Collapsin response mediator protein-1: a lung cancer invasion suppressor gene with nerve.
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Carcinoma↗
Biomedical subjects
P S Steeg
Publications and source records attributed to P S Steeg.
Elevation of breast carcinoma Nm23-H1 metastasis suppressor gene expression and reduced motility by DNA methylation inhibition.
We hypothesize that elevation of Nm23-H1 expression in micrometastatic breast cancer cells may inhibit their metastatic colonization and further invasion, and induce differentiation, thus resulting in a clinical benefit. The current study investigated the possible contribution of DNA methylation to the regulation of Nm23-H1 expression, based on the observation that two CpG islands are present in its promoter. 5-Aza-2'-deoxycytidine (5-Aza-CdR), a DNA methylation inhibitor, increased the Nm23-H1 expression of 5 of 11 human breast carcinoma cell lines in vitro, including 3 of 3 metastatically competent lines. Increased Nm23-H1 expression was accompanied by a reduction in motility in vitro, with minimal effect on proliferation. Both increased Nm23-H1 expression and decreased motility were observed using low (75 nM) concentrations of 5-Aza-CdR. Array analysis of MDA-MB-231 breast carcinoma cells treated with 5-Aza-CdR confirmed the elevation of nm23-H1 mRNA, whereas relatively few other genes exhibited altered expression. Bisulfite sequencing of the two CpG islands in a panel of cell lines and in 20 infiltrating ductal carcinomas revealed that one island (-3090 bp to -3922 bp) exhibited infrequent differential methylation. The data indicate that DNA methylation inhibitors can directly or indirectly cause both elevation of Nm23-H1 expression and decreased function in one aspect of metastasis, motility.
Antimetabolites, Antineoplastic↗
Cyclin D1 in breast premalignancy and early breast cancer: implications for prevention and treatment.
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Apoptosis↗
New approaches to proteomic analysis of breast cancer.
Proteomic based approaches are beginning to be utilized to study the natural history and treatment of breast cancer. A variety of proteomics approaches are under study, and are summarized herein. Two-dimensional gel electrophoresis (2D-PAGE) is still the foundation of most proteomics studies. We present an analysis of 2D-PAGE studies reported to date in breast cancer, including those examining normal/tumor differences and selected populations of breast cells. Newer technologies such as laser capture microdissection and highly sensitive mass spectrometry methods are currently being used together to identify greater numbers of lower abundance proteins that are differentially expressed between defined cell populations. Novel technologies still in developmental phases will enable identification of validated targets in small biopsy specimens, including high density protein arrays, antibody arrays and lysate arrays. Surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) analysis enables the high throughput characterization of lysates from very few tumor cells and may be best suited for clinical biomarker studies. We present SELDI-TOF data herein to show the accuracy of the method in a small cohort of breast tumors, as well as its potential discriminatory capability. Such technologies are expected to supplement our armamentarium of mRNA-based assays, and provide critical information on protein levels and post-translational modifications.
Breast Neoplasms↗
Molecular biology of breast cancer metastasis. 'Has it spread?': disarming one of the most terrifying questions.
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Animals↗
Molecular biology of breast cancer metastasis. Genetic regulation of human breast carcinoma metastasis.
The present is an overview of recent data that describes the genetic underpinnings of the suppression of cancer metastasis. Despite the explosion of new information about the genetics of cancer, only six human genes have thus far been shown to suppress metastasis functionally. Not all have been shown to be functional in breast carcinoma. Several additional genes inhibit various steps of the metastatic cascade, but do not necessarily block metastasis when tested using in vivo assays. The implications of this are discussed. Two recently discovered metastasis suppressor genes block proliferation of tumor cells at a secondary site, offering a new target for therapeutic intervention.
Antigens, CD↗
Radiation and the Apo2L/TRAIL apoptotic pathway preferentially inhibit the colonization of premalignant human breast cells overexpressing cyclin D1.
The role of cyclin D1 overexpression in human breast premalignancy was investigated using immortal, nontumorigenic MCF-10A cells. Previous work documented that cyclin D1 overexpression promoted in vitro anchorage-independent colonization. We now report that the colonization of MCF-10A cyclin D1 transfectants was preferentially inhibited by gamma-radiation and specific classes of apoptosis inducers [Apo-2 ligand (Apo-2L), but not tumor necrosis factor alpha]. Antibody inhibition studies and semiquantitative PCR indicated that radiation inhibition of colonization was partially mediated via the Apo2L/TRAIL pathway. The apoptotic removal of cyclin D1-overexpressing, colonization-competent premalignant breast cells by Apo2L/TRAIL or other biologicals may represent a novel approach to the prevention of breast cancer.
Apoptosis↗
Nm23/nucleoside diphosphate kinase in human cancers.
Tumor metastasis is the leading cause of death in cancer patients. From a series of tumor cohort studies, low expression of Nm23/NDP kinase has been correlated with poor patient prognosis and survival, lymph node infiltration, and histopathological indicators of high metastatic potential in a number of cancer types, including mammary and ovarian carcinomas and melanoma. In other tumor types, no correlation has been established. Transfection of Nm23/NDP kinase cDNA into highly metastatic breast, melanoma, prostrate and squamous cell carcinomas, and colon adenocarcinoma cells significantly reduced the metastatic competency of the cells in vivo. In culture, cell motility, invasion, and colonization were inhibited, whereas tumorigenicity and cellular proliferation were not affected, indicating that Nm23/NDP kinase acts as a metastasis suppressor.
Gene Expression Profiling↗
Cyclin D1 overexpression in a model of human breast premalignancy: preferential stimulation of anchorage-independent but not anchorage-dependent growth is associated with increased cdk2 activity.
Cyclin D1 is frequently overexpressed in human breast ductal carcinoma in situ (DCIS) specimens, which confer a high risk for the development of infiltrating ductal carcinoma. If causally involved in the genesis of human breast malignancy, cyclin D1 may represent an interesting target for chemopreventive approaches, as it sits at the junction of many growth factor and hormonal pathways. We have used the MCF-10A human breast cell line, derived from a mastectomy containing a low risk premalignant lesion, as a model system. Three cyclin D1 transfectants exhibited physiologically relevant levels of transgene overexpression, but no coordinate overexpression of other cell cycle related genes. Proliferation assays, flow cytometry, and cdk enzymatic assays of anchorage-dependent proliferation indicated only a minimal and transient effect of cyclin D1. In contrast, cyclin D1 overexpression significantly stimulated anchorage-independent colonization in soft agar or methylcellulose, accompanied by greater Gl-S progression. The cdk4 activity of the control- and cyclin D1 transfectants in colonization assays was comparable, but the cdk2 activity was higher in the latter. Injection of control- and cyclin D1 transfected MCF-10A cells in matrigel into nude mice failed to produce tumors within 1.5 years. The data suggest that cyclin D1 overexpression is an early feature of breast neoplastic progression, and can contribute to cancer development through the promotion of colonization.
Animals↗
Wild-type NM23-H1, but not its S120 mutants, suppresses desensitization of muscarinic potassium current.
NM23 (NDP kinase) modulates the gating of muscarinic K+ channels by agonists through a mechanism distinct from GTP regeneration. To better define the function of NM23 in this pathway and to identify sites in NM23 that are important for its role in muscarinic K+ channel function, we utilized MDA-MB-435 human breast carcinoma cells that express low levels of NM23-H1. M2 muscarinic receptors and GIRK1/GIRK4 channel subunits were co-expressed in cells stably transfected with vector only (control), wild-type NM23-H1, or several NM23-H1 mutants. Lysates from all cell lines tested exhibit comparable nucleoside diphosphate (NDP) kinase activity. Whole cell patch clamp recordings revealed a substantial reduction of the acute desensitization of muscarinic K+ currents in cells overexpressing NM23-H1. The mutants NM23-H1P96S and NM23-H1S44A resembled wild-type NM23-H1 in their ability to reduce desensitization. In contrast, mutants NM23-H1S120G and NM23-H1S120A completely abolished the effect of NM23-H1 on desensitization of muscarinic K+ currents. Furthermore, NM23-H1S120G potentiated acute desensitization, indicating that this mutant retains the ability to interact with the muscarinic pathway, but has properties antithetical to those of the wild-type protein. We conclude that NM23 acts as a suppressor of the processes leading to the desensitization of muscarinic K+ currents, and that Ser-120 is essential for its actions.
Humans↗
Cyclins and breast cancer.
Cyclins are regulatory subunits for cyclin dependent kinases in the coordination of the cell cycle. Cyclins can also serve non-cell cycle functions, such as the transactivation of estrogen receptor by cyclin D. Evidence for the participation of the G1 cyclins D and E in breast cancer is summarized, including transgenic and knockout mice, transfections, and expression patterns in cohort studies. Overexpression of cyclin D has been reported in ductal carcinoma in situ (DCIS), and similar overexpression of cyclin E is suggested. Strategies to reduce cyclin expression are discussed as potential prevention efforts.
Animals↗
Nm23-H1: genetic alterations and expression patterns in tumor metastasis.
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Cell Differentiation↗
Breast cancer advocacy and basic research: a scientist's perspective.
The breast cancer advocacy community has impacted the course of basic research in several ways. They have heightened public awareness of research initiatives, and increased funding for basic and other research efforts. Advocates now participate in many study sections, which prioritize research proposals for funding, and scientific oversight committees. This article discusses these changes and how they have worked to date, and future efforts for consideration.
Journal Article↗
A high-risk lesion for invasive breast cancer, ductal carcinoma in situ, exhibits frequent overexpression of retinoid X receptor.
The development of prevention strategies for breast cancer will require a molecular map of carcinogenesis. We have investigated gene expression patterns in premalignant and early carcinomatous human breast lesions that confer to the patient varying risks for developing invasive breast cancer. The relative expression levels of one of the retinoid receptors, retinoid X receptor (RXR), was determined by in situ hybridization to 58 biopsy specimens; RXR mRNA grain density over each lesion was compared to that over the normal ductal/lobular units in each section. Overexpression of RXR mRNA was observed in 66% of noncomedo ductal carcinoma in situ (DCIS), which confer a >8-fold increase in breast cancer risk, and 88% of comedo DCIS lesions, which are associated with a yet higher risk. In contrast, only 8% of lesions that confer little or no increase in breast cancer risk overexpressed RXR mRNA (P = 0.0008). Limited in situ hybridization data using retinoic acid receptor (RAR) riboprobes showed overexpression of RAR alpha, but not RAR beta or -gamma, in only a modest percentage (36%) of cases, suggesting that all members of the retinoid receptor superfamily are not similarly regulated. Immunohistochemistry performed on 52 DCIS specimens for alpha, beta, and gamma isoforms of RXR confirmed its overexpression at the protein level and implicate RXR alpha as the predominant overexpressed form. The data indicate that RXR overexpression is associated with an increased risk for the development of invasive breast cancer in human breast lesions and suggest the hypothesis that it is causally involved in breast oncogenesis. The implications for retinoid chemoprevention are discussed.
Biomarkers, Tumor↗
Nm23 and tumour metastasis: basic and translational advances.
The nm23 genes were discovered on the basis of their reduced expression by highly metastatic cell lines. This trend was confirmed in cohorts of several types of human carcinomas and melanomas. Several transfection studies have demonstrated the suppressive effect of nm23 overexpression on the metastatic aggressiveness of melanoma and breast carcinoma cells in vivo. These transfection experiments have also demonstrated an effect of nm23 overexpression on cellular functions involved in the metastatic phenotype, such as cell motility, and point to a regulatory role for Nm23 proteins in cellular signalling pathways. Nm23 homologues from various species are also involved in normal tissue development and differentiation. Transfection of nm23-H1 into breast cancer cells provided a functional demonstration of the involvement of this gene in the differentiation of mammary epithelial cells. However, the molecular mechanism of these biological effects remains unknown. Several biochemical activities have been reported for Nm23, including NDP kinase activity, serine autophosphorylation and protein-histidine kinase activity. To define the possible significance of these biochemical activities, we carried out site-directed mutagenesis of the relevant codons of nm23-H1 cDNA and studied the effects upon transfection into MDA-MB-435 human breast carcinoma cells. We have also used Nm23 expression as a molecular marker to identify novel compounds that are active against the most aggressive tumour cells. This approach revealed that none of the standard agents currently in clinical use is preferentially active against the most aggressive tumour cells, and allowed us to identify new compounds that are preferentially inhibitory towards low-Nm23-expressing breast carcinoma and melanoma cell lines. This analysis also revealed a significant correlation between Nm23 levels and sensitivity of the tumour cells to alkylating agents. A functional implication of Nm23 proteins in this phenomenon was demonstrated after transfection of nm23 cDNAs into melanoma and breast and ovarian carcinoma cells.
Amino Acid Sequence↗
Nm23/PuF does not directly stimulate transcription through the CT element in vivo.
Decreased levels of the nm23 gene product have been correlated with increased tumor metastatic potential in a variety of malignancies. At least a subset of the regulatory properties of Nm23 has been proposed to be due to transactivation of the human c-myc oncogene through binding to a homopyrimidine tract 140 base pairs upstream of the transcription start site (termed the CT element or the PuF site). Conventional transcription factors possess DNA binding and transactivation domains; Nm23 fusion proteins were used to address two questions. First, if provided with a well characterized DNA binding domain, does Nm23 possess a transactivation domain capable of stimulating transcription of an appropriate reporter? Second, if provided with a potent transactivation domain, is the DNA binding of Nm23 of sufficient specificity and affinity to direct the fusion protein to a CT-dependent reporter? Since reporter gene expression was not stimulated in either case, we conclude that Nm23 does not directly stimulate transcription through binding to the CT element and that its antimetastatic and other reported functions are likely due to other biochemical activities.
Animals↗
Two-component kinase-like activity of nm23 correlates with its motility-suppressing activity.
Nm23 genes, which encode nucleoside diphosphate kinases, have been implicated in suppressing tumor metastasis. The motility of human breast carcinoma cells can be suppressed by transfection with wild-type nm23-H1, but not by transfections with two nm23-H1 mutants, nm23-H1(S12OG) and nm23-H1(P96S). Here we report that nm23-H1 can transfer a phosphate from its catalytic histidine to aspartate or glutamate residues on 43-kDa membrane proteins. One of the 43-kDa membrane proteins was not phosphorylated by either nm23-H1(P96S) or nm23-H1(S120G), and another was phosphorylated much more slowly by nm23-H1(P96S) and by nm23-H1(S120G) than by wild-type nm23-H1. Nm23-H1 also can transfer phosphate from its catalytic histidine to histidines on ATP-citrate lyase and succinic thiokinase. The rates of phosphorylation of ATP-citrate lyase by nm23-H1(S120G) and nm23-H1(P96S) were similar to that by wild-type nm23-H1. The rate of phosphorylation of succinic thiokinase by nm23-H1(S120) was similar to that by wild-type nm23-H1, and the rate of phosphorylation of succinic thiokinase by nm23-H1(P96S) was about half that by wild-type nm23-H1. Thus, the transfer of phosphate from nm23-H1 to aspartates or glutamates on other proteins appears to correlate better with the suppression of motility than does the transfer to histidines.
Animals↗
Inhibition of cyclin D expression in human breast carcinoma cells by retinoids in vitro.
Transfection and transgenic mouse experiments supported an oncogenic role for cyclin D1 in breast cancer. We recently reported that noninvasive carcinoma in situ lesions of the human breast overexpress cyclin D, suggesting that this molecular event may represent a valuable target for chemoprevention. The purpose of the present series of investigations was to identify agents which could reduce the cyclin D expression of breast cells. We report that 9-cis retinoic acid (9-cis RA) and all trans retinoic acid (tRA) inhibited the cyclin D1 and D3 expression levels of human MCF-7, ZR-75 and T-47D breast carcinoma cells in vitro. Where detectable, similar trends were observed in the immortalized, HBL-100 and MCF-10A breast cell lines. Cyclin D2 was undetectable. The effect of retinoids was both dose- and time-dependent, and correlated with altered cell cycle kinetics and proliferative status. Retinoids were also found to inhibit the expression levels of other cell cycle related proteins, including Cdk2 and Cdk4, resulting in lower kinase activities. In contrast to other breast prevention studies, no synergistic effect was observed with retinoids and tamoxifen. The data indicate that retinoids can potently reduce cyclin D expression levels in a variety of breast cell lines in vitro, and suggest further consideration of this mechanism for the chemoprevention of breast cancer.
Breast Neoplasms↗