PI3K/Akt (PKB) pathway has been shown in several cell types to be activated by ligands to cell surface integrins, leading to the metastasis of tumour cells. The signalling pathways involved in the metastatic spread of human scirrhous gastric carcinoma cells have not been defined.
The role of the PI3K/Akt pathway in an extensive peritoneal-seeding cell line, OCUM-2MD3 and a parental cell line, OCUM-2M, was investigated by assessing in vitro adhesion and spreading assay, and in vivo peritoneal metastatic model. We also examined the correlation of PI3K/Akt pathway with integrin signals by immunoprecipitations, using cells by transfection with mutant p85 (Δp85).
Adhesiveness and spreading of OCUM-2MD3 cells on collagen type IV was significantly decreased by PI3K inhibitors and expression of mutant p85, but not by inhibitors of protein kinase C (PKC) or extracellular signal-regulated kinase (ERK). Immunoprecipitation studies indicated that the PI3K/Akt pathway was associated with integrin signalling through Src and vinculin. In an in vivo experimental metastasis model, p85 inhibition reduced peritoneal metastasis of OCUM-2MD3 cells.
PI3K/Akt signalling may be required for integrin-dependent attachment and spreading of scirrhous gastric carcinoma cells, and would be translated into generating better strategies to optimise their use in cancer clinical trials.
PI3 kinase; gastric carcinoma; adhesion; spreading: metastasis; integrin signalling
The intake of dietary fatty acids is highly correlated with the risk of various cancers. Linoleic acid (LA) is the most abundant polyunsaturated fat in the western diet, but the mechanism(s) by fatty acids such as LA modulate cancer cells is unclear. In this study, we examined the role of LA in various steps in gastric cancer progression.
The difference in gene expression between LA-treated and untreated OCUM-2MD3 gastric carcinoma cells was examined by mRNA differential display. The involvement of candidate genes was examined by oligo- and plasmid-mediated RNA interference. Biological functions of several of these genes were examined using in vitro assays for invasion, angiogenesis, apoptosis, cell viability, and matrix digestion. Angiogenesis in vivo was measured by CD-31 immunohistochemistry and microvessel density scoring.
LA enhanced the plasminogen activator inhibitor 1 (PAI-1) mRNA and protein expression, which are controlled by PAI-1 mRNA-binding protein. LA-stimulated invasion depended on PAI-1. LA also enhanced angiogenesis by suppression of angiostatin, also through PAI-1. LA did not alter cell growth in culture, but increased dietary LA-enhanced tumour growth in an animal model.
Our findings suggest that dietary LA impacts multiple steps in cancer invasion and angiogenesis, and that reducing LA in the diet may help slow cancer progression.
gastric carcinoma; linoleic acid; plasminogen activator inhibitor 1; angiostatin; invasion
Acquired drug resistance to irinotecan is one of the significant obstacles in the treatment of advanced gastric cancer. This study was performed to clarify the effect of epidermal growth factor receptor (EGFR) inhibitors in combination with SN38, an active metabolite of irinotecan, on the proliferation of irinotecan-refractory gastric cancer.
Two irinotecan-resistant gastric cancer cell lines, OCUM-2M/SN38 and OCUM-8/SN38 were, respectively, established by stepwise exposure to SN38 from the parent gastric cancer cell lines OCUM-2M and OCUM-8. The combination effects of two EGFR inhibitors, gefitinib and lapatinib, with SN38 on proliferation, apoptosis, and cell cycle on gastric cancer cells were examined.
Gefitinib or lapatinib showed synergistic anti-tumour effects against OCUM-2M/SN38 and OCUM-8/SN38 cells when used in combination with SN38, but not against OCUM-2M or OCUM-8 cells. SN38 increased the expression of EGFR and HER2 in OCUM-2M/SN38 and OCUM-8/SN38 cells. The combination of an EGFR inhibitor and SN38 significantly increased the levels of apoptosis-related molecules, caspase-6, p53, and DAPK-2, and resulted in the induction of apoptosis of irinotecan-resistant cells. The EGFR inhibitors increased the S-phase and decreased the UGT1A1 and ABCG expression in irinotecan-resistant cells. The SN38 plus Lapatinib group more effectively suppressed in vivo tumour growth by OCUM-2M/SN38 cells than either alone group.
The combination treatment with an EGFR inhibitor and irinotecan might produce synergistic anti-tumour effects for irinotecan-refractory gastric cancer cells. The regulation of SN38 metabolism-related genes and cell cycle by EGFR inhibitors might be responsible for the synergism.
gastric cancer; chemoresistance; irinotecan; EGFR inhibitor; combination therapy
Myofibroblasts in the cancer microenvironment have recently been implicated in tumour growth and metastasis of gastric cancer. However, the mechanisms responsible for the regulation of myofibroblasts in cancer-associated fibroblasts (CAFs) remain unclear. This study was performed to clarify the mechanisms for regulation of myofibroblasts in gastric cancer microenvironment.
Two CAFs (CaF-29 and CaF-33) from the tumoural gastric wall and a normal fibroblast (NF-29) from the nontumoural gastric wall, 4 human gastric cancer cell lines from scirrhous gastric cancer (OCUM-2MD3 and OCUM-12), and non-scirrhous gastric cancer (MKN-45 and MKN-74) were used. Immunofluorescence microscopy by triple-immunofluorescence labelling (α-SMA, vimentin, and DAPI) was performed to determine the presence of α-SMA-positive myofibroblasts. Real-time RT–PCR was performed to examine α-SMA mRNA expression.
Immunofluorescence microscopy showed that the frequency of myofibroblasts in CaF-29 was greater than that in NF-29. The number of myofibroblasts in gastric fibroblasts gradually decreased with serial passages. Transforming growth factor-β (TGF-β) significantly increased the α-SMA expression level of CAFs. Conditioned medium from OCUM-2MD3 or OCUM-12 cells upregulated the α-SMA expression level of CAFs, but that from MKN-45 or MKN-74 cells did not. The α-SMA upregulation effect of conditioned medium from OCUM-2MD3 or OCUM-12 cells was significantly decreased by an anti-TGF-β antibody or Smad2 siRNA.
Transforming growth factor-β from scirrhous gastric carcinoma cells upregulates the number of myofibroblasts in CAFs.
myofibroblasts; cancer-associated fibroblasts; TGF-β; scirrhous gastric carcinoma; microenvironment; interaction
Dietary (n-6)-polyunsaturated fatty acids influence cancer development, but the mechanisms have not been well characterised in gastric carcinoma.
We used two in vivo models to investigate the effects of these common dietary components on tumour metastasis. In a model of experimental metastasis, immunocompromised mice were fed diets containing linoleic acid (LA) at 2% (LLA), 8% (HLA) or 12% (VHLA) by weight and inoculated intraperitoneally (i.p.) with human gastric carcinoma cells (OCUM-2MD3). To model spontaneous metastasis, OCUM-2MD3 tumours were grafted onto the stomach walls of mice fed with the different diets. In in vitro assays, we investigated invasion and ERK phosphorylation of OCUM-2MD3 cells in the presence or absence of LA. Finally, we tested whether a cyclooxygenase (COX) inhibitor, indomethacin, could block peritoneal metastasis in vivo.
Both the HLA and VHLA groups showed increased incidence of tumour nodules (LA: 53% HLA: 89% VHLA: 100% P<0.03); the VHLA group also displayed increased numbers of tumour nodules and higher total volume relative to LLA group in experimental metastasis model. Both liver invasion (78%) and metastasis to the peritoneal cavity (67%) were more frequent in VHLA group compared with the LLA group (22% and 11%, respectively; P<0.03) in spontaneous metastasis model. We also found that the invasive ability of these cells is greatly enhanced when exposed to LA in vitro. Linoleic acid also increased invasion of other scirrhous gastric carcinoma cells, OCUM-12, NUGC3 and MKN-45. Linoleic acid effect on OCUM-2MD3 cells seems to be dependent on phosphorylation of ERK. The data suggest that invasion and phosphorylation of ERK were dependent on COX. Indomethacin decreased the number of tumours and total tumour volume in both LLA and VHLA groups. Finally, COX-1, which is known to be an important enzyme in the generation of bioactive metabolites from dietary fatty acids, appears to be responsible for the increased metastatic behaviour of OCUM-2MD3 cells in the mouse model.
Dietary LA stimulates invasion and peritoneal metastasis of gastric carcinoma cells through COX-catalysed metabolism and activation of ERK, steps that compose pathway potentially amenable to therapeutic intervention.
gastric carcinoma; dietary fatty acid; cyclooxygenase; metastasis; invasion
Triple-negative breast cancer (TNBC), a subtype of breast cancer that is oestrogen receptor (ER) negative, progesterone receptor (PR) negative, and human epidermal growth factor receptor 2 (HER2) negative, has a poor prognosis. Although a correlation between E-cadherin expression level and outcome has been demonstrated among all types of breast cancer, little is known about the significance of E-cadherin expression levels in TNBC.
A total of 574 patients who had undergone a resection of a primary breast cancer except for invasive lobular carcinomas were enrolled in this study. Expressions of ER, PR, HER2, and E-cadherin were assessed by immunohistochemistry. We examined the association between TNBC and other clinicopathological variables and evaluated the significance of the E-cadherin expression.
Among the 574 breast cancer cases, 123 (21.4%) revealed a triple-negative phenotype. Patients with TNBC experienced more frequent lymph node metastasis (P=0.024) and a poorer prognosis (P<0.001) in comparison with non-TNBC patients. Triple-negative breast cancer was an independent prognostic factor. Reduced levels of E-cadherin were observed in 238 (41.5%) of the 574 breast cancer cases. E-cadherin reduction was significantly frequent in cases of TNBC (P<0.001) and lymph node metastasis (P=0.032). Furthermore, in the 123 TNBC cases, the prognosis of patients with an E-cadherin-negative expression was significantly worse than that of E-cadherin-positive patients (P=0.0265), especially for those in clinical stage II (P=0.002). A multivariate logistic regression analysis showed a reduction of the E-cadherin expression to be an independent prognostic factor (P=0.046).
E-cadherin expression may be a useful prognostic marker for classifying subgroups of TNBC.
triple-negative breast cancer; E-cadherin; prognostic marker; intrinsic subtype; breast cancer
Many kinds of solid tumour have heterogeneously a hypoxic environment. Tumour hypoxia reported to be associated with more aggressive tumour phenotypes such as high metastatic ability and resistance to various anti-cancer therapies which may lead to a poorer prognosis. However, the mechanisms by which hypoxia affects the aggressive phenotypes remain unclear.
We established a scirrhous gastric carcinoma cell line (OCUM-12) from ascites associated with scirrhous gastric carcinoma, and a hypoxia-resistant cancer cell line (OCUM-12/Hypo) was cloned from OCUM-12 cells by continuous exposure to 1% oxygen.
Histologic findings from orthotopic tumours derived from parent OCUM-12 cells and daughter OCUM-12/Hypo cells revealed poorly differentiated adenocarcinoma with extensive fibrosis that resembled human scirrhous gastric cancer. Necrotic lesions were frequently detected in the OCUM-12 tumours but were rarely found in the OCUM-12/Hypo tumours, although both types had multiple hypoxic loci. Apoptosis rate of OCUM-12 cells was increased to 24.7% at 1% O2, whereas that of OCUM-12/Hypo was 5.6%. The OCUM-12/Hypo orthotopic models developed multiple metastases to the peritoneum and lymph nodes, but the OCUM-12 models did not. OCUM-12/Hypo cells showed epithelial-to-mesenchymal transition and high migratory and invasive activities in comparison with OCUM-12 cells. The mRNA expression levels of both E-cadherin and zonula occludens ZO-1 and ZO-2 decreased in OCUM-12/Hypo cells, and that of vimentin, Snail-1, Slug/Snail-2, Twist, ZEB-1, ZEB-2, matrix metalloproteinase-1 (MMP-1), and MMP-2 were increased in OCUM-12/Hypo cells.
OCUM-12 and OCUM-12/Hypo may be useful for the elucidation of disease progression associated with scirrhous gastric cancer in the setting of chronic hypoxia.
hypoxia resistant; scirrhous gastric carcinoma; cell line; epithelial-to-mesenchymal transition
Gastric cancer cells frequently metastasise, partly because of their highly invasive nature. Transforming growth factor-β (TGF-β) receptor signalling is closely associated with the invasion of cancer cells. The aim of this study was to clarify the effect of a TGF-β receptor (TβR) phosphorylation inhibitor on the invasiveness of gastric cancer cells.
Four gastric cancer cell lines, including two scirrhous-type cell lines and two non-scirrhous-type cell lines, were used. A TβR type I (TβR-I) kinase inhibitor, Ki26894, inhibits the phosphorylation of Smad2 at an ATP-binding site of TβR-I. We investigated the expression levels of TβR and phospho-Smad2, and the effects of TGF-β in the presence or absence of Ki26894 on Smad2 phosphorylation, invasion, migration, epithelial-to-mesenchymal transition (EMT), Ras homologue gene family member A (RhoA), ZO-2, myosin, and E-cadherin expression of gastric cancer cells.
TβR-I, TβR-II, and phospho-Smad2 expressions were found in scirrhous gastric cancer cells, but not in non-scirrhous gastric cancer cells. Ki26894 decreased Smad2 phosphorylation induced by TGF-β1 in scirrhous gastric cancer cells. Transforming growth factor-β1 upregulated the invasion, migration, and EMT ability of scirrhous gastric cancer cells. Transforming growth factor-β1 significantly upregulated the activity of RhoA and myosin phosphorylation, whereas TGF-β1 decreased ZO-2 and E-cadherin expression in scirrhous gastric cancer cells. Interestingly, Ki26894 inhibited these characteristics in scirrhous gastric cancer cells. In contrast, non-scirrhous gastric cancer cells were not affected by TGF-β1 or Ki26894 treatment.
A TβR-I kinase inhibitor decreases the invasiveness and EMT of scirrhous gastric cancer cells. Ki26894 is therefore considered to be a promising therapeutic compound for the metastasis of scirrhous gastric carcinoma.
scirrhous gastric cancer; TGF-β; epithelial-to-mesenchymal transition; Smad2; phosphorylation inhibitor
Scirrhous-type gastric carcinoma (SGC) exhibits an extensive submucosal fibrosis and extremely poor patient prognosis. We investigated the importance of the cancer–stromal interaction in the histogenesis of SGC.
Gastric fibroblasts NF-25 and intestinal fibroblasts NF-j2 were co-cultured with SGC-derived (HSC-39) or non-SGC-derived (HSC-57 and HSC-64) cells. To identify genes that are up- or downregulated in NF-25, complementary DNA (cDNA) microarray analysis was performed. The antibody against vascular-cell adhesion molecule-1 (VCAM-1) was used for cell growth test and immunohistochemistry. Moreover, the impact of interaction with NF-25 fibroblasts on HSC-39 cells was investigated using western blot and reverse transcription-polymerase chain reaction.
HSC-39 cells stimulated growth of NF-25 but not NF-j2 when co-cultured. Induction of VCAM-1 in NF-25 fibroblasts was identified, which was specific when co-cultured with HSC-39 but not with non-SGC-derived HSC-57 and HSC-64 cells. Neutralising antibody to VCAM-1 suppressed NF-25 growth in dose-dependent manners. In tissue samples, positive immunoreactivity of VCAM-1 in SGC-derived fibroblasts was significantly higher than that in non-SGC-derived fibroblasts. Furthermore, interaction with NF-25 fibroblasts not only induced the epithelial–mesenchymal transition-like change, but also expressions of matrix metalloproteinase- related genes in HSC-39 cells.
Direct interaction between SGC cells and gastric fibroblasts establishes the tumour microenvironment and reinforces the aggressiveness of SGC.
scirrhous-type gastric carcinoma; gastric fibroblast; cDNA microarray; VCAM-1; integrin-α4; epithelial–mesenchymal transition; matrix metalloproteinase
Vascular endothelial growth factor receptor-3 (VEGFR-3) signalling mediates lymphangiogenesis and lymphatic invasion; however, the effect of VEGFR-3 inhibition on the lymph node (LN) metastasis remains unclear. The aim of this study is to clarify the benefit of a VEGFR-3 inhibitor Ki23057 for LN metastasis.
Ki23057 was administered orally to gastric cancer models created by orthotopic inoculation of diffuse-type gastric cancer cells, OCUM-2MLN. The effects of Ki23057 on lymphatic vessel invasion, lymphatic vessel density, and VEGFR-3 phosphorylation were examined by immunostaining or immunoblotting.
Ki23057 inhibited the autophosphorylation of VEGFR-3, with IC50 values of 4.3 nM in the cell-free kinase assay. Murine gastric cancer models created by the orthotopic inoculation of OCUM-2MLN cells showed the diffusely infiltrating growth and frequently developed LN metastasis. The oral administration of Ki23057 significantly (P<0.01) reduced the size of orthotopic tumours and the number of the metastatic LN in gastric cancer models. The degree of lymphatic invasion and lymphangiogenesis was significantly (P<0.05) lower in the gastric tumours treated by Ki23057. Ki23057 inhibited the phosphorylation of VEGFR-3 of lymphatic endothelial cells in gastric tumours.
The inhibition of lymphangiogenesis targeting VEGFR-3 phosphorylation is a therapeutic strategy for inhibiting LN metastasis of diffuse-type gastric cancer.
diffuse-type gastric carcinoma; lymph node metastasis; orthotopic gastric cancer model; phosphorylation inhibitor; vascular endothelial cell growth factor receptor-3
Identification of cancer cells in the peritoneal cavity could influence therapy and outcome of gastric carcinoma patients. The objective of this study was to evaluate the clinical impact of the real-time quantitative polymerase chain reaction-(PCR) based identification of isolated tumour cells in the peritoneal lavage fluid of gastric carcinoma. The peritoneal lavage fluid of 116 patients with gastric cancer was sampled at laparotomy. After RNA extraction and reverse transcription, real-time quantitative PCR was performed using the primers and probes for carcinoembryonic antigen (CEA) and cytokeratin-20 (CK20). When either the CEA mRNA or CK20 mRNA level of the sample was over the cutoff value, the sample was determined to be PCR-positive. Forty-six (40%) of the 116 patients were PCR-positive and 30 (65%) of the 46 PCR-positive patients died as a result of recurrent peritoneal dissemination. The prognosis of the 46 PCR-positive patients was significantly (P<0.001) worse than that of 70 PCR-negative patients. Furthermore, in 80 of the cases with a curative R0 resection, 15 of the patients with PCR-positive findings had a significantly (P<0.001) poorer prognosis than the 65 PCR-negative patients. The prognosis of the PCR-positive patients was significantly poorer than that of the PCR-negative patients in the T3 (P<0.0001) and T4 (P=0.048) subgroups. In a multivariate analysis of the 80 cases with a curative R0 resection, the real-time quantitative RT–PCR (CEA and/or CK20) levels indicated that they were independent prognostic factors. The real-time quantitative RT–PCR analysis of the CEA and/or CK20 transcripts in the peritoneal lavage fluid is useful for predicting the peritoneal recurrence in patients who are undergoing a curative resection for gastric cancer.
gastric cancer; micrometastasis; prognosis; peritoneal dissemination
TGF-βs are multifunctional polypeptides that regulate cell growth and differentiation, extracellular matrix deposition, cellular adhesion properties, angiogenesis and immune functions. In this study, we investigated the effect of TGF-β1 on liver metastasis and its mechanism by using human pancreatic cancer cell lines Panc-1, Capan-2, and SW1990. Capan-2 and SW1990 cells demonstrated enhanced liver metastatic potential by in vivo splenic injection with TGF-β1. Consequently, we examined the role of TGF-β1 on in vitro angiogenesis and received cytotoxicity by peripheral blood mononuclear leukocytes (PBMLs). While TGF-β1 slightly decreased cell proliferation, it also upregulated VEGF production in all cancer cells examined. The binding of PBMLs to cancer cells and cancer cell cytotoxicity during co-culture with PBMLs were remarkably decreased by treatment with TGF-β1. Panc-1 cells revealed no liver metastasis despite their high immunogenetic and angiogenetic abilities, which was attributed to a lack of expression of the cell surface carbohydrates that induce attachment to endothelial cells. We concluded that the presence of TGF-β1 in the microenvironment of tumour site might play an important role in enhancing liver metastasis of pancreatic cancer by modulating the capacity of angiogenesis and immunogenicity. © 2001 Cancer Research Campaign http://www.bjcancer.com
TGF-β 1; liver metastasis; pancreatic cancer; VEGF
We established a highly peritoneal-seeding cell line, OCUM-2MD3, from a poorly peritoneal-seeding cell line, OCUM-2M, of human scirrhous gastric carcinoma. The intraperitoneal inoculation of OCUM-2MD3 cells produced peritoneal dissemination in nude mice, whereas that of OCUM-2M cells did not. We then investigated the correlation between seeding potential and adhesion molecule beta 1-integrins or alpha 6 beta 4-integrin. alpha 2 beta 1- and alpha 3 beta 1-integrin expression on OCUM-2MD3 cells (91.6% and 93.6%) was increased compared with that of OCUM-2M cells (47.8% and 34.3%) by flow cytometric analysis, and the expression level of the other integrins was not different between the two cell lines. The binding ability of OCUM-2MD3 cells to matrigel, fibronectin, laminin and type I collagen was significantly increased, approximately seven times, three times, eight times, and three times greater than that of OCUM-2M cells respectively. The invasiveness of OCUM-2MD3 cells was also significantly increased 8-fold over OCUM-2M cells. The binding and invasive ability of OCUM-2MD3 cells was significantly decreased following the addition of anti-alpha 2 beta 1- and alpha 3 beta 1-integrin antibody, but not by anti-alpha 6 beta 1- and alpha 6 beta 4-integrin antibody. These results suggest that adhesiveness and invasiveness in peritoneal implantation of scirrhous gastric carcinoma might be closely associated with alpha 2 beta 1- and alpha 3 beta 1-integrin.
Scirrhous gastric cancer cells proliferate rapidly with fibrosis, when the cancer cells invade into the submucosa of the stomach. To investigate the mechanisms responsible for the rapid proliferation, the growth interaction between gastric cancer cells and fibroblasts was examined. Human gastric cancer cell lines established from scirrhous carcinoma or well-differentiated adenocarcinoma were used. Human fibroblast cell lines were obtained from various organs. The growth interaction between gastric cancer cells and fibroblasts was examined by calculating the number of cancer cells or by measuring [3H]thymidine incorporation of cancer cells. Gastric fibroblasts specifically stimulated the growth of scirrhous gastric cancer cells, but not that of well-differentiated adenocarcinoma cells. The growth factor(s) produced from gastric fibroblasts were then partially purified and characterised. The growth-promoting factor(s) had apparent molecular weights of 10000 dalton and was sensitive both to heat and proteinase treatment. No inhibition for the factor(s) was achieved with defined anti-growth factor antibodies. In this study, differential responses of scirrhous and well-differentiated gastric cancer cells to orthotopic fibroblasts were shown. Rapid proliferation of scirrhous gastric carcinoma should be partly controlled by orthotopic fibroblasts. The growth factor(s) from gastric fibroblasts, which was distinct from various defined growth factors such as epidermal growth factor (EGF), basic fibroblast growth factor (b-FGF), transforming growth factor-alpha (TGF-alpha), keratinocyte growth factor (KGF), vascular endothelial growth factor (VEGF), insulin-like growth factor I (IGF-I), hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF) and transforming growth factor beta 1 (TGF-beta 1) may play an important role in the progression of scirrhous gastric cancer cells.
Determination of the differences between cell lines which are derived from a primary tumour and a disseminated metastatic lesion from the same patient may aid in elucidating the factors associated with disseminated metastases. We report on the establishment and characterisation of two new scirrhous gastric cancer cell lines, designated OCUM-2M and OCUM-2D, derived from a 49-year-old female. OCUM-2M was derived from a primary gastric tumour, and OCUM-2D was derived from a sample of disseminated metastasis. The two cell lines were derived from the same patient. We investigated biological differences between the two cell lines to study mechanisms involved in disseminated metastasis. The growth activity of OCUM-2D cells as determined by doubling time and tumorigenicity was greater than that of OCUM-2M cells. The level of epidermal growth factor receptor (EGFR) expression in OCUM-2D cells was about twice that of OCUM-2M cells and the growth of OCUM-2D cells was stimulated more by epidermal growth factor (EGF) than that of OCUM-2M cells. The invasive activity of OCUM-2D cells was higher than that of OCUM-2M cells and was increased after addition of transforming growth factor-beta 1 (TGF-beta 1). An increase in the number of attached and spreading cells was found following the addition of 10 ng ml-1 TGF-beta 1. These findings suggest that high growth and invasive activity may play an important role in disseminated metastasis and that EGF and TGF-beta 1, which affect the growth and invasive activity of OCUM-2D cells, might be factors associated with metastasis in scirrhous gastric carcinoma. The two cell lines OCUM-2M and OCUM-2D should be beneficial for analysing mechanisms of tumour progression.