Inflammatory Breast Cancer: The Immune Perspective

Inflammatory breast cancer (IBC) is the most insidious form of locally advanced disease. Although rare and less than 2% of all breast cancer, IBC is responsible for up to 10% of all breast cancer deaths. Despite the name, very little is known about the role of inflammation or immune mediators in IBC. Therefore, we analyzed blood samples from IBC patients and non-IBC patients, as well as healthy donor controls to establish an IBC-specific profile of peripheral blood leukocyte phenotype and function of T cells and dendritic cells and serum inflammatory cytokines. Emerging evidence suggests that host factors in the microenviromement may interact with underlying IBC genetics to promote the aggressive nature of the tumor. An integral part of the metastatic process involves epithelial to mesenchymal transition (EMT) where primary breast cancer cells gain motility and stem cell-like features that allow distant seeding. Interestingly, the IBC consortium microarray data found no clear evidence for EMT in IBC tumor tissues. It is becoming increasingly evident that inflammatory factors can induce EMT. However, it is unknown if EMT-inducing soluble factors secreted by activated immune cells in the IBC microenvironment canπ account for the absence of EMT in studies of the tumor cells themselves. We hypothesized that soluble factors from immune cells are capable of inducing EMT in IBC. We tested the ability of immune conditioned media to induce EMT in IBC cells. We found that soluble factors from activated immune cells are able to induce the expression of EMT-related factors in IBC cells along with increased migration and invasion. Specifically, the pro-inflammatory cytokines TNF-α, IL-6 and TGF-β were able to induce EMT and blocking these factors in conditioned media abated the induction of EMT. Surprisingly, unique to IBC cells, this process was related to increased levels of E-cadherin expression and adhesion, reminiscent of the characteristic tightly packed tumor emboli seen in IBC samples. This data offers insight into the unique pathology of IBC by suggesting that tumor immune interactions in the tumor microenvironment contribute to the aggressive nature of IBC implying that immune induced inflammation can be a novel therapeutic target. Specifically, we showed that soluble factors secreted by activated immune cells are capable of inducing EMT in IBC cells and may mediate the persistent E-cadherin expression observed in IBC. This data suggests that immune mediated inflammation may contribute to the highly aggressive nature of IBC and represents a potential therapeutic target that warrants further investigation.

The Role of Type I Insulin-Like Growth Factor Receptor Signaling in Breast Cancer Brain Metastasis

Brain metastasis is a common cause of mortality in cancer patients. Approximately 20-30% of breast cancer patients acquire brain metastasis, yet potential therapeutic targets remain largely unknown. The type I insulin-like growth factor receptor (IGF- IR) is known to play a role in the progression of breast cancer and is currently being investigated in the clinical setting for various types of cancer. The present study demonstrates that the IGF-IR signaling axis is constitutively active in brain-seeking sublines of breast cancer cells, driving an increase in in vitro metastatic properties. We demonstrate that IGF-IR signaling is activated in an autocrine manner as a result of IGFBP3 overexpression in brain-seeking cells. Transient and stable knockdown of IGF-IR results in a downregulation of IGF-IR downstream signaling through phospho-AKT, as well as decreased in vitro migration and invasion of MDA- MB-231Br brain-seeking cells. Using an in vivo experimental brain metastasis model, we show that IGF-IR ablation attenuates the establishment of brain metastases and prolongs survival. Finally, we demonstrate that the malignancy of brain-seeking cells is attenuated by pharmacological inhibition with picropodophyllin, an IGF-IR-specific tyrosine kinase inhibitor. Together, our data suggest that the IGF-IR is an important mediator of brain metastasis and its ablation delays the onset of brain metastases in our model system.

The role of erbB2 receptor in human breast cancer metastasis

Overexpression of c-erbB-2 gene-encoded p185 has been correlated with lymph node metastasis and poor prognosis in breast cancer patients. To investigate whether overexpression of c-erbB-2 can enhance metastatic potential of human breast cancer cells, we compared the metastatic phenotypes of the parental MDA-MB-435 cells and the c-erbB-2 gene transfected 435.eB cells. In vivo experimental metastasis assays demonstrated that mice injected erbB2-overexpressing 435.eB transfectants formed significantly more metastatic tumors than the mice injected with parental and control cells. The changes in metastatic potential in vivo were accompanied by increased invasiveness in vitro . The transfectants and the parental cells all had similar growth rates and transformation potential. These findings suggest that c- erbB-2 gene can enhance the intrinsic metastatic potentials of MDA-MB-435 cells without increasing their transformation abilities. ^ Homophilic adhesion may affect invasive and metastatic potential of tumor cells. We found that Heregulin-β1 (HRG-β1), a growth factor that activates receptor kinases erbB3 and erbB4, can enhance aggregation of MCF-7 and SKBR3 human breast cancer cells. While investigating the downstream signals involved in HRG-β1-increased cell aggregation, we observed that HRG-β1 increased the kinase activities of extracellular signal-regulated protein kinase (ERK) and PI3K in these cells. By using different kinase inhibitors, we found that the HRG-β1-activated MEK1-ERK pathway has no demonstrable role in the induction of cell aggregation, whereas HRG-β1-activated PI3K is required for enhancing breast cancer cell aggregation. These results have provided one mechanism by which HRG-β1-activated signaling of erbB receptors may affect invasive/metastatic properties of breast cancer cells. ^ To identify the structural motifs within the erbB2 receptor that are required for erbB2 increased metastatic potential in breast cancer cells, we injected different forms of mutated erbB2 expressing MDA-MB-435 cell line transfectants with or without the EGF-like domain of heregulin-β1 protein (HRG/egf) into ICR-SCID mice to test the metastatic survival rate. The results show that an intact kinase domain of erbB2 receptor is required for erbB2 enhanced metastatic potential in these cells. The C-terminal tyrosine 1248 residue of erbB2 may also play a role in enhancing metastatic potential. Moreover, the results suggest that HRG/egf promote the metastatic potential of human breast cancer cells in vivo. ^

The antiapoptotic effect of overexpression c -erBb2 in breast cancer

Overexpression of the receptor tyrosine kinase p185ErbB2 confers taxol resistance in breast cancers and activation of p34Cdc2 is required for taxol-induced apoptosis and cytotoxicity. Here, we investigated the underlying mechanisms and found that overexpression of p185 ErbB2 inhibits taxol-induced apoptosis through two branches to inhibit activation of p34Cdc2. ^ Overexpression of p185ErbB2 in MDA-MB-435 cells by transfection transcriptionally upregulated p21Cip1, which associates with p34Cdc2, inhibits taxol-mediated p34Cdc2 activation, delays cell entrance to G2/M phase, and thereby inhibits taxol-induced apoptosis. In p21Cip1 antisense-transfected MDA-MB-435 cells or in p21−/− MEF cells, p185ErbB2 was unable to inhibit taxol-induced apoptosis. Therefore, p21Cip1 participates in the regulation of a G2/M checkpoint that contributes to resistance to taxol-induced apoptosis in p185ErbB2-overexpressing breast cancer cells. ^ Direct phosphorylation on Tyrosine-15 of p34Cdc2 by p185 ErbB2 receptor tyrosine kinase inhibits p34Cdc2 activation. The wild-type p185ErbB2 but not the kinase-defective mutant, when overexpressed in breast cancer cells, can phosphorylate p34Cdc2 on tyrosine (Tyr)15, an inhibitory phosphorylation site of p34 Cdc2. The kinase domain of the ErbB2 receptor was sufficient for binding to p34Cdc2 and directly phosphorylating the recombinant Cdc2. Phosphospecific Cdc2-Tyr15 immunoblot analyses, immunocomplex kinase assays, and phospho-amino acid analyses revealed that p185ErbB2 specifically phosphorylates Cdc2 on Tyr15. Phosphorylation of Cdc2-Tyr15 by ErbB2 is modulated during cell cycle and corresponded with delayed cell entry into G2/M phase. The kinase-defective p185ErbB2, which incapable of phosphorylating Cdc2-Tyr15, failed to inhibit taxol-induced activation and apoptosis, whereas the wild-type and the constitutive-active p185ErbB2 did. Increased Cdc2-Tyr15 phosphorylation was found in Erb132-overexpressing tumors from breast cancer patients. Thus, direct phosphorylation of Cdc2-Tyr15 by p185 ErbB2 RTK in breast cancer cells inhibits taxol-induced p34 Cdc2 activation and apoptosis, thereby conferring taxol resistance. ^

Estradiol and insulin cross -talk in breast cancer

Approximately 33% of clinical breast carcinomas require estrogens to proliferate. Epidemiological data show that insulin resistance and diabetes mellitus is 2–3 times more prevalent in women with breast cancer than those with benign breast lesions, suggesting a clinical link between insulin and estradiol. Insulin and estradiol have a synergistic effect on the growth of MCF7 breast cancer cells, and long-term estradiol treatment upregulates the expression of the key insulin signaling protein IRS-1. The goal of this study was to further define the mechanism(s) of cross-talk between insulin and estradiol in regulating the growth of breast cancer. Using MCF7 cells, acute treatment with insulin or estradiol alone was found to stimulate two activities associated with growth: Erk MAP kinase and PI 3-kinase. However, combined acute treatment had an antagonistic effect on both activities. Acute estradiol treatment inhibited the insulin-stimulated tyrosine phosphorylation of IRS-1 while increasing its serine phosphorylation; the serine phosphorylation was attenuated by the PI 3-kinase inhibitor wortmannin. The acute antagonism observed with combined estradiol and insulin are not consistent with the long-term synergistic effect on growth. In contrast, chronic estradiol treatment enhanced the insulin-sensitivity of breast cancer cells as measured by increases in total cellular insulin-stimulated tyrosine phosphorylation of IRS-1 and activation of PI 3-kinase. Estradiol stimulation of gene transcription was found to require PI 3-kinase activity but not MAP kinase activity. Insulin alone had no effect on ER transcriptional activity, but chronic treatment in combination with estradiol resulted in synergism of ER transcription. The synergistic effect of insulin and estradiol on MCF7 cell growth was also found to require PI 3-kinase but not MAP kinase activity. Therefore, chronic estradiol treatment increases insulin stimulation of PI 3-kinase, and PI 3-kinase is required for estradiol stimulation of gene transcription alone and in combined synergy with insulin. These data demonstrate that PI 3-kinase is the locus for the cross-talk between insulin and estradiol which results in enhanced breast cancer growth with long-term exposure to both hormones. This may have important clinical implications for women with high risk for breast cancer and/or diabetes mellitus. ^

Breast cancer -specific activation of topoisomerase IIalpha and its application in the tumor -targeting gene therapy

To ensure the success of systemic gene therapy, it is critical to enhance the tumor specificity and activity of the promoter. In the current study, we identified the breast cancer-specific activity of the topoisomerase IIα promoter. We further showed that cdk2 and cyclin A activate topoisomerase IIα promoter in a breast cancer-specific manner. An element containing an inverted CCAAT box (ICB) was shown to respond this signaling. When the ICB-harboring topoisomerase IIα minimal promoter was linked with an enhancer sequence from the cytomegalovirus immediate early gene promoter (CMV promoter), this composite promoter, CT90, exhibited activity comparable to or higher than the CMV promoter in breast cancer cells in vitro and in vivo, yet expresses much lower activity in normal cell lines and normal organs than the CMV promoter. A CT90-driven construct expressing BikDD, a potent pro-apoptotic gene, was shown to selectively kill breast cancer cells in vitro and to suppress mammary tumor development in an animal model of intravenously administrated, liposome-delivered gene therapy. Expression of BikDD was readily detectable in the tumors but not in the normal organs of CT90-BikDD-treated animals. Finally, we demonstrated that CT90-BikDD treatment potentially enhanced the sensitivity of breast cancer cells to chemotherapeutic agents, especially doxorubicin and taxol. The results indicate that liposomal CT90-BikDD is a novel and effective systemic breast cancer-targeting gene therapy, and its combination with chemotherapy may further improve the current adjuvant therapy for breast cancer. ^

Heregulin -beta 1 directly associates with RhoA via the immunoglobulin -like domain thereby modulating breast cancer metastasis-related properties

Heregulins constitute a family of growth factors belonging to the epidermal growth factor (EGF) family. Breast cancers that overexpress specific members of the EGF receptor family (EGFR, ErbB2, ErbB3, ErbB4) have increased metastatic potential, and Heregulin-β1 (HRGβ1), a ligand for ErbB3 and ErbB4, has also been shown to induce metastasis-related properties in breast cancer cells in vitro. The secreted form of the HRGβ1 is composed of five distinct structural domains, including the N-terminal domain, an immunoglobulin-like domain (IgG-like), a glycosylation domain, an EGF-like domain, and a β1-specific domain. Of these, the EGF-like domain is well characterized for its function in metastasis-related properties as well as its structure. However, the contributions of the other HRGβ1 domains in breast cancer metastasis remains unclear. ^ To investigate this, HRGβ1 proteins with targeted domain deletions were purified and subjected to assays for metastasis-related properties, including aggregation, invasion, activation of EGFR family members, and motility of breast cancer cells. These assays showed that retaining the EGF-like domain of HRGβ1 is important for activation of EGFRs. Interestingly, the HRGβ1 protein lacking the IgG-like domain (NGEB) led to a decrease in breast cancer cell motility, indicating the IgG-like domain modulates cell motility, an important step in cancer metastasis. ^ To understand the underlying mechanisms, I performed protein sequence and structural analysis of HRGβ1 and identified that the IgG-like domain of HRGβ1 shares sequence homology and three-dimensional structural similarity with the IgG-like domain of TRIO. TRIO is a cytoplasmic protein that directly associates with RhoA, a GTPase involved in cell reorganization and cell motility. Therefore, I hypothesized that HRGβ1 may translocate inside the breast cancer cells through receptor mediated endocytosis and bind to RhoA via its IgG-like domain. I show wild type HRGβ1 but not NGEB binds RhoA in vitro and in vivo, leading to RhoA activation. Inhibition of HRG-β1 internalization via endocytosis disrupted HRGβ1 binding to RhoA. Additionally, breast cancer cell motility induced by HRG-β1 is reduced after treatment with inhibitors to both endocytosis and RhoA function, similar to levels seen with NGEB treatment. ^ Thus, in addition to the well-known role of HRGβ1 as an extracellular stimulator of the EGFR family members, HRGβ1 also functions within the cell as a binding partner and activator of RhoA to modulate cancer cell motility. ^

Survival analysis of circulating tumor cells in triple-negative breast cancer

Background. Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females, accounting for 23% (1.38 million) of the total new cancer cases and 14% (458,400) of the total cancer deaths in 2008. [1] Triple-negative breast cancer (TNBC) is an aggressive phenotype comprising 10–20% of all breast cancers (BCs). [2-4] TNBCs show absence of estrogen, progesterone and HER2/neu receptors on the tumor cells. Because of the absence of these receptors, TNBCs are not candidates for targeted therapies. Circulating tumor cells (CTCs) are observed in blood of breast cancer patients even at early stages (Stage I & II) of the disease. Immunological and molecular analysis can be used to detect the presence of tumor cells in the blood (Circulating tumor cells; CTCs) of many breast cancer patients. These cells may explain relapses in early stage breast cancer patients even after adequate local control. CTC detection may be useful in identifying patients at risk for disease progression, and therapies targeting CTCs may improve outcome in patients harboring them. Methods . In this study we evaluated 80 patients with TNBC who are enrolled in a larger prospective study conducted at M D Anderson Cancer Center in order to determine whether the presence of circulating tumor cells is a significant prognostic factor in relapse free and overall survival . Patients with metastatic disease at the time of presentation were excluded from the study. CTCs were assessed using CellSearch System™ (Veridex, Raritan, NJ). CTCs were defined as nucleated cells lacking the presence of CD45 but expressing cytokeratins 8, 18 or 19. The distribution of patient and tumor characteristics was analyzed using chi square test and Fisher's exact test. Log rank test and Cox regression analysis was applied to establish the association of circulating tumor cells with relapse free and overall survival. Results. The median age of the study participants was 53years. The median duration of follow-up was 40 months. Eighty-eight percent (88%) of patients were newly diagnosed (without a previous history of breast cancer), and (60%) of patients were chemo naïve (had not received chemotherapy at the time of their blood draw for CTC analysis). Tumor characteristics such as stage (P=0.40), tumor size (P=69), sentinel nodal involvement (P=0.87), axillary lymph node involvement (P=0.13), adjuvant therapy (P=0.83), and high histological grade of tumor (P=0.26) did not predict the presence of CTCs. However, CTCs predicted worse relapse free survival (1 or more CTCs log rank P value = 0.04, at 2 or more CTCs P = 0.02 and at 3 or more CTCs P < 0.0001) and overall survival (at 1 or more CTCs log rank P value = 0.08, at 2 or more CTCs P = 0.01 and at 3 or more CTCs P = 0.0001. Conclusions. The number of circulating tumor cells predicted worse relapse free survival and overall survival in TNBC patients.^

Prime-boost vaccination with plasmid and adenovirus gene vaccines control HER2/neu+ metastatic breast cancer in mice.

INTRODUCTION: Once metastasis has occurred, the possibility of completely curing breast cancer is unlikely, particularly for the 30 to 40% of cancers overexpressing the gene for HER2/neu. A vaccine targeting p185, the protein product of the HER2/neu gene, could have therapeutic application by controlling the growth and metastasis of highly aggressive HER2/neu+ cells. The purpose of this study was to determine the effectiveness of two gene vaccines targeting HER2/neu in preventive and therapeutic tumor models. METHODS: The mouse breast cancer cell line A2L2, which expresses the gene for rat HER2/neu and hence p185, was injected into the mammary fat pad of mice as a model of solid tumor growth or was injected intravenously as a model of lung metastasis. SINCP-neu, a plasmid containing Sindbis virus genes and the gene for rat HER2/neu, and Adeno-neu, an E1,E2a-deleted adenovirus also containing the gene for rat HER2/neu, were tested as preventive and therapeutic vaccines. RESULTS: Vaccination with SINCP-neu or Adeno-neu before tumor challenge with A2L2 cells significantly inhibited the growth of the cells injected into the mammary fat or intravenously. Vaccination 2 days after tumor challenge with either vaccine was ineffective in both tumor models. However, therapeutic vaccination in a prime-boost protocol with SINCP-neu followed by Adeno-neu significantly prolonged the overall survival rate of mice injected intravenously with the tumor cells. Naive mice vaccinated using the same prime-boost protocol demonstrated a strong serum immunoglobulin G response and p185-specific cellular immunity, as shown by the results of ELISPOT (enzyme-linked immunospot) analysis for IFNgamma. CONCLUSION: We report herein that vaccination of mice with a plasmid gene vaccine and an adenovirus gene vaccine, each containing the gene for HER2/neu, prevented growth of a HER2/neu-expressing breast cancer cell line injected into the mammary fat pad or intravenously. Sequential administration of the vaccines in a prime-boost protocol was therapeutically effective when tumor cells were injected intravenously before the vaccination. The vaccines induced high levels of both cellular and humoral immunity as determined by in vitro assessment. These findings indicate that clinical evaluation of these vaccines, particularly when used sequentially in a prime-boost protocol, is justified.

NOVEL AMINO ACID TRANSPORTER-TARGETED RADIOTRACERS FOR BREAST CANCER IMAGING

Breast cancer is the most common malignancy among women in the world. Its 5-year survival rate ranges from 23.4% in patients with stage IV to 98% in stage I disease, highlighting the importance of early detection and diagnosis. 18F-2-Fluoro-2-deoxy-glucose (18F-FDG), using positron emission tomography (PET), is the most common functional imaging tool for breast cancer diagnosis currently. Unfortunately, 18F-FDG-PET has several limitations such as poorly differentiating tumor tissues from inflammatory and normal brain tissues. Therefore, 18F-labeled amino acid-based radiotracers have been reported as an alternative, which is based on the fact that tumor cells uptake and consume more amino acids to sustain their uncontrolled growth. Among those radiotracers, 18F-labeled tyrosine and its derivatives have shown high tumor uptake and great ability to differentiate tumor tissue from inflammatory sites in brain tumors and squamous cell carcinoma. They enter the tumor cells via L-type amino acid transporters (LAT), which were reported to be highly expressed in many cancer cell lines and correlate positively with tumor growth. Nevertheless, the low radiosynthesis yield and demand of an on-site cyclotron limit the use of 18F-labeled tyrosine analogues. In this study, four Technetium-99m (99mTc) labeled tyrosine/ AMT (α-methyl tyrosine)-based radiotracers were successfully synthesized and evaluated for their potentials in breast cancer imaging. In order to radiolabel tyrosine and AMT, the chelators N,N’-ethylene-di-L-cysteine (EC) and 1,4,8,11-tetra-azacyclotetradecane (N4 cyclam) were selected to coordinate 99mTc. These chelators have been reported to provide stable chelation ability with 99mTc. By using the chelator technology, the same target ligand could be labeled with different radioisotopes for various imaging modalities for tumor diagnosis, or for internal radionuclide therapy in future. Based on the in vitro and in vivo evaluation using the rat mammary tumor models, 99mTc-EC-AMT is considered as the most suitable radiotracer for breast cancer imaging overall, however, 99mTc-EC-Tyrosine will be more preferred for differential diagnosis of tumor from inflammation.

The prognostic significance of sialyl-Tn antigen in women treated with adjuvant chemotherapy for breast cancer

Background and purpose. Sialyl-Tn(STn) represents an aberrantly glycosylated mucin epitope which is expressed in breast cancer and other adenocarcinomas and is an important target for the development of novel immunotherapeutic approaches. It is a marker of adverse prognosis in colon and ovarian cancer, but information about its prognostic impact in breast cancer is limited. The primary aim of the present study was to investigate the influence of STn expression on outcome of invasive breast cancer in 207 women who received anthracyline-containing adjuvant chemotherapy in a prospective clinical trial.^ Methods. Expression of STn was determined by an immunohistochemical procedure using the B72.3 monoclonal antibody. The extent of staining was determined by two observers using a 0 through 4 point scale, with 0 representing $<$5% of cells staining; 1: 5-25%; 2: 26-50%; 3: 51-75%; and 4: $>$75%. Intraobserver and interobserver agreement was.78-.92 (kappa). Kaplan-Meier and Cox proportional regression survival analyses were used to compare STn-negative and STn-positive patients.^ Results. Forty-eight (23%) of the 207 specimens demonstrated positive staining of STn. With a median follow-up of five years, STn-positivity was associated with a higher 5-year recurrence-free survival time than STn-negativity (67% vs. 80%, respectively; p = 0.03). STn expression was significantly associated with menopausal status (p = 0.04) but not other conventional prognostic markers. The risk of breast cancer recurrence and death was assessed by multivariate Cox regression analyses with adjustment for lymph node status, tumor size, menopausal status, hormone receptor status, nuclear grade, S-phase fraction and ploidy. In the final multivariate model for recurrence-free survival, the three factors that showed prognostic significance were: lymph node status (hazard ratio (HR) 3.04, 95% confidence interval (CI) 1.08-8.49), STn expression (HR 2.02, 95% CI 1.09-3.73), and tumor size (HR 1.96, 95% CI 1.05-3.64). STn was also associated with worse overall survival (HR 2.16, 95% CI 0.95-4.92) in multivariate analysis.^ Conclusion. STn antigen was shown to be a predictor of poor outcome in breast cancer. This tumor-associated antigen may be a valuable marker for identifying individuals at high risk of developing recurrent disease who may benefit from adjuvant therapy targeted at STn following definitive local therapy. Further study is needed to clarify the biologic and prognostic role of STn in breast cancer. ^

Study of retinoic acid signaling in cancer cells: Cloning and characterization of retinoic acid responsive genes

Retinoids such as all-trans-retinoic acid (ATRA) are promising agents for cancer chemoprevention and therapy. ATRA can cause growth inhibition, induction of differentiation and apoptosis of a variety of cancer cells. These effects are thought to be mediated by nuclear retinoids receptors which are involved in ligand-dependent transcriptional activation of downstream target genes. Using differential display, we identified several retinoic acid responsive genes in the head and neck squamous carcinoma cells and lung cancer cells, including tissue type transglutaminase, cytochrome P450-related retinoic acid hydroxylase, and a novel gene, designated RAIG1. RAIG1 has two transcripts of 2.4 and 6.8 kbp, respectively, that are generated by alternative selection of polyadenylation sites. Both transcripts have the same open reading frame that encodes a protein comprised of 357 amino acid residues. The deduced RAIG1 protein sequence contains seven transmembrane domains, a signature structure of G protein-coupled receptors. RAIG1 mRNA is expressed at high level in fetal and adult lung tissues. Induction of RAIG1 expression by ATRA is rapid and dose-dependent. A fusion protein of RAIG1 and the green fluorescent protein was localized in the cell surface membrane and perinuclear vesicles in transiently transfected cells. The locus for RAIG1 gene was mapped to a region between D12S358 and D12S847 on chromosome 12p12.3-p13. Our study of the novel retinoic acid induced gene RAIG1 provide evidence for a possible interaction between retinoid and G protein signaling pathways.^ We further examined RAIG1 expression pattern in a panel of 84 cancer cell lines of different origin. The expression level varies greatly from very high to non-detectable. We selected a panel of different cancer cells to study the effects of retinoids and other differentiation agents. We observed: (1) In most cases, retinoids (including all-trans retinoic acid, 4HPR, CD437) could induce the expression of RAIG-1 in cells from cancers of the breast, colon, head and neck, lung, ovarian and prostate. (2) Compare to retinoids, butyrate is often a more potent inducer of RAIG-1 expression in many cancer cells. (3) Butyrate, Phenylacetate butyrate, (R)P-Butyrate and (S)P-Butyrate have different impact on RAIG1 expression which varies among different cell lines. Our results indicate that retinoids could restore RAIG1 expression that is down-regulated in many cancer cells.^ A mouse homologous gene, mRAIG1, was cloned by 5$\sp\prime$ RACE reaction. mRAIG1 cDNA has 2105 bp and shares 63% identity with RAIG1 cDNA. mRAIG1 encodes a polypeptide of 356 amino acid which is 76% identity with RAIG1 protein. mRAIG1 protein also has seven transmembrane domains which are structurally identical to those of RAIG1 protein. Only one 2.2 kbp mRAIG1 transcript could be detected. The mRAIG1 mRNA is also highly expressed in lung tissue. The expression of mRAIG1 gene could be induced by ATRA in several mouse embryonal carcinoma cells. The induction of mRAIG1 expression is associated with retinoic acid-induced neuroectoderm differentiation of P19 cells. Similarity in cDNA and protein sequence, secondary structure, tissue distribution and inducible expression by retinoic acid strongly suggest that the mouse gene is the homologue of the human RAIG1 gene. ^

New implications of E1A gene therapy in breast and ovarian cancer

A variety of human cancers overexpress the HER-2/neu proto-oncogene. Among patients with breast and ovarian cancers this HER-2/ neu overexpression indicates an unfavorable prognosis, with a shorter overall survival duration and a lower response rate to chemotherapeutic agents. Downregulation of HER-2/neu gene expression in cancer cells through attenuation of HER-2/neu promoter activity is, therefore, an attractive strategy for reversing the transformation phenotype and thus the chemoresistance induced by HER-2/neu overexpression. ^ A viral transcriptional regulator, the adenovirus type 5 E1A (early region 1A) that can repress the HER-2/neu promoter, had been identified in the laboratory of Dr. Mien-Chie Hung. Following the identification of the E1A gene, a series of studies revealed that repression of HER-2/neu by the E1A gene which can act therapeutically as a tumor suppressor gene for HER-2/ neu-overexpressing cancers. ^ The results of these preclinical studies became the basis for a phase I trial for E1A gene therapy among patients with HER-2/neu-overexpressing breast and ovarian cancer. In this dissertation, three primary questions concerned with new implications of E1A gene therapy are addressed: First, could E1A gene therapy be incorporated with conventional chemotherapy? Second, could the E1A gene be delivered systemically to exert an anti-tumor effect? And third, what is the activity of the E1A gene in low-HER-2/neu-expressing cancer cells? ^ With regard to the first question, the studies reported in this dissertation have shown that the sensitivity of HER-2/neu-overexpressing breast and ovarian cancer to paclitaxel is in fact enhanced by the downregulation of HER-2/neu overexpression by E1A. With regard to the second question, studies have shown that the E1A gene can exert anti-tumor activity by i.v. injection of the E1A gene complexed with the novel cationic liposome/protamine sulfate/DNA type I (LPDI). And with regard to the third question, the studies of low-HER-2/ neu-expressing breast and ovarian cancers reported here have shown that the E1A gene does in fact suppress metastatic capability. It did not, however, suppress the tumorigenicity. ^ Three conclusions can be drawn from the experimental findings reported in this dissertation. Combining paclitaxel with E1A gene therapy may expand the implications of the gene therapy in the future phase II clinical trial. Anti-tumor activity at a distant site may be achieved with the i.v. injection of the E1A gene. Lastly when administered therapeutically the anti-metastatic effect of the E1A gene in low-HER-2/neu-expressing breast cancer cells may prevent metastasis in primary breast cancer. (Abstract shortened by UMI.)^

TUMOR PROGRESSION: ANALYSIS OF THE INSTABILITY OF THE METASTATIC PHENOTYPE, SENSITIVITY TO RADIATION AND CHEMOTHERAPY (PHENOTYPIC DRIFT, BREAST CANCER)

The major complications for tumor therapy are (i) tumor spread (metastasis); (ii) the mixed nature of tumors (heterogeneity); and (iii) the capacity of tumors to evolve (progress). To study these tumor characteristics, the rat 13762NF mammary adenocarcinoma was cloned and studied for metastatic properties and sensitivities to therapy (chemotherapy, radiation and hyperthermia). The cell clones were heterogeneous and no correlation between metastatic potential and therapeutic sensitivities was observed. Further, these phenotypes were unstable during passage in vitro; yet, the changes were clone dependent and reproducible using different cryoprotected cell stocks. To understand the phenotypic instability, subclones were isolated from low and high passage cell clones. Each subclone possessed a unique composite phenotype. Again, no apparent correlation was seen between metastatic potential and sensitivity to therapy. The results demonstrated that (1) tumor cells are heterogeneous for multiple phenotypes; (2) tumor cells are unstable for multiple phenotypes; (3) the magnitude, direction and time of occurrence of phenotypic drift is clone dependent; (4) the sensitivity of cell clones to ionizing radiation (gamma or heat) and chemotherapy agents is independent of their metastatic potential; (5) shifts in metastatic potential and sensitivity to therapy may occur simultaneously but are not linked; and (6) tumor cells independently diverge to form several subpopulations with unique phenotypic profiles. ^

Antitumor activity of an Ets protein, PEA3, in breast cancer cell lines MDA-MB-361DYT2 and BT474M1

Polyomavirus enhancer activator 3 (PEA3) is a member of the Ets family of transcription factors. We demonstrated in a previous study that, through down-regulating the HER-2/neu oncogene at the transcriptional level, PEA3 can inhibit the growth and tumor development of HER-2/neu-overexpressing ovarian cancer cells. Here, we established stable clones of the human breast cancer cell line MDA-MB-361DYT2 that express PEA3 under the control of a tetracycline-inducible promoter. The expression of PEA3 in this cell line inhibited cell growth and resulted in cell cycle delay in the G1 phase independently of the HER-2/neu down-regulation. In an orthotopic breast cancer model, we showed that expression of PEA3 inhibited tumor growth and prolonged the survival of tumor-bearing mice. In a parallel experiment in another breast cancer cell line, BT474M1, we were unable to obtain stable PEA3-inducible transfectants, which suggests that PEA3 possessed a strong growth inhibitory effect in this cell line. Indeed, PEA3 coupled with the liposome SN2 demonstrated therapeutic effects in mice bearing tumors induced by BT474M1. These results provide evidence that the PEA3 gene could function as an antitumor and gene therapy agent for human breast cancers. ^