Metastatic Colorectal Carcinoma Cells Research Articles

Transient receptor potential ankyrin 1 (TRPA1) mediates reactive oxygen species-induced Ca2+ entry, mitochondrial dysfunction, and caspase-3/7 activation in primary cultures of metastatic colorectal carcinoma cells

Colorectal carcinoma (CRC) represents the fourth most common cancer worldwide and is the third most common cause of malignancy-associated mortality. Distant metastases to the liver and lungs are the main drivers of CRC-dependent death. Pro-oxidant therapies, which halt disease progression by exacerbating oxidative stress, represent an antitumour strategy that is currently exploited by chemotherapy and ionizing radiation. A more selective strategy to therapeutically exploit reactive oxygen species (ROS) signaling would consist in targeting a redox sensor that is up-regulated in metastatic cells and is tightly coupled to the stimulation of cancer cell death programs. The non-selective cation channel, Transient Receptor Potential Ankyrin 1 (TRPA1), serves as a sensor of the cellular redox state, being activated to promote extracellular Ca2+ entry by an increase in oxidative stress. Recent work demonstrated that TRPA1 channel protein is up-regulated in several cancer types and that TRPA1-mediated Ca2+ signals can either engage an antiapoptotic pro-survival signaling pathway or to promote mitochondrial Ca2+ dysfunction and apoptosis. Herein, we sought to assess for the first time the outcome of TRPA1 activation by ROS on primary cultures of metastatic colorectal carcinoma (mCRC cells). We found that TRPA1 channel protein is up-regulated and mediates enhanced hydrogen peroxide (H2O2)-induced Ca2+ entry in mCRC cells as compared to non-neoplastic control cells. The lipid peroxidation product 4-hydroxynonenal (4-HNE) is the main ROS responsible for TRPA1 activation upon mCRC cell exposure to oxidative stress. TRPA1-mediated Ca2+ entry in response to H2O2 and 4-HNE results in mitochondrial Ca2+ overload, followed by mitochondrial depolarization and caspase-3/7 activation. Therefore, targeting TRPA1 could represent an alternative strategy to eradicate metastatic CRC by enhancing its sensitivity to oxidative stress.

Organ-specific cholesterol metabolic aberration fuels liver metastasis of colorectal cancer.

Rationale: Metastasis, the development of secondary malignant growth at a distance from a primary tumor, is the main cause of cancer-associated death. However, little is known about how metastatic cancer cells adapt to and colonize in the new organ environment. Here we sought to investigate the functional mechanism of cholesterol metabolic aberration in colorectal carcinoma (CRC) liver metastasis.Methods: The expression of cholesterol metabolism-related genes in primary colorectal tumors (PT) and paired liver metastases (LM) were examined by RT-PCR. The role of SREBP2-dependent cholesterol biosynthesis pathway in cell growth and CRC liver metastasis were determined by SREBP2 silencing in CRC cell lines and experimental metastasis models including, intra-splenic injection models and liver orthotropic injection model. Growth factors treatment and co-culture experiment were performed to reveal the mechanism underlying the up-regulation of SREBP2 in CRC liver metastases. The in vivo efficacy of inhibition of cholesterol biosynthesis pathway by betulin or simvastatin were evaluated in experimental metastasis models.Results: In the present study, we identify a colorectal cancer (CRC) liver metastasis-specific cholesterol metabolic pathway involving the activation of SREBP2-dependent cholesterol biosynthesis, which is required for the colonization and growth of metastatic CRC cells in the liver. Inhibiting this cholesterol biosynthesis pathway suppresses CRC liver metastasis. Mechanically, hepatocyte growth factor (HGF) from liver environment activates SREBP2-dependent cholesterol biosynthesis pathway by activating c-Met/PI3K/AKT/mTOR axis in CRC cells.Conclusion: Our findings support the notion that CRC liver metastases show a specific cholesterol metabolic aberration. Targeting this cholesterol biosynthesis pathway could be a promising treatment for CRC liver metastasis.

Parthenolide Induces Oxidative Stress and Impedes Cell Migration by Suppressing Wnt Pathway and Epithelial-Mesenchymal-Transition (EMT) in HCT-116 Metastatic Colorectal Cancer Cells

Colorectal cancer (CRC) is a vital cause of cancer morbidity and mortality. 50% of CRC patients suffer from an aggressive metastatic disease which ultimately fallout in death. In metastatic cancer, tumour cells migrate, invade, and finally colonise to the distant organ by degrading their attachments with the extracellular matrix. Parthenolide (PTL) is a secondary metabolite of feverfew (Tanacetum parthenium) plant. It shows its cytotoxic effect towards cancer cells via different cellular signalling pathways like inhibition of NF-κB, STAT3, MAPK, JNK pathways, activation of p53 etc. In the present study, we have assessed anti-cancer and anti-metastatic potential of PTL against human HCT-116 metastatic colorectal cancer cells. Analysis of cellular oxidative status (GSH/GSSG) of PTL treated HCT-116 cells showed a significant decrease (p<0.05) in GSH level while GSSG level was increased significantly (p<0.05) on PTL treatment. PTL also increased the amount of intracellular reactive oxygen species. The qRT-PCR analysis revealed that PTL down-regulates c-fos, c-jun and N-cadherin expression and up-regulates E-cadherin expression indicating inhibition of cell migration and metastasis by EMT pathway. PTL inhibited the MMP-9 expression in a dose-dependent fashion and inhibited cancer cell migration by regulating Wnt/β-catenin signalling through the up-regulation of DKK-1 protein expression indicating PTL has a promising anti-cancer potential against HCT-116 metastatic colorectal carcinoma cells.

Hydrogen Sulfide-Evoked Intracellular Ca2+ Signals in Primary Cultures of Metastatic Colorectal Cancer Cells.

Simple SummaryColorectal cancer (CRC) is the most common type of gastrointestinal cancer and the third most predominant cancer in the world. CRC is potentially curable with surgical resection of the primary tumor. The clinical problem of colorectal cancer, however, is the spread and outgrowth of metastases, which are difficult to eradicate and lead to a patient’s death. The failure of conventional treatment to significantly improved outcomes in mCRC has prompted the search for alternative molecular targets with the goal of ameliorating the prognosis of these patients. The present investigation revealed that exogenous delivery of hydrogen sulfide (H2S) suppresses proliferation in metastatic colorectal cancer cells by inducing an increase in intracellular Ca2+ concentration. H2S was effective on metastatic, but not normal, cells. Therefore, we propose that exogenous administration of H2S to patients affected by metastatic colorectal carcinoma could represent a promising therapeutic alternative.Exogenous administration of hydrogen sulfide (H2S) is emerging as an alternative anticancer treatment. H2S-releasing compounds have been shown to exert a strong anticancer effect by suppressing proliferation and/or inducing apoptosis in several cancer cell types, including colorectal carcinoma (CRC). The mechanism whereby exogenous H2S affects CRC cell proliferation is yet to be clearly elucidated, but it could involve an increase in intracellular Ca2+ concentration ([Ca2+]i). Herein, we sought to assess for the first time whether (and how) sodium hydrosulfide (NaHS), one of the most widely employed H2S donors, induced intracellular Ca2+ signals in primary cultures of human metastatic CRC (mCRC) cells. We provided the evidence that NaHS induced extracellular Ca2+ entry in mCRC cells by activating the Ca2+-permeable channel Transient Receptor Potential Vanilloid 1 (TRPV1) followed by the Na+-dependent recruitment of the reverse-mode of the Na+/Ca2+ (NCX) exchanger. In agreement with these observations, TRPV1 protein was expressed and capsaicin, a selective TRPV1 agonist, induced Ca2+ influx by engaging both TRPV1 and NCX in mCRC cells. Finally, NaHS reduced mCRC cell proliferation, but did not promote apoptosis or aberrant mitochondrial depolarization. These data support the notion that exogenous administration of H2S may prevent mCRC cell proliferation through an increase in [Ca2+]i, which is triggered by TRPV1.

Short-term 3D culture systems of various complexity for treatment optimization of colorectal carcinoma

Three-dimensional (3D) cultures have the potential to increase the predictive value of pre-clinical drug research and bridge the gap towards anticipating clinical outcome of proposed treatments. However, their implementation in more advanced drug-discovery programs is still in its infancy due to the lack of reproducibility and low time- and cost effectiveness. HCT116, SW620 and DLD1 cells, cell lines with distinct mutations, grade and origin, were co-cultured with fibroblasts and endothelial cells (EC) in 3D spheroids. Clinically relevant drugs, i.e. 5-fluorouracil (5−FU), regorafenib and erlotinib, were administered individually to in CRC cell cultures. In this study, we established a robust, low-cost and reproducible short-term 3D culture system addressing the various complexities of the colorectal carcinoma (CRC) microenvironment. We observed a dose-dependent increase of erlotinib sensitivity in 3D (co-)cultures compared to 2D cultures. Furthermore, we compared the drug combination efficacy and drug-drug interactions administered in 2D, 3D and 3D co-cultures. We observed that synergistic/additive drug-drug interactions for drug combinations administered at low doses shifted towards additive and antagonistic when applied at higher doses in metastatic CRC cells. The addition of fibroblasts at various ratios and EC increased the resistance to some drug combinations in SW620 and DLD1 cells, but not in HCT116. Retreatment of SW620 3D co-cultures with a low-dose 3-drug combination was as active (88% inhibition, relative to control) as 5-FU treatment at high dose (100 μM). Moreover, 3D and 3D co-cultures responded variably to the drug combination treatments, and also signalling pathways were differently regulated, probably due to the influence of fibroblasts and ECs on cancer cells. The short-term 3D co-culture system developed here is a powerful platform for screening (combination) therapies. Understanding of signalling in 3D co-cultures versus 3D cultures and the responses in the 3D models upon drug treatment might be beneficial for designing anti-cancer therapies.

H3K9 trimethylation silences Fas expression to confer colon carcinoma immune escape and chemoresistance (IRM6P.654)

Abstract The Fas-FasL effector mechanism plays a key role in cancer immune surveillance by host T cells, but metastatic human colorectal carcinoma (CRC) often uses silencing of Fas expression as a mechanism of immune evasion. The molecular mechanism of FAS transcriptional silencing in human CRC is unknown. We performed genome-wide ChIP-Sequencing analysis and determined that the level of H3K9me3 in the FAS promoter region is significantly higher in metastatic than in primary human CRC cells, and is inversely correlated with the level of Fas expression. We discovered that verticillin A is a selective inhibitor of histone methyltransferases and inhibits H3K9 trimethylation in human CRC cells. Fas expression is abolished in metastatic human CRC cells and verticillin A treatment effectively restored Fas expression in these metastatic CRC cells. Furthermore, verticillin A exhibited greater efficacy than Decitabine and Vorinostat in overcoming metastatic human CRC resistance to FasL-induced apoptosis. Interestingly, verticillin A also effectively overcomes metastatic human CRC resistance to 5-Fluorouracil in vitro and in vivo. Using an orthotopic CRC mouse model, we demonstrated that tumor-infiltrating cytotoxic T lymphocytes are FasL+ and FasL-mediated cancer immune surveillance is essential for CRC inhibition in vivo. Our findings determine that H3K9 trimethylation of the FAS promoter is a dominant mechanism underlying FAS silencing and resultant CRC immune evasion and metastasis.

Regulation of Colorectal Carcinoma Stemness, Growth, and Metastasis by an miR-200c-Sox2–Negative Feedback Loop Mechanism

To elucidate a novel mechanism of miR-200c in the regulation of stemness, growth, and metastasis in colorectal carcinoma (CRC). Quantitative reverse transcription PCR was used to quantify miR-200c expression in CRC cell lines and tissues. A luciferase assay was adopted for the target evaluation. The functional effects of miR-200c in CRC cells were assessed by its forced or inhibited expression using lentiviruses. MiR-200c was statistically lower in CRC clinical specimens and highly metastatic CRC cell lines compared with their counterparts. Sox2 was validated as a target for miR-200c. The knockdown of miR-200c significantly enhanced proliferation, migration, and invasion in CRC cell lines, whereas the upregulation of miR-200c exhibited an inverse effect. Moreover, rescue of Sox2 expression could abolish the effect of the upregulation of miR-200c. In addition, the reduction of miR-200c increased the expression of CRC stem cell markers and the sphere-forming capacity of CRC cell lines. Further study has shown that miR-200c and Sox2 reciprocally control their expression through a feedback loop. MiR-200c suppresses the expression of Sox2 to block the activity of the phosphoinositide 3-kinase (PI3K)-AKT pathway. Our findings indicate that miR-200c regulates Sox2 expression through a feedback loop and is associated with CRC stemness, growth, and metastasis.

MiR-30a Suppresses Cell Migration and Invasion Through Downregulation of PIK3CD in Colorectal Carcinoma

Background/Aims: MicroRNAs (miRNAs) play key roles in tumor metastasis. The aim of this study was to determine the regulation and function of miR-30a in colorectal carcinoma (CRC) metastasis. Methods: The expression of miR-30a was detected in CRC cell lines and samples by qRT-PCR. The anti-metastatic effect of miR-30a was determined by both in vitro and in vivo assays. A luciferase reporter assay was performed to determine target association between miR-30a and phosphoinositide 3-kinase catalytic subunit delta (PIK3CD). Results: miR-30a was significantly downregulated in highly metastatic CRC cell lines and metastatic tissues. Overexpression of miR-30a suppressed CRC cell migration and invasion in vitro and liver metastasis in vivo, whereas miR-30a deletion dramatically promoted cell migration and invasion. Further studies revealed that PIK3CD is a direct target of miR-30a as miR-30a bounds directly to the 3'-UTR of PIK3CD, subsequently reducing its expression. Similar to the restoring miR-30a expression, PIK3CD downregulation inhibited cell migration and invasion, whereas PIK3CD overexpression rescued the suppressive effect of miR-30a. Moreover, significant downregulation of miR-30a in metastatic CRC tissues was found to be inversely correlated with PIK3CD expression. Mechanistic studies revealed that miR-30a down-regulated the expression of key components of the Akt/mTOR pathway, whereas PIK3CD overexpression reversed this negative effect. Conclusion: Our findings indicate that miR-30a might function as a metastasis suppressor in CRC. miR-30a may be a potential therapeutic target to block CRC metastasis.

Expression of LOX is upregulated under hypoxia in metastatic colorectal carcinoma cells

Lysyl oxidase (LOX) is an extracellular amine oxidase catalyzing the formation of lysine-derived cross-linkages in collagen and elastin in the extracellular matrices. Four human paralogs of LOX (LOXL1, LOXL2, LOXL3, and LOXL4) have been identified, each encoding the functional domains required for the amine oxidase activity of LOX. Recently, upregulation of the LOX and LOXL2 expression was reported to be significantly correlated with absence of lymphovascular invasion in tumor tissues from colorectal adenocarcinoma patients, suggesting that the oxygen tension around the tumors may be an important factor for expressional regulation of these genes in colorectal carcinomas. To evaluate the effects of hypoxia on expression of LOX and LOXL2 in colorectal carcinomas, we performed promoter assays and RT-PCR analysis under hypoxia in colorectal carcinoma cell lines, HT-29 and HCT-116. LOX expression was upregulated under hypoxia in both HT-29 and HCT-116 cells, whereas LOXL2 expression was not affected by hypoxia in those cells. In the highly metastatic HCT-116 cells, LOX showed a higher level of upregulation than in HT-29 cells, suggesting that LOX upregulation may be associated with increased invasiveness and metastatic potential in colorectal carcinomas.

Overexpression of RhoGDI2 Correlates with Tumor Progression and Poor Prognosis in Colorectal Carcinoma

RhoGDI2 has been identified as a regulator of tumor metastasis but its role in cancer remains controversial. The aims of this study were to analyze the function of RhoGDI2 in colorectal carcinoma (CRC), and to determine its possible signaling pathway in CRC. The expression of RhoGDI2 was detected in CRC cell lines, and 20 matched pairs of fresh CRC tissues, and 120 cases of clinical paraffin-embedded CRC tissues by real-time RT-PCR, Western blot, RT-PCR, or immunohistochemistry. The levels of activations of p-PI3K, p-Akt, p-MAPK, and p-MEK were then examined in RhoGDI2-overexpressing cells by Western blot. A series of assays were finally performed to evaluate the effect of RhoGDI2 on CRC cell behaviors in vitro. RhoGDI2 expression was higher in highly metastatic CRC cell lines than in lowly metastatic ones. RhoGDI2 expression was up-regulated in CRC or lymphatic metastatic tissues relative to normal mucosa (P<0.05). RhoGDI2 expression was correlated strongly with tumor size, differentiation, and Duke's stage (P<0.05). Patients with lower RhoGDI2 expression had better overall survival (P=0.012), and RhoGDI2 could predict prognosis only in patients with early-stage disease. High levels of activations of p-PI3K and p-Akt were observed in RhoGDI2-overexpressing cells. LY294002 inhibitor could abrogate the activation of PI3K/Akt pathway in those cells. Over-expression of RhoGDI2 enhanced CRC cell proliferation, motility, and invasion in vitro. Over-expression of RhoGDI2 is associated with poor overall survival in CRC patients, especially those presenting in early-stage. RhoGDI2 contributes to cell proliferation, motility, and invasion of CRC, at least in part, by activating the PI3K/Akt pathway.

Quantitative Phosphoproteomics Reveals a Cluster of Tyrosine Kinases That Mediates Src Invasive Activity in Advanced Colon Carcinoma Cells

The nonreceptor tyrosine kinase Src is frequently overexpressed and/or activated in human colorectal carcinoma (CRC), and its increased activity has been associated with a poor clinical outcome. Src has been implicated in growth and invasion of these cancer cells by still not well-known mechanisms. Here, we addressed Src oncogenic signaling using quantitative phosphoproteomics. Src overexpression increased growth and invasiveness of metastatic SW620 CRC cells. Stable isotope labeling with amino acids in cell culture in combination with liquid chromatography tandem mass spectrometry allowed the identification of 136 proteins which exhibited a significant increase in and/or association with tyrosine phosphorylation upon Src expression. These mainly include signaling, cytoskeleton, and vesicular-associated proteins. Interestingly, Src also phosphorylated a cluster of tyrosine kinases, i.e., the receptors Met and EphA2, the cytoplasmic tyrosine kinase Fak, and pseudo-tyrosine kinase SgK223, which were required for its invasive activity. Similar results were obtained with metastatic Colo205 CRC cells that exhibit high endogenous Src activity. We concluded that Src uses a tyrosine kinases network to promote its invasive activity in CRC and this implicates a reverse signaling via tyrosine kinase receptors. Targeting these tyrosine kinases may be of significant therapeutic value in this cancer.

Akt2 overexpression plays a critical role in the establishment of colorectal cancer metastasis

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. Understanding the distinct genetic and epigenetic changes contributing to the establishment and growth of metastatic lesions is crucial for the development of novel therapeutic strategies. In a search for key regulators of colorectal cancer metastasis establishment, we have found that the serine/threonine kinase Akt2, a known proto-oncogene, is highly expressed in late-stage colorectal cancer and metastatic tumors. Suppression of Akt2 expression in highly metastatic colorectal carcinoma cells inhibits their ability to metastasize in an experimental liver metastasis model. Overexpression of wild-type Akt1 did not restore metastatic potential in cells with downregulated Akt2, thus suggesting non-redundant roles for the individual Akt isoforms. In contrast, Akt2 overexpression in wild-type PTEN expressing SW480 colorectal cancer cells led to the formation of micrometastases; however, loss of PTEN is required for sustained formation of overt metastasis. Finally, we found that the consequence of PTEN loss and Akt2 overexpression function synergistically to promote metastasis. These results support a role for Akt2 overexpression in metastatic colorectal cancer and establish a mechanistic link between Akt2 overexpression and PTEN mutation in metastatic tumor establishment and growth. Taken together, these data suggest that Akt family members have distinct functional roles in tumor progression and that selective targeting of the PI3K/Akt2 pathway may provide a novel treatment strategy for colorectal cancer metastasis.

Overexpression and elevated plasma level of tumor‐associated antigen 90K/Mac‐2 binding protein in colorectal carcinoma

The cancer cell secretome may contain potentially useful biomarkers. Previously, we have analyzed the colorectal carcinoma (CRC) cell secretome. In this study, tumor-associated antigen 90K (TAA90K)/Mac-2 binding protein (Mac-2BP), one of the CRC cell secreted proteins, was chosen for evaluation as a potential CRC biomarker because its mRNA level was also found to be significantly elevated in CRC tissues and in a more metastatic CRC cell line from the analysis of two public domain array-based datasets. Immunohistochemical analysis of 241 CRC specimens showed that TAA90K/Mac-2BP was positively detected in 52.7% of the tumors, but weakly or not detected in over 95% of the adjacent nontumor epithelial cells. The plasma TAA90K/Mac-2BP levels were significantly higher in CRC patients (N = 280) versus healthy controls (N = 147) (7.77 ± 3.49 vs. 5.72 ± 2.67 μg/mL, p<0.001). Moreover, combination of TAA90K/Mac-2BP and carcinoembryonic antigen (CEA) could outperform CEA alone in discriminating CRC patients from healthy persons in this case-control study. Our results collectively indicate that analysis of cancer cell secretome is a feasible strategy for identifying cancer biomarker candidates, and the TAA90K/Mac-2BP may be a potential CRC biomarker.

E‐selectin regulates gene expression in metastatic colorectal carcinoma cells and enhances HMGB1 release

Extravasation of cancer cells is a pivotal step in the formation of hematogenous metastasis. Extravasation is initiated by the loose adhesion of cancer cells to endothelial cells via an interaction between endothelial selectins and selectin ligands expressed by the tumor cells. The present study shows that the interaction between recombinant E-selectin (rE-selectin) and colorectal cancer (CRC) cells alters the gene expression profile of the cancer cells. A DNA microarry analysis indicated that E-selectin-mediated alterations were significantly more pronounced in the metastatic CRC variants SW620 and KM12SM than in the corresponding non-metastatic local SW480 and KM12C variants. The number of genes altered by E-selectin in the metastatic variants was about 10-fold higher than the number of genes altered in the corresponding local variants. Aiming to identify genes involved in CRC metastasis, we focused, by using a DNA microarry analysis, on genes that were altered by E-selectin in a similar fashion exclusively in both metastatic variants. This analysis indicated that E-selectin down regulated (at least by 1.6-folds) the expression of 7 genes in a similar fashion, in both metastatic cells. The DNA microarry analysis was validated by real time PCR or by RT-PCR. HMGB1 was among these genes. Confocal microscopy indicated that E-selectin down regulated the cellular expression of the HMGB1 protein and enhanced the release of HMGB1 into the culture medium. The released HMGB1 in turn, activated endothelial cells to express E-selectin.

STa peptide analogs for probing guanylyl cyclase C

Guanylyl cyclase C (GC-C), universally overexpressed on primary and metastatic colorectal carcinoma cells, is activated by endogenous ligands, guanylin, and uroguanylin, and by exogenous 18-residue heat-stable enterotoxins (STa) produced by diarrheagenic bacteria. Two 12-residue STa analogs with alternate combinations of two interlocked disulfide bonds, peptides 3 and 6, were synthesized by orthogonal solid phase synthesis routes. Peptides 3 and 6 bound GC-C with a rank order potency of STa > peptide 3 > peptide 6. Peptides 3 and 6 behaved as agonists in stimulating cGMP production. The results reveal that the toxic domain of STa can be reduced to 12 amino acids.

The involvement of the sLe-a selectin ligand in the extravasation of human colorectal carcinoma cells

The extravasation of tumor cells is a pivotal stage in the formation of hematogenous metastasis. An interaction of selectins expressed on endothelial cells and selectin ligands expressed by tumor cells has been implicated to play a role in extravasation. In the present study we used a human–mouse model to prove the hypothesis that the selectin ligand sialyl Lewis-a (sLe-a) is indeed involved in the in vivo extravasation of colorectal carcinoma (CRC) cells. The results indicated that highly metastatic CRC cells expressing high levels of sLe-a extravasate more efficiently than non-metastatic CRC cells expressing low levels of sLe-a. It was also demonstrated that down regulating the expression levels of sLe-a in CRC cells by genetic manipulations, significantly reduced CRC extravasation. Non-specific effects of these manipulations were ruled out. The results of this study indicate that the arrest and adhesion of CRC cells, and possibly of other types of cancer cells as well, to endothelium depend on the expression of the selectin ligand sLe-a by the tumor cells.

MMP-9-hemopexin domain hampers adhesion and migration of colorectal cancer cells

Matrix metalloproteinases (MMPs), in particular MMP-2 and MMP-9, are involved in colon cancer progression and metastasis due to their ability to degrade extracellular matrix (ECM) components. In previous studies we described the MMP-9 hemopexin like domain (MMP-9-PEX) as an MMP-9 antagonist. In the present study it was examined whether recombinant MMP-9-PEX has an inhibitory effect on migration and adhesion of colorectal carcinoma cells. Furthermore, we searched for MMP-9 substrate binding sites within the MMP-9-PEX by surface plasmon resonance. Migration of SW620 and LS174 cells was investigated in a modified Boyden chamber assay. In the presence of 0.2 microg/ml MMP-9-PEX migration of SW620 was decreased by 34%, while addition of 0.4 microg/ml diminished migration by 56%. Migration of LS174 cells was not affected by MMP-9-PEX. Adhesion studies were performed on 96-well plates coated with gelatin, collagen type I, and laminin, respectively. In the presence of MMP-9-PEX, adhesion of SW620 cells to these coating substrates was significantly inhibited. Surface plasmon resonance studies revealed binding of collagen type I and IV, elastin, and fibrinogen to proMMP-9 as well as to MMP-9-PEX. However, equilibrium constants (Kd) indicated a higher affinity of proMMP-9 to the matrix proteins. This could indicate that there is more than one binding site for matrix components within the entire proMMP-9 molecule. Since migration and adhesion of metastatic colorectal carcinoma cells were reduced by MMP-9-PEX, this recombinant MMP-9 antagonist might be of therapeutical interest.

Tumor hepatocytes and basement membrane–Producing cells specifically express two different forms of the endostatin precursor, collagen XVIII, in human liver cancers

Endostatin is an endogenous inhibitor of angiogenesis and tumor growth in mice, which may be generated by proteolytic cleavage of collagen XVIII. In normal tissues, 2 variants of the endostatin precursor, namely the SHORT and LONG forms, regulate tissue specificity. We analyzed 53 human liver biopsies (18 hepatocellular carcinomas, 16 metastases of colorectal cancer, 3 cholangiocarcinomas, and 16 controls) by RNA dot blots, double-labeling immunohistochemistry, and in situ hybridization, using common and variant-specific probes. Tumor hepatocytes expressed the LONG form, whereas cholangiocarcinoma cells expressed the SHORT form, which was deposited in tumor basement membranes. Metastatic colorectal carcinoma cells did not express collagen XVIII. In the stromal compartment of primary and metastatic cancers, myofibroblasts and vascular endothelial cells expressed the SHORT form. Both basement membrane components, collagen IV and the SHORT collagen XVIII form, were codistributed and their mRNA levels strongly correlated (R = .75, P < .001). In addition, freshly isolated human hepatocytes expressed the LONG form and culture-activated stellate cells the SHORT form. Moreover, the full-length LONG form is a plasma protein. Thus, the LONG form is a hepatocyte-specific variant, and the SHORT form is a major component of the tumor extracellular matrix in primary and metastatic liver cancers. In the clinical context, the global expression of the endogenous endostatin precursor, collagen XVIII, in liver cancer results from the combined expression profiles of tumor cells, stromal cells, and nontumor hepatocytes at the advancing edge of the tumor, particular to each type of cancer. (HEPATOLOGY 2001;33:868-876.)

Implantation of human colorectal carcinoma cells in the liver studied by in vivo fluorescence videomicroscopy

In vivo fluorescence videomicroscopy (IVFM) was used to analyse the behavior of weakly and highly metastatic human colorectal carcinoma (CRC) cells during implantation in the liver. A highly metastatic human CRC cell line, CX-1, and a weakly metastatic line, Clone A, were double-labeled with rhodamine B isothiocyanate-dextran (Rd-Dx) to locate cells and with calcein AM to assess cell metabolic activity in an experimental metastasis model. Double-labeled CRC cells (2.0 x 10(6)) were injected into the spleens of groups of nude mice and the livers observed by IVFM over the next 72 h. CRC cells were implanted within 30 s after injection into either portal venules or the proximal third of hepatic sinusoids. Approximately 0.5% of CRC cells traversed the liver through portal-central venous shunts and implanted in the lung. The number of CX-1 cells in the liver was similar to that of Clone A cells during the first 12 h. However, more CX-1 cells than Clone A cells remained in the liver at 4 h and were in groups of 8-12 cells whereas only a few, single Clone A cells were detected in the liver at 72 h. Not all Clone A cells are committed to die within 4 h of implantation because cells harvested 4 h after hepatic implantation proliferated normally in vitro when removed from the hepatic microenvironment. Since the stress of mechanical deformation during implantation may cause differences in cell survival, CX-1 and Clone A cells were passed through filters with 8 microM pores in vitro at 10-15 cm of water pressure to recreate the trauma of hepatic implantation. Approximately 50% of both CX-1 and Clone A cells were lysed. Furthermore, both CRC lines remained metabolically active when co-cultivated with liver cells for at least 24 h in vitro. Thus, the difference in metastatic potential between the two CRC lines may reside in their response to the combination of mechanical implantation and subsequent growth in the liver parenchyma.

AN ESSENTIAL CIS-ACTING ELEMENT OF THE LCK-3' PROMOTER REGULATES THE EXPRESSION OF P56(LCK) IN METASTATIC COLORECTAL-CANCER CELLS

Detection of lck-specific transcripts has been discussed as a marker for metastasis of epithelial tumor cells. Since it is known that lck expression is regulated post-transcriptionally, it was fundamental to us to identify lck in human colorectal cancer cell lines also at the protein level. Subsequently, RT-PCR was used to confirm that lck-producing colorectal cancer cell lines contain mature transcripts initiated exclusively from the 3' promoter element. When transcriptional activity of the two different lck promoter elements was characterized in the colon cancer cell lines, we found the 3' promoter preferentially activated. Based on the results obtained from truncating this promoter element at its 5' end, we were able to define the major transcriptional activity of the downstream promoter to be regulated within a small region of only 90 bp upstream from the start site for lck type I transcripts. This finding will contribute to the identification of lymphocyte-specific transcription factors involved in the activation of the lck gene in metastatic colorectal carcinoma cells.