Imatinib inhibits the regrowth of human colon cancer cells after treatment with 5-FU and cooperates with vitamin D analogue PRI-2191 in the downregulation of expression of stemness-related genes in 5-FU refractory cells.

Conventional cytotoxic drugs preferentially eliminate differentiated cancer cells but spare relatively more resistant stem-like cancer cells capable to initiate recurrence. Due to cancer cell plasticity, the stem-like phenotype can be also acquired by cancer cells refractory to treatment with cytotoxic drugs. We investigated whether drugs inhibiting receptor tyrosine kinases could be used to target human colon cancer cells initiating cancer regrowth following conventional cytotoxic treatment. The moderately differentiated cell line HT-29 and poorly differentiated cell line HCT-116 were exposed to 5-fluorouracil (5-FU). Cells that resisted the exposure to 5-FU were subsequently treated with imatinib or sunitinib. Both drugs reduced clonogenicity of 5-FU-refractory cells under normoxic and hypoxic culture conditions. The expression of numerous stemness-related genes was upregulated in cancer cells following the exposure to 5-FU, and remained at a high level in 5-FU-refractory cells undergoing renewal under normoxia, but decreased spontaneously under hypoxia. Imatinib downregulated the expression of stemness-related genes in cells undergoing renewal under normoxia. A combination of imatinib with PRI-2191, an analogue of 1,25-dihydroxyvitamin D3, downregulated stemness-related genes in HCT-116/5-FU cells more efficiently than imatinib alone. A synthetic analogue of 1,25-dihydroxyvitamin D2 (PRI-1906) abolished the effect of imatinib on gene expression in HCT-116/5-FU cells undergoing renewal under normoxia. Sunitinib promoted shift of phenotype of HT-29/5-FU cells undergoing renewal toward stem-like one. It suggests that the phenotype shift toward stemness induced by sequential sunitinib treatment following 5-FU treatment could increase a risk of cancer recurrence. In contrast to sunitinib, imatinib could be used both to interfere with cancer regrowth after conventional chemotherapy and to downregulate the expression of stemness-related genes in residual colon cancer cells capable to initiate cancer recurrence. The findings suggest that imatinib could also be combined with vitamin D analogue PRI-2191 to prevent recurrence more efficiently than imatinib alone and to compensate for vitamin D deficiency resulting from imatinib treatment.

Imatinib Inhibits the Renewal and Tumorigenicity of CT-26 Colon Cancer Cells after Cytoreductive Treatment with Doxorubicin.

Conventional anti-cancer drugs preferentially eliminate differentiated cancer cells but those cells that are spared (i.e. cancer stem cells: CSC), initiate recurrence. We tested whether drugs that target receptor tyrosine kinases (RTKs) involved in developmental signaling cascades and activated in CSC, could be used to silence and/or to eliminate colorectal cancer cells refractory to conventional treatment with cytoreductive drugs. A sequential treatment model was thereby developed with doxorubicin (DOX) and imatinib. CT-26 mouse colon carcinoma cells were pre-treated with DOX to select DOX-refractory cells with CSC properties, which were then subsequently treated with RTK inhibitor imatinib, where their regrowth was found to be inhibited. Under both normoxic and hypoxic conditions, imatinib potently inhibited clonogenicity of DOX-refractory CT-26 cells. Treatment with DOX did not eliminate tumorigenic CT-26 cells, since CT-26 cells pre-exposed to DOX in vitro, when inoculated subcutaneously, induced tumors in 90 % of mice, as opposed to a 100 % rate in the case of chemonaive CT-26 cells. In mice inoculated with chemonaive CT-26 cells, tumor formation was not prevented by imatinib. However, imatinib prevented tumor formation in 50 % of mice inoculated with CT-26 cells pre-exposed to DOX in vitro, with the remaining 50 % mice showing delayed tumor formation. These results suggest that the sequential use of the drug imatinib, as a drug targeting cancer cells expressing stem cell features after conventional cytoreductive treatment, is a promising future strategy for preventing tumor recurrence.

The Effect of Analogues of 1α,25-Dihydroxyvitamin D2 on the Regrowth and Gene Expression of Human Colon Cancer Cells Refractory to 5-Fluorouracil.

This study aimed to evaluate the capacity of hypocalcemic analogues of 1α,25-dihydroxyvitamin D2 (1,25D2) and 1α,25-dihydroxyvitamin D3 (1,25D3) to inhibit regrowth and regulate the stemness-related gene expression in colon cancer cells undergoing renewal after exposure to 5-fluorouracil (5-FU). All of the tested analogues of 1,25D2 equally potently decreased the clonogenicity and the proliferative activity of HT-29 cells which survived the exposure to 5-FU, but differently regulated gene expression of these cells during their renewal. 1,25D2 and analogues (PRI-1907 and PRI-1917), as well as 1,25D3 and analogue PRI-2191, decreased the relative expression level of several stemness-related genes, such as NANOG, OCT3/4, PROM1, SOX2, ALDHA1, CXCR4, in HT-29/5-FU cells during their renewal, in comparison to untreated HT-29/5-FU cells. The other 1,25D2 analogues (PRI-1906 and PRI-1916) were not capable of downregulating the expression of these stemness-related genes as the analogues PRI-1907 and PRI-1917 did. All of the tested vitamin D analogues upregulated CDH1, the gene encoding E-cadherin associated with epithelial phenotype. Out of the series of analogues studied, side-chain branched analogues of 1,25D2 (PRI-1907, PRI-1917) and the analogue of 1,25D3 (PRI-2191) might be used to target cancer cells with stem-like phenotypes that survive conventional chemotherapy.

Differential interference of vitamin D analogs PRI-1906, PRI-2191, and PRI-2205 with the renewal of human colon cancer cells refractory to treatment with 5-fluorouracil.

This study was aimed to determine whether hypocalcemic analogs of active forms of vitamins D modulate expression of genes related to stem-like phenotype in colon cancer cell lines HT-29 and HCT-116 undergoing renewal after the treatment with 5-fluorouracil (5-FU). Both lines express vitamin D receptor, but differ in differentiation stage and vitamin D sensitivity. Cells that resisted the 5-FU exposure were treated with synthetic analog of 1,25-dihydroxyvitamin D2 (PRI-1906) and analogs of 1,25-dihydroxyvitamin D3 (PRI-2191 and PRI-2205). Proliferative activity was more profoundly affected by vitamin D analogs in HT-29/5-FU than in HCT-116/5-FU cells. In HT-29/5-FU cells, analogs PRI-1906 and PRI-2191 downregulated the expression of genes related to survival, re-growth, and invasiveness during renewal, while PRI-2205 increased expression of genes related to differentiation only. In HCT-116/5-FU cells, PRI-2191 decreased the expression of stemness- and angiogenesis-related genes, whereas PRI-1906 augmented their expression. The effects in HCT-116/5-FU cells were observed at higher concentrations of the analogs than those used for HT-29/5-FU cells. Out of the series of analogs studied, PRI-2191 might be used to counteract the renewal of both moderately and poorly differentiated cancer cells following conventional treatment.

Soluble TNF-α receptor I encoded on plasmid vector and its application in experimental gene therapy of radiation-induced lung fibrosis.

Post-radiation inflammatory reaction leads to an irreversible pulmonary fibrosis which may cause lethal respiratory insufficiency. Pathological inflammatory and fibrotic changes might be attenuated by inhibiting tumour necrosis factor (TNF)-α activity using TNF-α soluble receptors. Thus, an experimental antifibrotic gene therapy with the plasmid vector encoding a mouse soluble receptor I for TNF-α (psTNFR-I) was assessed. Soluble TNFR-I encoding gene was cloned into pcDNA3.1 plasmid. The ability of psTNFR-I expressing vector to transfect cells, and its biological activity in vitro and in vivo were examined by PCR, RT-PCR, MTT assay and ELISA. The C57Bl/6J mice received single intramuscular injection of psTNFR-I, conjugated with polyetylenimine (PEI) 25 kDa, equally divided to both hind legs, 3 days before irradiation (20 Gy, Co60), and either a single injection or ten injections once a week after irradiation. The data proved the effectiveness of psTNFR-I product to neutralise TNF-α activity in vitro. The in vivo plasmid incorporation and maintenance was confirmed. Measurements of plasma soluble TNFR-I levels showed that the in vivo gene transfer was effective. PEI was found to enhance transfection efficiency in vivo. The psTNFR-I/PEI complexes caused no toxicity in the transfected mice. C57Bl/6J mice that received prolonged psTNFR-I/PEI injections developed lethal fibrotic syndrome and died 8 weeks later than the mice treated with a double plasmid injection and the control mice treated with a control plasmid. Sequential administration of soluble TNFR-I by a nonviral, intramuscular gene transduction in the early and late post-radiation inflammatory phase prolonged survival of irradiated mice and attenuated the symptoms of lung fibrosis. The psTNFR-I gene transduction may provide a safe and simple method to partially neutralise TNF-α activity and prevent radiation-induced lung injury.

[Epithelial-mesenchymal transition in cancer progression]. / Rola przejscia epitelialno-mezenchymalnego w progresji nowotworu.

According to recently published data, the epithelial-mesenchymal transition--a process important for embryonic development, may be involved in many pathological processes such as wound healing, tissue fibrosis or cancer progression. The EMT process in cell is driven by growth factors (EGF, PDGF, HGF) or other signaling proteins such as TGF-beta, sonic hedgehog (Shh), Wnt/beta-catenin and extracellular matrix (ECM) components that may stimulate cellular growth and migration. During cancer progression, the EMT process is necessary to the conversion of benign tumor to aggressive and highly invasive cancer. This is due to complex changes in cancer cells and their microenvironment that lead to dissolution of intracellular junctions and their detachment from basolateral membrane, and changes in the interactions between cancer cells and ECM. The loss of adhesion is accompanied by molecular and morphologic changes in cancer cells that are essential for the phenotypic change from epithelial to mesenchymal one, and the acquirement of higher migration and invasion potential. During the colonization of distant sites, a reverse process mesenchymal-epithelial transition (MET) takes place and metastatic cancer cells again acquire the epithelial phenotype. The EMT in cancer progression is not only specific for cancer cells. It has been suggested that also cells within tumor microenvironment e.g. cancer associated fibroblasts (CAF) are generated in part from normal epithelial cells in EMT process. The understanding of the role of EMT and MET processes in cancer progression and their relationship with cancer stem cells, cancer associated fibroblasts and other stroma cells might lead to the discovery of new, targeted cancer therapies.

Vascular endothelial growth factor and soluble FLT-1 receptor interactions and biological implications.

Vascular endothelial growth factor (VEGF), binding to an appropriate receptor like FLT, is the main mitogen for endothelial cells and a strong inducer of angiogenesis. A soluble form of VEGF receptor, sFLT-1, specifically binds VEGF and inhibits its activity. The following expression plasmids were used in the experiments: pVEGF plasmid encoding VEGF165, pFGF-2 encoding FGF-2 and psFLT-1 plasmid encoding the soluble form of VEGF receptor, sFLT-1. The interaction between VEGF and sFLT-1 was evaluated using a migration test and ERK1/2 activity utilizing mouse sarcoma cells (L-1). Implication of the VEGF/sFLT-1 action was also visualized using in vivo angiogenesis assay. The conditioned medium (CM) from L-1 phVEGF-165 transfectants stimulated L-1 cell migration more than medium from non-transfected L-1 cells. Media collected from phVEGF-165 transfectants or original L-1 cells only slightly stimulated the migration of cells transfected with psFLT-1. The L-1 cells also showed intensive phospho-ERK1/2 activity when treated with the CM from VEGF transfectants. In vivo tests showed that sFLT-1 effectively suppressed VEGF-mediated angiogenesis without affecting FGF-2-driven angiogenesis. To summarize, this study documented that sFLT-1 released from transfected cells might inhibit cell functions induced by VEGF, but not by FGF. The results obtained from in vivo angiogenesis tests also confirm the antiangiogenic potency of cloned sFLT-1, which can be useful for planning cancer experimental therapy studies.

Role of v-Raf and truncated form RAF1 in the induction of vascular endothelial growth factor and vascularization.

In this work we studied the effect of v-raf and different form RAF on up regulation of VEGF gene expression and angiogenesis. In the experiments the truncated forms of RAF1 gene were transfected into the cells of the established human urothelial line HCV-29, otherwise non-angiogenic. The plasmids coding for mitochondrial targeted dominant active or dominant negative RAF1 (DAM, DNM respectively) were deleted with RAS binding domain. DAM has the ability to phosphorylate BAD whereas DNM cannot phosphorylate BAD. DAM RAF1, similarly to v-raf transfected cells, induced up-regulation of VEGF and caused angiogenic phenotype as studied in vivo. DNM RAF1 transfectants induced VEGF independent angiogenesis.

Cytostatic and cytotoxic effects of alkylglycerols (Ecomer).

BACKGROUND: Shark liver oil, with a standardized concentration of alkylglycerols and their methoxyderivates, has been widely used in Scandinavian countries as complementary medicine in the treatment of different forms of cancer. The aim of our study was to verify the hypothesized antiproliferative effect of alkylglycerols in different human cancer cell lines. MATERIAL/METHODS: The plating efficiency method was used to assay the effect of alkylglycerols on the plating efficiency of human ovarian carcinoma (OVP-10), mammary carcinoma (MCF-7), and prostate cancer (DU-145, PC-3 and PCa-2b) cell lines. Tumor colonies containing more than 20 cells were scored as positive. Flow cytometry was applied to identify necrotic vs. apoptotic mode of cell death. The cells were exposed to Ecomer shark liver oil containing 20% alkylglycerols and 3% methoxyderivates in a dose of 0.1 mg/ml, up to a concentration corresponding to LD-50. Apoptotic and necrotic cells were stained with Anexin V and propidium iodine respectively. RESULTS: The prostate cells from DU-145, PC-3 and PCa-2B showed a dramatic reduction in the colony number even after relatively small doses of 0.5 and 0.1 mg/ml medium. Flow cytomery showed an increased percentage of apoptotic cells of ovarian and prostate carcinoma, while mammary carcinoma cells showed predominantly necrotic cells after exposure to Ecomer. CONCLUSIONS: The alkylglycerols and their methoxyderivates present in Ecomer shark liver oil showed a clear apoptotic/necrotic effect on human prostate and mammary carcinoma cell lines.

Construction of a bicistronic proangiogenic expression vector and its application in experimental angiogenesis in vivo.

Manipulation of angiogenesis in vivo is an example of successful gene therapy strategies. Overexpression of angiogenic genes like VEGF, FGF or PDGF causes new vessel formation and improves the clinical state of patients. Gene therapy is a very promising procedure but requires large amounts of pharmaceutical-grade plasmid DNA. In this regard we have constructed a bicistronic plasmid DNA vector encoding two proangiogenic factors, VEGF165 and FGF-2. The construct (pVIF) contains the internal ribosome entry site (IRES) of the encephalomyocarditis virus (ECMV) which permits both genes to be translated from a single bicistronic mRNA. The IRES sequence allows for a high efficiency of gene expression in vivo. The pVIF vector was characterized in vitro and in vivo. In vivo angiogenesis studies showed that the bicistronic vector encoding two proangiogenic factors induces the formation of new vessels significantly more than pVEGF165 or pFGF-2 alone. In our opinion the combined proangiogenic approach with VEGF165 and FGF-2 is more powerful and efficient than single gene therapy. We also postulate that IRES sequence can serve as a useful device improving efficiency of gene therapy.

The role of focal adhesion kinase in the emigration of cells from confluent cultures.

We studied the effect of the modification of focal adhesion kinase (FAK) on the growth, migration and adhesion of C3H 10T1/2 cells. Cells transfected with plasmid coding for antisense FAK displayed a low level of FAK protein. Interestingly, the transfected cells achieved a higher saturation density at confluence, and displayed reduced adhesion and enhanced emigration from a confluent layer of cells when stimulated with fibronectin. In conclusion, it can be postulated that FAK plays an important role in the mechanism of contact inhibition.