) Increased CD133 expression corresponds with higher stage tumors in HCC, thus indicating a poor prognosis for patients. These data support the cancer stem cell hypothesis;4) There is a preferential expression of ABCG2 in CD133~+ CSC cells. Thus, multi-pathways may take part in multidrug resistance of CD133~+ CSCs except for the activation of anti-apoposis pathway.
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