Role of the VEGFR3/VEGFD receptor axis in TGFbeta1 activation of primary prostate cell lines

BACKGROUND

Reports indicate that vascular endothelial growth factor receptor type 3 (VEGFR3) regulates cellular functions such as invasion, proliferation, and chemo-resistance. However, the exact function of the VEGFR3 signaling axis in prostate epithelial cells is poorly characterized.

METHODS

The goal of this study was to evaluate whether TGFbeta1 in combination with VEGFD can promote pre-malignant invasive activities of intermediate basal cells (IBC-10a) isolated from human prostate cancer (Gleason score 6).

RESULTS

hTERT immortalized IBC-10a cells normally grew as confluent "cobblestoned" monolayers, but treatment with TGFbeta1 (10 ng/ml for 2-6 hr) dissociated the cell-cell junctions and induced VEGFR3 translocation to the cell surface. This event was not inhibited by 10 microM cycloheximide or puromycin, indicating transcription and protein synthesis were not required. We further discovered that TGFbeta1 in combination with VEGFD induced a significant increase in the invasive activity of IBC-10a cells (>26% and 53% after 24 and 48 hr, respectively) in modified Boyden Chamber assays. TGFbetaRII receptor antibodies specifically blocked TGFbeta1 induction of VEGFR3 translocation to the cell surface and blocked VEGFD-induced invasion. Zymograms revealed that TGFbeta1 (and not VEGFR3) stimulated the secretion of MMP-2 and MMP-9, presumably to promote cell invasion. The cell invasion assays confirmed that antibodies specific for TGFbetaII receptor, MMP-2 and MMP-9 and VEGFR3, independently blocked TGFbeta1-induced invasion.

CONCLUSIONS

For the first time, we have demonstrated the mechanism by which TGFbeta1 stimulates VEGFD/VEGFR3 receptor axis activation leading to increased cell migration and invasion by primary intermediate basal cell cultures.

Dysplasia of human prostate CD133(hi) sub-population in NOD-SCIDS is blocked by c-myc anti-sense

BACKGROUND

The CD133(hi) sub-population of prostate epithelial cells has been demonstrated to possess tumor-initiating capacity consistent with that of the cancer stem cell theory. However, the involvement of oncogenes such as c-myc has not been fully elucidated in the CD133(hi) sub-population.

METHODS

We have isolated primary prostate cell strains (IBC-10a) and immortalized them by transfection with hTERT. The in vitro and in vivo tumorigenic capacity of isolated CD133(hi) and CD133(lo) cells was evaluated with respect to c-myc expression using specific sense and anti-sense oligonucleotides.

RESULTS

Freshly immortalized cells consisted of <3.3% CD133(hi)/CD24(hi) sub-population (SP). "Prostaspheres" generated from single CD133(hi) cells in the presence of EGF consisted of approximately 10% CD133(hi) SPs in 12-21 day cultures. A single Prostasphere generated from single CD133(hi) cells (6-10 cell stage at day 6 injected i.t.) produced dysplastic lesions in NOD-SCID mice (n = 4/5). Treatment of Prostaspheres from CD133(hi) SPs in vitro with c-myc or cyclin D1 anti-sense oligonucleotides totally blocked colony forming ability and growth. Furthermore, treatment of fully formed, 6-day Prostaspheres for 48 hr with c-myc anti-sense significantly reduced c-myc expression and their ability to generate lesions in NOD-SCIDs (n = 10 Prostaspheres injected i.t./mouse).

CONCLUSIONS

These data demonstrate for the first time that a single CD133(hi) cell is competent to generate Prostaspheres in vitro and that CD133(hi) Prostaspheres require c-myc to grow and form dysplastic lesions in vivo.

Identification of ABCA5 as a tissue and urine diagnostic marker for PIN

15508

Background: Bostwick and colleagues have suggested that prostatic intraepithelial neoplasia or PIN is the precursor of prostate cancer, and that a significant percentage of men with PIN develop prostate cancer (Sakr, 1994; Bostwick, 1995b; Arakawa, 1995; Qian, 1995; Qian, 1997). Currently there are no molecular diagnostic markers for PIN. Methods: Recently, we have developed ‘DNA-protein’ binding assays for the identification of novel transcriptional regulatory proteins associated with PIN glands. Electrophoretic mobility shift assays (EMSAs) with the 32P-labeled DNA probe was used for analysis of protein extracts from tissues and urine. Immunolabeling was carried out with rabbit antibodies specific for ABCA5. Results: Electrophoretic mobility assays (EMSAs) revealed that 1 DNA sequence (1 of 4,096 sequences screened) specifically bound a ∼160 Kda protein which was over-expressed in PIN and not found in BPH, SV or PCA glands (n=11). The gene encoding for the 160 Kda protein was cloned from a cDNA expression library by ‘in situ’ hybridization assays with the 32P-labeled DNA sequence. Sequencing revealed that the gene encoding for the 160 Kda protein was ABCA5, a member of the superfamily of ATP-binding cassette (ABC) transporters of multi-drug resistant genes. RT-PCR assays indicated the mRNA was over-expressed in PIN tissue, and was not present in BPH, or SV tissue. Rabbit polyclonal antibodies and immunolabeling showed that the antibodies specifically labeled the cell junctions of 3% glutaraldehyde fixed prostate cells. Immunohistochemistry indicated that ABCA5 was over expressed in foci of intermediate basal cells in normal glands, and in HGPIN. ABCA5 was faintly expressed in PCA glands. Enzyme linked immunoabsorbent assays (ELISAs) demonstrated in blinded studies that ABCA5 was a highly sensitive (>98% sensitivity) urine diagnostic marker for HGPIN in biopsy positive patients (n=107) at a cut off” of 25 ng/ml. ABCA5 was present at very low levels (i.e. <25 ng/ml) in the urine of patients diagnosed with BPH (n=79) or prostatitis or kidney and bladder cancer (>86% specificity). Conclusions: The data suggest that the expression of ABCA5 is over-expressed by PIN and may be a highly sensitive and specific urine diagnostic marker for detection of early stage prostate cancer.

No significant financial relationships to disclose.

Identification of ABCA5 as a tissue and urine diagnostic marker for prostatic intraepithelial epithelial or PIN

10089

Background: Bostwick and colleagues have suggested that prostatic intraepithelial neoplasia or PIN is the precursor of prostate cancer and that a significant percentage of men with PIN develop prostate cancer (Sakr, 1994; Bostwick, 1995b; Arakawa, 1995; Qian, 1995; Qian, 1997). Currently there are no diagnostic markers for PIN. Methods and Results: Recently, we have developed ‘DNA-protein’ binding assays for the identification of novel transcriptional regulatory proteins associated with PIN glands. Electrophoretic mobility assays (EMSAs) revealed that 1 (of 4096 sequences screened) DNA sequences specifically bound a 160 Kda protein over-expressed in PIN and not found in BPH, SV or PCA glands (n=11). The gene encoding for the 160 Kda protein was cloned from a lamda ZAP expression library by ‘in situ’ hybridization assays with the 32P labeled DNA sequence. Sequencing revealed that the gene encoding for the 160 Kda protein was ABCA5, a member of the superfamily of ATP-binding cassette (ABC) transporters of multi-drug resistant genes. RT-PCR assays indicated the mRNA was over-expressed in primary PIN cell cultures and by PIN tissue, but it was not present in BPH, or SV tissue. Rabbit polyclonal antibodies were raised against a n-terminal peptide (20 b) plus a c-terminal peptide (20b) and found to specifically label the cell junctions of 3% glutaraldehyde fixed cultured cells and to label putative adult cancer stem cells in sections of PIN tissue. ‘Blinded’ ELISA studies with urine specimens from biopsed patients showed that ABCA5 was over-expressed urine from patients with PIN (n=∼20), faintly expressed in PIN + PCA patients (n=8), and not expressed in BPH (n=10) or normal patients (n=20). Conclusions: The data suggest that the expression of ABCA5 is over-expressed by PIN and is a urine diagnostic marker for detection of the disease (>95% COI). Supported by NIH-NCI grant CA90397 to mes and by GTx.

[Table: see text]

A novel IL-10 signalling mechanism regulates TIMP-1 expression in human prostate tumour cells

We have previously reported that interleukin 10 (IL-10) signalling stimulated activation of a specific enhancer element, termed HTE-1, to promote tissue inhibitor of matrix metalloproteinase1 (TIMP-1) expression in human bone metastatic PC-3 subclone (PC-3 ML) cells. Recently, we have identified an IL-10 responsive signal molecule, termed IL-10E1, which binds the HTE-1 element and cloned the gene encoding for the 22 kDa protein. In this paper, we have examined the mechanism of IL-10/IL-10 receptor signalling in two distinct human prostate cell lines, a 'normal' prostate epithelial cell line, termed NPTX-1532 and highly metastatic PC-3 ML tumour cells. Signalling cascade studies revealed that IL-10 stimulated tyrosine phosphorylation of JAK1 and TYK2 receptor kinases and tyrosine phosphorylation of IL-10E1. Phosphorylation, triggered IL-10E1's rapid translocation to the nucleus by 10-30 min. Deletion analysis combined with transient transfection experiments revealed that the n-terminal domain (approximately 74 a.a.) of the IL-10E1 protein, the nt-nls peptide, was stimulated by IL-10 to translocate to the nucleus and induce TIMP-1 expression. Site-directed mutagenesis further showed that phosphorylation of two tyrosine moieties (Y57 and Y62) of the nt-nls peptide was required for IL-10 activation of signalling and TIMP-1 expression. The data demonstrate, for the first time, that IL-10 receptor signalling of TIMP-1 expression is regulated by tyrosine phosphorylation of a novel gene, IL-10E1, in human prostate cells.

Selective estrogen receptor modulators. An aid in unraveling the links between estrogen and breast cancer

Breast cancer is a classic hormone-dependent malignant disease that is influenced by estrogen. However, the molecular links between estrogen and cell proliferation in healthy and malignant breast tissue are complex and as yet not well understood. The selective estrogen receptor modulators (SERMs), which are competitive inhibitors of estrogen binding at estrogen receptors alpha and beta, have become important weapons in the prevention and treatment of breast cancer. These agents also offer opportunities for the elucidation of the multiple molecular mechanisms by which estrogen affects cell proliferation. Each SERM-estrogen receptor complex has a unique structure that influences its activity in different body tissues. Unraveling the links between SERM structure and function not only may shed light on the signaling pathways that connect estrogen to cell proliferation but also may allow the design of new agents specifically targeted to affect certain events along these pathways.

Significance of cysteine rich transcription factor (CRTF) in the synthesis of tissue inhibitor of metalloproteinases 1 (TIMP-1) in gastrointestinal cancers

We previously reported that a novel promoter enhancer element "human tissue inhibitors of metalloproteinases 1 (TIMP-1) enhancer" (HTE) and a novel transacting protein "cysteine rich transcription factor" (CRTF) induced TIMP-1 synthesis in prostate cancer cells 2xN.I.PC-3. In the present study, to clarify the significance of CRTF in gastrointestinal cancers we measured the binding activity of CRTF to HTE using an electrophoretic mobility shift assay (EMSA), and the TIMP-1 concentration by ELISA after various stimulation of six cancer cell lines (KE-3, TE-9, MKN-28, MKN-45, KM12SM, SW620). In three cell lines (KE-3, MKN-45, SW620), both the binding activity of CRTF and TIMP-1 concentration significantly increased after IL-10 stimulation. Fetal bovine serum (FBS) did not affect the binding activity of CRTF, whereas FBS induced TIMP-1 synthesis in all cell lines. In KE-3 esophageal cancer cells and SW620 colon cancer cells, both the binding activity of CRTF and TIMP-1 concentration increased in the presence of a conditioned medium (CM) of fibroblasts which was isolated from human colon cancer tissues, but did not increase in MKN-45 cells. Moreover, in the fibroblasts, both the binding activity of CRTF and the TIMP-1 concentration increased in the presence of CM from KM12SM, SW620, and TE-9 cancer cell lines. These results suggested that IL-I0, and unknown factors in addition to IL-10, induced TIMP-1 synthesis via an increase in the binding activity of CRTF in gastrointestinal cancers, and that interaction between cancer cells and fibroblasts may play an important role in TIMP-1 synthesis through a signal transduction pathway consisting of CRTF phosphorylation and HTE activation.

Upregulation of vascular endothelial growth factor by cobalt chloride-simulated hypoxia is mediated by persistent induction of cyclooxygenase-2 in a metastatic human prostate cancer cell line

Upregulation of vascular endothelial growth factor (VEGF) expression induced by hypoxia is crucial event leading to neovascularization. Cyclooxygenase-2, an inducible enzyme that catalyzes the formation of prostaglandins (PGs) from arachidonic acid, has been demonstrated to be induced by hypoxia and play role in angiogenesis and metastasis. To investigate the potential effect of COX-2 on hypoxia-induced VEGF expression in prostate cancer. We examined the relationship between COX-2 expression and VEGF induction in response to cobalt chloride (CoCl2)-simulated hypoxia in three human prostate cancer cell lines with differing biological phenotypes. Northern blotting and ELISA revealed that all three tested cell lines constitutively expressed VEGF mRNA, and secreted VEGF protein to different degrees (LNCaP > PC-3 > PC3ML). However, these cell lines differed in the ability to produce VEGF in the presence of CoCl2-simulated hypoxia. CoCl2 treatment resulted in 40% and 75% increases in VEGF mRNA, and 50% and 95% in protein secretion by LNCaP and PC-3 cell lines, respectively. In contrast, PC-3ML cell line, a PC-3 subline with highly invasive, metastatic phenotype, exhibits a dramatic upregulation of VEGF, 5.6-fold in mRNA and 6.3-fold in protein secretion after treatment with CoCl2. The upregulation of VEGF in PC-3ML cells is accompanied by a persistent induction of COX-2 mRNA (6.5-fold) and protein (5-fold). Whereas COX-2 expression is only transiently induced in PC-3 cells and not affected by CoCl2 in LNCaP cells. Moreover, the increases in VEGF mRNA and protein secretion induced by CoCl2 in PC-3ML cells were significantly suppressed following exposure to NS398, a selective COX-2 inhibitor. Finally, the effect of COX-2 inhibition on CoCl2-induced VEGF production was reversed by the treatment with exogenous PGE2. Our data demonstrate that VEGF induction by cobalt chloride-simulated hypoxia is maintained by a concomitant, persistent induction of COX-2 expression and sustained elevation of PGE2 synthesis in a human metastatic prostate cancer cell line, and suggest that COX-2 activity, reflected by PGE2 production, is involved in hypoxia-induced VEGF expression, and thus, modulates prostatic tumor angiogenesis.

Increased cellularity of tumor-encased native vessels in prostate carcinoma is a marker for tumor progression

Changes in the native vasculature of the prostate gland associated with prostate adenocarcinoma have not been well characterized. Eighty-nine whole mounts of entirely submitted radical prostatectomies were reviewed. Thirty prostates with a minimum of five native arteries surrounded by carcinoma with corresponding control arteries were found and included in this study. The number of nuclei in the media of native arteries was recorded per 0.138 mm2 using a 40x objective. The number of nuclei in vessels embedded in carcinoma (n = 204) was increased when compared with controls (26.37 versus 20.58 mean nuclei per 0.138 mm2; P < .001). Pathologic Stage T3 carcinomas contained vessels that were more cellular than stage T2 (P < .001). Vessels embedded in Gleason Grade 4 showed more cellularity than arteries embedded in Gleason Grade 3 (P < .002). Increased media cellularity of native prostate vessels encased in carcinoma is a histologic feature of higher grade/stage prostate carcinoma and provides positive indicator of advanced prostate cancer.

Growth of HPV-18 immortalized human prostatic intraepithelial neoplasia cell lines. Influence of IL-10, follistatin, activin-A, and DHT

Cultures from high grade prostatic intraepithelial neoplasia (HGPIN) have been established and immortalized by HPV-18 infection. The cultures were identified as PIN by Western blotting with anti-cytokeratin (34betaE12) and prostate specific antigen (PSA) antibodies. We examined the growth capabilities of the cultures in the presence of TGF-beta1, activin-A, follistatin (FS), androgens (DHEA, DHT) and several cytokines (IL-10, IL-2, IL-4). IL-10, FS, and DHT stimulated cell proliferation and colony forming ability, while the other cytokines and growth factors had no discernable effect. In addition, DHT and to a lesser extent IL-10 both stimulated PSA production. Activin-A blocked IL-10, FS, and DHT stimulated growth and PSA production. We interpret the data to mean that IL-10 induction of FS secretion (and FS binding of activin A) restores the normal growth capabilities of HGPIN cultures.

Role of interleukin 10 and transforming growth factor beta1 in the angiogenesis and metastasis of human prostate primary tumor lines from orthotopic implants in severe combined immunodeficiency mice

Transfection of primary human prostate tumor cells (i.e., HPCA-10a, 10b, 10c, and 10d lines) with the transforming growth factor (TGF)-beta1 gene stimulated anchorage-independent growth and promoted tumor growth, angiogenesis, and metastasis after orthotopic implantation in severe combined immunodeficiency mice. In contrast, interleukin (IL)-10 transfected cells or cells cotransfected with these two genes exhibited reduced growth rates and significantly reduced angiogenesis and metastasis after 8, 12, and 16 weeks. Enzyme-linked immunosandwich assays confirmed that the respective tumors expressed elevated levels of TGF-beta1 and IL-10 in vivo. ELISAs further showed that TGF-beta1 expression induced matrix metalloproteinases-2 (MMP-2) expression, whereas IL-10 down-regulated MMP-2 expression while up regulating TIMP-1 in the transfected cells. Also, tumor factor VIII levels correlated with TGF-beta1 and MMP-2 expression and inversely with IL-10 and TIMP-1 levels. More importantly, mouse survival was zero after 4-6 months in mice bearing TGF-beta1- and MMP-2-expressing tumors and increased significantly in mice implanted with IL-10- and TIMP-1-expressing tumors (i.e., to >80% survival). Analysis of the metastatic lesions showed that they expressed TGF-beta1 and MMP-2 but barely detectable levels of IL-10 or TIMP-1, suggesting that IL-10 and TIMP-1 might normally block tumor growth, angiogenesis, and metastasis.

Interleukin 10 (IL-10) inhibition of primary human prostate cell-induced angiogenesis: IL-10 stimulation of tissue inhibitor of metalloproteinase-1 and inhibition of matrix metalloproteinase (MMP)-2/MMP-9 secretion

In in vitro angiogenesis assays, aggregates of human papilloma virus (HPV)-18-immortalized primary human prostate cancer cells (HPCA-5aHPV-18 or HPCA-10aHPV-18 cells) induced human bone marrow endothelial cells (HBMCE-1 cells) to form microvessels in three-dimensional collagen I gels after 1-2 days incubation at 37 degrees C. The microvessels aligned perpendicular to the tumor aggregates and abutted on the edges of the aggregates. The number and length of the microvessels increased significantly from day 1 to 2 (i.e., by approximately 30%). ELISAs showed that the HPCA-5aHPV-18 cells normally secreted low levels of tissue inhibitor of metalloproteinase (TIMP)-2, matrix metalloproteinase (MMP)-2, and MMP-9 but relatively high levels of TIMP-1. In contrast, HPCA-10aHPV-18 cells secreted high levels of MMP-2 and MMP-9 (>40 pg/microg protein) but low levels of TIMP-1 and TIMP-2 (<5 pg/microg protein). Interleukin 10 (IL-10) (15 ng/ml) induced TIMP-1 production (>15 pg/microg protein) but reduced MMP-2 and MMP-9 secretion (<5 pg/microg protein) by the HPCA-5aHPV-18 and HPCA-10aHPV-18 cells. IL-10 (15 ng/ml) and MMP-9/MMP-2 antibodies all blocked induction of microvessel formation in the coculture experiments. In contrast, IL-10 receptor antibodies and TIMP-1 antibodies countered IL-10's effects and promoted angiogenesis. The data demonstrated that IL-10 stimulation of TIMP-1 and inhibition of MMP-2 and MMP-9 secretion by prostate tumor cells can control induction of angiogenesis in vitro.

Alendronate blocks metalloproteinase secretion and bone collagen I release by PC-3 ML cells in SCID mice

We have previously shown that alendronate, a potent bisphosphonate compound, can prevent human PC-3 ML tumor cell metastasis to the bone (Stearns and Stearns, 1996, Oncol Res, 8, 69-75). In this paper, tumor cells were injected into the bone medullary cavity of SCID mice femurs both in vivo and following isolation in vitro. ELISAs showed that the amount of collagen I released in the bone marrow (i.e. in in vitro experiments) and the blood plasma (i.e. in in vivo experiments) was a function of the time of incubation or the number of cells injected in the femurs. ELISAs also showed that the levels of matrix metalloproteinase (MMP-2 and MMP-9) secreted in the bone medullary cavity of the femurs directly correlated with the extent of collagen 1 release. In vitro experiments carried out with 'live' and 'devitalized bone' yielded similar results suggesting that the tumor cells (not the osteoclasts) were primarily responsible for the bone solubilization observed. Alendronate pretreatment of the SCID mice (0.1 mg/kg biweekly for 3 weeks) (or the tumor cells) blocked both MMP production by the tumor cells (and the osteoclasts) and collagen I release, providing direct evidence that alendronate might be utilized to prevent bone destruction by metastatic tumor cells. Zymography indicated that MMP-2 activation might be responsible for bone solubilization. In addition, the data suggest that the plasma levels of collagen I might be a marker of bone metastasis and osteolysis.

Identification of positive and negative regulator elements for the tissue inhibitor of metalloproteinase 1 gene

We have identified an IL-10 inducible enhancer (HTE) (5'-CACGATGACTCATCACTGTTGAAAGACA-3') (-864 to -836 bp) and associated silencer element (HTS) (5'-CCACTGGCCCATCGTATAT-3') (-1284 to -1266 bp) in the 5' promoter region of the human tissue inhibitor of metalloproteinase-1 (TIMP-1) gene. Chloramphenicol acetyl transferase (CAT), electrophoretic migration shift assays (EMSAs), and DNase footprinting revealed that IL-10 (15 ng/ml for 1-2 h) induced the HTE enhancer. In comparison, phorbol ester stimulated the HTS silencer and blocked IL-10's effects in a dose-dependent, orientation- and position-independent fashion, suggesting that HTS is a true silencer element. EMSAs combined with deletion and mutation analysis of the HTE and HTS elements confirmed these observations. Finally, Northern blot, Western blot, immunoprecipitation, and ELISA analysis showed that IL-10 (15 ng/ml) induced TIMP-1 expression (approximately 10-fold by 18 h), whereas PMA (100 ng/ml) inhibited the stimulatory effects of IL-10 on TIMP-1 expression. The data indicate that HTE and HTS function as positive and negative regulatory elements that control human TIMP-1 expression.

Antimestatic and antitumor activities of interleukin 10 in transfected human prostate PC-3 ML clones: Orthotopic growth in severe combined immunodeficient mice

We have permanently transfected human prostate PC-3 ML tumor cells and examined the influence of interleukin 10 (IL-10) production on tumor growth and metastasis following orthotopic implantation in the prostate gland of severe combined immunodeficient mice. Measurements of tumor volume after 5, 8, and 12 weeks indicated that tumor volume was negatively correlated with the amount of IL-10 production. Likewise, the extent of metastasis was inversely related to the amount of IL-10 produced. Following i.v. injection, the IL-10-expressing clones also failed to metastasize to the bone marrow. Controls showed that PC-3 ML and PC-3 ML mock clones grew rapidly and metastasized when implanted orthotopically or injected i.v. via the tail vein. Mouse survival curves showed that all of the mice injected orthotopically with the PC-3 ML clones died by about 14-16 weeks, whereas the PC-3 ML-IL10a or PC-3 ML-ILl0b clones induced only 10-20% death after 23-24 weeks. Likewise, survival studies showed a high death rate by approximately 30 days with PC-3 ML mock cells but <10% death by 12 weeks with the IL-10-transfected clones injected i.v. via the tail vein. The data strongly suggest that IL-10 production blocks tumor growth and metastasis in severe combined immunodeficient mice.

Specific transcription factors prognostic for prostate cancer progression

We have previously identified (M. Wang et al., Oncol. Res., in press, 1998) an enhancer element [human tissue inhibitor of metalloproteinase-1 enhancer-1 (HTE)] for the human tissue inhibitor of metalloproteinase-1 promoter that binds a novel zinc finger, cysteine-rich transcription factor (CRTF). In this study, we have used electrophoretic mobility shift assays to examine the relative level of expression of CRTF, jun/fos, and IFN-gamma responsive signal transducer activators of transcription (STATs) that bind specific HTE, activator protein, and IFN-gamma (Fcy and interferon regulatory factor) response motifs in tumor lines and human prostate tissue [i.e., normal (n = 3); benign prostatic hyperplasia (BPH; n = 12); high grade prostate intraepithelial neoplasia (PIN; n = 10); and prostate cancer adenocarcinoma (PCA; n = 61) plus seminal vesicle (n = 10) tissues]. The data showed that CRTF was overexpressed in PCA (Gleason's score, 10>8>6>5>4) compared with BPH, PIN, seminal vesicle, and normal tissues. To a much lesser degree, jun/fos and STAT 1 were also elevated in PCA compared to BPH, PIN, and normal tissues. In addition, blinded studies showed that CRTF and jun/fos were present at low levels in organ-confined specimens but at significantly elevated levels (P < 0.001) in samples exhibiting capsular penetration and localized spread, which indicated that CRTF and perhaps jun/fos were markers for cancer progression.

Alendronate blocks TGF-beta1 stimulated collagen 1 degradation by human prostate PC-3 ML cells

We have previously shown that alendronate can prevent human PC-3 ML tumor cell metastasis to the bone (Wang and Stearns, 1991, Differentiation, 48, 115-25). In this paper, ELISAs and Western blots showed that TGF-beta1 stimulated the secretion of a 72 kDa matrix metalloproteinase 2 (MMP-2) to enhance the solubilization of radiolabeled collagen 1 by metastatic human prostate PC-3 ML cells. A potent bisphosphonate compound, alendronate, inhibited MMP-2 secretion to block solubilization of collagen 1. Alendronate failed to inhibit MMP-2 activity directly, but instead appeared to block cellular secretion of MMP-2. Alendronate failed to inhibit secretion of tissue inhibitor of metalloproteinase-2 (TIMP-2; the inhibitor of MMP-2) and the decrease in collagen 1 solubilization observed may occur, in part, from changes in the molar stoichiometry of TIMP-2 to MMP-2. We conclude that alendronate may be a potent inhibitor of bone resorption based on its ability to block MMP-2 secretion by tumor cells.

IL-10 inhibition of human prostate PC-3 ML cell metastases in SCID mice: IL-10 stimulation of TIMP-1 and inhibition of MMP-2/MMP-9 expression

The molecular mechanism by which IL-10 inhibits metastases was examined using a SCID mouse model. Human PC-3 ML subclones normally metastasize to the lumbar vertebrae (approximately 70% mice injected, n = 14/20) following intravenous injection in severe combined immunodeficient (SCID) mice. IL-10 treatment of the PC-3 ML cells (15 ng/ml for 36 h) and the SCID mice (0.03 mg/kg/day for 30 days) reduced the number of metastases to 5% of the mice (n = 1/20). More importantly, following discontinuation of IL-10 treatment on day 30, the mice remained tumor-free and mouse survival rates increased dramatically (from < 30% in untreated mice) to about 85% in IL-10-treated mice. IL-10 did not appear to alter the growth rates or colony-forming ability of the PC-3 ML cells in vitro. Likewise, the growth of subcutaneous tumors and established bone marrow metastases was not inhibited by IL-10 treatment of the SCID mice. However IL-10 may inhibit the production of matrix metalloproteases (MMP) and prevent the establishment of metastasis. We therefore examined the influence of IL-10 on PC-3 ML production of MMP-2/MMP-9 and the tissue inhibitors of metalloproteinases (TIMP-1/2). Enzyme-linked immunosandwich assays (ELISAs) revealed that IL-10 (15 ng/ml for 36 h) treatment of the PC-3 ML cells down-regulated MMP-2 and MMP-9 while up-regulating TIMP-1 (not TIMP-2) expression. Likewise, IL-10-treated mice exhibited similar changes in TIMP-1 and MMP-2/MMP-9 expression. The IL-10 effects were blocked by IL-10 receptor antibodies. In comparison to IL-10, IL-4 failed to influence metastasis or the expression of TIMP-1, TIMP-2, MMP-2 and MMP-9 by PC-3 ML cells. We suggest that IL-10-regulated increases in the molar ratio of TIMP-1/MMP-9 and TIMP-2/MMP-2 might inhibit processes critical to the establishment of bone marrow metastasis.

In situ hybridization studies of metalloproteinases 2 and 9 and TIMP-1 and TIMP-2 expression in human prostate cancer

The expression of MMP-2, MMP-9, TIMP-1, TIMP-2, and the urokinase receptor were examined in fetal and normal prostate tissues, benign prostatic hyperplasia and prostate cancer (n = 117). In situ hybridization with digoxigenin-labeled oligonucleotide probes demonstrated that TIMP-1 and TIMP-2 were expressed at elevated levels in the stroma of Gleason sum 5 tissues, whereas MMP-2 and MMP-9 were expressed at relatively low levels. In higher Gleason sum tissues (GS 8-10), TIMP-1 and TIMP-2 were not expressed, whereas MMP-2 and MMP-9 were intensely expressed. Furthermore, TIMP-1 and TIMP-2 expression was high in organ-confined specimens (OC, n = 43), somewhat lower in specimens with capsular penetration (CP, n = 29), and low or negative in samples with surgical margin/seminal vesicle (M/SV, n = 17) and lymph node (LN, n = 13) involvement. In contrast, MMP-2 and MMP-9 expression was low in the OC tissues; and noticeably higher in CP, M/SV, and LN specimens. Finally, correlation of TIMP and MMP expression with GS and pathological stage versus cure rate further revealed that a high percentage of organ-confined, GS 5 specimens expressing TIMP and little MMP were cured. In comparison, few of the GS 7-10 patients with capsular penetration and expressing MMP and little TIMP were cured. The data suggest that TIMP-1 (and TIMP-2) and MMP-2 (and MMP-9) are independent predictors of outcome.

Platelet-derived growth factor A and B chains and the alpha and beta receptors in prostatic intraepithelial neoplasia

BACKGROUND

The objective of this study was to evaluate the expression of platelet-derived growth factor (PDGF A, PDGF B) and their receptors (PDGF alpha, PDGF beta) in prostatic intraepithelial neoplasia (PIN) and adenocarcinoma.

METHODS

Peroxidase-antiperoxidase immunoperoxidase labeling was used to detect the extent of antibody labeling in 29 different high grade PIN specimens.

RESULTS

PDGF A and PDGF alpha were uniformly expressed in glandular epithelial and stromal cells, whereas PDGF B was not expressed by either tissue. However, PDGF beta was lightly expressed in a uniform manner by both the glandular epithelial and stromal cells.

CONCLUSIONS

The data suggest that an autocrine loop may exist in which the epithelial cells of high-grade PIN express PDGF AA and PDGF alpha to modulate growth of precancerous lesions.

In situ hybridization studies of alpha 2-macroglobulin receptor and receptor-associated protein in human prostate carcinoma

We have utilized in situ hybridization and immunocytochemistry techniques to examine the expression of both alpha 2-macroglobulin (alpha 2-MR) and the 39 kDa receptor-associated protein (RAP) in 8 benign (BPH) and 34 malignant human prostate tissues, including 4 metastases. The levels of alpha 2-MR mRNA expression (but not RAP) increased significantly in high Gleason score carcinomas ( > 8) and in metastatic lesions, suggesting that alpha 2-MR expression is associated with advanced cancer. Semi-quantitative analysis with computer-assisted system analysis (CASA) confirmed this interpretation. This is the first report of alpha 2-MR expression being associated with advanced prostate cancer.

Effects of alendronate and taxol on PC-3 ML cell bone metastases in SCID mice

The combined influence of alendronate, a bisphosphonate compound, and taxol on the establishment and growth of human PC-3 ML subclones injected intravenously via the tail vein in SCID mice was investigated. The pretreatment of SCID mice with alendronate (0.04-0.1 mg/kg twice weekly or 0.1 mg/kg weekly) partially blocked the establishment of bone metastases by human PC-3 ML cells and resulted in tumor formation in the peritoneum and other soft tissues. However, alendronate pretreatment of mice (0.1 mg/kg twice weekly or weekly) and dosing along with taxol (10-50 mg/kg/day, twice weekly, or weekly) blocked the growth of PC-3 ML tumors in the bone marrow and soft tissues in a statistically significant manner and improved survival rates significantly (p < 0.001) by 4-5 weeks. ELISAs and zymography of matrix metalloproteinase production in vitro and in vivo showed that alendronate and taxol alone partially inhibited metalloproteinase production, but that taxol in combination with alendronate totally blocked protease production and release. The combined activities of alendronate and taxol appeared to inhibit the establishment and growth of tumors in SCID mice, perhaps, in part, as a result of inhibition of protease production and release.

Keratinocyte growth factor and receptor mRNA expression in benign and malignant human prostate

We have examined whether keratinocyte growth factor (KGF) and its receptor are expressed in normal, fetal, and prostate cancer cells since KGF may play a role in the growth of adenocarcinomas. In situ hybridization studies with digoxigenin-labeled oligonucleotides (anti-sense and sense controls) were employed to examine KGF and KGF receptor mRNA expression in prostate cancer. We found that the KGF and KGF receptor genes were faintly expressed in the stromal and epithelial cells, respectively, in both fetal (n = 6) and normal adult prostate (n = 6) tissues examined. In 10 benign prostatic hyperplasias (BPH), and in low- and high-grade prostatic carcinoma (32 total), both the KGF gene and the receptor mRNA were expressed in the glandular epithelial cells. KGF was also expressed by the stromal cells in BPH and low-grade carcinoma. Computer assisted system analysis indicated that the intensity of epithelial labeling by both probes was increased in high Gleason score carcinomas ( > 8) and in metastatic nodules. We interpret the data to mean that the paracrine loop in normal prostate may be replaced by an autocrine loop in BPH and adenocarcinomas.

Immunohistochemistry analysis of platelet-derived growth factor A and B chains and platelet-derived growth factor alpha and beta receptor expression in benign prostatic hyperplasias and Gleason-graded human prostate adenocarcinomas

The purpose of this study was to determine whether changes in the expression of platelet-derived growth factor (PDGF) and its receptors were associated with prostate cancer. Peroxidase-anti-peroxidase-immunoperoxidase labeling was used to detect the A and B chains and alpha and beta receptors of PDGF in 5 benign prostatic hyperplasias and 13 human prostate adenocarcinomas (Gleason grades 2 to 9). In all 5 benign prostatic hyperplasias, none of the PDGF antibodies (even at high titers, 1:50 dilutions) labeled the epithelial or the stromal cells. In adenocarcinomas, the A chain and alpha receptor antibodies labeled both epithelial and stromal cells. The intensity of the staining was relatively high in low Gleason grade (<6) and low in high Gleason grade (>7) tissue; however, the B chain and beta receptor antibodies failed to label either epithelial or stromal cells in any of the 13 adenocarcinomas. The data suggest that PDGF A and alpha receptor genes may be preferentially turned on in epithelial and stromal prostate tumor cells.

Identification of the receptor for a novel M(r) 78,000 "invasion stimulating factor" from metastatic human prostatic PC-3 ML clones

A M(r) 78,000 protein (reduced), termed invasion stimulating factor (ISF), was purified from the conditioned medium of a bone metastasizing human prostatic PC-3 ML clone (M. E. Stearns and M. Stearns. Cancer Metastasis Rev., 12: 39-52, 1993). Scatchard analysis and affinity cross-linking studies revealed that the producer PC-3 ML cells expressed a receptor binding site (M(r) approximately 115,000). We found a Kd approximately 425 pM and about 22,000 sites/cell. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis autoradiograms confirmed that the PC-3 ML cells expressed the receptor, whereas the ISF non-producing, noninvasive PC-3 clones (i.e., 3-4 x N.I. PC-3 cells) failed to express the ISF receptor. We conclude that a unique ISF autocrine loop characterizes the bone metastatic PC-3 ML cells.

Liarozole and 13-cis-retinoic acid anti-prostatic tumor activity

Liarozole fumarate (R85,246), a novel benzimidazole derivative, reduced s.c. and bone metastasis tumor growth by the androgen-independent PC-3ML-B2 human prostatic carcinoma clone in SCID mice. The drug inhibited cell invasion of Matrigel in Boyden chamber chemotactic assays and the secretion of type IV collagenase. In vitro, liarozole failed to inhibit cell proliferation and cell attachment to various substrates (Matrigel, laminin, type IV collagen, and fibronectin). In vivo, the drug also blocked type IV collagenase production in established s.c. tumors. Liarozole has been postulated by others (R. De Coster, W. Wouters, R. Van Ginckel, D. End, et al. J. Steroid Biochem. Mol. Biol., 43: 197-201, 1992) to inhibit retinoic acid catabolism. Our data indicate that liarozole treatment can increase the tumor retinoic acid levels in vivo. Studies of retinoic acid revealed that the drug independently reduced tumor growth in vivo and inhibited cell invasion of Matrigel and the secretion of collagenase IV. Surprisingly, liarozole and retinoic acid failed to exhibit measurable synergistic activity both in vitro and in vivo. Taken together these data suggest that liarozole might inhibit retinoic acid catabolism in vivo and consequently have significant therapeutic value as an anti-prostatic tumor agent.

Autocrine factors, type IV collagenase secretion and prostatic cancer cell invasion

Motility factors play a major role in tumor cell invasion and metastases. The biochemical properties of various motility factors; the receptor mediated mechanism of action; the role of microtubules; the potential influence of oncogenes; and the influence of motility factors on type IV collagenase secretion and invasion are discussed. We report on expression of a 70 kDa motility factor, termed invasion stimulating factor (ISF), in human prostatic PC-3 sublines. Boyden chamber chemotactic assays and measurements of type IV collagenase synthesis and secretion suggest that an ISF-receptor dependent mechanism influences tumor cell invasion and protease secretion. Taken together, the evidence that autocrine motility factors play an essential role in tumor cell invasion and metastases is compelling.

Type IV collagenase (M(r) 72,000) expression in human prostate: benign and malignant tissue

The expression of type IV collagenase (M(r) 72,000) has been examined in tissues from patients with benign prostatic hyperplasia (6 patients) and varying Gleason grades of malignant prostate cancer (18 patients). Immunoperoxidase labeling indicated that expression of the type IV collagenase was weak or nonexistent in benign tissue but consistently strong in the glandular and ductal epithelial cells of prostate tumors diagnosed at Gleason grades 1-8. In moderate to advanced cancer (i.e., Gleason grades 2 to 8), invasive tumor foci in the stromal tissue produced relatively modest amounts of type IV collagenase. The normal stromal tissue (i.e., fibroblasts) uniformly failed to produce detectable levels of type IV collagenase in the 24 patients examined. Northern and quantitative slot blot hybridization assays demonstrated that collagenase type IV mRNA levels were low in benign tissue and high in malignant tumors. In contrast, the stromal cells did not express significant amounts of type IV collagenase mRNA. Enzyme-linked immunosorbent assays demonstrated that the amounts of type IV collagenase protein correlated directly with the mRNA levels in the tumor tissue. The studies suggest that type IV collagenase may be selectively overexpressed by malignant, preinvasive prostatic epithelial cells.

Taxol blocks processes essential for prostate tumor cell (PC-3 ML) invasion and metastases

We have examined the antimetastatic effects of taxol on a PC-3 human prostatic tumor variant (PC-3 ML) which metastasizes to the lumbar vertebrae in severe combined immunodeficiency-carrying (SCID) mice. Immunofluorescence labeling indicated that taxol (0.5 to 1.0 microM for 6 h) produced an abnormal bundling of microtubules in a dosage-dependent manner. Slot blotting and gelatinase assays revealed that taxol inhibited secretion of the M(r) 72,000 and M(r) 92,000 type IV collagenases plus a M(r) 57,000 gelatinase. Radioimmunoprecipitation measurements confirmed that the drug inhibited both the secretion and the synthesis of the M(r) 72,000 collagenase. Taxol also blocked total protein secretion but did not influence total protein synthesis or turnover. Boyden chamber chemotactic studies further showed that taxol (0.5 to 1.0 microM) inhibited invasion of Matrigel. More importantly, studies in SCID mice demonstrated that taxol (50 to 250 mg/m2/day) blocked the establishment, growth, and long-term survival of PC-3 ML cells.

Isolation and characterization of PC-3 human prostatic tumor sublines which preferentially metastasize to select organs in S.C.I.D. mice

We have developed and partially characterized a mouse model system for studying human prostate tumor cell metastases in vivo. To develop this model we have selected highly invasive (3 x I.) and non-invasive (3 x N.I.) PC-3 human prostatic tumor sublines based on enhanced and diminished capacities to migrate across a reconstituted basement membrane barrier (Matrigel) in Boyden chamber chemotactic assays. When the 3 x I. cells were injected intravenously (i.v.) in the tail vein of severe combined immune deficient (scid) mice, the cells initially metastasized to a wide variety of tissues as demonstrated by using [125I] IUdR labeled cells and histology. Four distinct sublines were eventually isolated which preferentially metastasized at approximately 80% efficiency to the lumbar vertebrae (PC-3 ML), the mandibular region of the right cheek (PC-3 MC), the rib cartilage (PC-3 MR), and the right front knee bone (PC-3 MK), respectively. Implantation experiments at different sites indicated that organ metastases may somehow be conferred on the tumor subclones by the host tissue.

Regulation of kinesin expression and type IV collagenase secretion in invasive human prostate PC-3 tumor sublines

PC-3 human prostatic tumor sublines have been previously isolated which exhibit striking differences in their invasive and metastatic phenotypes. This work has been extended here to measure and compare the levels of kinesin, a microtubule-dependent translocator molecule, in the PC-3 sublines. Western blots, slot blots, radiolabeling, and immunoprecipitation analysis showed that kinesin was expressed in the highly invasive and metastatic sublines at levels which were elevated above the base-line levels observed in the parent PC-3 cells. In comparison, kinesin was not expressed in detectable amounts in the noninvasive cell lines. The conditioned medium of the metastatic PC-3 sublines contained a heat- and trypsin-sensitive protein which exhibited a dosage-dependent capacity to stimulate increased kinesin expression, type IV collagenase secretion, and invasion of Matrigel by the metastatic sublines. The noninvasive sublines failed to secrete a similar stimulatory factor(s) or respond to the conditioned medium of metastatic sublines. Various growth factors and cytokines tested (platelet-derived growth factor, epidermal growth factor, insulin-like growth factor, formylmethionineleucinephenylalanine) had no significant effect on either kinesin expression or protease secretion and invasion. Pertussis toxin blocked the stimulatory effects of the conditioned medium, but other agents known to interfere with adenylate cyclase pathways (i.e., cholera toxin, forskolin, 8-bromoadenosine) failed to block stimulation. The data show for the first time that kinesin, protease secretion, and the resulting invasion process may be regulated in a coordinated manner by an autocrine factor(s) which activates G-protein-dependent processes.

Evidence that estramustine binds MAP-1A to inhibit type IV collagenase secretion

Estramustine is a novel anti-microtubule drug shown to bind MAP-1 and MAP-2 (microtubule-associated proteins) in vitro. In this paper we have shown that estramustine specifically binds MAP-1A in Du 145a cells, resulting in disruption of MAP-1A microtubules and inhibition of type IV collagenase secretion. Immunofluorescence studies revealed that at 30 microM levels estramustine blocked type IV collagenase secretion by partial disruption of the MAP-1A microtubule networks. Immunoprecipitation studies with polyclonal antibodies provided quantitative evidence that 30–60 microM estramustine blocked secretion of a 105 × 10(3) Mr type IV collagenase. Pulse-labeling experiments confirmed that the effect was not a result of inhibition of either protein synthesis or altered rates of type IV collagenase turnover. Finally, drug uptake studies with [3H]estramustine, scintillation counting and fluorography demonstrated that the principal target of the drug was MAP-1A. For the first time we have shown that the drug blocks secretion by binding MAP-1A and causing incomplete disruption of the microtubule networks.

Properties of kinesin isolated from human prostatic DU 145 tumor cells and bovine brain

We have isolated and compared the 116-kilodalton (kDa) kinesin heavy chain from DU 145 human prostatic tumor cells and bovine brain. Comparative sodium dodecyl sulfate - polyacrylamide gel electrophoreses (SDS-PAGE), Western blots, and proteolytic digestion analysis all showed that the 116-kDa polypeptides from both sources were indistinguishable. Polyclonal antibodies raised against sea urchin kinesin cross-reacted with both brain and DU 145 kinesin on Western blots. SDS-PAGE and A-5m chromatographic studies indicated that kinesin forms a quarternary heteropolymer of approximately 400 kDa. DU 145 cells had three proteins of 116, 72, and 64 kDa forming the heteropolymer, in a 2:1:1 ratio, whereas brain cells appeared to have equimolar amounts of the 116-kDa heavy chain and a 64-kDa light chain.

Deprivation/enhancement fantasy patterns in children

Previous studies have shown that females tell stories that change from negative experiences (deprivation) to positive experiences (enhancement) and males tell stories that change in the opposite direction. The current study examines this phenomenon in children using a different story-telling procedure. Results were not consistent with those of previous studies.

Estramustine binds a MAP-1-like protein to inhibit microtubule assembly in vitro and disrupt microtubule organization in DU 145 cells

The twofold purpose of the study was (a) to determine if a MAP-1-like protein was expressed in human prostatic DU 145 cells and (b) to demonstrate whether a novel antimicrotubule drug, estramustine, binds the MAP-1-like protein to disrupt microtubules. SDS-PAGE and Western blots showed that a 330-kD protein was associated with microtubules isolated in an assembly buffer containing 10 microM taxol and 10 mM adenylylimidodiphosphate. After purification to homogeneity on an A5m agarose column, the 330-kD protein was found to promote 6 S tubulin assembly. Turbidimetric (A350), SDS-PAGE, and electron microscopic studies revealed that micromolar estramustine inhibited assembly promoted by the 330-kD protein. Similarly, estramustine inhibited binding of the 330-kD protein to 6-S microtubules independently stimulated to assemble with taxol. Immunofluorescent studies with beta-tubulin antibody (27B) and MAP-1 antibody (MI-AI) revealed that 60 microM estramustine (a) caused disassembly of MAP-1 microtubules in DU 145 cells and (b) removed MAP-1 from the surfaces of microtubules stabilized with 0.1 microM taxol. Taken together the data suggested that estramustine binds to a 330-kD MAP-1-like protein to disrupt microtubules in tumor cells.

Blocking of collagenase secretion by estramustine during in vitro tumor cell invasion

The effects of the antitumorigenic drug estramustine on tumor cell membrane penetration (invasion) were investigated in vitro by utilizing a synthetic basement membrane system (a modified Boyden chamber). Tumor cells were plated on a "partition barrier," consisting of a porous filter (8-micron pores) which was coated with a reconstituted basement membrane matrix (Matrigel), and induced to migrate across the barrier with conditioned medium obtained from 9DU 145 human prostatic tumor cells (passage 9). Quantitative radiolabeling studies demonstrated that specially isolated lines (isolated by several passages through the Matrigel) of DU 145 cells, A2058 melanoma, and B16-F10 melanoma cells were highly invasive such that 15 to 20% migrated across a 1-mm-thick Matrigel layer within 5 h at 37 degrees C. NIH-3T3 cells, mouse fibroblasts, and 20DU 145 cells (passage 20) exhibited little or no membrane invasive behavior. Micromolar concentrations of estramustine (30 to 120 microM) inhibited invasion by the invasive cell lines in a dosage-dependent fashion. Quantitative enzymatic assays and radioimmune assays demonstrated that estramustine inhibited membrane invasion by blocking type IV collagenase secretion. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blots confirmed that 30 to 60 microM estramustine blocked secretion of a Mr 105,000 collagenase protein. Indirect studies showed that a collagenase antibody raised against the Mr 105,000 protein and inhibitors of proteinase activity, including a metalloproteinase inhibitor, and 1,10-phenanthroline, blocked invasion. Because the antibodies inhibited type IV collagenase digestion of 3H-mouse type IV collagen, and invasion simultaneously, it is proposed that collagenolytic activity is involved in invasion. These data demonstrate that estramustine blocks proteinase secretion, and suggest that estramustine may be a useful therapeutic drug for the prevention of metastasis.

Estramustine binds MAP-2 to inhibit microtubule assembly in vitro

We have investigated the ability of estramustine to bind to rat brain microtubule-associated proteins (MAPs) and purified MAP-2 in vitro. [3H]estramustine's relative affinity for tubulin and MAPs was assessed by gel filtration chromatography, immunoprecipitation and binding assays. Scatchard analysis demonstrated a specific affinity of the drug for MAP-2. Calculations from kinetic parameters and non-linear regression analysis gave a Kd of 15 microM, and a Bmax of 3.4 × 10(−7)M ml-1. Extrapolation of this value suggested that each MAP-2 molecule binds approximately 20 molecules of estramustine. Microtubule assembly studies and SDS-polyacrylamide gel electrophoresis revealed that at 20–60 microM levels, estramustine inhibited the association of MAPs with taxol microtubules. Turbidity (A350) studies further demonstrated that 20–60 microM-estramustine inhibited MAP-2-driven tubulin assembly and produced microtubule disassembly. Electron-microscopic studies confirmed the centrifugation and turbidity results. The data demonstrated that estramustine can bind MAPs and MAP-2 specifically, thereby inhibiting microtubule assembly.

Evidence for intermediate filaments in squirrelfish erythrophores of Holocentrus ascensionus (Rufus)

We have documented the presence of intermediate filaments (IF) in cultured erythrophores of the squirrelfish Holocentrus ascensionus (Rufus). SDS-PAGE and Western blots with monoclonal antibodies T11 and R12 demonstrated that isolated IF consisted of a pair of polypeptides of 54 and 52 kDa. Immunofluorescent studies revealed that the two proteins formed prominent radially oriented IF networks in erythrophores. Immunoelectron microscopic studies showed that the IF were distributed in a "spider-web"-like network of filaments which occasionally intersected with the microtubule surfaces. The IF proteins also were found in fish iridiphores but not in fish epithelial cells which cocultured with the chromatophores.

Immunofluorescent studies of the anti-microtubule effects of the anti-cancer drug estramustine

Immunofluorescent studies in human prostatic carcinoma cells (DU 145) and cultured squirrel fish epithelial cells (a non-cancer cell) revealed that estramustine, a conjugate of estradiol and nor-nitrogen mustard, possessed microtubule disassembly properties. Sixty microM estramustine produced disassembly at both the proximal and distal ends of microtubules, producing short pieces of less than 2 microM which were "wavy" and oriented in a random manner. With increased time of drug exposure these short microtubules disappeared, to be accompanied by a gradual disassembly of a small population of longer microtubules (greater than 7-8 microM). In dividing DU 145 cells it was possible to show a different degree of sensitivity of specific microtubule-containing cellular structures. In mitotic figures the asters were most sensitive and disappeared completely following exposure to estramustine. These were followed by the "pole-to-pole" and "chromosomal" fibers. In cytokinesis, the intercellular fibers between daughter cells were comparatively resistant to the drug. Estramustine did not induce disassembly of the vimentin filaments in non-dividing or dividing cells but did cause their collapse around the nucleus or the mitotic apparatus. These data suggest that specific microtubules have differing sensitivity to estramustine.

Plasmodium falciparum: fine structural changes in the cytoskeletons of infected erythrocytes

Following parasitization by Plasmodium falciparum, numerous changes take place in the host erythrocyte membrane. In this study, we used the technique of whole cell mount electron microscopy to determine if the ultrastructure of the erythrocyte cytoskeleton changed following parasitization with knobby and knobless strains of P. falciparum. Using this technique, a network of spectrin filaments (3-10 X 45-120 nm) branching from electron dense junctions (15-25 nm in diameter), the presumed site of bands 4.1 and actin, were visualized. The overall architecture of normal and parasitized erythrocyte cytoskeletons was the same: however, additional patches (35 to 60 nm in size) and aggregates (30 X 150 nm) of electron dense material were present in parasitized skeletons. The ultrastructure of knobby and knobless cytoskeletons was similar, except knobless skeletons usually did not possess the larger aggregates of material. Antigens associated with the erythrocyte cytoskeleton of cells infected with knobby and knobless strains, but not uninfected cells, were demonstrated by indirect immunofluorescence. Results suggest that antigens, associated with the erythrocyte cytoskeleton, may contribute to perturbations in the host erythrocyte membrane.

Localization of Plasmodium falciparum histidine-rich protein 1 in the erythrocyte skeleton under knobs

Plasmodium falciparum parasites that induce knobs in the host erythrocyte membrane (K+ phenotype) synthesize a 90 kDa histidine-rich protein (PfHRP-1), whereas knobless variants do not. A monoclonal antibody (mAb 89) to PfHRP-1, in combination with cryo-thin section immunoelectron microscopy, localized the antigen in the parasitophorous vacuolar space and vesicles within the erythrocyte cytosol. Additional immunoelectron microscopic studies showed that PfHRP-1 was also associated with submembranous electron-dense material under knobs and with microfilaments of the host erythrocyte skeletal network. Immunofluorescence and immunoelectron microscopy of intact, non-fixed K+ infected erythrocytes using mAb 89 and a rabbit antiserum raised against purified PfHRP-1, failed to identify any surface exposed epitopes. These antibodies also failed to block cytoadherence of infected erythrocytes to C32 melanoma cells or to affect macrophage phagocytosis of infected erythrocytes.

Hormone-independent, non-alkylating mechanism of cytotoxicity for estramustine

Over two decades, experience with estramustine has provided limited data which support an estrogenic mechanism of action and no data which indicate the nitrogen mustard involvement in the cytotoxic properties of the drug. Consideration of the carbamate-ester portion of estramustine supports the pharmacokinetic evidence that estramustine has a long half life since enzymatic hydrolysis of the carbamate is an uncommon event. Using a variety of immunocytochemical and cellular morphology procedures, estramustine per se has been found to express anti-cytoskeletal properties through non-covalent binding to microtubule associated proteins (MAP's). In both fish erythrophores and in dividing human prostatic carcinoma cells, estramustine exerts an antimicrotubule effect at micromolar concentrations. Thus, estramustine possesses unique pharmacology and protein binding specificity. As such, it should not be classified as an alkylating agent. The estrogenic effects, while possibly of relevance to clinical administration, are not the primary mechanism by which the drug exerts cytotoxicity.

Polarized pigment granule transport occurs in the absence of microtubules in squirrelfish erythrophores: studies of the effects of estramustine

We have re-examined the involvement of microtubules in the process of pigment granule transport in squirrelfish erythrophores in situ (i.e. on scales). Light-microscopic studies revealed that following exposure to 5 microM-nocodazole for 1 h at 4 degrees C erythrophores retained an ability to aggregate and disperse their pigment uniformly, though at reduced rates. Serial thick-section stereo high-voltage electron-microscopic studies showed that the entire microtubule population was removed by drug treatment and that the microtubules were not reassembled as a result of pigment translocation processes in the presence of reduced levels of nocodazole (0.4 microM). Immunofluorescence microscopic studies confirmed that nocodazole (0.5-1 microM) produced rapid disassembly of the microtubules. Whole-mount electron-microscopic studies showed that the pigment granules were suspended in a cross-linking network of 3–10 nm filaments, which appeared to support ordered pigment transport in situ in the absence of microtubules. Drug inhibition studies showed that micromolar levels of estramustine, a novel anti-MAPs (microtubule-associated proteins) drug, reversibly inhibited pigment transport. The results suggest that an estramustine-sensitive cytomatrix component might produce polarized pigment transport in intact erythrophores.

Evidence that MAP-2 may be involved in pigment granule transport in squirrel fish erythrophores

We have demonstrated the presence of MAP-2 in squirrel fish erythrophores using SDS-PAGE, immunoblot, and immunoprecipitation techniques. The monoclonal antibodies used (AP-9, -13, -14) were raised against distinct antigenic sites on Chinese hamster brain MAP-2. Immunoprecipitation studies demonstrated that all three antibodies bind a 300 K protein found in crude cell extracts and in partially purified MAP fractions isolated from erythrophores of the squirrel fish Holocentrus rufus. Immunofluorescent studies confirmed that the 300 K protein was present in cultured erythrophores. Studies of cells induced to aggregate and disperse their pigment granules revealed that the 300 K protein comigrated with the pigment, suggesting that the 300 K protein may constitute part of the "alpha-cytomatrix" involved in pigment translocations.

The cytomatrix regulates "resolute" transport in erythrophores

Light microscopic studies have indicated that most microtubule-directed transport is either saltatory or resolute in nature. The latter form of transport is an intriguing phenomenon, because it commonly involves the unidirectional bulk motion of an organelle(s) such as chromosomes in dividing cells or pigment granules in chromatophores. We have investigated the ultrastructural and biochemical basis for the resolute transport of pigment in chromatophores. Light and EM studies of erythrophores in situ have clearly shown that when the microtubules were completely removed with nocodazole, resolute transport continued and was stimulated by aggregating and dispersing agents. Light and electron microscopic studies of cultured erythrophores permeabilized with digitonin indicated that resolute motion was produced by a cytomatrix of 3 to 7 nm filaments. Immunofluorescent analysis with several monoclonal antibodies raised against MAP-2 further demonstrated that MAP-2 was an important component of the contractile cytomatrix that powers pigment aggregation and dispersion. We conclude that a microtubule-associated cytomatrix normally produces resolute pigment transport in chromatophores.