Laminin alpha5 chain metastasis- and angiogenesis-inhibiting peptide blocks fibroblast growth factor 2 activity by binding to the heparan sulfate chains of CD44

Recently, we reported that the laminin alpha5 synthetic peptide A5G27 (RLVSYNGIIFFLK, residues 2,892-2,904) binds to the CD44 receptor of B16-F10 melanoma cells via the glycosaminoglycans on CD44 and inhibits tumor cell migration, invasion, and angiogenesis in a dominant-negative manner. Here, we have identified the potential mechanism of A5G27 activity using WiDr human colorectal carcinoma cells. WiDr cells bound to the laminin A5G27 peptide via the heparin-like and chondroitin sulfate B glycosaminoglycan side chains of CD44. Cell binding to fibroblast growth factor (FGF2) was blocked by laminin peptide A5G27 but not by either a scrambled version of this peptide or by another laminin peptide known to bind cell surface proteoglycans. FGF2 signaling involving tyrosine phosphorylation was also blocked by laminin peptide A5G27 but was not affected by peptide controls. Finally, we have shown that peptide A5G27 directly blocks FGF2 binding to heparin. Peptide A5G27 has sequence homology to a region on FGF2 that binds heparin and the FGF receptor and is important in FGF2 central cavity formation. We conclude that peptide A5G27 inhibits metastasis and angiogenesis by blocking FGF2 binding to the heparan sulfate side chains of CD44 variant 3, thus decreasing FGF2 bioactivity.     

Laminin gamma 1 chain peptide, C-16 (KAFDITYVRLKF), promotes migration, MMP-9 secretion, and pulmonary metastasis of B16-F10 mouse melanoma cells

Laminin-1, a heterotrimer of alpha 1, beta 1, and gamma 1 chains specific to basement membrane, promotes cell adhesion and migration, proteinase secretion and metastases of tumour cells. Several active sites on the alpha 1 chain have been found to promote B16-F10 melanoma lung colonisation and here we have determined whether additional tumour promoting sites exist on the beta 1 and gamma 1 chains. Recently, we have identified novel cell adhesive peptides derived from laminin beta 1 and gamma 1 chains by systematic screening of synthetic peptides. Nine beta 1 peptides and seven gamma 1 peptides active for cell adhesion were tested for their effects on experimental pulmonary metastases of B16-F10 mouse melanoma cells in vivo. The most active adhesive peptide derived from the gamma 1 chain globular domain, C-16 (KAFDITYVRLKF), significantly enhanced pulmonary metastases of B16-F10 cells, whereas no other peptides showed enhancement. C-16 also stimulated migration of B16-F10 cells in the Boyden chamber assay in vitro. Furthermore, C-16 significantly induced the production of MMP-9 from B16-F10 cells. These results suggest that this specific laminin gamma 1 chain peptide has a metastasis-promoting activity and might be a new molecular target of anti-cancer treatment.     

The B16F10 cell receptor for a metastasis-promoting site on laminin-1 is a heparan sulfate/chondroitin sulfate-containing proteoglycan

Exposure to AG73, a synthetic peptide (LQVQLSIR) from the COOH-terminal region of the laminin alpha1 chain, induces a malignant phenotype in B16F10 melanoma cells. Coinjection of this peptide with the cells results in an increase of lung tumors and also the formation of liver tumors in approximately 50% of the mice (W. H. Kim et al., Int. J. Cancer, 77: 632-639, 1998). Here we have characterized the cell surface receptor and its functional groups on B16F10 cells. Peptide affinity chromatography identified a cell surface protein eluting with 1 M NaCl, which ran in SDS gels as a broad band of M(r) approximately 150,000-200,000. Digestion with heparitinase and chondroitinase produced a core protein of lower molecular weight (M(r) approximately 90,000). Involvement of the glycosaminoglycan (GAG) side chains was demonstrated by inhibition of cell binding to the peptide by heparin, heparan sulfate, and chondroitin sulfate B, but not by chondroitin sulfates A or C, or hyaluronic acid. The IC(50) for heparin was the lowest, followed by heparan sulfate, then chondroitin sulfate B, suggesting that the overall sulfation of the GAG side chain is critical. This was confirmed by inhibition of attachment with chemically modified heparin and heparan sulfate, which also showed that N or O linkages were not important for function. Using sized heparin fragments to inhibit cell binding to the peptide demonstrated that 16-mer is the minimum length required. B16F10 cells form a network when grown on Matrigel, and this is prevented by addition of the AG73 peptide. The GAGs alone did not affect network formation, but heparin, heparan sulfate, and chondroitin sulfate B reversed the inhibitory effect of the peptide, whereas other GAGs were inactive. Furthermore, removal of cell surface GAGs inhibited cell attachment to the peptide. Cells treated with glycosidases and coinjected with the peptide formed liver tumors equal to the control group receiving no peptide, suggesting that the GAGs play an early role in peptide-mediated tumor metastasis. These data indicate that the B16F10 cell receptor for a laminin metastasis-promoting sequence is a heparan sulfate/chondroitin sulfate-containing proteoglycan, and these GAG side chains are functionally important in the cell-peptide interaction.     

Binding of some metastatic tumor cell lines to fibrous elastin and elastin peptides

Recent suggestions that tumor-cell targeting of elastin-rich tissues (e.g., lung) correlates with the presence of surface elastin receptors have been investigated. Receptors for insoluble (fibrous) elastin and for soluble elastin peptides have been implemented in these correlations. A rapid assay for binding of insoluble elastin has been devised. Two of the cell lines tested (M27 and MAT-LyLu), which metastasize to the lung, strongly bound fibrous elastin whereas a third (B16-F10) did not. None of 4 metastatic cell lines that do not target the lung (A549,3LL, TA3, TA3-iso2) bound fibrous elastin. The ability of cell lines to interact with soluble elastin was tested by cell attachment to high-molecular-weight soluble elastin peptides adsorbed on plastic surface. Three of 7 tested cell lines, B16-F10, M27 and TA3, attached to a soluble elastin coating. In contrast to the rapid binding of insoluble elastin particles, the cell interaction with immobilized soluble elastin peptides was delayed, suggesting that induction of receptors for soluble elastin and/or modification of the elastin coat was occurring. Thus, all 3 tested cell lines where metastases target the lung, namely, MAT-LyLu, B16-F10 and M-27, show soluble- or insoluble-elastin interactions, whereas, of 4 cell lines not targeting lungs, only one, TA3, reacts with soluble elastin.     

4—乙酰胺苯基维甲酸酯抑制肿瘤细胞侵袭重组基底膜及其作用机理

目的研究新维甲类化合物４－乙酰胺苯基维甲酸酯（４－ＡＰＲ）对Ｂ１６－Ｆ１０小鼠黑色素瘤细胞侵袭能力的抑制作用,探讨其作用机理。方法癌细胞侵袭能力用重组基底膜侵袭试验衡量;ＰＡＧＥ底物酶谱方法检测Ⅳ型胶原酶活性;斑点杂交检测ＣＮＥ－２Ｚ细胞ＴＩＭＰ－１ｍＲＮＡ表达;以细胞生长曲线评价药物对Ｂ１６－Ｆ１０细胞的生长抑制作用。结果在１０－５ｍｏｌ／Ｌ和１０－６ｍｏｌ／Ｌ时,４－ＡＰＲ对Ｂ１６－Ｆ１０小鼠黑色素瘤细胞侵袭重组基底膜的抑制率分别为５４．２％和４１．９％,对ＣＮＥ－２Ｚ细胞培养上清中的Ⅳ型胶原酶活性有降低作用。此外,４－ＡＰＲ可抑制Ｂ１６－Ｆ１０细胞与ＬＮ、ＦＮ和Ｍａｔｒｉｇｅｌ的粘附,诱导ＣＮＥ－２Ｚ细胞ＴＩＭＰ－１ｍＲＮＡ表达。结论４－ＡＰＲ抑制Ｂ１６－Ｆ１０细胞侵袭重组基底膜。４－ＡＰＲ的抗侵袭活性与抑制肿瘤细胞的粘附,降低肿瘤细胞培养上清中Ⅳ型胶原酶的活性和（或）诱导肿瘤细胞ＴＩＭＰ－１ｍＲＮＡ表达等有关。     

B16-F10-luc-G5黑色素瘤细胞生物学特性的研究

目的：探讨B16-F10-luc-G5黑色素瘤细胞的生物学特性.方法：倒置荧光显微镜下连续观察B16-F10-luc-G5细胞生长动态.流式细胞术检测冻存复苏后、培养基漂浮细胞、胰酶消化损伤后的细胞死亡率以评价其对实验损伤的耐受性.1×104/孔B16-F10-luc-G5细胞按1∶2梯度稀释至0.78×102/孔,加入底物荧光素后检测其生物发光特性.Babl/C和C57 bl/6雄性小鼠各10只接种该细胞,目测肿瘤生长速度和活体成像监测Babl/C小鼠移植瘤生长动态以评价其成瘤特性.结果：B16-Fl0-luc-G5细胞生长动态符合典型B16-F10细胞特性,无自发及激发荧光.B16-F10-luc-G5细胞冻存、漂浮细胞及对数生长期细胞消化后死亡率分别为23.8％、35.8％和4.8％.B16-F10-luc-G5细胞数与实测平均光子数之间存在线性回归关系,检测光子数可反映细胞数目.两组小鼠移植成瘤率均为100％,平均肿瘤出现时间差异显著（t =9.05,P＜0.05）,移植瘤病理符合B16黑色素瘤典型生长特点;活体成像监测可灵敏监测移植瘤生长动态.结论：B16-F10-luc-G5细胞具有生长快、对各种实验操作耐受性好、标记生物发光基因易追踪等优点,且其一般特性与B16-F10细胞基本相同,是肿瘤学研究良好的实验材料.     

Anti-tumor effect of adenovirus-mediated gene transfer of pigment epithelium-derived factor on mouse B16-F10 melanoma

Background

Angiogenesis plays an important role in tumor growth, invasion, and eventually metastasis. Antiangiogenic strategies have been proven to be a promising approach for clinical therapy for a variety of tumors. As a potent inhibitor of tumor angiogenesis, pigment epithelium-derived factor (PEDF) has recently been studied and used as an anticancer agent in several tumor models.

Methods

A recombined adenovirus carrying PEDF gene (Ad-PEDF) was prepared, and its expression by infected cells and in treated animals was confirmed with Western blotting and ELISA, respectively. Its activity for inhibiting human umbilical vein endothelial cell (HUVEC) proliferation was tested using the MTT assay. C57BL/6 mice bearing B16-F10 melanoma were treated with i.v. administration of 5 × 10⁸ IU/mouse Ad-PEDF, or 5 × 10⁸ IU/mouse Ad-Null, or normal saline (NS), every 3 days for a total of 4 times. Tumor volume and survival time were recorded. TUNEL, CD31 and H&E stainings of tumor tissue were conducted to examine apoptosis, microvessel density and histological morphology changes. Antiangiogenesis was determined by the alginate-encapsulated tumor cell assay.

Results

The recombinant PEDF adenovirus is able to transfer the PEDF gene to infected cells and successfully produce secretory PEDF protein, which exhibits potent inhibitory effects on HUVEC proliferation. Through inhibiting angiogenesis, reducing MVD and increasing apoptosis, Ad-PEDF treatment reduced tumor volume and prolonged survival times of mouse bearing B16-F10 melanoma.

Conclusion

Our data indicate that Ad-PEDF may provide an effective approach to inhibit mouse B16-F10 melanoma growth.     

Pentoxifylline modulates cell surface integrin expression and integrin mediated adhesion of B16F10 cells to extracellular matrix components

Our previous studies demonstrated that Pentoxifylline (PTX), a phosphodiesterase inhibitor, could inhibit the lung homing of B16-F10 melanoma cells in C57BL/6 mice. In this study we have looked at the effect of PTX on cell surface integrin expression and integrin mediated adhesion of B16-F10 melanoma cells. B16-F10 cells treated with PTX when injected through the tail vein of mice showed a 75% reduction in pulmonary nodules as compared to control untreated cells. PTX brought about a significant reduction in the integrin mediated adhesion of F10 cells to Fibronectin and Vitronectin (58.75% +/- 3.4 S.E and 60% +/- 1.7 S.E respectively if control was considered as 100%). This inhibition in adhesion was evident up to four hours only and treatment for 24 hours brought about an increase in adhesion (135.5% +/- 0.5 S.E). Flow cytometric analysis showed higher surface expressions of alphav, alpha5 and alphaIIb integrin subunits in B16-F10 as compared to the low metastatic cell line B16-F1 suggesting a role for these integrins in determining the metastatic potential. PTX brought about a significant decrease in the cell surface expression of alpha5, alphaIIb and beta1 integrin subunits but not that of the alphav subunit on B16-F10 cells. PTX also brought about a reduction in the total cellular protein levels of beta1 and alphav integrin subunits. Various isoforms of Protein Kinase C (PKC) has been shown to regulate integrin expression, localization and activity. Hence we looked at the effect of PTX on total cellular PKC activity. PTX brought about a significant reduction in total cellular PKC activity (82.66 +/- 0.593). Collectively our results indicate that the antimetastatic action of PTX is mediated, at least in part through its effects on adhesion and the surface expression of specific integrin receptors.     

Antitumor activity of monomethoxy poly(ethylene glycol)-poly (ε-caprolactone) micelle-encapsulated doxorubicin against mouse melanoma

Doxorubicin (Dox) is one of the most commonly used and highly effective antineoplastic agents, but the clinical application of this broad spectrum drug is largely hampered by its poor stability and serious toxicity to normal tissues. Hence, it is essential to improve the therapeutic effect and decrease the systematic toxicity for the administration of doxorubicin. In our study, doxorubicin was incorporated into monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelle by a self-assembly method. The cytotoxicity and cellular uptake efficiency of Dox-loaded MPEG-PCL (Dox/MPEG-PCL) micelle against B16-F10 murine melanoma cells was examined by the methylthiazoltetrazolium (MTT) test and flow cytometry. The antitumor activity of Dox/MPEG-PCL was evaluated in C57BL/6 mice injected subcutaneously with B16-F10 cells. Toxicity was evaluated in tumor-free mice. Meanwhile, tumor proliferation, intratumoal angiogenesis and apoptotic cells were evaluated by PCNA, CD31 staining and TUNEL assay, respectively. Encapsulation of doxorubicin in MPEG-PCL micelle improved the cytotoxicity of doxorubicin and enhanced its cellular uptake on B16-F10 cell in vitro. Administration of Dox/MPEG-PCL micelle resulted in significant inhibition (75% maximum inhibition relative to controls) in the growth of B16-F10 tumor xenografts and prolonged the survival of the treated mice (P<0.05). These anti-tumor responses were associated with marked increase of tumor apoptosis and notable reduction of cell proliferation and intratumoral microvessel density (P<0.05). The system toxicity also decreased in the Dox/MPEG-PCL group compared with free doxorubicin group. Our data indicate that the encapsulation of doxorubicin in MPEG-PCL micelle improved the anti-tumor activity in vivo without conspicuous systemic toxic effects.     

Reduced tumorigenicity of B16-F10 mouse melanoma cells transfected with mycobacterial antigen 85A

Immunotherapy based on the administration of the mycobacterium bacillus Calmette-Guerin has been successfully used in the treatment of in situ transitional cell bladder cancer, and may be applicable to the treatment of cutaneous malignant melanoma. Antigen 85A (Ag85A) and heat shock protein 65 kDa (hsp65) are major secreted proteins of Mycobacterium species and potent stimulators of cell-mediated immunity. This study evaluated the ability of Ag85A and hsp65 gene transfection to limit tumor growth by B16-F10 mouse melanoma cells. Immunoblotting confirmed protein expression and secretion by B16-F10 cells that were transiently transfected with plasmid DNA containing the Ag85A or hsp65 gene. Groups of syngeneic C57BL/6 mice were injected subcutaneously with 1x10(5) untransfected B16-F10 cells or B16-F10 cells transiently transfected with either empty vector or vector containing the Ag85A or hsp65 gene. Ag85A-expressing B16-F10 cells exhibited a dramatic 76% reduction (p<0.05, Mann-Whitney U test) in tumor weight in comparison to empty vector controls at 14 days post-inoculation. In contrast, hsp65-transfected B16-F10 cells did not show any change in tumorigenicity. Decreased tumorigenicity by Ag85A-transfected B16-F10 cells was not due to a reduced ability of Ag85A-transfected B16-F10 cells to proliferate since both mock- and Ag85A-transfected B16-F10 cells showed increased in vitro proliferation in comparison to untransfected cells. Hematoxylin and eosin staining revealed that Ag85A-transfected B16-F10 tumors contained an inflammatory leukocyte infiltrate that was not present in hsp65-transfected tumors. Reduced tumor progression by Ag85A-transfected B16-F10 melanoma cells suggests that immunotherapy based on the transient induction of Ag85A expression may be an effective approach for the treatment of cutaneous malignant melanoma.     

Anti-tumor activity of N-trimethyl chitosan-encapsulated camptothecin in a mouse melanoma model

Background

Camptothecin (CPT) has recently attracted increasing attention as a promising anticancer agent for a variety of tumors. But the clinical application is largely hampered by its extreme water insolubility and unpredictable side effect. It is essential to establish an efficient and safe protocol for the administration of CPT versus melanoma.

Methods

Camptothecin was encapsulated with N-trimethyl chitosan (CPT-TMC) through microprecipitation and sonication. Its inhibition effect on B16-F10 cell proliferation and induction of apoptosis was evaluated by MTT assay and flow cytometric analysis in vitro. The anti-tumor activity of CPT-TMC was evaluated in C57BL/6 mice bearing B16-F10 melanoma. Tumor volume, tumor weight and survival time were recorded. Assessment of apoptotic cells within tumor tissue was performed by TUNEL assay. Antiangiogenesis and antiproliferation effects of CPT-TMC in vivo were conducted via CD31 and PCNA immunohistochemistry, respectively.

Results

CPT-TMC efficiently inhibited B16-F10 cells proliferation and increased apoptosis in vitro. Experiment group showed significant inhibition compared with free CPT-treated group (81.3% vs. 56.9%) in the growth of B16-F10 melanoma xenografts and prolonged the survival time of the treated mice (P < 0.05). Decreased cell proliferation, increased tumor apoptosis as well as a reduction in angiogenesis were observed.

Conclusions

Our data suggest that N-trimethyl chitosan-encapsulated camptothecin is superior to free CPT by overcoming its insolubility and finally raises the potential of its application in melanoma therapy.     

Inhibition of hepatocellular carcinomas in vitro and hepatic metastases in vivo in mice by the histone deacetylase inhibitor HA-But.

PURPOSE: The purpose is to evaluate the CD44-mediated cellular targeting of HA-But, a hyaluronic acid esterified with butyric acid (But) residues, to hepatocellular carcinoma cell lines in vitro and to hepatic tumor metastases in vivo. EXPERIMENTAL DESIGN: In vitro, the CD44-dependent cytotoxicity in two human hepatocellular carcinoma cell lines (HepB3 and HepG2) with high and low CD44 expression was investigated; in vivo, the effect on liver metastases originating from intrasplenic implants of Lewis lung carcinoma (LL3) or B16-F10 melanoma in mice was compared with the pharmacokinetics of organ and tissue distribution using different routes of administration. RESULTS: HepB3 and HepG2 cell lines showed different expression of CD44 (78 and 18%, respectively), which resulted in a CD44-dependent HA-But inhibitory effect as demonstrated also by the uptake analysis performed using radiolabeled HA-But ((99m)Tc-HA-But). Pharmacokinetic studies showed different rates of (99m)Tc-HA-But distribution according to the route of administration (i.v., i.p., or s.c.): very fast (a few minutes) after i.v. treatment, with substantial accumulation in the liver and spleen; relatively slow after i.p. or s.c. treatment, with marked persistence of the drug at the site of injection. The effect of s.c. and i.p. treatment with HA-But on liver metastases originating from intrasplenic implants of LL3 carcinoma or B16-F10 melanoma (both CD44-positive: 68 and 87%, respectively), resulted in 87 and 100% metastases-free animals, respectively (regardless of the route of administration), and a significant prolongation of the life expectancy compared with control groups. CONCLUSIONS: HA-But tends to concentrate in the liver and spleen and appears to be a promising new drug for the treatment of intrahepatic tumor lesions.     

结直肠癌组织中肿瘤干细胞标志物CD44与周期蛋白p27关系及意义

目的：了解结直肠癌组织中CD44、p27表达的关系。方法：采用组织芯片检测、免疫组织化学和双重免疫组织化学染色技术检测61例结直肠癌组织中CD44、p27的表达。结果：在结直肠癌组织中,CD44与p27蛋白的表达与病理分级无明显相关性,CD44＋细胞数约占癌细胞数的0.1%-55%（30.9±19.29）,p27^＋细胞数约占癌细胞数0.1%-35%（20.9±12.21）,p27蛋白在癌组织中表达强弱不一,强阳性细胞（p27high）呈灶性或单个散在分布,约占癌细胞总数的0.1%-15%,CD44^＋细胞大多数p27^-（90%以上）,p27＋的癌细胞也极少表达CD44,CD44^＋/p27high占CD44＋细胞数的0.1%-5%（3.12±1.18）。结论：周期蛋白p27,G0/G1期（即静止期）细胞核含量最高。本实验证实只有极少数CD44＋细胞呈p27蛋白强阳性（p27high）,CD44^＋/p27high的细胞多处于静止期,可能为肿瘤干细胞,p27分子可作为进一步筛选肿瘤干细胞的一个重要标记物。     

Extraction of immunogenic and suppressogenic antigens from variants of B16 melanoma exhibiting low or high metastatic potentials

This investigation examined the effect of soluble antigen prophylaxis on s.c. and metastatic growth of B16 variants which demonstrated either a low or high propensity to colonize the lungs (B16-F1 and B16-F10, respectively) of syngeneic C57BL/6J mice. The two variants share a tumor-associated antigen, since immunization with crude butanol extracts (CBEs) of B16-F1 cells protected hosts against s.c. challenge with either B16-F1 or B16-F10 cells. CBE from B16-F10 (CBE-F10) were unable to engender a measurable immune response against s.c. challenge with either tumor variant. Pretreatment with 100 to 300 micrograms CBE from F1 cells was also effective in reducing the outgrowth of experimentally induced B16-F1 or B16-F10 pulmonary foci. However, mice immunized with 100 micrograms CBE-F10 bore significantly more pulmonary tumors than did phosphate-buffered saline-treated controls. The enhancing and protective activities were specific for the B16 tumor and could be adoptively transferred 24 hr prior to tumor challenge by i.p. injection of 5 X 10(7) spleen cells from CBE-immunized mice. The enhancing activity in the CBE-F10 immune spleen cell population was abolished by depletion of adherent cells onto plastic. Adoptive transfer of the CBE-F10-immune adherent cell population did not affect metastatic growth, suggesting that, in this experimental system, the adherent population was not an efferent suppressor and could not recruit host elements to effect suppression. Indeed, spleen cell-mixing experiments demonstrated that only immune adherent cells combined with immune nonadherent cells could partially reconstitute the tumor growth-enhancing potential of the unfractionated CBE-F10-immune spleen cell population.     

Synthetic peptides inhibit adhesion of human tumor cells to extracellular matrix proteins

Human tumor cell progression and metastasis are partially dependent on the ability of a tumor cell to adhere to the proteins of the extracellular matrix (ECM) and survive at the distant location. Six novel D-amino acid-containing peptides were analyzed for their ability to adhere to human prostate tumor cells, support tumor cell adhesion, and inhibit tumor cell adhesion to ECM proteins or human dermal fibroblasts. Of these, two peptides called RZ-3 (kmviywkag) and HYD-1 (kikmviswkg) bound to tumor cell surfaces and compared favorably with the previously reported AG-73 (RKRLQVQLSIRT) L-amino acid peptide, as determined by fluorescence-activated cell sorting analysis. A scrambled peptide derivative of HYD-1, called HYDS-1 (wiksmkivkg), was not active. The RZ-3, HYD-1, and AG-73 peptides supported maximal cancer cell adhesion at 5 microg, 10 microg, and 50 microg/well, respectively. The ECM proteins fibronectin, laminin 1, and collagen IV supported maximal cell adhesion at 1 microg, >10 microg, and 50 microg/well, respectively. Prostate tumor cell adhesion to immobilized RZ-3 and HYD-1 peptides was inhibited by alpha2-6- and beta1-integrin-blocking antibodies. Conversely, tumor cell adhesion to a beta1-integrin-specific antibody was blocked by both RZ-3 and HYD-1. Epithelial cell adhesion to dermal fibroblasts was inhibited by HYD-1 and unaffected by the scrambled peptide, HYDS-1. Cell adhesion to immobilized peptides was unaffected by EDTA. The soluble RZ-3 and HYD-1 peptides inhibited tumor cell adhesion to each of the immobilized four ECM proteins (1.0 microg/well) in a time- and concentration-dependent manner. The IC(50) of the RZ-3 peptide for blocking adhesion to fibronectin, laminin 1, laminin 5, and collagen IV was 2.4 microg, 1.8 microg, 4.6 microg, and 2.8 microg/well, respectively. The IC(50) of the HYD-1 peptide for blocking adhesion to fibronectin, laminin 1, laminin 5, and collagen IV was 6.9 microg, 5.7 microg, >10 microg, and 6.2 microg/well, respectively. Taken together, these results indicate that RZ-3 and HYD-1 are biologically active D-amino acid-containing peptides that can themselves support tumor cell adhesion and can inhibit tumor cell adhesion to immobilized ECM proteins or dermal fibroblasts.     

The fatty acid synthase inhibitor orlistat reduces experimental metastases and angiogenesis in B16-F10 melanomas

Background:Fatty acid synthase (FASN) is overexpressed and associated with poor prognosis in several human cancers. Here, we investigate the effect of FASN inhibitors on the metastatic spread and angiogenesis in experimental melanomas and cultured melanoma cells.Methods:The lung colonisation assay and cutaneous melanomas were performed by the inoculation of mouse melanoma B16-F10 cells in C57BL6 mice. Blood vessel endothelial cells (RAEC and HUVEC) were applied to determine cell proliferation, apoptosis, and the formation of capillary-like structures. Vascular endothelial growth factor A (VEGFA) expression was evaluated by quantitative RT-PCR and ELISA in B16-F10, human melanoma (SK-MEL-25), and human oral squamous carcinoma (SCC-9) cells. Conditioned media from these cancer cell lines were used to study the effects of FASN inhibitors on endothelial cells.Results:B16-F10 melanoma-induced metastases and angiogenesis were significantly reduced in orlistat-treated mice. Fatty acid synthase inhibitors reduced the viability, proliferation, and the formation of capillary-like structures by RAEC cells, as well as the tumour cell-mediated formation of HUVEC capillary-like structures. Cerulenin and orlistat stimulated the production of total VEGFA in B16-F10, SK-MEL-25, and SCC-9 cells. Both drugs also enhanced VEGFA(121), (165), (189,) and (165b) in SK-MEL-25 and SCC-9 cells.Conclusion:FASN inhibitors reduce metastasis and tumour-induced angiogenesis in experimental melanomas, and differentially modulate VEGFA expression in B16-F10 cells.     

An embryo-specific expressing TGF-β family protein,growth-differentiation factor 3 (GDF3), augments progression of B16 melanoma

Malignant tumor cells often express embryonic antigens which share the expression with embryonic stem (ES) cells. The embryonic antigens are usually encoded by ES cell-specific genes, a number of which are associated with tumorigenesis and/or tumor progression. We examined the expression of ES cell-specific genes in the mouse B16 melanoma cell line to identify the factors promoting tumorigenesis. We found that endogenous growth-differentiation factor 3 (GDF3) expression was induced in implant B16 tumor during tumor progression in syngenic C57BL/6 mice. B16 F10, a subline with a high metastatic potential, continuously expressed GDF3 while low metastatic B16 F1 expressed comparatively decreased levels of GDF3. Overexpression of GDF3 promoted growth of implanted melanoma B16 F1 and F10 in syngenic mice. Ectopic expression of GDF3 was accompanied by an increased level of production of CD24/CD44. Such a profile was reported to be characteristic of melanoma stem cell-like cells. GDF3 expression was observed in embryonal carcinomas, primary testicular germ cell tumors, seminomas and breast carcinomas. However, the role of GDF3 in these cancers remains undetermined. Overexpression of GDF3 did not affect the growth of mouse hepatoma high or low metastatic sublines G5 or G1, both of which do not express GDF3. Since GDF3-driven CD24 acts as a receptor for endogenous innate immune ligands that modulate cell proliferation, CD24 is an effective determinant of tumorigenesis in malignant cell transformation. Finally, our results support the view that GDF3 has the ability to induce progression of CD24-inducible melanoma in mice.     

Effect of retinoic acid on tumor-mediated immunologic alterations in mice bearing a variant of the B16 melanoma

This investigation examined the effect of retinoic acid on tumor progression and immunological status of mice bearing the B16-F10 melanoma (previously selected for high lung-colonizing capacity). Tumor cells were implanted s.c. in syngeneic C57BL/6 mice, half of which were treated with beta-all trans retinoic acid (RA). Although RA failed to exhibit direct toxicity on this variant at the concentration used, the immunologic aberrations induced by the tumors were diminished by i.p. RA administration (at 45 micrograms twice/week for 3 weeks). In mice bearing B16-F10 tumors, tumor burdens were decreased from 2.9% of body weight to 1.6%. The mitogenic responses of splenic lymphocytes to concanavalin A (ConA) were increased in tumor-bearing mice following this RA treatment. The presence of these tumor cells decreased the absolute number of CD4- and CD8-positive splenic lymphocytes. Following RA treatment, the CD8-positive population was increased in tumor-bearing mice, while the CD4+ population was not significantly altered. Since previous studies indicated that plasma membrane fragments (or vesicles) could alter lymphocyte distributions and proliferative capacities, the in vitro shedding of membrane fragments from B16-F10 tumor cells was assayed and observed to be decreased after continuous treatment of cultures with 10(-6) M RA for 21 days. Membrane shedding from B16-F10 cells was inhibited by 48.5% following RA treatment. Based on these in vivo and in vitro results, we suggest that RA treatment may diminish tumor growth by decreasing tumor-induced immunosuppressive events.     

Effect of retinoic acid on integrin receptors of B16F10 melanoma cells

The intriguing problem of metastasis requires the spreading of metastatic cells through the basement membrane barrier. The interaction of the basement membrane with the metastatic cell is a cell surface activity involving the function of integrin receptors. Integrins are a group of alpha,beta heterodimeric proteins responsible for transducing intracellular signals on binding to the extracellular matrix proteins present in the basement membrane. To understand the role of integrin receptors in tumor metastasis, the cell surface receptor functions were modulated by All Trans Retinoic Acid (ATRA) treatment in B16F10 tumor cells. Our experimental results clearly indicate that All Trans Retinoic Acid (ATRA) inhibit metastatic potential of highly metastatic B16F10 melanoma cells by 1) downregulating the cell surface integrin receptors against ECM proteins specially laminin and vitronectin and 2) by inhibiting the 72 kd collagenase activity.     

Basement membrane and the SIKVAV laminin-derived peptide promote tumor growth and metastases

Summary Laminin, the major glycoprotein component of basement membrane, promotes the malignant phenotype. Cells which are adherent to laminin are more malignant than the non-adherent cells and in certain tumor cells, the number of laminin receptors is positively correlated with malignancy. Laminin also increases collagenase IV activity, an enzyme demonstrated to be critical for tumor spread. A site on laminin, containing the amino acid sequence SIKVAV, has been identified which when injected intravenously with B16F10 melanoma cells, causes an increase in the number of colonies on the surface of the lungs. This peptide does not affect tumor cell arrest in the vasculature or the immune system. It does promote angiogenesis in various in vitro and in vivo models, thereby facilitating tumor cell survival.When a complex mixture of laminin-enriched basement membrane components (Matrigel) is coinjected with tumor cells subcutaneously, tumor incidence and growth increases. Various tumor cell lines and primary isolates, which previously could not form tumors in mice, can be induced to grow rapidly in the presence of Matrigel. Slowly growing tumors or arrested tumors can also be induced to grow more quickly with additional injections of Matrigel. When an SIKVAV-containing synthetic peptide is coinjected with B16F10 tumor cells and Matrigel subcutaneously in mice, larger tumors are formed than that observed with either Matrigel or cells alone. Such studies define the role of laminin in tumor growth and spread and generate new models for studying therapeutic agents. Of particular interest is the ability to grow primary isolates which generally do not grow in mice.