Suppression of Slit3 induces tumor proliferation and chemoresistance in hepatocellular carcinoma through activation of GSK3ß/ß-catenin pathway.

BACKGROUND: It is essential to understand the mechanisms responsible for hepatocellular carcinoma (HCC) progression and chemoresistance in order to identify prognostic biomarkers as well as potential therapeutic avenues. Recent findings have shown that SLIT3 appears to function as a novel tumor suppressor gene in various types of cancers, yet its clinical correlation and role in HCC has not been understood clearly. METHODS: We determined the transcript levels of Slit3 in tumor and adjacent normal tissues within two cohorts (N = 40 and 25) of HCC patients, and correlated the gene expression with the clinicopathological data. Subsequently, the functional effects and underlying molecular mechanisms of Slit3 overexpression and/or repression were studied using cell-line and mouse models. RESULTS: Our results demonstrated a repression in Slit3 expression in nearly 50% of the HCC patients, while the overall expression of Slit3 inversely correlated with the size of the tumor in both cohorts of patients. Stable down-regulation of Slit3 in HCC cell-lines induced cell proliferation in vitro and tumor growth in vivo, while stable Slit3 overexpression repressed these effects. Molecular investigations showed that the stable Slit3 repression-induced cell proliferation was associated with a higher expression of ß-catenin and a repressed GSK3ß activity. Moreover, Slit3-repression induced chemoresistance to sorafenib, oxaliplatin and 5-FU through impairment of ß-catenin degradation and induction of cyclin D3 and survivin levels. The effects induced by stable Slit3-repression were diminished by transient repression of ß-catenin by siRNA approach. CONCLUSION: This study suggests that Slit3 acts as a tumor suppressor in HCC by repressing the tumor growth and thus tumor progression. Low Slit3 level indicates a poor response of HCC cells to chemotherapy. Restoration or overexpression of Slit3 is a potential therapeutic approach to repress the tumor growth and enhance the efficacy of chemotherapeutic agents.

Preclinical analysis of the anti-tumor and anti-metastatic effects of Raf265 on colon cancer cells and CD26(+) cancer stem cells in colorectal carcinoma.

BACKGROUND: In colorectal carcinoma (CRC), activation of the Raf/MEK/ERK signaling pathway is commonly observed. In addition, the commonly used 5FU-based chemotherapy in patients with metastatic CRC was found to enrich a subpopulation of CD26(+) cancer stem cells (CSCs). As activation of the Raf/MEK/ERK signaling pathway was also found in the CD26(+) CSCs and therefore, we hypothesized that an ATP-competitive pan-Raf inhibitor, Raf265, is effective in eliminating the cancer cells and the CD26(+) CSCs in CRC patients. METHODS: HT29 and HCT116 cells were treated with various concentrations of Raf265 to study the anti-proliferative and apoptotic effects of Raf265. Anti-tumor effect was also demonstrated using a xenograft model. Cells were also treated with Raf265 in combination with 5FU to demonstrate the anti-migratory and invasive effects by targeting on the CD26(+) CSCs and the anti-metastatic effect of the combined treatment was shown in an orthotopic CRC model. RESULTS: Raf265 was found to be highly effective in inhibiting cell proliferation and tumor growth through the inhibition of the RAF/MEK/ERK signaling pathway. In addition, anti-migratory and invasive effect was found with Raf265 treatment in combination with 5FU by targeting on the CD26(+) cells. Finally, the anti-tumor and anti-metastatic effect of Raf265 in combination with 5FU was also demonstrated. CONCLUSIONS: This preclinical study demonstrates the anti-tumor and anti-metastatic activity of Raf265 in CRC, providing the basis for exploiting its potential use and combination therapy with 5FU in the clinical treatment of CRC.

Biology of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a common cancer in the world due to high prevalence of hepatitis B or C virus infection. Research in recent years has uncovered important molecular pathways involved in development and progression of HCC. Several genetic aberrations and molecular mechanisms responsible for initiation of hepatocarcinogenesis have been identified. Novel biomarkers for HCC are being developed for better detection and prognostication. Alpha-fetoprotein, the conventional marker of HCC, has limited sensitivity and specificity. Serum levels of isoforms of AFP based on differential lectin binding of the glycan moiety appear to be more sensitive and specific than total AFP level in early detection of HCC. The clinical usefulness of other HCC biomarkers such as des-gamma-carboxy prothrombin and glypican-3 are under investigation. HCC is an aggressive tumor with early vascular invasion and metastasis. Studies over the past two decades have elucidated the clinical predictors of outcome, leading to several staging systems for HCC based on clinical parameters. However, the predictive accuracy of clinical staging systems is limited. Recent studies suggested that biological factors may provide additional prognostic information. In particular, gene expression profiling appears to be a promising approach. Study of tumor angiogenesis in HCC reveals that the expression of angiogenic factors such as vascular endothelial growth factor and angiopoietins may also predict prognosis. The elucidation of tumor biology of HCC is of particular importance in the current era of rapid development of anti-cancer molecular targeting agents, which provide hope for an effective systemic therapy for HCC.

A phase I/II trial of chemoembolization for hepatocellular carcinoma using a novel intra-arterial drug-eluting bead.

BACKGROUND & AIMS: To assess the safety and efficacy of transarterial chemoembolization (TACE) using doxorubicin-eluting beads (DEB) for hepatocellular carcinoma (HCC). METHODS: Patients with incurable HCC and Child-Pugh class A cirrhosis were considered eligible for this phase I/II trial. Two courses of TACE using DEB were given at an interval of 2 months, and tumor response was assessed by computerized tomography scan. The phase I trial was a dose-escalating study starting from 25 mg to 150 mg doxorubicin in cohorts of 3 patients. The 150-mg doxorubicin dose was used for the phase II study. Primary end points were treatment-related complications and deaths. Secondary end points included tumor response and pharmacokinetics of doxorubicin. RESULTS: In the phase I study involving 15 patients, no dose-limiting toxicity was observed for up to 150 mg doxorubicin, which was used for 20 patients in the phase II study. The pharmacokinetic study showed a low peak plasma doxorubicin concentration (49.4 +/- 23.7 ng/mL), and no systemic toxicity was observed. The treatment-related complication rate was 11.4%. There was no treatment-related death. Among 30 patients who completed 2 courses of TACE, the partial response rate and the complete response rates were 50% and 0%, respectively, by response evaluation criteria in solid tumors (RECIST) criteria at computerized tomography scan 1 month after the second TACE. By modified RECIST criteria, taking into account the extent of tumor necrosis, 19 (63.3%) patients had a partial response and 2 (6.7%) had a complete response. CONCLUSIONS: This study shows that TACE using DEB is a safe and effective treatment for HCC, supporting a phase III randomized trial to compare this novel treatment with conventional TACE using doxorubicin-Lipiodol emulsion.

From molecular biology to targeted therapies for hepatocellular carcinoma: the future is now.

Hepatocellular carcinoma (HCC) is characterized as a highly chemoresistant cancer with no effective systemic therapy. Despite surgical or locoregional therapies, prognosis remains poor because of high tumor recurrence or tumor progression, and currently there are no well-established effective adjuvant therapies. The molecular biology of carcinogenesis and tumor progression of HCC has been increasingly understood with intense research in recent years. Several important intracellular signaling pathways such as the Ras/Raf/Mek/Erk pathway and PI3k/Akt/mTOR pathway have been recognized, and the role of several growth factors and angiogenic factors such as EGF and VEGF has been confirmed. Effective agents targeting these molecular abnormalities have been developed and widely tested in preclinical studies of HCC cell lines or xenograft models. Several agents have entered clinical trials in HCC patients, and recent data indicated that a multikinase inhibitor targeting Ras kinase and VEGFR-2, sorafenib, is effective in prolonging survival of patients with advanced HCC. The management of advanced HCC is entering the era of molecular targeting therapy, which is of particular significance for HCC in view of the lack of existing effective systemic therapy for this cancer.

Clinical implications of angiogenesis in cancers.

Angiogenesis plays an important role in the growth and progression of cancer. The regulation of tumor angiogenesis depends on a net balance of angiogenic factors and antiangiogenic factors, which are secreted by both tumor cells and host-infiltrating cells. Numerous studies have indicated that assessment of angiogenic activity by either microvessel density or expression of angiogenic factors in cancer can provide prognostic information independent of conventional clinicopathological factors such as tumor staging. Some studies also suggested that assessment of tumor angiogenesis may predict cancer response to chemotherapy or radiotherapy. However, the most important clinical implication of tumor angiogenesis is the development of a novel strategy of anticancer therapy targeting tumor vessels instead of cancer cells. Antiangiogenic therapy aims to inhibit the growth of tumor, and current evidence suggests that it works best in combination with conventional cytotoxic chemotherapy. Recently, a monoclonal antibody against vascular endothelial growth factor, which is one of the most potent angiogenic factors, has been approved for clinical use in colorectal cancer patients after a clinical trial confirmed that combining the antibody with standard chemotherapy regimen could prolong patient survival. The clinical implications of angiogenesis in cancer are reviewed in this article.

Survivin depletion inhibits tumor growth and enhances chemosensitivity in hepatocellular carcinoma.

Survivin is a member of the inhibitor of apoptosis family, which has been suggested to be crucial in the control of cell division and inhibition of apoptosis. Expression of this protein has been observed in transformed cell lines and human tumor tissues, including those from colorectal cancer, but not in terminally differentiated adult tissues. Survivin mRNA expression has frequently been detected in hepatocellular carcinoma (HCC) and its protein expression has been demonstrated to be highly correlated with proliferation index rather than apoptotic index. The present study aimed to analyze the effect of survivin on the tumorigenicity and chemosensitivity of HCC via the establishment of an HCC cell line (PLC/PRF/5) with the stable knockdown of the survivin gene (PLC­k3). This cell line displayed significantly lower rates of survival and proliferation in assays of cell viability and proliferation, respectively, compared with those of the control cell line (PLC­v). In addition, PLC­k3 cells were more sensitive to cisplatin treatment, resulting in S phase arrest. These findings were further confirmed by an in vivo experiment. The data of the present study suggest that survivin is critical in promoting cell proliferation but not in inhibition of apoptosis, and enhances the chemosensitivity of HCC. Thus, the suppression of survivin expression in combination with cisplatin may contribute to the development of more effective treatments for HCC.

Cancer stem cell as a potential therapeutic target in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common human cancers. HCC is a chemoresistant cancer and the current drug therapy has limited efficacy. As a result, the prognosis of HCC patients is generally poor. Recent studies have demonstrated that a subpopulation of cancer cells with stem cell properties, called cancer stem cells (CSCs), are responsible for growth and metastasis of cancer. CSCs characterized by several markers including CD133, CD44, CD90, OV6, Epithelial cell adhesion molecule (EpCAM) and CD13 have been isolated from different human HCC cell lines or specimens. CSCs share many of the signaling pathways found in normal stem cells, such as Wnt, Hedgehog, Notch and Transforming growth factor-beta (TGF-ß) pathways. These pathways are involved in self-renewal, differentiation and survival of CSCs. There is evidence of deregulation of these pathways in HCC CSCs. MicroRNAs also play an important role in regulating signaling pathways in HCC, and recent data suggested an important role of microRNA in CSCs of HCC. Therapeutic targeting of CSCs may provide a novel strategy that is more effective than the current drugs targeting the bulk mature cancer cells in treatment of HCC.

Anti-tumor efficacy of a recombinant human arginase in human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is considered as auxotrophic for arginine and BCT-100, a new recombinant human arginase, has been synthesized for arginine deprivation to inhibit arginine-dependent tumor growth. The aim of the present study was to evaluate the effects of BCT-100 on the inhibition of in vitro cell proliferation of HCC cell lines and in vivo tumor growth. The molecular mechanism involved was also studied. The anti-tumor efficacy of BCT-100 on cell proliferation, cell cycle distribution and cellular apoptosis were determined in human hepatoma HepG2 and PLC/PRF/5 cells. Protein expression in the Wnt/ß-catenin and Akt signaling pathways were analyzed by western blotting. Tumors were also established subcutaneously and BCT-100, in combination with oxaliplatin, was administrated i.p. to study the anti-tumor growth of the drugs. Treatment with BCT-100 was found to inhibit cell proliferation and enhance caspasedependent cellular apoptosis. Cell cycle arrest at S phase was observed. Inhibition of Wnt/ß-catenin and Akt signaling pathways, with a reduction in survivin and XIAP protein expressions, were also observed. Furthermore, combined treatment of BCT-100 and chemotherapy with oxaliplatin demonstrated synergistic inhibiting effect on tumor growth and the overall survival probability was enhanced as compared with BCT-100 or oxaliplatin treatment alone. These preclinical data demonstrate robust anti-tumor activity of BCT100 in HCC, thus providing the basis for its exploitation as a potential therapeutic agent in arginine-driven tumors. The positive effect of testing BCT100 with oxaliplatin in PLC/PRF/5 tumours also supports the rationale of combining BCT-100 and oxaliplatin in the clinical treatment of HCC.

Inhibition of mTOR enhances chemosensitivity in hepatocellular carcinoma.

The present study investigated the effect of mammalian target of rapamycin (mTOR) inhibition on HCC cells in vitro and in vivo, either alone or in combination with cytotoxic agents. In vitro, HCC cell lines were exposed to RAD001, an mTOR inhibitor, either alone or in combination with cisplatin. Alone, RAD001 suppressed cell proliferation in all cell lines tested, but did not induce apoptosis. RAD001 in combination with cisplatin induced a significant increase in the number of apoptotic cells, downregulated the expression of pro-survival molecules, Bcl-2, survivin and cyclinD1, and increased the cleavage of PARP, compared to RAD001 or cisplatin alone. Transfection of p53 into the Hep3B cell line increased the sensitivity of tumor cells to cisplatin. The suppression of HCC tumor growth in vivo was enhanced by RAD001 combined with cisplatin, accompanied by a significant increase in the number of apoptotic cells in tumor tissues. This study demonstrates that inhibition of mTOR suppresses tumor growth and sensitizes tumor cells to chemocytotoxic agents.

Significance of circulating endothelial progenitor cells in hepatocellular carcinoma.

This study evaluated the significance of circulating bone marrow-derived endothelial progenitor cells (EPCs) in patients with hepatocellular carcinoma (HCC), a solid tumor with rich neovasculature. Eighty patients with HCC were recruited for the study, and 16 patients with liver cirrhosis and 14 healthy subjects were also included for comparison. Blood samples were taken before treatment. Total mononuclear cells were isolated from peripheral blood, preplated to eliminate mature circulating endothelial cells, and colony-forming units (CFUs) formed by circulating EPCs were counted. To validate the CFU scores, FACS quantification of EPCs using CD133, VEGFR2, and CD34 as markers was performed in 30 cases. Our study showed significantly higher mean CFU scores in patients with HCC compared to patients with cirrhosis and healthy controls (P = .001 and .009, respectively). Furthermore, the CFU scores of patients with HCC positively correlated with levels of serum alpha-fetoprotein (r = .303, P = .017), plasma VEGF (r = .242, P = .035), and plasma interleukin-8 (IL-8) (r = .258, P = .025). Patients with unresectable HCC had higher CFU scores than patients with resectable tumors (P = .027). Furthermore, for those who underwent curative surgery, higher preoperative CFU scores were observed in patients with recurrence within 1 year compared with those who were disease-free after 1 year (P = .013). In conclusion, higher circulating levels of EPCs are seen in patients with advanced unresectable HCC as compared to patients with resectable HCC or those with liver cirrhosis. Our evidence supports the potential use of circulating level of EPCs as a prognostic marker in patients with HCC.