Differential role of Fas/Fas ligand interactions in cytolysis of primary and metastatic colon carcinoma cell lines by human antigen-specific CD8+ CTL

We have previously identified mutated ras peptides reflecting the glycine to valine substitution at position 12 as HLA-A2-restricted, CD8+ CTL neo-epitopes. CTL lines produced against these peptide epitopes lysed the HLA-A2+ Ag-bearing SW480 primary colon adenocarcinoma cell line, although IFN-gamma treatment of the targets was necessary to achieve efficient cytotoxicity. Here, we compared the lytic phenotype of the SW480 cell line to its metastatic derivative, SW620, as an in vitro paradigm to further characterize the nature of a HLA class I-restricted, Ag-specific CTL response against neoplastic cell lines of primary and metastatic origin. Although both colon carcinoma cell lines were lysed by these Ag-specific CTL following IFN-gamma pretreatment, the mechanisms of lysis were distinct, which reflected differential levels of sensitivity to the Fas pathway. Whereas IFN-gamma pretreatment rendered SW480 cells sensitive to both Fas-dependent and -independent (perforin) pathways, SW620 cells displayed lytic susceptibility to Fas-independent mechanisms only. Moreover, pretreatment of SW480 cells with the anti-colon cancer agent, 5-fluorouracil (5-FU), led to enhanced Fas and ICAM-1 expression and triggered Ag-specific CTL-mediated lysis via Fas- and perforin-based pathways. In contrast, these phenotypic and functional responses were not observed with SW620 cells. Overall, these data suggested that 1) IFN-gamma and 5-FU may enhance the lytic sensitivity of responsive colon carcinoma cells to immune effector mechanisms, including Fas-induced lysis; 2) the malignant phenotype may associate with resistance to Fas-mediated lysis in response to Ag-specific T cell attack; and 3) if Ag-specific CTL possess diverse lytic capabilities, this may overcome, to some extent, the potential "escape" of Fas-resistant carcinoma cells.     

Spectral karyotyping of the human colon cancer cell lines SW480 and SW620

The cell lines SW480 and SW620, derived from different stages of colon carcinoma in the same patient, have been used for a number of biochemical, immunological, and genetic studies on colon cancer. A comparative analysis of their karyotypes may identify chromosomal aberrations that might represent markers for metastatic spread. In the present study spectral karyotyping (SKY) was applied to these two colon cancer cell lines. Compared to previously reported G-banded karyotypes, 9 (SW480) and 7 (SW620) markers were identical, 3 (SW480) and 3 (SW620) markers could be redefined, 5 (SW480) and 8 (SW620) markers were newly identified, and 4 (SW480) and 5 (SW620) of the previous described markers could not be confirmed. The redefined aberrations include very complex rearrangements, such as a der(16) t(3;16;1;16;8;16; 1;16;10) and a der(18)t(18;15;17)(q12; p11p13;??) in SW620 and a der(19)t(19;8;19;5) in SW480, that have not been identified by conventional banding techniques. The resulting chromosome gains (5q11-->5q15, 7pter-->q22, 11, 13q14-->qter, 20pter-->p12, X) and losses (8pter-->p2, 18q12-->qter, Y) found in both SW480 and SW620 were in good agreement with those frequently described in colorectal tumors as primary changes in the stem cell. Abnormalities found exclusively in SW620 cells only (gains of 5pter-->5q11, 12q12-->q23, 15p13-->p11, and 16q21-->q24 and losses of 2pter-->2p24, 4q28-->qter, and 6q25-->qter) can be viewed as changes that occurred in a putative metastatic founder cell.     

Silibinin triggers apoptotic signaling pathways and autophagic survival response in human colon adenocarcinoma cells and their derived metastatic cells

Silibinin, a flavonolignan isolated from the milk thistle plant (Silybum marianum), possesses anti-neoplastic properties. In vitro and in vivo studies have recently shown that silibinin inhibits the growth of colorectal cancer (CRC). The present study investigates the mechanisms of silibinin-induced cell death using an in vitro model of human colon cancer progression, consisting of primary tumor cells (SW480) and their derived metastatic cells (SW620) isolated from a metastasis of the same patient. Silibinin induced apoptotic cell death evidenced by DNA fragmentation and activation of caspase-3 in both cell lines. Silibinin enhanced the expression (protein and mRNA) of TNF-related apoptosis-inducing ligand (TRAIL) death receptors (DR4/DR5) at the cell surface in SW480 cells, and induced their expression in TRAIL-resistant SW620 cells normally not expressing DR4/DR5. Caspase-8 and -10 were activated demonstrating the involvement of the extrinsic apoptotic pathway in silibinin-treated SW480 and SW620 cells. The protein Bid was cleaved in SW480 cells indicating a cross-talk between extrinsic and intrinsic apoptotic pathway. We demonstrated that silibinin activated also the intrinsic apoptotic pathway in both cell lines, including the perturbation of the mitochondrial membrane potential, the release of cytochrome c into the cytosol and the activation of caspase-9. Simultaneously to apoptosis, silibinin triggered an autophagic response. The inhibition of autophagy with a specific inhibitor enhanced cell death, suggesting a cytoprotective function for autophagy in silibinin-treated cells. Taken together, our data show that silibinin initiated in SW480 and SW620 cells an autophagic-mediated survival response overwhelmed by the activation of both the extrinsic and intrinsic apoptotic pathways.     

Metastatic SW620 colon cancer cells are primed for death when detached and can be sensitized to anoikis by the BH3-mimetic ABT-737

Anoikis, a Bax-dependent apoptosis triggered by detachment from the extracellular matrix, is often inhibited in metastatic cancer cells. Using a couple of isogenic human colon cancer cell lines derived either from the primary tumor (SW480) or from a lymph node metastasis (SW620), we found that only SW480 cells were sensitive to anoikis. Bim upregulation but not Mcl-1 degradation was determined to be a critical factor of anoikis initiation in SW480 cells. ERK-mediated phosphorylation targets Bim for ubiquitination and proteasomal degradation. A MEK inhibitor (PD0325901) was able to increase Bim expression in SW620 cells and to sensitize these cells to anoikis. Thus, in both cell lines anoikis is under the control of proteins of the Bcl-2 family. Most interestingly, the BH3-mimetic ABT-737 was found not only to increase the level of apoptosis in suspended SW480 cells but also to sensitize SW620 cells to anoikis. Accordingly, both cell lines cultured in suspension were found to be primed for death, as determined by the detection of Bcl-2:Bim and Bcl-xL:Bim complexes. In contrast, adherent SW480 and SW620 cells were resistant to ABT-737. This indicates that, whether or not they undergo anoikis, colon cancer cells that have detached from the extracellular matrix might go through a transient state, where they are sensitive to BH3 mimetics. This would confer to compounds such as Navitoclax or ABT-199 a therapeutic window where they could have anti-metastatic potential.     

Polyamine metabolism in primary human colon adenocarcinoma cells (SW480) and their lymph node metastatic derivatives (SW620)

The natural polyamines are multifunctional constituents of all eucaryotic cells. The objective of this work was to compare aspects of polyamine metabolism in two related cell lines with the idea to investigate whether metabolic differences can be attributed to functional differences of the cells. The human colon carcinoma-derived cell lines SW480 and SW620 were chosen as models. SW480 cells were isolated from the primary tumour, SW620 cells from a lymph node of the same patient. SW620 cells grow faster, and the key regulatory enzymes of polyamine biosynthesis (ODC and AdoMetDC) are more active in the metastatic cells. Moreover, their ability to accumulate polyamines from the environment is more important than of SW480 cells. Likewise polyamine concentrations were markedly higher in SW620 cells, although they are much smaller than SW480 cells, and have a particularly small cytoplasmic space. Both cell lines show a striking diminution of ODC and AdoMetDC activities and changes in the polyamine patterns at the transition from exponential to non-exponential growth--most probably as a consequence of high cell density. Depletion of putrescine and spermidine due to inactivation of ODC by DFMO causes accumulation of cells in G1, and a proportional decrease of S-phase cells in both cell lines. Based on morphologic and other criteria SW480 and SW620 cells were typified as poorly differentiated. In agreement with their low grade of differentiation they exhibit a low alkaline phosphatase activity. However, the time-dependent decrease of alkaline phosphatase is not typical of differentiation patterns of other adenocarcinoma-derived cell lines or of normal enterocytes. The high capacity of de novo polyamine biosynthesis and of polyamine uptake is presumably a prerequisite for the rapid growth and invasiveness. The fact that these properties were more accentuated in the case of SW620 cells and paralleled enhanced metastatic properties indicate relationships between basic parameters of polyamine metabolism and malignancy.     

Lactate Formation in Primary and Metastatic Colon Cancer Cells at Hypoxia and Normoxia

High glucose consumption and lactate synthesis in aerobic glycolysis are a hallmark of cancer cells. They can form lactate also in glutaminolysis, but it is not clear how oxygen availability affects this process. We studied lactate synthesis at various oxygen levels in human primary (SW480) and metastatic (SW620) colon cancer cells cultured with L‐Ser and/or L‐Asp. Glucose and lactate levels were determined colorimetrically, amino acids by HPLC, expression of AST1‐mRNA and AST2‐mRNA by RT‐PCR. In both lines glucose consumption and lactate synthesis were higher at 10% than at 1% oxygen, and lactate/glucose ratio was increased above 2.0 by L‐Asp. AST1‐mRNA expression was independent on oxygen and cell line, but AST2‐mRNA was lower at hypoxia in SW480. We conclude that, in both cell lines at 1% hypoxia, lactate is formed mainly from glucose but at 10% normoxia also from L‐Asp. At 10% normoxia, lactate synthesis is more pronounced in primary than metastatic colon cancer cells.     

Lupulone, a hop bitter acid, activates different death pathways involving apoptotic TRAIL-receptors, in human colon tumor cells and in their derived metastatic cells

Our study aimed to compare death signalling pathways triggered by lupulone in TRAIL-sensitive human colon cancer cells (SW480) and in their derived TRAIL-resistant metastatic cells (SW620). Lupulone (40 μg/ml) up-regulated expression of TRAIL DR4/DR5 death receptors at the cell surface of both cell lines, even in the absence of exogenous TRAIL ligand. Cell death induced by lupulone was inhibited in SW480 and SW620 cells exposed to blocking anti-DR4/DR5 antibodies. In SW480 cells, lupulone triggered cell death through a cross-talk between TRAIL-DR4/DR5 and the mitochondrial (intrinsic) pathways involving caspase-8 activation and Bid protein cleavage. As a consequence mitochondrial cytochrome c was released into the cytosol and activation of caspases-9 and -3 was observed. In the metastatic SW620 cells, lupulone restored the sensibility of these cells to TRAIL ligand and activated the extrinsic apoptotic pathway via DR4/DR5 death receptors and the involvement of the caspase-8/caspase-3 cascade. The demonstration that lupulone is able to activate TRAIL-death signalling pathways even in TRAIL resistant cancer cells highlights the potential of this natural compound for cancer prevention and therapy.     

Closely related colon cancer cell lines display different sensitivity to polyunsaturated fatty acids, accumulate different lipid classes and downregulate sterol regulatory element-binding protein 1

N-6 polyunsaturated fatty acids (PUFAs) may be associated with increased risk of colon cancer, whereas n-3 PUFAs may have a protective effect. We examined the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid and arachidonic acid on the colon carcinoma cell lines SW480 derived from a primary tumour, and SW620 derived from a metastasis of the same tumour. DHA had the strongest growth-inhibitory effect on both cell lines. SW620 was relatively more growth-inhibited than SW480, but SW620 also had the highest growth rate in the absence of PUFAs. Flow cytometry revealed an increase in the fraction of cells in the G2/M phase of the cell cycle, particularly for SW620 cells. Growth inhibition was apparently not caused by increased lipid peroxidation, reduced glutathione or low activity of glutathione peroxidase. Transmission electron microscopy revealed formation of cytoplasmic lipid droplets after DHA treatment. In SW620 cells an eightfold increase in total cholesteryl esters and a 190-fold increase in DHA-containing cholesteryl esters were observed after DHA treatment. In contrast, SW480 cells accumulated DHA-enriched triglycerides. Arachidonic acid accumulated in a similar manner, whereas the nontoxic oleic acid was mainly incorporated in triglycerides in both cell lines. Interestingly, nuclear sterol regulatory element-binding protein 1 (nSREBP1), recently associated with cell growth regulation, was downregulated after DHA treatment in both cell lines. Our results demonstrate cell-specific mechanisms for the processing and storage of cytotoxic PUFAs in closely related cell lines, and suggest downregulation of nSREBP1 as a possible contributor to the growth inhibitory effect of DHA.     

Proteins excreted by primary human colon carcinoma cells (SW 480) promote spreading and growth of metastatic human colon carcinoma cells (SW 620) in serum-free medium

The growth behavior of the two human colon tumor cell lines (SW 480, primary and SW 620, metastatic), originating from the same patient, was studied in six different serum-free media (SFM) [GF3, Chee's essential medium plus insulin, transferrin and selenium; GF3F, GF3 plus fetuin; GF4, GF3 plus linoleic acid-BSA; GF5, GF4 plus fetuin; GF5E, GF5 plus EGF; GF5T, GF5 plus triiodothyronine]. SW 480 grew in all of the SFM. In contrast, SW 620 grew only in four SFM. The cells did not grow in GF3 and GF4. When grown in SFM, SW 480 attached much more firmly to the dishes than SW 620 as determined by the time required to detach the cells with trypsin-EDTA (SW 480, greater than 20 min and SW 620, less than 5 min). It was speculated that SW 480 cells excrete proteins in SFM which influence attachment and growth of the cells. Growth behavior of SW 480 cells which did not grow in GF3, was studied using GF3 medium and SW 480 substratum dishes. SW 620 cells readily attached to the SW 480 substratum dishes and grew. Furthermore, when SW 620 cells were grown on substratum prepared from serum-supplemented medium incubated in the absence of cells (serum substratum), the cell growth was comparable to the cell growth on SW 480 substratum in GF3. Substratum from SW 480 cells and the serum substratum were compared for their components using SDS-PAGE system. The SW 480 substratum contains many more components than serum substratum. A protein band at 60 kD appears to be common in both SW 480 and serum substrata.     

Teriflunomide – The common drug with underestimated oxygen - Dependent anticancer potential

Leflunomide (LFN) is a well-known immunomodulatory and anti-inflammatory prodrug of teriflunomide (TFN). Due to pyrimidine synthesis inhibition TFN also exhibits potent anticancer effect. Because, there is the strict coupling between the pyrimidine synthesis and the mitochondrial respiratory chain, the oxygen level could modify the cytostatic TNF effect.The aim of the study was to evaluate the cytostatic effect of pharmacologically achievable teriflunomide (TFN) concentrations at physiological oxygen levels, i.e. 1% hypoxia and 10% tissue normoxia compared to 21%oxygen level occurred in routine cell culture environment.The TFN effect was evaluated using TB, MTT and FITC Annexin tests for human primary (SW480) and metastatic (SW620) colon cancer cell lines at various oxygen levels.We demonstrated significant differences between proliferation, survival and apoptosis at 1, 10 and 21% oxygen in primary and metastatic colon cancer cell lines (SW480, SW620) under TFN treatment. The cytostatic TFN effect was more pronounced at hypoxia compared to tissue and atmospheric normoxia in both cancer cell lines, however metastatic cells were more resistant to antiproliferative and proapoptotic TFN action. The early apoptosis was predominant in physiological oxygen tension while in atmospheric normoxia the late apoptosis was induced.Our findings showed that anticancer TFN effect is more strong in physiological oxygen compared to atmospheric normoxia. It suggests that results obtained from in vitro studies could be underestimated. Thus, it gives assumption for future comprehensive studies at real oxygen environment involving TNF use in combination with other antitumor agents affecting oxygen-dependent pyrimidine synthesis.     

Identification of Novel Biomarkers for Metastatic Colorectal Cancer Using Angiogenesis-Antibody Array and Intracellular Signaling Array

Colorectal cancer (CRC) is one of the three leading causes for cancer mortality. CRC kills over 600,000 people annually worldwide. The most common cause of death from CRC is the metastasis to distant organs. However, biomarkers for CRC metastasis remain ill-defined. We compared primary and metastatic CRC cell lines for their angiogenesis-protein profiles and intracellular signaling profiles to identify novel biomarkers for CRC metastasis. To this end, we used primary and metastatic CRC cell lines as a model system and normal human colon cell line as a control. The angiogenesis profiles two isogenic CRC cell lines, SW480 and SW620, and HT-29 and T84 revealed that VEGF was upregulated in both SW620 and T84 whereas coagulation factor III, IGFBP-3, DPP IV, PDGF AA/AB, endothelin I and CXCL16 were downregulated specifically in metastatic cell lines. Furthermore, we found that TIMP-1, amphiregulin, endostatin, angiogenin were upregulated in SW620 whereas downregulated in T84. Angiogenin was downregulated in T84 and GM-CSF was also downregulated in SW620. To induce CRC cell metastasis, we treated cells with pro-inflammatory cytokine IL-6. Upon IL-6 treatment, epithelial-mesenchymal transition was induced in CRC cells. When DLD-1 and HT-29 cells were treated with IL-6; Akt, STAT3, AMPKα and Bad phosphorylation levels were increased. Interestingly, SW620 showed the same signal activation pattern with IL-6 treatment of HT-29 and DLD-1. Our data suggest that Akt, STAT3, AMPKα and Bad activation can be biomarkers for metastatic colorectal cancer. IL-6 treatment specifically reduced phosphorylation levels of EGFR, HER2 receptor, Insulin R and IGF-1R in receptor tyrosine kinase array study with HT-29. Taken together, we have identified novel biomarkers for metastatic CRC through the angiogenesis-antibody array and intracellular signaling array studies. Present study suggests that those novel biomarkers can be used as CRC prognosis biomarkers, and as potential targets for the metastatic CRC therapy.     

Treatment of human colon carcinoma cell lines with anti-neoplastic agents enhances their lytic sensitivity to antigen-specific CD8+ cytotoxic T lymphocytes

Certain anti-neoplastic agents at subtoxic doses may exert immunomodulatory effects, which alter the expression of specific tumor cell surface molecules. We reasoned that potential increases in tumor cell surface markers, such as those important for facilitating effector-target contact, as well as triggering cell death pathways, might then improve antigen (Ag)-specific T-cell-mediated tumor cytolysis. Here, in a human colon carcinoma cell model in vitro, we examined whether the anti-neoplastic agents 5-fluorouracil (5-FU), CPT-11 or cisplatin (CDDP) could upregulate the expression of specific tumor cell surface markers, which may then enhance productive lytic interactions between CD8+ CTL and Ag-bearing tumor cells. Based on our earlier studies, IFN-gamma treatment was included as a control for sensitization to CTL-mediated lysis. Pretreatment of the SW480 primary colon carcinoma cell line with IFN-gamma, 5-FU, CPT-11 or CDDP enhanced ICAM-1 and Fas expression, resulting in Ag-specific CTL-mediated lysis involving Fas-dependent and -independent mechanisms. In contrast, pretreatment of the SW620 metastatic isolate, derived from the same patient, with IFN-gamma, CPT-11 or CDDP, but not 5-FU, enhanced ICAM-1 expression, resulting in Ag-specific CTL-mediated lysis via Fas-independent mechanisms only. Flow cytometric-based assays were then developed to measure the effects of drug treatment on caspase signaling and apoptosis incurred by tumor targets after interaction with CTL. We found that the lytic enhancement caused by drug treatment of SW480 or SW620 targets was accompanied by an increase in caspase-3-like protease activity. A peptide-based caspase inhibitor abrogated CTL-mediated apoptosis, suggesting that "chemomodulation" involved regulation of the caspase pathway. These results revealed for the first time an important role for components of the caspase pathway, such as caspase-3-like proteases, in the sensitization of human colon carcinoma cells by anti-neoplastic agents to Ag-specific CTL. Thus, certain anti-neoplastic agents may display unique immunoregulatory properties that facilitate human colon carcinoma death by engaging the lytic capacity of Ag-specific CTL, which may have implications for chemoimmunotherapy strategies.     

beta-lapachone induces cell cycle arrest and apoptosis in human colon cancer cells

BACKGROUND: Human colon cancers have a high frequency of p53 mutations, and cancer cells expressing mutant p53 tend to be resistant to current chemo- and radiation therapy. It is thus important to find therapeutic agents that can inhibit colon cancer cells with altered p53 status. beta-Lapachone, a novel topoisomerase inhibitor, has been shown to induce cell death in human promyelocytic leukemia and prostate cancer cells through a p53-independent pathway. Here we examined the effects of beta-lapachone on human colon cancer cells. MATERIALS AND METHODS: Several human colon cancer cell lines, SW480, SW620, and DLD1, with mutant or defective p53, were used. The antiproliferative effects of beta-lapachone were assessed by colony formation assays, cell cycle analysis, and apoptosis analysis, including annexin V staining and DNA laddering analysis. The effects on cell cycle and apoptosis regulatory proteins were examined by immunoblotting. RESULTS: All three cell lines, SW480, SW620, and DLD1, were sensitive to beta-lapachone, with an IC(50) of 2 to 3 microM in colony formation assays, a finding similar to that previously reported for prostate cancer cells. However, these cells were arrested in different stages of S phase. At 24 hr post-treatment, beta-lapachone induced S-, late S/G2-, and early S-phase arrest in SW480, SW620, and DLD1 cells, respectively. The cell cycle alterations induced by beta-lapachone were congruous with changes in cell cycle regulatory proteins such as cyclin A, cyclin B1, cdc2, and cyclin D1. Moreover, beta-lapachone induced apoptosis, as demonstrated by annexin V staining, flow cytometric analysis of DNA content, and DNA laddering analysis. Furthermore, down-regulation of mutant p53 and induction of p27 in SW480 cells, and induction of pro-apoptotic protein Bax in DLD1 cells may be pertinent to the anti-proliferative and apoptotic effects of beta-lapachone on these cells. CONCLUSIONS: beta-Lapachone induced cell cycle arrest and apoptosis in human colon cancer cells through a p53-independent pathway. For human colon cancers, which often contain p53 mutations, beta-lapachone may prove to be a promising anticancer agent that can target cancer cells, especially those with mutant p53.     

Knockdown of the inducible nitric oxide synthase (NOS2) splicing variant S3 promotes autophagic cell death from nitrosative stress in SW480 human colon cancer cells

Low levels of nitric oxide (NO) produced by constitutively expressed inducible NO synthase (NOS2) in tumor cells may be an important factor in their development. NOS2 expression is associated with high mortality rates for various cancers. Alternative splicing of NOS2 down-regulates its enzymatic activity, resulting in decreased intracellular NO concentrations. Specific probes to detect alternative splicing of NOS2 were used in two isogenic human colon cancer cell lines derived either from the primary tumor (SW480) or from a lymph node metastasis (SW620). Splicing variant of NOS2 S3, lacking exons 9, 10, and 11, was overexpressed in SW480 cells. NOS2 S3 was silenced in SW480 cells. Flow-cytometry analysis was used to estimate the intracellular NO levels and to analyze the cell cycle of the studied cell lines. Western blot analysis and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine apoptosis and autophagy markers. SW480 and SW620 cells expressed NOS2 S3. Overexpression of the NOS2 S3 in SW480 cells downregulated intracellular NO levels. SW480 cells with knocked down NOS2 S3 (referred to as S3C9 cells) had higher intracellular levels of NO compared to the wild-type SW480 cells under serum restriction. Higher NO levels resulted in the loss of viability of S3C9 cells, which was associated with autophagy. Induction of autophagy by elevated intracellular NO levels in S3C9 cells under serum restriction, suggests that autophagy operates as a cytotoxic response to nitrosative stress. The expression of NOS2 S3 plays an important role in regulating intracellular NO production and maintaining viability in SW480 cells under serum restriction. These findings may prove significant in the design of NOS2/NO-based therapies for colon cancer.     

Multiplex Flow Cytometry Barcoding and Antibody Arrays Identify Surface Antigen Profiles of Primary and Metastatic Colon Cancer Cell Lines

Colon cancer is a deadly disease affecting millions of people worldwide. Current treatment challenges include management of disease burden as well as improvements in detection and targeting of tumor cells. To identify disease state-specific surface antigen signatures, we combined fluorescent cell barcoding with high-throughput flow cytometric profiling of primary and metastatic colon cancer lines (SW480, SW620, and HCT116). Our multiplexed technique offers improvements over conventional methods by permitting the simultaneous and rapid screening of cancer cells with reduced effort and cost. The method uses a protein-level analysis with commercially available antibodies on live cells with intact epitopes to detect potential tumor-specific targets that can be further investigated for their clinical utility. Multiplexed antibody arrays can easily be applied to other tumor types or pathologies for discovery-based approaches to target identification.     

Effect of selenite combined with chemotherapeutic agents on the proliferation of human carcinoma cell lines

Selenite is frequently used in combination with cancer chemotherapeutic agents to reduce side effects. However, the cytoprotective activity of selenite may also reduce the efficacy of chemotherapeutic drugs on tumor cells. This study was designed to examine the effects of selenite combined with cytotoxic agents used in clinical protocols [e.g., doxorubicine, docetaxel, 5-fluorouracil (5-FU), methotrexate (MTX), mafosphamide, mitomycin C, gemcitabine, etoposide, cisplatin, irinotecan, and oxaliplatin] on the proliferation of various carcinoma cell types. The data demonstrated that selenite had no marked effects on the antiproliferative activity of docetaxel, doxorubicine, 5-FU, MTX, and mafosphamide in MDA-MB-231 breast cancer cells. Likewise, no consistent changes were observed in A549 lung cancer cell proliferation when selenite was combined with cisplatin, etoposide, gemcitabine, or mitomycin C. On the other hand, selenite potentiated the cytotoxicity of 5-FU, oxaliplatin, and irinotecan in HCT116 colon cancer cells by approx 1.1-fold, 2.7-fold, and 2.6-fold, respectively. In SW620 colon cancer cells, selenite induced a 1.5-fold and 4.3-fold increase of the antiproliferative activity of 5-FU and oxaliplatin, respectively. Whereas irinotecan showed no effects on SW620 cell growth, a combination with selenite resulted in 23% inhibition. Our results indicate that selenite did not reduce the antiproliferative activity of chemotherapeutic agents in vitro. In addition, selenite was able to increase the inhibitory activity of docetaxel in A549 lung cancer cells, and of 5-FU, oxaliplatin, and irinotecan in HCT116 and SW620 colon cancer cells implying selenite is potentially useful as an adjuvant chemotherapeutic agent.