Circular RNA circ_0000228 promotes the malignancy of cervical cancer via microRNA-195-5p/ lysyl oxidase-like protein 2 axis

circ_0006789 promotes cervical cancer development via the miR-615-5p/HSF1 axis

OBJECTIVE

Circular RNAs (circRNAs) are involved in the development of human cancers, including cervical cancer (CC). However, the role and mechanism of circ_0006789 (circSLC25A43) in CC are unclear. The purpose of this study was to investigate the functional role of circ_0006789 in CC.

METHODS

The expression of circ_0006789 in CC tissues and cell lines was examined by RT-qPCR. The characterization of circ_0006789 in CC cells was verified by subcellular localisation, actinomycin D assay, and RNase R assay. After circ_0006789 was knocked down in CC cell lines, the proliferation, apoptosis, migration and invasion of CC cells were assessed by CCK-8 method, flow cytometry, and Transwell assay. RIP assay, FISH assay, dual luciferase reporter gene assay and Western blot were used to investigate the regulatory mechanism between circ_0006789, miR-615-5p and heat shock factor 1 (HSF1).

RESULTS

circ_0006789 was upregulated in CC tissues and cell lines. CC cells were inhibited in their proliferation, migration, and invasion, as well as promoted to apoptosis when circ_0006789 was knocked down. It was found that circ_0006789 targeted miR-615-5p, and miR-615-5p expression was inversely correlated with circ_0006789 expression. Furthermore, HSF1 was a target gene of miR-615-5p. Furthermore, the suppressive effects on HeLa cells mediated by circ_0006789 knockdown were counter-balanced when miR-615-5p was knocked down and HSF1 was overexpressed. Mechanistically, circ_0006789 was found to promote CC development by reducing miR-615-5p and increasing HSF1 expressions.

CONCLUSION

circ_0006789 accelerates CC development via the miR-615-5p/HSF1 axis.

Expression of circular RNAs in myelodysplastic neoplasms and their association with mutations in the splicing factor gene SF3B1

Mutations in the splicing factor 3b subunit 1 (SF3B1) gene are frequent in myelodysplastic neoplasms (MDS). Because the splicing process is involved in the production of circular RNAs (circRNAs), we investigated the impact of SF3B1 mutations on circRNA processing. Using RNA sequencing, we measured circRNA expression in CD34+ bone marrow MDS cells. We defined circRNAs deregulated in a heterogeneous group of MDS patients and described increased circRNA formation in higher-risk MDS. We showed that the presence of SF3B1 mutations did not affect the global production of circRNAs; however, deregulation of specific circRNAs was observed. Particularly, we demonstrated that strong upregulation of circRNAs processed from the zinc finger E-box binding homeobox 1 (ZEB1) transcription factor; this upregulation was exclusive to SF3B1-mutated patients and was not observed in those with mutations in other splicing factors or other recurrently mutated genes, or with other clinical variables. Furthermore, we focused on the most upregulated ZEB1-circRNA, hsa_circ_0000228, and, by its knockdown, we demonstrated that its expression is related to mitochondrial activity. Using microRNA analyses, we proposed miR-1248 as a direct target of hsa_circ_0000228. To conclude, we demonstrated that mutated SF3B1 leads to deregulation of ZEB1-circRNAs, potentially contributing to the defects in mitochondrial metabolism observed in SF3B1-mutated MDS.

LOXL2 in Cancer: A Two-Decade Perspective

Lysyl Oxidase Like 2 (LOXL2) belongs to the lysyl oxidase (LOX) family, which comprises five lysine tyrosylquinone (LTQ)-dependent copper amine oxidases in humans. In 2003, LOXL2 was first identified as a promoter of tumour progression and, over the course of two decades, numerous studies have firmly established its involvement in multiple cancers. Extensive research with large cohorts of human tumour samples has demonstrated that dysregulated LOXL2 expression is strongly associated with poor prognosis in patients. Moreover, investigations have revealed the association of LOXL2 with various targets affecting diverse aspects of tumour progression. Additionally, the discovery of a complex network of signalling factors acting at the transcriptional, post-transcriptional, and post-translational levels has provided insights into the mechanisms underlying the aberrant expression of LOXL2 in tumours. Furthermore, the development of genetically modified mouse models with silenced or overexpressed LOXL2 has enabled in-depth exploration of its in vivo role in various cancer models. Given the significant role of LOXL2 in numerous cancers, extensive efforts are underway to identify specific inhibitors that could potentially improve patient prognosis. In this review, we aim to provide a comprehensive overview of two decades of research on the role of LOXL2 in cancer.

MicroRNA and gynecological cancers: Focus on miR-195

Different cancer types have been shown to have down-regulated expression levels of miR-195 as an anti-tumor agent. MiR-195 family members can inhibit cancer cell proliferation, angiogenesis, epithelial-mesenchymal transition and metastases, immunosuppression, glycolysis, drug resistance, and cancer stem cell development by targeting the 3'-UTR of the mRNA of different pro-tumor genes. MiR-195 identified as a tumor suppressor miR in a variety of cancers, most notably gynecological malignancies such as cervical, endometrial, and ovarian carcinoma. As a result, restoring miR-195 expression should be regarded as a potential therapy for either prevention or treatment of gynecological cancers. This review will present the most recent data about miR-195-mediated anti-tumor effects in gynecological malignancies, emphasizing its downstream signaling pathways and target genes, as well as prospective treatment techniques.

Advances in epigenetic modifications and cervical cancer research

Cervical cancer (CC) is an important public health problem for women, and perspectives and information regarding its prevention and treatment are quickly evolving. Human papilloma virus (HPV) has been recognized as a major contributor to CC development; however, HPV infection is not the only cause of CC. Epigenetics refers to changes in gene expression levels caused by non-gene sequence changes. Growing evidence suggests that the disruption of gene expression patterns which were governed by epigenetic modifications can result in cancer, autoimmune diseases, and various other maladies. This article mainly reviews the current research status of epigenetic modifications in CC based on four aspects, respectively DNA methylation, histone modification, noncoding RNA regulation and chromatin regulation, and we also discuss their functions and molecular mechanisms in the occurrence and progression of CC. This review provides new ideas for early screening, risk assessment, molecular targeted therapy and prognostic prediction of CC.

Circ_0006646 Accelerates the Growth and Metastasis of Cervical Cancer by Elevating RRM2 Through miR-758-3p

Cervical cancer (CC) is the fourth most common cancer in women, and circular RNAs (circRNAs) have been shown to regulate CC development. However, the role of circ_0006646 in CC progression is still unclear. The levels of circ_0006646, miR-758-3p, and ribonucleotide reductase regulatory subunit M2 (RRM2) were evaluated by quantitative real-time PCR. Cell proliferation was tested by cell counting kit 8 and 5-ethynyl-2'-deoxyuridine assays. Flow cytometry was used to test cell apoptosis. Migration and invasion were estimated by transwell assay. Western blot assay was performed to examine protein expression. Dual-luciferase reporter assay, RIP assay, and RNA pull down assay were used to analyze the connection between miR-758-3p and circ_0006646 or RRM2. Tumor growth was detected by in vivo experiments. Exosomes were isolated form CC patients and healthy controls. Circ_0006646 expression was elevated in CC cells, and its knockdown suppressed CC cell growth, migration, and invasion. MiR-758-3p was sponged by circ_0006646, and RRM2 was targeted by miR-758-3p. In addition, the effects of circ_0006646 depletion on CC cell progression were overturned by miR-758-3p inhibitor, and either RRM2 overexpression reversed those effects of miR-758-3p overexpression on CC cell progression. Circ_0006646 was highly expressed in the exosomes of CC patients. Circ_0006646 expedited CC cell growth and metastasis by regulating miR-758-3p/RRM2 axis, and exosomal circ_0006646 might be a potential diagnostic indicator of CC.

Scutellaria barbata D. Don inhibits cervical cancer cell proliferation, migration, and invasion via miR-195-5p/LOXL2 axis

Background

Scutellaria barbata D. Don (SB) is a widely used herbal medicine in China, with various pharmacological effects such as anti-oxidation, anti-inflammation, and anti-cancer. This work is aimed to investigate the tumor-suppressive effect of SB in cervical cancer (CC) and to identify its underlying mechanisms.

Methods and materials

CC cell lines (HeLa and HT-3) were treated with different concentrations of SB chloroform extract (ECSB) (0, 0.2, 0.5 mg/ml). MiR-195-5p and LOXL2 mRNA expression in CC cell lines and tissue samples was detected by quantitative real-time polymerase chain reaction. Cell counting kit-8 experiment was utilized to examine cell viability; TUNEL assay and Transwell experiment was executed to examine cell apoptosis, migration, and invasion. Western blotting experiments were implemented to detect LOXL2 protein expression. Bioinformatics and dual-luciferase reporter gene experiment were executed to examine the binding relationship between miR-195-5p and LOXL2.

Results

ECSB repressed the viability, migration, and invasion of HeLa and HT-3 cells, and promoted cell apoptosis in a dose-dependent manner. MiR-195-5p was remarkably under-expressed in CC tissues and cells, and ECSB up-regulated miR-195-5p expression. MiR-195-5p inhibitors partially counteracted the suppressive effects of ECSB on the malignant phenotypes of HeLa and HT-3 cells. LOXL2 was a downstream target of miR-195-5p, and ECSB up-modulated LOXL2 expression by specifically repressing miR-195-5p.

Conclusion

SB restrains CC cell proliferation and metastasis and promotes cell apoptosis via miR-195-5p/LOXL2, which may be a potential therapeutic agent for CC treatment.

circGPA: circRNA functional annotation based on probability-generating functions

Recent research has already shown that circular RNAs (circRNAs) are functional in gene expression regulation and potentially related to diseases. Due to their stability, circRNAs can also be used as biomarkers for diagnosis. However, the function of most circRNAs remains unknown, and it is expensive and time-consuming to discover it through biological experiments. In this paper, we predict circRNA annotations from the knowledge of their interaction with miRNAs and subsequent miRNA-mRNA interactions. First, we construct an interaction network for a target circRNA and secondly spread the information from the network nodes with the known function to the root circRNA node. This idea itself is not new; our main contribution lies in proposing an efficient and exact deterministic procedure based on the principle of probability-generating functions to calculate the p-value of association test between a circRNA and an annotation term. We show that our publicly available algorithm is both more effective and efficient than the commonly used Monte-Carlo sampling approach that may suffer from difficult quantification of sampling convergence and subsequent sampling inefficiency. We experimentally demonstrate that the new approach is two orders of magnitude faster than the Monte-Carlo sampling, which makes summary annotation of large circRNA files feasible; this includes their reannotation after periodical interaction network updates, for example. We provide a summary annotation of a current circRNA database as one of our outputs. The proposed algorithm could be generalized towards other types of RNA in way that is straightforward.

Effects of Circ_0109046 Regulating Mir-338-3p on the Malignant Behavior of A2780 Cells

Objective

The objective is to explore the action and mechanism of circ_0109046 on the malignant phenotypes of ovarian cancer cells.

Methods

Circ_0109046 and miR-338-3p expression were detected by quantitative real-time polymerase chain reaction (qRT-PCR). In vitro assays were conducted to investigate the action of circ_0109046 and miR-338-3p on ovarian cancer cell growth and metastasis. Western blotting was utilized to investigate the contents of apoptosis-related markers. The binding between circ_0109046 and miR-338-3p was validated using dual-luciferase reporter assay.

Results

Circ_0109046 was increased, while miR-338-3p content was decreased in ovarian cancer tissues. Deficiency of circ_0109046 or the upregulation of miR-338-3p was observed to weaken cell proliferative, migratory, and invasive abilities and elevated cell apoptosis rate in ovarian cancer. Circ_0109046 targetedly suppressed miR-338-3p. Down-regulation of miR-338-3p was able to reverse the repressing impacts of circ_0109046 silencing on ovarian cancer growth and mobility.

Conclusion

Circ_0109046 silencing impaired the proliferation, migration, and invasion of ovarian cancer cells through negatively regulating miR-338-3p in vitro, indicating the potential implication of circ_0109046 in ovarian cancer progression.

Roles and mechanisms of miR-195-5p in human solid cancers

Cancer persists as a worldwide disease that contributes to high morbidity and mortality rates. As a class of non-coding RNA, microRNAs (miRNAs) are one kind of important regulators in cancer and frequently implicated in tumor development and progression. Emerging experiments have suggested that miRNA-195-5p (miR-195-5p) can regulate neoplastic processes in many pathways. For instance, miR-195-5p can not only regulate proliferation, migration and invasion of tumor cells but also promote tumor cell apoptosis. Furthermore, low expression of miR-195-5p could induce drug resistance. Our review focuses on the expression of miR-195-5p in various tumors and elucidates the related mechanisms of which miR-195-5p participates in tumor biology, as well as summarizes the roles of miR-195-5p in tumor progression. We believe that miR-195-5p might have potential utility as a novel diagnostic biomarker and therapeutic target for cancer.

Circular_0086414 induces SPARC like 1 (SPARCL1) production to inhibit esophageal cancer cell proliferation, invasion and glycolysis and induce cell apoptosis by sponging miR-1290

Circular RNA (circRNA) plays an important role in cancer progression. Here, we investigated the function of circ_0086414 in the malignant progression of esophageal cancer (EC). RNA expression of circ_0086414, microRNA-1290 (miR-1290), and SPARC like 1 (SPARCL1) was detected by quantitative real-time polymerase chain reaction. The protein levels of N-cadherin, E-cadherin, and SPARCL1 were checked by Western blotting analysis. Cell proliferation was investigated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-Ethynyl-29-deoxyuridine (EdU), and cell colony formation assays. Cell invasion and apoptosis were analyzed by transwell invasion assay and flow cytometry analysis, respectively. Glycolysis was evaluated by analyzing glucose consumption and lactate production. In an xenograft mouse model, the effect of circ_0086414 on tumor tumorigenesis was investigated. The interactions among circ_0086414, miR-1290, and SPARCL1 were identified by dual-luciferase reporter and RNA pull-down assays. Results showed that circ_0086414 and SPARCL1 expression were significantly downregulated, while miR-1290 was upregulated in EC tissues and cells. EC patients with low circ_0086414 expression had a poor prognosis. Increasing circ_0086414 expression led to decreased EC cell proliferation, invasion and glycolysis and increased cell apoptosis, accompanied by a decrease of N-cadherin expression and an increase of E-cadherin expression. Also, the enforced expression of circ_0086414 delayed tumor tumorigenesis. Besides, circ_0086414 acted as a miR-1290 sponge and regulated EC cell processes by binding to the miRNA. MiR-1290 also participated in EC malignant progression through SPARCL1. Further, circ_0086414 stimulated SPARCL1 production by negatively regulating miR-1290. Thus, circ_0086414 inhibited EC cell malignancy through the miR-1290/SPARCL1 pathway, providing a reliable target for the therapy of EC.

Circular RNAs as emerging players in cervical cancer tumorigenesis; A review to roles and biomarker potentials

Cervical cancer is the most lethal gynecological cancer among women worldwide. Most of the patients are diagnosed at the advanced stages due to late diagnosis and lack of accessible and valuable approaches for early detection of the disease. Circular RNAs (circRNAs) are a distinguishable class of non-coding RNAs with characteristic loop structures. Although their function has not been completely elucidated; however, recent evidence has suggested regulatory functions for circRNAs on gene expression controlling various biological functions like cell growth and apoptosis, development, embryogenesis, and pathogenesis of human diseases particularly cancers. Studies show the role of dysregulated circRNAs in biological processes including cell proliferation, migration, invasion, apoptosis, angiogenesis, and chemoresistance contributing to affect tumorigenesis in ovarian cancer cells, animal, and clinical studies. These effects can be defined as consistent with several tumorigenesis characteristics, which are defined as "hallmarks of cancer". Additionally, dysregulated circRNAs exhibit prognostic, and diagnostic potentials both in the prediction of prognosis in ovarian cancer patients, and also their discrimination from healthy individuals. Furthermore, targeting circRNAs has shown positive results in the suppression of malignant features of cancer cells, and also in overcoming chemoresistance. In this review, I have gathered the majority of studies evaluating the role of circRNAs in the development, and progression of cervical cancer, and also have discussed prognostic, diagnostic, and therapeutic potentials of circRNAs for clinical applications in cervical cancer patients.

Circular RNA hsa_circ_0004543 Aggravates Cervical Cancer Development by Sponging MicroRNA hsa-miR-217 to Upregulate Hypoxia-Inducible Factor

Cervical cancer (CC) is the 4^th principal source of cancer death in females with 604,000 new patients and 342,000 deaths in 2020 worldwide. It has been extensively shown that circRNAs are involved in regulating CC development. Nevertheless, the function and mechanisms of hsa_circ_0004543 in regulating CC need to be clearly elucidated. Herein, hsa_circ_0004543 expressions were compared between 40 paired paracancerous and cancerous specimens from CC patients and between 6 CC cell lines and a normal human cervical epithelial cell line based on qRT-PCR. Potential complementary binding sites between hsa-miR-217 and hsa_circ_0004543 were predicted using the interactome, while binding sites for the hypoxia-inducible factor-1a (HIF-1a) were predicted by TargetScan. The function and mechanism of hsa_circ_0004543 in the development of CC were estimated by silencing hsa_circ_0004543 with/without hsa-miR-217 or HIF-1a overexpression. The association between gene expressions was evaluated with Pearson's correlation analysis. Molecular mechanisms were explored by ribonucleic acid (RNA) pulldown, dual-luciferase activity, and rescue experimental assays. Our results revealed that the hsa_circ_0004543 expression was considerably increased in CC tissues and cells. Its silencing repressed proliferation and metastasis, while it increased apoptosis of CC cells. The investigation of the mechanism showed that hsa-miR-217 silencing or HIF-1a overexpression rescued hsa_circ_0004543, and silencing inhibited malignant phenotypes of CC cells. hsa_circ_0004543 upregulated the HIF-1α expression by sponging hsa-miR-217 in CC development. Therefore, the hsa_circ_0004543 functioned as a competing endogenous RNA (ceRNA) of hsa-miR-217 to increase CC oncogenesis and metastasis by the upregulation of the HIF-1α expression. Consequently, targeting the hsa_circ_0004543/hsa-miR-217/HIF-1α axis might be a potential treatment approach for CC.

Metallothionein-like 5 expression is correlated with poor prognosis and promotes proliferation of cervical squamous cell carcinoma

Cervical cancer represents one of the most important female genital cancers. Cervical squamous cell carcinoma (CESC) accounts for about 90% of all cervical malignancies and the prognosis are unsatisfied. Here we aimed to investigate the clinical relevance of metallothionein-like 5 (MTL5), a novel metallothionein-like protein, in CESC. RT-qPCR and immunohistochemistry staining showed that MTL5 was upregulated in CESC tissues than nontumorous cervix tissues, which is consistent with the data from TCGA database. Kaplan-Meier survival analysis revealed that higher MTL5 can help predict worse prognosis. In addition, Cox hazard regression analysis verified an independent predictive role of MTL5 in CESC. To further investigate the involvement of MTL5 in CESC, we conducted knockdown experiments in two CESC cell lines. As a result, silencing MTL5g significantly inhibited proliferation of CESC cells. Finally, we validated that silencing MTL5 can suppress CESC tumor growth in vivo using the mice subcutaneous xenografts model. Taken together, higher MTL5 indicates worse survival of CESC after surgical resection. Targeting MTL5 represents a potential therapy of CESC by inhibiting tumor growth, which deserves further investigations.

Circular RNA Pvt1 oncogene (CircPVT1) promotes the progression of papillary thyroid carcinoma by activating the Wnt/β-catenin signaling pathway and modulating the ratio of microRNA-195 (miR-195) to vascular endothelial growth factor A (VEGFA) expression

Circular RNAs (circRNAs) have been reported to be involved in the progression of papillary thyroid carcinoma (PTC). However, the role of circular RNA Pvt1 oncogene (circPVT1) in PTC has rarely been reported. In this study, we aimed to investigate the function and mechanism of circPVT1 in PTC. The expression level of circPVT1, miR-195 and VEGFA were determined by reverse transcription‑quantitative PCR (RT‑qPCR). Fisher's exact test was used to analyze the correlation between circPVT1 expression and PTC clinical features. Cell Counting Kit-8 (CCK-8) and 5-Ethynyl-2'-deoxyuridine (EdU) staining assay and transwell assay were conducted to evaluate the cell proliferation, migration and invasion ability. Dual-luciferase reporter and Western blot assay were conducted for evaluating the correlation between miR-195 and circPVT1 or VEGFA. The results of RT-PCR showed that the expression level of circPVT1 was significantly upregulated in PTC tissues and cell lines. After downregulating circPVT1 expression in PTC cells, the abilities of cell proliferation, migration, and invasion were obviously suppressed, and the Wnt/β-catenin signaling pathway was also repressed. Besides, miR-195 could both bind to PVT1 and VEGFA, while PVT1 could promote the expression of VEGFA by binding to miR-195. Downregulation of VEGFA expression in PTC cells revealed weakened cell proliferation, migration, and invasion capacities, and restrained Wnt/β-catenin signaling pathway. Therefore, we demonstrated that circPVT1 could promote VEGFA expression by sponging miR-195. CircPVT1 could serve as a molecule sponge for miR-195 and mediate the ceRNA network to promote the expression of VEGFA, thus contributed to the malignant progression of PTC.

MicroRNA-98-5p modulates cervical cancer progression via controlling PI3K/AKT pathway

To probe into the potential mechanism of microRNA (miR)-98-5p inhibiting the biological progress of cervical cancer (CC) cells via regulating PI3K/Akt pathway. Reverse transcription quantitative polymerase chain reaction was applied to detect miR-98-5p expression in CC tissues and cell lines; Cell counting kit-8 and Edu analysis were performed for checking cell proliferation, flow cytometry for cell apoptosis, transwell for cell invasion and migration, Western blot for proliferation-related proteins Ki67 and Proliferating cell nuclear antigen expression, apoptosis-related proteins Bcl-2 and Bax expression, epithelial-mesenchymal transition (EMT)-related proteins Snail, matrix metalloproteinase-3, E-cadherin and N-cadherin expression, as well as PI3K/Akt pathway-related proteins PTEN, PI3K as well as Akt expression levels, and the nude mouse tumor xenograft experiment was applied to verify in vivo. The result clarified, miR-98-5p was reduced in CC. Overexpression miR-98-5p could inhibit CC cell proliferation, invasion, migration and EMT, whereas promoted its apoptosis, but silencing miR-98-5p was opposite. Overexpression miR-98-5p could depress the activation of PI3K/Akt pathway in CC in vivo and in vitro. MiR-98-5p targeted CBX5. In short, miR-98-5p is able to be used as a potential target for treating CC in future research.

Circular RNA circVRK1 suppresses the proliferation, migration and invasion of osteosarcoma cells by regulating zinc finger protein ZNF652 expression via microRNA miR-337-3p

Circular RNA is an innovative kind of endogenous non-coding RNA, which could take part in tumorigenesis. Nonetheless, the potential molecular mechanisms of circVRK1 in the progression of osteosarcoma remain unresolved. In the current study, we initially investigated circVRK1 levels in osteosarcoma clinical samples and cell lines by qRT-PCR analysis and northern blot assay. RNase R treatments, RNA stability assay and nucleoplasmic separation assay were conducted to identify the characteristics of circVRK1. We adopted CCK-8, colony formation, wound-healing, and transwell assays to assess the biological effects of circVRK1 on the proliferation, migration, and invasiveness of osteosarcoma cells in vitro. We then constructed a xenograft model in nude mice to confirm the suppressive role of circVRK1 in vivo. Moreover, dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays were utilized to elucidate the underlying molecular mechanisms mediated by circVRK1. We demonstrated that circVRK1 was a stable circular transcript localized in the cytoplasm of osteosarcoma cells, and the down-regulation of circVRK1 in osteosarcoma tissues was related to poor outcome of patients. Meanwhile, over-expressed circVRK1 obviously restrained the growth, migration, and invasion of osteosarcoma in vitro and in vivo. Mechanistically, circVRK1 was assumed to be a microRNA sponge for miR-337-3p, and ZNF652 was the downstream gene of miR-337-3p. CircVRK1 overexpression or miR-337-3p knockdown accelerated ZNF652 expression, and up-regulated miR-337-3p efficiently abolished the promotion of ZNF652 induced by circVRK1. Moreover, rescue experiments have proved that circVRK1 inhibits the progression of osteosarcoma by modulating the miR-337-3p/ZNF652 axis. Therefore, we conclude that circVRK1 promotes ZNF652 expression by sponging miR-337-3p. CircVRK1 serves as a molecule sponge for miR-337-3p and mediates the ceRNA network to promote the expression of ZNF652, thus suppresses osteosarcoma proliferation, migration and invasion.