Free insulin-like growth factor-I and breast cancer risk

Insulin-like growth factor-I (IGF-I) has mitogenic and anti-apoptotic effects on breast cancer cells. Epidemiologic studies have shown that high plasma levels of IGF-I and low levels of IGF binding protein (BP)-3 are associated with increased risk of breast cancer in premenopausal women. The actions of IGF-I are mediated through the IGF-I receptor (IGF-IR) and are regulated by IGFBPs. In circulation, most of the IGF-I binds to IGFBP-3, and binding of IGF-I to IGFBP-3 inhibits the actions of IGF-I. Since free IGF-I, which does not bind to IGFBPs, can readily cross the endothelial barrier to interact with IGF-IR, circulating free IGF-I is thought to be more relevant to the biologic activity of IGF-I. To examine the association of free IGF-I with breast cancer, we compared free IGF-I levels between 40 newly diagnosed breast cancer patients and 40 age- and race-matched healthy controls. Plasma levels of free IGF-I, total IGF-I and IGF-II, as well as total, intact and fragment IGFBP-3, were measured using commercial immunoassay kits. The association between IGF-I and breast cancer was examined using the conditional logistic regression analysis. Analysis of correlation (Spearman) showed that free IGF-I was correlated with total IGF-I and IGFBP-3 but not with IGF-II. The odds ratios for breast cancer patients having high plasma IGF-I (> or = median) after adjusting for menopausal status and IGFBP-3 were 2.00 (p < o r = 0.376) for total IGF-I and 6.31 (p < or = 0.047) for free IGF-I. A high ratio of IGF-I to IGFBP-3 was also associated with breast cancer (p < 0.05). No association was found for IGF-II, nor for total, intact and fragment IGFBP-3. The findings of this study suggest that measuring free IGF-I in circulation is more useful than measuring total IGF-I with respect to evaluation of an association between IGF-I and breast cancer risk.

17 beta-estradiol-regulated expression of protein tyrosine phosphatase gamma gene in cultured human normal breast and breast cancer cells

BACKGROUND

Protein tyrosine phosphatase gamma (PTP gamma) has been implicated as a potential tumor suppressor gene in kidney and lung adenocarcinomas. We have previously shown that PTP gamma mRNA expression levels are lower in DES-induced kidney tumors than in normal kidneys of Syrian hamsters. The goals of the present study were to determine if PTP gamma mRNA is present in both normal and cancerous human breast cells, and to investigate the estrogenic regulation of PTP gamma mRNA expression in these cell types.

METHODS

Primary cultured human breast cells derived from surgical specimens of mammoplasty and breast cancer patients, as well as human breast cancer cell lines were used for the study. RT-PCR and RNase protection assay was utilized to detect and quantify levels of PTP gamma mRNA among the cell types used and between control and 17 beta-estradiol (E2)-treated cells. Transient transfection of human estrogen receptor (ER) into MDA-MB-231 human breast cancer cells was performed to establish the role of ER in the regulation of PTP gamma mRNA expression.

RESULTS

The results show that PTP gamma mRNA is expressed in primary cultured human breast cells isolated from mammoplasty and breast cancer patients, as well as in human cancer cell lines, and that E2 significantly inhibits PTP gamma expression in ER-positive human breast cancer cells via an ER-mediated mechanism. We show that PTP gamma mRNA levels are lower in human breast cancer cells than in normal human breast cells. Furthermore, we report that PTP gamma mRNA expression is inhibited by E2 in a dose-dependent manner in primary cultured breast cells. After treatment with 20 nM E2 for 24 hours, PTP gamma mRNA was significantly suppressed in primary cultured cancerous and non-cancerous cells from breast cancer patients, as well as in the ER-positive MCF-7 cell line by 50%, 85%, and 66%, respectively. In contrast, the PTP gamma mRNA expression levels did not change in similarly treated ER-negative MDA-MB-231 cells. Sensitivity to E2-induced suppression could be restored (94% inhibition) by transfecting MDA-MB-231 cells with an ER expression plasmid.

CONCLUSIONS

Our results are the first to suggest that PTP gamma is a potential estrogen-regulated tumor suppressor gene in human breast cancer which may play an important role in neoplastic processes of human breast epithelium.

Modulation of CD4 cell cytokine production by colon cancer-associated mucin

PURPOSE

Mucins have been implicated in tumor-associated immunosuppression. The possibility that colon cancer mucin (CCM) may modulate T-helper 1 (TH1) activity was evaluated by investigating its effect on the production of interleukin-2 (IL-2) by CD4+ cells, a process that requires antigen-specific and costimulatory signals.

METHODS

CCM was purified from human colorectal cancer cells by gel-exclusion fast-pressure liquid chromatography. Cytokine production of purified CD4+ cells was evaluated at the protein and gene level in the presence of a phorbol ester or an anti-CD3 monoclonal antibody (mAb) plus mAb against the CD28 costimulatory receptor to mimic two-signal activation.

RESULTS

Soluble CCM, which contains mucins MUC2 as well as MUC1, inhibited IL-2 mRNA expression and secretion of CD4+ stimulated with a phorbol ester or an anti-CD3 mAb plus anti-CD28 mAb. Pretreatment of CD4+ cells with anti-CD28 mAb abrogated the suppressive effects of CCM on IL-2 production, and flow cytometry showed decreased binding of anti-CD28 mAb to its receptor in the presence of mucin. In addition, Ca2+ mobilization after T cell receptor cross-linking with anti-CD3 mAb was maintained in the presence of CCM. Although interferon gamma production was also diminished, CCM did not induce a general inhibition of cytokine production, nor did it decrease cell viability. Macrophage inflammatory protein 1alpha production was up-regulated; the production of IL-10 and transforming growth factor beta was unchanged.

CONCLUSIONS

The results indicate that CCM can alter TH1 activity and suggest that the modulation of costimulatory interactions is involved. They provide another mechanism of immunosuppression mediated by these highly expressed tumor products.

Acute mixed lineage leukemia with an inv(8)(p11q13) resulting in fusion of the genes for MOZ and TIF2

Chromosomal abnormalities in acute leukemia have led to the discovery of many genes involved in normal hematopoiesis and in malignant transformation. We have identified the fusion partners in an inv(8)(p11q13) from a patient with acute mixed lineage leukemia. We show by fluorescence in situ hybridization (FISH) analysis, Southern blotting, and reverse transcriptase-polymerase chain reaction (RT-PCR) that the genes for MOZ, monocytic leukemia zinc finger protein, and TIF2, transcriptional intermediary factor 2, are involved in the inv(8)(p11q13). We demonstrate that the inversion creates a fusion between the 5' end of MOZ mRNA and the 3' end of TIF2 mRNA maintaining the translational frame of the protein. The predicted fusion protein contains the zinc finger domains, the nuclear localization domains, the histone acetyltransferase (HAT) domain, and a portion of the acidic domain of MOZ, coupled to the CREB-binding protein (CBP) interaction domain and the activation domains of TIF2. The breakpoint is distinct from the breakpoint in the t(8;16)(p11;p13) translocation in acute monocytic leukemia with erythrophagocytosis that fuses MOZ with CBP. The reciprocal TIF2-MOZ fusion gene is not expressed, perhaps as a result of a deletion near the chromosome 8 centromere. The MOZ-TIF2 fusion is one of a new family of chromosomal rearrangements that associate HAT activity, transcriptional coactivation, and acute leukemia.

Multiple phosphotyrosine phosphatase mRNAs are expressed in the human lung fibroblast cell line WI-38

Protein tyrosine phosphatases are important components of signal transduction pathways. The authors have used reverse transcription/polymerase chain reactions to accomplish a comprehensive examination of the RNA expression for 58 distinct mammalian protein tyrosine and dual specificity phosphatase (PTPase) and PTPase-like genes in the normal human diploid fibroblast cell line WI-38. Thirty-seven of these PTPase genes express easily measurable RNA, and four simultaneously express the RNA for two or more isoforms. Messages for an additional eight PTPase genes are detectable at low levels. Only 14 known PTPase genes do not express measurable RNA under our conditions. For purposes of comparison, the authors also assessed the PTPases expressed in the WI-38 cell line using highly degenerate primers to conserved motifs found in the classical tyrosine-specific PTPases. Only eight of the 22 classic tyrosine-specific PTPases detected using the specific primers were detected using these degenerate primers. Our panel of specific PTPase primers should be very useful for semiquantitatively assessing the repertoire of PTPases expressed by cells.

The expression of C-myb in human metastatic melanoma cell lines and specimens

The rapidly increasing incidence of malignant melanoma and lack of effective systemic therapy for advanced disease has given rise to the need for new approaches. The suggestion that c-myb may be an important gene in the control of melanoma proliferation prompted the exploration of its expression in several metastatic melanoma cell lines and specimens. Initial Northem hybridization showed undetectable expression of c-myb in the cell lines, although it was very strongly expressed in the K-562 cell line. Therefore, c-myb expression was examined utilizing primers and RT-PCR on the five melanoma cell lines and thirty-two metastatic melanoma specimens. There was very low expression in the two cell lines (UISO Mel-1 and 3) that were nontumorigenic, whereas there was a 10 fold increase in expression in the tumorigenic cell lines. In the metastatic specimens the expression varied by over 100 fold between the lowest and highest specimens. The expression of c-myb in tumor specimens was in general greater than matched normal specimens, save for skin which had moderate expression. In general, there did not appear to be any correlation between the clinical characteristics of the various specimens and the amount of c-myb expression. However, females with lymph node metastases had somewhat lower expression than males. The fact that significant melanoma specimens have altered expression of c-myb, coupled with the previous inhibition of melanoma growth by antisense c-myb, suggests that there may be a potential role for c-myb antisense therapy in the treatment of this tumor.

The protein tyrosine phosphatase DEP-1 is induced during differentiation and inhibits growth of breast cancer cells

Sodium butyrate-induced differentiation of breast cancer cell lines was used to identify protein tyrosine phosphatases (PTPs) involved in differentiation and growth inhibition of breast cancer cells. Of 42 PTPs analyzed, 31 were expressed in the ZR75-1 breast cancer cell line. Expression of four PTPs (DEP-1, SAP, PTP gamma, and PAC) was regulated in ZR75-1 cells undergoing differentiation. Expression of two of these PTPs (DEP-1 and SAP) was also regulated in the SKBr-3 cell line undergoing differentiation. In view of its marked induction with differentiation in an estrogen receptor (ER)-positive and an ER-negative breast cancer cell line, DEP-1 was investigated for a role in growth inhibition or induction of differentiation in breast cancer cells. A DEP-1 cDNA construct under control of a constitutively active cytomegalovirus promoter was transfected into the ZR75-1, SKBR-3, and MCF-7 breast cancer cell lines, and resistant colonies were selected with G418. DEP-1 expression inhibited the development of resistant colonies by 3-5-fold in all three lines compared to transfection with vector alone. Three stable MCF-7 cell lines expressing DEP-1 under control of an inducible metallothionein promoter were then established. In these lines, induction of DEP-1 expression inhibited breast cancer cell growth by 5-10-fold. These data describe PTPs expressed and regulated in breast cancer cell lines during differentiation and identify one PTP, DEP-1, that inhibits the growth of breast cancer cells in vitro.

Isotretinoin and recombinant interferon alfa-2a therapy of metastatic malignant melanoma

Twenty-five patients with metastatic malignant melanoma were treated with isotretinoin (13-cis-retinoic acid) orally at 1 mg/kg daily and recombinant interferon alfa-2a (INF-alpha) subcutaneously at 3 million units daily for 16-48 weeks. Therapy was well tolerated; fatigue and hyperlipidemia were the most frequent dose-limiting toxicity and necessitated dose reductions in 14 patients. Two patients achieved a complete response, and 3 responded partially for a total response rate of 20% (95% confidence interval: 4-36%). Responses occurred primarily in patients with limited tumor burden and disease confined to the skin and lymph nodes. Significant elevations in peripheral blood 2'-5'-oligoadenylate synthetase activity and natural killer activity were observed with therapy. The magnitude of these changes, however, was not predictive of response. Biopsy specimens of two responding lesions showed extensive necrosis of tumor. One specimen showed large aggregates of melanophages in association with tumor. The combination of isotretinoin and IFN-alpha is an active, easily administered regimen with acceptable toxicity for metastatic malignant melanoma.

B cell IL-7. Human B cell lines constitutively secrete IL-7 and express IL-7 receptors

IL-7 was originally reported as a cytokine produced by stromal cells which supports pre-B cell proliferation in vitro. To determine whether human B cells secrete IL-7 and express IL-7R we studied a wide panel of B cell lines (CLS). In Northern blot analysis we detected 2.4 kb IL-7 mRNA and by quantitative PCR we demonstrated IL-7 expression in 5 of 6 B CLS derived from patients with AIDS-associated Burkitt's lymphoma (AABCL), 3 of 3 CLS derived from patients with American Burkitt's lymphoma and 5 of 6 normal lymphoblastoid CLS. Only 1 of 5 African Burkitt's lymphoma CLS and 2 of 7 EBV- CLS expressed IL-7. A total of 484-bp amplicons was cloned and sequenced and found to correspond to the original IL-7 sequence. Constitutive IL-7 secretion was detected in 5 of 6 AABCL and in 6 of 7 normal lymphoblastoid CLS but in none of the 7 EBV- CLS. IL-7R expression was demonstrated in 8 of 26 CLS, none of which secreted IL-7. Our data suggest that 1) IL-7 mRNA is expressed in malignant B cell phenotypes, which correspond to a narrow window in the B cell differentiation pathway (pre-B, early B, intermediate B), as well as in normal lymphoblastoid B CLS. 2) IL-7 mRNA is expressed in both EBV+ and EBV- CLS, but only the EBV+ CLS secrete IL-7. 3) B cells activated by both EBV and HIV-1 (AABCL) secrete the greatest amount of IL-7. 4) IL-7 autocrine loops are not evident since IL-7R were detected on on CLS, which do not secrete IL-7. Our data provide the first direct evidence of IL-7 secretion by human cells and it is yet to be determined whether IL-7 is secreted by other cell types.

B cell IL-7. Human B cell lines constitutively secrete IL-7 and express IL-7 receptors

IL-7 was originally reported as a cytokine produced by stromal cells which supports pre-B cell proliferation in vitro. To determine whether human B cells secrete IL-7 and express IL-7R we studied a wide panel of B cell lines (CLS). In Northern blot analysis we detected 2.4 kb IL-7 mRNA and by quantitative PCR we demonstrated IL-7 expression in 5 of 6 B CLS derived from patients with AIDS-associated Burkitt's lymphoma (AABCL), 3 of 3 CLS derived from patients with American Burkitt's lymphoma and 5 of 6 normal lymphoblastoid CLS. Only 1 of 5 African Burkitt's lymphoma CLS and 2 of 7 EBV- CLS expressed IL-7. A total of 484-bp amplicons was cloned and sequenced and found to correspond to the original IL-7 sequence. Constitutive IL-7 secretion was detected in 5 of 6 AABCL and in 6 of 7 normal lymphoblastoid CLS but in none of the 7 EBV- CLS. IL-7R expression was demonstrated in 8 of 26 CLS, none of which secreted IL-7. Our data suggest that 1) IL-7 mRNA is expressed in malignant B cell phenotypes, which correspond to a narrow window in the B cell differentiation pathway (pre-B, early B, intermediate B), as well as in normal lymphoblastoid B CLS. 2) IL-7 mRNA is expressed in both EBV+ and EBV- CLS, but only the EBV+ CLS secrete IL-7. 3) B cells activated by both EBV and HIV-1 (AABCL) secrete the greatest amount of IL-7. 4) IL-7 autocrine loops are not evident since IL-7R were detected on on CLS, which do not secrete IL-7. Our data provide the first direct evidence of IL-7 secretion by human cells and it is yet to be determined whether IL-7 is secreted by other cell types.

Human B cell lines express the interferon gamma gene

Interferon gamma (IFN-gamma) production has been attributed exclusively to activated T cells and NK cells. We sought to determine whether human B cells express IFN-gamma. We studied 28 B cell lines including Epstein-Barr virus (EBV)+ normal lymphoblastoid B cell lines (N = 7), EBV+ B cell lines derived from patients with Burkitt's lymphoma with (N = 6) or without AIDS (N = 8), as well as seven EBV- B cell lines. All cell lines were studied by reverse transcription-polymerase chain reaction (RT-PCR). We detected constitutive expression of IFN-gamma in every B cell line. The tumor promoters PMA and teleocidin appeared to enhance this IFN-gamma expression in nearly every B cell line. The 517 bp amplicons spanning the entire protein coding region of the IFN-gamma mRNA from three representative lines were sequenced, definitively establishing that B cell IFN-gamma is identical to IFN-gamma from activated T cells and is not altered by derivation of the B cell lines from AIDS patients or by EBV status. Detection of IFN-gamma in the entire panel of EBV+ and EBV- cell lines suggests that the IFN-gamma gene is broadly expressed by human B cells. Our data imply that human B cells can be activated to produce IFN-gamma, further enmeshing B cells in the dynamics of immunoregulation.

Human B-cell interleukin-10: B-cell lines derived from patients with acquired immunodeficiency syndrome and Burkitt's lymphoma constitutively secrete large quantities of interleukin-10

A recent addition to the lymphokine network is human IL-10 (hIL-10). This novel lymphokine has striking homology to BCRF1 protein, the product of a previously uncharacterized open-reading frame in the Epstein-Barr virus (EBV) genome. To date, IL-10 expression has been described in several T clones induced with anti-CD3 and phorbol myristate acetate (PMA), in monocytes stimulated with lipopolysaccharide (LPS), and in murine B-cell lymphomas. We sought to determine whether human B cells express hIL-10 and, if so, its relationship to EBV and to other B-cell lymphokines. We studied 21 EBV-positive B-cell lines derived from patients with acquired immunodeficiency syndrome (AIDS) and Burkitt's lymphoma (n = 6), American Burkitt's (n = 3), African Burkitt's (n = 5), and normal lymphoblastoid cell lines (n = 7), in comparison with seven EBV-negative cell lines. All cell lines were activated with the tumor promoters PMA and teleocidin and were studied by Northern blot analysis, reverse transcription-polymerase chain reaction (RT-PCR), and enzyme-linked immunoadsorbent assay (ELISA). We demonstrated that EBV-positive cell lines derived from patients with American Burkitt's lymphoma, and especially those from patients with AIDS, constitutively express large quantities of hIL-10 by Northern blot analysis and ELISA (range, 3,101 to 25,915 pg/mL), and that both teleocidin and PMA induce hIL-10 in these cell lines. In contrast, six of seven EBV-negative cell lines did not express hIL-10 even by RT-PCR, and hIL-10 was not triggered by PMA or teleocidin. To assure that the 350 bp amplified by PCR was hIL-10 and not BCRF1, we used PCR primers, which do not amplify a fragment from plasmid templates containing BCRF1. Cloning and sequencing of the 350 bp product also demonstrated that B-cell IL-10 is identical to hIL-10 from the T-cell clone B21. Correlation of hIL-10 with other B-cell lymphokines secreted by these B-cell lines demonstrated that hIL-10 secretor cell lines also constitutively secrete or can be induced to secrete IL-6, although to a much lesser amount. Since both lymphokines influence B-cell growth and differentiation, we suggest that hIL-10 may contribute to the polyclonal B-cell activation and hyperglobulinemia seen in AIDS patients. Finally, several reports support the hypothesis that EBV is an important cofactor in the development of human immunodeficiency virus type 1 (HIV-1)-related B-cell lymphomas. Detection of large quantities of hIL-10 in B-cell lines derived from AIDS patients, the close association between EBV and hIL-10 shown in this report, and the ability of BCRF1 to capture hIL-10 activities, make hIL-10/BCRF1 an attractive candidate as a factor causing B-cell growth and immortalization in patients with AIDS and B-cell lymphomas.

Affinity labeling of a glutamyl peptide in the coenzyme binding site of NADP+-specific glutamate dehydrogenase of Salmonella typhimurium by 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate

NADP+-specific glutamate dehydrogenase from Salmonella typhimurium, cloned and expressed in Escherichia coli, has been purified to homogeneity. The nucleotide sequence of S. typhimurium gdhA was determined and the amino acid sequence derived. The nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A-2',5'-DP) reacts irreversibly with the enzyme to yield a partially inactive enzyme. After about 60% loss of activity, no further inactivation is observed. The rate of inactivation exhibits a nonlinear dependence on 2-BDB-T epsilon A-2',5'-DP concentration with kmax = 0.160 min-1 and KI = 300 microM. Reaction of 200 microM 2-BDB-T epsilon A-2',5'-DP with glutamate dehydrogenase for 120 min results in the incorporation of 0.94 mol of reagent/mol of enzyme subunit. The coenzymes, NADPH and NADP+, completely protect the enzyme against inactivation by the reagent and decrease the reagent incorporation from 0.94 to 0.5 mol of reagent/mol enzyme subunit, while the substrate alpha-ketoglutarate offers only partial protection. These results indicate that 2-BDB-T epsilon A-2',5'-DP functions as an affinity label of the coenzyme binding site and that specific reaction occurs at only about 0.5 sites/enzyme subunit or 3 sites/hexamer. Glutamate dehydrogenase modified with 200 microM 2-BDB-T epsilon A-2',5'-DP in the absence and presence of coenzyme was reduced with NaB3H4, carboxymethylated, and digested with trypsin. Labeled peptides were purified by high performance liquid chromatography and characterized by gas phase sequencing. Two peptides modified by the reagent were isolated and identified as follows: Phe-Cys(CM)-Gln-Ala-Leu-Met-Thr-Glu-Leu-Tyr-Arg and Leu-Cys(CM)-Glu-Ile-Lys. These two peptides were located within the derived amino acid sequence as residues 146-156 and 282-286. In the presence of NADPH, which completely prevents inactivation, only peptide 146-156 was labeled. This result indicates that modification of the pentapeptide causes loss of activity. Glutamate 284 in this peptide is the probable reaction target and is located within the coenzyme binding site.

Augmented nuclease activity during cellular senescence in vitro

The molecular correlates of the limited proliferative potential of normal human diploid fibroblasts and extensive single-strand breaks in the genomic DNA of these cells were examined by transfection analyses in which DNA replication could be uncoupled from DNA damage and repair. Both supercoiled (fmI), and restriction endonuclease-cleaved, linear (fmIII) molecules of a well-defined bacterial plasmid DNA, pBR322, were transfected into, and subsequently recovered from, early and late passage fibroblasts. Southern blot analysis revealed that fmI DNA was converted by random nicks into fmII DNA slightly more rapidly in late passage cells compared with cells at early passage. Similarly, fmII and fmIII DNAs also sustained multiple random nicks and no appreciable net religation of free ends of fmIII DNA could be detected at either passage. In addition, the efficiency of in vitro ligation of fmIII DNA recovered from late passage cells was also reduced, compared with that from early passage cells, as determined by Southern blotting. These data suggest that in the absence of DNA replication, a putative nuclease activity may contribute to DNA damage observed in senescent cells, which, in turn, may be causally related to their limited replicative potential.

In vivo voltammetry with electrodes that discriminate between dopamine and ascorbate

Untreated carbon-fiber voltammetric electrodes have been employed as chemical sensors of easily oxidized compounds in the brains of rats anesthetized with chloral hydrate. These electrodes can be used to distinguish dopamine from ascorbate and dihydroxyphenylacetate by the shape of the voltammograms. The electrodes are shown to provide a reproducible response to different neuronal stimuli. The rapid release of dopamine in the caudate nucleus can be measured following a local application of potassium chloride. Intraperitoneal injections of amphetamine also induce an increase of easily oxidized compounds; however, the voltammetry suggests that ascorbic acid, rather than dopamine, is the primary substance detected. Measurements in the cortex or in the caudate nucleus of animals lesioned by prior injection of 6-hydroxydopamine show that a substance with voltammetric properties identical to those of ascorbic acid also increases in concentration in these areas as a result of amphetamine administration.

Evaluation of amphetamine-induced in vivo electrochemical response

A carbon fiber microelectrode is shown to give a potential-dependent dopamine-selective response in rat brain tissue. However, distinct evidence for dopamine release is not obtained with intraperitoneal amphetamine administration (1.8 or 3.7 mg . kg-1). In rats which have been unilaterally depleted of dopamine, the change in electrochemical signal obtained in the lesioned striatum is very similar to that measured on the non-lesioned side following amphetamine administration. This indicates that substances other than dopamine contribute to the observed signals.