Prospects of Gene Therapy to Treat Melanoma

The incidence of melanoma has continued to increase over the past 30 years. Hence, developing effective therapies to treat both primary and metastatic melanoma are essential. While advances in targeted therapy and immunotherapy have provided novel therapeutic options to treat melanoma, gene therapy may provide additional strategies for the treatment of metastatic melanoma clinically. This review focuses upon the challenges and opportunities that gene therapy provides for targeting melanoma. We begin with a discussion of the various gene therapy targets which are relevant to melanoma. Next, we explore the gene therapy clinical trials that have been conducted for treating melanoma. Finally, challenges faced in gene therapy as well as combination therapies for targeting melanoma, which may circumvent these obstacles, will be discussed. Targeted combination gene therapy strategies hold significant promise for developing the most effective therapeutic outcomes, while reducing the toxicity to noncancerous cells, and would integrate the patient's immune system to diminish melanoma progression. Next-generation vectors designed to embody required safety profiles and "theranostic" attributes, combined with immunotherapeutic strategies would be critical in achieving beneficial management and therapeutic outcomes in melanoma patients.

Loss of tumor suppressor Merlin results in aberrant activation of Wnt/β-catenin signaling in cancer

The expression of the tumor suppressor Merlin is compromised in nervous system malignancies due to genomic aberrations. We demonstrated for the first time, that in breast cancer, Merlin protein expression is lost due to proteasome-mediated elimination. Immunohistochemical analysis of tumor tissues from patients with metastatic breast cancer revealed characteristically reduced Merlin expression. Importantly, we identified a functional role for Merlin in impeding breast tumor xenograft growth and reducing invasive characteristics. We sought to determine a possible mechanism by which Merlin accomplishes this reduction in malignant activity. We observed that breast and pancreatic cancer cells with loss of Merlin show an aberrant increase in the activity of β-catenin concomitant with nuclear localization of β-catenin. We discovered that Merlin physically interacts with β-catenin, alters the sub-cellular localization of β-catenin, and significantly reduces the protein levels of β-catenin by targeting it for degradation through the upregulation of Axin1. Consequently, restoration of Merlin inhibited β-catenin-mediated transcriptional activity in breast and pancreatic cancer cells. We also present evidence that loss of Merlin sensitizes tumor cells to inhibition by compounds that target β-catenin-mediated activity. Thus, this study provides compelling evidence that Merlin reduces the malignant activity of pancreatic and breast cancer, in part by suppressing the Wnt/β-catenin pathway. Given the potent role of Wnt/β-catenin signaling in breast and pancreatic cancer and the flurry of activity to test β-catenin inhibitors in the clinic, our findings are opportune and provide evidence for Merlin in restraining aberrant activation of Wnt/β-catenin signaling.

MDA-7/IL-24 functions as a tumor suppressor gene in vivo in transgenic mouse models of breast cancer

Melanoma differentiation associated gene-7/Interleukin-24 (MDA-7/IL-24) is a novel member of the IL-10 gene family that selectively induces apoptosis and toxic autophagy in a broad spectrum of human cancers, including breast cancer, without harming normal cells or tissues. The ability to investigate the critical events underlying cancer initiation and progression, as well as the capacity to test the efficacy of novel therapeutics, has been significantly advanced by the development of genetically engineered mice (GEMs) that accurately recapitulate specific human cancers. We utilized three transgenic mouse models to better comprehend the in vivo role of MDA-7/IL-24 in breast cancer. Using the MMTV-PyMT spontaneous mammary tumor model, we confirmed that exogenously introducing MDA-7/IL-24 using a Cancer Terminator Virus caused a reduction in tumor burden and also produced an antitumor “bystander” effect. Next we performed xenograft studies in a newly created MMTV-MDA-7 transgenic model that over-expresses MDA-7/IL-24 in the mammary glands during pregnancy and lactation, and found that MDA-7/IL-24 overexpression delayed tumor growth following orthotopic injection of a murine PDX tumor cell line (mPDX) derived from a tumor formed in an MMTV-PyMT mouse. We also crossed the MMTV-MDA-7 line to MMTV-Erbb2 transgenic mice and found that MDA-7/IL-24 overexpression delayed the onset of mammary tumor development in this model of spontaneous mammary tumorigenesis as well. Finally, we assessed the role of MDA-7/IL-24 in immune regulation, which can potentially contribute to tumor suppression in vivo. Our findings provide further direct in vivo evidence for the role of MDA-7/IL-24 in tumor suppression in breast cancer in immune-competent transgenic mice.

Suppression of Her2/Neu mammary tumor development in mda-7/IL-24 transgenic mice

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) encodes a tumor suppressor gene implicated in the growth of various tumor types including breast cancer. We previously demonstrated that recombinant adenovirus-mediated mda-7/IL-24 expression in the mammary glands of carcinogen-treated (methylnitrosourea, MNU) rats suppressed mammary tumor development. Since most MNU-induced tumors in rats contain activating mutations in Ha-ras, which arenot frequently detected in humans, we presently examined the effect of MDA-7/IL-24 on Her2/Neu-induced mammary tumors, in which the RAS pathway is induced. We generated tet-inducible MDA-7/IL-24 transgenic mice and crossed them with Her2/Neu transgenic mice. Triple compound transgenic mice treated with doxycycline exhibited a strong inhibition of tumor development, demonstrating tumor suppressor activity by MDA-7/IL-24 in immune-competent mice. MDA-7/IL-24 induction also inhibited growth of tumors generated following injection of Her2/Neu tumor cells isolated from triple compound transgenic mice that had not been treated with doxycycline, into the mammary fat pads of isogenic FVB mice. Despite initial growth suppression, tumors in triple compound transgenic mice lost mda-7/IL-24 expression and grew, albeit after longer latency, indicating that continuous presence of this cytokine within tumor microenvironment is crucial to sustain tumor inhibitory activity. Mechanistically, MDA-7/IL-24 exerted its tumor suppression effect on HER2⁺ breast cancer cells, at least in part, through PERP, a member of PMP-22 family with growth arrest and apoptosis-inducing capacity. Overall, our results establish mda-7/IL-24 as a suppressor of mammary tumor development and provide a rationale for using this cytokine in the prevention/treatment of human breast cancer.

Detecting Tumor Metastases: The Road to Therapy Starts Here

Metastasis is the complex process by which primary tumor cells migrate and establish secondary tumors in an adjacent or distant location in the body. Early detection of metastatic disease and effective therapeutic options for targeting these detected metastases remain impediments to effectively treating patients with advanced cancers. If metastatic lesions are identified early, patients might maximally benefit from effective early therapeutic interventions. Further, monitoring patients whose primary tumors are effectively treated for potential metastatic disease onset is also highly valuable. Finally, patients with metastatic disease can be monitored for efficacy of specific therapeutic interventions through effective metastatic detection techniques. Thus, being able to detect and visualize metastatic lesions is key and provides potential to greatly improve overall patient outcomes. In order to achieve these objectives, researchers have endeavored to mechanistically define the steps involved in the metastatic process as well as ways to effectively detect metastatic progression. We presently overview various preclinical and clinical in vitro and in vivo assays developed to more efficiently detect tumor metastases, which provides the foundation for developing more effective therapies for this invariably fatal component of the cancerous process.

Abrus agglutinin is a potent anti-proliferative and anti-angiogenic agent in human breast cancer

Abrus agglutinin (AGG), a plant lectin isolated from the seeds of Abrus precatorius, has documented antitumor and immunostimulatory effects in murine models. To examine possible antitumor activity against breast cancer, we established human breast tumor xenografts in athymic nude mice and intraperitoneally administered AGG. AGG inhibited tumor growth and angiogenesis as confirmed by monitoring the expression of Ki-67 and CD-31, respectively. In addition, TUNEL positive cells increased in breast tumors treated with AGG suggesting that AGG mediates anti-tumorigenic activity through induction of apoptosis and inhibition of angiogenesis. On a molecular level, AGG caused extrinsic apoptosis through ROS generation that was AKT-dependent in breast cancer cells, without affecting primary mammary epithelial cells, suggesting potential cancer specificity of this natural compound. In addition, using HUVECs, AGG inhibited expression of the pro-angiogenic factor IGFBP-2 in an AKT-dependent manner, reducing angiogenic phenotypes both in vitro and in vivo. Overall, the present results establish that AGG promotes both apoptosis and anti-angiogenic activities in human breast tumor cells, which might be exploited for treatment of breast and other cancers.

Gene Therapies for Cancer: Strategies, Challenges and Successes

Gene therapy, which involves replacement of a defective gene with a functional, healthy copy of that gene, is a potentially beneficial cancer treatment approach particularly over chemotherapy, which often lacks selectivity and can cause non-specific toxicity. Despite significant progress pre-clinically with respect to both enhanced targeting and expression in a tumor-selective manner several hurdles still prevent success in the clinic, including non-specific expression, low-efficiency delivery and biosafety. Various innovative genetic approaches are under development to reconstruct vectors/transgenes to make them safer and more effective. Utilizing cutting-edge delivery technologies, gene expression can now be targeted in a tissue- and organ-specific manner. With these advances, gene therapy is poised to become amenable for routine cancer therapy with potential to elevate this methodology as a first line therapy for neoplastic diseases. This review discusses recent advances in gene therapy and their impact on a pre-clinical and clinical level.

Molecular-genetic imaging of cancer

Molecular-genetic imaging of cancer using nonviral delivery systems has great potential for clinical application as a safe, efficient, noninvasive tool for visualization of various cellular processes including detection of cancer, and its attendant metastases. In recent years, significant effort has been expended in overcoming technical hurdles to enable clinical adoption of molecular-genetic imaging. This chapter will provide an introduction to the components of molecular-genetic imaging and recent advances on each component leading to safe, efficient clinical applications for detecting cancer. Combination with therapy, namely, generating molecular-genetic theranostic constructs, will provide further impetus for clinical translation of this promising technology.

MDA-9/Syntenin regulates differentiation and angiogenesis programs in head and neck squamous cell carcinoma

Little is known about the molecular pathways regulating poor differentiation and invasion of head and neck squamous cell carcinoma (HNSCC). In the present study, we aimed to determine the role of MDA-9/Syntenin, a metastasis associated molecule in HNSCC tumorigenesis. Elevated MDA-9/Syntenin expression was evident in 67% (54/81) primary HNSCC tumors (p=0.001-0.002) and 69% (9/13) pre-neoplastic tissues (p=0.02-0.03). MDA-9/Syntenin overexpression was associated with the stage (p=0.001), grade (p=0.001) and lymph node metastasis (p=0.0001). Silencing of MDA-9/Syntenin in 3 poorly differentiated HNSCC cell lines induced squamous epithelial cell differentiation, disrupted angiogenesis and reduced tumor growth in vitro and in vivo. We confirmed SPRR1B and VEGFR1 as the key molecular targets of MDA-9/Syntenin on influencing HNSCC differentiation and angiogenesis respectively. MDA-9/Syntenin disrupted SPRR1B expression interacting through its PDZ1 domain and altered VEGFR1 expression in vitro and in vivo. VEGFR1 co-localized with MDA-9/Syntenin in HNSCC cell lines and primary tumor. Downregulation of growth regulatory molecules CyclinD1, CDK4, STAT3, PI3K and CTNNB1 was also evident in the MDA-9/Syntenin depleted cells, which was reversed following over-expression of MDA-9/Syntenin in immortalized oral epithelial cells. Our results suggest that early induction of MDA-9/Syntenin expression influences HNSCC progression and should be further evaluated for potential biomarker development.

Targeting tumor invasion: the roles of MDA-9/Syntenin

INTRODUCTION

Melanoma differentiation-associated gene - 9 (MDA-9)/Syntenin has become an increasingly popular focus for investigation in numerous cancertypes. Originally implicated in melanoma metastasis, it has diverse cellular roles and is consistently identified as a regulator of tumor invasion and angiogenesis. As a potential target for inhibiting some of the most lethal aspects of cancer progression, further insight into the function of MDA-9/Syntenin is mandatory.

AREAS COVERED

Recent literature and seminal articles were reviewed to summarize the latest collective understanding of MDA-9/Syntenin's role in normal and cancerous settings. Insights into its participation in developmental processes are included, as is the functional significance of the N- and C-terminals and PDZ domains of MDA-9/Syntenin. Current reports highlight the clinical significance of MDA-9/Syntenin expression level in a variety of cancers, often correlating directly with reduced patient survival. Also presented are assessments of roles of MDA-9/Syntenin in cancer progression as well as its functions as an intracellular adapter molecule.

EXPERT OPINION

Multiple studies demonstrate the importance of MDA-9/Syntenin in tumor invasion and progression. Through the use of novel drug design approaches, this protein may provide a worthwhile therapeutic target. As many conventional therapies do not address, or even enhance, tumor invasion, an anti-invasive approach would be a worthwhile addition in cancer therapy.

Suppression of miR-184 in malignant gliomas upregulates SND1 and promotes tumor aggressiveness

BACKGROUND

Malignant glioma is an aggressive cancer requiring new therapeutic targets. MicroRNAs (miRNAs) regulate gene expression post transcriptionally and are implicated in cancer development and progression. Deregulated expressions of several miRNAs, specifically hsa-miR-184, correlate with glioma development.

METHODS

Bioinformatic approaches were used to identify potential miR-184-regulated target genes involved in malignant glioma progression. This strategy identified a multifunctional nuclease, SND1, known to be overexpressed in multiple cancers, including breast, colon, and hepatocellular carcinoma, as a putative direct miR-184 target gene. SND1 levels were evaluated in patient tumor samples and human-derived cell lines. We analyzed invasion and signaling in vitro through SND1 gain-of-function and loss-of-function. An orthotopic xenograft model with primary glioma cells demonstrated a role of miR-184/SND1 in glioma pathogenesis in vivo.

RESULTS

SND1 is highly expressed in human glioma tissue and inversely correlated with miR-184 expression. Transfection of glioma cells with a miR-184 mimic inhibited invasion, suppressed colony formation, and reduced anchorage-independent growth in soft agar. Similar phenotypes were evident when SND1 was knocked down with siRNA. Additionally, knockdown (KD) of SND1 induced senescence and improved the chemoresistant properties of malignant glioma cells. In an orthotopic xenograft model, KD of SND1 or transfection with a miR-184 mimic induced a less invasive tumor phenotype and significantly improved survival of tumor bearing mice.

CONCLUSIONS

Our study is the first to show a novel regulatory role of SND1, a direct target of miR-184, in glioma progression, suggesting that the miR-184/SND1 axis may be a useful diagnostic and therapeutic tool for malignant glioma.

Genetically engineered mice as experimental tools to dissect the critical events in breast cancer

Elucidating the mechanism of pathogenesis of breast cancer has greatly benefited from breakthrough advances in both genetically engineered mouse (GEM) models and xenograft transplantation technologies. The vast array of breast cancer mouse models currently available is testimony to the complexity of mammary tumorigenesis and attempts by investigators to accurately portray the heterogeneity and intricacies of this disease. Distinct molecular changes that drive various aspects of tumorigenesis, such as alterations in tumor cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and drug resistance have been evaluated using the currently available GEM breast cancer models. GEM breast cancer models are also being exploited to evaluate and validate the efficacy of novel therapeutics, vaccines, and imaging modalities for potential use in the clinic. This review provides a synopsis of the various GEM models that are expanding our knowledge of the nuances of breast cancer development and progression and can be instrumental in the development of novel prevention and therapeutic approaches for this disease.

MDA-9/syntenin is a key regulator of glioma pathogenesis

BACKGROUND

The extraordinary invasiveness of human glioblastoma multiforme (GBM) contributes to treatment failure and the grim prognosis of patients diagnosed with this tumor. Consequently, it is imperative to define further the cellular mechanisms that control GBM invasion and identify promising novel therapeutic targets. Melanoma differentiation associated gene-9 (MDA-9/syntenin) is a highly conserved PDZ domain-containing scaffolding protein that promotes invasion and metastasis in vitro and in vivo in human melanoma models. To determine whether MDA-9/syntenin is a relevant target in GBM, we investigated its expression in tumor samples and involvement in GBM invasion and angiogenesis.

MATERIALS

We assessed MDA-9/syntenin levels in available databases, patient tumor samples, and human-derived cell lines. Through gain-of-function and loss-of-function studies, we analyzed changes in invasion, angiogenesis, and signaling in vitro. We used orthotopic xenografts with GBM6 cells to demonstrate the role of MDA-9/syntenin in GBM pathogenesis in vivo.

RESULTS

MDA-9/syntenin expression in high-grade astrocytomas is significantly higher than normal tissue counterparts. Forced overexpression of MDA-9/syntenin enhanced Matrigel invasion, while knockdown inhibited invasion, migration, and anchorage-independent growth in soft agar. Moreover, overexpression of MDA-9/syntenin increased activation of c-Src, p38 mitogen-activated protein kinase, and nuclear factor kappa-B, leading to elevated expression of matrix metalloproteinase 2 and secretion of interleukin-8 with corresponding changes observed upon knockdown. GBM6 cells that stably express small hairpin RNA for MDA-9/syntenin formed smaller tumors and had a less invasive phenotype in vivo.

CONCLUSIONS

Our findings indicate that MDA-9/syntenin is a novel and important mediator of invasion in GBM and a key regulator of pathogenesis, and we identify it as a potential target for anti-invasive treatment in human astrocytoma.

Novel role of MDA-9/syntenin in regulating urothelial cell proliferation by modulating EGFR signaling

PURPOSE

Urothelial cell carcinoma (UCC) rapidly progresses from superficial to muscle-invasive tumors. The key molecules involved in metastatic progression and its early detection require clarification. The present study defines a seminal role of the metastasis-associated gene MDA-9/Syntenin in UCC progression.

EXPERIMENTAL DESIGN

Expression pattern of MDA-9/Syntenin was examined in 44 primary UCC and the impact of its overexpression and knockdown was examined in multiple cells lines and key findings were validated in primary tumors.

RESULTS

Significantly higher (P=0.002-0.003) expression of MDA-9/Syntenin was observed in 64% (28 of 44) of primary tumors and an association was evident with stage (P=0.01), grade (P=0.03), and invasion status (P=0.02). MDA-9/Syntenin overexpression in nontumorigenic HUC-1 cells increased proliferation (P=0.0012), invasion (P=0.0001), and EGF receptor (EGFR), AKT, phosphoinositide 3-kinase (PI3K), and c-Src expression. Alteration of β-catenin, E-cadherin, vimentin, claudin-1, ZO-1, and T-cell factor-4 (TCF4) expression was also observed. MDA-9/Syntenin knockdown in three UCC cell lines reversed phenotypic and molecular changes observed in the HUC-1 cells and reduced in vivo metastasis. Key molecular changes observed in the cell lines were confirmed in primary tumors. A physical interaction and colocalization of MDA-9/Syntenin and EGFR was evident in UCC cell lines and primary tumors. A logistic regression model analysis revealed a significant correlation between MDA-9/Syntenin:EGFR and MDA-9/Syntenin:AKT expressions with stage (P=0.04, EGFR; P=0.01, AKT). A correlation between MDA-9/Syntenin:β-catenin coexpression with stage (P=0.03) and invasion (P=0.04) was also evident.

CONCLUSIONS

Our findings indicate that MDA-9/Syntenin might provide an attractive target for developing detection, monitoring, and therapeutic strategies for managing UCC.

Targeting breast cancer-initiating/stem cells with melanoma differentiation-associated gene-7/interleukin-24

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) displays a broad range of antitumor properties including cancer-specific induction of apoptosis, inhibition of tumor angiogenesis and modulation of antitumor immune responses. In our study, we elucidated the role of MDA-7/IL-24 in inhibiting growth of breast cancer-initiating/stem cells. Ad.mda-7 infection decreased proliferation of breast cancer-initiating/stem cells without affecting normal breast stem cells. Ad.mda-7 induced apoptosis and endoplasmic reticulum stress in breast cancer-initiating/stem cells similar to unsorted breast cancer cells and inhibited the self-renewal property of breast cancer-initiating/stem cells by suppressing Wnt/β-catenin signaling. Prevention of inhibition of Wnt signaling by LiCl increased cell survival upon Ad.mda-7 treatment, suggesting that Wnt signaling inhibition might play a key role in MDA-7/IL-24-mediated death of breast cancer-initiating/stem cells. In a nude mouse subcutaneous xenograft model, Ad.mda-7 injection profoundly inhibited growth of tumors generated from breast cancer-initiating/stem cells and also exerted a potent "bystander" activity inhibiting growth of distant uninjected tumors. Further studies revealed that tumor growth inhibition by Ad.mda-7 was associated with a decrease in proliferation and angiogenesis, two intrinsic features of MDA-7/IL-24, and a reduction in vivo in the percentage of breast cancer-initiating/stem cells. Our findings demonstrate that MDA-7/IL-24 is not only nontoxic to normal cells and normal stem cells but also can kill both unsorted cancer cells and enriched populations of cancer-initiating/stem cells, providing further documentation that MDA-7/IL-24 might be a safe and effective way to eradicate cancers and also potentially establish disease-free survival.

Selected approaches for rational drug design and high throughput screening to identify anti-cancer molecules

Structure-based modeling combined with rational drug design, and high throughput screening approaches offer significant potential for identifying and developing lead compounds with therapeutic potential. The present review focuses on these two approaches using explicit examples based on specific derivatives of Gossypol generated through rational design and applications of a cancer-specificpromoter derived from Progression Elevated Gene-3. The Gossypol derivative Sabutoclax (BI-97C1) displays potent anti-tumor activity against a diverse spectrum of human tumors. The model of the docked structure of Gossypol bound to Bcl-XL provided a virtual structure-activity-relationship where appropriate modifications were predicted on a rational basis. These structure-based studies led to the isolation of Sabutoclax, an optically pure isomer of Apogossypol displaying superior efficacy and reduced toxicity. These studies illustrate the power of combining structure-based modeling with rational design to predict appropriate derivatives of lead compounds to be empirically tested and evaluated for bioactivity. Another approach to cancer drug discovery utilizes a cancer-specific promoter as readouts of the transformed state. The promoter region of Progression Elevated Gene-3 is such a promoter with cancer-specific activity. The specificity of this promoter has been exploited as a means of constructing cancer terminator viruses that selectively kill cancer cells and as a systemic imaging modality that specifically visualizes in vivo cancer growth with no background from normal tissues. Screening of small molecule inhibitors that suppress the Progression Elevated Gene-3-promoter may provide relevant lead compounds for cancer therapy that can be combined with further structure-based approaches leading to the development of novel compounds for cancer therapy.

Innovative approaches for enhancing cancer gene therapy

Gene therapy provides a novel platform for therapeutic intervention of several genetic and non-genetic disorders. With the recent developments in the field, a wide variety of viral and non-viral vectors have emerged that can deliver genetic payloads to target cells. However, non-targeted delivery of transgenes often results in undesirable effects, low tumor transduction, and reduced therapeutic index. In this review, we focus on some of the novel approaches that can be used to meet the present challenges in the field and translate the potential of cancer gene therapy from 'bench to bedside' in the near future.

Abstract 2403: DNAJB6 suppresses the Wnt/β-catenin pathway

DNAJB6 is an HSP40 family protein which plays an important role in regulating tumorigenicity and metastasis of breast cancer and melanoma. Expression of DNAJB6 is found to be reduced in advanced stages of the disease. Restoration of its expression significantly decreases tumor growth and metastasis in xenograft studies. DNAJB6 expressing cells also show altered morphology, gain in epithelial markers and loss of mesenchymal markers and increased expression of DKK1, a secreted Wnt/β-catenin signaling. Our current studies elaborate the intricate mechanistic details about contributions of DNAJB6 to the negative regulation of the Wnt/β-catenin pathway. We describe the important role of the “J” domain of DNAJB6 in inhibiting Wnt/β-catenin. Deletion of “J” domain renders DNAJB6 incapable of impeding tumor growth and metastasis. Co-immunoprecipitation, mammalian-two-hybrid and FPLC studies show that DNAJB6 can form a multimeric complex with HSPA8 (HSC70), GSK3β and PP2A. DNAJB6 binds HSC70 and dephosphorylates GSK3β by recruiting PP2A. Activated GSK3β in-turn degrades β-catenin protein. Deletion of the J domain does not allow the formation of this multiprotein complex, which inactivates GSK3β and restores β-catenin levels. We further noted that the morphology of the cells grown in three dimensional matrix show distinct difference in WT-DNAJB6 and J-domain deleted expressors. In vivo and in vitro studies done with J domain deleted expressors showed increased malignancy. We also demonstrate the importance of J domain of DNAJB6 in suppressing osteopontin as one of the critical factors contributing to its reduced malignant activity in suppressing invasion and growth of xenografts. In summary, our studies unravel a novel mechanistic role of DNAJB6 in regulating GSK3β, a critical kinase which restricts tumor progression.

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 2403. doi:1538-7445.AM2012-2403

Cellular stress stimulates nuclear localization signal (NLS) independent nuclear transport of MRJ

HSP40 family member MRJ (DNAJB6) has been in the spot light for its relevance to Huntington's, Parkinson's diseases, limb-girdle muscular dystrophy, placental development, neural stem cells, cell cycle and malignancies such as breast cancer and melanoma. This gene has two spliced variants coding for 2 distinct proteins with significant homology. However, MRJ(L) (large variant) is predominantly localized to the nucleus whereas MRJ(S) (small variant) is predominantly cytoplasmic. Interestingly MRJ(S) translocates to the nucleus in response to heat shock. The classical heat shock proteins respond to crises (stress) by increasing the number of molecules, usually by transcriptional up-regulation. Our studies imply that a quick increase in the molar concentration of MRJ in the nuclear compartment is a novel method by which MRJ responds to stress. We found that MRJ(S) shows NLS (nuclear localization signal) independent nuclear localization in response to heat shock and hypoxia. The specificity of this response is realized due to lack of such response by MRJ(S) when challenged by other stressors, such as some cytokines or UV light. Deletion analysis has allowed us to narrow down on a 20 amino acid stretch at the C-terminal region of MRJ(S) as a potential stress sensing region. Functional studies indicated that constitutive nuclear localization of MRJ(S) promoted attributes of malignancy such as proliferation and invasiveness overall indicating distinct phenotypic characteristics of nuclear MRJ(S).

DNAJB6 chaperones PP2A mediated dephosphorylation of GSK3β to downregulate β-catenin transcription target, osteopontin

Elevated levels of the oncoprotein, osteopontin (OPN), are associated with poor outcome of several types of cancers including melanoma. We have previously reported an important involvement of DNAJB6, a member of heat-shock protein 40 (HSP40) family, in negatively impacting tumor growth. The current study was prompted by our observations reported here which revealed a reciprocal relationship between DNAJB6 and OPN in melanoma specimens. The 'J domain' is the most conserved domain of HSP40 family of proteins. Hence, we assessed the functional role of the J domain in activities of DNAJB6. We report that the J domain of DNAJB6 is involved in mediating OPN suppression. Deletion of the J domain renders DNAJB6 incapable of impeding malignancy and suppressing OPN. Our mechanistic investigations reveal that DNAJB6 binds HSPA8 (heat-shock cognate protein, HSC70) and causes dephosphorylation of glycogen synthase kinase 3β (GSK3β) at Ser 9 by recruiting protein phosphatase, PP2A. This dephosphorylation activates GSK3β, leading to degradation of β-catenin and subsequent loss of TCF/LEF (T cell factor1/lymphoid enhancer factor1) activity. Deletion of the J domain abrogates assembly of this multiprotein complex and renders GSK3β inactive, thus, stabilizing β-catenin, a transcription co-activator for OPN expression. Our in-vitro and in-vivo functional analyses show that silencing OPN expression in the background of deletion of the J domain renders the resultant tumor cells less malignant despite the presence of stabilized β-catenin. Thus, we have uncovered a new mechanism for regulation of GSK3β activity leading to inhibition of Wnt/β-catenin signaling.

Dickkopf1: a tumor suppressor or metastasis promoter?

Dickkopf1 (DKK1), a secreted inhibitor of the Wnt/β-catenin pathway, is a negative regulator of bone formation. DKK1 acts as a switch that transitions prostate cancer bone metastases from osteolytic to osteoblastic and also is an active indicator of poor outcome for multiple myeloma. However, in other tumor types, DKK1 upregulation or overexpression suppresses tumor growth. Thus, the role of DKK1 in cancer appears to be diverse. This raises a question: Could the increased levels of DKK1 still be tumor protective when observed in high levels in the serum of patients? Here, we summarize the diverse, seemingly contradicting roles of DKK1 and attempt to explain the apparent dichotomy in its activity. We propose that DKK1 is a critical secreted factor that modulates microenvironment. Based on the location and components of the microenvironment DKK1 will support different outcomes.

Abstract 997: Stability of β-catenin decides the tumor suppressive effect of MRJ

Mammalian relative of DnaJ (MRJ), is a member of the heat shock protein 40 family. We have found that MRJ is lost in advanced grades of breast cancer. Functional studies showed that ectopic expression of the large spliced variant of MRJ, MRJ(L), results in reduced malignant properties as indicated by reduced motility, migration, invasion and soft agar colonization. Furthermore, xenograft studies in athymic mice showed that MRJ(L) expression reduced tumor growth and metastasis. Our investigations also revealed that Wnt/β-catenin signaling is one of the pathways impacted by MRJ(L) expression. Specifically, we found that MRJ(L) expression led to enhanced degradation of β-catenin. Our studies showed that MRJ(L) mediated its tumor suppressive effects by upregulation of DKK1, a negative regulator of Wnt/β-catenin signaling, which promotes proteosome mediated degradation of β-catenin. Hence, we hypothesized that introduction of a degradation-resistant form of β-catenin will lead to restoration of malignant attributes of the MRJ(L) expressing cells. S37A mutation of β-catenin has been known to render it insensitive to ubiquitination-mediated proteosomal degradation. We established stable clones co-expressing S37A β-catenin and MRJ(L). Our analysis of these clones showed that the TCF/LEF activity, as a measure of Wnt/β-catenin signaling, was elevated 10 fold, as measured by the increased activity of the luciferase reporter, TOPFlash. We also found that downstream transcriptional target of Wnt/β-catenin signaling, cyclin D1 showed increased expression in S37A β-catenin clones as compared to the MRJ(L) expressors. Synchronized cell cycle analysis demonstrated that cells co-expressing S37A β-catenin and MRJ(L) resulted in marked increase in S phase at 2 and 24 hours after the release of cell cycle block. The MRJ(L) expressors; did not go through an increase in the S phase in the 24 hour period after the release. Analysis of tumor growth in vivo (xenograft model) revealed that S37A β-catenin was able to restore the malignant activity overriding the suppressive effect of MRJ(L). Thus controlled degradation of β-catenin, brought about by MRJ(L), is an important event in maintaining cells in a non-tumorigenic state.

Acknowledgement: We acknowledge grant support from the NCI: 1R01CA140472

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 997. doi:10.1158/1538-7445.AM2011-997

DNAJB6 induces degradation of beta-catenin and causes partial reversal of mesenchymal phenotype

We showed that expression of MRJ (DNAJB6) protein is lost in invasive ductal carcinoma, and restoration of MRJ(L) restricts malignant behavior of breast cancer and melanoma cells. However, the signaling pathways influenced by MRJ(L) are largely unknown. Our observations revealed that MRJ(L) expression causes changes in cell morphology concomitant with down-regulation of several mesenchymal markers, viz. vimentin, N-cadherin, Twist, and Slug, and up-regulation of epithelial marker keratin 18. Importantly, MRJ(L) expression led to reduced levels of beta-catenin, an epithelial mesenchymal transition marker, and a critical player in the Wnt pathway. We found that MRJ(L) up-regulates expression of DKK1, a well known Wnt/beta-catenin signaling inhibitor, that causes degradation of beta-catenin. Re-expression of DNAJB6 alters the Wnt/beta-catenin signaling in cancer cells, leading to partial reversal of the mesenchymal phenotype. Thus, MRJ(L) may play a role in maintaining an epithelial phenotype, and inhibition of the Wnt/beta-catenin pathway may be one of the potential mechanisms contributing to the restriction of malignant behavior by MRJ(L).

Abstract 2289: MRJ(L) reverts mesenchymal phenotype and restricts malignancy by inhibiting Wnt/β-catenin signaling

Expression of MRJ (Hsp40/DNAJB6) is lost in advanced infiltrating ductal carcinoma. We found that ectopic expression of the large isoform of MRJ, MRJ(L), is functionally capable of retarding tumor growth. Our continuing efforts towards understanding the effect of MRJ(L) expression on cancer cells revealed that MRJ(L) caused morphological changes indicative of epithelial-like appearance. It decreased the expression of several mesenchymal markers such as N-cadherin, Twist, Slug, vimentin and up regulated epithelial marker, Keratin 18. However, most noticeable was the loss of β-catenin protein upon MRJ(L) expression. Differential-proteomic analysis of the secretome showed that MRJ(L) expression elevated DKK1 (Dickkopf1), a secreted inhibitor of Wnt/β-catenin signaling. Increased DKK1 levels enhanced proteosome mediated degradation of β-catenin and reduced Wnt/β-catenin signaling as measured by the TCF/LEF reporter activity in MRJ(L) expressors. Furthermore we found that silencing MRJ(L) from immortalized mammary epithelial cell line, MCF10A, led to decreased DKK1 and E-cadherin levels, with concomitant increase of β-catenin protein. We also found that silencing DKK1 from the MRJ(L) overespressing cancer lines led to increased malignant behavior as measured by foci formation, growth in soft agar and wound healing capacity. Overall, our findings lead us to conclude that MRJ(L) maintains the epithelial phenotype and restricts malignant behavior of tumor cells by inhibiting Wnt/β-catenin pathway.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2289.

TT virus infection in children and adults who visited a general hospital in the south of Brazil for routine procedure

TT virus (TTV) is a newly described nonenveloped human virus, with a circular, negative-stranded DNA genome, that was first identified in the blood of a patient with posttransfusion hepatitis of unknown etiology. PCR primers and conditions used for TTV DNA amplification may greatly influence the level of TTV detection in serum. Three PCR assays, with different regions of the genome as targets, were used to test TTV DNA in 130 sera from children and adults visiting a hospital in the south of Brazil, most of them for routine procedure. Forty-four percent of adult sera and 73% of sera from children aged 0-10 years were TTV positive with at least one PCR assay. However, the three assays were able to detect only 33%, 35%, and 70% of the total positive samples. Our results showed a high prevalence of TTV infection in the south of Brazil, particularly among young children, and confirmed the necessity of performing several PCR assays to assess the true TTV prevalence in a determined population.

Cardiac tamponade in systemic lupus erythematosus. Report of four cases

OBJECTIVE

To report and assess the incidence of cardiac tamponade in systemic lupus erythematosus as a cardiac manifestation of the disease.

METHODS

We reviewed the medical records of 325 patients diagnosed with systemic lupus erythematosus according to the American Rheumatism Association and their complementary laboratory tests compatible with cardiac tamponade.

RESULTS

In the 325 medical records reviewed, we found 108 patients with pericardial effusions corresponding to 33.2% of the total and 54% of the patients studied in the active phase of the disease. Clinical assessment and transthoracic echocardiogram allowed the clinical diagnosis of cardiac tamponade in only 4 (1.23%) patients, 3 of whom were females, white, with ages ranging from 25 to 44 years. The pericardial fluid was hemorrhagic or serosanguineous with high levels of FAN and positivity for LE cells. In the treatment, we successfully used pericardiocentesis associated with high doses of corticosteroids. In clinical and laboratory follow-up performed for a period of 3 years, neither recrudescence of the pericardial effusion nor evolution to constriction occurred.

CONCLUSION

Even though rare (1.23%), cardiac tamponade in patients with systemic lupus erythematosus has a benign evolution when properly treated, according to our experience.

Chlamydia pneumoniae and atherosclerosis. Identification of bacterial DNA in the arterial wall

OBJECTIVE

The intracellular Gram-negative bacterium Chlamydia pneumoniae has been associated with atherosclerosis. The presence of Chlamydia pneumoniae has been investigated in fragments of the arterial wall with a technique for DNA identification.

METHODS

Arterial fragments obtained from vascular surgical procedures in 58 patients were analyzed. From these patients, 39 were males and the mean age was 65+/-6 years. The polymerase chain reaction was used to identify the bacterial DNA with a pair of primers that codify the major outer membrane protein (MOMP) of Chlamydia pneumoniae. The amplified product was visualized by electrophoresis in the 2% agarose gel stained with ethidium bromide, and it was considered positive when migrating in the band of molecular weight of the positive controls.

RESULTS

Seven (12%) out of the 58 patients showed positive results for Chlamydia pneumoniae.

CONCLUSION

DNA from Chlamydia pneumoniae was identified in the arterial wall of a substantial number of patients with atherosclerosis. This association, which has already been described in other countries, corroborates the evidence favoring a role played by Chlamydia pneumoniae in atherogenesis.

[Cardiac involvement in systemic lupus erythematosus. An echocardiographic evaluation]

PURPOSE

To study, by a non-invasive method, patients with systemic lupus erythematosus (SLE), to evaluate possible cardiac involvement.

METHODS

A hundred-eight lupic patients, 60 of them during activity, were studied, independently of cardiovascular signs and symptoms, by M-mode and two-D echocardiography and Doppler. Among the patients in the acute phase, 19 had never used steroid therapy before.

RESULTS

Echocardiographic evaluation showed cardiac involvement in all patients who were in clinical activity. Seven had myocardial involvement with systolic impairment. In 35 patients, pericardial effusion was found, all in the acute phase. Regarding endocardial involvement, there were valve thickening in 54 patients in group I (acute phase), valve vegetations in eight and one with mitral valve prolapse. There were only six with valve thickening in group II (remission). Pulmonary hypertension was observed in 15 patients in the activity group and in two during remission.

CONCLUSION

Echocardiogram has showed how frequent cardiac involvement is in SLE, especially during disease activity and being independent of previous steroid therapy. As it is a non-invasive method, it could be used in a routine protocol in the evaluation and follow-up of these patients.

The lac permease of Escherichia coli: site-directed mutagenesis studies on the mechanism of beta-galactoside/H+ symport

In this communication, we summarize site-directed mutagenesis studies of the lac permease from Escherichia coli, a prototypic H(+)-coupled active transport protein. We classify mutant permeases by phenotype, and suggest possible roles for some individual residues in the mechanism of H+/lactose symport. Although high-resolution structural information is not presently available, kinetic analysis of the partial reactions catalysed by the mutant permeases, as well as biophysical studies, suggest an evolving model for the mechanism of H+/lactose symport.