Lattice-Gas Cellular Automaton Models for Biology: From Fluids to Cells

Lattice-gas cellular automaton (LGCA) and lattice Boltzmann (LB) models are promising models for studying emergent behaviour of transport and interaction processes in biological systems. In this chapter, we will emphasise the use of LGCA/LB models and the derivation and analysis of LGCA models ranging from the classical example dynamics of fluid flow to clotting phenomena in cerebral aneurysms and the invasion of tumour cells.     

Cellular Migration and Invasion Uncoupled: Increased Migration Is Not an Inexorable Consequence of Epithelial-to-Mesenchymal Transition

Metastatic dissemination requires carcinoma cells to detach from the primary tumor and invade through the basement membrane. To acquire these characteristics, epithelial tumor cells undergo epithelial-to-mesenchymal transitions (EMT), whereby cells lose polarity and E-cadherin-mediated cell-cell adhesion. Post-EMT cells have also been shown, or assumed, to be more migratory; however, there have been contradictory reports on an immortalized human mammary epithelial cell line (HMLE) that underwent EMT. In the context of carcinoma-associated EMT, it is not yet clear whether the change in migration and invasion must be positively correlated during EMT or whether enhanced migration is a necessary consequence of having undergone EMT. Here, we report that pre-EMT rat prostate cancer (PC) and HMLE cells are more migratory than their post-EMT counterparts. To determine a mechanism for increased epithelial cell migration, gene expression analysis was performed and revealed an increase in epidermal growth factor receptor (EGFR) expression in pre-EMT cells. Indeed, inhibition of EGFR in PC epithelial cells slowed migration. Importantly, while post-EMT PC and HMLE cell lines are less migratory, both remain invasive in vitro and, for PC cells, in vivo. Our study demonstrates that enhanced migration is not a phenotypic requirement of EMT, and migration and invasion can be uncoupled during carcinoma-associated EMT.     

干扰OVA66基因表达对移植瘤生物学功能的影响

目的探讨干扰OVA66基因表达对移植瘤细胞生物学功能的影响。方法采用脂质体法,以重组的pSUPER-shRNA-OVA66和空载体转染HeLa细胞获得稳定表达细胞株,经RT-PCR和Western blot鉴定OVA66基因的表达。将两组细胞接种于BALB／cnu／nu裸鼠的前肢腋下,连续观察干扰OVA66表达对肿瘤的生长影响。并于接种4周后,应用RT-PCR,免疫组化、免疫荧光等方法检测移植瘤细胞中OVA66的蛋白表达。组织病理分析肿瘤细胞生长和转移的特征。结果经检测pSUPER-shRNA-OVA66能有效抑制目的基因的表达。比较两组荷瘤小鼠中肿瘤的生长曲线发现,OVA66实验组的肿瘤生长速度明显低于对照组,并且肿瘤细胞体内转移和浸润能力显著降低。结论干扰OVA66基因和蛋白表达,可以抑制肿瘤细胞的生长,浸润和侵袭能力。     

Inhibition of IGF-1-Mediated Cellular Migration and Invasion by Migracin A in Ovarian Clear Cell Carcinoma Cells

Previously we isolated migracin A from a Streptomyces culture filtrate as an inhibitor of cancer cell migration. In the present research, we found that migracin A inhibited migration and invasion of ovarian clear cell carcinoma ES-2 cells. In the course of our mechanistic study, migracin A was shown to enhance vasohibin-1 expression in an angiogenesis array. We also confirmed that it increased the mRNA expression of this protein. Moreover, overexpression of vasohibin-1 lowered the migration but not the invasion of ES-2 cells. Then, we looked for another target protein employing a motility array, and found that migracin A lowered the IGF-1 expression. Knockdown of IGF-1 by siRNA decreased the migration and invasion of ES-2 cells. Migracin A also decreased Akt phosphorylation involved in the downstream signaling. Crosstalk analysis indicated that overexpression of vasohibin-1 decreased the IGF-1 expression. On the other hand, it showed no direct anticancer activity in terms of the ES-2 growth in agar. Migracin A inhibited the migration and IGF-1 expression in not only ES-2 but also another ovarian clear cell carcinoma JHOC-5 cells. In addition, it also inhibited capillary tube formation of human umbilical vein endothelial cells. Since its cytotoxicity is very low, migracin A may be a candidate for an anti-metastasis agent not exhibiting prominent toxicity.     

A Cellular Automaton Model for Tumor Dormancy: Emergence of a Proliferative Switch

Malignant cancers that lead to fatal outcomes for patients may remain dormant for very long periods of time. Although individual mechanisms such as cellular dormancy, angiogenic dormancy and immunosurveillance have been proposed, a comprehensive understanding of cancer dormancy and the “switch” from a dormant to a proliferative state still needs to be strengthened from both a basic and clinical point of view. Computational modeling enables one to explore a variety of scenarios for possible but realistic microscopic dormancy mechanisms and their predicted outcomes. The aim of this paper is to devise such a predictive computational model of dormancy with an emergent “switch” behavior. Specifically, we generalize a previous cellular automaton (CA) model for proliferative growth of solid tumor that now incorporates a variety of cell-level tumor-host interactions and different mechanisms for tumor dormancy, for example the effects of the immune system. Our new CA rules induce a natural “competition” between the tumor and tumor suppression factors in the microenvironment. This competition either results in a “stalemate” for a period of time in which the tumor either eventually wins (spontaneously emerges) or is eradicated; or it leads to a situation in which the tumor is eradicated before such a “stalemate” could ever develop. We also predict that if the number of actively dividing cells within the proliferative rim of the tumor reaches a critical, yet low level, the dormant tumor has a high probability to resume rapid growth. Our findings may shed light on the fundamental understanding of cancer dormancy.     

Trypanosoma cruzi: Mutations in the 3' untranslated region of calmodulin gene are specific for lineages T. cruzi I, T. cruzi II, and the Zymodeme III isolates

Populations of Trypanosoma cruzi can be clustered in two main phylogenetic lineages, T. cruzi I and T. cruzi II and a third group denominated Zymodeme III (ZIII) has been described. Using 23 isolates representing the two major T. cruzi groups and the Zymodeme III, the 3' untranslated region (3'UTR) of the calmodulin gene was analyzed. Several mutations located on a 330 bp segment of this 3'UTR were observed, among which three important insertion/deletion events, namely (1) a dinucleotide AG present only in ZIII isolates; (2) a 13 bases purine block missing only in ZIII; and (3) a five base GT block in T. cruzi II. Minimum free energy dot plots show that T. cruzi I and T. cruzi ZIII exhibit similar patterns of optimal and sub-optimal folding of this segment. These mutations in 3'UTR of calmodulin raise the possibility that T. cruzi I and ZIII group are sharing common functional routes.     

RNAi干扰Ska2对H1299细胞增殖、迁移及侵袭能力的影响

Ska2（spindle and kinetochore associated complex subunit2）,又称FAM33A（family with sequence similarity33,member A）,是新近发现的一个与细胞周期调控和肿瘤发生发展紧密相关的基瓯且与该团队前期发现的新基NPRR11（proline rich 11）共享一个双向启动子。但是,Ska2在肺癌中的具体作用和分子机制仍不清楚。该研究选用肺癌细胞系H1299,采用RNAi技术构建Ska2基因沉默的稳定细胞株,并进行了细胞表型和潜在分子机制分析。RT-PCR和Western blot结果表明,Ska2在mRNA和蛋白质水平上的表达均被有效抑制。细胞增殖、细胞迁移和侵袭实验结果表明,与对照细胞相比,Ska2基因沉默稳定细胞株的细胞增殖能力、细胞迁移和侵袭能力均显著降低。此外,Ska2基因被沉默后,CCNA1基因的表达显著下调。该研究的结果提示,Ska2与其对侧基因PRR11的功能高度相关,可能与PRR11共同参与肺癌细胞增殖、迁移和侵袭行为的调节。     

Effects of Osthole on Migration and Invasion in Breast Cancer Cells

Osthole, a natural coumarin derivative, is extracted from the fruit of Cnidium monnieri Cusson. Breast cancer is one of the most commonly diagnosed cancers and the leading cause of death in women. Recent studies have shown that Osthole has anti-tumor activity. However, the effects of Osthole on the migration and invasion of cancer cells have not yet been reported. Here, we found that Osthole is effective in inhibiting the migration and invasion of breast cancer cells by wound healing and transwell assays. Luciferase and zymography assays revealed that Osthole effectively inhibits matrix metalloproteinase-2 promoter and enzyme activity, which might be one of the causes that lead to the inhibition of migration and invasion by Osthole. This is the first report on the inhibitory function of Osthole in migration and invasion in breast cancer cells. Our findings indicate a need for further evaluation of Osthole in breast cancer chemotherapy and chemoprevention.     

Computational Models Reveal a Passive Mechanism for Cell Migration in the Crypt

Cell migration in the intestinal crypt is essential for the regular renewal of the epithelium, and the continued upward movement of cells is a key characteristic of healthy crypt dynamics. However, the driving force behind this migration is unknown. Possibilities include mitotic pressure, active movement driven by motility cues, or negative pressure arising from cell loss at the crypt collar. It is possible that a combination of factors together coordinate migration. Here, three different computational models are used to provide insight into the mechanisms that underpin cell movement in the crypt, by examining the consequence of eliminating cell division on cell movement. Computational simulations agree with existing experimental results, confirming that migration can continue in the absence of mitosis. Importantly, however, simulations allow us to infer mechanisms that are sufficient to generate cell movement, which is not possible through experimental observation alone. The results produced by the three models agree and suggest that cell loss due to apoptosis and extrusion at the crypt collar relieves cell compression below, allowing cells to expand and move upwards. This finding suggests that future experiments should focus on the role of apoptosis and cell extrusion in controlling cell migration in the crypt.     

Transferrin Promotes Endothelial Cell Migration and Invasion: Implication in Cartilage Neovascularization

During endochondral bone formation, avascular cartilage differentiates to hypertrophic cartilage that then undergoes erosion and vascularization leading to bone deposition. Resting cartilage produces inhibitors of angiogenesis, shifting to production of angiogenic stimulators in hypertrophic cartilage. A major protein synthesized by hypertrophic cartilage both in vivo and in vitro is transferrin. Here we show that transferrin is a major angiogenic molecule released by hypertrophic cartilage. Endothelial cell migration and invasion is stimulated by transferrins from a number of different sources, including hypertrophic cartilage. Checkerboard analysis demonstrates that transferrin is a chemotactic and chemokinetic molecule. Chondrocyte-conditioned media show similar properties. Polyclonal anti-transferrin antibodies completely block endothelial cell migration and invasion induced by purified transferrin and inhibit the activity produced by hypertrophic chondrocytes by 50–70% as compared with controls. Function-blocking mAbs directed against the transferrin receptor similarly reduce the endothelial migratory response. Chondrocytes differentiating in the presence of serum produce transferrin, whereas those that differentiate in the absence of serum do not. Conditioned media from differentiated chondrocytes not producing transferrin have only 30% of the endothelial cell migratory activity of parallel cultures that synthesize transferrin.

The angiogenic activity of transferrins was confirmed by in vivo assays on chicken egg chorioallantoic membrane, showing promotion of neovascularization by transferrins purified from different sources including conditioned culture medium.

Based on the above results, we suggest that transferrin is a major angiogenic molecule produced by hypertrophic chondrocytes during endochondral bone formation.

     

microRNA-124 Inhibits Migration and Invasion by Down-Regulating ROCK1 in Glioma

Background

The extraordinary invasive capability is a major cause of treatment failure and tumor recurrence in glioma, however, the molecular and cellular mechanisms governing glioma invasion remain poorly understood. Evidence in other cell systems has implicated the regulatory role of microRNA in cell motility and invasion, which promotes us to investigate the biological functions of miR-124 in glioma in this regard.

Results

We have found that miR-124 is dramatically downregulated in clinical specimen of glioma and is negatively correlated with the tumor pathological grading in the current study. The cells transfected by miR-124 expression vector have demonstrated retarded cell mobility. Using a bioinformatics analysis approach, rho-associated coiled-coil containing protein kinase 1 (ROCK1), a well-known cell mobility-related gene, has been identified as the target of miR-124. A dual-luciferase reporter assay was used to confirm that miR-124 targeted directly the 3′UTR of ROCK1 gene and repressed the ROCK1 expression in U87MG human glioma cell line. Furthermore, experiments have shown that the decreased cell mobility was due to the actin cytoskeleton rearrangements and the reduced cell surface ruffle in U87MG glioma cells. These results are similar to the cellular responses of U87MG glioma cells to the treatment of Y-27632, an inhibitor of ROCK protein. Moreover, a constitutively active ROCK1 in miR-124 over-expressed glioma cells reversed the effects of miR-124. Our results revealed a novel mechanism that miR-124 inhibits glioma cells migration and invasion via ROCK1 downregulation.

Conclusions

These results suggest that miR-124 may function as anti-migration and anti-invasion influence in glioma and provides a potential approach for developing miR-124-based therapeutic strategies for malignant glioma therapy.     

CCL21/CCR7 Enhances the Proliferation,Migration, and Invasion of Human Bladder Cancer T24 Cells

Objective

To investigate the effects of CCL21/CCR7 on the proliferation, migration, and invasion of T24 cells and the possible associated mechanisms: expression of MMP-2 and MMP-9, and regulation of BCL-2 and BAX proteins.

Methods

T24 cells received corresponding treatments including vehicle control, antibody (20ng/mL CCR7 antibody and 50 ng/ml CCL21), and 50, 100, and 200 ng/ml CCL21. Proliferation was evaluated by MTT assay; cell migration and invasion were assayed using a transwell chamber. Cell apoptosis was induced by Adriamycin (ADM). The rate of cell apoptosis was examined by flow cytometry using annexin V-FITC/PI staining. Western-blot was used to analyze MMP-2 and MMP-9 and BCL-2 and BAX proteins.

Results

CCL21 promoted T24 cell proliferation in concentration-dependent manner with that 200 ng/mL induced the largest amount of proliferation. Significant differences of cell migration were found between CCL21treatment groups and the control group in both the migration and invasion studies (P < 0.001 for all). The expressions of MMP-2 and MMP-9 proteins were significantly increased after CCL21 treatment (p < 0.05 for all). Protein expression of Bcl-21 follows an ascending trend while the expression of Bax follows a descending trend as the concentration of CCL21 increases. No difference was found between the control group and antibody group for all assessments.

Conclusion

CCL21/CCR7 promoted T24 cell proliferation and enhanced its migration and invasion via the increased expression of MMP-2 and MMP-9. CCL21/CCR7 had antiapoptotic activities on T24 cells via regulation of Bcl-2 and Bax proteins. CCL21/CCR7 may promote bladder cancer development and metastasis.