Functional gene expression profile underlying methotrexate-induced senescence in human colon cancer cells

Identification of fibroblast-related genes based on single-cell and machine learning to predict the prognosis and endocrine metabolism of pancreatic cancer

Background

Single-cell sequencing technology has become an indispensable tool in tumor mechanism and heterogeneity studies. Pancreatic adenocarcinoma (PAAD) lacks early specific symptoms, and comprehensive bioinformatics analysis for PAAD contributes to the developmental mechanisms.

Methods

We performed dimensionality reduction analysis on the single-cell sequencing data GSE165399 of PAAD to obtain the specific cell clusters. We then obtained cell cluster-associated gene modules by weighted co-expression network analysis and identified tumorigenesis-associated cell clusters and gene modules in PAAD by trajectory analysis. Tumor-associated genes of PAAD were intersected with cell cluster marker genes and within the signature module to obtain genes associated with PAAD occurrence to construct a prognostic risk assessment tool by the COX model. The performance of the model was assessed by the Kaplan-Meier (K-M) curve and the receiver operating characteristic (ROC) curve. The score of endocrine pathways was assessed by ssGSEA analysis.

Results

The PAAD single-cell dataset GSE165399 was filtered and downscaled, and finally, 17 cell subgroups were filtered and 17 cell clusters were labeled. WGCNA analysis revealed that the brown module was most associated with tumorigenesis. Among them, the brown module was significantly associated with C11 and C14 cell clusters. C11 and C14 cell clusters belonged to fibroblast and circulating fetal cells, respectively, and trajectory analysis showed low heterogeneity for fibroblast and extremely high heterogeneity for circulating fetal cells. Next, through differential analysis, we found that genes within the C11 cluster were highly associated with tumorigenesis. Finally, we constructed the RiskScore system, and K-M curves and ROC curves revealed that RiskScore possessed objective clinical prognostic potential and demonstrated consistent robustness in multiple datasets. The low-risk group presented a higher endocrine metabolism and lower immune infiltrate state.

Conclusion

We identified prognostic models consisting of APOL1, BHLHE40, CLMP, GNG12, LOX, LY6E, MYL12B, RND3, SOX4, and RiskScore showed promising clinical value. RiskScore possibly carries a credible clinical prognostic potential for PAAD.

Knockdown of Lamin B1 and the Corresponding Lamin B Receptor Leads to Changes in Heterochromatin State and Senescence Induction in Malignant Melanoma

Modifications in nuclear structures of cells are implicated in several diseases including cancer. They result in changes in nuclear activity, structural dynamics and cell signalling. However, the role of the nuclear lamina and related proteins in malignant melanoma is still unknown. Its molecular characterisation might lead to a deeper understanding and the development of new therapy approaches. In this study, we analysed the functional effects of dysregulated nuclear lamin B1 (LMNB1) and its nuclear receptor (LBR). According to their cellular localisation and function, we revealed that these genes are crucially involved in nuclear processes like chromatin organisation. RNA sequencing and differential gene expression analysis after knockdown of LMNB1 and LBR revealed their implication in important cellular processes driving ER stress leading to senescence and changes in chromatin state, which were also experimentally validated. We determined that melanoma cells need both molecules independently to prevent senescence. Hence, downregulation of both molecules in a BRAF^V600E melanocytic senescence model as well as in etoposide-treated melanoma cells indicates both as potential senescence markers in melanoma. Our findings suggest that LMNB1 and LBR influence senescence and affect nuclear processes like chromatin condensation and thus are functionally relevant for melanoma progression.

MiR-654-3p Constrains Proliferation, Invasion, and Migration of Sinonasal Squamous Cell Carcinoma via CREB1/PSEN1 Regulatory Axis

Background: MiR-654-3p can repress malignant progression of cancer cells, whereas no relative reports were about its modulatory mechanism in sinonasal squamous cell carcinoma (SNSCC). This research committed to approaching modulatory effect of miR-654-3p on SNSCC cells. Methods: Bioinformatics methods were utilized for analyzing interaction of miR-654-3p/cAMP-responsive element binding protein 1 (CREB1)/presenilin-1 (PSEN1). Expression levels of miR-654-3p, CREB1, and PSEN1 mRNA were assessed by quantitative real-time polymerase chain reaction. Western blot was completed for level assessment of CREB1, PSEN1, and epithelial-mesenchymal transition-related proteins. The targeted relationship between miR-654-3p and CREB1, or CREB1 and PSEN1 was authenticated via dual-luciferase assay and ChIP assay. A trail of experiments in vitro was used for detection of the effects of miR-654-3p/CREB1/PSEN1 axis on malignant progression of SNSCC cells. Results: CREB1 as the downstream target mRNA of miR-654-3p could activate transcription of its downstream target gene PSEN1. Besides, miR-654-3p could target CREB1 to repress PSEN1 expression, thus restraining proliferation, migration, invasion, epithelial-mesenchymal transition, and hastening apoptosis of SNSCC cells. Conclusion: MiR-654-3p as an antitumor gene targeted CREB1 to hamper malignant progression of SNSCC through miR-654-3p/CREB1/PSEN1 axis.

Inhibition of ERK5 Elicits Cellular Senescence in Melanoma via the Cyclin-Dependent Kinase Inhibitor p21

Melanoma is the deadliest skin cancer with a very poor prognosis in advanced stages. Although targeted and immune therapies have improved survival, not all patients benefit from these treatments. The mitogen-activated protein kinase ERK5 supports the growth of melanoma cells in vitro and in vivo. However, ERK5 inhibition results in cell-cycle arrest rather than appreciable apoptosis. To clarify the role of ERK5 in melanoma growth, we performed transcriptomic analyses following ERK5 knockdown in melanoma cells expressing BRAFV600E and found that cellular senescence was among the most affected processes. In melanoma cells expressing either wild-type or mutant (V600E) BRAF, both genetic and pharmacologic inhibition of ERK5 elicited cellular senescence, as observed by a marked increase in senescence-associated β-galactosidase activity and p21 expression. In addition, depletion of ERK5 from melanoma cells resulted in increased levels of CXCL1, CXCL8, and CCL20, proteins typically involved in the senescence-associated secretory phenotype. Knockdown of p21 suppressed the induction of cellular senescence by ERK5 blockade, pointing to p21 as a key mediator of this process. In vivo, ERK5 knockdown or inhibition with XMD8-92 in melanoma xenografts promoted cellular senescence. Based on these results, small-molecule compounds targeting ERK5 constitute a rational series of prosenescence drugs that may be exploited for melanoma treatment. SIGNIFICANCE: This study shows that targeting ERK5 induces p21-mediated cellular senescence in melanoma, identifying a prosenescence effect of ERK5 inhibitors that may be exploited for melanoma treatment.

Antigen presentation capability and AP-1 activation accompany methotrexate-induced colon cancer cell senescence in the context of aberrant β-catenin signaling

Reversible cellular senescence was demonstrated previously to constitute colon cancer cell response to methotrexate. The current study presents a comparison of two senescent states of colon cancer cells, arrested and reversing, resulting from respectively, 120 h exposure to the drug, and 48 h exposure followed by 96 h regrowth in drug-free media. The upregulation of immunoproteasome subunit-coding genes and the increase in human leukocyte antigen HLA-A/B/C membrane level indicated MHC-I-restricted antigen presentation as common to both senescent states. Nuclear factor NF-κB p65 level decreased and activating protein AP-1: c-Jun, Fra2 and JunB nuclear levels increased in both senescent cell populations. Notably, the increase in AP-1- dependent transcription occurred after 48 h exposure to methotrexate. β-catenin nuclear level increased after 48 h exposure to the drug and remained as such only in senescence-arrested cells. β-catenin level was found uncoupled from the protein phosphorylation status indicating the deregulation of β-catenin signaling in colon cancer cells employed in the study. These findings carry implications for both, a general mechanism of senescence establishment and putative advantages for colon cancer treatment.

Autophagy and senescence in cancer therapy

Tumor cells can undergo diverse responses to cancer therapy. While apoptosis represents the most desirable outcome, tumor cells can alternatively undergo autophagy and senescence. Both autophagy and senescence have the potential to make complex contributions to tumor cell survival via both cell autonomous and cell non-autonomous pathways. The induction of autophagy and senescence in tumor cells, preclinically and clinically, either individually or concomitantly, has generated interest in the utilization of autophagy modulating and senolytic therapies to target autophagy and senescence, respectively. This chapter summarizes the current evidence for the promotion of autophagy and senescence as fundamental responses to cancer therapy and discusses the complexity of their functional contributions to cell survival and disease outcomes. We also highlight current modalities designed to exploit autophagy and senescence in efforts to improve the efficacy of cancer therapy.

Monoamine Oxidase B Expression Correlates with a Poor Prognosis in Colorectal Cancer Patients and Is Significantly Associated with Epithelial-to-Mesenchymal Transition-Related Gene Signatures

Monoamine oxidases (MAOs) including MAOA and MAOB are enzymes located on the outer membranes of mitochondria, which are responsible for catalyzing monoamine oxidation. Recently, increased level of MAOs were shown in several cancer types. However, possible roles of MAOs have not yet been elucidated in the progression and prognosis of colorectal carcinoma (CRC). We therefore analyzed the importance of MAOs in CRC by an in silico analysis and tissue microarrays. Several independent cohorts indicated that high expression of MAOB, but not MAOA, was correlated with a worse disease stage and poorer survival. In total, 203 colorectal adenocarcinoma cases underwent immunohistochemical staining of MAOs, and associations with clinicopathological parameters and patient outcomes were evaluated. We found that MAOB is highly expressed in CRC tissues compared to normal colorectal tissues, and its expression was significantly correlated with a higher recurrence rate and a poor prognosis. Moreover, according to the univariate and multivariate analyses, we found that MAOB could be an independent prognostic factor for overall survival and disease-free survival, and its prognostic value was better than T and N stage. Furthermore, significant positive and negative correlations of MAOB with mesenchymal-type and epithelial-type gene expressions were observed in CRC tissues. According to the highlighted characteristics of MAOB in CRC, MAOB can be used as a novel indicator to predict the progression and prognosis of CRC patients.

Therapy-Induced Senescence: An "Old" Friend Becomes the Enemy

For the past two decades, cellular senescence has been recognized as a central component of the tumor cell response to chemotherapy and radiation. Traditionally, this form of senescence, termed Therapy-Induced Senescence (TIS), was linked to extensive nuclear damage precipitated by classical genotoxic chemotherapy. However, a number of other forms of therapy have also been shown to induce senescence in tumor cells independently of direct genomic damage. This review attempts to provide a comprehensive summary of both conventional and targeted anticancer therapeutics that have been shown to induce senescence in vitro and in vivo. Still, the utility of promoting senescence as a therapeutic endpoint remains under debate. Since senescence represents a durable form of growth arrest, it might be argued that senescence is a desirable outcome of cancer therapy. However, accumulating evidence suggesting that cells have the capacity to escape from TIS would support an alternative conclusion, that senescence provides an avenue whereby tumor cells can evade the potentially lethal action of anticancer drugs, allowing the cells to enter a temporary state of dormancy that eventually facilitates disease recurrence, often in a more aggressive state. Furthermore, TIS is now strongly connected to tumor cell remodeling, potentially to tumor dormancy, acquiring more ominous malignant phenotypes and accounts for several untoward adverse effects of cancer therapy. Here, we argue that senescence represents a barrier to effective anticancer treatment, and discuss the emerging efforts to identify and exploit agents with senolytic properties as a strategy for elimination of the persistent residual surviving tumor cell population, with the goal of mitigating the tumor-promoting influence of the senescent cells and to thereby reduce the likelihood of cancer relapse.

Synergistic Cytotoxicity of Renieramycin M and Doxorubicin in MCF-7 Breast Cancer Cells. Mar Drugs. 2019;17. [PMID: 31527453 PMCID: PMC6780817 DOI: 10.3390/md17090536]

Renieramycin M (RM) is a KCN-stabilized tetrahydroisoquinoline purified from the blue sponge Xestospongia sp., with nanomolar IC₅₀s against several cancer cell lines. Our goal is to evaluate its combination effects with doxorubicin (DOX) in estrogen receptor positive MCF-7 breast cancer cells. MCF-7 cells were treated simultaneously or sequentially with various combination ratios of RM and DOX for 72 h. Cell viability was determined using the MTT assay. Synergism or antagonism was determined using curve-shift analysis, combination index method and isobologram analysis. Synergism was observed with pharmacologically achievable concentrations of DOX when administered simultaneously, but not sequentially. The IC₉₅ values of RM and DOX after combination were reduced by up to four-fold and eight-fold, respectively. To gain insights on the mechanism of synergy, real-time profiling, cell cycle analysis, apoptosis assays, and transcriptome analysis were conducted. The combination treatment displayed a similar profile with DNA-damaging agents and induced a greater and faster cell killing. The combination treatment also showed an increase in apoptosis. DOX induced S and G2/M arrest while RM did not induce significant changes in the cell cycle. DNA replication and repair genes were downregulated commonly by RM and DOX. p53 signaling and cell cycle checkpoints were regulated by DOX while ErbB/PI3K-Akt, integrin and focal adhesion signaling were regulated by RM upon combination. Genes involved in cytochrome C release and interferon gamma signaling were regulated specifically in the combination treatment. This study serves as a basis for in vivo studies and provides a rationale for using RM in combination with other anticancer drugs.

Epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) suppressed the growth of hepatocellular carcinoma cells by promoting Semaphorin 3B(SEMA3B)

AIM

Epidermal growth factor-containing fibulin-like extracellular matrix protein 1(EFEMP1) has been found to be involved in the occurrence and development of many cancers. The relationship between EFEMP1 and the development of hepatocellular carcinoma (HCC) and the molecular mechanism are not fully understood.

METHODS

Real-time polymerase chain reaction (PCR) and tissue microarray were used to detect the expression of EFEMP1 in HCC cell lines and tissue. Methylation-specific PCR assay was used to measure the methylation level of EFEMP1 in HCC cell lines and tissue. To study the function of EFEMP1 on cell function, Huh7 and HepG2 were infected with lentiviral particles expressing EFEMP1. MTT assay and colony formation assay were used to examine the effect of EFEMP1 on cell proliferation. Annexin-VAPC/7-AAD double were used to detect the effect of EFEMP1 on cell apoptosis. To further detect the effect of EFEMP1 on the development of HCC in vivo, we performed the tumor formation experiment in nude mice. Gene chip was used to detect the expression profile of Huh7 and HepG2 overexpressing EFEMP1. To further screen out the differences, GO analysis and pathway analysis were performed. To study the effects of SEMA3B, specific siRNA was used to inhibit the expression of SEMA3B. Chi-squared test and rank sum test were used to analyze the relationship between EFEMP1 expression and HCC clinical characteristic.

RESULTS

The study found that the expression of EFEMP1 was significantly decreased in HCC cell lines and HCC tissues. The expression level of EFEMP1 was related to the TNM (the extent of the tumor, the extent of spread to the lymph nodes, the presence of metastasis) stage and the prognosis of patients with HCC. The decrease of protein expression suggested that the patient prognosis was worse, and the protein level of EFEMP1 may be an independent factor in the prognosis of HCC patients. Promoter methylation may be one of the reasons for EFEMP1 inhibition. EFEMP1 could inhibit the proliferation of HCC cells and promoted the apoptosis of HCC cells to regulate the development of HCC. And EFEMP1 promoted the apoptosis of HCC cells mainly through the mitochondrial apoptosis pathway. EFEMP1 may inhibit the proliferation of HCC cells through the SEMA3B gene in the Axon guidance pathway.

CONCLUSION

In summary, our research revealed the regulation of EFEMP1 on cell proliferation and apoptosis in HCC. EFEMP1 may suppress the growth of HCC cells by promoting SEMA3B.

Impact of ERK5 on the Hallmarks of Cancer

Extracellular signal-regulated kinase 5 (ERK5) belongs to the mitogen-activated protein kinase (MAPK) family that consists of highly conserved enzymes expressed in all eukaryotic cells and elicits several biological responses, including cell survival, proliferation, migration, and differentiation. In recent years, accumulating lines of evidence point to a relevant role of ERK5 in the onset and progression of several types of cancer. In particular, it has been reported that ERK5 is a key signaling molecule involved in almost all the biological features of cancer cells so that its targeting is emerging as a promising strategy to suppress tumor growth and spreading. Based on that, in this review, we pinpoint the hallmark-specific role of ERK5 in cancer in order to identify biological features that will potentially benefit from ERK5 targeting.

The LncRNA H19/miR-193a-3p axis modifies the radio-resistance and chemotherapeutic tolerance of hepatocellular carcinoma cells by targeting PSEN1

This study was designated to verify if the lncRNA H19/miR-193a-3p axis would play a regulatory role in the radio-/chemo-resistances of HCC cells through targeting PSEN1. Within the study, five human HCC cell lines were prepared, including Bel-7402, HepG2, Hep3b, QGY-7703, and SMMC-7721. Moreover, docetaxel (DT), paclitaxel (Pt), vinorelbine (Vb), and 5-fluorouracil (5-Fu) were managed as the chemo-therapeutics, and single-dose X-rays were performed as radio-therapies. Besides, lncRNA H19 and miR-193a-3p were detected by qRT-PCR and Western blot were implemented to quantify the expressional levels of PSEN1, Ku80, γ-H2AX, and RAD51. Luciferase reporter gene assay was advanced to verify the targeted relationship between lncRNA H19 and miR-193a-3p. As a consequence, QGY-7703 and Bel-7402 were, respectively, the most radiation-sensitive and radiation-proof cell lines, and Bel-7402 was associated with the highest resistances to DT, Pt, Vb, and 5-FU. The restrained lncRNA H19 and over-expressed miR-193a-3p expressions tended to significantly elevate the survival rate and proliferation of Bel-7402 cells, when they were exposed to radiation and subject to chemo-therapies. The lncRNA H19 was also found to directly target miR-193a-3p in inducing the HCC development. PSEN1 appeared to be subject to the modification of lncRNA H19 and miR-193a-3p in its acting on the survival rates and proliferative abilities of HCC cells. The lncRNA H19/miR-193a-3p/PSEN1 axis could be regarded as the treatment targets for HCC, so as to further improve the treatment efficacy of chemo- and radio-therapies for HCC.

Proteomic analysis indicates the importance of TPM3 in esophageal squamous cell carcinoma invasion and metastasis

Numerous esophageal squamous cell carcinoma (ESCC) patients exhibit tumor recurrence following radical resection. Invasion and metastasis are key factors in poor prognosis following esophagectomy. In the present study, two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used to define patterns of protein expression in ESCC tissues at different pathological stages. The expression levels of identified proteins were determined by immunohistochemistry and western blotting. A total of fifteen protein spots with >2-fold differences were observed when comparing results of 2-DE for stage III and stage I ESCC tissue sample. A total of 12 proteins were identified by mass spectrometry analysis and database searches. The results of immunohistochemistry and western blotting demonstrated expression levels of tropomyosin 3 (TPM3) were higher in stage III ESCC tissue compared with stage I (P<0.05). The findings of the present study identified twelve proteins, which are closely associated with ESCC invasion and metastasis, apoptosis and cell signal transduction. Furthermore, the overexpression of TPM3 may be important in ESCC invasion and metastasis.

Clinical Implications of Hepatocyte Growth Factor, Interleukin-20, and Interleukin-22 in Serum and Bronchoalveolar Fluid of Patients with Non-Small Cell Lung Cancer

Hepatocyte growth factor (HGF) is involved in tumorigenesis, interleukin-20 (IL-20) is an inhibitor of angiogenesis, and interleukin-22 (IL-22) stimulates tumor growth. The aim of this study was to determine the level of HGF, IL-20, and IL-22 in both serum and bronchoalveolar lavage fluid (BALF) of non-small cell lung cancer (NSCLC) patients before onset of chemotherapy, the nature of the interrelationships between these markers, and their prognostic significance regarding post-chemotherapy survival time. We studied 46 NSCLC patients and 15 healthy subjects as a control group. We found significantly higher serum levels of HGF and IL-22 in the NSCLC patients than those in controls [pg/ml: HGF - 1911 (693-6510) vs. 1333 (838-3667), p = 0.0004; IL-22 - 10.66 (1.44-70.34) vs. 4.69 (0.35-12.29), p = 0.0007]. In contrast, concentrations of HGF and IL-22 in BALF were lower in NSCLC patients than those in controls [pg/ml: HGF - 72 (6-561) vs. 488 (14-2003), p = 0.0002; IL-22 - 2.28 (0.70-6.52) vs. 3.72 (2.76-5.64), p = 0.002]. In the NSCLC patients, there was a negative correlation between the serum level of IL-20 and time to tumor progression (r = -0.405, p = 0.04) and between the serum level of HGF and survival time (r = -0.41, p = 0.005). In addition, a higher serum level of HGF and a higher BALF level of IL-22 in patients were linked with a shorter overall survival. We conclude that HGF, IL-20, and IL-22 in the serum and BALF of NSCLC patients before chemotherapy may be a prognostic of cancer progression.

The role of the IL-22/IL-22R1 axis in cancer

Interleukin-22 (IL-22) is an IL-10 family cytokine produced by T cells and innate lymphoid cells. The IL-22 signaling pathway orchestrates mucosal immune defense and tissue regeneration through pleiotropic effects including pro-survival signaling, cell migration, dysplasia and angiogenesis. While these functions can prevent initial establishment of tumors, they can also be hijacked by aggressive cancers to enhance tumor growth and metastasis. Thus, the role of the IL-22/IL-22R1 axis in cancer is complex and context-specific. Evidence of IL-22 involvement manifests as dysregulation of IL-22 expression and signaling in patients with many common cancers including those of the gut, skin, lung and liver. Unlike other cancer-associated cytokines, IL-22 has restricted tissue specificity as its unique receptor IL-22R1 is exclusively expressed on epithelial and tissue cells, but not immune cells. This makes it an attractive target for therapy as there is potential achieve anti-tumor immunity with fewer side effects. This review summarizes current findings on functions of IL-22 in association with general mechanisms for tumorigenesis as well as specific contributions to particular cancers, and ponders how best to approach further research in the field.

Investigation of a novel biomarker, neuropilin-1, and its application for poor prognosis in acute myeloid leukemia patients

According to the previous studies, numerous biomarkers impact on the prognosis of acute myeloid leukemia (AML) and the prediction for AML had been improved tremendously in the past decades. However, accurate risk-stratification at diagnosis or prognosis remained difficult. In order to further investigate the prognosis evaluation biomarker, the transcription or expression of neuropilin-1 (NRP-1) in 87 AML patients and 32 non-malignant controls were examined. Real-time quantitative polymerase chain reaction (RT-PCR) and Western blot were used to detect the NRP-1 expression. Clinical data were collected and analyzed for the 87 AML patients. The results indicated that high NRP-1 expression discriminated the complete remission (CR) rate of AML patients (22.12 % vs. 68.04 % for AML, P < 0.01). De novo AML patients tended to express higher NRP-1 proteins than relapsed AML patients. The overall survival (OS) and relapse-free survival (RFS) rate of the high NRP-1 expression patients decreased significantly compared with the low NRP-1 expression patients (P < 0.001). NRP-1 was revealed to be an independent risk factor for OS in AML (P = 0.003). In conclusion, NRP-1 could predict the shorter OS and RFS rate, and also related with the CR response in AML. Therefore, NRP-1 may act as a more aggressive and promising predictor for the poor prognosis of AML.

Differential gene expression profile of first-generation and second-generation rapamycin-resistant allogeneic T cells

BACKGROUND AIMS

We completed a phase II clinical trial evaluating rapamycin-resistant allogeneic T cells (T-rapa) and now have evaluated a T-rapa product manufactured in 6 days (T-rapa(6)) rather than 12 days (T-Rapa(12)).

METHODS

Using gene expression microarrays, we addressed our hypothesis that the two products would express a similar phenotype. The products had similar phenotypes using conventional comparison methods of cytokine secretion and surface markers.

RESULTS

Unsupervised analysis of 34,340 genes revealed that T-rapa(6) and T-rapa(12) products clustered together, distinct from culture input CD4(+) T cells. Statistical analysis of T-rapa(6) products revealed differential expression of 19.3% of genes (n = 6641) compared with input CD4(+) cells; similarly, 17.8% of genes (n = 6147) were differentially expressed between T-rapa(12) products and input CD4(+) cells. Compared with input CD4(+) cells, T-rapa(6) and T-rapa(12) products were similar in terms of up-regulation of major gene families (cell cycle, stress response, glucose catabolism, DNA metabolism) and down-regulation (inflammatory response, immune response, apoptosis, transcriptional regulation). However, when directly compared, T-rapa(6) and T-rapa(12) products showed differential expression of 5.8% of genes (n = 1994; T-rapa(6) vs. T-rapa(12)).

CONCLUSIONS

Second-generation T-rapa(6) cells possess a similar yet distinct gene expression profile relative to first-generation T-rapa(12) cells and may mediate differential effects after adoptive transfer.

The effect of systemic chemotherapy on neurogenesis, plasticity and memory

Chemotherapy has been enormously successful in treating many forms of cancer and improving patient survival rates. With the increasing numbers of survivors, a number of cognitive side effects have become apparent. These have been called "chemobrain" or "chemofog" among patient groups, who describe the symptoms as a decline in memory, concentration and executive functions. Changes which, although subtle, can cause significant distress among patients and prevent a return to the quality of life experienced before treatment. This cognitive side effect of chemotherapy was not anticipated as it had been assumed that chemotherapy agents, administered systematically, could not cross the blood-brain barrier and that the brain was therefore protected from their action. It is now realised that low concentrations of many chemotherapy agents cross the blood-brain barrier and even those that are completely prevented from doing so, can induce the production of inflammatory cytokines in peripheral tissues which in turn can cross the blood-brain barrier and impact on the brain. A large number of patient studies have shown that cognitive decline is found in a proportion of patients treated with a variety of chemotherapy agents for different types of cancer. The deficits experienced by these patients can last for up to several years and have a deleterious effect on educational attainment and ability to return to work. Imaging studies of patients after systemic chemotherapy show that this treatment produces structural and functional changes in the brain some of which seem to persist even when the cognitive deficits have ceased. This suggests that, with time, brain plasticity may be able to compensate for the deleterious effects of chemotherapy treatment. A number of mechanisms have been suggested for the changes in brain structure and function found after chemotherapy. These include both central and peripheral inflammatory changes, demyelination of white matter tracts, a reduction in stem cell proliferation in both the hippocampal neurogenic region and by oligodendrocyte precursors as well as changes in hormonal or growth factor levels. A number of possible treatments have been suggested which range from pharmacological interventions to cognitive behavioural therapies. Some of these have only been tested in animal models while others have produced varying degrees of improvement in patient populations. Currently, there is no recognised treatment and a greater understanding of the causes of the cognitive decline experienced after chemotherapy will be key to finding ways of preventing or treating the effects of chemobrain.