Arthur W. Lambert

Epigenetic dysregulation of HTR2A in the brain of patients with schizophrenia and bipolar disorder

INTRODUCTION HTR2A gene has been the subject of numerous studies in psychiatric genetics because LSD, which resembles serotonin causes psychosis and atypical antipsychotic drugs target the HTR2A receptor. However, evidence for the role of HTR2A polymorphism(s) in schizophrenia (SCZ) and bipolar disorder (BD) has been elusive. We hypothesized that epigenetic dysregulation of HTR2A may be involved in psycho-pathogenesis and analyzed promoter DNA methylome and expression of HTR2A in SCZ, BD and control subjects. METHOD DNA derived from post-mortem brains of patients with SCZ and BD and matched control subjects (each 35) were obtained from the Stanley Medical Research Institute. While bisulfite DNA sequencing was used to screen and quantify cytosine methylation in the HTR2A promoter, corresponding gene expression was analyzed by qRT-PCR. RESULTS We found strong evidence for epigenetic fine-tuning of HTR2A expression. In general, the expression of HTR2A in individuals carrying the C allele of T102C (or G allele of -1438A/G polymorphism) was higher than TT genotype. Interestingly, promoter DNA of HTR2A was hypermethylated at and around the -1438A/G polymorphic site, but was hypomethylated at and around T102C polymorphic site in SCZ and BD compared to the controls. Furthermore, epigenetic down-regulation of HTR2A was associated with early age of disease onset in SCZ and BD. CONCLUSION Epigenetic dysregulation of HTR2A may contribute to SCZ, BD and earlier age of disease onset. Further research is required to delineate the dysregulation of other components of serotoninergic pathway to design new therapeutics based on the downstream effects of serotonin.

DNA hypermethylation of serotonin transporter gene promoter in drug naïve patients with schizophrenia.

INTRODUCTION Dysfunctional serotonin signaling has been linked to the pathogenesis of autism, obsessive compulsive disorder, mood disorders and schizophrenia. While the hypo-activity of serotonin signaling is involved in the pathogenesis of depression, anxiety and obsessive compulsive disorder; LSD, an agonist of serotonin type 2 receptor (5-HTR2A) induces psychosis. Therefore, anxiety and depressive disorders are treated by SSRIs which inhibit serotonin transporter (5-HTT) while psychotic disorders are controlled by drugs that block serotonin and/or dopamine receptors. Since genetic polymorphisms and epigenetic dysregulation of 5-HTT are involved in the pathogenesis of mental diseases, we analyzed DNA methylation of 5-HTT promoter in post-mortem brains and saliva samples of patients with schizophrenia (SCZ) and bipolar disorder (BD) to evaluate its potential application as a diagnostic and/or therapeutic biomarker in SCZ and BD. METHODS Whole genome DNA methylation profiling was performed for a total of 24 samples (including two saliva samples) using the Illumina 27K (for 12 samples) and 450K DNA methylation array platform (for another 12 samples), followed by bisulfite sequencing to identify candidate CpGs for further analysis. Quantitative methylation specific PCR (qMSP) was used to assess the degree of CpG methylation of 5-HTT promoter in 105 post-mortem brains (35 controls, 35 SCZ and 35 BD) and 100 saliva samples (30 controls, 30 SCZ, 20 BD and 20 first degree relatives of SCZ or BD). The U133 2.0 Plus Human Transcriptome array for a total of 30 post-mortem brain samples (each group 10) followed by quantitative real-time PCR was used to study 5-HTT expression in 105 post-mortem brain samples. RESULTS The qMSP analysis for 5-HTT promoter region showed DNA hypermethylation in post-mortem brain samples of SCZ patients (~30%), particularly in drug free patients (~60%, p=0.04). Similarly, there was a trend for DNA hypermethylation in antipsychotic free BD patients (~50%, p=0.066). qMSP analysis of DNA extracted from the saliva samples also exhibited hypermethylation of 5-HTT promoter in patients with SCZ (~30%, p=0.039), which was more significant in drug naïve SCZ patients (>50%, p=0.0025). However, the difference was not significant between the controls and unaffected first degree relatives of patients with SCZ (p=0.37) and versus patients using antipsychotic drugs (p=0.2). The whole genome transcriptome analysis of post-mortem brain samples showed reduced expression of 5-HTT in SCZ compared to the control subjects (~50%, p=0.008), confirmed by quantitative real-time PCR analysis (~40%, p=0.035) which was more significant in drug free SCZ patients (~70%, p=0.022). CONCLUSION A correlation between reduction in 5-HTT expression and DNA hypermethylation of the 5-HTT promoter in drug naïve SCZ patients suggests that an epigenetically defined hypo-activity of 5-HTT may be linked to SCZ pathogenesis. Furthermore, this epigenetic mark in DNA extracted from saliva can be considered as one of the key determinants in a panel of diagnostic and/or therapeutic biomarkers for SCZ.

Targeting IL13Ralpha2 activates STAT6-TP63 pathway to suppress breast cancer lung metastasis

IntroductionBasal-like breast cancer (BLBC) is an aggressive subtype often characterized by distant metastasis, poor patient prognosis, and limited treatment options. Therefore, the discovery of alternative targets to restrain its metastatic potential is urgently needed. In this study, we aimed to identify novel genes that drive metastasis of BLBC and to elucidate the underlying mechanisms of action.MethodsAn unbiased approach using gene expression profiling of a BLBC progression model and in silico leveraging of pre-existing tumor transcriptomes were used to uncover metastasis-promoting genes. Lentiviral-mediated knockdown of interleukin-13 receptor alpha 2 (IL13Ralpha2) coupled with whole-body in vivo bioluminescence imaging was performed to assess its role in regulating breast cancer tumor growth and lung metastasis. Gene expression microarray analysis was followed by in vitro validation and cell migration assays to elucidate the downstream molecular pathways involved in this process.ResultsWe found that overexpression of the decoy receptor IL13Ralpha2 is significantly enriched in basal compared with luminal primary breast tumors as well as in a subset of metastatic basal-B breast cancer cells. Importantly, breast cancer patients with high-grade tumors and increased IL13Ralpha2 levels had significantly worse prognosis for metastasis-free survival compared with patients with low expression. Depletion of IL13Ralpha2 in metastatic breast cancer cells modestly delayed primary tumor growth but dramatically suppressed lung metastasis in vivo. Furthermore, IL13Ralpha2 silencing was associated with enhanced IL-13-mediated phosphorylation of signal transducer and activator of transcription 6 (STAT6) and impaired migratory ability of metastatic breast cancer cells. Interestingly, genome-wide transcriptional analysis revealed that IL13Ralpha2 knockdown and IL-13 treatment cooperatively upregulated the metastasis suppressor tumor protein 63 (TP63) in a STAT6-dependent manner. These observations are consistent with increased metastasis-free survival of breast cancer patients with high levels of TP63 and STAT6 expression and suggest that the STAT6-TP63 pathway could be involved in impairing metastatic dissemination of breast cancer cells to the lungs.ConclusionOur findings indicate that IL13Ralpha2 could be used as a promising biomarker to predict patient outcome and provide a rationale for assessing the efficacy of anti-IL13Ralpha2 therapies in a subset of highly aggressive basal-like breast tumors as a strategy to prevent metastatic disease.

Integrin Signaling in Mammary Epithelial Cells and Breast Cancer

Cells sense and respond to the extracellular matrix (ECM) by way of integrin receptors, which facilitate cell adhesion and intracellular signaling. Advances in understanding the mammary epithelial cell hierarchy are converging with new developments that reveal how integrins regulate the normal mammary gland. But in breast cancer, integrin signaling contributes to the development and progression of tumors. This paper highlights recent studies which examine the role of integrin signaling in mammary epithelial cells and their malignant counterparts.

hBub1 negatively regulates p53 mediated early cell death upon mitotic checkpoint activation

Our previous studies showed that the depletion of the outer kinetochore protein hBub1 upon activation of spindle assembly checkpoint (SAC) primarily triggers early cell death mediated by p53 rather than aneuploidy. Here, we report that phosphorylation of p53 at the Ser 37 is critical for its proapoptotic activity upon SAC activation. Furthermore, we show that p53 physically interacts with hBub1 at kinetochores in response to mitotic spindle damage suggesting a direct role for hBub1 in the suppression of p53 mediated cell death. This observation is further substantiated by the inhibition of p53 mediated transactivation of the proapoptotic target genes, PUMA and BAX, by hBub1 in SAC activated cells. In summary, our data from these and our previous studies strongly suggest that in response to SAC activation, hBub1 acts as a negative regulator of p53 mediated early cell death in a novel checkpoint pathway. On the translational medicine front, it is tempting to speculate that by disabling the hBub1 in p53 proficient cancer cells, apoptosis may be induced as a therapeutic approach to eradicate the tumor cells.

SDPR functions as a metastasis suppressor in breast cancer by promoting apoptosis

Significance Discovery of novel metastasis suppressor genes in breast cancer using genomic efforts has been limited, potentially due to overlooking their regulation by epigenetic mechanisms. We report the discovery of SDPR as a novel metastasis suppressor gene localized to 2q32-33, a region associated with significant loss of heterozygosity in breast cancer, using comparative gene expression analysis of a breast cancer progression model system in conjunction with in silico metaanalysis of publicly available datasets. SDPR is silenced epigenetically by promoter DNA methylation and its loss of expression correlates with significantly reduced distant-metastasis–free and relapse-free survival of breast cancer patients. Overexpression of SDPR reduces cell migration and intravasation/extravasation potential, favors cell death, and suppresses experimental lung metastasis of breast cancer cells. Metastatic dissemination of breast cancer cells represents a significant clinical obstacle to curative therapy. The loss of function of metastasis suppressor genes is a major rate-limiting step in breast cancer progression that prevents the formation of new colonies at distal sites. However, the discovery of new metastasis suppressor genes in breast cancer using genomic efforts has been slow, potentially due to their primary regulation by epigenetic mechanisms. Here, we report the use of model cell lines with the same genetic lineage for the identification of a novel metastasis suppressor gene, serum deprivation response (SDPR), localized to 2q32-33, a region reported to be associated with significant loss of heterozygosity in breast cancer. In silico metaanalysis of publicly available gene expression datasets suggests that the loss of expression of SDPR correlates with significantly reduced distant-metastasis–free and relapse-free survival of breast cancer patients who underwent therapy. Furthermore, we found that stable SDPR overexpression in highly metastatic breast cancer model cell lines inhibited prosurvival pathways, shifted the balance of Bcl-2 family proteins in favor of apoptosis, and decreased migration and intravasation/extravasation potential, with a corresponding drastic suppression of metastatic nodule formation in the lungs of NOD/SCID mice. Moreover, SDPR expression is silenced by promoter DNA methylation, and as such it exemplifies epigenetic regulation of metastatic breast cancer progression. These observations highlight SDPR as a potential prognostic biomarker and a target for future therapeutic applications.

hBub1 deficiency triggers a novel p53 mediated early apoptotic checkpoint pathway in mitotic spindle damaged cells

It has been universally believed that spindle assembly checkpoint (SAC) proteins which include the kinetochore proteins are involved in monitoring the faithful segregation of sister chromatids during cell division and hence defects in these proteins result in anueploidy. Furthermore, there are multiple sources of experimental data to suggest that a defect in p53 could also promote genomic instability leading to anueploidy. Despite these observations, a molecular basis for the prevention of aneuploidy to maintain genomic integrity upon activation of SAC has largely remained elusive. In this report, we demonstrate a novel mechanism for the maintenance of a balance between cell survival and apoptosis upon activation of SAC. We found that depletion of the outer kinetochore protein hBub1 upon activation of SAC primarily triggers early cell death mediated by p53. This phenomenon is further supported by the up-regulation of p53 down-stream pro-apoptotic genes, BAX and PUMA as well as a corresponding increase in the cleavage products of PARP and caspase 3, markers of apoptosis upon depletion of hBub1 in SAC activated cells. On the other hand, as expected, concomitant loss of both hBub1 and p53 resulted in disabling of the p53 mediated cell death pathway leading to the accumulation of cells with aneuploidy/polyploidy. Commentary also to: hBub1 negatively regulates p53 mediated early cell death upon mitotic checkpoint activation Fangming Gao, Jose F Ponte, Panagiotis Papageorgis, Mary Levy, Sait Ozturk, Arthur W. Lambert, Arunthathi Thiagalingam, Hamid Mostafavi Abdolmaleky, Beth A Sullivan and Sam Thiagalingam

Tumor Cell-Derived Periostin Regulates Cytokines That Maintain Breast Cancer Stem Cells.

Basal-like breast cancer (BLBC) is an aggressive subtype of breast cancer which is often enriched with cancer stem cells (CSC), but the underlying molecular basis for this connection remains elusive. We hypothesized that BLBC cells are able to establish a niche permissive to the maintenance of CSCs and found that tumor cell-derived periostin (POSTN), a component of the extracellular matrix, as well as a corresponding cognate receptor, integrin αvβ3, are highly expressed in a subset of BLBC cell lines as well as in CSC-enriched populations. Furthermore, we demonstrated that an intact periostin–integrin β3 signaling axis is required for the maintenance of breast CSCs. POSTN activates the ERK signaling pathway and regulates NF-κB–mediated transcription of key cytokines, namely IL6 and IL8, which in turn control downstream activation of STAT3. In summary, these findings suggest that BLBC cells have an innate ability to establish a microenvironmental niche supportive of CSCs. Implications: The findings reported here indicate that POSTN produced by CSCs acts to reinforce the stem cell state through the activation of integrin receptors and the production of key cytokines. Mol Cancer Res; 14(1); 103–13. ©2015 AACR.

Abstract P1-06-13: Periostin controls cytokine production to maintain breast cancer stem cells

Recent evidence suggests that the molecular heterogeneity inherent to breast cancer, which underlies metastasis, resistance to treatment and disease recurrence, can be driven by a distinct subpopulation of tumor cells referred to as cancer stem cells (CSCs). Basal-like breast cancer represents a particularly aggressive disease subtype and the tumor cells share phenotypic similarities to breast cancer stem cells. However, the extracellular cues and intracellular pathways that CSCs rely on remain unclear. Working with a breast cancer progression model system we found the invasive breast cancer cell line to exhibit numerous stem-like characteristics. Gene expression profiling, along with a careful review of the literature, identified a secreted extracellular matrix molecule, periostin (POSTN), which we hypothesized to be required for the maintenance of a cancer stem cell state. POSTN expression was increased in numerous basal-like breast cancer cell lines, as well as in cells grown as mammospheres and in the CD44+/CD24- fraction of tumor cells. Furthermore, CSC-like lines displayed increased surface levels of the integrin alpha-v beta-3 heterodimer, a known receptor for POSTN, suggesting that hyperactivation of a POSTN signaling axis could potentially regulate the CSC state. Using stable cell lines expressing an shRNA directed at POSTN or ITGB3 we have found that POSTN signaling is required for efficient mammosphere formation and for the maintenance of an ALDH-positive CSC population. Disruption of this signaling axis resulted in decreased production of cytokines, including IL-6 and IL-8 - known regulators of CSCs - as well as downstream STAT3 signaling. Furthermore, high POSTN expression is associated with a worse clinical prognosis in ER-negative breast cancer. Therefore, we suggest that POSTN signaling through integrin receptors may enrich for highly tumorigenic breast CSCs in a subset of basal-like tumors, leading to aggressive and recurrent malignancies. This reveals a previously unknown link between POSTN signaling and cytokine production, and suggests that basal-like cancers can establish a microenvironmental niche supportive of cancer stem cells. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-06-13.

Abstract 4890: Periostin signaling regulates breast cancer stem cells.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Recent evidence suggests that the molecular heterogeneity inherent to breast cancer, which underlies metastasis, resistance to treatment and disease recurrence, can be driven by a distinct subpopulation of tumor cells referred to as cancer stem cells (CSCs). However, the extracellular cues and intracellular pathways that CSCs rely on remain unclear. Working with a breast cancer progression model system we found the invasive breast cancer cell line to exhibit numerous stem-like characteristics. Gene expression profiling, along with a careful review of the literature, identified a secreted extracellular matrix molecule, periostin (POSTN), which we hypothesized to be required for the maintenance of a cancer stem cell state. POSTN expression was increased in numerous basal-like breast cancer cell lines that contain an expanded CSC population, as well as in cells grown as mammospheres and in the CD44+/CD24- fraction of tumor cells. Furthermore, CSC-like lines displayed increased surface levels of the alpha-v beta-3 integrin heterodimer, a known receptor for POSTN, suggesting that hyperactivation of a POSTN signaling axis could potentially regulate the CSC state. Using stable cell lines expressing an shRNA directed at POSTN we have found that POSTN is required for efficient mammosphere formation and for the maintenance of an ALDH-positive CSC population. In line with this, we found these cells had impaired Erk and Wnt signaling and expressed less IL-6 and IL-8, known regulators of CSCs. Furthermore, high POSTN expression correlates with a worse clinical prognosis in basal-like breast cancer patients. Therefore, we suggest that POSTN signaling through integrin receptors may enrich for highly tumorigenic breast CSCs in a subset of basal-like tumors, leading to aggressive and recurrent malignancies. More broadly, our results imply that a supportive tumor niche can be established and maintained by cancer cells, and raises the possibility of targeting components of this extracellular environment to eradicate breast CSCs. Citation Format: Arthur W. Lambert, Sait Ozturk, Panos Papageorgis, Hamid Abdolmaleky, Sam Thiagalingam. Periostin signaling regulates breast cancer stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4890. doi:10.1158/1538-7445.AM2013-4890