Thymidylate Synthase In Colorectal Cancer Research Articles

MicroRNA-375-3p enhances chemosensitivity to 5-fluorouracil by targeting thymidylate synthase in colorectal cancer.

Resistance to chemotherapy is a major challenge for the treatment of patients with colorectal cancer (CRC). Previous studies have found that microRNAs (miRNAs) play key roles in drug resistance; however, the role of miRNA‐373‐3p (miR‐375‐3p) in CRC remains unclear. The current study aimed to explore the potential function of miR‐375‐3p in 5‐fluorouracil (5‐FU) resistance. MicroRNA‐375‐3p was found to be widely downregulated in human CRC cell lines and tissues and to promote the sensitivity of CRC cells to 5‐FU by inducing colon cancer cell apoptosis and cycle arrest and by inhibiting cell growth, migration, and invasion in vitro. Thymidylate synthase (TYMS) was found to be a direct target of miR‐375‐3p, and TYMS knockdown exerted similar effects as miR‐375‐3p overexpression on the CRC cellular response to 5‐FU. Lipid‐coated calcium carbonate nanoparticles (NPs) were designed to cotransport 5‐FU and miR‐375‐3p into cells efficiently and rapidly and to release the drugs in a weakly acidic tumor microenvironment. The therapeutic effect of combined miR‐375 + 5‐FU/NPs was significantly higher than that of the individual treatments in mouse s.c. xenografts derived from HCT116 cells. Our results suggest that restoring miR‐375‐3p levels could be a future novel therapeutic strategy to enhance chemosensitivity to 5‐FU.

Inhibition of NF-κB translocation by curcumin analogs induces G0/G1 arrest and downregulates thymidylate synthase in colorectal cancer

Cell cycle progression and DNA synthesis are essential steps in cancer cell growth and resistance. Thymidylate synthase (TS) is a therapeutic target for 5FU. Curcumin is a potent inhibitor of NF-κB. EF31 and UBS109 are potent synthetic analogues of curcumin. We tested the hypothesis that inhibition of NF-κB translocation by curcumin and its analogs EF31 and UBS109 can inhibit cell cycle progression and downregulate TS levels in colorectal cancer (CRC) cell lines. Two CRC cell lines (HCT116 and HT-29) were either untreated (control) or treated with IC50 concentrations of curcumin, EF31 UBS109 led to G0/G1 cell cycle arrest. Treatment with curcumin, EF31 or UBS109 inhibited NF-κB, downregulated survival pathways and inhibited cell cycle progression. Arrest in the G0/G1 phase was associated with downregulation of the transcription factor E2F-1 and its target gene TS. NF-κB over-expression induced E2F-1 and TS protein and mRNA levels in both cell lines. EF31 and UBS109 treatment significantly decreased tumor growth in compared to untreated tumors. EF31 and UBS109 are promising agents for the prevention and treatment of CRC.

E2F1/TS Immunophenotype and Survival of Patients with Colorectal Cancer Treated with 5FU-Based Adjuvant Therapy.

The predictive value of thymidylate synthase (TS) expression alone for 5FU-based treatment of colorectal cancer (CRC) has not been clinically confirmed. Little is known on the association of expression of E2F1, which controls the transcription of genes encoding proteins engaged in DNA synthesis including TS, and survival of patients with CRC. The purpose of this study is to assess the correlation between expression of both E2F1 and TS in CRCs and survival of patients administered adjuvant 5FU-based chemotherapy, in order to find a better predictor of treatment outcome than expression of TS or E2F1 alone. Nuclear TS and E2F1 were detected by immunohistochemistry in tissue microarrays from 190 CRCs (Astler-Coller stage B2 or C). Multivariate analysis identified significant association of the combined E2F1+TS+ immunophenotype with worse OS (HR = 3,78, P = 0,009) and DFS (HR = 2,30, P = 0,03) of patients with colon cancer. There were significant differences between E2F1+TS+ and E2F1-TS- Kaplan-Meier survival curves in relation to DFS (P = 0.008) and OS (P = 0.01). About 37 and 31 % difference in 3-year DFS and OS respectively were seen between patients with E2F1+TS+ vs. E2F1-TS- colon cancer immunophenotype. The E2F1+TS+ immunophenotype may be a marker of poor prognosis (the worst DFS and OS) of patients with colon cancer treated with 5FU-based adjuvant therapy. A subgroup of patients with this immunophenotype may require different and perhaps more aggressive treatment than 5FU-based chemotherapy. Thus, the combined E2F1/TS immunophenotype could be a potential indicator of colon cancer sensitivity to 5FU.

MicroRNA-218 is a prognostic indicator in colorectal cancer and enhances 5-fluorouracil-induced apoptosis by targeting BIRC5.

One major reason for the failure of advanced colorectal cancer (CRC) treatment is the occurrence of chemoresistance to fluoropyrimidine (FU)-based chemotherapy. Various reports showed that ectopic expression and function of microRNAs (miRNAs) played key roles to mediate apoptosis at the post-transcriptional level. To further explore the possible mechanisms, we evaluated the prognostic effect of miR-218 in patients with CRC receiving 5-FU-based treatment and investigated the proapoptotic role of miR-218 in vitro. Primary tumour specimens and adjacent non-tumour sites were used to determine miR-218 expression distribution and explore its potential prognostic value in response to 5-FU-based treatment in patients with CRC. HCT116 and HT29 cells were transfected with precursor miR-218 or negative control, followed by assays to investigate its influence on apoptosis, cell proliferation and pathways involved in molecular mechanisms of chemoresistance to 5-FU. Results showed that high miR-218 expression was associated with positive response to firstline 5-FU treatment in CRC patients. MiR-218 promoted apoptosis, inhibited cell proliferation and caused cell cycle arrest in CRC cells by suppressing BIRC5 expression. Furthermore, miR-218 enhanced 5-FU cytotoxicity in CRC cells by suppressing the 5-FU targeted enzyme, thymidylate synthase (TS). In conclusion, we demonstrated that high miR-218 expression had a positive prognostic value in 5-FU-based treatments for CRC patients and discovered a novel mechanism mediated by miR-218 to promote apoptosis and to function synergistically with 5-FU to promote chemosensitivity by suppressing BIRC5 and TS in CRC. These suggest the unique potential of miR-218 as a novel candidate for developing miR-218-based therapeutic strategies in CRC.

Abstract 3778: Inhibition of NF-κB translocation induces G0/G1 arrest and downregulates thymidylate synthase in colorectal cancer

Abstract Purpose Objectives: Cell cycle progression and DNA synthesis are essential steps in cancer cell growth and resistance. Thymidylate synthase (TS) is a therapeutic target for 5FU. Curcumin is a potent inhibitor of NF-κB. We tested the hypothesis that NF-κB translocation inhibition by curcumin and its analogs can inhibit cell cycle progression and downregulate TS levels in colorectal cell lines. Methods: Two colorectal cancer cell lines were usedHCT-116 and HT-29. Cells were either untreated (control) or treated with curcumin (20μM), EF31 (7.5μM for HCT-116 and 2.5μM for HT-29) and UBS109 (620nM for HCT-116 and 1.25μM for HT-29) for 24 hours. Western blot and RT-PCR analyses were carried out to determine the effect of curcumin and its analogues EF31 and UBS109 on different signal molecules involved in cell cycle arrest and DNA synthesis. Electromobility shift assay (EMSA) was performed in colon cancer cells to evaluate the effects of curcumin and its analogues on NF-κB activity. A subcutaneous xenograft mouse model was used to evaluate the in vivo effects of curcumin analogues. Results: Treatment with curcumin and its analogues inhibited cyclin D1, pRb and E2F-1 at the transcriptional and translational level and induced p21, leading to G0/G1 cell cycle arrest. NF-κB over-expression induced E2F-1 and TS protein and mRNA levels in both cell lines. Arrest in the G0/G1 phase was associated with downregulation of the transcription factor E2F-1 and its target gene TS. Similar effects were observed in tumors from animals treated with EF31 and UBS109. Further, EF31 and UBS109 treatment significantly decreased the tumor growth compared to untreated tumors. Conclusion: In this study, we present in vitro and in vivo data to support the use of curcumin analogs in colorectal cancer based on their ability to reduce expression of proteins important for DNA repair and cell cycle progression leading to cell cycle arrest and tumor shrinkage. Accordingly, combining curcumin analogs with chemotherapy is a rational approach for future drug development in colorectal cancer. Citation Format: Ganji Purnachandra Nagaraju, Alese Olatunji, Sandhya Gupta, Mamoru Shoji, Bassel F. El-Rayes. Inhibition of NF-κB translocation induces G0/G1 arrest and downregulates thymidylate synthase in colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3778. doi:10.1158/1538-7445.AM2015-3778

MicroRNA-197 influences 5-fluorouracil resistance via thymidylate synthase in colorectal cancer.

The response rate of first-line fluoropyrimidine-based regimens for metastatic colorectal cancer (mCRC) is generally less than 50%. The down-regulation of miR-197 in colorectal cancer cells after exposure to 5-fluorouracil might be related to the mechanism of resistance to fluoropyrimidine-based chemotherapy. So we investigated the regulatory mechanism of miR-197 on 5-FU sensitivity. Dual luciferase reporter gene construct and dual luciferase reporter assay were used to identify the target of miR-197. TYMS expression was evaluated by immunohistochemistry staining. 5-Fu resistance of colorectal cancer cell lines was detected by MTS assay. The expression of miR-197 was detected by real time PCR. A luciferase assay and western blot analysis confirmed that miR-197 directly binds to and negatively regulates TYMS expression. Overexpressing miR-197 could increase the sensitivity of colorectal cancer cells to 5-fluorouracil (5-FU). The expression of miR-197 negatively correlated with TYMS expression in cancerous tissues from patients with stage IV colorectal cancer. miR-197 mediates the response of colorectal cancer cells to 5-FU by regulating TYMS expression.

MiR-203 enhances chemosensitivity to 5-fluorouracil by targeting thymidylate synthase in colorectal cancer.

MicroRNAs (miRNAs) are a conserved class of small non-coding RNAs that play important roles in diverse biological processes, including chemoresistance. However, the molecular mechanism as to how miR-203 modulates the chemosensitivity to 5-fluorouracil (5-FU) in colorectal cancer is poorly known. In the present study, we found that miR-203 was downregulated in the 5-FU-resistant cell line LoVo/5-Fu, and was inversely correlated with the extent of 5-FU chemoresistance. Cytotoxicity assay showed that the inhibition of miR-203 expression enhanced 5-FU chemoresistance in colorectal cancer cells, while miR-203 overexpression increased 5-FU chemosensitivity. We then validated that thymidylate synthase (TYMS) was a direct target of miR-203 and miR-203 suppressed TYMS protein levels. Silencing of TYMS enhanced 5-FU chemosensitivity, similar to the roles of miR-203. Finally, we discovered that miR-203 increased the inhibitory effects of 5-FU on tumor growth in vivo. Overall, our data indicate that miR-203 enhances 5-FU chemosensitivity via the downregulation of TYMS in colorectal cancer and provide important insight into the mechanism of 5-FU resistance in colorectal cancer patients. More important, the present study suggests that miR-203 has the potential as a therapeutic strategy for 5-FU-resistant colorectal cancer.

Abstract 1308: Functional inhibition of HSP90 induces G0/G1 arrest and downregulates thymidylate synthase in colorectal cancer

Abstract Purpose Objectives: Cell cycle progression and DNA synthesis are essential steps in cancer cell growth and resistance. Thymidylate synthase (TS) is a therapeutic target for 5FU. Ganetespib is a potent functional inhibitor of HSP90 currently under evaluation in clinical trials. We tested the hypothesis that HSP90 functional inhibition by ganetespib can inhibit cell cycle progression and downregulate TS levels in colorectal cell lines. Methods: Two colorectal cancer (CRC) cell lines were used, HCT-116 and HT-29. Cells were either untreated (control) or treated with ganetespib at 50 nM for 24 hours. Western blot and Real time-PCR analyses were carried out to determine the effect of ganetespib on different signal molecules involved in cell cycle arrest and DNA synthesis. A subcutaneous xenograft mouse model was used to evaluate the in vivo effects of ganetespib. Pre and post ganetespib treatment tumor biopsies from patients with rectal cancer on a phase I trial of ganetespib were analyzed using RT-PCR. Results: Treatment with ganetespib inhibited cyclin D1, pRb and E2F-1 at the transcriptional and translational level and induced p21, leading to G0/G1 cell cycle arrest. HSP90 knockdown inhibited E2F-1 and TS protein and mRNA levels in both cell lines. Arrest in the G0/G1 phase was associated with downregulation of the transcription factor E2F-1 and its target gene TS. Similar effects were observed in tumors from animals treated with ganetespib. Further, ganetespib treatment significantly inhibited the tumor growth. Inhibition of cyclin D1, Rb, E2F-1, TS and upregulation of p21 at transcriptional levels were observed in post treatment rectal tumor biopsies obtained from patients receiving ganetespib. Conclusion: In this study, we present preclinical and clinical data to support the use of HSP90 inhibitors in colorectal cancer based on their ability to reduce expression of proteins important for DNA repair and cell cycle progression leading to cell cycle arrest and tumor shrinkage. Accordingly, combining HSP90 inhibitors with chemotherapy is a rational approach for future drug development in colorectal cancer. Citation Format: Ganji Purnachandra Nagaraju, Field F. Willingham, Kevin E. Woods, Patrick Sullivan, Jerome C. Landry, Roberto Diaz, Bassel F. El-Rayes. Functional inhibition of HSP90 induces G0/G1 arrest and downregulates thymidylate synthase in colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1308. doi:10.1158/1538-7445.AM2014-1308

Role of topoisomerase I and thymidylate synthase expression in sporadic colorectal cancer: Associations with clinicopathological and molecular features

Topoisomerase I (Topo I) and thymidylate synthase (TS) are essential enzymes for the replication, transcription and repair of DNA, and are potential biomarkers in colorectal cancer (CRC). The aim of the study was to correlate the tissue expression of Topo I and TS in sporadic CRCs with relevant pathological and molecular features and patients’ outcome.Topo I and TS expression was assessed by immunostaining in 112 consecutive primary CRCs. Increased expression of Topo I was found in 36% of tumors, preferentially rectal (50%) and with not otherwise specified (NOS) histology (44%). Topo I expression was associated with 18q allelic loss (LOH), (p=0.013), microsatellite stable phenotype (p=0.002) and normal expression of mismatch proteins hMLH1 and hMSH2 (p=0.0012 and p=0.02, respectively). High TS expression was found in 60% of tumors, more frequently in distal sites (62%) and with NOS histology (66%); no association with microsatellite instability was observed.Topo I seems to be involved in the chromosomal instability pathway of sporadic CRCs. Conversely, high TS expression is unlikely to affect the clinical behavior of microsatellite unstable CRCs.

Targeting thymidylate synthase in colorectal cancer: critical re-evaluation and emerging therapeutic role of raltitrexed

Introduction: 5-fluorouracil continues to be the cornerstone of treatment for colorectal cancer. Although fluoropyrimidines are generally considered as well-tolerated drugs, severe toxicities can be a major clinical problem, and the recommended prolonged infusion of 5-fluorouracil provokes discomfort in patients. Raltitrexed (Tomudex), a quinazoline analogue of folinic acid, is a selective and direct thymidylate synthase (TS) inhibitor with a convenient 3-weekly schedule of administration.Areas covered: In this review, through critical insight into the mechanism of action and main clinical experiences, the authors suggest the necessity to reconsider raltitrexed as a valuable anticancer drug and as a suitable option for colorectal cancer. The authors highlight its emerging therapeutic role in clinical practice for patients with fluoropyrimidine-induced cardiotoxicity or a significant history of cardiac disease.Expert opinion: This review discusses if TS could still be a relevant target for colorectal cancer in the era of molecular therapy and if raltitrexed should still be considered a drug with a life-threatening toxicity. Furthermore, this review discusses the principal combination clinical experiences of raltitrexed and its emerging therapeutic role in clinical practice as a suitable option for colorectal cancer patients with fluoropyrimidine-induced cardiotoxicity or a significant history of cardiac disease.

Correlation between Efficacy of Irinotecan and Thymidylate Synthase in Colorectal Cancer

Correlation between Efficacy of Irinotecan and Thymidylate Synthase in Colorectal Cancer

Microsatellite Instability and the Association with Plasma Homocysteine and Thymidylate Synthase in Colorectal Cancer

The possible associations between microsatellite instability, homocysteine and thymidylate synthase were investigated in tumors and plasma from 130 patients with colorectal cancer. Other analyses included thymidylate synthase and 5,10-methylene-tetrahydrofolate reductase gene polymorphisms, carcinoembryonic antigen, vitamin B12, and folate. Microsatellite instability of tumors was associated with higher levels of plasma homocysteine (p = 0.008) and higher protein expression of thymidylate synthase (p < 0.001). Supplemental analyses ruled out that the finding could be explained by the other analyzed factors. CEA was not associated with neither homocysteine nor microsatellite instability. The data suggests that there is a more pronounced methyl unit deficiency in microsatellite instable tumors.

Validation of biomarkers associated with 5-fluorouracil and thymidylate synthase in colorectal cancer

Previous studies from our laboratory have identified a number of genes associated with chemosensitivity to 5-fluorouracil (5-FU) using an in vitro colon cancer cell line model. In this study, the in vivo significance of several marker genes in terms of prognostic potential was evaluated using colorectal cancer patient samples. Eight marker genes were selected based on their functional roles and significant fold changes in expression. They are SERTA domain containing 1 (SEI1), ribonucleotide reductase M2 polypeptide (RRM2), origin recognition complex, subunit 6 homolog-like (ORC6L), eukaryotic translation initiation factor 4E (EIF4E), thymidylate synthase (TS), SET and MYND domain containing 3 (SMYD3), Dickkopf homolog 4, and methyl-CpG binding domain protein 4 (MBD4). Forty-eight snap frozen clinical colorectal samples (24 normal and 24 paired colorectal cancer patient samples) were selected with detailed clinical follow-up information. cDNAs were synthesized and the expression levels of marker genes were quantified via qRT-PCR analysis. The statistical significance of these markers for disease prognosis was evaluated using the two-tailed paired Wilcoxon test. Survival curves were plotted according to the method of Kaplan-Meier and compared using the log-rank test. Based on the quantitative expression analysis, RRM2 (p=0.0001; 95% CI, 2.0-4.5), ORC6L (p=0.0001; 95% CI, 1.8-4.6), EIF4E (p=0.0002; 95% CI, 0.3-0.9), TS (p=0.0005; 95% CI, 0.7-2.2) and SMYD3 (p=0.0001; 95% CI, 0.8-1.5) were overexpressed in tumor tissues. However, the expression of SEI1 was decreased in tumors (p=0.02; 95% CI, 0.1-1.3), consistent with the function of SEI1 as a potential tumor suppressor. Kaplan-Meier survival analysis indicated that MBD4 is a significant prognostic factor for patient survival (p=0.03). MBD4 was a key protein involved in DNA methylation. The expression of TS was associated with tumor stage as it had a significantly higher expression level in UICC stage I and II compared to stage IV patients (p=0.03). MBD4 may be a potential novel prognostic marker for predicting patient survival for colorectal cancer.

Thymidylate synthase expression in primary colorectal tumours is correlated with its expression in metastases

Objective. Thymidylate synthase (TS) is the rate-limiting enzyme in the synthesis of pyrimidine nucleotides and as such a critical target for fluoropyrimidines, which are widely used in the treatment of colorectal cancer (CRC). The purpose of this study was to investigate TS expression in the primary tumours (PTs) and their metastases (M) in advanced CRC. Material and methods. TS expression was determined immunohistochemically in paraffin-embedded biopsies of PT-M pairs in 39 CRC patients, as related to the clinical data. Results. There was no difference in the mean TS index of PTs compared with that of M, 1.25 and 1.14, respectively (p=0.12). TS expression of PTs was above the mean more often than that of M (61.5% and 41.0%, respectively, p=0.035). High TS expression in PTs was significantly related to high expression in M (the Fisher exact test, p=0.001). Using the absolute index values, TS expression in PT and M was significantly correlated (Pearson R=0.501, p=0.001). In 29/39 (74.3%) pairs, PT and M had concordant expression levels (Cohen's kappa 0.508, 95% CI 0.260–0.756, p=0.001; intraclass correlation coefficient (ICC) = 0.679, 95% CI 0.358–0.836, p=0.0001). No significant association was found between TS expression and any of the clinicopathological variables, disease outcome (DFS, DSS) or its response to treatment in univariate or multivariate analysis. Conclusions. Albeit usually higher, TS expression in PT was closely correlated with TS expression in M. This suggests that measurement of TS in primary CRC accurately predicts TS expression in subsequent metastases, which may help in selecting those patients most likely to respond to 5-FU-based regimens.

5-fluorouracil related gene expression levels in primary colorectal cancer and corresponding liver metastases

3568 Background: The most commonly used chemotherapeutic drug for colorectal cancer (CRC) is 5-fluorouracil (5-FU). Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), orotate phosphoribosyl transpherase (OPRT) are involved in the metabolic pathway of 5-FU and have been shown in several studies to be associated with response to 5-FU-based therapies. Since liver metastases are the main cause of death for most of CRC patients, it is reasonable to expect that measurement of these gene expression levels in liver metastases would provide the best prediction of therapy benefit, but in most cases, only biopsies of the patient’s primary tumor are readily available for analysis. Our aim was to determine how TS, DPD, TP, and OPRT gene expression levels in primary CRC were related to those in liver metastases. Methods: Thirty-one pairs of primary CRC and corresponding liver metastases were analyzed. (18 males and 13 females: Median age 66 (range 45–85)). Formalin-fixed, paraffin-embedded tumor specimens were dissected by using laser-captured microdissection. RNA was extracted and cDNA was prepared by reverse-transcription. Quantitation of target gene and internal reference gene was performed using real-time PCR (Taqman PCR). Results: No significant difference was seen between median mRNA expression levels of TS, DPD, TP, and OPRT in primary cancer and those in corresponding liver metastases (Median value: TS 1.48 vs. 1.43; p=0.92, DPD 0.19 vs.0.12; p=0.10, TP 1.20 vs. 0.98; p=0.39, OPRT 1.17 vs. 0.95; p=0.10, Wilcoxon signed rank test). When matched tissue sets were compared on an individual basis, there was a significant correlation for TS mRNA expression between primary cancer and corresponding liver metastases (rs=0.52, p=0.0026, Spearman rank correlation coefficient). However, no correlation was seen between matched sets for DPD, TP, or OPRT. Significant correlation was seen between DPD and TP expression levels in both primary CRC (rs=0.38, p=0.03) and liver metastases (rs=0.72, p<0.0001). Conclusions: A good prediction of TS mRNA levels in liver metastases can be obtained by measuring those of primary CRC, although no correlation was seen for DPD, TP, and OPRT. No significant financial relationships to disclose.

Immunohistochemical determination of thymidylate synthase in colorectal cancer--methodological studies.

With the aid of specific monoclonal antibodies, an immunohistochemical technique has recently been developed for the detection of intratumoral thymidylate synthase (TS). This technique can be applied to paraffin-embedded material suitable for retrospective studies. In order to examine this technique further, the TS enzyme activity of lysates from frozen-stored colorectal cancer (CRC) specimens were compared with their immunohistochemical TS staining intensity (arbitrarily graded from 0 to 3). A statistically significant correlation between these two methods on a total of 25 tumour specimens (P < 0.001) was observed. The staining intensity in different areas of 48 paraffin-embedded CRCs was examined. Sixty-seven per cent of the tumours were homogeneously stained (either grades 0-1 or 2-3), 33% showed a heterogeneity in TS staining. Increased TS expression correlated with more advanced Dukes' stage (P < 0.001). It is concluded that TS immunostaining intensity reflects TS enzyme activity in colorectal tumours and is well suited for paraffin-embedded material. The TS immunostaining pattern is heterogeneous in up to one-third of the tumours.