Our recent study showed critical roles of Dmp1 as a sensor of oncogenic Ras, HER2/neu signaling and activation of the Arf-p53 pathway. To elucidate the role of human DMP1 (hDMP1) in breast cancer, one hundred and ten pairs of human breast cancer specimen were studied for the alterations of the hDMP1-ARF-Hdm2-p53 pathway with follow up of clinical outcomes. Loss of heterozygosity (LOH) of the hDMP1 locus was found in 42% of human breast carcinomas, while that of INK4a/ARF and p53 were found in 20% and 34%, respectively. Hdm2 amplification was found in 13% of the same sample, which was found independently of LOH for hDMP1. Conversely, LOH for hDMP1 was found in mutually exclusive fashion with that of INK4a/ARF and p53, and was associated with low Ki67 index and diploid karyotype. Consistently, LOH for hDMP1 was associated with luminal A category and longer relapse-free survival, while that of p53 was associated with non-luminal A and shorter survival. Thus, loss of hDMP1 could define a new disease category associated with prognosis of breast cancer patients. Human breast epithelial cells/cancer cells with wild-type p53 were sensitive to growth inhibition by activated Dmp1:ER while those that delete p14ARF or p53, and/or Hdm2 amplification showed partial or nearly complete resistance, indicating that p53 is a critical target for hDMP1 to exhibit its biological activity.
Dmp1 (Dmtf1); breast cancer; loss of heterozygosity; relapse-free survival; Ki67; prognostic marker
Lung cancer is the most lethal carcinoma worldwide. Mutations of p53, inactivation of p16INK4a, and overexpression of cyclins E, A and B are independently associated with poor prognoses of patients, while the prognostic value of cyclin D1 or RB expression is inconclusive. Cyclin D binding myb-like protein 1 (Dmp1) encodes a DNA binding protein that receives signals from oncogenic Ras and functions as a tumor suppressor by activating the Arf-p53 pathway. Dmp1 has been shown to be haplo-insufficient for tumor suppression in mouse models including K-ras-mediated lung carcinogenesis. The human DMP1 gene is located on chromosome 7q21, and our recent results revealed that the hDMP1 gene is deleted, but not mutated or silenced, in approximately 40 % of human non-small-cell lung carcinomas. These cases typically retained wild-type ARF and p53 and expressed very low levels of the hDMP1 protein. Thus, hDMP1 loss could be a novel diagnostic marker for non-small-cell lung carcinomas.
ARF; DMP1l; haploid insufficiency; immunohistochemistryl; LOHl; loss of heterozygosity; lung cancer; p16INK4a; p53; Ras; tumor-suppressor gene
Ferroportin and hepcidin are critical proteins for the regulation of systemic iron homeostasis. Ferroportin is the only known mechanism for export of intracellular non–heme-associated iron; its stability is regulated by the hormone hepcidin. Although ferroportin profoundly affects concentrations of intracellular iron in tissues important for systemic iron absorption and trafficking, ferroportin concentrations in breast cancer and their influence on growth and prognosis have not been examined. We demonstrate here that both ferroportin and hepcidin are expressed in cultured human breast epithelial cells and that hepcidin regulates ferroportin in these cells. Further, ferroportin protein is substantially reduced in breast cancer cells compared to nonmalignant breast epithelial cells; ferroportin protein abundance correlates with metabolically available iron. Ferroportin protein is also present in normal human mammary tissue and markedly decreased in breast cancer tissue, with the highest degree of anaplasia associated with lowest ferroportin expression. Transfection of breast cancer cells with ferroportin significantly reduces their growth after orthotopic implantation in the mouse mammary fat pad. Gene expression profiles in breast cancers from >800 women reveal that decreased ferroportin gene expression is associated with a significant reduction in metastasis-free and disease-specific survival that is independent of other breast cancer risk factors. High ferroportin and low hepcidin gene expression identifies an extremely favorable cohort of breast cancer patients who have a 10-year survival of >90%. Ferroportin is a pivotal protein in breast biology and a strong and independent predictor of prognosis in breast cancer.
Polymorphisms in phase I and phase II enzymes may enhance the occurrence of mutations at critical tumor suppressor genes, such as p53, and increase breast cancer risk by either increasing the activation or detoxification of carcinogens and/or endogenous estrogens. We analyzed polymorphisms in CYP1B1, GSTM1, GSTT1, and GSTP1 and p53 mutations in 323 breast tumor samples. Approximately 11% of patients exhibited mutations in p53. Women with mutations had a significantly younger age of diagnosis (P = 0.01) and a greater incidence of tumors classified as stage II or higher (P = 0.002). More women with mutations had a history of smoking (55%) compared to women without mutations (39%). Although none of the genotypes alone were associated with p53 mutations, positive smoking history was associated with p53 mutations in women with the GSTM1 null allele [OR = 3.54; 95% CI = 0.97–12.90 P = 0.06] compared to women with the wild-type genotype and smoking history [OR = 0.62, 95% CI = 0.19–2.07], although this association did not reach statistical significance. To test for gene–gene interactions, our exploratory analysis in the Caucasian cases suggested that individuals with the combined GSTP1 105 VV, CYP1B1 432 LV/VV, and GSTM1 positive genotype were more likely to harbor mutations in p53 [OR = 4.94; 95% CI = 1.11–22.06]. Our results suggest that gene–smoking and gene–gene interactions may impact the prevalence of p53 mutations in breast tumors. Elucidating the etiology of breast cancer as a consequence of common genetic polymorphisms and the genotoxic effects of smoking will enable us to improve the design of prevention strategies, such as lifestyle modifications, in genetically susceptible subpopulations.
breast cancer; p53; polymorphisms; drug metabolism
Studies have suggested that the nuclear receptor corepressor 1 (NCOR1) could play an important role in human cancers. However, the detailed molecular mechanisms by which it functions in vivo to affect cancer progression are not clear. The present study elucidated the in vivo actions of NCOR1 in carcinogenesis using a mouse model (ThrbPV/PV mice) that spontaneously develops thyroid cancer. ThrbPV/PV mice harbor a dominantly negative thyroid hormone receptor β (TRβ) mutant (denoted as PV). We adopted the loss-of-the function approach by crossing ThrbPV mice with mice that globally express an NCOR1 mutant protein (NCOR1ΔID) in which the receptor interaction domains have been modified so that it cannot interact with the TRβ, or PV, in mice. Remarkably, expression of NCOR1ΔID protein reduced thyroid tumor growth, markedly delayed tumor progression, and prolonged survival of ThrbPV/PVNcor1ΔID/ΔID mice. Tumor cell proliferation was inhibited by increased expression of cyclin-dependent kinase inhibitor 1 (p21waf1/cip1; Cdkn1A), and apoptosis was activated by elevated expression of pro-apoptotic BCL-Associated X (Bax). Further analyses showed that p53 was recruited to the p53-binding site on the proximal promoter of the Cdkn1A and the Bax gene as a co-repressor complex with PV/NCOR1/histone deacetylas-3 (HDAC-3), leading to repression of the Cdkn1A as well as the Bax gene in thyroids of ThrbPV/PV mice. In thyroids of ThrbPV/PVNcor1ΔID/ΔID mice, the p53/PV complex could not recruit NCOR1ΔID and HDAC-3, leading to de-repression of both genes to inhibit cancer progression. The present studies provided direct evidence in vivo that NCOR1 could function as an oncogene via transcription regulation in a mouse model of thyroid cancer.
Gene expression signatures indicative of tumor proliferative capacity and tumor-immune cell interactions have emerged as principal biology-driven predictors of breast cancer outcomes. How these signatures relate to one another in biological and prognostic contexts remains to be clarified.
To investigate the relationship between proliferation and immune gene signatures, we analyzed an integrated dataset of 1,954 clinically annotated breast tumor expression profiles randomized into training and test sets to allow two-way discovery and validation of gene-survival associations. Hierarchical clustering revealed a large cluster of distant metastasis-free survival-associated genes with known immunological functions that further partitioned into three distinct immune metagenes likely reflecting B cells and/or plasma cells; T cells and natural killer cells; and monocytes and/or dendritic cells. A proliferation metagene allowed stratification of cases into proliferation tertiles. The prognostic strength of these metagenes was largely restricted to tumors within the highest proliferation tertile, though intrinsic subtype-specific differences were observed in the intermediate and low proliferation tertiles. In highly proliferative tumors, high tertile immune metagene expression equated with markedly reduced risk of metastasis whereas tumors with low tertile expression of any one of the three immune metagenes were associated with poor outcome despite higher expression of the other two metagenes.
These findings suggest that a productive interplay among multiple immune cell types at the tumor site promotes long-term anti-metastatic immunity in a proliferation-dependent manner. The emergence of a subset of effective immune responders among highly proliferative tumors has novel prognostic ramifications.
Breast cancer; gene signatures; hierarchical clustering; immune metagene; intrinsic subtypes; metagene tertiles; multivariable analysis; prognosis; proliferation metagene; survival analysis
Src is over-expressed or hyper-activated in a variety of human cancers including thyroid carcinoma. Src is a central mediator in multiple signaling pathways that are important in oncogenesis and cancer progression. In this study, we evaluated the effects of a Src inhibitor, SKI-606 (bosutinib), in a spontaneous metastatic thyroid cancer model with constitutively activated Src (ThrbPV/PVPten+/− mice).
ThrbPV/PVPten+/− mice were treated with SKI-606 or vehicle controls, beginning at 6 weeks of age until the mice succumbed to thyroid cancer. We assessed the effects of SKI-606 on thyroid cancer progression and analyzed the impact of SKI-606 on aberrant Src-mediated signaling.
SKI-606 effectively inhibited aberrant activation of Src and its downstream targets to markedly inhibit the growth of thyroid tumor, thereby prolonging the survival of treated mice. While Src inhibition did not induce cell apoptosis, it decreased cell proliferation by affecting the expression of key regulators of cell cycle progression. Importantly, SKI-606 dramatically prevented de-differentiation, vascular invasion, and lung metastasis of thyroid cancer cells. These responses were meditated by down-regulation of mitogen-activated protein kinase pathways and inhibition of the epithelial-mesenchymal transition.
Our findings suggest that Src is critical in the progression of thyroid cancer, making oral SKI-606 a promising treatment strategy for refractory thyroid cancer.
Thyroid cancer; Src; SKI-606; metastasis; epithelial-mesenchymal transition; mouse model
Accumulated evidence suggests that thyroid hormone receptor β (TRβ) could function as a tumor suppressor, but the detailed mechanisms by which TRβ inhibits tumorigenesis are not fully understood. The present studies explored the mechanisms by which TRβ acted to inhibit thyroid tumor development mediated by simian virus-40 (SV40). In mouse xenograft models, SV40 large T antigen (SV40Tag)-immortalized human thyroid epithelial (HTori) cells rapidly induced tumors, but the tumor development was totally blocked by TRβ stably expressed in HTori cells. Previous studies showed that the SV40Tag oncoprotein binds to and inactivates tumor suppressors p53 and retinoblastoma protein (Rb), thereby inducing tumorigenesis. Here we showed that one of the mechanisms by which TRβ suppressed tumor development was by competing with p53 and Rb for binding to SV40Tag. The interaction of TRβ with SV40Tag led to reactivation of Rb to inhibit cell cycle progression. TRβ- SV40Tag interaction also resulted in reactivating p53 to increase the expression of Pten, thus attenuating PI3K-AKT signaling to decrease cell proliferation and to induce apoptosis. The present study uncovered a novel action of TRβ as a tumor suppressor initiated via interfering with the recruitment of Rb and p53 by SV40Tag oncoprotein through protein-protein interaction, thereby acting to block tumor development.
Thyroid hormone receptor; tumor suppressor; tumorigenesis; thyroid hormone; xenograft models
Vesicular stomatitis virus (VSV) is a potential oncolytic virus for treating glioblastoma multiforme (GBM), an aggressive brain tumor. Matrix (M) protein mutants of VSV have shown greater selectivity for killing GBM cells versus normal brain cells than VSV with wild-type M protein. The goal of this research was to determine the contribution of death receptor and mitochondrial pathways to apoptosis induced by an M protein mutant (M51R) VSV in U87 human GBM tumor cells. Compared to controls, U87 cells expressing a dominant negative form of Fas (dnFas) or overexpressing Bcl-XL had reduced caspase-3 activation following infection with M51R VSV, indicating that both the death receptor pathway and mitochondrial pathways are important for M51R VSV-induced apoptosis. Death receptor signaling has been classified as type I or type II, depending on whether signaling is independent (type I) or dependent on the mitochondrial pathway (type II). Bcl-XL overexpression inhibited caspase activation in response to a Fas-inducing antibody, similar to the inhibition in response to M51R VSV infection, indicating that U87 cells behave as type II cells. Inhibition of apoptosis in vitro delayed, but did not prevent, virus-induced cell death. Murine xenografts of U87 cells that overexpress Bcl-XL regressed with a time course similar to that of control cells following treatment with M51R VSV, and tumors were not detectable at 21 days postinoculation. Immunohistochemical analysis demonstrated similar levels of viral antigen expression but reduced activation of caspase-3 following virus treatment of Bcl-XL-overexpressing tumors compared to controls. Further, the pathological changes in tumors following treatment with virus were quite different in the presence versus the absence of Bcl-XL overexpression. These results demonstrate that M51R VSV efficiently induces oncolysis in GBM tumor cells despite deregulation of apoptotic pathways, underscoring its potential use as a treatment for GBM.
HER2 overexpression stimulates cell growth in p53-mutated cells while it inhibits cell proliferation in those with wild-type p53, but the molecular mechanism is unknown. The Dmp1 promoter was activated by HER2/neu through the PI3K-Akt-NF-κB pathway, which in turn stimulated Arf transcription. Binding of p65 and p52 subunits of NF-κB was demonstrated to the Dmp1 promoter and that of Dmp1 to the Arf promoter upon HER2/neu overexpression. Both Dmp1 and p53 were induced in pre-malignant lesions from MMTV-neu mice and mammary tumorigenesis was significantly accelerated in both Dmp1+/− and Dmp1−/− mice. Selective deletion of Dmp1 and/or overexpression of Tbx2/Pokemon was found in >50 % of wild-type HER2/neu carcinomas while the involvement of Arf, Mdm2, or p53 was rare. Tumors from Dmp1+/−, Dmp1−/−, and wild-type neu mice with hemizygous Dmp1 deletion showed significant downregulation of Arf and p21Cip1/WAF1, showing p53 inactivity and more aggressive phenotypes than tumors without Dmp1 deletion. Notably, endogenous hDMP1 mRNA decreased when HER2 was depleted in human breast cancer cells. Our study demonstrates the pivotal roles of Dmp1 in HER2/neu-p53 signaling and breast carcinogenesis.
Dmp1 (Dmtf1); HER2/neu; NF-κB; Arf; p53; Tbx2; Pokemon; breast cancer
Ferritin binds specifically and saturably to a variety of cell types, and recently several ferritin receptors have been cloned. TIM-2 is a specific receptor for H ferritin (HFt) in the mouse. TIM-2 is a member of the T cell immunoglobulin and mucin domain containing (TIM) protein family and plays an important role in immunity. The expression of TIM-2 outside of the immune system indicates that this receptor may have broader roles. We tested whether ferritin binding to TIM-2 can serve as an iron delivery mechanism. TIM-2 was transfected into normal (TCMK-1) mouse kidney cells, where it was appropriately expressed on the cell surface. HFt was labeled with 55Fe and 55Fe-HFt was incubated with TIM-2 positive cells or controls. 55Fe-HFt uptake was observed only in TIM-2 positive cells. HFt uptake was also seen in A20 B cells, which express endogenous TIM-2. TIM-2 levels were not increased by iron chelation. Uptake of 55Fe-HFt was specific and temperature-dependent. HFt taken up by TIM-2 positive cells transited through the endosome and eventually entered a lysosomal compartment, distinguishing the HFt pathway from that of transferrin, the classical vehicle for cellular iron delivery. Iron delivered following binding of HFt to TIM-2 entered the cytosol and became metabolically available, resulting in increased levels of endogenous intracellular ferritin. We conclude that TIM-2 can function as an iron uptake pathway.
In this study, we pilot tested an in vitro assay of cancer killing activity (CKA) in circulating leukocytes of 22 cancer cases and 25 healthy controls.
Using a human cervical cancer cell line, HeLa, as target cells, we compared the CKA in circulating leukocytes, as effector cells, of cancer cases and controls. The CKA was normalized as percentages of total target cells during selected periods of incubation time and at selected effector/target cell ratios in comparison to no-effector-cell controls.
Our results showed that CKA similar to that of our previous study of SR/CR mice was present in human circulating leukocytes but at profoundly different levels in individuals. Overall, males have a significantly higher CKA than females. The CKA levels in cancer cases were lower than that in healthy controls (mean ± SD: 36.97 ± 21.39 vs. 46.28 ± 27.22). Below-median CKA was significantly associated with case status (odds ratio = 4.36; 95% Confidence Interval = 1.06, 17.88) after adjustment of gender and race.
In freshly isolated human leukocytes, we were able to detect an apparent CKA in a similar manner to that of cancer-resistant SR/CR mice. The finding of CKA at lower levels in cancer patients suggests the possibility that it may be of a consequence of genetic, physiological, or pathological conditions, pending future studies with larger sample size.
Selective drugs targeting dysregulated oncogenic pathways are promising cancer therapies. Because the mammalian target of rapamycin complex 1 (mTORC1) pathway is hyperactivated in human follicular thyroid cancer (FTC), we hypothesized that its inhibition could block cancer development and progression. We, therefore, analyzed the effect of a treatment with a specific mTORC1 inhibitor (RAD001) in a faithful mouse model of FTC with constitutive mTORC1 activation (TRβPV/PVPten+/− mice). The treatment did not prevent capsular and vascular invasion of the thyroid and the occurrence of lung metastasis. However, it substantially decelerated thyroid tumor growth, thereby prolonging TRβPV/PVPten+/− mouse life span. RAD001 efficiently inhibited mTORC1 activity, as shown by the reduced phosphorylation of its downstream targets involved in the activity of the translation machinery, such as ribosomal S6 kinase (p70S6K), eukaryotic translation initiation factor 4E binding protein (4E-BP1) and the eukaryotic translation initiation factors eIF-4B and eIF-4G. Whereas mTORC1 signaling inhibition did not alter cell apoptosis, it induced a significant decrease in cell proliferation that was associated with the reduced abundance and altered activity of key regulators of cell cycle progression. Altogether, our data indicate that mTORC1 signaling plays a major role in the integration of the mitogenic signal in FTC. Therefore, our preclinical study with a relevant mouse model of FTC demonstrates for the first time that RAD001 efficaciously stabilizes cancer growth although it does not prevent its fatal outcome. In conclusion, our work underscores that in the treatment of FTC patients, RAD001 can only be used in combination with drugs and therapies inducing tumor shrinkage and blocking metastasis.
Mice may be useful for studies of skeletal aging, but there are limited data on changes in bone structure and strength over their lifespan. We obtained bones from female and male BALB/c mice at ages 2, 4, 7, 12 and 20 months and evaluated their structural, densitometric and mechanical properties. MicroCT of the mid-diaphysis of the femur and radius indicated that during skeletal growth (2–7 months) bone cross-sectional size (area, moment of inertia) increased rapidly; during aging (7–20 months) cortical area was maintained while moment of inertia continued to increase. Bones from females were smaller than males at young ages, but not at later ages. Changes in whole-bone stiffness and strength reflected the changes in bone size, with a rapid increase from 2–7 months followed by little or no change. In contrast, energy-to-fracture declined with aging. Cortical tissue mineral density (TMD) increased during growth and was maintained with aging. MicroCT of trabecular bone revealed age-related changes that were site-dependent. The proximal tibia showed a clear pattern of age-related decline in trabecular BV/TV, with progressive decreases after 4 months in both sexes; lumbar (L5) vertebra had more modest age-related declines; in contrast, caudal (Ca7) vertebra had increasing BV/TV with aging. Overall, we found no evidence that females had more pronounced age-related deterioration than males. We conclude that bones from aging female and male BALB/c mice exhibit many of the changes seen in humans, and are therefore a clinically relevant model for studies of skeletal aging.
bone structure; bone strength; bone mineralization; aging; mouse model
Long chain n-3 PUFA have been shown to have chemopreventive properties against breast cancer through various mechanisms. One pathway, studied in human breast cancer cell lines, involves upregulation of the proteoglycan, syndecan-1 (SDC-1) by n-3 PUFA-enriched LDL. Using Fat-1 mice that are able to convert n-6 to n-3 PUFA, we tested whether SDC-1 level in vivo is elevated in mammary glands due to endogenously synthesized rather than LDL-derived n-3 PUFA. Female Fat-1 and wild type (wt) mice were fed an n-6 PUFA- enriched diet for 7 weeks. Fatty acid analysis of plasma lipoproteins showed that total n-6 PUFA reflected dietary intake similarly in both genotypes (VLDL, 36.2±2.2 and 40.9±3.9; LDL, 49.0±3.3 and 48.1±2.0; HDL, 54.6±1.2 and 58.2±1.3, mean ± SEM percent of total fatty acids for Fat-1 and wt animals respectively). Lipoprotein percent n-3 PUFA was also similar between groups. However, phospholipids and triglycerides extracted from mammary and liver tissues demonstrated significantly higher n-3 PUFA and a corresponding decrease in the ratio n-6/n-3 PUFA in Fat-1 compared to wt mice. This was accompanied by higher SDC-1 in mammary glands and livers of Fat-1 mice, thus demonstrating that endogenously synthesized n-3 PUFA may upregulate SDC-1 in the presence of high dietary n-6 PUFA.
There is no effective treatment for prostate cancer arising after androgen ablation. Previous studies have analyzed the short-term effects of androgen ablation on the immune system and suggest an abatement of immune suppression by hormone removal. Since castration-resistant disease can arise years after treatment, it is crucial to determine the duration of immune potentiation by castration. Because immunotherapeutic efficacy is determined by the balance of immune cell subsets and their location within the tumor, we assessed the acute and chronic effect of androgen ablation on the localization of T cell subsets within castration-resistant murine prostate cancer. We observed a transient increase in CD4+ and CD8+ T cell numbers at the residual tumor after androgen ablation. More than two months later, regulatory T cells were increasingly within prostate epithelium, while cytolytic T cells (CTL), which were evenly distributed prior to androgen ablation, became sequestered within stroma. Anti-CD25 antibody administration along with castration enhanced CTL access to cancerous glands, but did not increase effector function. Intra-prostatic injection of LIGHT-expressing tumor cells increased the proportion of CD8+ T cells with functional capacity within the cancerous gland. In addition, Treg depletion within the tumor was enhanced. Together these manipulations significantly reduced castration-resistant tumor burden. Thus, our results indicate that immune modulations which prevent Treg accumulation and augment effector cell infiltration of prostatic epithelium may be effective in reducing tumor burden or preventing tumor recurrence after androgen ablation therapy.
castration; prostate cancer; T cells; regulatory T cell depletion; stroma; LIGHT; vaccination
Dmp1 (Dmtf1) encodes a Myb-like transcription factor implicated in tumor suppression through direct activation of the Arf-p53 pathway. The human DMP1 gene is frequently deleted in non-small cell lung cancers, especially those that retain wild-type INK4a/ARF and/or p53. To identify novel genes that are regulated by Dmp1, transcriptional profiles of lung tissue from Dmp1-null and wild-type mice were generated using the GeneChip Microarray. Comparative analysis of gene expression changes between the two groups resulted in identification of numerous genes that may be regulated by Dmp1. Notably, amphiregulin (Areg), thrombospondin-1 (Tsp-1), JunB, Egr1, adrenomedullin (Adm), Bcl-3 and methyl-CpG binding domain protein 1 (Mbd1) were downregulated in the lungs from Dmp1-null mice while Gas1 and Ect2 genes were upregulated. These target genes were chosen for further analyses since they are involved in cell proliferation, transcription, angiogenesis/metastasis, apoptosis, or DNA methylation, and thus could account for the tumor suppressor phenotype of Dmp1. Dmp1 directly bound to the genomic loci of Areg, Tsp-1, JunB and Egr1. Significant upregulation or downregulation of the novel Dmp1 target genes was observed upon transient expression of Dmp1 in alveolar epithelial cells, an effect which was nullified by the inhibition of de novo mRNA synthesis. Interestingly, these genes and their protein products were significantly downregulated or upregulated in the lungs from Dmp1-heterozygous mice as well. Identification of novel Dmp1 target genes not only provides insights into the effects of Dmp1 on global gene expression, but also sheds light on the mechanism of haploid insufficiency of Dmp1 in tumor suppression.
Dmp1; Dmtf1; GeneChip Microarray; Lung; Amphiregulin; Thrombospondin-1; JunB; Egr1; Ect2; Arf; haploid insufficiency
Deletions within the short arm of chromosome 7 are observed in approximately 25% of adult and 10% of Wilms pediatric renal tumors. Within Wilms tumors, the region of interest has been delineated to a 2-Mb minimal region that includes ten known genes. Two of these ten candidate genes, SOSTDC1 and MEOX2, are particularly relevant to tumor development and maintenance. This finding, coupled with evidence that SOSTDC1 is frequently downregulated in adult renal cancer and regulates both Wingless-Int (Wnt)- and bone morphogenetic protein (BMP)-induced signaling, points to a role for SOSTDC1 as a potential tumor suppressor.
To investigate this hypothesis, we interrogated the Oncomine database to examine the SOSTDC1 levels in adult renal clear cell tumors and pediatric Wilms tumors. We then performed single nucleotide polymorphism (SNP) and sequencing analyses of SOSTDC1 in 25 pediatric and 36 adult renal tumors. Immunohistochemical staining of patient samples was utilized to examine the impact of SOSTDC1 genetic aberrations on SOSTDC1 protein levels and signaling.
Within the Oncomine database, we found that SOSTDC1 levels were reduced in adult renal clear cell tumors and pediatric Wilms tumors. Through SNP and sequencing analyses of 25 Wilms tumors, we identified four with loss of heterozygosity (LOH) at 7p and three that affected SOSTDC1. Of 36 adult renal cancers, we found five with LOH at 7p, two of which affected SOSTDC1. Immunohistochemical analysis of SOSTDC1 protein levels within these tumors did not reveal a relationship between these instances of SOSTDC1 LOH and SOSTDC1 protein levels. Moreover, we could not discern any impact of these genetic alterations on Wnt signaling as measured by altered beta-catenin levels or localization.
This study shows that genetic aberrations near SOSTDC1 are not uncommon in renal cancer, and occur in adult as well as pediatric renal tumors. These observations of SOSTDC1 LOH, however, did not correspond with changes in SOSTDC1 protein levels or signaling regulation. Although our conclusions are limited by sample size, we suggest that an alternative mechanism such as epigenetic silencing of SOSTDC1 may be a key contributor to the reduced SOSTDC1 mRNA and protein levels observed in renal cancer.
Spontaneous regression/complete resistance (SR/CR) mice are a unique colony of mice that possess an inheritable, natural cancer resistance mediated primarily by innate cellular immunity. This resistance is effective against sarcoma 180 (S180) at exceptionally high doses and these mice remain healthy.
In this study, we challenged SR/CR mice with additional lethal transplantable mouse cancer cell lines to determine their resistance spectrum. The ability of these transplantable cancer cell lines to induce leukocyte infiltration was quantified and the percentage of different populations of responding immune cells was determined using flow cytometry.
In comparison to wild type (WT) mice, SR/CR mice showed significantly higher resistance to all cancer cell lines tested. However, SR/CR mice were more sensitive to MethA sarcoma (MethA), B16 melanoma (B16), LL/2 lung carcinoma (LL/2) and J774 lymphoma (J774) than to sarcoma 180 (S180) and EL-4 lymphoma (EL-4). Further mechanistic studies revealed that this lower resistance to MethA and LL/2 was due to the inability of these cancer cells to attract SR/CR leukocytes, leading to tumor cell escape from resistance mechanism. This escape mechanism was overcome by co-injection with S180, which could attract SR/CR leukocytes allowing the mice to resist higher doses of MethA and LL/2. S180-induced cell-free ascites fluid (CFAF) co-injection recapitulated the results obtained with live S180 cells, suggesting that this chemoattraction by cancer cells is mediated by diffusible molecules. We also tested for the first time whether SR/CR mice were able to resist additional cancer cell lines prior to S180 exposure. We found that SR/CR mice had an innate resistance against EL-4 and J774.
Our results suggest that the cancer resistance in SR/CR mice is based on at least two separate processes: leukocyte migration/infiltration to the site of cancer cells and recognition of common surface properties on cancer cells. The infiltration of SR/CR leukocytes was based on both the innate ability of leukocytes to respond to chemotactic signals produced by cancer cells and on whether cancer cells produced these chemotactic signals. We found that some cancer cells could escape from SR/CR resistance because they did not induce infiltration of SR/CR leukocytes. However, if infiltration of leukocytes was induced by co-injection with chemotactic factors, these same cancer cells could be effectively recognized and killed by SR/CR leukocytes.
Spontaneous Regression/Complete Resistant (SR/CR) mice are a colony of cancer-resistant mice that can detect and rapidly destroy malignant cells with innate cellular immunity, predominately mediated by granulocytes. Our previous studies suggest that several effector mechanisms, such as perforin, granzymes, or complements, may be involved in the killing of cancer cells. However, none of these effector mechanisms is known as critical for granulocytes. Additionally, it is unclear which effector mechanisms are required for the cancer killing activity of specific leukocyte populations and the survival of SR/CR mice against the challenges of lethal cancer cells. We hypothesized that if any of these effector mechanisms was required for the resistance to cancer cells, its functional knockout in SR/CR mice should render them sensitive to cancer challenges. This was tested by cross breeding SR/CR mice into the individual genetic knockout backgrounds of perforin (Prf-/-), superoxide (Cybb-/), or inducible nitric oxide (Nos2-/).
SR/CR mice were bred into individual Prf-/-, Cybb-/-, or Nos2-/- genetic backgrounds and then challenged with sarcoma 180 (S180). Their overall survival was compared to controls. The cancer killing efficiency of purified populations of macrophages and neutrophils from these immunodeficient mice was also examined.
When these genetically engineered mice were challenged with cancer cells, the knockout backgrounds of Prf-/-, Cybb-/-, or Nos2-/- did not completely abolish the SR/CR cancer resistant phenotype. However, the Nos2-/- background did appear to weaken the resistance. Incidentally, it was also observed that the male mice in these immunocompromised backgrounds tended to be less cancer-resistant than SR/CR controls.
Despite the previously known roles of perforin, superoxide or nitric oxide in the effector mechanisms of innate immune responses, these effector mechanisms were not required for cancer-resistance in SR/CR mice. The resistance was functional when any one of these effector mechanisms was completely absent, except some noticeably reduced penetrance, but not abolishment, of the phenotype in the male background in comparison to female background. These results also indicate that some other effector mechanism(s) of granulocytes may be involved in the killing of cancer cells in SR/CR mice.
Spontaneous Regression/Complete Resistant (SR/CR) mice are resistant to cancer through a mechanism that is mediated entirely by leukocytes of innate immunity. Transfer of leukocytes from SR/CR mice can confer cancer resistance in wild-type (WT) recipients in both preventative and therapeutic settings. In the current studies, we investigated factors that may impact the efficacy and functionality of SR/CR donor leukocytes in recipients.
In sex-mismatched transfers, functionality of female donor leukocytes was not affected in male recipients. In contrast, male donor leukocytes were greatly affected in the female recipients. In MHC-mismatches, recipients of different MHC backgrounds, or mice of different strains, showed a greater negative impact on donor leukocytes than sex-mismatches. The negative effects of sex-mismatch and MHC-mismatch on donor leukocytes were additive. Old donor leukocytes performed worse than young donor leukocytes in all settings including in young recipients. Young recipients were not able to revive the declining function of old donor leukocytes. However, the function of young donor leukocytes declined gradually in old recipients, suggesting that an aged environment may contain factors that are deleterious to cellular functions. The irradiation of donor leukocytes prior to transfers had a profound suppressive effect on donor leukocyte functions, possibly as a result of impaired transcription. The cryopreserving of donor leukocytes in liquid nitrogen had no apparent effect on donor leukocyte functions, except for a small loss of cell number after revival from freezing.
Despite the functional suppression of donor leukocytes in sex- and MHC-mismatched recipients, as well as old recipients, there was a therapeutic time period during the initial few weeks during which donor leukocytes were functional before their eventual rejection or functional decline. The eventual rejection of donor leukocytes will likely prevent donor leukocyte engraftment which would help minimize the risk of transfusion-associated graft-versus-host disease. Therefore, using leukocytes from healthy donors with high anti-cancer activity may be a feasible therapeutic concept for treating malignant diseases.
NGEP (New Gene Expressed in Prostate) is a prostate specific polytopic membrane protein found at high concentrations at cell:cell contact regions. To determine if NGEP is a useful target for antibody based therapy of prostate cancer we performed an immunohistochemical analysis of 126 human prostate carcinoma samples using a polyclonal anti-NGEP sera and found that 91% of the cancers express NGEP protein. To elucidate the topology of NGEP and guide the development of monoclonal antibodies (MAb) reacting with the extracellular regions of NGEP, an HA epitope tag was inserted at several positions within the NGEP sequence. The tagged proteins were expressed in 293T cells and locations of the tags were determined by immunofluorescence in intact or permeabilized cells. The results indicate that NGEP contains 8 transmembrane ™ domains with both the N-and C-termini of NGEP located inside the cell. We produced MAb to three regions that are predicted to be intracellular based on the epitope tag data (a.a. 1–352, 441–501 and 868–933) and as predicted the MAb only detected the protein in permeabilized cells. NGEP is a glycoprotein with predicted glycosylation sites at N809 and N824. When these residues were converted to glutamine, glycosylation was abolished confirming the residues are extracellular. Our findings on the expression and the orientation of the NGEP protein serve as an important framework for the development of MAb targeting the extracellular regions of NGEP that could be used for prostate cancer immunotherapy.
prostate cancer; immunotherapy; plasma membrane protein; TMEM16E; N-glycosylation
Cytosolic phospholipase A2 (cPLA2)α responds to the rise in cytosolic Ca2+ ([Ca2+]i) attending cell stimulation by moving to intracellular membranes, releasing arachidonic acid (AA) from these membranes, and thereby initiating the synthesis of various lipid mediators. Under some conditions, however, cPLA2α translocation occurs without any corresponding changes in [Ca2+]i. The signal for such responses has not been identified. Using confocal microscopy to track fluorescent proteins fused to cPLA2α or cPLA2α’s C2 domain, we find that AA mimics Ca2+ ionophores in stimulating cPLA2α translocations to the perinuclear ER and to a novel site, the lipid body. Unlike the ionophores, AA acted independently of [Ca2+]i rises and did not translocate the proteins to the Golgi. AA’s action did not involve its metabolism to eicosanoids or acylation into cellular lipids. Receptor agonists also stimulated translocations targeting lipid bodies. We propose that AA is a signal for Ca2+-independent cPLA2α translocation and that lipid bodies are common targets of cPLA2α and contributors to stimulus-induced lipid mediator synthesis.
cPLA2α; C2 Domain; Translocation; Arachidonic Acid; Lipid Bodies; Cellular Calcium; Cancer Cells
BAD, a pro-apoptotic protein of the Bcl-2 family, has recently been identified as an integrator of several anti-apoptotic signaling pathways in prostate cancer cells. Thus, activation of EGFR, GPCRs or PI3K pathway leads to BAD phosphorylation and inhibition of apoptosis. Increased levels of BAD in prostate carcinomas have also been reported. It appears contradictory that instead of limiting expression of pro-apoptotic protein, prostate cancer cells choose to increase BAD levels while keeping it under tight phosphorylation control. Analysis of the effect of BAD on prostate cancer xenografts has shown that increased BAD expression enhances tumor growth, while knockdown of BAD expression by shRNA inhibits tumor growth. Tissue culture experiments demonstrated that increased BAD expression stimulates proliferation of prostate cancer cells. These results suggest that increased expression of BAD provides a proliferative advantage to prostate tumors, while BAD dephosphorylation increases sensitivity of prostate cancer cells to apoptosis. Combination of proliferative and apoptotic properties prompts prostate cancer cells to be “addicted” to increased levels of phosphorylated BAD. Thus, kinases that phosphorylate BAD are plausible therapeutic targets; while monitoring BAD phosphorylation could be used to predict tumor response to treatments.
We previously created a knock-in mutant mouse harboring a dominantly negative mutant thyroid hormone receptor β (TRβPV/PV mouse) that spontaneously develops a follicular thyroid carcinoma similar to human thyroid cancer. We found that β-catenin, which plays a critical role in oncogenesis, was highly elevated in thyroid tumors of TRβPV/PV mice. We sought to understand the molecular basis underlying aberrant accumulation of β-catenin by mutations of TRβ in vivo. Cell-based studies showed that thyroid hormone (T3) induced the degradation of β-catenin in cells expressing TRβ via proteasomal pathways. In contrast, no T3-induced degradation occurred in cells expressing the mutant receptor (TRβPV). In vitro binding studies and cell-based analyses revealed that β-catenin physically associated with unliganded TRβ or TRβPV. However, in the presence of T3, β-catenin was dissociated from TRβ-β-catenin complexes but not from TRβPV-β-catenin complexes. β-Catenin signaling was repressed by T3 in TRβ-expressing cells through decreasing β-catenin-mediated transcription activity and target gene expression, whereas sustained β-catenin signaling was observed in TRβPV-expressing cells. The stabilization of β-catenin, via association with a mutated TRβ, represents a novel activating mechanism of the oncogenic protein β-catenin that could contribute to thyroid carcinogenesis in TRβPV/PV mice.