Cyclin E overexpression responsible for growth of human hepatic tumors with p21WAF1/CIP1/SDI1

Transplantation of melanocytes obtained from the skin ameliorates apomorphine-induced abnormal behavior in rodent hemi-parkinsonian models

Tyrosinase, which catalyzes both the hydroxylation of tyrosine and consequent oxidation of L-DOPA to form melanin in melanocytes, is also expressed in the brain, and oxidizes L-DOPA and dopamine. Replacement of dopamine synthesis by tyrosinase was reported in tyrosine hydroxylase null mice. To examine the potential benefits of autograft cell transplantation for patients with Parkinson’s disease, tyrosinase-producing cells including melanocytes, were transplanted into the striatum of hemi-parkinsonian model rats or mice lesioned with 6-hydroxydopamine. Marked improvement in apomorphine-induced rotation was noted at day 40 after intrastriatal melanoma cell transplantation. Transplantation of tyrosinase cDNA-transfected hepatoma cells, which constitutively produce L-DOPA, resulted in marked amelioration of the asymmetric apomorphine-induced rotation in hemi-parkinsonian mice and the effect was present up to 2 months. Moreover, parkinsonian mice transplanted with melanocytes from the back skin of black newborn mice, but not from albino mice, showed marked improvement in the apomorphine-induced rotation behavior up to 3 months after the transplantation. Dopamine-positive signals were seen around the surviving transplants in these experiments. Taken together with previous studies showing dopamine synthesis and metabolism by tyrosinase, these results highlight therapeutic potential of intrastriatal autograft cell transplantation of melanocytes in patients with Parkinson’s disease.

Aminoimidazole carboxamide ribonucleotide (AICAR) inhibits the growth of retinoblastoma in vivo by decreasing angiogenesis and inducing apoptosis

5-Aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR), an analog of AMP is widely used as an activator of AMP-kinase (AMPK), a protein that regulates the responses of the cell to energy change. Recently, we showed that AICAR-induced AMPK activation inhibits the growth of retinoblastoma cells in vitro by decreasing cyclins and by inducing apoptosis and S-phase arrest. In this study, we investigated the effects of AMPK activator AICAR on the growth of retinoblastoma in vivo. Intraperitoneal injection of AICAR resulted in 48% growth inhibition of Y79 retinoblastoma cell tumors in mice. Tumors isolated from mice treated with AICAR had decreased expression of Ki67 and increased apoptotic cells (TUNEL positive) compared with the control. In addition, AICAR treatment suppressed significantly tumor vessel density and macrophage infiltration. We also showed that AICAR administration resulted in AMPK activation and mTOR pathway inhibition. Paradoxically observed down-regulation of p21, which indicates that p21 may have a novel function of an oncogene in retinoblastoma tumor. Our results indicate that AICAR treatment inhibited the growth of retinoblastoma tumor in vivo via AMPK/mTORC1 pathway and by apoptogenic, anti-proliferative, anti-angiogenesis mechanism. AICAR is a promising novel non-chemotherapeutic drug that may be effective as an adjuvant in treating Retinoblastoma.

RNAi-mediated silencing of the Cyclin E gene inhibits the proliferation and invasion of HepG2, SMMC-7721 and BEL-7402 cells

AIM: To observe the effect of RNAi-mediated silencing of the Cyclin E gene on the proliferation and invasion of HepG2, SMMC-7721 and BEL-7402 cells.

METHODS: Two vectors carrying siRNA targeting the Cyclin E gene were constructed and transfected into HepG2, SMMC-7721 and BEL-7402 cells. The mRNA and protein expression of Cyclin E were measured by RT-PCR and Western blot, respectively. CCK-8 assay and colony formation assay were employed to assess the proliferation and colony-forming ability of transfected HepG2, SMMC-7721 and BEL-7402. Flow cytometry (FCM) and transwell migration assay were used to evaluate cell cycle progression and migration of transfected cells.

RESULTS: Compared to the blank control group and negative control group, the expression of Cyclin E mRNA and protein was significantly decreased, the proliferation, colony-forming ability, and migration were suppressed significantly, and cell cycle was arrested in G₀/G₁ phase in two experimental groups.

CONCLUSION: Down-regulation of Cyclin E expression significantly inhibits the proliferation and migration of HepG2, SMMC-7721 and BEL-7402 cells.

Expression and functional role of a transcribed noncoding RNA with an ultraconserved element in hepatocellular carcinoma

Although expression of non-protein-coding RNA (ncRNA) can be altered in human cancers, their functional relevance is unknown. Ultraconserved regions are noncoding genomic segments that are 100% conserved across humans, mice, and rats. Conservation of gene sequences across species may indicate an essential functional role, and therefore we evaluated the expression of ultraconserved RNAs (ucRNA) in hepatocellular cancer (HCC). The global expression of ucRNAs was analyzed with a custom microarray. Expression was verified in cell lines by real-time PCR or in tissues by in situ hybridization using tissue microarrays. Cellular ucRNA expression was modulated with siRNAs, and the effects on global gene expression and growth of human and murine HCC cells were evaluated. Fifty-six ucRNAs were aberrantly expressed in HepG2 cells compared with nonmalignant hepatocytes. Among these ucRNAs, the greatest change was noted for ultraconserved element 338 (uc.338), which was dramatically increased in human HCC compared with noncancerous adjacent tissues. Although uc.338 is partially located within the poly(rC) binding protein 2 (PCBP2) gene, the transcribed ncRNA encoding uc.338 is expressed independently of PCBP2 and was cloned as a 590-bp RNA gene, termed TUC338. Functional gene annotation analysis indicated predominant effects on genes involved in cell growth. These effects were experimentally demonstrated in both human and murine cells. siRNA to TUC338 decreased both anchorage-dependent and anchorage-independent growth of HCC cells. These studies identify a critical role for TUC338 in regulation of transformed cell growth and of transcribed ultraconserved ncRNA as a unique class of genes involved in the pathobiology of HCC.

Down-regulation of tumor suppressor A kinase anchor protein 12 in human hepatocarcinogenesis by epigenetic mechanisms

The A kinase anchor protein 12 (AKAP12) is a central mediator of protein kinase A and protein kinase C signaling. Although AKAP12 has been described to act as a tumor suppressor and its expression is frequently down-regulated in several human malignancies, the underlying molecular mechanisms responsible for the AKAP12 reduction are poorly understood. We therefore analyzed the expression of AKAP12 and its genetic and epigenetic regulatory mechanisms in human hepatocarcinogenesis. Based on tissue microarray analyses (n = 388) and western immunoblotting, we observed a significant reduction of AKAP12 in cirrhotic liver (CL), premalignant lesions (DN), and hepatocellular carcinomas (HCCs) compared to histologically normal liver specimens (NL). Analyses of array comparative genomic hybridization data (aCGH) from human HCCs revealed chromosomal losses of AKAP12 in 36% of cases but suggested additional mechanisms underlying the observed reduction of AKAP12 expression in hepatocarcinogenesis. Quantitative methylation analysis by MassARRAY of NL, CL, DN, and HCC tissues, as well as of various tumorigenic and nontumorigenic liver cell lines revealed specific hypermethylation of the AKAP12α promoter but not of the AKAP12β promoter in HCC specimens and in HCC cell lines. Consequently, restoration experiments performed with 5-aza-2'deoxycytidine drastically increased AKAP12α mRNA levels in a HCC cell line (AKN1) paralleled by AKAP12α promoter demethylation. As hypermethylation is not observed in CL and DN, we investigated microRNA-mediated posttranscriptional regulation as an additional mechanism to explain reduced AKAP12 expression. We found that miR-183 and miR-186 are up-regulated in CL and DN and are able to target AKAP12.

CONCLUSION

In addition to genetic alterations, epigenetic mechanisms are responsible for the reduction of the tumor suppressor gene AKAP12 in human hepatocarcinogenesis.

Targeting heat shock protein 90 with non-quinone inhibitors: a novel chemotherapeutic approach in human hepatocellular carcinoma

The inhibition of heat shock protein 90 (Hsp90) has emerged as a promising antineoplastic strategy in diverse human malignancies. Hsp90 has been predicted to be involved in hepatocellular carcinoma (HCC) development; however, its role in hepatocarcinogenesis remains elusive. Using chemically distinctive Hsp90 inhibitors, we show that Hsp90 capacitates the aberrant expression and activity of crucial hepatocarcinogenesis-driving factors (e.g., insulin-like growth factor receptor 1, hepatocyte growth factor receptor, protein kinase B, v-raf-1 murine leukemia viral oncogene homolog 1, and cyclin-dependent kinase 4). In vitro, Hsp90 inhibition with both geldanamycin analogs (17-allylamino-17-desmethoxygeldanamycin (17-AAG) and 17-dimethylaminoethylamino-17-desmethoxygeldanamycin (17-DMAG)) and the non-quinone compound 8-(6-iodobenzo[d][1,3]dioxol-5-ylthio)-9-(3-(isopropylamino)propyl)-9H-purin-6-amine (PU-H71) reduced the viability of various HCC cell lines, induced the simultaneous degradation of numerous hepatocarcinogenic factors, and caused substantial cell cycle arrest and apoptosis. In contrast, nontumorigenic hepatocytes were less susceptible to Hsp90 inhibition. Because conventional geldanamycin-derivate Hsp90 inhibitors induce dose-limiting liver toxicity, we tested whether novel Hsp90 inhibitors lacking the benzoquinone moiety, which has been deemed responsible for hepatotoxicity, can elicit antineoplastic activity without causing significant liver damage. In HCC xenograft mouse models, PU-H71 was retained in tumors at pharmacologically relevant concentrations while being rapidly cleared from nontumorous liver. PU-H71 showed potent and prolonged in vivo Hsp90 inhibitory activity and reduced tumor growth without causing toxicity.

CONCLUSION

Hsp90 constitutes a promising therapeutic target in HCC. Non-quinone Hsp90 inhibitors exhibit tumor-specific accumulation and exert potent antineoplastic activity without causing significant hepatotoxicity.

Abnormal expression pattern of cyclin E in tumour cells

The expression pattern of cyclin E during the cell cycle was studied in normal and tumour cells in culture and in tumour biopsies. This pattern was found to be abnormal in tumour cells. A triple immunostaining protocol, digital microscopy and image analysis were used to find the position of the individual cells in the cell cycle and to measure the nuclear cyclin E levels. In normal cells, the number of cyclin E-positive cells decreased rapidly when the cells entered the S-phase. In the tumour cell lines, cyclin E was not downregulated in early S-phase, as in normal cells. Instead the number of cyclin E-positive cells remained high throughout S-phase, and the cyclin E staining intensity per cell often increased during S-phase. In about half of the analysed tumour cell lines, many cells stained positive for cyclin E even in the G(2)-phase. This abnormal expression over the cell cycle of cyclin E was also found in tumour biopsies from cervical, breast and prostatic carcinomas, even though it varied greatly between individual tumours. In some tumours, the expression pattern of cyclin E was similar to that of normal cells in culture, whereas in others high cyclin E levels could be seen in S-phase cells, as in the transformed cell lines. A high percentage of cells expressing cyclin E during S- or G(2)-phase was found to be related to poor outcome (p < 0.025) in a small group of cervical carcinoma patients (n = 12).