Reassignment of the human ARH9 RAS-related gene to chromosome 1p13-p21

Role of RhoC in cancer cell migration

Migration is one of the five major behaviors of cells. Although RhoC—a classic member of the Rho gene family—was first identified in 1985, functional RhoC data have only been widely reported in recent years. Cell migration involves highly complex signaling mechanisms, in which RhoC plays an essential role. Cell migration regulated by RhoC—of which the most well-known function is its role in cancer metastasis—has been widely reported in breast, gastric, colon, bladder, prostate, lung, pancreatic, liver, and other cancers. Our review describes the role of RhoC in various types of cell migration. The classic two-dimensional cell migration cycle constitutes cell polarization, adhesion regulation, cell contraction and tail retraction, most of which are modulated by RhoC. In the three-dimensional cell migration model, amoeboid migration is the most classic and well-studied model. Here, RhoC modulates the formation of membrane vesicles by regulating myosin II, thereby affecting the rate and persistence of amoeba-like migration. To the best of our knowledge, this review is the first to describe the role of RhoC in all cell migration processes. We believe that understanding the detail of RhoC-regulated migration processes will help us better comprehend the mechanism of cancer metastasis. This will contribute to the study of anti-metastatic treatment approaches, aiding in the identification of new intervention targets for therapeutic or genetic transformational purposes.

The Effect of Ras Homolog C/Rho-Associated Coiled-Protein Kinase (Rho/ROCK) Signaling Pathways on Proliferation and Apoptosis of Human Myeloma Cells

BACKGROUND The aim of this study was to explore the impact of Ras homolog C/Rho-associated coiled-protein kinase (Rho/ROCK) signaling pathways intervention on biological characteristics of the human multiple myeloma cell lines RPMI-8226 and U266 cells, and to investigate the expression of RhoC, ROCK1, and ROCK2 in RPMI-8226 and U266 cells. MATERIAL AND METHODS RPMI8226 and U266 cell lines were treated by 5-aza-2-deoxycytidine (5-Aza-Dc), trichostatin A (TSA), RhoA inhibitor CCG-1423, Rac1 inhibitor NSC23766, and ROCK inhibitor fasudil. Cell proliferation was examined by Cell Counting Kit-8 (CCK-8) assay and clone formation. Cell apoptosis was examined by flow cytometry and TUNEL assay. The mRNA and protein expressions of RhoC, ROCK1, and ROCK2 were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot, respectively. RESULTS CCG-1423, NSC23766, and fasudil could significantly inhibit the proliferation of RPMI8226 and U266 cells. The inhibitory effect was dose- and time-dependent within a certain concentration range (P<0.05). After treatment with CCG-1423, NSC23766, and fasudil for 24 hours, the apoptosis rates of RPMI8226 and U266 cells were significantly higher than those of the control group, which were dose-dependent (P<0.05). Compared with the control group, the mRNA and protein expressions of RhoC, ROCK1, and ROCK2 in RPMI8226 and U266 cells were significantly decreased with single 5-Aza-Dc or TSA treatment. However, the effects were obviously stronger after combined treatment of 5-Aza-CdR and TSA (P<0.05). CONCLUSIONS We found that 5-Aza-Dc and TSA can effectively decrease the mRNA and protein expressions of RhoC, ROCK1, and ROCK2. Furthermore, Rho and ROCK inhibitors significantly inhibit cell growth and induce cell apoptosis in the human multiple myeloma cell lines RPMI-8226 and U266.

RhoC, vascular endothelial growth factor and microvascular density in esophageal squamous cell carcinoma

AIM: To investigate the expression of Ras homolog (Rho)C, vascular endothelial growth factor (VEGF) and CD105 in esophageal squamous cell carcinoma.

METHODS: Semi-quantitative reverse transcriptase polymerase chain reaction, in situ hybridization and immunohistochemical streptavidin-biotin- peroxidase methods were used to detect expression of RhoC mRNA and protein, and VEGF protein in 62 cases with esophageal squamous cell carcinoma, 31 cases with adjacent atypical hyperplastic tissues, and 62 cases with normal esophageal mucosa. CD105 antibody labeling was used to measure microvascular density. Expression levels were compared according to clinicopathologic and patient parameters.

RESULTS: Expression of RhoC mRNA showed a positive correlation with the protein level in esophageal squamous cell carcinoma, as well as with VEGF protein levels. RhoC mRNA expression was mainly located within the cytoplasm of the tumor cells, appearing as blue to purple particles by in situ hybridization. The differences in RhoC mRNA expression in esophageal squamous cell carcinoma, adjacent atypical hyperplasia and normal esophageal mucosa were significant (P < 0.05). The relative expression of RhoC mRNA in cancer tissues with lymph node metastasis was significantly higher than in the tissues without lymph node metastasis (P < 0.05). VEGF protein expression was consistent with microvascular density (t = 25.52, P < 0.05). Positive expression of VEGF protein in esophageal squamous cell carcinoma of different histologic gradings did not differ significantly. Positive expression of VEGF protein in carcinoma tissues with deep infiltration was significantly higher than in tissues with only superficial infiltration (P < 0.05). The positive expression of VEGF protein in cancer tissues with lymph node metastasis was significantly higher than in the tissues without lymph node metastasis (P < 0.05).

CONCLUSION: RhoC protein may upregulate VEGF expression, thereby promoting tumor angiogenesis. RhoC mRNA and protein expression was correlated with metastasis.

Establishment and preliminary identification of a mouse hepatocellular carcinoma cell line with high metastatic potential to the lung

AIM: To establish a mouse H22 hepatocellular carcinoma cell line with high metastatic potential to the lung to provide a suitable model for the study of metastasis-related molecular mechanisms.

METHODS: H22 hepatocellular ascitic tumor cells (M0) were inoculated into mice via the vena caudalis, and pulmonary metastatic lesions were harvested to refabricate ascitic tumor cells. The obtained cells were inoculated into mice again via the vena caudalis to form pulmonary metastatic nodes. The same procedure was repeated four times to obtain a cell line with high metastatic potential to the lung (M4). The metastatic ability in vivo, proliferation capability in vitro, cell division index, and cell cycle distribution of M4 cells were measured. The mRNA expression of the RhoC gene in M4 cells was detected by RT-PCR.

RESULTS: After injection via the vena caudalis, M4 cells produced pulmonary metastasis earlier and formed more and larger nodes. Compared to M0 cells, the doubling time of M4 cells was shortened by 38.73%; cell division index significantly increased (P = 0.014); and the proportion of cells in S phase was significantly higher (P = 0.022). The number of chromatosomes was comparable between M0 and M4 cells, while heteromorphism was more obvious in M4 cells. The mRNA expression of the RhoC gene was significantly higher in M4 cells than in M0 cells (1.011 ± 0.163 vs 0.486 ± 0.045, P = 0.0029).

CONCLUSION: A mouse hepatocellular carcinoma cell line with high metastatic potential to the lung has been established successfully.

Significance of RhoC mRNA expression in esophageal squamous cell carcinoma

AIM: To investigate the expression of RhoC mRNA in esophageal squamous cell carcinoma (ESCC) and to explore its correlation with the development and progression of ESCC.

METHODS: Semi-quantitative RT-PCR was used to detect the relative expression levels of RhoC mRNA in 62 ESCC specimens, 31 tumor-adjacent atypical hyperplastic epithelial specimens and 62 normal esophageal epithelial specimens. The distribution of RhoC transcripts in ESCC was determined by in situ hybridization.

RESULTS: The mRNA expression of RhoC was closely correlated with tumor grade, infiltration and lymph node metastasis in ESCC (all P < 0.05). The expression intensity of RhoC mRNA in carcinoma, adjacent atypical hyperplasia epithelium and normal esophageal epithelium were 0.902 ± 0.119, 0. 731 ± 0.065 and 0.653 ± 0.069, respectively, with a significant difference among the three groups (P < 0.01). In situ hybridization analysis demonstrated that RhoC transcripts were detected in the cytoplasm of cells. The positive rates of RhoC mRNA expression in carcinoma, tumor-adjacent atypical hyperplasia epithelium and normal esophageal epithelium were 80.6% (50/62), 32.3% (10/31) and 21.0% (13/62), respectively, with a significant difference among the three groups (P < 0.01). RT-PCR results were consistent with those obtained by in situ hybridization.

CONCLUSION: The mRNA expression of RhoC in ESCC increases significantly and is closely correlated with tumor biological behavior, which suggests that RhoC overexpression is closed associated with the pathogenesis of ESCC. RhoC may be a new auxiliary parameter for early diagnosis and prognostic prediction for ESCC.

Human monocyte x mouse melanoma fusion hybrids express human gene

Artificial fusion of human monocyte with Cloudman S91 mouse melanoma cells resulted in hybrids that showed increased motility in vitro, enhanced metastatic potential in vivo, and also tended to be super melanotic (Rachkovsky et al., Clin. Exp. Metastasis 16 (1998) 299). However, no gene derived from monocytes has been shown to be expressed in these hybrids until now. Similar observations have also been noted in hybrids originating from mouse macrophage and mouse melanoma cells. Having the advantage of species differences in mouse x human hybrids, we are able, this time, to show by RT-PCR that some genes specific to the human genome are expressed in these hybrids, indicating that not only is the genomic DNA from parental monocytes integrated in the hybrids but also some genes are being expressed. This observation may lead us to find contributory genes from monocyte and/or macrophage that are responsible for modulating the genotypes and hence the phenotypes in the hybrids.

Genomic structure and promoter characterization of an imprinted tumor suppressor gene ARHI

We have recently identified a maternally imprinted tumor suppressor gene, ARHI (aplysia ras homolog I), the expression of which is lost in ovarian and breast cancers. We have now characterized the genomic structure of the gene including its promoter and the methylation status of its upstream CpG islands. The ARHI gene spans approximately 8 kb containing two exons and one intron. Exon 1 contains 81 non-translated nucleotides, connected to exon 2 with a 3.2-kb intron. The entire protein-coding region is located within exon 2 and encodes a 229-residue small GTP-binding protein belonging to the Ras superfamily. Genomic structure analysis has identified three potential CpG islands. Two of them (CpG island I and II) are located within the promoter and adjacent exon 1 of the ARHI gene. Aberrant methylation of these CpG islands has been detected in breast cancer cells but not in normal epithelial cells, supporting the possibility that appropriate methylation status of the CpG islands in the promoter region may play a role in the downregulation of ARHI gene expression. A TATA box is found 27 bp upstream of the transcription start site associated with several putative transcription factor binding sites. Transient transfection with nested deletion constructs of the 2-kb ARHI promoter regions fused to a luciferase reporter indicated a 121-bp sequence upstream of the transcription initiation site is required for basal promoter activity. Interestingly, this is the region where lower promoter activity has been observed in cancer cells than in normal cells.

The GTP-binding protein Rho

RhoA, RhoB and RhoC are three closely related proteins, and are members of the Ras super-family of small GTP-binding proteins. They bind and hydrolyse GTP, and are active in the GTP-bound form. Their activity in cells is regulated by exchange factors, GTPase activating proteins and guanine nucleotide dissociation inhibitors. Several potential downstream target proteins for Rho proteins have been identified, including protein kinases and adaptor-type proteins. Rho proteins regulate actin cytoskeletal organization; for example in fibroblasts RhoA induces the formation of actin stress fibres. Rho proteins are also involved in regulating secretion, pinocytosis and clathrin coat-mediated endocytosis, transcriptional activation and stimulation of DNA synthesis. In addition, there is evidence that Rho proteins can play a role in cell transformation, and thus Rho proteins or components of their signalling pathways may be potential targets for the development of anti-cancer therapies.

Structure and chromosomal assignment to 22q12 and 17qter of the ras-related Rac2 and Rac3 human genes

Members of the Rho/Rac/Cdc42Hs family of GTPases have been shown to participate in many aspects of the signaling of cell growth and differentiation. Although the biochemical properties of these GTPases have been extensively studied, very little is known about the structure of the corresponding genes. To gain insight on the evolution of the Rho family, we were interested in studying the genomic structure of several members. We report here the structure and the localization to 22q12 of the human Rac2 gene, as well as the localization to 17qter of Rac3, a new member closely related to Rac1 and Rac2. Unlike the structure of its closest relative ARH-G gene, which contains a single intron, Rac2 is made of at least 7 exons, spanning over 18 kb of DNA. Comparison of gene structure and exonic borders suggests that the emergence of the whole superfamily took place early during evolution.

Involvement of the ALL-1 gene in a solid tumor

Translocations involving chromosome band 11q23, found in 5-10% of human acute leukemias, disrupt the ALL-1 gene. This gene is fused by reciprocal translocation with a variety of other genes in acute lymphoblastic and myelogenous leukemias, and it undergoes self-fusion in acute myeloid leukemias with normal karyotype or trisomy 11. Here we report an alteration of the ALL-1 gene in a gastric carcinoma cell line (Mgc80-3). Characterization of this rearrangement revealed a three-way complex translocation, involving chromosomes 1 and 11, resulting in a partial duplication of the ALL-1 gene. Sequencing of reverse transcription-PCR products and Northern blot analysis showed that only the partially duplicated ALL-1 gene was transcribed, producing an mRNA with exon 8 fused to exon 2. This report of ALL-1 gene rearrangement in a solid tumor suggests that ALL-1 plays a role in the pathogenesis of some solid malignancies. The absence of the normal transcript in this cell line, in association with the loss-of-heterozygosity studies on chromosome 11q23 seen in solid tumors, suggests that ALL-1 is involved in tumorigenesis by a loss-of-function mechanism.