Cellular response to 5-fluorouracil (5-FU) in 5-FU-resistant colon cancer cell lines during treatment and recovery

Background  

Treatment of cells with the anti-cancer drug 5-fluorouracil (5-FU) causes DNA damage, which in turn affects cell proliferation and survival. Two stable wild-type TP53 5-FU-resistant cell lines, ContinB and ContinD, generated from the HCT116 colon cancer cell line, demonstrate moderate and strong resistance to 5-FU, respectively, markedly-reduced levels of 5-FU-induced apoptosis, and alterations in expression levels of a number of key cell cycle- and apoptosis-regulatory genes as a result of resistance development. The aim of the present study was to determine potential differential responses to 8 and 24-hour 5-FU treatment in these resistant cell lines. We assessed levels of 5-FU uptake into DNA, cell cycle effects and apoptosis induction throughout treatment and recovery periods for each cell line, and alterations in expression levels of DNA damage response-, cell cycle- and apoptosis-regulatory genes in response to short-term drug exposure.     

Role of hMLH1 promoter hypermethylation in drug resistance to 5-fluorouracil in colorectal cancer cell lines

Loss of DNA mismatch repair (MMR) occurs in 10-15% of sporadic colorectal cancer, is usually caused by hMLH1 hypermethylation, and has been shown to confer resistance to various chemotherapeutic reagents, including 5-fluorouracil (5-FU). We tested the hypothesis that demethylation of the hMLH1 promoter in hypermethylated colorectal cancer cells would restore MMR proficiency and drug sensitivity to 5-FU. We used the MMR-deficient cell lines SW48, HCT116, HCT116+chr2 and the -proficient cell line HCT116+chr3. After treatment with the demethylating agent 5-Aza-2'-deoxycytidine (5 aza-dC), hMLH1 mRNA and protein expression were determined by RT-PCR and immunoblots. The methylation status for hMLH1 was investigated by methylation-specific PCR. Cells were subsequently treated with 5-FU and the growth characteristics ascertained by clonogenic assays. hMLH1 hypermethylation was reverted in SW48 cells 24 hr after treatment with 5 aza-dC and was accompanied by hMLH1 mRNA and protein reexpression. While 5 aza-dC alone did not affect the growth of SW48 cells, all other cell lines responded with a pronounced growth inhibition. 5-FU treatment strongly reduced the colony formation of HCT116+chr3 cells. These effects were significantly less in the MMR-deficient cells. Combined treatment of SW48 cells resulted in a similar growth pattern as seen in 5-FU only treated HCT116+chr3 cells. We demonstrate that in vitro resistance to 5-FU can be overcome by reexpression of hMLH1 protein through 5 aza-dC-induced demethylation in hypermethylated cell lines. Induction of the expression of methylated tumor suppressor or MMR genes could have a significant impact on the development of future chemotherapy strategies.     

The roles of thymidylate synthase and p53 in regulating Fas-mediated apoptosis in response to antimetabolites.

Fas (CD95/Apo-1) is a member of the tumor necrosis factor receptor family. Receptor binding results in activation of caspase 8, leading to activation of proapoptotic downstream molecules. We found that expression of Fas was up-regulated >10-fold in MCF-7 breast and HCT116 and RKO colon cancer cell lines after treatment with IC(60) doses of 5-fluorouracil (5-FU) and raltitrexed (RTX). Combined treatment with the agonistic Fas antibody CH-11 and either 5-FU or RTX resulted in a highly synergistic induction of apoptosis in these cell lines. Similar results were obtained for another antifolate, Alimta. Induction of thymidylate synthase expression inhibited Fas induction in response to RTX and Alimta, but not in response to 5-FU. Furthermore, thymidylate synthase induction abrogated the synergy between CH-11 and both antifolates but had no effect on the synergistic interaction between 5-FU and CH-11. Inactivation of p53 in MCF-7 and HCT116 cell lines blocked 5-FU- and antifolate-mediated up-regulation of Fas. Furthermore, Fas was not up-regulated in response to 5-FU or antifolates in the p53-mutant H630 colon cancer cell line. Lack of Fas up-regulation in the p53-null and -mutant lines abolished the synergistic interaction between 5-FU and CH-11. Interestingly, synergy was still observed between the antifolates and CH-11 in the p53-null HCT116 and p53-mutant H630 cell lines, although this was significantly reduced compared with the p53 wild-type cell lines. Our results indicate that Fas is an important mediator of apoptosis in response to both 5-FU and antifolates.     

Molecular characterizations of derivatives of HCT116 colorectal cancer cells that are resistant to the chemotherapeutic agent 5-fluorouracil

5-Fluorouracil (5-FU) is the chemotherapeutic drug of choice for the treatment of metastatic colorectal cancer, but resistance to 5-FU remains a major obstacle to successful therapy. We generated 5-FU-resistant derivatives of the HCT116 human colon cancer cell line by serial passage of these cells in the presence of increasing 5-FU concentrations in an attempt to elucidate the biological mechanisms involved in resistance to 5-FU. Two resultant resistant derivatives, HCT116 ResB and ResD, were characterized for resistance phenotypes, genotypes, and gene expression using cells maintained long-term in 5-FU-free media. Compared to parental HCT116 cells that respond to 5-FU challenge by inducing high levels of apoptosis, ResB and ResD derivatives had significantly reduced apoptotic fractions when transiently challenged with 5-FU. ResB and ResD cells were respectively 27- and 121-fold more resistant to 5-FU, had increased doubling times, and significantly increased plating efficiencies compared to the parental cells. Both resistant derivatives retained the wild-type TP53 genotype, TP53 copy number and CGH profile characteristic of the parental line. Alterations in gene expression in the resistant derivatives compared to the parental line were assessed using oligonucleotide microarrays. Overall, the 5-FU-resistant derivatives were characterized by reduced apoptosis and a more aggressive growth phenotype, consistent with the observed up-regulation of apoptosis-inhibitory genes (e.g., IRAK1, MALT1, BIRC5), positive growth-regulatory genes (e.g., CCND3, CCNE2, CCNF, CYR61), and metastasis genes (e.g., LMNB1, F3, TMSNB), and down-regulation of apoptosis-promoting genes (e.g., BNIP3, BNIP3L, FOXO3A) and negative growth-regulatory genes (e.g., AREG, CCNG2, CDKN1A, CDKN1C, GADD45A). 5-FU metabolism-associated genes (e.g., TYMS, DTYMK, UP) and DNA repair genes (e.g., FEN1, FANCG, RAD23B) were also up-regulated in one or both resistant derivatives, suggesting that the resistant derivatives might be able to overcome both 5-FU inhibition of thymidylate synthase and the DNA damage caused by 5-FU, respectively. Development of 5-FU resistance thus appears to encompass deregulation of apoptosis-, proliferation-, DNA repair-, and metastasis-associated regulatory pathways.     

Toxicity of levamisole and 5-fluorouracil in human colon carcinoma cells

The combination of 5-fluorouracil (5-FU) with the immunomodulator levamisole (Lev) has been clinically tested in patients with metastatic colorectal carcinoma and as adjuvant therapy following primary tumor surgery. In some studies in advanced disease, the addition of Lev to 5-FU improved the median duration of response; in the adjuvant setting, the combination was associated with improvement in the disease-free survival. We studied whether Lev was directly toxic to three human colorectal carcinoma cell lines (HCT 116, SNU-C4, and NCI-H630). We also evaluated the toxicity of Lev in combination with 5-FU in these three cell lines. Lev inhibited the growth of all three colorectal cell lines, but only at concentrations two logs above that achieved with a standard 150-mg oral dose of Lev. In cell growth studies, 500 and 1,000 microM Lev increased the toxicity of 5-FU in HCT 116 cells in an additive fashion. In clonogenic assays, continuous exposure to 10 or 100 microM Lev was minimally toxic and did not enhance the lethality associated with a 24-hour exposure to 5-FU in any of the cell lines. Lev alone at 1,000 microM decreased colony formation by 45% in HCT 116 cells. A combination of 1,000 microM Lev with 10 microM 5-FU resulted in a decrease in HCT 116 colony formation from 54% to 6% of control levels. Continuous exposure of NCI-H630 cells to 500 microM Lev decreased colony formation to 76.5% of control levels; when Lev was combined with 50 microM 5-FU, colony formation was decreased from 59.5% to 27.5% of control levels. We conclude that at concentrations achievable with conventional doses of Lev, there was no evidence of direct toxicity in these colorectal cell lines. Furthermore, an additive interaction with 5-FU was evident only at suprapharmacologic doses of Lev.     

Heat shock protein 27, a novel regulator of 5-fluorouracil resistance in colon cancer

The resistance of colon cancer to 5-fluorouracil (5-FU) is a critical issue, and the cause of this resistance cannot always be explained based on the known molecules. Heat shock protein 27 (HSP27) mRNA expression has recently been shown to be correlated with 5-FU resistance in 5-FU-resistant cell lines. In this study, we attempted to elucidate the functional mechanism of HSP27 in 5-FU resistance in colon cancer. HSP27 protein levels in several human colon cancer cell lines (LoVo, HCT15, WiDr, HCT116, HT-29 and SW480) were determined by immunoblot and densitometry analysis. The in vitro growth inhibition rates (IR) of the cell lines at various concentrations of 5-FU were assessed by MTT assay. The degree of 5-FU resistance was estimated as the drug concentration inducing 50% IR (IC50). The HSP27 protein level and IC50 were significantly correlated in these cell lines (p=0.010). The effect of HSP27 overexpression on IC50 was evaluated in LoVo cells. HSP27 transfectants significantly increased IC50 and reduced HSP27 resistance. The effect of HSP27 down-regulation by HSP27 siRNA on IC50 was confirmed in HCT15 cells. HSP27 siRNA suppressed HSP27 protein levels and reduced IC50 in a dose-dependent manner. These data indicated that HSP27 is closely connected with 5-FU resistance in colon cancer and suggested that HSP27 levels predicted 5-FU resistance. HSP27 down-regulation overcame 5-FU resistance and HSP27 may be a clinical target in patients with 5-FU-resistant colon cancer.     

Mechanisms of acquired chemoresistance to 5-fluorouracil and tomudex: thymidylate synthase dependent and independent networks

Purpose Thymidylate synthase (TS) over-expression is widely accepted as a major molecular mechanism responsible for 5-fluorouracil (5-FU) and tomudex (TDX) resistance. In this study, the importance of TS in 5-FU and TDX resistance was evaluated. Methods The sensitivity of TS-over-expressing 5-FU (3) and TDX (3) resistant cell lines to 5-FU and TDX was analysed. The cross-resistance between 5-FU and TDX resistant cell lines was determined. The relationship between p53 and NF-κB status and the sensitivity to 5-FU and TDX was evaluated. Results Compared to relevant parental sensitive cell lines, the 5-FU resistant cell lines were highly cross-resistant to TDX (over 20,000-fold). In contrast, over-expression of TS did not significantly confer 5-FU resistance on the TDX resistant cell lines (0.8- to 1.3-fold). Thymidine (20 μM) rescue induced TDX resistance in TDX sensitive cell lines (over 10,000-fold) but only moderately influenced 5-FU sensitivity in 5-FU sensitive cell lines (1.1- to 2.4-fold). Uridine moderately protected one cancer cell line (RKO) from 5-FU-induced, but not TDX-induced, cytotoxicity. NF-κB transfected MCF-7 and p53 knockout HCT116 cells were resistant to 5-FU (4.4- and 2.4-fold, respectively) but not to TDX. TS protein expression in NF-κB transfected and p53 knockout cell lines was comparable to the relevant parental cell lines. Conclusion In some cancer cell lines, TS-independent molecular events may play a key role in 5-FU resistance. Loss of p53 function and NF-κB over-expression may be involved in TS-independent 5-FU chemoresistance in some cancer cell lines.     

Dual antitumor effects of 5-fluorouracil on the cell cycle in colorectal carcinoma cells: a novel target mechanism concept for pharmacokinetic modulating chemotherapy

5-Fluorouracil (5-FU) is one of the most widely used anticancer agents for advanced colorectal carcinoma, but its response rate is only 15%. The "pharmacokinetic modulating chemotherapy" (PMC) regimen that we have advocated has proved to be highly effective in treating colorectal carcinoma. PMC consists of a continuous i.v. infusion of 5-FU over 24 h for 1day a week at 600 mg/m2/day, and an oral dose of uracil-tegafur (UFT), a 5-FU derivative, at 400 mg/day for 5-7 days per week, repeated every week for more than 6 months. Assays of 5-FU in 23 patients receiving this treatment showed serum concentrations ranging from 88 to 1,323 ng/ml. We then analyzed the effects of clinically relevant concentrations of 5-FU found in colorectal cancer patients treated with the PMC regimen on the growth of three human colorectal adenocarcinoma cell lines, SW480 and COLO320DM (mutant p53) and HCT116 (wild-type p53). Exposure of these three cell lines to 5-FU resulted in growth inhibition in a dose-dependent manner. Exposure to 100 ng/ml of 5-FU in SW480 and COLO320DM caused G1 arrest after 24 h and G2 arrest after 72-144 h, and only a minority of the cell population showed apoptotic features, which indicated that most of the cells were killed through mitotic catastrophe, nonapoptotic cell death. On the contrary, exposure to 1000 ng/ml of 5-FU in SW480 and COLO320DM resulted in G1-S-phase arrest and the induction of apoptosis throughout the experimental period. Nuclear cyclin B1 expression was markedly induced with exposure to 100 ng/ml of 5-FU in SW480 and COLO320DM; and expression of 14-3-3sigma protein, a cell cycle inhibitor in the GG phase, was induced in SW480. ICT116 responded to lower concentrations of 5-FU more rapidly: G2 arrest was seen after 24-72 h of exposure to 10 ng/ml of 5-FU, and G,1rrest was seen after 12-24 h of exposure to 100 ng/ml. These results show that 5-FU acts via two different pathways, depending on dose: (a) G,1S-phase cell cycle arrest and apoptosis at 1,000 ng/ml in SW480 and COLO320DM, and 100 ng/ml in HCT116; and (b) G2-M-phase cell cycle arrest and mitotic catastrophe at 100 ng/ll in SW480 and COLO320DM, and 10 ng/ml in HCT116. These results suggest that the efficacy of our PMC regimen is based on targeting at least two different phases of the cell cycle. In our clinical trial, we showed efficacy independent of p53 status, ascertained by cell kinetic analysis in vitro, which may lead to a novel concept of schedule-oriented biochemical modulation of this drug.     

Proliferating cell nuclear antigen as a predictor of therapeutic effect of continuous 5-fluorouracil administration in gastric cancer

The change of proliferating cell nuclear antigen (PCNA) expression was examined in three gastric cancer cell lines, MKN28, MKN45 and MKN74, during continuous or bolus exposure to 5-fluorouracil (5-FU). The cytotoxic effect of 5-FU was almost the same in all the cells. PCNA expression was higher at 24 and 72 h after continuous 5-FU treatment than before treatment. Continuous 5-FU treatment of cells revealed higher expression of PCNA protein and mRNA than did bolus treatment. Flow cytometry revealed that 5-FU increased cell population at the late G1 or S phase 24 and 72 h after treatment. PCNA values at the late G1 and S phase were significantly higher than those at other phases 24 h after treatment. These results suggest that PCNA expression increased due to cell cycle accumulation at late G1 and S phases. Thus PCNA values just after chemotherapy of gastric cancer may be useful in predicting the therapeutic effects of continuous 5-FU administration.     

Violacein synergistically increases 5-fluorouracil cytotoxicity, induces apoptosis and inhibits Akt-mediated signal transduction in human colorectal cancer cells

Despite recent additions to the armory of chemotherapeutic agents for colorectal cancer (CRC) treatment, the results of chemotherapy remain unsatisfactory. 5-Fluorouracil (5-FU) still represents the cornerstone of treatment and resistance to its actions is a major obstacle to successful chemotherapy. Therefore, new active agents in CRC and agents that increase the chemosensitivity of cancer cells to 5-FU are still urgently required. Violacein, a pigment isolated from Chromobacterium violaceum in the Amazon river, has a diverse spectrum of biological activities, and represents a novel cytotoxic drug with known antileukemic properties. To assess the suitability of violacein as a chemotherapeutic agent in CRC its cytotoxic effects were evaluated both as a single agent and in combination with 5-FU. Its underlying mechanisms of action were further investigated by studying its effects on the cell cycle, apoptosis and cell survival pathways [phosphatidylinositol-3-kinase/Akt, p44/42 mitogen activated protein kinase and nuclear factor kappaB (NF-kappaB)] in colon cancer cell lines. Violacein inhibits the growth of all four colon cancer cell lines tested. It induces apoptosis, and potentiates the cytotoxic effect of 5-FU in a poorly differentiated microsatellite unstable cell line (HCT116). Violacein causes cell cycle block at G(1), upregulates p53, p27 and p21 levels and decreases the expression of cyclin D1. Violacein leads to dephosphorylation of retinoblastoma protein and activation of caspases and a pancaspase inhibitor abrogates its biological activity. Our data provide evidence that violacein acts through the inhibition of Akt phosphorylation with subsequent activation of the apoptotic pathway and downregulation of NF-kappaB signaling. This leads to the increase in chemosensitivity to 5-FU in HCT116 colon cancer cells. Taken together, our findings suggest that violacein will be active in the treatment of colorectal tumors and offers new prospects for overcoming 5-FU resistance.     

The potential clinical value of GML and the p53 gene as a predictor of chemosensitivity for colorectal cancer

Background. Adjuvant chemotherapy with 5-fluorouracil (5-FU) and mitomycin C (MMC) has commonly been used after resection of colorectal cancer. The aim of this study was to determine the predictive value of p53 mutation or the expression of GML, a target of p53, for sensitivity to 5-FU and MMC. Methods. We analyzed p53 mutations and the expression of GML in six colorectal cancer cell lines (SW837, DLD-1, RPMI4788, WiDr, HT-29, and HCT116), and examined the correlation between genetic changes and in-vitro chemosensitivity to MMC and 5-FU by measuring the colony-forming ability in these cell lines. We also introduced GML cDNA into a cell line that lacked endogenous GML expression to investigate changes in sensitivity to MMC and 5-FU. Results. The sensitivity to MMC was highest in HCT116, which had no p53 gene abnormalities and expressed endogenous GML, and lowest in RPMI4788 cells, which had neither p53 gene abnormalities nor expression of endogenous GML. For 5-FU treatment with 24-h exposure, HCT116 showed the highest sensitivity, and SW837, which had p53 mutations without expression of GML, showed the lowest sensitivity. The introduction of GML cDNA to RPMI4788 (RPMI4788-GML) showed that the sensitivity of RPMI4788-GML to MMC was enhanced almost to the level of HCT116 cells. However, when RPMI4788-GML were exposed to 5-FU for 24 h, the sensitivity of RPMI4788-GML was slightly increased compared with that of the parental cells, but was slightly lower than that of HCT116. Conclusion. GML expression and p53 mutation in colorectal cancer may be useful predictive genetic markers for sensitivity to MMC and 5-FU, respectively. Received: June 30, 2000 / Accepted: December 8, 2000     

Oncogenic Ras increases sensitivity of colon cancer cells to 5-FU-induced apoptosis

Despite the fact that objective response rates to 5-FU are as low as 20%, 5-FU remains the most commonly used drug for the treatment of colorectal cancer. The lack of understanding of resistance to 5-FU, therefore, remains a significant impediment in maximizing its efficacy. We used intestinal epithelial cells with an inducible K-RasV12 to demonstrate that expression of oncogenic Ras promotes cell death upon 5-FU treatment. Accordingly, transient expression of the mutant RasV12, but not the WT Ras, enhanced 5-FU-induced apoptosis in 293T cells. Consistent with these data, we showed that targeted deletion of the mutant Ras allele in the HCT116 colon cancer cell line protected cells from 5-FU-induced apoptosis. Using isogenic colon cancer cell lines that differ only by the presence of the mutant Ras allele, HCT116 and Hke-3 cells, we demonstrated that signaling by oncogenic Ras promotes both accumulation of p53 and its phosphorylation on serine15 in response to 5-FU, a situation that favors apoptosis over growth arrest. However, despite the differential induction of p53 in HCT116 and Hke-3 cells, the expression of Puma, a gene with an important role in p53-dependent apoptosis, was not affected by Ras signaling. In contrast, we showed that Ras interferes with 5-FU-induced expression of gelsolin, a protein with known antiapoptotic activity. We ascertained the role of gelsolin in 5-FU-induced apoptosis by demonstrating that silencing of gelsolin expression through RNAi sensitized cells to 5-FU-induced apoptosis and that re-expression of gelsolin in cells harboring mutant Ras protected cells from 5-FU-induced apoptosis. These data therefore demonstrate that Ras mutations increase sensitivity to 5-FU-induced apoptosis at least in part through the negative regulation of gelsolin expression. Our data indicate that Ras mutations promote apoptosis in response to 5-FU treatment and imply that tumors with Ras mutations and/or reduced expression of gelsolin may show enhanced apoptosis in response to 5-FU also in vivo.     

Gelam Honey and Ginger Potentiate the Anti Cancer Effect of 5-FU against HCT 116 Colorectal Cancer Cells

The development of chemopreventive approaches using a concoction of phytochemicals is potentially viablefor combating many types of cancer including colon carcinogenesis. This study evaluated the anti-proliferativeeffects of ginger and Gelam honey and its efficacy in enhancing the anti-cancer effects of 5-FU (5-fluorouracil)against a colorectal cancer cell line, HCT 116. Cell viability was measured via MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphenyl)-2H-tetrazolium) assay showing ginger inhibiting the growthof HCT 116 cells more potently (IC50 of 3mg/mL) in comparison to Gelam honey (IC50 of 75mg/mL). Combinedtreatment of the two compounds (3mg/mL ginger+75mg/mL Gelam honey) synergistically lowered the IC50 ofGelam honey to 22mg/mL. Combination with 35 mg/mL Gelam honey markedly enhanced 5-FU inhibitingeffects on the growth of HCT 116 cells. Subsequent analysis on the induction of cellular apoptosis suggestedthat individual treatment of ginger and Gelam honey produced higher apoptosis than 5-FU alone. In addition,treatment with the combination of two natural compounds increased the apoptotic rate of HCT 116 cells dosedependentlywhile treatment of either ginger or Gelam honey combined with 5-FU only showed modest changes.Combination index analysis showed the combination effect of both natural compounds to be synergistic in theirinhibitory action against HCT 116 colon cancer cells (CI 0.96 < 1). In conclusion, combined treatment of Gelamhoney and ginger extract could potentially enhance the chemotherapeutic effect of 5-FU against colorectal cancer.     

Survival of colorectal cancer cell lines treated with paclitaxel, radiation, and 5-FU: effect of TP53 or hMLH1 deficiency

Clonogenic survival and early cell death during treatment of human colon carcinoma cells were investigated following X-irradiation (IR) alone, IR followed by 5-FU for 24 h, and Taxol administered 24 h before IR and 5F-U. The investigated cell lines were: HCT116, 40-16 clonally derived from HCT116, and two HCT116 variants: N6CHR3 expressing hMLH1, and TP53 null cells denoted HCT116 p53-/-. The objective was to determine efficacy of the combined treatment and to correlate response with constitutive levels of TP53, WAF1, and hMLH1 proteins, as well as with mRNA levels of the apoptosis-related genes survivin, BNIP3, and MYC. At the end of treatment with 5-FU, the proportion of viable cells was between 0.65 and 0.70 for all cell lines. Additional cell loss occurred in 40-16 and HCT116 p53-/- cells following administration of Taxol before IR and 5-FU. Radiation sensitivity was unaffected by combined treatments, except for Taxol, irradiation, and 5-FU sequence in the HCT116 p53-/- and 40-16 cell lines, where radiation sensitivity determined by clonogenic survival curve slopes was doubled or quadrupled, respectively. Under our present experimental conditions, treatment response did not correlate with TP53 or hMLH1 status, but was associated with apoptosis-related genes, most notably BNIP3. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 175-185 (2000).     

Microarray Analysis of Long Non-coding RNA Expression Profile Associated with 5-Fluorouracil-Based Chemoradiation Resistance in Colorectal Cancer Cells

Background: Preoperative 5-fluorouracil (5-FU)-based chemoradiotherapy is a standard treatment for locallyadvanced colorectal cancer (CRC). However, CRC cells often develop chemoradiation resistance (CRR). Recentstudies have shown that long non-coding RNA (lncRNA) plays critical roles in a myriad of biological processesand human diseases, as well as chemotherapy resistance. Since the roles of lncRNAs in 5-FU-based CRR inhuman CRC cells remain unknown, they were investigated in this study. Materials and Methods: A 5-FU-basedconcurrent CRR cell model was established using human CRC cell line HCT116. Microarray expression profilingof lncRNAs and mRNAs was undertaken in parental HCT116 and 5-FU-based CRR cell lines. Results: In total,2,662 differentially expressed lncRNAs and 2,398 mRNAs were identified in 5-FU-based CRR HCT116 cellswhen compared with those in parental HCT116. Moreover, 6 lncRNAs and 6 mRNAs found to be differentiallyexpressed were validated by quantitative real time PCR (qRT-PCR). Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway analysis for the differentially expressed mRNAs indicated involvement of many, such as Jak-STAT, PI3K-Akt and NF-kappa B signaling pathways. To better understand the molecular basis of 5-FU-basedCRR in CRC cells, correlated expression networks were constructed based on 8 intergenic lncRNAs and theirnearby coding genes. Conclusions: Changes in lncRNA expression are involved in 5-FU-based CRR in CRCcells. These findings may provide novel insight for the prognosis and prediction of response to therapy in CRCpatients.