KAI1, a putative marker for metastatic potential in human breast cancer

The KAI1 gene maps to chromosome 11p11.2, is a metastasis-suppressor gene for human prostate cancer and also is involved in the progression of human pancreatic and non-small cell lung cancer. Recently, we showed that introduction of a single copy of normal, neomycin-tagged human chromosome 11 into highly metastatic MDA-MB-435 breast cancer cells suppressed breast cancer metastasis. Concomitantly, KAI1 levels were higher in chromosome 11/MDA-MB-435 cell clones. The purpose of this study was to test whether KAI1 expression is indicative of breast cancer metastasis using a panel of immortalized breast epithelial and breast cancer cell lines that represent multiple stages of breast cancer progression. Metastatic cell clones isolated from the parental mixed, wild-type population of MDA-MB-435 cells expressed the lowest levels of KAI1 mRNA and chromosome 11 containing MDA-MB-435 (neo11/MDA-MB-435.A3 and neo11/MDA-MB-435.B1) cells had approximately twice as much KAI1 mRNA than the parental clones. MCF-10A, an immortalized normal-like non-tumorigenic mammary epithelial cell line, had the highest level of KAI1 mRNA. We compared the metastatic propensity and invasive ability of a continuum of breast cancer cells with varying degrees of progression toward malignancy and found that these parameters tended to correlate inversely with KAI1 mRNA expression. These data suggest that, in addition to its role in human prostate, pancreatic and non-small cell lung cancer, KAI1 may also be a useful marker for staging human breast disease.

Suppression of metastasis in human breast carcinoma MDA-MB-435 cells after transfection with the metastasis suppressor gene, KiSS-1

Based on the observation that chromosome 1q deletions are not infrequent in late-stage human breast carcinomas, we tested whether the recently discovered human melanoma metastasis suppressor gene, KiSS-1, which maps to chromosome 1q32-q41, could suppress metastasis of the human breast carcinoma cell line MDA-MB-435. Parental, vector-only transfectants and KiSS-1 transfectant clones were injected into the mammary fat pads of athymic nude mice and assessed for tumor growth and spontaneous metastasis to regional lymph nodes and lungs. Expression of KiSS-1 reduced metastatic potential by 95% compared to control cells but did not suppress tumorigenicity. Metastasis suppression correlated with a decreased clonogenicity in soft (0.3%) and hard (0.9%) agar. Although the overall rate of cell adhesion to extracellular matrix components was unaffected, KiSS-1 transfectants spread on immobilized type-IV collagen more rapidly than did control populations. Invasion and motility were unaffected by KiSS-1. Based on the predicted structure of the KiSS-1 protein, our results imply a mechanism whereby KiSS-1 regulates events downstream of cell-matrix adhesion, perhaps involving cytoskeletal reorganization. In addition to its already described role in melanoma, our results show that KiSS-1 also functions as a metastasis suppressor gene in at least some human breast cancers.

Identification of highly expressed genes in metastasis-suppressed chromosome 6/human malignant melanoma hybrid cells using subtractive hybridization and differential display

Microcell-mediated transfer of chromosome 6 into human melanoma cell lines C8161 and MelJuSo suppresses metastasis by at least 95% without affecting tumorigenicity. Subtractive hybridization and differential display were used to identify the molecule(s) responsible for suppressing metastasis in neo6/melanoma (neo6/C8161 and neo6/MelJuSo) hybrids. Seven cDNA clones exhibiting quantitatively or qualitatively higher expression in neo6/melanoma hybrids were obtained. These genes fell into 2 categories: 1) transcription-related genes (AP-2A, HMG-I(Y) and a novel isoform of nucleophosmin B23), which have previously been shown to regulate metastasis-associated genes; and 2) novel genes. One of the novel genes, designated KiSS-1, significantly suppressed metastasis of the human malignant melanoma cell lines MelJuSo and a highly metastatic subclone of C8161, C8161cl.9, following transfection and constitutive expression. Our results illustrate the power of subtractive hybridization and differential display to identify functional metastasis-controlling genes in human melanoma.

Suppression of human melanoma metastasis following introduction of chromosome 6 is independent of NME1 (Nm23)

Metastasis is suppressed more than 95% following microcell-mediated transfer of a single copy of neomycin-tagged human chromosome 6 (neo6) into the human melanoma cell lines C8161 and MelJuSo. Concomitant with metastasis suppression is upregulation of NME1 (Nm23-H1) mRNA and protein expression. The purposes of this study were to determine whether NME1 expression was responsible for metastasis suppression in neo6/melanoma hybrids, and whether genes on chromosome 6 regulate NME1. Using neo6/C8161 cells, transfection of CAT reporter constructs linked to the NME1 promoter failed to consistently induce CAT. Therefore, it does not appear that genes on chromosome 6 directly control transcription of NME1. Transfection and overexpression of NME1 in MelJuSo, under the control of the CMV promoter, resulted in 40-80% inhibition of lung metastasis following i.v. inoculation of 2 x 10(5) cells. Only one transfectant of C8161 subclone 9 (C8161cl.9) cells was suppressed for metastasis. Control transfections with pCMVneo or pSV2neo did not suppress metastasis in either cell line. Taken together, these data suggest that NME1 can reduce metastatic potential of some human melanoma cells; but, this inhibitory activity appears to be independent of the metastasis suppression following introduction of chromosome 6 into C8161 and MelJuSo human melanoma cell lines.

Elevated expression of the neutrophil calcium-binding protein, MRP-14, in metastasis-enhancing neutrophils

Tumor-elicited neutrophils (tcPMN) purified from 13762NF mammary adenocarcinoma tumor-bearing rats enhanced metastasis of syngeneic cells when co-injected intravenously; whereas, circulating (cPMN) and phorbol esteractivated (PMA-PMN) neutrophils did not [Welch et al. (1989) Proc. Natl. Acad. Sci. 86:5859-63]. We hypothesized that differential protein expression was responsible for functional differences between the neutrophil subtypes. Two-dimensional polyacrylamide gel electrophoresis was used to compare neutrophils (cPMN, PMA-PMN) purified from the peripheral blood of healthy, syngeneic nontumor-bearing rats, to tcPMN collected from rats with highly metastatic [clone MTLn3, subclone MTLn3(T44).5] or poorly metastatic [subclone MTLn3(T44).11] tumors growing in the mammary fat pads. Quantitative differences in polypeptide expression were observed between these functionally distinct PMN populations. Compared to cPMN, expression of a M(r) approximately 38.8 kDa (pl approximately 8) polypeptide was similar in tcPMN collected from poorly metastatic tumor-bearing rats, higher in PMA-PMN, and further increased in tcPMN from rats with highly metastatic tumors. Expression of two polypeptides, M(r) approximately 14.1 kDa (pl approximately 6) and M(r) approximately 43.3 kDa (pl approximately 5), was greater in tcPMN from rats with highly metastatic tumors compared to cPMN, PMA-PMN, or tcPMN from rats bearing poorly metastatic tumors. The latter two polypeptides thus appeared to be specifically increased in tcPMN from rats bearing highly metastatic tumors. Because it was most abundant and displayed the greatest differences between PMN subtypes, the M(r) approximately 14.1 kDa protein was further analyzed. Tryptic digests followed by internal sequence analyses of resulting peptide fragments revealed that the M(r) approximately 14.1 kDa contained amino acid sequences that were identical to those of MRP-14, a 14 kDa neutrophil calcium-binding protein belonging to the S-100 protein family of calcium-binding proteins. These results suggest a novel function for MRP-14 and suggest that MRP-14 may represent a marker for distinguishing phenotypically distinct subpopulations of neutrophils, particularly tcPMN with metastasis-enhancing abilities.

KiSS-1, a novel human malignant melanoma metastasis-suppressor gene

BACKGROUND

Microcell-mediated transfer of chromosome 6 into human C8161 and MelJuSo melanoma cell suppresses their ability to metastasize by at least 95% without affecting their tumorigenicity. This observation demonstrates that the ability to metastasize is a phenotype distinct from tumor formation and suggests that tumorigenic cells acquire metastatic capability only after accumulating additional genetic defects. These results also imply that mutations of genes on chromosome 6 are among those late genetic changes responsible for metastatic potential. They further suggest that a melanoma metastasis-suppressor gene(s) is encoded on chromosome 6 or is regulated by genes on chromosome 6.

PURPOSE

Our objective was to identify the gene(s) responsible for the suppression of metastasis in chromosome 6/melanoma cell hybrids.

METHODS

A modified subtractive hybridization technique was used to compare the expression of messenger RNAs (mRNAs), via an analysis of complementary DNAs (cDNAs), in metastatic cells (C8161 or MelJuSo) and nonmetastatic hybrid clones (neo6/C8161 or neo6/MelJuSo).

RESULTS

A novel cDNA, designated KiSS-1, was isolated from malignant melanoma cells that had been suppressed for metastatic potential by the introduction of human chromosome 6. Northern blot analyses comparing mRNAs from a panel of human melanoma cells revealed that KiSS-1 mRNA expression occurred only in nonmetastatic melanoma cells. Expression of this mRNA in normal heart, brain, liver, lung, and skeletal muscle was undetectable by northern blot analysis. Weak expression was found in the kidney and pancreas, but the highest expression was observed in the placenta. The KiSS-1 cDNA encodes a predominantly hydrophilic, 164 amino acid protein with a polyproline-rich domain indicative of an SH3 ligand (binds to the homology 3 domain of the oncoprotein Src) and a putative protein kinase C-alpha phosphorylation site. Transfection of a full-length KiSS-1 cDNA into C8161 melanoma cells suppressed metastasis in an expression-dependent manner.

CONCLUSIONS

These data strongly suggest that KiSS-1 expression may suppress the metastatic potential of malignant melanoma cells.

IMPLICATIONS

KiSS-1 may be a useful marker for distinguishing metastatic melanomas from nonmetastatic melanomas.

Metastasis suppressed, but tumorigenicity and local invasiveness unaffected, in the human melanoma cell line MelJuSo after introduction of human chromosomes 1 or 6

Progression of human melanoma toward increasing malignant behavior is associated with several nonrandom chromosomal aberrations, most commonly involving chromosomes 1, 6, 7, 9, and 10. We previously showed that introduction of human chromosome 6 into the highly metastatic human malignant melanoma cell line C8161 completely suppressed metastasis without altering tumorigenicity (Welch DR, Chen P, Miele ME, et al., Oncogene 9:255-262, 1994). Alterations of chromosome 1 are the most frequent chromosome abnormality observed in melanomas, and they frequently arise late in tumor progression. The purpose of the study presented here was to compare the effects of chromosomes 1 and 6 on malignant melanoma metastasis. By using microcell-mediated chromosome transfer, single copies of neo-tagged human chromosomes 1 or 6 were introduced into the human melanoma cell line MelJuSo. The presence of the added chromosome was verified by G banding of karyotypes, fluorescence in situ hybridization, and screening for polymorphic markers on each chromosome. The incidence and number of metastases per lung after intravenous or intradermal injection of parental MelJuSo cells was significantly (P<0.01) greater than those of hybrids containing either chromosome 1 or chromosome 6, although chromosome 1 was a less potent inhibitor of metastasis than chromosome 6. Cultures established from primary tumors and metastases remained neomycin resistant, suggesting that portions of the added chromosomes were retained. These results strengthen the evidence for the presence of a melanoma metastasis suppressor gene on chromosome 6. neo6/MelJuSo hybrids expressed 2.4- to 3.4-fold more of the melanoma differentiation-associated gene mda-6 (previously shown to be identical to WAF1/CIP1/Sdi1/CAP20) than parental metastatic cells. mda-6/WAF1 is among the candidate genes on chromosome 6. These results also demonstrate, for the first time, the existence of metastasis suppressor genes on human chromosome 1, although these genes appear to be less potent than the one encoded on chromosome 6.

Metastasis suppressed, but tumorigenicity and local invasiveness unaffected, in the human melanoma cell line MelJuSo after introduction of human chromosomes 1 or 6

Progression of human melanoma toward increasing malignant behavior is associated with several nonrandom chromosomal aberrations, most commonly involving chromosomes 1, 6, 7, 9, and 10. We previously showed that introduction of human chromosome 6 into the highly metastatic human malignant melanoma cell line C8161 completely suppressed metastasis without altering tumorigenicity (Welch DR, Chen P, Miele ME, et al., Oncogene 9:255-262, 1994). Alterations of chromosome 1 are the most frequent chromosome abnormality observed in melanomas, and they frequently arise late in tumor progression. The purpose of the study presented here was to compare the effects of chromosomes 1 and 6 on malignant melanoma metastasis. By using microcell-mediated chromosome transfer, single copies of neo-tagged human chromosomes 1 or 6 were introduced into the human melanoma cell line MelJuSo. The presence of the added chromosome was verified by G banding of karyotypes, fluorescence in situ hybridization, and screening for polymorphic markers on each chromosome. The incidence and number of metastases per lung after intravenous or intradermal injection of parental MelJuSo cells was significantly (P<0.01) greater than those of hybrids containing either chromosome 1 or chromosome 6, although chromosome 1 was a less potent inhibitor of metastasis than chromosome 6. Cultures established from primary tumors and metastases remained neomycin resistant, suggesting that portions of the added chromosomes were retained. These results strengthen the evidence for the presence of a melanoma metastasis suppressor gene on chromosome 6. neo6/MelJuSo hybrids expressed 2.4- to 3.4-fold more of the melanoma differentiation-associated gene mda-6 (previously shown to be identical to WAF1/CIP1/Sdi1/CAP20) than parental metastatic cells. mda-6/WAF1 is among the candidate genes on chromosome 6. These results also demonstrate, for the first time, the existence of metastasis suppressor genes on human chromosome 1, although these genes appear to be less potent than the one encoded on chromosome 6.

Suppression of MDA-MB-435 breast carcinoma cell metastasis following the introduction of human chromosome 11

To determine the relevance of genetic information on chromosome 11 in the development of metastatic breast tumors, we introduced a normal human chromosome 11 into the highly metastatic MDA-MB-435 breast carcinoma cell line via the microcell-mediated chromosome transfer technique. Although the MDA-MB-435 recipient cell line and four randomly selected microcell hybrid clones remained tumorigenic in nude mice, the hybrids were >95% suppressed for metastasis to lung and regional lymph nodes (p<0.01). We also tested whether chromosome 6 harbors a metastasis-suppressor gene for breast cancer as observed previously for human melanoma. Grouped together, the four neo6 microcell hybrids had no statistically significant reduction in the incidence or number of lung or lymph node metastases compared to the weakly metastatic, subcloned parent cell line, MDA-MB-453.7. Expression of nm23-H1 (NME1), a known metastasis-suppressor gene in this breast cancer cell line, did not correlate with metastasis suppression in the microcell hybrids. These results further demonstrate that control of metastasis is molecularly distinct from tumorigenic potential. They also indicate that chromosome 11 encodes a metastasis-suppressor gene for human breast cancer.

p53-independent increase in p21WAF1 and reciprocal down-regulation of cyclin A and proliferating cell nuclear antigen in bromodeoxyuridine-mediated growth arrest of human melanoma cells

Differentially regulated expression of activators and inhibitors of cyclin-dependent kinases (cdks) modulate cell cycle progression. In normal fibroblasts, these complexes consist of the cdk inhibitor p21WAF1/PCNA/G1 cyclin/cdk. We now show that bromodeoxyuridine (BrdUrd), a thymidine analogue and radiation sensitizer, inhibits growth and activity of cyclin A-cdk2 kinase in metastatic C8161 and nonmetastatic neo 6.3/C8161 human melanoma cells. Inhibition is not due to altered levels of cyclin D or catalytic cdk2 but involves a decrease in cyclin A and proliferating cell nuclear antigen, paralleled by higher levels of p21WAF1 without increases in p53. In contrast to serum starvation, which prevents accumulation of cyclins A and D in normal fibroblasts, such treatment did not down-regulate either cyclin in these melanoma cells, implying an aberrant control for G1 cyclins in these tumor cells. However, cyclin A was decreased by BrdUrd, suggesting that this pyrimidine analogue arrests melanoma cells at a G1 transition point, unlike that of serum starvation. This is the first report indicating that the antitumor therapeutic action of BrdUrd may be mediated by a p53-independent reciprocal effect on activators and inhibitors of cdk kinases.

Highly metastatic 13762NF rat mammary adenocarcinoma cell clones stimulate bone marrow by secretion of granulocyte-macrophage colony-stimulating factor/interleukin-3 activity

Circulating neutrophil (polymorphonuclear leukocyte levels rise 50-fold in 13762NF tumor-bearing rats in proportion to the tumor's metastatic potential. Purified tumor-elicited neutrophils enhance metastasis of syngeneic tumor cells when co-injected intravenously; however, circulating and phorbol ester-activated polymorphonuclear neutrophils do not. The purpose of this study was to elucidate the source of tumor-elicited neutrophils in metastatic tumor-bearing rats. We examined the bone marrow in rats bearing tumors of poorly, moderately, and highly metastatic cell clones. Marrow from rats with highly metastatic tumors had increased cellularity (100%), myeloid to erythroid ratio (10:1), and megakaryocytes compared with control rats (cellularity, approximately 80%; myeloid to erythroid ratio, 5:1), with marrows from rats with moderately metastatic tumors having intermediate values. This suggested production of a colony-stimulating factor by the metastatic cells. To confirm this, bone marrow colony formation from control and tumor-bearing rats was compared. Colony number increased in proportion to the metastatic potential of the tumor. Conditioned medium from metastatic cells supported growth of the granulocyte-macrophage colony-stimulating factor/interleukin-3-dependent 32Dcl3 cell line, but media from nonmetastatic or moderately metastatic cells did not. Antibodies to murine granulocyte-macrophage colony-stimulating factor neutralized 32Dcl3 growth in tumor cell conditioned medium. These results suggest production of a granulocyte-macrophage colony-stimulating factor or interleukin-3-like activity by highly metastatic 13762NF clones and implicate a possible role for colony-stimulating factors in regulating the metastatic potential of mammary adenocarcinoma cell clones.

SOD2 (MnSOD) does not suppress tumorigenicity or metastasis of human melanoma C8161 cells

Manganese superoxide dismutase (MnSOD, encoded by the SOD2 gene mapping to chromosome 6q25) has been implicated as a tumor suppressor and as a metastasis suppressor in some tumor cell lines. We showed that introduction of an intact chromosome 6 into the metastatic melanoma cell line C8161 completely suppressed metastasis but did not affect tumorigenicity (Welch et al., (1994) Oncogene 9:255). The purpose of this study was to test whether SOD2 is the gene responsible for metastasis suppression. MnSOD protein levels of C8161 (measured by Western blot), before and after transfer of chromosome 6, showed no correlation with metastatic potential. To determine whether the lack of correlation was due to mutant, nonfunctional SOD2, a highly metastatic subclone of C8161 (C8161c1.9) was transfected with functional SOD2 or vector control (pSFFV). Metastatic potential and tumorigenicity were unchanged. Southern and Northern blots confirmed the presence of the transfected SOD2; however, total MnSOD protein and antioxidant activity were not significantly altered. These results suggest that levels of MnSOD are highly regulated within C8161 melanoma cells and that SOD2 does not suppress tumor formation nor metastatic potential in all human melanomas.

The melanoma differentiation-associated gene mda-6, which encodes the cyclin-dependent kinase inhibitor p21, is differentially expressed during growth, differentiation and progression in human melanoma cells

The combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) induces terminal differentiation with an irreversible loss of proliferative capacity in human melanoma cells. Using subtraction hybridization, cDNAs were identified that display enhanced expression in terminally differentiated and growth arrested human melanoma cells (Jiang and Fisher, 1993; Jiang et al., 1994a). A specific melanoma differentiation-associated (mda) cDNA, mda-6, is described whose expression inversely correlates with melanoma progression and growth. mda-6 is identical to WAF1/CIP1/SDI1 that encodes the M(r) 21,000 protein (p21) that is an inhibitor of cyclin-dependent kinases. Actively growing normal melanocyte, SV40-immortalized human melanocyte and dysplastic nevus cell lines synthesize elevated levels of mda-6 mRNA; whereas, actively proliferating radial and early vertical growth phase primary melanomas as well as metastatic human melanoma cells produce reduced levels of mda-6 mRNA. Treatment of primary and metastatic human melanoma cells with IFN-beta + MEZ results in growth inhibition and an increase in mda-6 expression. mda-6 expression also increases when human melanoma cells are grown to high saturation densities or when grown in serum-free medium. Using anti-p53 and anti-p21 antibodies, an inverse correlation is found between p53 and p21 protein levels during growth arrest and differentiation. Induction of growth arrest and terminal differentiation in H0-1 human melanoma cells by IFN-beta + MEZ results in a temporal decrease in wild-type p53 protein levels with a corresponding increase in p21 levels. In the Matrigel-assisted melanoma progression model, mda-6 expression decreases in early vertical growth phase primary human melanoma cells selected for autonomous or enhanced tumor formation in nude mice. In metastatic human melanoma cells displaying a loss of metastatic potential resulting from introduction of a normal human chromosome 6, mda-6 mRNA levels increase. Taken together, these studies indicate that mda-6 (p21) may function as a negative regulator of melanoma growth, progression and metastasis.

Suppression of human melanoma metastasis by introduction of chromosome 6 may be partially due to inhibition of motility, but not to inhibition of invasion

Active cellular motility and invasion play essential roles in metastasis. Introduction of normal, neo-tagged human chromosome 6 (neo6) into highly metastatic human melanoma cell line C8161 results in complete suppression of metastasis in vivo. To understand the mechanism by which metastasis was inhibited in neo6/C8161 hybrids, two in vitro assays, pseudopod protrusion and Membrane Invasion Culture System, were used to measure motility and invasion, respectively. neo6/C8161 hybrids are much less motile although they remained invasive, indicating that a metastasis-suppressor gene(s) on human chromosome 6 may regulate cellular motility, thereby inhibiting metastasis.

Evidence for paracrine regulation of experimental metastasis in 13762NF rat mammary adenocarcinoma cell clones

The ability of tumor cell lines to form experimental pulmonary metastases is determined in part by characteristics which are stable over many cell generations; in part by characteristics that are acquired by adaptation or phenotypic instability; but also in part by characteristics which may change over less than one cell generation. This study was designed to examine the hypothesis that tumor cells secrete and respond to paracrine factors which can reversibly modulate metastasis. The number of experimental lung metastases increased for 13762NF rat mammary adenocarcinoma cell clones MTF7 and MTLn3 as they approach 100% confluence. This observation corresponded to increased attachment to bovine brain capillary and bovine corneal endothelial monolayers and to ability of tumor cells to invade reconstituted basement membrane barriers in the Membrane Invasion Culture System (MICS), but did not correspond to cell cycle distribution, susceptibility to NK or PMN cell killing or average cell size/Coulter volume. While changing confluence did not qualitatively alter metastatic potential, modification of metastasis in a quantitative manner suggested that some properties pertinent to metastasis are transient and manipulatable. Tumor cell-conditioned medium (CM) collected from donor cells grown to defined levels of confluence when placed onto recipient cells reversibly raised or lowered metastatic potential depending upon the medium source and confluence of the recipient cells. CM from 20% confluent donor cultures reduced recipient cell metastatic potential. In contrast CM from 100% confluent cultures increased metastatic potential of subconfluent cells. Replacement with fresh unconditioned medium or leaving the medium unchanged did not alter experimental metastasis. These data suggest that metastasis involves steps which may be influenced by paracrine factors elaborated by tumor cells.

Enhanced metastatic ability of TNF-alpha-treated malignant melanoma cells is reduced by intercellular adhesion molecule-1 (ICAM-1, CD54) antisense oligonucleotides

Treating human malignant melanoma cells with tumor necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma) causes a dose- and time-dependent increase in surface expression of ICAM-1. Increased ICAM-1 expression corresponds to greater binding of human leukocyte functional antigen-1 (CD11a/CD18)-expressing peripheral blood mononuclear cells (PBMC) to C8161 monolayers, suggesting that cytokine-treated melanoma cells would be more metastatic due to PBMC-tumor cell emboli. The purpose of this study was: (1) to test whether TNF-alpha-treated human melanoma cells are indeed more metastatic than untreated C8161 and (2) to determine whether ICAM-1 plays a role in metastasis of C8161. When surface ICAM-1 expression is upregulated, formation of lung metastases in nude mice increases 1.5- to 4-fold (P < 0.05) for human melanoma cell lines C8161, MeWo, and A375. Treatment of C8161 with ICAM-1 phosphorothioate antisense oligonucleotides using cationic lipids results in > 90% inhibition of ICAM-1 surface expression as determined by ELISA and flow cytometry. Antisense ICAM-1-treated cells form 41-64% fewer metastases than sham-treated cells. Metastasis does not increase when antisense-treated melanoma cells are exposed to TNF-alpha. However, treatment of C8161 with antisense 5-lipoxygenase (5-LO) oligonucleotides inhibits metastases 39% in Lipofectin-treated cells, but does not inhibit TNF-alpha-induced upregulation of experimental metastases. Similar experiments were performed to measure PBMC adhesion to antisense oligonucleotide-treated C8161 cells; however, TNF-alpha-inducible increase in adhesion was unaffected by ICAM-1 or 5-LO antisense oligonucleotides. These results demonstrate that ICAM-1 is involved in melanoma metastasis, but probably not at the step of PBMC adhesion to C8161 cells.

Microcell-mediated transfer of chromosome 6 into metastatic human C8161 melanoma cells suppresses metastasis but does not inhibit tumorigenicity

Structural alterations of chromosome 6, including del(6q), are often associated with metastatic melanoma; therefore, we hypothesized that a metastasis-suppressor gene could be coded on human chromosome 6. Highly metastatic C8161 human malignant melanoma cells exhibit chromosomal changes typical of late-stage melanomas. Using microcell-mediated chromosome transfer, a copy of a normal human chromosome 6 was introduced into C8161. Three randomly selected hybrid clones (neo6/C8161.1, neo6/C8161.2 and neo6/C8161.3) were assayed for metastasis in athymic nude mice. All controls - parental C8161 cells, randomly-selected single cell clones, neo-transfected cell clones, neo11/C8161.2 and neo11/C8161.3 - were tumorigenic (270/272 mice) and metastatic (208/272 mice). neo6/C8161 hybrid cells were still tumorigenic (91/93 mice) but were not metastatic (0/195 mice). The presence of the added chromosomes was verified in cultured and tumor cells by amplification of polymorphic (CA)n markers using PCR-RFLP. The neo6/C8161 hybrids display growth and morphological patterns of more differentiated cells than C8161. In Northern blot analysis an inverse relationship between metastatic ability and metastasis-suppressor gene, nm23-H1, expression is observed - with clone neo6/C8161.1 expressing the highest level of nm23 transcripts, neo6/C8161.2 and neo6/C8161.3 expressing intermediate levels, and barely detectable levels are seen in C8161. Collectively, these results suggest that a malignant melanoma metastasis-regulatory gene may be located on human chromosome 6. These results further demonstrate that tumorigenicity and metastatic ability are distinct phenotypes.

Serum and plasma M(r) 92,000 progelatinase levels correlate with spontaneous metastasis of rat 13762NF mammary adenocarcinoma

The expression of metalloproteinases, such as type IV collagenase/gelatinase, enables tumor cells to degrade type IV collagen present in the basement membrane and correlates with metastatic potential of several tumor types. We found that increased levels of rat serum type IV collagenolytic activity are associated with increased 13762NF mammary adenocarcinoma metastases in lungs and lymph nodes of syngeneic rats. To investigate serum metalloproteinases responsible for type IV collagenolysis, we performed zymography and Western blot analysis of rat sera. A M(r) 92,000 progelatinase (progelatinase B, M(r) 92,000 type IV procollagenase, MMP-9) was detected on zymograms of rat sera within 16 days after intramammary fat pad inoculation of highly metastatic MTLn3 cells. The activated serum M(r) 92,000 progelatinase degraded sodium dodecyl sulfate-denatured type I and IV collagens but was not active on casein, albumin, hemoglobin, and immunoglobulin. Sera from rats with fat pad tumors and lung metastases formed from highly metastatic clones possessed greater than 7 times higher levels of serum M(r) 92,000 progelatinase than control sera or sera from rats bearing similar size fat-pad tumors of low or nonmetastatic clones. The results were confirmed by Western blot analysis of rat sera using rabbit anti-human M(r) 92,000 progelatinase antibodies. Similar results were obtained from the analysis of rat plasma samples. The serum and plasma M(r) 92,000 progelatinase levels correlated with the extent of metastases in the lung and lymph nodes. The results indicate that high levels of serum and plasma M(r) 92,000 progelatinase are associated with the presence of disseminated metastatic adenocarcinoma cells and suggest that this enzyme may facilitate the invasion of blood-borne tumor cells through vascular basement membranes.

U-77,863: a novel cinnanamide isolated from Streptomyces griseoluteus that inhibits cancer invasion and metastasis

Several cinnamoyl compounds have been shown to have antitumor activities, but not specifically anti-invasive or antimetastatic effects. U-77,863 (o-methyl cinnanamide) was originally isolated from a fermentation beer of Streptomyces griseoluteus and recently synthesized (Harper, DE and Welch DR. Journal of Antibiotics, in press). Based upon some differential activities of cinnanamides, in general, and U-77,863, specifically, we tested the hypothesis that U-77,863 could inhibit invasion and metastasis of human malignant melanoma cell lines C8161 and A375M. Pretreatment of melanoma cells in vitro with nontoxic doses of U-77,863 caused a dose-, and time-dependent, reversible reduction (IC50 = 12.5 micrograms/ml) of invasion through Matrigel-coated polycarbonate filters in the Membrane Invasion Culture System (MICS). Likewise, lung colonization was significantly (P < 0.05) inhibited when tumor cells were pretreated in vitro with U-77,863 prior to intravenous injection. Structure-activity analysis revealed that the acrylamide side-chain alone and cinnanamide were only slightly less potent than U-77,863, whereas cinnamic acid analogs did not inhibit tumor cell invasion at doses < or = 100 micrograms/ml. U-77,863 inhibits invasion and metastasis without decreasing growth rates or clonogenic potential. Adhesion to endothelial monolayers or extracellular matrices (Matrigel) is not affected by exposure to U-77,863. U-77,863 presumably inhibits metastasis by inhibiting tumor cell extravasation (invasion). U-77,863 is a lead compound for developing a novel class of anti-invasive/anti-metastatic drugs.

Isolation, purification, synthesis, and antiinvasive/antimetastatic activity of U-77863 and U-77864 from Streptomyces griseoluteus, strain WS6724

In screening of actinomycetes for structures with differential solid tumor activity, Streptomyces griseoluteus, strain WS6724 was found to produce U-77863 and U-77864. U-77863 exhibited antiinvasive activity in vitro in the membrane invasion culture system (MICS) and a dose-dependent antimetastatic activity in vivo versus K1735-M2 and B16-F10 murine melanomas. The isolation, purification, and synthesis of both structures and biological activity is reported.

Inhibition of tumor cell invasion by verapamil

Verapamil, a calcium channel antagonist, inhibits murine B16 melanoma and colon adenocarcinoma C26 tumor metastasis by altering platelet aggregation [Tsuruo, T., et al. (1985) Cancer Chemother. Pharmacol., 14:30-33]. However, the role of calcium homeostasis in regulating several biochemical pathways implicated in other steps of the metastatic cascade suggests that calcium channel antagonists could also inhibit metastasis by other mechanisms. In this report, non-toxic doses of verapamil reversibly decreased human A375M and C8161 melanoma cell invasion and metastasis in a dose-dependent manner. Verapamil reduced cellular invasion and metastases by up to 96% (range 78-96%). Concomitantly, verapamil disrupts microtubule and microfilament organization and inhibits unidirectional cell migration but does not affect cellular adhesion to endothelial monolayers or reconstituted basement membranes. In addition, tumor cells treated with verapamil have a decrease in mRNA of type IV collagenase, a proteinase important in tumor cell degradation of basement membranes. Collectively, these data offer additional evidence regarding the mechanisms of action of verapamil as an anti-metastatic agent.

Human melanoma cell invasion is inhibited in vitro by swainsonine and deoxymannojirimycin with a concomitant decrease in collagenase IV expression

A 48 h pretreatment of two malignant and invasive human melanoma cell lines with either swainsonine (an inhibitor of Golgi alpha-mannosidase II) or deoxymannojirimycin (a Golgi alpha-mannosidase I inhibitor) resulted in a dose-dependent decrease in the cells' ability to invade a reconstituted basement membrane in vitro. This effect was reversible within 48 h of removing the drugs. Treatment with either drug resulted in both cell lines being more resistant to the cytotoxic effects of the lectin leukoagglutinin (PHA-L) and more sensitive to the lectin concanavalin A which indirectly indicated a change in the cell surface oligosaccharide composition and structure consistent with the known effects of these drugs on N-linked oligosaccharide processing. A 25-33% decrease was noted in the adhesion of treated cells to either a reconstituted basement membrane or human umbilical vein endothelial cell monolayer while no change was measured in the cells' proliferative rates. A correlative decrease was observed, however, in the expression of human type IV collagenase mRNA which was recovered within 48 h of removing the drugs. These results suggest that a correlation exists between the drug-induced changes in the cell surface oligosaccharide composition and structure with a concomitant decrease in the mRNA and secreted levels of type IV collagenase and the ability of these cells to invade.