Stromal Gas6 promotes the progression of premalignant mammary cells

Tumor progression is regulated by a complex interplay between neoplastic cells and the tumor microenvironment. Tumor associated macrophages have been shown to promote breast cancer progression in advanced disease and more recently, in early stage cancers. However, little is known about the macrophage-derived factors that promote tumor progression in early stage lesions. Using a p53-null model of early stage mammary tumor progression, we found that Gas6 is highly expressed in pre-invasive lesions associated with increased infiltrating macrophages, as compared to those with few recruited macrophages. We show that F4/80⁺CD11b⁺ macrophages produce Gas6 in premalignant lesions in vivo, and that macrophage-derived Gas6 induces a tumor-like phenotype ex vivo. Using a 3-D co-culture system, we show that macrophage-derived Gas6 activates its receptor Axl and downstream survival signals including Akt and STAT3, which was accompanied by altered E-cadherin expression to induce a malignant morphology. In vivo studies demonstrated that deletion of stromal Gas6 delays early stage progression and decreases tumor formation, while tumor growth in established tumors remains unaffected. These studies suggest that macrophage-derived Gas6 is a critical regulator of the transition from premalignant to invasive cancer, and may lead to the development of unique biomarkers of neoplastic progression for patients with early stage breast cancer, including ductal carcinoma in situ.

Whole Mammary Gland Transplantation in Mice Protocol

Whole Mammary Gland Transplantation involves transplanting an excised mammary gland into another, more suitable host. This method can be used to extend the life of a mammary gland past the mouse's life span by transplanting the mammary gland of an older mouse into a young healthy mouse. As you can see in the video below (Video 1), by attaching it to the abdomen of the mouse, the gland will receive a steady blood supply and both epithelial and stromal cells will remain viable for up to one year. Although this method is not used often, it has been part of several experiments including determining whether the stroma or epithelium is the primary target in chemically induced mouse mammary tumorigenesis (Medina and Kittrell, 2005). To monitor transplants, palpate every week for tumor formation. The transplanted mammary gland may also be passaged serially every 8-10 weeks. Keep transplanted gland in the same mouse for no longer than one year.

Pituitary Isograft Transplantation in Mice

The mouse pituitary isograft is a technique developed to administer persistent hormone stimulation, thereby increasing cellular proliferation in the mammary tissue ( Christov et al., 1993 ). The pituitary isograft procedure was first described in 'Induction of Mammary Cancer in Mice without the Mammary Tumor Agent by Isografts of Hypophyses' by O. Mühlbock and L. M. Boot in 1959 (Muhlbock and Boot, 1959). Since then, the procedure has seen wide use. A pituitary gland is harvested posthumously from a donor mouse and implanted under the renal capsule of the recipient mouse through a small abdominal incision just below the last rib. Once the pituitary gland is implanted, it begins releasing hormones. These secretions increase serum levels of multiple hormones including prolactin, progesterone and 17β-estradiol ( Christov et al., 1993 ). Although the effects of these hormones on cancer cell proliferation, growth, differentiation, and longevity are not well characterized, and, in some cases, controversial, the net effect of a pituitary isograft is to increase the proliferation of murine breast tissue depending upon strain specific characteristics ( Lydon et al., 1999 ). Below is a protocol describing how to perform the pituitary isograft procedure. After many of the steps, a time reference is listed in parentheses. Each reference corresponds to a time point in the embedded video of the procedure. (Video 1) Video 1.Pituitary isograft transplantation in mice. Video portraying pituitary isograft transplantation procedure in donor and recipient mice.

Macrophages promote the progression of premalignant mammary lesions to invasive cancer

Breast cancer initiation, progression and metastasis rely on a complex interplay between tumor cells and their surrounding microenvironment. Infiltrating immune cells, including macrophages, promote mammary tumor progression and metastasis; however, less is known about the role of macrophages in early stage lesions. In this study, we utilized a transplantable p53-null model of early progression to characterize the immune cell components of early stage lesions. We show that macrophages are recruited to ductal hyperplasias with a high tumor-forming potential where they are differentiated and polarized toward a tumor-promoting phenotype. These macrophages are a unique subset of macrophages, characterized by pro-inflammatory, anti-inflammatory and immunosuppressive factors. Macrophage ablation studies showed that macrophages are required for both early stage progression and primary tumor formation. These studies suggest that therapeutic targeting of tumor-promoting macrophages may not only be an effective strategy to block tumor progression and metastasis, but may also have critical implications for breast cancer prevention.

Mouse Mammary Intraductal (MIND) Method for Transplantation of Patient Derived Primary DCIS Cells and Cell Lines

The MIND method involves intraductal injection of patient derived ductal carcinoma in situ (DCIS) cells and DCIS cell lines (MCF10DCIS.COM and SUM225) inside the mouse mammary ducts [Video 1 and Figure 1 in Behbod et al. (2009)]. This method mimics the normal environment of DCIS and facilitates study of the natural progression of human DCIS, i.e., their initial growth as carcinoma in situ within the ducts, followed by invasion into the stroma through the myoepithelial cell layer and basement membrane (Behbod et al., 2009; Valdez et al., 2011). In order to demonstrate that transplantation procedure is successful, the transplanted mammary glands may be excised as early as two weeks following intraductal injection of cells followed by Hematoxylin and Eosin (H&E) staining and/or immunofluorescence staining using human specific cytokeratin 5 and/or 19 [please see Figures 2-4 in Behbod et al. (2009)]. Additionally, the presence of trypan blue inside the mouse mammary ducts immediately following intraductal injection is the best indicator that the injection was successful (Video 1 starting at 4:33 sec).

Intra-mammary ductal transplantation: a tool to study premalignant progression

Ductal carcinoma in situ (DCIS) is a non-obligate precursor to invasive breast cancer. Although there is extensive information on the cellular and molecular changes in DCIS, there is limited ability to functionally test. The critical changes in premalignant progression. This review summarizes our experience with a recently developed method which provides. The opportunity to functionally test the molecular events occuring to functionally test the molecular events occurring in the initial changes in premaligant progression; i.e., the step from non-invasive to invasive behavior.

Prevention of tumorigenesis in p53-null mammary epithelium by rexinoid bexarotene, tyrosine kinase inhibitor gefitinib, and celecoxib

The chemopreventive effects of three agents, rexinoid bexarotene, tyrosine kinase inhibitor gefitinib, and celecoxib, were tested on mammary tumor development arising in p53-null mammary epithelium. The rexinoid bexarotene was the most efficacious inhibitor as it reduced mammary tumor development by 75% in virgin mice and significantly delayed mean tumor development by 98 days in hormone-stimulated mice. The tyrosine kinase inhibitor gefitinib reduced mammary tumor incidence by 50% in virgin mice but did not significantly delay mean tumor latency in hormone-stimulated mice. Celecoxib did not reduce tumor incidence or mean tumor latency in either of the two models. The high doses of the rexinoid and the tyrosine kinase inhibitor did not affect the progression of tumors arising from the premalignant mammary outgrowth line, PN8a. A comparison of these agents with tamoxifen shows the superiority of tamoxifen in preventing tumor development in p53-null mammary cells. Similarly, a comparison of the results of the p53 model with other transgenic models in their response to the chemopreventive agents showed that mammary tumors arising from different oncogenic events will respond differently to the different agents.

Identification of tumor-initiating cells in a p53-null mouse model of breast cancer

Using a syngeneic p53-null mouse mammary gland tumor model that closely mimics human breast cancer, we have identified, by limiting dilution transplantation and in vitro mammosphere assay, a Lin(-)CD29(H)CD24(H) subpopulation of tumor-initiating cells. Upon subsequent transplantation, this subpopulation generated heterogeneous tumors that displayed properties similar to the primary tumor. Analysis of biomarkers suggests the Lin(-)CD29(H)CD24(H) subpopulation may have arisen from a bipotent mammary progenitor. Differentially expressed genes in the Lin(-)CD29(H)CD24(H) mouse mammary gland tumor-initiating cell population include those involved in DNA damage response and repair, as well as genes involved in epigenetic regulation previously shown to be critical for stem cell self-renewal. These studies provide in vitro and in vivo data that support the cancer stem cell (CSC) hypothesis. Furthermore, this p53-null mouse mammary tumor model may allow us to identify new CSC markers and to test the functional importance of these markers.

Identification of tumor-initiating cells in a p53-null mouse model of breast cancer

Using a syngeneic p53-null mouse mammary gland tumor model that closely mimics human breast cancer, we have identified, by limiting dilution transplantation and in vitro mammosphere assay, a Lin(-)CD29(H)CD24(H) subpopulation of tumor-initiating cells. Upon subsequent transplantation, this subpopulation generated heterogeneous tumors that displayed properties similar to the primary tumor. Analysis of biomarkers suggests the Lin(-)CD29(H)CD24(H) subpopulation may have arisen from a bipotent mammary progenitor. Differentially expressed genes in the Lin(-)CD29(H)CD24(H) mouse mammary gland tumor-initiating cell population include those involved in DNA damage response and repair, as well as genes involved in epigenetic regulation previously shown to be critical for stem cell self-renewal. These studies provide in vitro and in vivo data that support the cancer stem cell (CSC) hypothesis. Furthermore, this p53-null mouse mammary tumor model may allow us to identify new CSC markers and to test the functional importance of these markers.

Altered mammary gland development in the p53+/m mouse, a model of accelerated aging

The tumor suppressor p53 is important for inhibiting the development of breast carcinomas. However, little is known about the effects of increased p53 activity on mammary gland development. Therefore, the effect of p53 dosage on mammary gland development was examined by utilizing the p53+/m mouse, a p53 mutant which exhibits increased wild-type p53 activity, increased tumor resistance, a shortened longevity, and a variety of accelerated aging phenotypes. Here we report that p53+/m virgin mice exhibit a defect in mammary gland ductal morphogenesis. Transplants of mammary epithelium into p53+/m recipient mice demonstrate decreased outgrowth of wild-type and p53+/m donor epithelium, suggesting systemic or stromal alterations in the p53+/m mouse. Supporting these data, p53+/m mice display decreased levels of serum IGF-1 and reduced IGF-1 signaling in virgin glands. The induction of pregnancy or treatment of p53+/m mice with estrogen, progesterone, estrogen and progesterone in combination, or IGF-1 stimulates ductal outgrowth, rescuing the p53+/m mammary phenotype. Serial mammary epithelium transplants demonstrate that p53+/m epithelium exhibits decreased transplant capabilities, suggesting early stem cell exhaustion. These data indicate that appropriate levels of p53 activity are important in regulating mammary gland ductal morphogenesis, in part through regulation of the IGF-1 pathway.

p19ARF determines the balance between normal cell proliferation rate and apoptosis during mammary gland development

This study demonstrated, for the first time, the following events related to p19(ARF) involvement in mammary gland development: 1) Progesterone appears to regulate p19(ARF) in normal mammary gland during pregnancy. 2) p19(ARF) expression levels increased sixfold during pregnancy, and the protein level plateaus during lactation. 3) During involution, p19(ARF) protein level remained at high levels at 2 and 8 days of involution and then, declined sharply at day 15. Absence of p19(ARF) in mammary epithelial cells leads to two major changes, 1) a delay in the early phase of involution concomitant with downregulation of p21(Cip1) and decrease in apoptosis, and 2) p19(ARF) null cells are immortal in vivo measured by serial transplantion, which is partly attributed to complete absence of p21(Cip1) compared with WT cells. Although, p19(ARF) is dispensable in mammary alveologenesis, as evidenced by normal differentiation in the mammary gland of pregnant p19(ARF) null mice, the upregulation of p19(ARF) by progesterone in the WT cells and the weakness of p21(Cip1) in mammary epithelial cells lacking p19(ARF) strongly suggest that the functional role(s) of p19(ARF) in mammary gland development is critical to sustain normal cell proliferation rate during pregnancy and normal apoptosis in involution possibly through the p53-dependent pathway.

Stroma is not a major target in DMBA-mediated tumorigenesis of mouse mammary preneoplasia

Carcinogenesis in the mammary gland is thought to involve carcinogen-induced initiation in mammary epithelial cells. Recent experiments have demonstrated that the mammary stroma can be a target of carcinogenic agents, which results in the stroma positively affecting carcinogenesis. To determine whether the stroma or epithelium is the primary target in chemically induced mouse mammary tumorigenesis, we used transplantation of untreated or 7,12-dimethylbenzanthracene (DMBA)-treated immortalized preneoplastic mammary cells into untreated or DMBA-treated stroma. The results demonstrate that the chemical-carcinogen treated stroma did not enhance mammary tumorigenesis in this model and that carcinogen treatment of the mammary epithelium was essential for tumorigenesis.

From mice to humans: identification of commonly deregulated genes in mammary cancer via comparative SAGE studies

Genetically engineered mouse mammary cancer models have been used over the years as systems to study human breast cancer. However, much controversy exists on the utility of such models as valid equivalents to the human cancer condition. To perform an interspecies gene expression comparative study in breast cancer we used a mouse model that most closely resembles human breast carcinogenesis. This system relies on the transplant of p53 null mouse mammary epithelial cells into the cleared mammary fat pads of syngeneic hosts. Serial analysis of gene expression (SAGE) was used to obtain gene expression profiles of normal and tumor samples from this mouse mammary cancer model (>300,000 mouse mammary-specific tags). The resulting mouse data were compared with 25 of our human breast cancer SAGE libraries (>2.5 million human breast-specific tags). We observed significant similarities in the deregulation of specific genes and gene families when comparing mouse with human breast cancer SAGE data. A total of 72 transcripts were identified as commonly deregulated in both species. We observed a systematic and significant down-regulation in all of the tumors from both species of various cytokines, including CXCL1 (GRO1), LIF, interleukin 6, and CCL2. All of the mouse and most human mammary tumors also displayed decreased expression of genes known to inhibit cell proliferation, including NFKBIA (IKBalpha), GADD45B, and CDKN1A (p21); transcription-related genes such as CEBP, JUN, JUNB, and ELF1; and apoptosis-related transcripts such as IER3 and GADD34/PPP1R15A. Examples of overexpressed transcripts in tumors from both species include proliferation-related genes such as CCND1, CKS1B, and STMN1 (oncoprotein 18); and genes related to other functions such as SEPW1, SDFR1, DNCI2, and SP110. Importantly, abnormal expression of several of these genes has not been associated previously with breast cancer. The consistency of these observations was validated in independent mouse and human mammary cancer sets. This is the first interspecies comparison of mammary cancer gene expression profiles. The comparative analysis of mouse and human SAGE mammary cancer data validates this p53 null mouse tumor model as a useful system closely resembling human breast cancer development and progression. More importantly, these studies are allowing us to identify relevant biomarkers of potential use in human studies while leading to a better understanding of specific mechanisms of human breast carcinogenesis.

Modeling human breast cancer metastasis in mice: maspin as a paradigm

Breast cancer is the most common cancer detected in women, accounting for nearly one out of every three cancers diagnosed in the United States. Most cancer patients do not die from the primary tumor but die due to metastasis. Therefore, the study of metastasis is of most importance both to the clinician and patient. In the past, animal models have been used in breast cancer research and mammary gland biology. Our group has also established several animal models to address the function of a novel tumor suppressor gene maspin in breast tumor progression. Maspin was initially isolated from normal mammary epithelial cells. Its expression was down regulated in breast tumors. To test the protective role of maspin overexpression in mammary tumor progression, we crossed maspin overexpression transgenic mice (WAP-maspin) with a strain of oncogenic WAP-SV40 T antigen mice. The bitransgenic mice had reduced tumor growth rate and metastasis. Maspin overexpression increased the rate of apoptosis of both preneoplastic and carcinomatous mammary epithelial cells. Maspin reduced tumor growth through a combination of reduced angiogenesis and increased apoptosis. In a separate animal experiment, maspin overexpressing mammary tumor cells (TM40D) were implanted into the fat pad of syngeneic mice. TM40D tumor cells were very invasive and metastatic. However, both primary tumor growth and metastasis were significantly blocked in TM40D cells that overexpress maspin as a consequence of plasmid or retrovirus infection. These evidences demonstrate that maspin function to inhibit primary tumor growth as well as invasion and metastasis. Elucidating the molecular mechanism of maspin action will shed light on our understanding of breast cancer invasion and metastasis.

Functional analysis of cyclin D2 and p27(Kip1) in cyclin D2 transgenic mouse mammary gland during development

Two mammary gland phenotypes were detected in pregnant MMTV-cyclin D2 transgenic mice; line D2-53 exhibited a lack of alveologenesis and failure to nurse, whereas line D2-58 featured a reduction in alveologenesis, but retained normal nursing behavior. In pregnant mammary glands, cyclin D2 protein levels were twofold (P<0.107) and 3.8-fold (P<0.0076) higher in line D2-58 and D2-53, respectively, compared to wild type. Concomitantly with the increase in cyclin D2 was a fivefold decrease in cyclin D1 hyper-phosphorylated isoform in mammary glands of pregnant cyclin D2-58 mice. Because cyclin D1 is a critical molecule in normal mammary lobuloalveolar development, these data suggest that overexpression of cyclin D2 may block mammary lobuloalveolar development through inhibition of cyclin D1 phosphorylation. During mammary gland development, p27(kip1) protein level oscillated in a similar profile in wild type and cyclin D2 transgenic mice, but was consistently higher in the cyclin D2 mice suggesting that p27(kip1) functions downstream of cyclin D2. The ratio of p27(kip1)-cdk4/p27(kip1)-cdk2 was 6.5-fold (P<0.0003) higher in cyclin D2 mammary glands compared to wild type in pregnant animals. This ratio reversed to 2.2-fold (P<0.005) higher in wild type compared to cyclin D2 mammary glands in involution suggesting that overexpression of cyclin D2 moderately induced apoptosis during pregnancy but accelerated involution. Collectively, the effects of cyclin D2 overexpression on mammary gland development during pregnancy and involution are attributed to two major factors, altered p27(kip1) protein level and inhibition of cyclin D1 phosphorylation.

Serial analysis of gene expression in normal p53 null mammary epithelium

Much evidence has accumulated implicating the p53 gene as of importance in breast carcinogenesis. However, much still remains to be uncovered on the specific downstream pathways influenced by this important activator/repressor of transcription. This study investigated the effects of a p53 null genotype on the transcriptome of 'normal' mouse mammary epithelium using a unique in vivo model of preneoplastic transformation. We used SAGE for the comparative analysis of p53 wild type (wt) and null mammary epithelium unexposed and exposed to hormonal stimulation. Analysis of the hormone exposed samples provided a comprehensive view of the dramatic changes in gene expression as consequence of the functional differentiation of the mammary epithelium in an in vivo system. We detected the dysregulation in p53(null) epithelium of <1% of the transcriptome. Changes in expression affected not only known p53 target genes, but also several unexpected genes such as Expi (Wdnm1), Cyp1b1, Gelsolin, Ramp2 and class I MHC genes. The dysregulation of specific genes and their potential use as preneoplastic markers was further validated using an independent model of premalignant mammary outgrowth lines. This is the first study to examine the transcriptome of very early stages of preneoplastic progression in an in vivo model that mimics human breast cancer.

Nuclear factor-kappaB (NF-kappaB) regulates proliferation and branching in mouse mammary epithelium

The nuclear factor-kappaB (NF-kappaB) family of transcription factors has been shown to regulate proliferation in several cell types. Although recent studies have demonstrated aberrant expression or activity of NF-kappaB in human breast cancer cell lines and tumors, little is known regarding the precise role of NF-kappaB in normal proliferation and development of the mammary epithelium. We investigated the function of NF-kappaB during murine early postnatal mammary gland development by observing the consequences of increased NF-kappaB activity in mouse mammary epithelium lacking the gene encoding IkappaBalpha, a major inhibitor of NF-kappaB. Mammary tissue containing epithelium from inhibitor kappaBalpha (IkappaBalpha)-deficient female donors was transplanted into the gland-free mammary stroma of wild-type mice, resulting in an increase in lateral ductal branching and pervasive intraductal hyperplasia. A two- to threefold increase in epithelial cell number was observed in IkappaBalpha-deficient epithelium compared with controls. Epithelial cell proliferation was strikingly increased in IkappaBalpha-deficient epithelium, and no alteration in apoptosis was detected. The extracellular matrix adjacent to IkappaBalpha-deficient epithelium was reduced. Consistent with in vivo data, a fourfold increase in epithelial branching was also observed in purified IkappaBalpha-deficient primary epithelial cells in three-dimensional culture. These data demonstrate that NF-kappaB positively regulates mammary epithelial proliferation, branching, and functions in maintenance of normal epithelial architecture during early postnatal development.

Expression of Brca1 and splice variant Brca1delta11 RNA levels in mouse mammary gland during normal development and tumorigenesis

Expression of Brca1 in mouse mammary cancer has yet to be analysed. We use a progressive model of neoplasia based on several mouse epithelial cell lines that represent distinct steps toward the fully tumorigenic state. Using RNase protection analysis because acceptable anti-Brca1 antibodies are not available we investigated the expression of Brca1 and a splice variant, Brca1Delta11, in several mammary hyperplasias and tumors that arose from them, and in normal mammary gland through pregnancy and involution. Expression of Brca1 was highest in rapidly proliferating cells. Expression of the full-length Brca1 was detectable in the virgin gland, was slightly elevated in the midpregnant gland, and decreased to levels similar to the age-matched virgin gland in the completely involuted gland. Expression of both forms of Brca1 was detectable in 9/9 paired hyperplasias and tumors, with levels of total Brca1, but not the splice variant Brca1Delta11, in tumors higher than those in the hyperplasias. While in disagreement with the observation that Brca1 levels decrease in human breast cancer progression, these patterns support the notion that Brca1 expression is associated with proliferating cells, and suggests that the link with differentiation seen in normal cells can be removed when cells become tumorigenic.

Stage-specific changes in SR splicing factors and alternative splicing in mammary tumorigenesis

Using a mouse model of mammary gland development and tumorigenesis we examined changes in both alternative splicing and splicing factors in multiple stages of mammary cancer. The emphasis was on the SR family of splicing factors known to influence alternative splicing in a wide variety of genes, and on alternative splicing of the pre-mRNA encoding CD44, for which alternative splicing has been implicated as important in a number of human cancers, including breast cancer. We observed step-wise increases in expression of individual SR proteins and alternative splicing of CD44 mRNA during mammary gland tumorigenesis. Individual preneoplasias differed as to their expression patterns for SR proteins, often expressing only a sub-set of the family. In contrast, tumors demonstrated a complex pattern of SR expression. Little difference was observed between neoplasias and their metastases. Alternative splicing of CD44 also changed through the disease paradigm such that tumors produced RNA containing a mixture of variable exons, whereas preneoplasias exhibited a more restricted exon inclusion pattern. In contrast, other standard splicing factors changed little in either concentration or splicing pattern in the same cells. These data suggest alterations in relative concentrations of specific splicing factors during early preneoplasia that become more pronounced during tumor formation. Given the ability of SR proteins to affect alternative processing decisions, our results suggest that a number of pre-mRNAs may undergo changes in alternative splicing during the early and intermediate stages of mammary cancer.

A transgenic mouse model for mammary carcinogenesis

Missense mutations in the p53 tumor suppressor occur frequently in human breast cancer and influence both the prognosis and response to chemotherapy. Amino acid 175 (equivalent to murine 172) is the second most common site of missense mutations in p53 in human breast cancer. Over 95% of these mutations are arginine-to-histidine (R-H) substitutions resulting in a gain-of-function, and not merely a dominant-negative phenotype. Transgenic mice expressing a p53 172(R-H) construct targeted to the mammary gland by means of a whey acidic protein (WAP) promoter were characterized as a model system in order to determine the specific effects of this mutation on mammary tumorigenesis. Although transgene expression alone had no apparent effect on normal mammary development, transgenic mice treated with the chemical carcinogen dimethylbenz(a)anthracene developed tumors with much shorter latency than did control littermates and had a greater tumor burden. Tumors arising in transgenic mice did not exhibit either decreased apoptosis or increased cell proliferation relative to tumors arising in nontransgenic littermates, but did display increased genomic instability. Large pleiomorphic nuclei were visible in many tumors from transgenic mice, and DNA flow analysis confirmed the presence of significant aneuploid cell populations. Since these transgenic mice develop very few spontaneous tumors, while accelerating carcinogen-and oncogene-mediated tumorigenesis, this mouse model will, therefore, be useful in the investigation of early events in mammary tumorigenesis. It may also be used as a preclinical model to test newly developed chemotherapeutic strategies.

Combination therapy with a nuclear type-ii site agonist and 5-Fluorouracil - inhibition of mammary-tumor growth

Methyl p-hydroxyphenyllactate (MeHPLA) is an endogenous ligand for nuclear type II sites which apparently regulates cellular growth and proliferation through this binding interaction. Occupancy of type II sites by MeHPLA agonists such as dihydroxybenzylidene acetophenone (DHBA), 2,6-bis ([3,4-dihydroxyphenyl]-methylene) cyclohexanone (BDHPC) and 2,6-bis ([3-methoxy-4-hydroxyphenyl]-methylene)cyclohexanone (BMHPC) is directly correlated with the inhibition of malignant cell proliferation. Most importantly, these compounds inhibit mammary tumor growth in vivo with minimal non-specific cytotoxicity. Therefore, combination therapy with MeHPLA agonists plus standard anti-neoplastic agents such as 5-Fluorouracil (FU) may result in tumor growth inhibition with minimal non-specific cytotoxicity. The results of these studies demonstrated that low doses of BMHPC (2 mug/mL) and FU (0.2 mug/mL) failed to significantly affect MCF-7 human breast cancer cell proliferation. However, combination therapy with these sub-inhibitory doses of BMHPC plus FU resulted in significant inhibition of cell proliferation in vitro, suggesting that BMHPC acts in an additive or synergistic fashion with FU to inhibit MCF-7 cell proliferation. Similarly, when orally administered to mice at a dose level of 50 mug/mL drinking water, neither BMHPC or FU alone substantially inhibited the growth of estrogen-independent transplantable mammary tumors. However, combination therapy with BMHPC plus FU antagonized tumor growth and no significant treatment effects were observed on fluid consumption or the body weights of these animals. These results demonstrate that MeHPLA agonists such as BMHPC are capable of acting additively or synergistically with FU to maintain therapeutic response with reduced non-specific systemic toxicity.

Distribution of selenium-binding proteins in different tissues of the mouse and rat

The distribution of selenium-binding proteins in specific tissues of mice and rats was examined by electrophoretic and immunologic techniques. Major selenium-binding proteins of 58K and 26K daltons were present in whole blood, erythrocytes, liver, duodenum, mammary tumors, kidney, testis, ovary and pancreas by electrophoretic analysis. By Western immunoblot it was evident that the 58K protein in plasma did not cross-react with the cellular 58 K protein. Furthermore, muscle did not exhibit any immunologically recognizable 58K protein. The antibody raised against mouse liver 58K recognized a similar protein in rat liver, kidney and testis. The 58K selenium-binding protein appeared to be concentrated in tissues enriched in G1 and the effect of hydroxyurea on selenium-binding protein levels suggested the 58K selenium-binding protein appeared to be made predominantly during the G1 phase of the cell cycle. Evidence is also presented that whole blood contains selenium bound to hemoglobin which supports prior evidence by other investigators. These results further support the evidence for tissue selenium-binding proteins other than glutathione peroxidase and document the immunological specificity and reactivity of a new antibody against a selenium-binding protein.