Side population in hepatocellular carcinoma HCCLM3 cells is enriched with stem-like cancer cells.

Substantial evidence implicates that low-abundance cancer stem cells (CSCs) are responsible for tumor metastasis and recurrence in hepatocellular carcinoma (HCC). Side population (SP) cells possess typical CSCs-like features, and are frequently considered as a special subpopulation in which CSCs are enriched and in studies may be considered as a substitute for CSCs. The aim of the present study was to examine the abundance of SP cells in human HCC cell lines with different metastatic potentials and compare their CSC-like, tumorigenic and invasive properties with those of the main population (MP) cells. An experimental system is described for identifying SP cells and analyzing their CSC-like properties. The relative abundance of SP cells correlated directly with the metastatic potential of the HCC cell line: HCCLM3, 16.3±2.2%; MHCC97-H, 8.4±0.7%; MHCC97-L, 4.7±0.5%; and Huh7, 1.0±0.3% (P<0.05). SP cells isolated from HCCLM3 cultures showed significantly higher proliferation rates and clonogenicity than the corresponding MP cells, in addition to higher migration and invasive abilities in vitro and greater tumorigenicity in mice. Expression levels of all CSC-associated genes tested, except EpCAM and Oct4, were significantly higher in SP cells. The findings revealed that the proportion of SP cells correlates with metastatic potential, and SP cells demonstrated the characteristics expected of CSCs, implicating them in HCC metastasis. Further studies on the identification and characterization of SP cells using clinical HCC specimens will contribute to the understanding of how SP cells are involved in these disease processes.

COX-2 Promotes Migration and Invasion by the Side Population of Cancer Stem Cell-Like Hepatocellular Carcinoma Cells.

Cancer stem cells (CSCs) are thought to be responsible for tumor relapse and metastasis due to their abilities to self-renew, differentiate, and give rise to new tumors. Cyclooxygenase-2 (COX-2) is highly expressed in several kinds of CSCs, and it helps promote stem cell renewal, proliferation, and radioresistance. Whether and how COX-2 contributes to CSC migration and invasion is unclear. In this study, COX-2 was overexpressed in the CSC-like side population (SP) of the human hepatocellular carcinoma (HCC) cell line HCCLM3. COX-2 overexpression significantly enhanced migration and invasion of SP cells, while reducing expression of metastasis-related proteins PDCD4 and PTEN. Treating SP cells with the selective COX-2 inhibitor celecoxib down-regulated COX-2 and caused a dose-dependent reduction in cell migration and invasion, which was associated with up-regulation of PDCD4 and PTEN. These results suggest that COX-2 exerts pro-metastatic effects on SP cells, and that these effects are mediated at least partly through regulation of PDCD4 and PTEN expression. These results further suggest that celecoxib may be a promising anti-metastatic agent to reduce migration and invasion by hepatic CSCs.

Adjuvant transarterial chemoembolization after curative resection of hepatocellular carcinoma: propensity score analysis.

AIM: To compare survival and recurrence in hepatocellular carcinoma (HCC) patients who did or did not receive adjuvant transarterial chemoembolization (TACE). METHODS: A consecutive sample of 229 patients who underwent curative resection between March 2007 and March 2010 in our hospital was included. Of these 229 patients, 91 (39.7%) underwent curative resection followed by adjuvant TACE and 138 (60.3%) underwent curative resection alone. In order to minimize confounds due to baseline differences between the two patient groups, comparisons were conducted between propensity score-matched patients. Survival data and recurrence rates were compared using the Kaplan-Meier method. Independent predictors of overall survival and recurrence were identified using Cox proportional hazard regression. RESULTS: Among 61 pairs of propensity score-matched patients, the 1-, 2-, and 3-year overall survival rates were 95.1%, 86.7%, and 76.4% in the TACE group and 86.9%, 78.5%, and 73.2% in the control group, respectively. At the same time, the TACE and control groups also showed similar recurrence rates at 1 year (13.4% vs 24.8%), 2 years (30.6% vs 32.1%), and 3 years (40.1% vs 34.0%). Multivariate Cox regression identified serum alpha-fetoprotein level ≥ 400 ng/mL and tumor size > 5 cm as independent risk factors of mortality (P < 0.05). CONCLUSION: As postoperative adjuvant TACE does not improve overall survival or reduce recurrence in HCC patients, further study is needed to clarify its clinical benefit.