Lack of transforming growth factor-β signaling promotes collective cancer cell invasion through tumor-stromal crosstalk

ABSTRACT: INTRODUCTION: Transforming growth factor beta (TGF-β) has a dual role during tumor progression, initially as a suppressor and then as a promoter. Epithelial TGF-β signaling regulates fibroblast recruitment and activation. Concurrently, TGF-β signaling in stromal fibroblasts suppresses tumorigenesis in adjacent epithelia, while its ablation potentiates tumor formation. Much is known about the contribution of TGF-β signaling to tumorigenesis, yet the role of TGF-β in epithelial-stromal migration during tumor progression is poorly understood. We hypothesize that TGF-β is a critical regulator of tumor-stromal interactions that promote mammary tumor cell migration and invasion. METHODS: Fluorescently labeled murine mammary carcinoma cells, isolated from either MMTV-PyVmT transforming growth factor-beta receptor II knockout (TβRII KO) or TβRIIfl/fl control mice, were combined with mammary fibroblasts and xenografted onto the chicken embryo chorioallantoic membrane. These combinatorial xenografts were used as a model to study epithelial-stromal crosstalk. Intravital imaging of migration was monitored ex ovo, and metastasis was investigated in ovo. Epithelial RNA from in ovo tumors was isolated by laser capture microdissection and analyzed to identify gene expression changes in response to TGF-β signaling loss. RESULTS: Intravital microscopy of xenografts revealed that mammary fibroblasts promoted two migratory phenotypes dependent on epithelial TGF-β signaling: single cell/strand migration or collective migration. At epithelial-stromal boundaries, single cell/strand migration of TβRIIfl/fl carcinoma cells was characterized by expression of α-smooth muscle actin and vimentin, while collective migration of TβRII KO carcinoma cells was identified by E-cadherin+/p120+/β-catenin+ clusters. TβRII KO tumors also exhibited a twofold greater metastasis than TβRIIfl/fl tumors, attributed to enhanced extravasation ability. In TβRII KO tumor epithelium compared with TβRIIfl/fl epithelium, Igfbp4 and Tspan13 expression was upregulated while Col1α2, Bmp7, Gng11, Vcan, Tmeff1, and Dsc2 expression was downregulated. Immunoblotting and quantitative PCR analyses on cultured cells validated these targets and correlated Tmeff1 expression with disease progression of TGF-β-insensitive mammary cancer. CONCLUSION: Fibroblast-stimulated carcinoma cells utilize TGF-β signaling to drive single cell/strand migration but migrate collectively in the absence of TGF-β signaling. These migration patterns involve the signaling regulation of several epithelial-to-mesenchymal transition pathways. Our findings concerning TGF-β signaling in epithelial-stromal interactions are important in identifying migratory mechanisms that can be targeted as recourse for breast cancer treatment.     

Differences in chemotaxis to fibronectin in weakly and highly metastatic tumor cells.

We have examined the chemotactic ability of tumor cell lines with different metastatic potential to plasma fibronectin in Transwell chamber assay. Human renal carcinoma cells with highly metastatic potential, SN12 C-2, chemotactically migrated to fibronectin (10 micrograms/ml) about three-fold more strongly than weakly metastatic SN12 C-4 cells. Similarly, murine melanoma B16-BL6 cells (highly metastatic) showed higher motility to soluble fibronectin in comparison with weakly metastatic B16-F1 cells. Anti-VLA-alpha 3 and beta 1 antibodies potently blocked the chemotaxis of both highly and weakly metastatic cells (SN12 C-2 and C-4) to fibronectin. This implies that the migration of both C-2 and C-4 cells to fibronectin is basically mediated by VLA-3 receptor. In contrast, the anti-VLA-alpha 5 antibody and RGDS peptide significantly inhibited the chemotaxis of SN12 C-2 cells to fibronectin, but did not affect weakly metastatic SN12 C-4 cells. These results suggest that the chemotactic ability to fibronectin positively correlates with the metastatic potential in SN12 and B16 cell lines, and that VLA-5 receptor is concerned in the motility of highly metastatic SN12 C-2 cells to soluble fibronectin.     

Induction of autocrine factor inhibiting cell motility from murine B16-BL6 melanoma cells by alpha-melanocyte stimulating hormone

We have previously reported that neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) successfully inhibited Matrigel invasion and haptotactic migration of B16-BL6 melanoma cells towards both fibronectin and laminin without affecting their growth. In the present study, we investigated the inhibitory mechanism of tumor cell motility by alpha-MSH. Alpha-MSH significantly blocked the autocrine motility factor (AMF)-enhanced cell motility. However, alpha-MSH did neither prevent the secretion of AMF from B16-BL6 cells nor alter the expression level of AMF receptor (gp78). On the other hand, alpha-MSH induced the secretion of the motility inhibitory factor(s) from B16-BL6 cells in a concentration- and time-dependent manner. The induction of the motility inhibitor(s) was proportional to increasing levels of intracellular cAMP induced by alpha-MSH as well as forskolin, and the activity was abolished by an adenylate cyclase inhibitor, 2',5'-dideoxyadenosine (DDA). The motility-inhibiting activity in conditioned medium (CM) from alpha-MSH-treated B16-BL6 cells was found to have a m.w. below 3 kDa after fractionation. This activity was abolished by boiling but insensitive to trypsin. The treatment of tumor cells with cycloheximide reduced the activity in alpha-MSH-stimulated CM. Our results suggest that alpha-MSH inhibited the motility of B16-BL6 cells through induction of autocrine factor(s).     

Interaction between non-small-cell lung cancer cells and fibroblasts via enhancement of TGF-β signaling by IL-6

Introduction

Fibroblasts are key components of the tumor microenvironment. We clarified the role of transforming growth factor (TGF)-β and interleukin (IL)-6 in the interaction between fibroblasts and non-small-cell lung cancer (NSCLC) cells.

Methods

We used NSCLC cells (A549, NCI-H358) and normal human lung fibroblast (NHLF) cells to evaluate phenotypic changes in the presence of human IL-6, TGF-β1, and conditioned media (CM) from these cells. Possible pathways were evaluated with SB431542, a TGF-β receptor inhibitor, or an anti-human IL-6 receptor neutralizing antibody (IL-6R-Ab).

Results

A549 and NCI-H358 cells incubated with IL-6 (50 ng/mL) and TGF-β1 (2 ng/mL) showed significantly increased epithelial–mesenchymal transition (EMT) signaling compared to those treated with TGF-β1 alone. Furthermore, NHLF cells were synergistically activated by IL-6 and TGF-β1. IL-6 increased the expression of TGF-β type I receptors on the surface of A549, NCI-H358 and NHLF cells and enhanced TGF-β signaling. TGF-β1 induced phenotypic changes were attenuated by IL-6R-Ab. NHLF cells were activated and A549 cells showed induction of EMT in response to CM from the other cell type. These activities were attenuated by SB431542 or IL-6R-Ab, suggesting that interplay between NSCLC cells and NHLF may lead to increased EMT signaling in NSCLC cells and activation of NHLF cells through TGF-β and IL-6 signaling. Subcutaneous co-injection of A549 and NHLF cells into mice resulted in a high rate of tumor formation compared with injection of A549 cells without NHLF cells. SB431542 or IL-6R-Ab also attenuated the tumor formation enhanced by co-injection of the two cell types.

Conclusion

IL-6 enhanced epithelial cell EMT and stimulated tumor progression by enhancing TGF-β signaling. IL-6 and TGF-β may play a contributing role in maintenance of the paracrine loop between these two cytokines in the communication between fibroblasts and NSCLC cells for tumor progression.     

Paracrine recruitment and activation of fibroblasts by c-Myc expressing breast epithelial cells through the IGFs/IGF-1R axis

Fibroblasts are among the most abundant stromal cells in the tumor microenvironment (TME), progressively differentiating into activated, motile, myofibroblast-like, protumorigenic cells referred to as Cancer-Associated Fibroblasts (CAFs). To investigate the mechanisms by which epithelial cells direct this transition, the early stages of tumorigenesis were exemplified by indirect cocultures of WI-38 or human primary breast cancer fibroblasts with human mammary epithelial cells expressing an inducible c-Myc oncogene (MCF10A-MycER). After c-Myc activation, the conditioned medium (CM) of MCF10A-MycER cells significantly enhanced fibroblast activation and mobilization. As this was accompanied by decreased insulin-like growth factor binding protein-6 (IGFBP-6) and increased insulin-like growth factor-1 and IGF-II (IGF-I, IGF-II) in the CM, IGFs were investigated as key chemotactic factors. Silencing IGFBP-6 or IGF-I or IGF-II expression in epithelial cells or blocking Insulin-like growth factor 1 receptor (IGF-1R) activity on fibroblasts significantly altered fibroblast mobilization. Exposure of WI-38 fibroblasts to CM from induced MCF10A-MycER cells or to IGF-II upregulated FAK phosphorylation on Tyr³⁹⁷, as well as the expression of α-smooth muscle actin (α-SMA), features associated with CAF phenotype and increased cell migratory/invasive behavior. In three-dimensional (3D)-organotypic assays, WI-38 or human primary fibroblasts, preactivated with either CM from MCF10A-MycER cells or IGFs, resulted in a permissive TME that enabled nontransformed MCF10A matrix invasion. This effect was abolished by inhibiting IGF-1R activity. Thus, breast epithelial cell oncogenic activation and stromal fibroblast transition to CAFs are linked through the IGFs/IGF-1R axis, which directly promotes TME remodeling and increases tumor invasion.     

Tumor-derived transforming growth factor-β1 and interleukin-6 are chemotactic for lymphokine-activated killer cells

Adherent lymphokine-activated killer (A-LAK) cells are purified IL-2 activated natural killer (NK) cells with potent anti-tumor cytotoxic activity. They have been used in the adoptive immunotherapy of metastatic canters. However, it has been shown that intravenously transferred LAK cells have a poor horning capacity to tumor sites. For the present study, the effects of tumor-derived factors on the in vitro migratory capacity of A-LAK cells was investigated. In a micropore migration assay the conditioned medium from 3LL Lewis lung carcinoma cell cultures was found to exert a strong chemotactic, but not chemokinetic effect on A-LAK cells. This effect was partially inhibited by neutralizing antibodies against the cytokines TGF-β1 and IL-6. A combination of the 2 antibodies completely suppressed the chemotactic activity of tumor-cell-conditioned medium. Purified TGF-β1 and recombinant IL-6 were chemotactic for A-LAK cells. Biological activities of both cytokines were detectable in the tumor-cell-conditioned medium. The in vivo relevance of these findings, with respect to tissue infiltration of NK cells and LAK cells in inflammation or cancer, remains to be elucidated.     

Elevated expression of angiomodulin (AGM/IGFBP-rP1) in tumor stroma and its roles in fibroblast activation

Angiomodulin (AGM/IGFBP-rP1), a glycoprotein of about 30 kDa, is overexpressed in tumor vasculature as well as some human cancer cell lines, but it has been suggested to be a tumor suppressor. To elucidate roles of angiomodulin (AGM) in tumor progression, we here examined distribution of AGM in three types of human cancer tissues by immunohistochemistry. The results showed that AGM was overexpressed in the stroma as well as the vasculature surrounding tumor cells in the human cancer tissues. AGM and α-smooth muscle actin (α-SMA) as an activated fibroblast marker were often colocalized in cancer-associated fibroblasts (CAFs). In vitro analysis indicated that transforming growth factor (TGF)-β1 might be an important inducer of AGM in normal human fibroblasts. AGM strongly stimulated the expression of fibronectin and weakly that of α-SMA in normal fibroblasts. AGM significantly stimulated the proliferation and migration of fibroblasts. The AGM-induced expression of fibronectin and α-SMA was blocked by a TGF-β signal inhibitor but neither the stimulation of cell growth nor migration. These results imply that AGM activates normal fibroblasts by TGF-β-dependent and independent mechanisms. These findings also suggest that AGM and TGF-β1 cooperatively or complementarily contribute to the stromal activation and connective tissue formation in human cancer tissues, contributing to tumor progression.     

Ultraviolet exposure of melanoma cells induces fibroblast activation protein-α in fibroblasts: Implications for melanoma invasion

Fibroblast activation protein-α (FAP-α) promotes tumor growth and cell invasiveness through extracellular matrix degradation. How ultraviolet radiation (UVR), the major risk factor for malignant melanoma, influences the expression of FAP-α is unknown. We examined the effect of UVR on FAP-α expression in melanocytes, keratinocytes and fibroblasts from the skin and in melanoma cells. UVR induces upregulation of FAP-α in fibroblasts, melanocytes and primary melanoma cells (PM) whereas keratinocytes and metastatic melanoma cells remained FAP-α negative. UVA and UVB stimulated FAP-α-driven migration and invasion in fibroblasts, melanocytes and PM. In co-culture systems UVR of melanocytes, PM and cells from regional metastases upregulated FAP-α in fibroblasts but only supernatants from non-irradiated PM were able to induce FAP-α in fibroblasts. Further, UV-radiated melanocytes and PM significantly increased FAP-α expression in fibroblasts through secretory crosstalk via Wnt5a, PDGF-BB and TGF-β1. Moreover, UV radiated melanocytes and PM increased collagen I invasion and migration of fibroblasts. The FAP-α/DPPIV inhibitor Gly-ProP(OPh)2 significantly decreased this response implicating FAP-α/DPPIV as an important protein complex in cell migration and invasion. These experiments suggest a functional association between UVR and FAP-α expression in fibroblasts, melanocytes and melanoma cells implicating that UVR of malignant melanoma converts fibroblasts into FAP-α expressing and ECM degrading fibroblasts thus facilitating invasion and migration. The secretory crosstalk between melanoma and tumor surrounding fibroblasts is mediated via PDGF-BB, TGF-β1 and Wnt5a and these factors should be evaluated as targets to reduce FAP-α activity and prevent early melanoma dissemination.     

Tumor cell invasion is promoted by interstitial flow-induced matrix priming by stromal fibroblasts

Interstitial flow emanates from tumors into the microenvironment where it promotes tumor cell invasion. Fibroblasts are key constituents of the tumor stroma that modulate the mechanical environment by matrix remodeling and contraction. Here, we explore how interstitial fluid flow affects fibroblast-tumor cell interactions. Using a 3-dimensional invasion assay and MDA-MB-435S cells cocultured with dermal fibroblasts in a collagen matrix, we showed a synergistic enhancement of tumor cell invasion by fibroblasts in the presence of interstitial flow. Interstitial flow also drove transforming growth factor (TGF)-β1 and collagenase-dependent fibroblast migration, consistent with previously described mechanisms in which flow promotes invasion through autologous chemotaxis and increased motility. Concurrently, migrating fibroblasts enhanced tumor cell invasion by matrix priming via Rho-mediated contraction. We propose a model in which interstitial flow promotes fibroblast migration through increased TGF-β1 activation and collagen degradation, positioning fibroblasts to locally reorganize collagen fibers via Rho-dependent contractility, in turn enhancing tumor cell invasion via mechanotactic cues. This represents a novel mechanism in which interstitial flow causes fibroblast-mediated stromal remodeling that facilitates tumor invasion.     

Soluble fibronectin promotes migration of oral squamous-cell carcinoma cells

We have shown that a fibronectin (FN) matrix is required for the organization of tenascin-C (TN-C) matrices by peritumor fibroblasts (PTF) cultured from tissue surrounding oral squamous-cell carcinoma (SCC). In the present study, we detected alternatively spliced FN containing both the EDA and EDB domains decorating the reactive stroma adjacent to the invading tumor nests in oral SCC biopsies. In vitro, PTF cells organized an extensive FN matrix rich in the EDA domain and containing a small amount of EDB. In contrast, normal human fibroblasts deposited a FN matrix which expressed only the EDA domain. PTF-conditioned medium (CM), shown to enhance migration of oral SCC cells on TN-C, was found to enhance their migration on FN and invasion of a reconstituted basement membrane. Addition of antibodies to FN to the PTF-CM inhibited SCC-cell migration on TN-C, and depletion of FN from the PTF-CM abolished its ability to induce migration or invasion by oral SCC cells, suggesting that FN promotes the migration and invasion of oral SCC cells. Western blots of the PTF-CM identified FN containing the EDA but not the EDB domain. When soluble FN was added to the control medium in the lower chamber of the Transwell system, SCC-cell migration increased significantly. These results demonstrate that both the EDA and the EDB domains of FN are expressed in the extracellular matrix of oral SCC in vivo and PTF in vitro and indicate that FN is the probable chemotactic factor in the PTF-conditioned medium. Int. J. Cancer 78:261–267, 1998.© 1998 Wiley-Liss, Inc.     

Altered TGF-β signaling in a subpopulation of human stromal cells promotes prostatic carcinogenesis

Carcinoma-associated fibroblasts (CAF) play a critical role in malignant progression. Loss of TGF-β receptor II (TGFβR2) in the prostate stroma is correlated with prostatic tumorigenesis. To determine the mechanisms by which stromal heterogeneity because of loss of TGFβR2 might contribute to cancer progression, we attenuated transforming growth factor beta (TGF-β) signaling in a subpopulation of immortalized human prostate fibroblasts in a model of tumor progression. In a tissue recombination model, loss of TGFβR2 function in 50% of the stromal cell population resulted in malignant transformation of the nontumorigenic human prostate epithelial cell line BPH1. Mixing fibroblasts expressing the empty vector and dominant negative TGFβR2 increased the expression of markers of myofibroblast differentiation [coexpression of vimentin and alpha smooth muscle actin (αSMA)] through elevation of TGF-β1 and activation of the Akt pathway. In combination, these two populations of stromal cells recapitulated the tumor inductive activity of CAFs. TGFβR2 activity in mixed stromal cell populations cultured in vitro caused secretion of factors that are known to promote tumor progression, including TGF-β1, SDF1/CXCL12, and members of the fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) families. In vivo, tissue recombination of fibroblasts overexpressing TGF-β1 and SDF1/CXCL12 not only induced transformation of BPH1 cells, but also promoted a robust growth of highly invasive cells, similar to effects produced by CAFs. While the precise nature and/or origin of the particular stromal cell populations in vivo remain unknown, these findings strongly link heterogeneity in TGF-β signaling to tumor promotion by tumor stromal cells.     

TAM通过PLGF/Flt-1和TGF-β1通路促进非小细胞肺癌生长和肿瘤血管异生的研究

目的 探讨胎盘生长因子(PLGF)介导非小细胞肺癌(NSCLC)细胞和肿瘤相关巨噬细胞(TAM)之间相互作用的具体机制。方法 采用尾静脉注射法将转染腺病毒(AAV)的NSCLC A549细胞注入10周龄的雄性NOD/SCID小鼠体内,构建小鼠肺癌动物模型。流式细胞技术检测瘤体内各种巨噬细胞(MΦ)亚型,RT-qPCR检测肿瘤细胞和TAM中PLGF、血管内皮生长因子受体(Flt-1)和转化生长因子β1(TGF-β1)表达水平。根据A549细胞和MΦ细胞的培养条件不同,分为单纯A549组,单纯MΦ组,A549+MΦ组,A549+MΦ+sFlt-1组(加入10 μg/L sFlt-1),PLGF+MΦ组(加入100 ng PLGF)和PLGF+MΦ+sFlt-1组(加入100 ng PLGF和10 μg/L sFlt-1)。Transwell、MTT法分别检测不同共培养条件下A549细胞的增殖和迁移能力。根据HUVEC细胞的培养条件,分为对照组、条件培养基(CM)组、CM+SB431542组、TGF-β1组和TGF-β1+SB431542组,HUVEC细胞胶原凝胶测定法检测肿瘤血管异生情况。结果 与RFP-细胞相比,PLGF主要由肿瘤细胞表达(31.72±4.69 vs. 2.31±0.06,P＜0.001),而Flt-1主要由CD163+的巨噬细胞表达(P＜0.001)。A549+MΦ组A549细胞增殖能力显著强于单纯A549组和A549+MΦ+sFlt-1组(OD值:3.62±0.23 vs. 4.53±0.34 vs. 3.71±0.37,P＜0.05)。TAM/M2巨噬细胞中TGF-β1的表达量高于M1巨噬细胞(0.99±0.23 vs. 0.07±0.02,P＜0.05)。CM组和TGF-β1组中HUVEC细胞管状结构的形成最多(P＜0.05),TGF-β1抑制剂SB431542可抑制这一现象。结论 TAM和NSCLC细胞间通过PLGF/Flt-1和TGF-β1信号通路间的交互作用,促进NSCLC的生长和血管异生。     

Enhancement of antiproliferative activity of interferons by RNA interference-mediated silencing of SOCS gene expression in tumor cells

The suppressor of cytokine signaling (SOCS) proteins, negative regulators of interferon (IFN)-induced signaling pathways, is involved in IFN resistance of tumor cells. To improve the growth inhibitory effect of IFN-β and IFN-γ on a murine melanoma cell line, B16-BL6, and a murine colon carcinoma cell line, Colon26 cells, SOCS-1 and SOCS-3 gene expression in tumor cells was downregulated by transfection of plasmid DNA expressing short hairpin RNA targeting one of these genes (pshSOCS-1 and pshSOCS-3, respectively). Transfection of pshSOCS-1 significantly increased the antiproliferative effect of IFN-γ on B16-BL6 cells. However, any other combinations of plasmids and IFN had little effect on the growth of B16-BL6 cells. In addition, transfection of pshSOCS-1 and pshSOCS-3 produced little improvement in the effect of IFN on Colon26 cells. To understand the mechanism underlining these findings, the level of SOCS gene expression was measured by real time polymerase chain reaction. Addition of IFN-γ greatly increased the SOCS-1 mRNA expression in B16-BL6 cells. Taking into account the synergistic effect of pshSOCS-1 and IFN-γ on the growth of B16-BL6 cells, these findings suggest that IFN-γ-induced high SOCS-1 gene expression in B16-BL6 cells significantly interferes with the antiproliferative effect of IFN-γ. These results indicate that silencing SOCS gene expression can be an effective strategy to enhance the antitumor effect of IFN under conditions in which the SOCS gene expression is upregulated by IFN. ( Cancer Sci 2008; 99: 1650–1655)     

Differences in Chemotaxis to Fibronectin in Weakly and Highly Metastatic Tumor Cells

We have examined the chemotactic ability of tumor cell lines with different metastatic potential to plasma fibronectin in Transwell chamber assay. Human renal carcinoma cells with highly metastatic potential, SN12 C-2, chemotactically migrated to fibronectin (10 μg/ml) about three-fold more strongly than weakly metastatic SN12 C-4 cells. Similarly, murine melanoma B16–BL6 cells (highly metastatic) showed higher motility to soluble fibronectin in comparison with weakly metastatic B16–F1 cells. Anti-VLA-α3 and β₁, antibodies potently blocked the chemotaxis of both highly and weakly metastatic cells (SN12 C-2 and C-4) to fibronectin. This implies that the migration of both C-2 and C-4 cells to fibronectin is basically mediated by VLA-3 receptor. In contrast, the anti-VLA-as antibody and RGDS peptide significantly inhibited the chemotaxis of SN12 C-2 cells to fibronectin, but did not affect weakly metastatic SN12 C-4 cells. These results suggest that the chemotactic ability to fibronectin positively correlates with the metastatic potential in SN12 and B16 cell lines, and that VLA-5 receptor is concerned in the motility of highly metastatic SN12 C-2 cells to soluble fibronectin.     

Inhibition of tumor-induced angiogenesis by sulfated chitin derivatives.

The effect of antimetastatic sulfated chitin derivatives (SCM-chitin III) on angiogenesis induced by B16-BL6 cells was examined in syngeneic mice. SCM-chitin III caused a marked decrease of the number of vessels toward tumor mass (angiogenic response) without affecting the tumor cell growth when coinjected with tumor cells (on day 0), or injected into tumor site on day 1 or 3 after tumor inoculation. In contrast, carboxymethyl chitin as well as heparin had no effect. Invasion of endothelial cells through reconstituted basement membrane (Matrigel) toward tumor-conditioned media was significantly inhibited by SCM-chitin III in a Transwell chamber assay. SCM-chitin III also inhibited the haptotactic migration of endothelial cells to fibronectin-substrate, but did not inhibit the chemotactic activity in tumor conditioned media in vitro. SCM-chitin III did not directly affect the viability and the growth of tumor cells and endothelial cells in vitro. These results suggest that inhibition of lung tumor metastasis by SCM-chitin III may in part be due to the inhibition of tumor-associated angiogenesis.     

Therapeutic efficacy of interleukin-2 activated killer cells against adriamycin resistant mouse B16-BL6 melanoma.

Development of multidrug-resistance (MDR) remains a major cause of failure in the treatment of cancer with chemotherapeutic agents. In our efforts to explore alternative treatment regimens for multidrug-resistant tumors we have examined the sensitivity of MDR tumor cell lines to lymphokine activated killer (LAK) cells. Adriamycin (ADM) resistant B16-BL6 melanoma, L1210 and P388 leukemic cell lines were tested for sensitivity to lysis by LAK cells in vitro. While ADM-resistant B16-BL6 and L1210 sublines were found to exhibit at least 2-fold greater susceptibility to lysis by LAK cells, sensitivity of ADM-resistant P388 cell was similar to that of parental cells. Since ADM-resistant B16-BL6 cells were efficiently lysed by LAK cells in vitro, the efficacy of therapy with LAK cells against the ADM-resistant B16-BL6 subline in vivo was evaluated. Compared to mice bearing parental B16-BL6 tumor cells, the adoptive transfer of LAK cells and rIL2 significantly reduced formation of experimental metastases (P less than 0.009) and extended median survival time (P less than 0.001) of mice bearing ADM-resistant B16-BL6 tumor cells. Results suggest that immunotherapy with LAK cells and rIL2 may be a useful modality in the treatment of cancers with the MDR phenotype.     

Characterization in vitro and in vivo of progressively adriamycin-resistant B16-BL6 mouse melanoma cells

Adriamycin (ADR)-resistant sublines of B16-BL6 mouse melanoma selected by exposure to increasing concentrations of ADR were characterized in vitro for growth properties and in vivo for tumorigenicity and pulmonary metastases. The progressively resistant sublines adapted to grow in the presence of 0.025, 0.05, 0.1, and 0.25 microgram/ml ADR in monolayer culture were found to be 5-, 10-, 20-, and 40-fold ADR-resistant, respectively, compared to the parental sensitive cells, using a soft-agar colony assay and continuous ADR treatment for 7 days. The doubling time in monolayer culture of the parent sensitive and progressively ADR-resistant sublines of B16-BL6 melanoma cells was approximately 16-18 h. Although the colony-forming efficiency in soft agar of parental sensitive cells was only 0.5-4%, the 5-, 10-, 20-, and 40-fold ADR-resistant sublines had colony-forming efficiencies of 15, 20, 30, and 77%, respectively. Tumorigenicity in C57BL/6 mice of progressively ADR-resistant sublines was similar to parental sensitive cells following s.c. and i.p. implantation of 10(5)-10(6) tumor cells. Experimental pulmonary metastases were significantly lower in ADR-resistant sublines with progressive resistance. Additionally, unlike the parental sensitive and 5-fold ADR-resistant B16-BL6 cells, the 10-, 20-, and 40-fold ADR-resistant sublines were spontaneously nonmetastatic. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunochemical detection of P-glycoprotein revealed the presence of a Mr 170,000 plasma membrane glycoprotein in the 40-fold ADR-resistant subline and its counterpart maintained for 1 year in ADR-free medium. Results from this study suggest that progressively ADR-resistant B16-BL6 mouse melanoma cells selected in vitro demonstrate a marked increase in colony formation in soft agar and a decrease in the ability to produce pulmonary metastases, without alterations in tumorigenicity.     

Role of fibroblasts in HGF/SF-induced cohort migration of human colorectal carcinoma cells: fibroblasts stimulate migration associated with increased fibronectin production via upregulated TGF-beta1.

Carcinoma cells frequently invade the surrounding tissue as coherent clusters or nests of cells. We have called this type of movement "cohort migration." We have previously presented an in vitro two-dimensional cohort migration model, in which highly metastatic variant L-10 cells of human rectal adenocarcinoma cell line RCM-1 moved as coherent cell sheets when stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA) or hepatocyte growth factor/scatter factor (HGF/SF). Pericellular deposition of EDA-containing fibronectin (EDA+FN) was essential for TPA-induced cohort migration. In this study, we investigated how colon-derived fibroblasts could affect the induction of cohort migration of colorectal carcinoma cells by HGF/SF, since carcinoma cell-fibroblast interactions frequently regulate biological events during cancer cell invasion. Fibroblasts co-cultured with L-10 carcinoma cells stimulated HGF/SF-induced cohort migration of L-10 cells up to 2 to 3-fold. Conditioned medium (CM) from fibroblasts that were cultured alone was not effective but CM from fibroblasts cocultured with carcinoma cells enhanced HGF/SF-induced cohort migration, and this effect in CM was found to be mediated by TGF-beta1 upregulated in co-cultured conditions. Among the motogenic growth factors examined, only TGF-beta1 synergistically stimulated HGF/SF-induced L-10 cell cohort migration, although TGF-beta1 alone did not induce cohort migration. TGF-beta1 also exhibited synergistic effect in several other human colorectal carcinoma cell lines. The synergistic stimulation of L-10 cell cohort migration by HGF/SF and TGF-beta1 was associated with increased production of motility-enhancing EDA+FN by L-10 cells, and blocking FN with a specific antibody effectively inhibited the synergistic effect.     

Mesothelial cells induce the motility of human ovarian carcinoma cells

The dissemination of ovarian carcinoma cells within the abdominal cavity involves interaction of tumor cells with the peritoneal mesothelium. The aim of our study was to investigate whether mesothelial cells might directly affect the spreading of this tumor by inducing motility and invasiveness of human ovarian carcinoma cells. Serum‐free supernatants of cultured human mesothelial cells [conditioned medium (CM)] induced chemotaxis and invasiveness of the human ovarian carcinoma cell lines SK‐OV‐3, OVCAR‐5 and A2780 in a Boyden chamber. Checkerboard analysis indicated that the stimulated motility was prevalently directional. Most of the chemotactic activity was retained by a heparin affinity column, indicating that the motility factor(s) is a heparin‐binding protein. Using different monoclonal antibodies (MAbs) directed against chemotactic factors that are secreted by mesothelial cells, we found that chemotaxis was partially prevented (64.8% inhibition) by antibodies against fibronectin (FN). CM also induced haptotactic migration of ovarian carcinoma cells, and anti‐FN antibodies significantly inhibited haptotaxis. The presence of FN in the CM was confirmed by Western blot analysis. Our findings suggest that mesothelium plays an active role in inducing the intraperitoneal spread of ovarian carcinoma cells, and point to FN as being one of the main mediators of mesothelium‐induced ovarian carcinoma cell motility. Int. J. Cancer 80:303–307, 1999. © 1999 Wiley‐Liss, Inc.