ICAM-5 (telencephalin) gene expression in head and neck squamous carcinoma tumorigenesis and perineural invasion!

DNMT1/DNMT3a-mediated promoter hypermethylation and transcription activation of ICAM5 augments thyroid carcinoma progression

Promoter methylation is one of the most studied epigenetic modifications and it is highly relevant to the onset and progression of thyroid carcinoma (THCA). This study investigates the promoter methylation and expression pattern of intercellular adhesion molecule 5 (ICAM5) in THCA. CpG islands with aberrant methylation pattern in THCA, and the expression profiles of the corresponding genes in THCA, were analyzed using bioinformatics. ICAM5 was suggested to have a hypermethylation status, and it was highly expressed in THCA tissues and cells. Its overexpression promoted proliferation, mobility, and tumorigenic activity of THCA cells. As for the downstream signaling, ICAM5 was found to activate the MAPK/ERK and MAPK/JNK signaling pathways. Either inhibition of ERK or JNK blocked the oncogenic effects of ICAM5. DNA methyltransferases 1 (DNMT1) and DNMT3a were found to induce promoter hypermethylation of ICAM5 in THCA cells. Knockdown of DNMT1 or DNMT3a decreased the ICAM5 expression and suppressed malignant properties of THCA cells in vitro and in vivo, which were, however, restored by further artificial ICAM5 overexpression. Collectively, this study reveals that DNMT1 and DNMT3a mediates promoter hypermethylation and transcription activation of ICAM5 in THCA, which promotes malignant progression of THCA through the MAPK signaling pathway.

Perineural Invasion (PNI) Definition, Histopathological Parameters of PNI in Oral Squamous Cell Carcinoma With Molecular Insight and Prognostic Significance

Oral squamous cell carcinoma is associated with severe morbidity, recurrence of tumor, and reduced survival rate despite advances in treatment. Perineural invasion (PNI) is associated with neurotropic malignancy. PNI is due to the tropism of cancer cells toward nerve bundles in tissue. The aim of this literature review is to study the definition, patterns of PNI, Prognostic and therapeutic significance, and mechanism of PNI along with a molecular insight into oral cavity squamous cell carcinoma. Liebig type A pattern defines PNI as the presence of tumor cells within the peripheral nerve sheath & infiltration into the epineurium, perineurium, or endoneurium. Liebig type B pattern defines PNI as a tumor encircling at least 33% of a nerve. Few studies demonstrated an association between PNI and cervical metastasis which indicate poor prognosis. A higher level of expression of nerve growth factor and tyrosine kinase is associated with PNI in OSCC which can be considered as a biomarker of PNI. PNI needs to be studied in detail as it is associated with the aggressiveness of the tumor and decreased survival.

Identification of prognostic biomarkers among ICAMs in the breast cancer microenvironment

BACKGROUND

Intercellular adhesion molecules (ICAMs) in the tumor microenvironment are closely related to immunity and affect the prognosis of cancer patients.

OBJECTIVE

The aim of our study is to explore the correlation between ICAM expression, mutation, methylation and immunity and their prognostic value in breast cancer (BC) is not clear.

METHODS

Online databases and tools such as UALCAN, COSMIC, cBioPortal, MethSurv, PrognoScan, Kaplan-Meier Plotter, GSCA and TIMER were utilized in this study.

RESULTS

We found that the mRNA and protein expression levels of ICAM1 were upregulated in triple-negative breast cancer (TNBC) compared with normal tissues, and TNBC patients with high expression of ICAM1 had better overall survival (OS) and recurrence-free survival (RFS). The main types of ICAM1 gene variants were missense mutation and amplification, and ICAM1 showed a lower level of methylation in TNBC cancer tissues than in normal tissues, which was contrary to the high expression levels of ICAM1 mRNA and protein. Next, the function of ICAM1 was mainly related to the activation of apoptosis, epithelial-mesenchymal transition (EMT) and inhibition of the androgen receptor (AR) and estrogen receptor (ER) pathways. Meanwhile, functional pathway enrichment results showed that ICAM1 was also involved in the immune regulation process of BC. Furthermore, the expression of ICAM1 was positively associated with 6 types of tumor-infiltrating immune cells (CD8+ T cells, CD4+ T cells, B cells, neutrophils, macrophages and dendritic cells) and was also positively related to the expression of programmed cell death-1 (PD-1), programmed cell death-ligand 1 (PD-L1) and cytotoxic T lymphocyte-associated antigen-4 (CTLA4).

CONCLUSIONS

Our research indicated that ICAM1 was likely to be a potential therapeutic target in TNBC.

UCHL5 Promotes Proliferation and Migration of Bladder Cancer Cells by Activating c-Myc via AKT/mTOR Signaling

Ubiquitin C-terminal hydrolase L5 (UCHL5) is a deubiquitinating enzyme (DUB) that removes ubiquitin from its substrates. Associations between UCHL5 and cancer have been reported in various tissues, but the effect of UCHL5 on bladder cancer has not been thoroughly investigated. This study investigates the expression and function of UCHL5 in bladder cancer. UCHL5 was shown to be abnormally expressed using IHC of tissue microarray and Western blotting. Several procedures were performed to assess the effect of UCHL5 overexpression or knockdown on bladder cancer, such as cell proliferation, colony formation, wound-healing, and Transwell assays. In addition, RNA-Seq and Western blotting experiments were used to verify the status of downstream signaling pathways. Finally, bladder cancers with knockdown or overexpression of UCHL5 were treated with either SC79 or LY294002 to examine the participation of the AKT/mTOR signaling pathway and the expression of downstream targets c-Myc, SLC25A19, and ICAM5. In contrast to adjacent tissue samples, we discovered that UCHL5 was substantially expressed in bladder cancer samples. We also found that UCHL5 downregulation significantly suppressed both tumor growth in vivo and cell proliferation and migration in vitro. According to RNA-Seq analyses and Western blotting experiments, the expression of c-Myc, SLC25A19, and ICAM5 was modified as a result of UCHL5 activating AKT/mTOR signaling in bladder cancer cells. All things considered, our findings show that increased UCHL5 expression stimulates AKT/mTOR signaling, subsequently triggering the expression of c-Myc, SLC25A19, and ICAM5, which in turn promotes carcinogenesis in bladder cancer. UCHL5 is therefore a potential target for therapy in bladder cancer patients.

Perineural invasion-associated biomarkers for tumor development

Perineural invasion (PNI) is the process of neoplastic invasion of peripheral nerves and is considered to be the fifth mode of cancer metastasis. PNI has been detected in head and neck tumors and pancreatic, prostate, bile duct, gastric, and colorectal cancers. It leads to poor prognostic outcomes and high local recurrence rates. Despite the increasing number of studies on PNI, targeted therapeutic modalities have not been proposed. The identification of PNI-related biomarkers would facilitate the non-invasive and early diagnosis of cancers, the establishment of prognostic panels, and the development of targeted therapeutic approaches. In this review, we compile information on the molecular mediators involved in PNI-associated cancers. The expression and prognostic significance of molecular mediators and their receptors in PNI-associated cancers are analyzed, and the possible mechanisms of action of these mediators in PNI are explored, as well as the association of cells in the microenvironment where PNI occurs.

The Role of ECM Remodeling, EMT, and Adhesion Molecules in Cancerous Neural Invasion: Changing Perspectives

Perineural invasion (PNI) refers to the cancerous invasion of nerves. It provides an alternative route for metastatic invasion and can exist independently in the absence of lymphatic or vascular invasion. It is a prominent characteristic of specific aggressive malignancies where it correlates with poor prognosis. The clinical significance of PNI is widely recognized despite a lack of understanding of the molecular mechanisms underlying its pathogenesis. The interaction between the nerve and the cancer cells is the most pivotal PNI step which is mediated by the activation or inhibition of multiple signaling pathways that include chemokines, interleukins, nerve growth factors, and matrix metalloproteinases, to name a few. The nerve-cancer cell interaction brings about specific changes in the perineural niche, which not only affects the regular nerve functions, but also enhances the migratory, invasive, and adherent properties of the tumor cells. This review aims to elucidate the vital role of adhesion molecules, extracellular matrix, and epithelial-mesenchymal proteins that promote PNI, which may serve as therapeutic targets in the future.

Neurotropic Cutaneous Malignancies: Case Report on Keratinocyte Derived Malignancies of the Head and Neck With Perineural Invasion

Background

The recent addition of immunotherapy as a treatment modality to surgery and radiation has vastly improved disease control for patients with keratinocyte-derived carcinomas (KCs) that are incurable with local therapies alone. With the advent of immune checkpoint inhibitors (ICPis) in non-melanoma skin cancers comes diagnostic and therapeutic challenges when considering treatment strategies for patients presenting with clinical perineural invasion (cPNI) of locally advanced KC of the head and neck.

Objectives

We report four cases that convey the diagnostic and therapeutic complexity of managing patients with neuropathic symptoms from cutaneous neurotropic carcinomas of the head and neck. We also discuss an updated review regarding immunotherapies and perineural invasion within KC management.

Conclusion

Patients presenting with symptoms suspicious for cPNI warrant an expanded diagnostic evaluation to correlate neurological findings with neurotropic spread of disease. While nerve biopsies can be precarious in sensitive areas, a history of skin cancer and clinical presentation suggestive of neurotropism may be enough to pursue timely management in the form of surgery, radiation, and/or systemic therapy given each patient’s individual priorities, comorbidities, and prognosis. When adding ICPi as a treatment modality for patients with disease not amenable to local therapies, the potential for immune-related adverse events must be considered. A multi-disciplinary review and approach to the management of patients with KC and cPNI is essential for obtaining optimal patient outcomes.

A Novel 16-Genes Signature Scoring System as Prognostic Model to Evaluate Survival Risk in Patients with Glioblastoma

Previous studies have found that gene expression levels are associated with prognosis and some genes can be used to predict the survival risk of glioblastoma (GBM) patients. However, most of them just built the survival-related gene signature, and personal survival risk can be evaluated only in group. This study aimed to find the prognostic survival related genes of GBM, and construct survival risk prediction model, which can be used to evaluate survival risk by individual. We collected gene expression data and clinical information from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. Cox regression analysis and LASSO-cox regression analysis were performed to get survival-related genes and establish the overall survival prediction model. The ROC curve and Kaplan Meier analysis were used to evaluate the prediction ability of the model in training set and two independent cohorts. We also analyzed the biological functions of survival-related genes by GO and KEGG enrichment analysis. We identified 99 genes associated with overall survival and selected 16 genes (IGFBP2, GPRASP1, C1R, CHRM3, CLSTN2, NELL1, SEZ6L2, NMB, ICAM5, HPCAL4, SNAP91, PCSK1N, PGBD5, INA, UCHL1 and LHX6) to establish the survival risk prediction model. Multivariate Cox regression analysis indicted that the risk score could predict overall survival independent of age and gender. ROC analyses showed that our model was more robust than four existing signatures. The sixteen genes can also be potential transcriptional biomarkers and the model can assist doctors on clinical decision-making and personalized treatment of GBM patients.

Gene expression profiling of perineural invasion in head and neck cutaneous squamous cell carcinoma

Perineural invasion (PNI) is frequently associated with aggressive clinical behaviour in head and neck cutaneous squamous cell carcinoma (HNcSCC) leading to local recurrence and treatment failure. This study evaluates the gene expression profiles of HNcSCC with PNI using a differential expression analysis approach and constructs a tailored gene panel for sensitivity and specificity analysis. 45 cases of HNcSCC were stratified into three groups (Extensive, Focal and Non PNI) based on predefined clinicopathological criteria. Here we show HNcSCC with extensive PNI demonstrates significant up- and down-regulation of 144 genes associated with extracellular matrix interactions, epithelial to mesenchymal transition, cell adhesion, cellular motility, angiogenesis, and cellular differentiation. Gene expression of focal and non PNI cohorts were indistinguishable and were combined for further analyses. There is clinicopathological correlation between gene expression analysis findings and disease behaviour and a tailored panel of 10 genes was able to identify extensive PNI with 96% sensitivity and 95% specificity.

Identification of diagnostic and prognostic lncRNA biomarkers in oral squamous carcinoma by integrated analysis and machine learning

BACKGROUND

Patients with oral squamous carcinoma (OSCC) present difficulty in precise diagnosis and poor prognosis.

OBJECTIVE

We aimed to identify the diagnostic and prognostic indicators in OSCC and provide basis for molecular mechanism investigation of OSCC.

METHODS

We collected sequencing data and clinical data from TCGA database and screened the differentially expressed mRNAs (DEmRNAs) and lncRNAs (DElncRNAs) in OSCC. Machine learning and modeling were performed to identify the optimal diagnostic markers. In order to determine lncRNAs with prognostic value, survival analysis was performed through combing the expression profiles with the clinical data. Finally, co-expressed DEmRNAs of lncRNAs were identified by interacted network construction and functional annotated by GO and KEGG analysis.

RESULTS

A total of 1114 (345 up- and 769 down-regulated) DEmRNAs and 156 (86 up- and 70 down-regulated) DElncRNAs were obtained in OSCC. Following the machine learning and modeling, 15 lncRNAs were identified to be the optimal diagnostic indicators of OSCC. Among them, FOXD2.AS1 was significantly associated with survival rate of patients with OSCC. In addition, Focal adhesion and ECM-receptor interaction pathways were found to be involved in OSCC.

CONCLUSIONS

FOXD2.AS1 might be a prognostic marker for OSCC and our study may provide more information to the further study in OSCC.

Integrating Clinical and Genetic Analysis of Perineural Invasion in Head and Neck Squamous Cell Carcinoma

Introduction: Perineural invasion (PNI), a key pathological feature of head and neck squamous cell carcinoma (HNSCC), predicts poor survival. However, the associated clinical characteristics remain uncertain, and the molecular mechanisms are largely unknown. Materials and methods: HNSCC gene expression and corresponding clinical data were downloaded from The Cancer Genome Atlas (TCGA). Prognostic subgroup analysis was performed, and potential PNI risk factors were assessed with logistic regression. PNI-associated gene coexpression modules were identified with weighted gene coexpression network analysis (WGCNA), and key module gene functions and the roles of non-malignant cells in PNI were evaluated with a single-cell transcriptomic dataset (GSE103322). Results: PNI was significantly inversely associated with overall survival (HR, 2.08; 95% CI, 1.27 to 3.40; P = 0.004), especially in advanced patients (HR, 2.62; 95% CI, 1.48 to 4.64; P < 0.001). Age, gender, smoking history, and alcohol history were not risk factors. HPV-positive cases were less likely than HPV-negative cases to develop PNI (OR, 0.28; 95% CI, 0.09 to 0.76; P = 0.017). WGCNA identified a unique significantly PNI-associated coexpression module containing 357 genes, with 12 hub genes (TIMP2, MIR198, LAMA4, FAM198B, MIR4649, COL5A1, COL1A2, OLFML2B, MMP2, FBN1, ADAM12, and PDGFRB). Single-cell transcriptomic data analysis revealed that the genes in the PNI-associated module correlated with the signatures "EMT," "metastasis," and "invasion." Among non-malignant cells, fibroblasts had relatively high expression of the key genes. Conclusion: At the molecular and omic levels, we verified that PNI in HNSCC is a process of invasion rather than simple diffusion. Fibroblasts probably play an important role in PNI. Novelty & Impact Statements  The study is a thorough analysis of PNI in HNSCC from the clinical level to the molecular level and presents the first description of cancer-related PNI from the omics perspective to date as far as we know. We verified that PNI in HNSCC is a process of invasion rather than simple diffusion, at the molecular and omic levels. Fibroblasts were found to probably play an important role in PNI by analyzing single-cell transcriptomic data.

Yarrow supercritical extract exerts antitumoral properties by targeting lipid metabolism in pancreatic cancer

Metabolic reprogramming is considered a hallmark of cancer. Currently, the altered lipid metabolism in cancer is a topic of interest due to the prominent role of lipids regulating the progression of various types of tumors. Lipids and lipid-derived molecules have been shown to activate growth regulatory pathways and to promote malignancy in pancreatic cancer. In a previous work, we have described the antitumoral properties of Yarrow (Achillea Millefolium) CO₂ supercritical extract (Yarrow SFE) in pancreatic cancer. Herein, we aim to investigate the underlaying molecular mechanisms by which Yarrow SFE induces cytotoxicity in pancreatic cancer cells. Yarrow SFE downregulates SREBF1 and downstream molecular targets of this transcription factor, such as fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD). Importantly, we demonstrate the in vivo effect of Yarrow SFE diminishing the tumor growth in a xenograft mouse model of pancreatic cancer. Our data suggest that Yarrow SFE can be proposed as a complementary adjuvant or nutritional supplement in pancreatic cancer therapy.

[Advances in the molecular mechanisms of perineural invasion in salivary adenoid cystic carcinoma]

Salivary adenoid cystic carcinoma is a very common malignant neoplasm in the salivary glands. One of the most important features of salivary cystic carcinoma is perineural invasion, which renders its complete removal is very difficult through clinical surgery. Consequently, tumor recurrence occurs easily after clinical surgery. Therefore, the molecular mechanisms of perineural invasion in salivary adenoid cystic carcinoma are necessary to explore. These mechanisms are reviewed in this paper.

Perineural Invasion in Head and Neck Cancer

Perineural invasion (PNI) is a mechanism of tumor dissemination that can provide a challenge to tumor eradication and that is correlated with poor survival. Squamous cell carcinoma, the most common type of head and neck cancer, has a high prevalence of PNI. This review provides an overview of clinical studies on the outcomes and factors associated with PNI in head and neck cancer and on findings on cancer-nerve crosstalk.

The role of perineural invasion in treatment decisions for oral cancer patients: A review of the literature

PURPOSE

The role of perineural invasion (PNI) in the management of patients with oral squamous cell carcinoma (OSSC) is still controversial, and there is no consensus regarding the most appropriate therapeutic approach. The purpose of this study is to review the findings in the literature describing OSCC as a neurotropic malignancy, with the aim of correlating perineural invasion with treatment decisions and disease prognosis.

MATERIALS AND METHODS

A literature search was conducted of references based on the MEDLINE and Cochrane Database of Systematic Reviews, with subject keywords including four main categories: perineural invasion, perineural spread, oral squamous cell cancinoma, neurotropic carcinoma.

RESULTS

In this systematic review and analysis, more than 350 publications met the eligibility criteria of the authors.

CONCLUSION

Perineural invasion (PNI) is a widely recognized indicator of poor prognosis in oral cancer patients, strongly correlating with aggressive tumor behavior, disease recurrence, and increased morbidity and mortality. Elective neck dissection could be an indicator in improving neck control in PNI-positive patients, while the addition of adjuvant postoperative radiotherapy may not significantly improve survival rates. Various molecular markers have been correlated with perineural tumor spread, but further investigations are required before targeting PNI as part of advanced cancer therapies.

Laminin-5 and insulin-like growth factor-II mRNA binding protein-3 (IMP3) expression in preoperative biopsy specimens from oral cancer patients: Their role in neural spread risk and survival stratification

Perineural invasion (PNI) hinders the ability to establish local control of oral squamous cell carcinoma (OSCC). To date, PNI can be evaluated only in surgical specimens and not in preoperative biopsy material, rendering timely therapeutic planning impossible. Insulin-like growth factor-II mRNA binding protein-3 (IMP3) expression appears to be of diagnostic and prognostic utility for many solid tumours, and laminin-5 expression in surgical specimens has been identified as a valid predictor of neural spread of head-and-neck neoplasms. The ability to use preoperative biopsy material to identify patients exhibiting PNI is fundamental for good management of OSCC. We examined a series of 64 consecutive patients treated (primarily via surgery) for OSCC between 2009 and 2014 at the Maxillofacial Surgery Unit, University of Bologna. We evaluated IMP3 and laminin-5 expression in preoperative biopsy material using immunohistochemistry and quantitative reverse transcription polymerase chain reaction. We sought to correlate expression of IMP3 and laminin-5 with PNI evident in surgical specimens. Expression of IMP3 and laminin-5 in preoperative biopsy material appeared to be predictive of PNI in patients with OSCC (P < 0.001). Additionally, the results of multivariate analyses showed that IMP3 status was an independent predictor of death of patients with OSCC (P = 0.001). The present study demonstrates that IMP3 and laminin-5 expression in preoperative biopsy material correlate well with PNI status and may allow accurate preoperative risk stratification of patients with OSCC.

A systematic approach to prioritize drug targets using machine learning, a molecular descriptor-based classification model, and high-throughput screening of plant derived molecules: a case study in oral cancer

Network-based and cheminformatics approaches identify novel lead molecules forCXCR4, a key gene prioritized in oral cancer.

Prognostic significance of perineural invasion in cervical cancer

Perineural invasion (PNI) has attracted attention as a new prognostic factor for cancer. We aimed to investigate the prognostic value of PNI in patients with cervical cancer. Clinical data of 185 patients with early-stage cervical cancer (stages IA2-IIA2) who underwent radical hysterectomy and pelvic lymphadenectomy between 2003 and 2011 were investigated. PNI was detected in 7% (13 of 18 cases) of patients. Moreover, 92% (12 of 13 cases) of patients with PNI received radiation therapy or concurrent chemoradiation therapy after surgery. We investigated whether PNI can be a new indication for adjuvant therapy for cervical cancer. In our study, PNI had a significant association with well-known indications for adjuvant therapy (92.3% sensitivity, 50% specificity, odds ratio 12.0, P = 0.003). Multivariate analysis showed that parametrial invasion and lymphovascular invasion were independently associated with PNI (P < 0.05). However, statistical analysis did not show differences in disease-free survival (P = 0.292) or overall survival (P = 0.346) according to the presence of PNI. In conclusion, PNI as an independent predictor for prognosis was limited, but PNI had a significant association with prognostic factors. PNI may be a new risk factor candidate for cervical cancer. PNI is expected to help in decision making for the need for adjuvant therapy.

Telencephalin protects PAJU cells from amyloid beta protein-induced apoptosis by activating the ezrin/radixin/moesin protein family/phosphatidylinositol-3-kinase/protein kinase B pathway

Telencephalin is a neural glycoprotein that reduces apoptosis induced by amyloid beta protein in the human neural tumor cell line PAJU. In this study, we examined the role of the ezrin/radixin/moesin protein family/phosphatidylinositol-3-kinase/protein kinase B pathway in this process. Western blot analysis demonstrated that telencephalin, phosphorylated ezrin/radixin/moesin and phosphatidylinositol-3-kinase/protein kinase B were not expressed in PAJU cells transfected with empty plasmid, while they were expressed in PAJU cells transfected with a telencephalin expression plasmid. After treatment with 1.0 nM amyloid beta protein 42, expression of telencephalin and phosphorylated phosphatidylinositol-3-kinase/protein kinase B in the transfected cells gradually diminished, while levels of phosphorylated ezrin/radixin/moesin increased. In addition, the high levels of telencephalin, phosphorylated ezrin/radixin/moesin and phosphatidylinositol-3-kinase/protein kinase B expression in PAJU cells transfected with a telencephalin expression plasmid could be suppressed by the phosphatidylinositol-3-kinase inhibitor LY294002. These findings indicate that telencephalin activates the ezrin/radixin/moesin family/phosphatidylinositol-3-kinase/protein kinase B pathway and protects PAJU cells from amyloid beta protein-induced apoptosis.

Expression profile of genes regulated by curcumin in Y79 retinoblastoma cells

Curcumin, a well-known chemopreventive agent from turmeric, inhibits the expression of several oncogenes and cell proliferation genes in tumor cells. This study aims to understand the precise molecular mechanism by which curcumin exerts its effects on retinoblastoma cells, by performing whole genome microarray analysis to determine the gene expression profiles altered by curcumin treatment. Curcumin suppressed cell viability and altered the cell cycle of retinoblastoma cells. We identified 903 downregulated genes and 1,319 upregulated genes when compared with the control cells after treatment with 20 μM curcumin concentration for 48 h. These genes were grouped into respective functional categories according to their biological function. We found that curcumin regulated the expression of genes that are involved in the regulation of apoptosis, tumor suppressor, cell-cycle arrest, transcription factor, and angiogenesis. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was used to validate the results of genome array, and the results were consistent with the obtained data. In conclusion, treatment of curcumin affects the expression of genes involved in various cellular functions and plays an important role in tumor metastasis and apoptosis. Thus, curcumin might be an effective chemopreventive agent for retinoblastoma cancer.

Revisiting the seed and soil in cancer metastasis

Metastasis remains the overwhelming cause of death for cancer patients. During metastasis, cancer cells will leave the primary tumor, intravasate into the bloodstream, arrest at a distant organ, and eventually develop into gross lesions at the secondary sites. This intricate process is influenced by innumerable factors and complex cellular interactions described in 1889 by Stephen Paget as the seed and soil hypothesis. In this review, we revisit this seed and soil hypothesis with an emerging understanding of the cancer cell (i.e. seed) and its microenvironment (i.e. soil). We will provide background to suggest that a critical outcome of the seed-soil interaction is resistance of the stresses that would otherwise impede metastasis.

The genomic response of the ipsilateral and contralateral cortex to stroke in aged rats

Aged rats recover poorly after unilateral stroke, whereas young rats recover readily possibly with the help from the contralateral, healthy hemisphere. In this study we asked whether anomalous, age-related changes in the transcriptional activity in the brains of aged rats could be one underlying factor contributing to reduced functional recovery. We analysed gene expression in the periinfarct and contralateral areas of 3-month- and 18-month-old Sprague Dawley rats. Our experimental end-points were cDNA arrays containing genes related to hypoxia signalling, DNA damage and apoptosis, cellular response to injury, axonal damage and re-growth, cell lineage differentiation, dendritogenesis and neurogenesis. The major transcriptional events observed were: (i) Early up-regulation of DNA damage and down-regulation of anti-apoptosis-related genes in the periinfarct region of aged rats after stroke; (ii) Impaired neurogenesis in the periinfarct area, especially in aged rats; (iii) Impaired neurogenesis in the contralateral (unlesioned) hemisphere of both young and aged rats at all times after stroke and (iv) Marked up-regulation, in aged rats, of genes associated with inflammation and scar formation. These results were confirmed with quantitative real-time PCR. We conclude that reduced transcriptional activity in the healthy, contralateral hemisphere of aged rats in conjunction with an early up-regulation of DNA damage-related genes and pro-apoptotic genes and down-regulation of axono- and neurogenesis in the periinfarct area are likely to account for poor neurorehabilitation after stroke in old rats.