Glucocorticoid Receptor Regulates and Interacts with LEDGF/p75 to Promote Docetaxel Resistance in Prostate Cancer Cells

Patients with advanced prostate cancer (PCa) invariably develop resistance to anti-androgen therapy and taxane-based chemotherapy. Glucocorticoid receptor (GR) has been implicated in PCa therapy resistance; however, the mechanisms underlying GR-mediated chemoresistance remain unclear. Lens epithelium-derived growth factor p75 (LEDGF/p75, also known as PSIP1 and DFS70) is a glucocorticoid-induced transcription co-activator implicated in cancer chemoresistance. We investigated the contribution of the GR-LEDGF/p75 axis to docetaxel (DTX)-resistance in PCa cells. GR silencing in DTX-sensitive and -resistant PCa cells decreased LEDGF/p75 expression, and GR upregulation in enzalutamide-resistant cells correlated with increased LEDGF/p75 expression. ChIP-sequencing revealed GR binding sites in the LEDGF/p75 promoter. STRING protein-protein interaction analysis indicated that GR and LEDGF/p75 belong to the same transcriptional network, and immunochemical studies demonstrated their co-immunoprecipitation and co-localization in DTX-resistant cells. The GR modulators exicorilant and relacorilant increased the sensitivity of chemoresistant PCa cells to DTX-induced cell death, and this effect was more pronounced upon LEDGF/p75 silencing. RNA-sequencing of DTX-resistant cells with GR or LEDGF/p75 knockdown revealed a transcriptomic overlap targeting signaling pathways associated with cell survival and proliferation, cancer, and therapy resistance. These studies implicate the GR-LEDGF/p75 axis in PCa therapy resistance and provide a pre-clinical rationale for developing novel therapeutic strategies for advanced PCa.

Glucocorticoid Receptor and β-Catenin Interact in Prostate Cancer Cells and Their Co-Inhibition Attenuates Tumorsphere Formation, Stemness, and Docetaxel Resistance

Therapy resistance hinders the efficacy of anti-androgen therapies and taxane-based chemotherapy for advanced prostate cancer (PCa). Glucocorticoid receptor (GR) signaling mediates resistance to androgen receptor signaling inhibitors (ARSI) and has also been recently implicated in PCa resistance to docetaxel (DTX), suggesting a role in therapy cross-resistance. Like GR, β-catenin is upregulated in metastatic and therapy-resistant tumors and is a crucial regulator of cancer stemness and ARSI resistance. β-catenin interacts with AR to promote PCa progression. Given the structural and functional similarities between AR and GR, we hypothesized that β-catenin also interacts with GR to influence PCa stemness and chemoresistance. As expected, we observed that treatment with the glucocorticoid dexamethasone promotednuclear accumulation of GR and active β-catenin in PCa cells. Co-immunoprecipitation studies showed that GR and β-catenin interact in DTX-resistant and DTX-sensitive PCa cells. Pharmacological co-inhibition of GR and β-catenin, using the GR modulator CORT-108297 and the selective β-catenin inhibitor MSAB, enhanced cytotoxicity in DTX-resistant PCa cells grown in adherent and spheroid cultures and decreased CD44+/CD24- cell populations in tumorspheres. These results indicate that GR and β-catenin influence cell survival, stemness, and tumorsphere formation in DTX-resistant cells. Their co-inhibition could be a promising therapeutic strategy to overcome PCa therapy cross-resistance.

TSLP as a Potential Therapy in the Treatment of CRLF2 B Cell Acute Lymphoblastic Leukemia

Cytokine receptor-like factor 2 B-cell acute lymphoblastic leukemia (CRLF2 B-ALL) is a high-risk subtype characterized by CRLF2 overexpression with poor survival rates in children and adults. CRLF2 and interleukin-7 receptor alpha (IL-7Rα) form a receptor for the cytokine thymic stromal lymphopoietin (TSLP), which induces JAK/STAT and PI3K/AKT/mTOR pathway signals. Previous studies from our group showed that low TSLP doses increased STAT5, AKT, and S6 phosphorylation and contributed to CRLF2 B-ALL cell survival. Here we investigated the role of TSLP in the survival and proliferation of CRLF2 B-ALL cells in vitro and in vivo. We hypothesized that high doses of TSLP increase CRLF2 signals and contribute to increased proliferation of CRLF2 B-ALL cells in vitro and in vivo. Interestingly, we observed the opposite effect. Specifically, high doses of TSLP induced apoptosis in human CRLF2 B-ALL cell lines in vitro, prevented engraftment of CRLF2 B-ALL cells, and prolonged the survival of +TSLP patient-derived-xenograft mice. Mechanistically, we showed that high doses of TSLP induced loss of its receptor and loss of CRLF2 signals in vitro. These results suggest that high doses of TSLP could be further investigated as a potential therapy for the treatment of CRLF2 B-ALL.

Abstract 399: The glucocorticoid receptor and β-catenin interact in prostate cancer cells and their co-inhibition attenuates stemness and docetaxel resistance

The efficacy of anti-androgen receptor (AR) therapies and taxane-based chemotherapy for the treatment of advanced prostate cancer (PCa) is hindered by the development of therapy resistance. Our previous studies demonstrated that docetaxel (DTX)-resistant PCa cells activates a transcriptomic program associated with stemness and display cancer stem cell (CSC) properties, consistent with the notion that CSCs within prostate tumors contribute to chemoresistance. Glucocorticoid receptor (GR) signaling is a critical mediator of resistance to AR-targeted therapy, and has been recently implicated in the development of PCa cell tumorsphere formation and chemoresistance. Like GR, β-catenin is overexpressed in metastatic and therapy-resistant tumors, and is considered a key regulator of cancer stemness and androgen-targeted therapy resistance. Given the structural and functional overlap between GR and AR, a known interacting partner of β-catenin, we hypothesized that GR also interacts with β-catenin to support stemness and chemoresistance in PCa cells. We observed that treatment with the glucocorticoid dexamethasone induces enhanced nuclear accumulation of both GR and β-catenin in DTX-resistant PCa cells compared to their DTX-sensitive counterparts. Knockdown studies revealed that GR and β-catenin do no regulate each other at the protein level. However, using whole cell and nuclear co-immunoprecipitation, we demonstrated the interaction between GR and β-catenin in both DTX-resistant and DTX-sensitive PC3, DU145, and 22RV1 cells. Pharmacological inhibition and RNA interference-mediated silencing of GR with concomitant inhibition of β-catenin enhanced DTX cytotoxicity in resistant PCa cells grown in both adherent and spheroid cultures, and decreased CD44+/CD24- cell populations in tumorspheres. These results indicate that both GR and β-catenin interact and influence stemness, and may be promising therapeutic targets to overcome PCa chemoresistance.

Citation Format: Shannalee R. Martinez, Catherine C. Elix, Pedro T. Ochoa, Evelyn S. Sanchez-Hernandez, Hossam R. Alkashgari, Greisha L. Ortiz-Hernandez, Lubo Zhang, Carlos A. Casiano. The glucocorticoid receptor and β-catenin interact in prostate cancer cells and their co-inhibition attenuates stemness and docetaxel resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 399.

Abstract 2559: Tumor lipogenesis influences macrophage polarization in advanced prostate cancer

Aberrant lipid metabolism in prostate tumors is linked to aggressive disease and poor outcomes. The purpose of this study was to identify mechanisms by which lipid metabolism in prostate cancer cells influences the tumor immune microenvironment, with emphasis on the activation of macrophages. Our hypothesis that fatty acid synthase-driven de novo lipogenesis promotes immune evasion via alternative M2-like macrophage activation was tested using human monocyte (U937)-derived macrophages co-cultured with prostate cancer cells in the presence of fatty acid synthase inhibitors. Monocytes were differentiated to macrophages in vitro using phorbol-12-myristate-13-acetate for 48 hours prior to co-culture with prostate cancer cells. Macrophage polarization following co-culture with prostate cancer cells was evaluated using multi-parameter flow cytometry to detect established M1 (CD80, CD86) and M2 (CD163, CD206) markers. Furthermore, the expression of fatty acid synthase and pan-macrophage marker CD68 in human prostate tumor tissue microarrays was evaluated using multiplex immunohistochemistry. The lipogenic enzyme and macrophage staining correlated with disease progression, reaching peak levels in metastatic tissues. These findings indicate that tumoral fatty acid synthase is an important mediator of tumor-immune crosstalk, particularly in the context of aggressive and metastatic prostate cancer. These data further suggest that fatty acid synthesis represents a targetable complement to immune-enhancing therapies by modulating tumor cell metabolism, underscoring the need for further evaluation of agents targeting lipid metabolism in prostate cancer.

Citation Format: Shannalee R. Martinez, Carla Barrientos Risso, Ralphdy Vergne, Nathan R. Wall, Julie Dutil, Carlos A. Casiano, Gilberto Ruiz-Deya, Carlos Joel Diaz Osterman. Tumor lipogenesis influences macrophage polarization in advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2559.

Abstract 2460: Oncogenic regulation of lipogenesis in docetaxel resistant prostate cancer cells

Prostate cancer is the second leading cause of cancer related deaths in men in the United States. Docetaxel is the standard chemotherapeutic agent available for patients with advanced prostate cancer, in both hormone sensitive and castration resistant settings. However, the development of resistance to docetaxel curtails the efficacy of the drug in prostate cancer patients. Aberrant lipid metabolism has been linked to poor outcomes and therapy resistance in prostate cancer, particularly through overexpression and activation of lipogenic enzymes including ATP citrate lyase, acetyl coA carboxylase, fatty acid synthase, and stearoyl coA desaturase. Together, these enzymes drive fatty acid biogenesis, which has been linked to docetaxel resistance. The purpose of this study is to delineate the molecular mechanisms underlying the lipogenic reprogramming of docetaxel resistant prostate cancer cells, as these represent targets for reversal of this drug resistance. Docetaxel resistant sublines of LNCaP, 22rv1, PC3 and DU145 cell lines were established through chronic continuous exposure to incrementally increasing concentrations of docetaxel, followed by authentication by single tandem repeat (STR) analysis and validation of resistance using MTT viability assays and immunoblot detection of multidrug resistance protein 1 (MDR1/p glycoprotein/ABCB1). Enhanced intracellular accumulation of lipids using BODIPY 493/593 staining and flow cytometric detection was used to confirm the lipogenic phenotype of docetaxel-resistant cells. Oncogenic cMYC expression was also detected by immunoblotting, and its role in regulating lipogenic enzyme expression was evaluated by siRNA interference in docetaxel resistant prostate cancer sublines. cMYC knockdown suppressed the expression of lipogenic enzymes including acetyl coA carboxylase, fatty acid synthase, and stearoyl CoA desaturase in docetaxel-resistant prostate cancer cells. Furthermore, pharmacological inhibition of cMYC production (JQ1) or activity (10058-F4) effectively resensitized resistant cells to docetaxel, as did targeting of key lipogenic enzymes. These data indicate that a cMYC associated lipogenic program is associated with docetaxel resistance in prostate cancer and may represent targets for interventions to enhance docetaxel response in patients with advanced prostate cancer.

Citation Format: Shannalee R. Martinez, Adrián Pérez Aybar, Carlos J. Díaz Osterman. Oncogenic regulation of lipogenesis in docetaxel resistant prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2460.

Epithelial/mesenchymal heterogeneity of high-grade serous ovarian carcinoma samples correlates with miRNA let-7 levels and predicts tumor growth and metastasis

Patient‐derived samples present an advantage over current cell line models of high‐grade serous ovarian cancer (HGSOC) that are not always reliable and phenotypically faithful models of in vivo HGSOC. To improve upon cell line models of HGSOC, we set out to characterize a panel of patient‐derived cells and determine their epithelial and mesenchymal characteristics. We analyzed RNA and protein expression levels in patient‐derived xenograft (PDX) models of HGSOC, and functionally characterized these models using flow cytometry, wound healing assays, invasion assays, and spheroid cultures. Besides in vitro work, we also evaluated the growth characteristics of PDX in vivo (orthotopic PDX). We found that all samples had hybrid characteristics, covering a spectrum from an epithelial‐to‐mesenchymal state. Samples with a stronger epithelial phenotype were more active in self‐renewal assays and more tumorigenic in orthotopic xenograft models as compared to samples with a stronger mesenchymal phenotype, which were more migratory and invasive. Additionally, we observed an inverse association between microRNA let‐7 (lethal‐7) expression and stemness, consistent with the loss of let‐7 being an important component of the cancer stem cell phenotype. We observed that lower let‐7 levels were associated with the epithelial state and a lower epithelial mesenchymal transition (EMT) score, more efficient spheroid and tumor formation, and increased sensitivity to platinum‐based chemotherapy. Surprisingly, in these HGSOC cells, stemness could be dissociated from invasiveness: Cells with lower let‐7 levels were more tumorigenic, but less migratory, and with a lower EMT score, than those with higher let‐7 levels. We conclude that let‐7 expression and epithelial/mesenchymal state are valuable predictors of HGSOC proliferation, in vitro self‐renewal, and tumor burden in vivo.

Abstract D116: Glucocorticoid receptor interacts with beta-catenin to promote stemness and therapy resistance in prostate cancer cells

Prostate cancer (PCa) is the most commonly diagnosed male cancer, with men of African ancestry showing a disproportionately high incidence and mortality. There is increasing evidence that glucocorticoid signaling through glucocorticoid receptor (GR) is amplified in African American men due to cumulative life stress, and that GR signaling is a key driver of resistance to androgen-targeted therapy, radiotherapy, and taxane chemotherapy in advanced PCa. Recent studies indicate that GR also promotes in PCa cells the formation of tumorspheres, a property of cancer stem cells (CSC); however, the mechanisms remain unclear. CSCs are intrinsically resistant to therapies due to their low-frequency, expression of transporters and efflux pumps, quiescent cell cycle and metabolic profile. Our previous studies demonstrated that docetaxel (DTX)-resistant PCa cells exhibit increased capacity for CSC-like properties, suggesting that these properties contribute to chemoresistance. Like GR, beta-catenin is overexpressed in metastatic and therapy-resistant tumors, and is considered a key regulator of cancer stemness and androgen-targeted therapy resistance. Thus, we hypothesized that GR may interact with beta-catenin in PCa cells to support stemness and chemoresistance. Using whole-cell and nuclear co-immunoprecipitation, we demonstrated the interaction between GR and beta-catenin in several DTX-sensitive and -resistant PCa cell line pairs. Pharmacological inhibition of GR using the selective inhibitor CORT-108297 with concomitant inhibition of beta-catenin using the small molecule inhibitor MSAB significantly enhanced DTX cytotoxicity in resistant PCa cells grown in both adherent and spheroid cultures. The BET bromodomain inhibitor JQ1, an antagonist of enhancer-mediated GR upregulation, also significantly reduced tumorsphere formation and stemness in DTX-resistant PCa cells. In order to gain insights into transcriptomic profiles activated by GR signaling that may contribute to stemness and therapy resistance, we performed RNA sequencing in a racially diverse panel of PCa cell lines (MDA-PCa-2b, VCaP, 22RV1, and PC3) treated with and without dexamethasone, a potent glucocorticoid. We observed that the African American cell line MDA-PCa-2b yielded the largest number of differentially regulated genes, perhaps due to the ability of dexamethasone to signal through both AR and GR in this particular cell line. RNAseq data is currently being mined and validated in cellular models treated with glucocorticoids or androgens, in the presence or absence of anti-GR or anti-androgen inhibitors, in order to identify GR-regulated genes. Our results offer novel insights into mechanisms by which GR signaling may influence tumorsphere formation and stemness, and suggest that combinatorial targeting of GR and beta-catenin could be a promising therapeutic strategy to overcome PCa therapy resistance and consequently reduce PCa mortality and its racial disparities.

Citation Format: Shannalee R Martinez, Evelyn S Sanchez-Hernandez, Xin Chen, Alfonso M Duran, Charles H Wang, Carlos A Casiano. Glucocorticoid receptor interacts with beta-catenin to promote stemness and therapy resistance in prostate cancer cells [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr D116.

Psychosocial Stress, Glucocorticoid Signaling, and Prostate Cancer Health Disparities in African American Men

Recent advances in our understanding of racial disparities in prostate cancer (PCa) incidence and mortality that disproportionately affect African American (AA) men have provided important insights into the psychosocial, socioeconomic, environmental, and molecular contributors. There is, however, limited mechanistic knowledge of how the interplay between these determinants influences prostate tumor aggressiveness in AA men and other men of African ancestry. Growing evidence indicates that chronic psychosocial stress in AA populations leads to sustained glucocorticoid signaling through the glucocorticoid receptor (GR), with negative physiological and pathological consequences. Compelling evidence indicates that treatment of castration-resistant prostate cancer (CRPC) with anti-androgen therapy activates GR signaling. This enhanced GR signaling bypasses androgen receptor (AR) signaling and transcriptionally activates both AR-target genes and GR-target genes, resulting in increased prostate tumor resistance to anti-androgen therapy, chemotherapy, and radiotherapy. Given its enhanced signaling in AA men, GR-together with specific genetic drivers-may promote CRPC progression and exacerbate tumor aggressiveness in this population, potentially contributing to PCa mortality disparities. Ongoing and future CRPC clinical trials that combine standard of care therapies with GR modulators should assess racial differences in therapy response and clinical outcomes in order to improve PCa health disparities that continue to exist for AA men.

Abstract LB-260: Role of the glucocorticoid receptor/beta-catenin interaction in prostate cancer stem cell survival and chemoresistance

Prostate cancer (PCa) is the second leading cause of cancer deaths in U.S. men, disproportionately affecting African American men and certain Hispanic/Latino populations. Patients with advanced PCa are treated with androgen deprivation therapy (ADT) and docetaxel (DTX)-based chemotherapy with effective but transient results due to therapy resistance. While the role of glucocorticoid receptor (GR) in promoting ADT resistance has been well characterized, comparatively little is known about its contribution to PCa stemness and chemoresistance. Our group demonstrated recently that DTX-resistance is associated with upregulation of a stemness transcriptomic program and enhanced cancer stem cell (CSC) properties in PCa cells. We also demonstrated that GR signaling upregulates the DTX-resistance associated proteins Clusterin and LEDGF/p75 in a panel of PCa cells. The proto-oncogene β-catenin promotes CSC survival in many cancers, including PCa, and several studies have demonstrated a crosstalk between AR and β-catenin signaling pathways contributing to ADT resistance. Given the structural similarities between AR and GR and the importance of GR in therapy resistance, this study was designed to investigate the interaction between GR and β-catenin and its contribution to CSC survival and DTX resistance. Using a panel of PCa cell lines including PC3, DU145, 22rv1, and their corresponding DTX-resistant cell lines, we showed by quantitative immunoblotting that GR is upregulated and β-catenin is activated in PC3 and 22rv1 DTX-resistant cells compared to sensitive cells. Co-immunoprecipitation studies revealed interaction between endogenous GR and β-catenin in these cells. We next assessed the effect of the potent GR ligand dexamethasone (Dex) on CSC maintenance, and observed that Dex treatment of PC3 cells increased tumorsphere number and expression of established CSC markers measured by multicolor flow cytometry. To identify potential GR target genes that could mediate the acquisition of CSC properties and DTX resistance, we performed RNA-sequencing analysis in four different Dex-treated and -untreated PCa cell lines. This analysis revealed several candidate GR target genes differentially regulated in a cell-type dependent manner. To determine the effects of the GR/β-catenin interaction on downstream GR target genes and β-catenin target genes, we performed immunoblotting of specific candidate target genes on lysates from cells treated with Dex alone or in combination with COR-10829 (selective GR inhibitor, and MSAB (β-catenin inhibitor). Interestingly, we also observed that the dual blockade of GR and β-catenin markedly reduced tumorsphere formation in DTX-resistant cells, a phenomenon not observed with either GR or β-catenin inhibition alone. In summary, our findings revealed a novel interaction between GR and β-catenin in PCa cells, and suggest that co-targeting the GR/β-catenin signaling axis in advanced PCa patients could be a potential strategy to overcome therapy resistance.

Citation Format: Shannalee R. Martinez, Carlos J. Diaz Osterman, Xin S. Chen, Charles Wang, Lubo Zhang, Carlos A. Casiano. Role of the glucocorticoid receptor/beta-catenin interaction in prostate cancer stem cell survival and chemoresistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-260.

Abstract 1623: Autoantibodies to human endogenous retrovirus K envelope protein (HERV-K ENV) are associated with features of prostate cancer aggressiveness in African American men

Prostate cancer (PCa) is the most commonly diagnosed cancer and the second leading cause of cancer-related deaths in American men. African-American (AA) men are more likely to develop PCa at a younger age and are twice as likely to die from the disease compared to men from other ethnic/racial backgrounds. Even when normalized with equal access to healthcare, socioeconomic status and familial PCa history, AA men still die disproportionately from PCa. Thus, it is paramount to improve the early detection of aggressive PCa. A cancer patient’s humoral immune response to a tumor offers us a minimally invasive opportunity to detect aggressive cancers before a symptomatic tumor emerges. Previous studies indicate that genes associated with immunity and inflammation are significantly upregulated in prostate tumors from AA men compared to European-American (EA) men, suggesting that there are racial differences in the anti-tumor immune response in patients with PCa. This has prompted our laboratory to evaluate the autoantibody repertoire to tumor-associated antigens (TAA) in ethnically diverse patients. Previous studies showed a higher frequency of autoantibodies to the human endogenous retrovirus K (HERV-K) GAG protein in men with late stage PCa. In addition, investigators in this team reported previously an elevated expression of the envelope (ENV) protein in PCa tumors from AA men compared to PCa tumors from EA men. Given the emerging role of HERV-K in human cancers and the potential use of autoantibodies to the ENV and GAG viral proteins as cancer serum biomarkers and immunotherapeutic tools, we investigated the antibody response to the HERV-K ENV in AA and EA men with and without PCa. Using an enzyme-linked immunosorbent assay (ELISA), we detected a significant increase in the frequency of autoantibodies to HERV-K ENV in AA men with PCa compared to EA men with PCa (N=100, p<0.05) and AA men without PCa (N=100, p<0.0001). The frequency of autoantibodies to ENV was also significantly higher in AA men with stage IV (29%, p<0.0001) and AA men with PCa metastasis (40%, p<0.0001) compared to AA men without PCa or EA men with and without PCa. The immunoreactivity of the sera against ENV was confirmed by immunoblotting. To our knowledge this is the first report of an increased autoantibody frequency to HERV-K ENV in PCa patients and the first report of autoantibodies associated with racial differences in PCa. The observation that these autoantibodies are significantly linked to a more aggressive PCa in AA men is also consistent with previous observation of increased upregulation of HERV-K ENV in prostate tumors from AA men. The biological and clinical significance of anti-HERV-K ENV and GAG autoantibodies in PCa, and the racial differences in their frequency and clinical associations, warrant further investigation.

Citation Format: Tino W. Sanchez, Shannalee R. Martinez, Greisha Ortiz-Hernandez, Evelyn Sanchez-Hernandez, Christopher Montgomery, Benjamin Becerra, Tiffany Dorsey, Feng Wang-Johanning, Stefan Ambs, Carlos A. Casiano. Autoantibodies to human endogenous retrovirus K envelope protein (HERV-K ENV) are associated with features of prostate cancer aggressiveness in African American men [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1623.

TSLP or IL-7 provide an IL-7Rα signal that is critical for human B lymphopoiesis

Thymic stromal lymphopoietin (TSLP) and IL-7 are cytokines that signal via the IL-7 receptor alpha (IL-7Rα) to exert both overlapping and unique functions during early stages of mouse B-cell development. In human B lymphopoiesis, the requirement for IL-7Rα signaling is controversial and the roles of IL-7 and TSLP are less clear. Here, we evaluated human B-cell production using novel in vitro and xenograft models of human B-cell development that provide selective IL-7 and human TSLP (hTSLP) stimulation. We show that in vitro human B-cell production is almost completely blocked in the absence of IL-7Rα stimulation, and that either TSLP or IL-7 can provide a signal critical for the production and proliferation of human CD19(+) PAX5(+) pro-B cells. Analysis of primary human bone marrow stromal cells shows that they express both IL-7 and TSLP, providing an in vivo source of these cytokines. We further show that the in vivo production of human pro-B cells under the influence of mouse IL-7 in a xenograft scenario is reduced by anti-IL-7 neutralizing antibodies, and that this loss can be restored by hTSLP at physiological levels. These data establish the importance of IL-7Rα mediated signals for normal human B-cell production.

LEDGF/p75 Overexpression Attenuates Oxidative Stress-Induced Necrosis and Upregulates the Oxidoreductase ERP57/PDIA3/GRP58 in Prostate Cancer

Prostate cancer (PCa) mortality is driven by highly aggressive tumors characterized by metastasis and resistance to therapy, and this aggressiveness is mediated by numerous factors, including activation of stress survival pathways in the pro-inflammatory tumor microenvironment. LEDGF/p75, also known as the DFS70 autoantigen, is a stress transcription co-activator implicated in cancer, HIV-AIDS, and autoimmunity. This protein is targeted by autoantibodies in certain subsets of patients with PCa and inflammatory conditions, as well as in some apparently healthy individuals. LEDGF/p75 is overexpressed in PCa and other cancers, and promotes resistance to chemotherapy-induced cell death via the transactivation of survival proteins. We report in this study that overexpression of LEDGF/p75 in PCa cells attenuates oxidative stress-induced necrosis but not staurosporine-induced apoptosis. This finding was consistent with the observation that while LEDGF/p75 was robustly cleaved in apoptotic cells into a p65 fragment that lacks stress survival activity, it remained relatively intact in necrotic cells. Overexpression of LEDGF/p75 in PCa cells led to the upregulation of transcript and protein levels of the thiol-oxidoreductase ERp57 (also known as GRP58 and PDIA3), whereas its depletion led to ERp57 transcript downregulation. Chromatin immunoprecipitation and transcription reporter assays showed LEDGF/p75 binding to and transactivating the ERp57 promoter, respectively. Immunohistochemical analysis revealed significantly elevated co-expression of these two proteins in clinical prostate tumor tissues. Our results suggest that LEDGF/p75 is not an inhibitor of apoptosis but rather an antagonist of oxidative stress-induced necrosis, and that its overexpression in PCa leads to ERp57 upregulation. These findings are of significance in clarifying the role of the LEDGF/p75 stress survival pathway in PCa.

Antenatal hypoxia induces epigenetic repression of glucocorticoid receptor and promotes ischemic-sensitive phenotype in the developing heart

Large studies in humans and animals have demonstrated a clear association of an adverse intrauterine environment with an increased risk of cardiovascular disease later in life. Yet mechanisms remain largely elusive. The present study tested the hypothesis that gestational hypoxia leads to promoter hypermethylation and epigenetic repression of the glucocorticoid receptor (GR) gene in the developing heart, resulting in increased heart susceptibility to ischemia and reperfusion injury in offspring. Hypoxic treatment of pregnant rats from day 15 to 21 of gestation resulted in a significant decrease of GR exon 14, 15, 16, and 17 transcripts, leading to down-regulation of GR mRNA and protein in the fetal heart. Functional cAMP-response elements (CREs) at -4408 and -3896 and Sp1 binding sites at -3425 and -3034 were identified at GR untranslated exon 1 promoters. Hypoxia significantly increased CpG methylation at the CREs and Sp1 binding sites and decreased transcription factor binding to GR exon 1 promoter, accounting for the repression of the GR gene in the developing heart. Of importance, treatment of newborn pups with 5-aza-2'-deoxycytidine reversed hypoxia-induced promoter methylation, restored GR expression and prevented hypoxia-mediated increase in ischemia and reperfusion injury of the heart in offspring. The findings demonstrate a novel mechanism of epigenetic repression of the GR gene in fetal stress-mediated programming of ischemic-sensitive phenotype in the heart.

A novel xenograft model to study the role of TSLP-induced CRLF2 signals in normal and malignant human B lymphopoiesis

Thymic stromal lymphopoietin (TSLP) stimulates in-vitro proliferation of human fetal B-cell precursors. However, its in-vivo role during normal human B lymphopoiesis is unknown. Genetic alterations that cause overexpression of its receptor component, cytokine receptor-like factor 2 (CRLF2), lead to high-risk B-cell acute lymphoblastic leukemia implicating this signaling pathway in leukemogenesis. We show that mouse thymic stromal lymphopoietin does not stimulate the downstream pathways (JAK/STAT5 and PI3K/AKT/mTOR) activated by the human cytokine in primary high-risk leukemia with overexpression of the receptor component. Thus, the utility of classic patient-derived xenografts for in-vivo studies of this pathway is limited. We engineered xenograft mice to produce human thymic stromal lymphopoietin (+T mice) by injection with stromal cells transduced to express the cytokine. Control (-T) mice were produced using stroma transduced with control vector. Normal levels of human thymic stromal lymphopoietin were achieved in sera of +T mice, but were undetectable in -T mice. Patient-derived xenografts generated from +T as compared to -T mice showed a 3-6-fold increase in normal human B-cell precursors that was maintained through later stages of B-cell development. Gene expression profiles in high-risk B-cell acute lymphoblastic leukemia expanded in +T mice indicate increased mTOR pathway activation and are more similar to the original patient sample than those from -T mice. +T/-T xenografts provide a novel pre-clinical model for understanding this pathway in B lymphopoiesis and identifying treatments for high-risk B-cell acute lymphoblastic leukemia with overexpression of cytokine-like factor receptor 2.

Epigenetic mechanisms in heart development and disease

Suboptimal intrauterine development has been linked to predisposition to cardiovascular disease in adulthood, a concept termed 'developmental origins of health and disease'. Although the exact mechanisms underlying this developmental programming are unknown, a growing body of evidence supports the involvement of epigenetic regulation. Epigenetic mechanisms such as DNA methylation, histone modifications and micro-RNA confer added levels of gene regulation without altering DNA sequences. These modifications are relatively stable signals, offering possible insight into the mechanisms underlying developmental origins of health and disease. This review will discuss the role of epigenetic mechanisms in heart development as well as aberrant epigenetic regulation contributing to cardiovascular disease. Additionally, we will address recent advances targeting epigenetic mechanisms as potential therapeutic approaches to cardiovascular disease.

Abstract B25: A human-mouse xenograft model to evaluate therapies and study the role of TSLP-induced signals in Ph-like ALL

While the overall survival rate for children with B cell precursor acute lymphoblastic leukemia (B-ALL) is high, a subset of children with this disease are at high risk for relapse and death. Genome-wide analysis has shown that gene expression profiles in these high-risk B-ALLs is similar to that of Philadelphia chromosome–positive ALL and these are designated Ph-like ALL. Approximately half of Ph-like ALL are characterized by genetic defects resulting in overexpression of CRLF2. CRLF2, together with the IL-7Rα, forms a receptor complex that is activated by the cytokine, TSLP. The JAK-STAT5 pathway is phosphorylated downstream of this receptor complex activation. The activating JAK mutations found in some CRLF2 B-ALL have led to speculation that TSLP stimulation is not a factor in CRLF B-ALL. In preliminary studies to address this question we evaluated the effect of TSLP on a CRLF2 B-ALL cell lines with JAK defects and which have been reported to exhibit constitutive JAK-STAT5 activation. Our data show that TSLP increases STAT5 phosphorylation in these cell lines and also in primary CRLF2 B-ALL cells. Our next step was to evaluate the role of TSLP-CRLF2 interactions in vivo in the human-mouse xenograft model. However, mouse TSLP is different from most other cytokines produced in the xenograft in that it is species-specific and does not activate the human TSLP receptor complex that includes CRLF2. Thus, traditional xenograft models do not provide the TSLP-CRLF2 interactions that we believe to be a major factor in CRLF2 B-ALL. To overcome this obstacle we engineered immune-deficient NOD/SCID IL-2Rγ null (NSG) mice to express human TSLP (hTSLP+ mice) as well as control mice that lack the TSLP cytokine (hTSLP– mice). ELISA assays show serum hTSLP levels in the hTSLP+ mice that approximate the normal range in human serum. We used this hTSLP+/- xenograft model system to study the in vivo effects of TSLP on mice transplanted with a CRLF2 B-ALL. We used this hTSLP+/– xenograft model system to evaluate the in vivo effects of TSLP on survival and proliferation of transplanted CRLF2 B-ALL cells harboring a JAK defect (MUTZ5 cell line). Mice were euthanized at 5 weeks and BM was harvested. Evaluation of BM disease by flow cytometry showed that the percentage of viable human leukemia cells in hTSLP+ mice was twice that observed in hTSLP– mice. Evaluation of cell cycle progression in human CRLF2 B-ALL cells isolated from xenograft BM showed that the percentage of cycling cells in hTSLP+ mice was 2.5 fold higher than in hTSLP– mice. When primary Ph-like ALL cells were transplanted to produce hTSLP+/– xenografts, the viable pre-B ALL cells present in the BM of hTSLP+ mice showed higher expression levels of the TSLPR components (CRLF2 and IL-7Rα) than those in the hTSLP- mice. These data provide evidence that the TSLP produced in this model is active and that it impacts primary pre-B ALL cells. Preliminary data obtained from this model suggests that TSLP provides a signal that promotes in vivo survival of CRLF2 B-ALL cells and that it may play a role in selection of leukemia clones during in vivo leukemogenesis. Microarray analysis comparing gene expression in primary CRLF2 B-ALL cells isolated from hTSLP+ and hTSLP– xenograft mice identified 565 that genes are differentially regulated (> 2 fold up or downregulated; p<.05). Ingenuity Pathway Analysis is currently underway to identify the signaling pathways that are regulated by hTSLP in CRLF2 B-ALL in vivo in the hTSLP+/– xenograft model. The identification of genes downstream of TSLP-CRLF2 signaling has the potential of providing drug targets for combination therapy to effectively treat Ph-like B-ALL. The hTSLP+/– xenograft model provides an important tool for evaluating the in vivo efficacy of these and other drugs to treat CRLF2 B-ALL.

Citation Format: Ruijun Su, Francis L. Olivia, Shannalee R. Martinez, Ineavely Baez, Terry Ann Milford, Terrence Bennett, Ross Fisher, Christopher L. Morris, Sinisa Dovat, Kimberly J. Payne. A human-mouse xenograft model to evaluate therapies and study the role of TSLP-induced signals in Ph-like ALL. [abstract]. In: Proceedings of the AACR Special Conference: The Translational Impact of Model Organisms in Cancer; Nov 5-8, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(11 Suppl):Abstract nr B25.

Abstract 5027: In vivo effects of TSLP in a human-mouse xenograft model of CRLF2 B-ALL

Pediatric CRLF2 B-cell Acute Lymphoblastic Leukemia (CRLF2 B-ALL) is a high-risk form of leukemia that is associated with relapse and poor patient survival outcomes. This leukemia occurs five times more frequently among children of Hispanic/Latino ethnicity than others and represents the most significant biological component of childhood cancer health disparities identified to date. CRLF2 B-ALL arises from genetic alterations that result in overexpression of the CRLF2 gene. CRLF2, together with the IL-7 receptor α, forms a receptor complex that is activated by the cytokine, TSLP. The JAK-STAT5 pathway is phosphorylated downstream of receptor activation. The activating JAK mutations found in some CRLF2 B-ALL have led to speculation that TSLP stimulation is not a factor in CRLF B-ALL. However, we found that TSLP increases STAT5 phosphorylation, even in CRLF2 B-ALL cells with JAK mutations. Our studies of normal B cell development show that TSLP stimulation increases cellular proliferation in early human B lineage cells. We also find that pediatric bone marrow (BM) stromal cells express TSLP and thus provide an in vivo source of TSLP that can act on CRLF2 B-ALL cells. We proposed to evaluate the role of TSLP in human CRLF2 B-ALL using a human-mouse xenograft model. However, TSLP is different from most other cytokines produced in the mouse in that it is species-specific and therefore does not activate the human TSLP receptor complex that contains CRLF2. Thus, traditional xenograft models do not provide the TSLP-CRLF2 interactions that we believe to be a contributing factor in CRLF2 B-ALL. To overcome this hurdle we engineered immune deficient mice to express human TSLP (hTSLP+ mice) as well as control mice that lack the human TSLP cytokine (hTSLP- mice). We used this hTSLP+/- xenograft model system to evaluate the in vivo effects of TSLP on survival and proliferation of transplanted CRLF2 B-ALL cells harboring a JAK defect (MUTZ5 cell line). Mice were euthanized at 5 weeks and BM was harvested. Evaluation of BM disease by flow cytometry showed that the percentage of viable human leukemia cells in hTSLP+ mice was twice that observed in hTSLP-mice. Evaluation of cell cycle progression in human CRLF2 B-ALL cells isolated from xenograft BM showed that the percentage of cycling cells in hTSLP+ mice was 2.5 fold higher than in hTSLP- mice. These preliminary data suggest that TSLP may contribute to CRLF2 B-ALL by increasing the survival and proliferation of CRLF2-B-ALL cells. Ongoing studies are focused on evaluating in vivo effects of TSLP in primary CRLF2 B-ALL from Hispanic patients. The identification of genes downstream of TSLP-CRLF2 signaling has the potential of providing drug targets for combination therapy to effectively treat CRLF2 B-ALL and reduce cancer health disparities in Hispanic childhood B-ALL.

This work is supported by NIH R21R21CA162259, a St. Baldrick's Foundation Research Grant, and a LLU GCAT award (KJP)

Citation Format: Rui-jun Su, Olivia L. Francis, Shannalee R. Martinez, Ineavely Baez, Terry-Ann Milford, Christopher L. Morris, Ross O. Fisher, Xiao-Bing Zhang, Sinisa Dovat, Kimberly J. Payne. In vivo effects of TSLP in a human-mouse xenograft model of CRLF2 B-ALL. [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 5027. doi:10.1158/1538-7445.AM2013-5027

Abstract B32: A novel preclinical model to identify therapies for CRLF2 B-ALL and reduce childhood cancer health disparities

Hispanic children with Acute Lymphoblastic Leukemia (ALL) have a 39% higher death rate than white children. A major contributor to this disparity is the lack of therapies that specifically target CRLF2 B cell ALL. This high-risk leukemia occurs five times more frequently among children of Hispanic/Latino ethnicity than others and represents the most significant biological component of childhood cancer health disparities identified to date. CRLF2 B-ALL is caused by genetic alterations that result in B cells that overexpress the cytokine receptor component, CRLF2, leading to malignant transformation and high-risk leukemia with poor prognosis. CRLF2 pairs with the IL-7Rα, to form a receptor complex that is activated by the cytokine, TSLP. Activation of the receptor complex stimulates downstream JAK-STAT5 phosphorylation that has been shown to induce proliferation and survival of B-ALL cells. Activating JAK mutations are found in many cases of CRLF2 B-ALL and have led to speculation that stimulation of the receptor by TSLP is not a factor in this disease. In preliminary studies to address this question we evaluated the effect of TSLP in CRLF2 B-ALL cells with JAK defects. Our data show that TSLP increases STAT5 phosphorylation in these cell lines and also in primary CRLF2 B-ALL cells. These data suggest that TSLP can activate JAK-STAT5 signaling to induce downstream survival and proliferation in CRLF2-B-ALL cells, including those with JAK defects. Bone marrow (BM) provides the tumor microenvironment that can harbor chemoresistant B-ALL cells responsible for relapse in B-ALL. We used RT-PCR and ELISA assays to show that TSLP is expressed in BM cells from pediatric patients and thus could provide an in vivo source of TSLP to stimulate CRLF2 B-ALL cells. Human-mouse xenograft models produced by transplanting human leukemia cells into immune deficient mice mimic the in vivo environment and are the model of choice for identifying therapies that target the mechanisms of chemoresistance that are characteristic of high-risk leukemia. However, mouse TSLP is different from most other cytokines produced in the xenograft in that it is species-specific and does not activate the human TSLP receptor complex that contains CRLF2. Thus, traditional xenograft models do not provide the TSLP-CRLF2 interactions that our data implicate as a contributing factor in CRLF2 B-ALL. To overcome this obstacle we have engineered immune deficient mice to express human TSLP (hTSLP+ mice) as well as control mice that lack the TSLP cytokine (hTSLP– mice). ELISA assays show hTSLP levels in the hTSLP+ mice that approximate the normal range in human plasma. We used this hTSLP+/- xenograft model system to study the in vivo effects of TSLP on mice transplanted with a CRLF2 B-ALL cell line harboring a JAK defect (MUTZ5) and with primary pre-B ALL cells from a Hispanic patient. Mice were euthanized at 5 weeks and BM disease was evaluated. In recipients of MUTZ5 B-ALL cells the percentage of viable leukemia cells in hTSLP+ mice was twice that observed in hTSLP- mice. Similarly, in recipients of primary B-ALL, the percentage of viable leukemia cells was higher in hTSLP+ than hTSLP- mice. These data provide evidence that the TSLP produced in this model is active and that TSLP-CRLF2 interactions contribute in vivo to CRLF2-B-ALL. This model will be particularly important for identifying therapies that can effectively target CRLF2 B-ALL and reduce cancer health disparities in Hispanic childhood B-ALL.

Citation Format: Francis L. Olivia, Shannalee R. Martinez, Terrence Bennett, Ineavely Baez, Terry-Ann Milford, Christopher L. Morris, Ross O. Fisher, Xiao-Bing Zhang, Rui-Jun Su, Sinisa Dovat, Kimberly J. Payne. A novel preclinical model to identify therapies for CRLF2 B-ALL and reduce childhood cancer health disparities. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr B32.

Abstract 1347: A human-mouse xenograft model to study the role of TSLP in CRLF2d B-ALL

B-cell precursor ALL where genetic defects lead to overexpression of CRLF2 (CRLF2d B-ALL) are high-risk with poor prognosis. CRLFd B-ALL occurs 5 times more frequently among children of Hispanic/Latino ethnicity and is a major contributor to the health disparity in survival of Hispanic children with ALL. CRLF2, together with the IL-7Rα, forms a receptor complex that is activated by the cytokine, TSLP. The JAK-STAT5 pathway is phosphorylated downstream of receptor activation. The activating JAK mutations found in some CRLF2 B-ALL have led to speculation that TSLP stimulation is not a factor in CRLF B-ALL. In preliminary studies to address this question we evaluated the effect of TSLP on two CRLF2d B-ALL cell lines with JAK defects and which have been reported to exhibit constitutive JAK-STAT5 activation. Our data show that TSLP increases STAT5 phosphorylation in both of these cell lines and in primary B-ALL cells that overexpress CRLF2. Our next step was to evaluate the role of TSLP-CRLF2 interaction in vivo in the human-mouse xenograft model. However, mouse TSLP is different from most other cytokines produced in the xenograft in that it is species-specific and does not activate the human TSLP receptor complex that contains CRLF2. Thus, traditional xenograft models do not provide the TSLP-CRLF2 interactions that we believe to be a major factor in CRLF2 B-ALL. To overcome this obstacle we have engineered immune deficient NOD/SCID IL-2Rγ null (NSG) mice to express human TSLP (hTSLP+ mice) as well as control mice that lack the TSLP cytokine (hTSLP- mice). ELISA assays show plasma hTSLP levels in the hTSLP+ mice that approximate the normal range in human plasma. We have used this hTSLP+/− system to expand a sample of primary pre-B ALL cells from a patient that includes clones of CRLF2-HI and CRLF2- B-ALL cells. Preliminary data indicate that the pre-B ALL cells expanded in hTSLP+ mice show higher expression levels of the TSLPR components (CRLF2 and IL-7Rα) than cells expanded in the hTSLP- mice. This data provide evidence that the TSLP produced in this model is active and that it impacts primary pre-B ALL cells. The hTSLP+ mice that we produce will allow for the first time the study of normal and malignant B lymphopoiesis in a model that provides the complex bone marrow architecture of the xenograft while providing the full range of cytokines that are known to act on early B lineage cells (IL-7, FL and TSLP). This model will be particularly important for identifying therapies that can effectively target CRLF2-d B-ALL and reduce cancer health disparities in Hispanic childhood B-ALL.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1347. doi:1538-7445.AM2012-1347

The stress oncoprotein LEDGF/p75 interacts with the methyl CpG binding protein MeCP2 and influences its transcriptional activity

The lens epithelium-derived growth factor p75 (LEDGF/p75) is a transcription coactivator that promotes resistance to oxidative stress- and chemotherapy-induced cell death. LEDGF/p75 is also known as the dense fine speckles autoantigen of 70 kDa (DFS70) and has been implicated in cancer, HIV-AIDS, autoimmunity, and inflammation. To gain insights into mechanisms by which LEDGF/p75 protects cancer cells against stress, we initiated an analysis of its interactions with other transcription factors and the influence of these interactions on stress gene activation. We report here that both LEDGF/p75 and its short splice variant LEDGF/p52 interact with MeCP2, a methylation-associated transcriptional modulator, in vitro and in various human cancer cells. These interactions were established by several complementary approaches: transcription factor protein arrays, pull-down and AlphaScreen assays, coimmunoprecipitation, and nuclear colocalization by confocal microscopy. MeCP2 was found to interact with the N-terminal region shared by LEDGF/p75 and p52, particularly with the PWWP-CR1 domain. Like LEDGF/p75, MeCP2 bound to and transactivated the Hsp27 promoter (Hsp27pr). LEDGF/p75 modestly enhanced MeCP2-induced Hsp27pr transactivation in U2OS osteosarcoma cells, whereas this effect was more pronounced in PC3 prostate cancer cells. LEDGF/p52 repressed Hsp27pr activity in U2OS cells. Interestingly, siRNA-induced silencing of LEDGF/p75 in U2OS cells dramatically elevated MeCP2-mediated Hsp27pr transactivation, whereas this effect was less pronounced in PC3 cells depleted of LEDGF/p75. These results suggest that the LEDGF/p75-MeCP2 interaction differentially influences Hsp27pr activation depending on the cellular and molecular context. These findings are of significance in understanding the contribution of this interaction to the activation of stress survival genes.

Differential expression of peroxiredoxins in prostate cancer: consistent upregulation of PRDX3 and PRDX4

BACKGROUND

The peroxiredoxins (PRDXs) are emerging as regulators of antioxidant defense, apoptosis, and therapy resistance in cancer. Because their significance in prostate cancer (PCa) is unclear, we investigated their expression and clinical associations in PCa.

METHODS

Transcript expression of PRDX1-6 in PCa was evaluated in cancer gene microarray datasets, whereas protein expression was evaluated by immunoblotting in prostate cell lines, and by immunohistochemistry (IHC) in prostate tissue microarrays (TMAs) containing tumor (n = 80) and control (n = 17) tissues. PRDX3 was also analyzed in TMAs containing PCa tissues from African-American and Caucasian patients (n = 150 per group). PRDX expression was correlated with patients' clinicopathologic characteristics.

RESULTS

Analysis of PRDX expression in cancer microarray datasets revealed consistent upregulation (tumor vs. normal) of PRDX3 and 4. All PRDXs exhibited elevated protein expression in PCa cell lines, compared with non-tumor cells. IHC revealed significant overexpression of PRDX3 and 4 in PCa, associated with age, increased prostate specific antigen (PSA), tumor stage, or Gleason score. High PRDX3 staining was associated with early age and elevated Gleason score at time of radical prostatectomy in African-American but not in Caucasian patients with PCa. PSA recurrence free survival in patients with low PRDX3 tumor expression was significantly longer in Caucasians compared to African-Americans, but no difference was detected for high expression.

CONCLUSIONS

PRDXs exhibit differential expression in prostate tumors, with PRDX3 and 4 consistently upregulated. Their role in PCa development, and their potential as biological determinants of PCa health disparities and novel therapeutic targets, deserve further investigation.

Quality control issues in the management of colon cancer patients

Quality assurance in colon cancer demands a multidisciplinary effort involving general practitioners, surgeons, radiologists, gastroenterologists, medical oncologists, and pathologists, among others. Maximal improvements in survival will result when colon cancer screening, diagnosis, staging, treatment and surveillance are optimized. We seek to identify those issues most relevant to the quality of care we provide our colon cancer patients.