Changes in the status of p53 affect drug sensitivity to thymidylate synthase (TS) inhibitors by altering TS levels

Resveratrol and p53: How are they involved in CRC plasticity and apoptosis?

BACKGROUND

Colorectal cancer (CRC), which is mainly caused by epigenetic and lifestyle factors, is very often associated with functional plasticity during its development. In addition, the malignant plasticity of CRC cells underscores one of their survival abilities to functionally adapt to specific stresses, including inflammation, that occur during carcinogenesis. This leads to the generation of various subsets of cancer cells with phenotypic diversity and promotes epithelial-mesenchymal transition (EMT), formation of cancer cell stem cells (CSCs) and metabolic reprogramming. This can enhance cancer cell differentiation and facilitate tumorigenic potential, drug resistance and metastasis.

AIM OF REVIEW

The tumor protein p53 acts as one of the central suppressors of carcinogenesis by regulating its target genes, whose proteins are involved in the plasticity of cancer cells, autophagy, cell cycle, apoptosis, DNA repair. The aim of this review is to summarize the latest published research on resveratrol's effect in the prevention of CRC, its regulatory actions, specifically on the p53 pathway, and its treatment options.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Resveratrol, a naturally occurring polyphenol, is a potent inducer of a variety of tumor-controlling. However, the underlying mechanisms linking the p53 signaling pathway to the functional anti-plasticity effect of resveratrol in CRC are still poorly understood. Therefore, this review discusses novel relationships between anti-cellular plasticity/heterogeneity, pro-apoptosis and modulation of tumor protein p53 signaling in CRC oncogenesis, as one of the crucial mechanisms by which resveratrol prevents malignant phenotypic changes leading to cell migration and drug resistance, thus improving the ongoing treatment of CRC.

Association of the TRIM family protein with survival outcomes and clinicopathological features in colorectal cancer: a systematic review and meta-analysis

BACKGROUND

The tripartite motif (TRIM) proteins have been reported to play crucial roles in various malignancies. However, the clinical significance of TRIM proteins in colorectal cancer (CRC) remains controversial. This study aimed to evaluate the association between TRIM proteins and the clinicopathological features and survival outcomes in patients with CRC.

METHODS

We performed a meta-analysis to investigate whether TRIM is a prognostic factor in CRC. PubMed, Embase, Web of Science, CNKI and Weipu databases were searched to identify eligible studies that evaluated the association between TRIM proteins and overall survival (OS), as well as the clinicopathological features of patients with CRC. Hazard ratios (HR) or odds ratios (OR) with 95% confidence interval (CI) were derived and pooled using a fixed-effects model.

RESULTS

From inception to March 2023, we extracted study characteristics and prognostic data for each identified study. Twelve studies enrolling 1608 patients were eligible for inclusion. Data on OS and recurrence-free survival (RFS) were available for 12 and 2 studies, respectively. The pooled analysis results showed a significant correlation between the elevated TRIM proteins and shorter OS (HR = 2.42, 95% CI: 1.96-2.99) and worse RFS (HR = 2.51, 95% CI: 1.78-3.54) in patients with CRC. The combined ORs indicated that TRIM protein over-expression was significantly associated with advanced TNM stage (OR = 2.26, 95% CI: 1.25-4.10), deep tumor invasion (OR = 2.01, 95% CI: 1.04-3.88), lymph node metastasis (OR = 2.99, 95% CI: 2.19-4.09) and perineural invasion (OR = 1.95, 95% CI: 1.18-3.23).

CONCLUSIONS

Our findings suggest that TRIM proteins can predict tumor progression and poor prognosis in CRC. Therefore, TRIM proteins may be promising therapeutic targets for patients with CRC.

Inhibition of Colon Cancer Cells Via Apoptosis Pathway by Ethanolic Extract of Andaliman (Zanthoxylum Acanthopodium Dc.) Fruits

Andaliman (Zanthoxylum acanthopodium DC.) is an exotic spice from North Sumatra (Indonesia) commonly added to enrich the flavor of Bataknese ethnic food because of its unique aroma and trigeminal sensation. Traditionally, it is also known to have health benefits in the gastrointestinal tract; however no studies have reported it. Therefore, this study aimed to investigate the potency of Andaliman fruit to inhibit the proliferation of HCT-116 and WiDr colon cancer cells and its underlying mechanism of inhibition. Andaliman fruits were extracted using ethanol. The anti-proliferative effect was evaluated using the MTT test, and the underlying mechanism of inhibition was examined using the Real-Time Polymerase Chain Reaction (RT-PCR) and Hoechst staining. Bax and Bcl-2 proteins were used as the markers for the pro-apoptotic and anti-apoptotic gene expression analysis, respectively. Andaliman ethanolic extract showed potential bioactivity to inhibit the growth of WiDr and HCT-116 cells in vitro with IC50 of 95.61 μg.mL-1 and 94.64 μg.mL-1, respectively. The cytotoxicity effect of andaliman was rationalized by the gene expression of Bax and Bcl-2 in a non-dose-dependent manner. In addition, Andaliman extract could increase the apoptotic gene marker expression in both cells at half of their IC50, i.e. 47.81 μg.mL-1 and 47.32 μg.mL-1 for WiDr and HCT-116 cells, respectively. This study demonstrated that Andaliman fruit could be potentially developed as a functional food ingredient to prevent colon cancer by inducing the apoptosis mechanism.

Role of pH in Regulating Cancer Pyrimidine Synthesis

Replication is a fundamental aspect of cancer, and replication is about reproducing all the elements and structures that form a cell. Among them are DNA, RNA, enzymes, and coenzymes. All the DNA is doubled during each S (synthesis) cell cycle phase. This means that six billion nucleic acids must be synthesized in each cycle. Tumor growth, proliferation, and mutations all depend on this synthesis. Cancer cells require a constant supply of nucleotides and other macromolecules. For this reason, they must stimulate de novo nucleotide synthesis to support nucleic acid provision. When deregulated, de novo nucleic acid synthesis is controlled by oncogenes and tumor suppressor genes that enable increased synthesis and cell proliferation. Furthermore, cell duplication must be achieved swiftly (in a few hours) and in the midst of a nutrient-depleted and hypoxic environment. This also means that the enzymes participating in nucleic acid synthesis must work efficiently. pH is a critical factor in enzymatic efficiency and speed. This review will show that the enzymatic machinery working in nucleic acid synthesis requires a pH on the alkaline side in most cases. This coincides with many other pro-tumoral factors, such as the glycolytic phenotype, benefiting from an increased intracellular pH. An increased intracellular pH is a perfect milieu for high de novo nucleic acid production through optimal enzymatic performance.

Gastric cancer with microsatellite instability displays increased thymidylate synthase expression

BACKGROUND

Gastric cancer (GC) with microsatellite instability (MSI) is a less aggressive disease and associated with resistance to 5-fluorouracil (5-FU)-based chemotherapy (CMT). Thymidylate synthase (TS) is inhibited by 5-FU, and another potential mediator of therapeutic resistance to 5-FU. Therefore, we aimed to analyze the association between MSI and TS expression in GC, and its impact on disease outcomes.

METHODS

We retrospectively evaluated GC who underwent D2-gastrectomy. MSI and TS were analyzed by immunohistochemistry. We also investigated p53 expression, PD-L1 status, and tumor-infiltrating lymphocytes (CD4 and CD8).

RESULTS

Out of 284 GC, 60 (21.1%) were MSI. Median TS-score for all cases was 16.5. TS expression was significantly higher in MSI compared to microsatellite-stable (MSS; p < 0.001). Considering both status, GC were classified in four groups: 167 (58.8%) MSS + TS-low; 57 (20.1%) MSS + TS-High; 24 (8.5%) MSI + TS-low; and 36 (12.7%) MSI + TS-high. MSI + TS-high group had less advanced pTNM stage, higher CD8+T cells levels (p < 0.001) and PD-L1 positivity (p < 0.001). Normal p53 expression was related to MSI GC (p < 0.001). Improved survival was observed in MSI + TS-high, but no survival benefit was seen with CMT.

CONCLUSION

MSI GC was associated with high TS levels, which may explain therapeutic resistance to 5-FU. Additionally, MSI + TS-high showed better survival, but without improvement with CMT.

Genetic polymorphisms and gene expression of one-carbon metabolizing enzymes and their relation to breast cancer

Background

Breast cancer is considered the leading cause of cancer-related death among Egyptian women (15.41%). One of the common BC risk factors is the genetic factor. One-carbon metabolism is one of the pathways reported to increase BC risk by influencing DNA synthesis and methylation. Methyl tetrahydrofolate reductase (MTHFR), thymidylate synthase (TYMS) and DNA methyltransferase (DNMT) enzymes are key enzymes in one-carbon metabolism directly and through influencing folate metabolism. We aimed to study the association of the gene expression level and polymorphisms of MTHER C677T (rs1801133), TYMS (rs45445694), TYMS 3′UTR 1494del6 and ΔDNMT3B − 149C>T with breast cancer risk in a sample of Egyptian women.

Methods

This study was conducted on one hundred female breast cancer patients. Genotyping and gene expression of the MTHFR and TYMS (1494del6, rs45445694) and DNMT3B genes were performed.

Results

There was no significant difference (OR 1.493; 95% CI 0.78–2.84; P = 0.288) in the frequency of the MTHFR (C677T) genotypes between breast cancer patients and control subjects and no significant difference in the frequency of the MTHFR mutant T allele. TYMS tandem repeats showed a significant difference (OR 2.232; CI 1.21–4.12; P = 0.01) in the frequency of the genotype 2R/3R among breast cancer patients and control subjects; however, the frequency of the 2R allele was not significantly different from that of the 3R allele (OR 1.461; 95% CI 0.96–2.21; P = 0.073). TYMS 3′-UTR 1494del6 showed a significant difference in the distribution of (+ 6/ + 6), (+ 6/− 6) and (− 6/− 6) genotypes between the patient and control groups (P ≤ 0.001*), and its corresponding mutant allele showed P value ≤ 0.001, 95% CI = 1.64–3.76 and OR = 2.483. The expression of MTHFR was downregulated by 0.62-fold in all malignant tissues compared to normal adjacent tissues (0.57 ± 0.20, P < 0.001*). On the other hand, no significant difference (P = 0.143) in the expression level of TYMS was found. Gene expression of DNMT3B was upregulated by 1.65-fold in all breast cancerous tissue samples compared with the control normal adjacent tissue with mean ± SD of 1.81 ± 0.63. (P ≤ 0.001*).

Conclusion

The current study showed that the 2R/3R TYMS allele and DNMT3B (− 149C>T) SNP are associated with a high risk of breast cancer and that there is a correlation between the 3′-UTR 1494del6 polymorphism (genotype − 6/− 6) and breast cancer risk. A significant reduction was found in the MTHFR gene expression level in BC compared with control tissues, and the DNMT3B (− 149C>T) SNP did affect the DNMT3B expression level.

Regulations of expressions of rat/human sulfotransferases by anticancer drug, nolatrexed, and micronutrients

Cancer is related to the cellular proliferative state. Increase in cell-cycle regulatory function augments cellular folate pool. This pathway is therapeutically targeted. A number of drugs influences this metabolism, that is, folic acid, folinic acid, nolatrexed, and methotrexate. Our previous study showed methotrexate influences on rat/human sulfotransferases. Present study explains the effect of nolatrexed (widely used in different cancers) and some micronutrients on the expressions of rat/human sulfotransferases. Female Sprague-Dawley rats were treated with nolatrexed (01-100 mg/kg) and rats of both sexes were treated to folic acid (100, 200, or 400 mg/kg) for 2-weeks and their aryl sulfotransferase-IV (AST-IV; β-napthol sulfation) and sulfotransferase (STa; DHEA sulfation) activities, protein expression (western blot) and mRNA expression (RT-PCR) were tested. In human-cultured hepatocarcinoma (HepG2) cells nolatrexed (1 nM-1.2 mM) or folinic acid (10 nM-10 μM) were applied for 10 days. Folic acid (0-10 μM) was treated to HepG2 cells. PPST (phenol catalyzing), MPST (dopamine and monoamine), DHEAST (dehydroepiandrosterone and DHEA), and EST (estradiol sulfating) protein expressions (western-blot) were tested in HepG2 cells. Present results suggest that nolatrexed significantly increased sulfotransferases expressions in rat (protein, STa, F = 4.87, P < 0.05/mRNA, AST-IV, F = 6.702, P < 0.014; Student's t test, P < 0.01-0.05) and HepG2 cells. Folic acid increased sulfotransferases activity/protein in gender-dependant manner. Both folic and folinic acid increased several human sulfotransferases isoforms with varied level of significance (least or no increase at highest dose) in HepG2 cells pointing its dose-dependent multiphasic responses. The clinical importance of this study may be furthered in the verification of sulfation metabolism of several exogenous/endogenous molecules, drug-drug interaction and their influences on cancer pathophysiological processes. Further studies are necessary.

TRIM Proteins in Colorectal Cancer: TRIM8 as a Promising Therapeutic Target in Chemo Resistance

Colorectal cancer (CRC) represents one of the most widespread forms of cancer in the population and, as all malignant tumors, often develops resistance to chemotherapies with consequent tumor growth and spreading leading to the patient’s premature death. For this reason, a great challenge is to identify new therapeutic targets, able to restore the drugs sensitivity of cancer cells. In this review, we discuss the role of TRIpartite Motifs (TRIM) proteins in cancers and in CRC chemoresistance, focusing on the tumor-suppressor role of TRIM8 protein in the reactivation of the CRC cells sensitivity to drugs currently used in the clinical practice. Since the restoration of TRIM8 protein levels in CRC cells recovers chemotherapy response, it may represent a new promising therapeutic target in the treatment of CRC.

p53 expression confers sensitivity to 5-fluorouracil via distinct chromatin accessibility dynamics in human colorectal cancer

One of the most commonly used drugs in chemotherapy, 5-fluorouracil (5-FU) has been shown to be effective in only 10-15% of patients with colon cancer. Thus, studies of the mechanisms affecting 5-FU sensitivity in these patients are necessary. The tumor suppressor protein p53 is a transcription factor that serves important roles in cell apoptosis by regulating the cell cycle. It has also been characterized as a key factor influencing drug sensitivity. Furthermore, accessible chromatin is a hallmark of active DNA regulatory elements and functions as a crucial epigenetic factor regulating cancer mechanisms. The present study assessed the genetic regulatory landscape in colon cancer by performing RNA sequencing and Assay for Transposase-Accessible Chromatin sequencing, and investigated the effects of 5-FU on chromatin accessibility and gene expression. Notably, while treatment with 5-FU mediated global increases in chromatin accessibility, chromatin organization in several genomic regions differed depending on the expression status of p53. Since the occupancy of p53 does not overlap with accessible chromatin regions, the 5-FU-mediated changes in chromatin accessibility were not regulated by direct binding of p53. In the p53-expressing condition, the 5-FU-mediated accessible chromatin region was primarily associated with genes encoding cell death pathways. Additionally, 5-FU was revealed to induce open chromatin conformation at regions containing binding motifs for AP-1 family transcription factors, which may drive expression of apoptosis pathway genes. In conclusion, expression of p53 may confer 5-FU sensitivity by regulating chromatin accessibility of distinct genes associated with cell apoptosis in a transcription-independent manner.

Plasma thymidylate synthase and dihydrofolate reductase mRNA levels as potential predictive biomarkers of pemetrexed sensitivity in patients with advanced non-small cell lung cancer

Background

High levels of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) expression in tumour tissues are an indicator of ineffective responses to pemetrexed-based chemotherapy in various tumours, including non-small cell lung cancer (NSCLC). However, tumour tissues are highly heterogeneous, so a single biopsy may not reflect genetic alterations during disease progression. This study investigated the potential use of plasma TS and DHFR mRNA levels as biomarkers for predicting sensitivity to pemetrexed-based chemotherapy.

Methods

Plasma samples were obtained from 245 patients with advanced NSCLC and 30 healthy donors. Total RNA was extracted from the plasma samples, and TS and DHFR mRNA levels were determined via real-time PCR. TS and DHFR mRNA levels between cancer patients and healthy controls were compared. The association between plasma TS and DHFR mRNA levels and tumour response to pemetrexed/cisplatin chemotherapy was analysed.

Results

The plasma TS and DHFR mRNA levels decreased in patients with advanced NSCLC compared with healthy controls. Moreover, plasma TS and DHFR mRNA levels negatively correlated with tumour response to pemetrexed/cisplatin chemotherapy in patients with advanced NSCLC. Overall survival time was prolonged in patients with low TS mRNA expression compared with those with high TS mRNA expression, although the difference was not statistically significant.

Conclusions

Low expression levels of plasma TS and DHFR mRNA confer increased tumour sensitivity to pemetrexed/cisplatin chemotherapy in patients with advanced NSCLC. The results suggested that plasma TS and DHFR mRNA levels are promising biomarkers for choosing patients who are likely to respond and benefit the most from pemetrexed-based chemotherapy.

High-grade serous peritoneal cancer follows a high stromal response signature and shows worse outcome than ovarian cancer

In the era of personalized medicine, where transition from organ‐based to individualized genetic diagnosis takes place, the tailoring of treatment in cancer becomes increasingly important. This is particularly true for high‐grade, advanced FIGO stage serous adenocarcinomas of the ovary (OC), fallopian tube (TC), and peritoneum (PC), which are currently all treated identically. We analyzed three independent patient cohorts using histopathologically classified diagnosis and various molecular approaches (transcriptomics, immunohistochemistry, next‐generation sequencing, fluorescent and chromogenic in situ hybridization). Using multivariate Cox regression model, we found that PC is more aggressive compared with advanced‐stage OC independent of residual disease as shown by an earlier relapse‐free survival in two large cohorts (HR: 2.63, CI: 1.59–4.37, P < 0.001, and HR: 1.66, CI: 1.04–2.63, P < 0.033). In line with these findings, transcriptomic data revealed differentially expressed gene signatures identifying PC as high stromal response tumors. The third independent cohort (n = 4054) showed a distinction between these cancer types for markers suggested to be predictive for chemotherapy drug response. Our findings add additional evidence that ovarian and peritoneal cancers are epidemiologically and molecularly distinct diseases. Moreover, our data also suggest consideration of the tumor‐sampling site for future diagnosis and treatment decisions.

A Peptidic Thymidylate-Synthase Inhibitor Loaded on Pegylated Liposomes Enhances the Antitumour Effect of Chemotherapy Drugs in Human Ovarian Cancer Cells

There is currently no effective long-term treatment for ovarian cancer (OC) resistant to poly-chemotherapy regimens based on platinum drugs. Preclinical and clinical studies have demonstrated a strong association between development of Pt-drug resistance and increased thymidylate synthase (hTS) expression, and the consequent cross-resistance to the hTS inhibitors 5-fluorouracil (5-FU) and raltitrexed (RTX). In the present work, we propose a new tool to combat drug resistance. We propose to treat OC cell lines, both Pt-sensitive and -resistant, with dual combinations of one of the four chemotherapeutic agents that are widely used in the clinic, and the new peptide, hTS inhibitor, [D-Gln⁴]LR. This binds hTS allosterically and, unlike classical inhibitors that bind at the catalytic pocket, causes cell growth inhibition without inducing hTS overexpression. The dual drug combinations showed schedule-dependent synergistic antiproliferative and apoptotic effects. We observed that the simultaneous treatment or 24h pre-treatment of OC cells with the peptide followed by either agent produced synergistic effects even in resistant cells. Similar synergistic or antagonistic effects were obtained by delivering the peptide into OC cells either by means of a commercial delivery system (SAINT-PhD) or by pH sensitive PEGylated liposomes. Relative to non-PEGylated liposomes, the latter had been previously characterized and found to allow macrophage escape, thus increasing their chance to reach the tumour tissue. The transition from the SAINT-PhD delivery system to the engineered liposomes represents an advancement towards a more drug-like delivery system and a further step towards the use of peptides for in vivo studies. Overall, the results suggest that the association of standard drugs, such as cDDP and/or 5-FU and/or RTX, with the novel peptidic TS inhibitor encapsulated into PEGylated pH-sensitive liposomes can represent a promising strategy for fighting resistance to cDDP and anti-hTS drugs.

p53 Disruption Increases Uracil Accumulation in DNA of Murine Embryonic Fibroblasts and Leads to Folic Acid-Nonresponsive Neural Tube Defects in Mice

BACKGROUND

Neural tube defects (NTDs) occur in nervous tissue during embryogenesis when the neural tube fails to close. Approximately 70% of all human NTDs can be prevented by folic acid (FA). Altered expression and/or function of the tumor suppressor protein p53 can lead to NTDs in mouse models.

OBJECTIVES

The aim of this study was to determine if dietary FA could rescue p53-/--induced NTDs in mice, and to determine the effect loss of p53 has on pathways in folate 1-carbon metabolism.

METHODS

p53+/- female mice were randomly allocated and weaned onto either an FA-sufficient diet (2 mg/kg folic acid; +FA), or an FA-deficient diet (-FA). After 8 wk, the females were time-mated to p53-/- males. Embryos were examined at E12.5 for NTDs. Folate enzyme concentrations, nucleotide synthesis, uracil accumulation in DNA, and proliferation were measured in primary murine embryonic fibroblasts (MEFs). The "n - 1" chi-square test was used to compare NTD percentages, whereas all other data were analyzed by Student t test, except where noted a multilevel-fit model was used.

RESULTS

NTD rates of litters from dams consuming the +FA diet (20/46; 43%) did not differ from those of litters from dams consuming the -FA diet (14/35; 40%) (P > 0.05). p53-/- MEFs had 55% higher rates of folate-dependent de novo dTMP synthesis, a ∼2-fold higher accumulation of uracil in DNA, and a ∼30% higher rate of proliferation (P ≤ 0.05) than p53+/- MEFs independent of folate.

CONCLUSIONS

p53-related NTDs are not FA responsive. Increased dTMP synthesis in p53-/- MEFs might not have been sufficient to meet the demands for thymidine triphosphate (dTTP) synthesis as evidenced by the elevated amounts of uracil in DNA. This study provides additional evidence that elevated uracil in DNA is a risk factor for NTDs.

5-fluorouracil and other fluoropyrimidines in colorectal cancer: Past, present and future

5-Fluorouracil (5-FU) is an essential component of systemic chemotherapy for colorectal cancer (CRC) in the palliative and adjuvant settings. Over the past four decades, several modulation strategies including the implementation of 5-FU-based combination regimens and 5-FU pro-drugs have been developed and tested to increase the anti-tumor activity of 5-FU and to overcome the clinical resistance. Despite the encouraging progress in CRC therapy to date, the patients' response rates to therapy continue to remain low and the patients' benefit from 5-FU-based therapy is frequently compromised by the development of chemoresistance. Inter-individual differences in the treatment response in CRC patients may originate in the unique genetic and epigenetic make-up of each individual. The critical element in the current trend of personalized medicine is the proper comprehension of causes and mechanisms contributing to the low or lack of sensitivity of tumor tissue to 5-FU-based therapy. The identification and validation of predictive biomarkers for existing 5-FU-based and new targeted therapies for CRC treatment will likely improve patients' outcomes in the future. Herein we present a comprehensive review summarizing options of CRC treatment and the mechanisms of 5-FU action at the molecular level, including both anabolic and catabolic ways. The main part of this review comprises the currently known molecular mechanisms underlying the chemoresistance in CRC patients. We also focus on various 5-FU pro-drugs developed to increase the amount of circulating 5-FU and to limit toxicity. Finally, we propose future directions of personalized CRC therapy according to the latest published evidence.

MYC predetermines the sensitivity of gastrointestinal cancer to antifolate drugs through regulating TYMS transcription

Background

Thymidylate synthase (TYMS) is a successful chemotherapeutic target for anticancer therapy. Numerous TYMS inhibitors have been developed and used for treating gastrointestinal cancer now, but they have limited clinical benefits due to the prevalent unresponsiveness and toxicity. It is urgent to identify a predictive biomarker to guide the precise clinical use of TYMS inhibitors.

Methods

Genome-scale CRISPR-Cas9 knockout screening was performed to identify potential therapeutic targets for treating gastrointestinal tumours as well as key regulators of raltitrexed (RTX) sensitivity. Cell-based functional assays were used to investigate how MYC regulates TYMS transcription. Cancer patient data were used to verify the correlation between drug response and MYC and/or TYMS mRNA levels. Finally, the role of NIPBL inactivation in gastrointestinal cancer was evaluated in vitro and in vivo.

Findings

TYMS is essential for maintaining the viability of gastrointestinal cancer cells, and is selectively inhibited by RTX. Mechanistically, MYC presets gastrointestinal cancer sensitivity to RTX through upregulating TYMS transcription, supported by TCGA data showing that complete response cases to TYMS inhibitors had significantly higher MYC and TYMS mRNA levels than those of progressive diseases. NIPBL inactivation decreases the therapeutic responses of gastrointestinal cancer to RTX through blocking MYC.

Interpretation

Our study unveils a mechanism of how TYMS is transcriptionally regulated by MYC, and provides rationales for the precise use of TYMS inhibitors in the clinic.

Funding

This work was financially supported by grants of NKRDP (2016YFC1302400), STCSM (16JC1406200), NSFC (81872890, 81322034, 81372346) and CAS (QYZDB-SSW-SMC034, XDA12020210).

Coexisting Molecular Determinants of Acquired Oxaliplatin Resistance in Human Colorectal and Ovarian Cancer Cell Lines

Oxaliplatin (OHP) treatment of colorectal cancer (CRC) frequently leads to resistance. OHP resistance was induced in CRC cell lines LoVo-92 and LoVo-Li and a platinum-sensitive ovarian cancer cell line, A2780, and related to cellular platinum accumulation, platinum-DNA adducts, transporter expression, DNA repair genes, gene expression arrays, and array-CGH profiling. Pulse (4 h, 4OHP) and continuous exposure (72 h, cOHP) resulted in 4.0 to 7.9-fold and 5.0 to 11.8-fold drug resistance, respectively. Cellular oxaliplatin accumulation and DNA-adduct formation were decreased and related to OCT1-3 and ATP7A expression. Gene expression profiling and pathway analysis showed significantly altered p53 signaling, xenobiotic metabolism, role of BRCA1 in DNA damage response, and aryl hydrocarbon receptor signaling pathways, were related to decreased ALDH1L2, Bax, and BBC3 (PUMA) and increased aldo-keto reductases C1 and C3. The array-CGH profiles showed focal aberrations. In conclusion, OHP resistance was correlated with total platinum accumulation and OCT1-3 expression, decreased proapoptotic, and increased anti-apoptosis and homologous repair genes.

AMPK activation induced in pemetrexed-treated cells is associated with development of drug resistance independently of target enzyme expression

Pemetrexed (PEM) inhibits DNA and RNA synthesis and is currently one of the first‐line agents for mesothelioma. PEM suppresses the activities of several enzymes involved in purine and pyrimidine synthesis, and elevated activity of these enzymes in tumors is often linked with resistance to PEM. The agent also stimulates AMP‐activated protein kinase (AMPK) and consequently influences the mammalian target of rapamycin complex 1 (mTORC1) pathways. Nevertheless, it remains unclear whether PEM resistance is linked to the AMPK or mTORC1 pathways. Here, we established two independent PEM‐resistant mesothelioma cell lines in which expression of the PEM‐target enzymes was not elevated, and found that levels of phosphorylated AMPK and p70S6K and, to a lesser extent, levels of phosphorylated AKT and p53, were increased in these cells as compared with the respective parent cells. PEM stimulation also augmented phosphorylation of AMPK, p70S6K, AKT and p53 in most cases. An AMPK activator increased phosphorylation and PEM resistance in parental cells, and the inhibitor decreased the resistance of PEM‐resistant cells. In contrast, inhibitors for p70S6K and AKT did not influence PEM resistance; furthermore, increased levels of endogenous p53 did not affect PEM sensitivity. These data collectively indicate that constitutive activation of AMPK is associated with PEM resistance, and that this is unconnected with elevated DNA and RNA synthesis.

Design, synthesis and biological evaluation of N-phenyl-(2,4-dihydroxypyrimidine-5-sulfonamido)benzoyl hydrazide derivatives as thymidylate synthase (TS) inhibitors and as potential antitumor drugs

The Inhibition of cellular nucleotide metabolism to promote apoptosis is a key principle of cancer therapy. Thymidylate synthase (TS) is a key rate-limiting enzyme in the initiation of DNA synthesis in cell. Here, we presented two types of thymidylate synthase inhibitors, and, the key pharmacological properties of these two types of thymidylate synthase inhibitor were extracted and combined to design new compounds with inhibitory activity. Therefore, two series of 42 new compounds with the common biological effect of promoting apoptosis are designed and synthesized by combination principle. Most of the compounds had good anti-proliferative activity on A549, OVCAR-3, SGC7901 and MDA-MB-231 cells. The IC₅₀ of compound 10l on A549 cells was 1.26 μM, which was better than that of pemetrexed (PTX, IC₅₀ = 3.31 μM), furthermore, the selection index of compound 10l was higher than PTX. Flow cytometry analysis showed that compound 10l (the apoptosis rate is 39.4%) could induce A549 cell apoptosis and effectively inhibit tumor cell proliferation. Further western blot analysis showed that compound 10l could induce intrinsic apoptosis by activating caspase-3, increasing expression of cleaved caspase-3 and reducing the ratio of bcl-2/bax. All of this makes compound 10l to be a promising compound in future animal tumor models.

Curcumin Analog Pentagamavunon-1 (PGV-1) Sensitizes Widr Cells to 5-Fluorouracil through Inhibition of NF-κB Activation

Cell cycle regulation and the NF-κB pathway in cancer cells are important in mediating resistance to 5-Fluorouracil (5-FU). Pentagamavunon-1 (PGV-1), a curcumin analog, is known to exhibit stronger growth inhibitory effects than curcumin itself in several cancer cells. In this study, we evaluated the potency of PGV-1 in combination with 5-FU in WiDr colon cancer cells. In MTT assays, PGV-1 did not only exhibit stronger growth inhibitory effects than both 5-FU and curcumin, but also enhanced the cytotoxicity of 5-FU. Flow cytometry demonstrated that single treatments with PGV-1 and 5-FU resulted in different effects on cell cycle profiles. PGV-1 induced G2/M arrest while 5-FU caused S-phase arrest at low concentration (1 μM) and G1-phase arrest at high concentration (100 μM). Interestingly, the combination of 5-FU and PGV-1 enhanced cell accumulation in S-phase. Although a single treatment with either 5-FU or PGV-1 increased cyclin D1 at the protein level, the combination treatment resulted in significant suppression. In addition, PGV-1 inhibited activation of NF-κB and suppressed the expression of cyclooxygenase-2, an NF-κB downstream protein. In conclusion, PGV-1 increased the cytotoxic effect of 5-FU on WiDr cells through inhibition of NF-κB activation.

High pemetrexed sensitivity of docetaxel-resistant A549 cells is mediated by TP53 status and downregulated thymidylate synthase

The chemoresistance of non-small cell lung cancer (NSCLC) that occurs in docetaxel (DOC) chemotherapy substantially decreases the survival of patients. To overcome DOC-induced chemoresistance, we established DOC-selected A549 lung cancer sublines (A549/D16 and A549/D32) and revealed that both sublines were cross-resistant to vincristine (VCR) and doxorubicin (DXR). Notably, both sublines were more sensitive to pemetrexed (PEM) than parental cells according to MTT and clonogenic assays. The expression levels of thymidylate synthase (TS) and γ-glutamyl hydrolase (GGH) were downregulated in DOC-resistant sublines. When exogenous TS was overexpressed in A549/D16 cells, PEM sensitivity was significantly decreased, however it was not decreased by overexpression of exogenous GGH. PEM treatment induced more apoptotic sub-G1 cells in both DOC-resistant sublines and in the in vivo PEM sensitivities of A549/D16 cells. These findings were further confirmed by a xenografted tumor model. To unmask the mediator of TS downregulation, we investigated human lung cancer cell lines that have various TP53 statuses using DOC treatment. The level of TS protein was significantly decreased in wild-type TP53-containing cells with DOC treatment; TS expression levels were not affected in mutant-TP53 and TP53-null cells under the same conditions. Furthermore, when the expression of TP53 was inhibited in A549 cells, the expression level of TS was increased. Our data indicated that DOC activated wild-type TP53 and suppressed TS expression under continuous DOC exposure. Therefore, the expression of TS remained at low levels in DOC-resistant A549 cancer cells. Our data revealed that for lung cancer with DOC resistance and wild-type TP53 status, the administration of PEM as a second-line agent to overcome DOC-resistance may benefit patients.

Raltitrexed Inhibits HepG2 Cell Proliferation via G0/G1 Cell Cycle Arrest

Raltitrexed (RTX) is an antimetabolite drug used as a chemotherapeutic agent for treating colorectal cancer, malignant mesothelioma, and gastric cancer. The antitumor capacity of RTX is attributed to its inhibitory activity on thymidylate synthase (TS), a key enzyme in the synthesis of DNA precursors. The current study is aimed at investigating the potential antitumor effects of RTX in liver cancer. Using the HepG2 cell line as an in vitro model of liver cancer, we evaluated the effects of RTX on cell proliferation employing both a WST-8 assay and a clone formation efficiency assay. In addition, we monitored the ultrastructure changes of HepG2 cells in response to RTX with transmission electric microscopy. To investigate the mechanism underlying the regulation of cell proliferation by RTX, we analyzed cell cycle using cell flow cytometry. Moreover, real-time PCR and Western blot analyses were conducted to examine expression levels of cell cycle regulatory proteins cyclin A and cyclin-dependent kinase 2 (CDK2), as well as their mediators tumor suppressor genes p53 and p16. Our results demonstrate that RTX inhibits HepG2 proliferation by arresting the cell cycle at G₀/G₁. This cell cycle arrest function was mediated via downregulation of cyclin A and CDK2. The observed elevated expression of p53 and p16 by RTX may contribute to the reduction of cyclin A/CDK2. Our study indicates that RTX could serve as a potential chemotherapeutic agent in the treatment of hepatocellular carcinoma.

TS mRNA levels can predict pemetrexed and raltitrexed sensitivity in colorectal cancer

PURPOSE

The purpose of the study is to analyze the relationship between tumor thymidylate synthase (TS) mRNA expression levels and raltitrexed/pemetrexed/5-FU sensitivity.

PATIENTS AND METHODS

We collected freshly removed colorectal tumor specimens from 50 patients. Chemosensitivities to anticancer drugs were evaluated by histoculture drug response assay. We adopted quantitative reverse transcription polymerase chain reaction for TS mRNA detection and immunohistochemical staining for assessing TS expression in tumor tissues.

RESULTS

There is a significant relationship between TS mRNA expression levels and in vitro chemosensitivity of freshly removed colorectal tumor specimens to pemetrexed (P < 0.001)/raltitrexed (P = 0.004)/5-FU (P = 0.007).

CONCLUSIONS

TS mRNA expression levels can predict pemetrexed and raltitrexed sensitivity in colorectal cancer.

¹⁸F-FDG uptake on PET is a predictive marker of thymidylate synthase expression in patients with thoracic neoplasms

The aim of this study was to investigate the relationship between the expression levels of thymidylate synthase (TS) and 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) uptake on positron emission tomography (PET) in various thoracic neoplasms. In total, 392 patients [non-small cell lung cancer (NSCLC) (n=140), malignant pleural mesothelioma (MPM) (n=21), pulmonary metastatic tumors (PMT) (n=148), thymic epithelial tumors (n=49) and pulmonary neuroendocrine (NE) tumor (n=34)] who underwent ¹⁸F-FDG PET before treatment were included in this study. Tumor sections were stained using immunohistochemistry for determination of TS, orotate phosphoribosyltransferase (OPRT), dihydropyrimidine dehydrogenase (DPD), vascular endothelial growth factor (VEGF), microvessel density (MVD), CD34 and p53. The expression of TS in thoracic neoplasms had a positivity of 58% (230/392), and the positive rates of TS expression in NSCLC, PMT, thymic epithelial tumor, NE tumor and MPM samples were 56, 57, 57, 85 and 47%, respectively. The positivity of TS expression was significantly higher in NE tumors compared to that in other thoracic tumors. A statistically significant correlation between TS expression and ¹⁸F-FDG uptake was observed in thoracic neoplasms, in particular primary lung adenocarcinomas, high-grade NE tumors, thymomas and MPMs. Moreover, TS expression was closely associated with angiogenesis, DPD, OPRT and p53. Our results indicated that SUV(max) by ¹⁸F-FDG uptake may be an alternative biomarker for predicting TS expression in patients with primary lung adenocarcinoma, high-grade NE tumor, thymoma and MPM.

Polymorphisms of folate metabolism-related genes and survival of patients with colorectal cancer in the Korean population

BACKGROUND

5-Fluorouracil (5-FU) is a cornerstone of chemotherapy for colorectal cancer (CRC), and the major targets of 5-FU are thymidylate synthase (TS), methylenetetrahydrofolate reductase (MTHFR), and reduced folate carrier 1 (RFC1). We hypothesized that polymorphisms in the genes encoding these proteins would be associated with CRC patient survival.

PATIENTS AND METHODS

We genotyped the following polymorphisms in 372 CRC patients: TS enhancer region (TSER), TS 1494del6, MTHFR 677C>T and 1298A>C, and RFC1 -43T>C, 80G>A, and 696C>T. Using Kaplan-Meier curves, log-rank tests, and Cox proportional hazard models, we evaluated associations between these polymorphisms and overall survival (OS).

RESULTS

The combined TS 1494 0bp6bp+6bp6bp genotype was associated with reduced OS compared to the TS 1494 0bp0bp genotype. Among rectal cancer patients, the RFC1 -43CC and 80AA genotypes were associated with favorable OS.

CONCLUSIONS

Our data suggest that TS and RFC1 polymorphisms are associated with CRC prognosis in Korean patients. Further studies are needed to verify these findings.

Thymidylate synthase and folyl-polyglutamate synthase are not clinically useful markers of response to pemetrexed in patients with malignant pleural mesothelioma

PURPOSE

Thymidylate synthase (TS) is a potential predictor of outcome after pemetrexed (Pem) in patients with malignant pleural mesothelioma (MPM), and assays measuring TS levels are commercially marketed. The goal of this study was to further evaluate the value of TS and to study another potential biomarker of response, the enzyme, folyl-polyglutamate synthase (FPGS), which activates Pem intracellularly.

METHODS

Levels of TS and FPGS were semi-quantitatively determined immunohistochemically using H-scores on tissue samples from 85 MPM patients receiving Pem as primary therapy. H-score was correlated with radiographic disease control rate (DCR), time to progression (TTP) and overall survival (OS). In addition, expression levels of TS and FPGS in MPM cell lines were determined using immunoblotting and correlated with their sensitivity to Pem-induced cell death.

RESULTS

H-scores from patients with disease control versus progressive disease showed extensive overlap. There were no significant correlations of DCR, TTP, or OS to either TS levels (p = 0.73, 0.93, and 0.59, respectively), FPGS levels (p = 0.95, 0.77, and 0.43, respectively) or the ratio of FPGS/TS using the median scores of each test as cutoffs. There was no correlation between TS or FPGS expression and chemosensitivity of mesothelioma cells to Pem in vitro.

CONCLUSIONS

Although previous retrospective data suggest that TS and FPGS expression might be potential markers of Pem efficacy in MPM, our data indicate these markers lack sufficient predictive value in individual patients and should not be used to guide therapeutic decisions in the absence of prospective studies.

Interferon-β produces synergistic combinatory anti-tumor effects with cisplatin or pemetrexed on mesothelioma cells

Interferons (IFNs) have been tested for the therapeutic effects in various types of malignancy, but mechanisms of the anti-tumors effects and the differential biological activities among IFN members are dependent on respective cell types. In this study, we examined growth inhibitory activities of type I and III IFNs on 5 kinds of human mesothelioma cells bearing wild-type p53 gene, and showed that type I IFNs but not type III IFNs decreased the cell viabilities. Moreover, growth inhibitory activities and up-regulated expression levels of the major histocompatibility complexes class I antigens were greater with IFN-β than with IFN-α treatments. Cell cycle analyses demonstrated that type I IFNs increased S- and G2/M-phase populations, and subsequently sub-G1-phase fractions. The cell cycle changes were also greater with IFN-β than IFN-α treatments, and these data collectively showed that IFN-β had stronger biological activities than IFN-α in mesothelioma. Type I IFNs-treated cells increased p53 expression and the phosphorylation levels, and activated apoptotic pathways. A combinatory use of IFN-β and cisplatin or pemetrexed, both of which are the current first-line chemotherapeutic agents for mesothelioma, produced synergistic anti-tumor effects, which were also evidenced by increased sub-G1-phase fractions. These data demonstrated firstly to our knowledge that IFN-β produced synergistic anti-tumor effects with cisplatin or pemetrexed on mesothelioma through up-regulated p53 expression.

S-adenosyl methionine specifically protects the anticancer effect of 5-FU via DNMTs expression in human A549 lung cancer cells

Cellular methylation is associated with stabilization of the chromatin structure. S-adenosyl methionine (SAM), a metabolite of methionine metabolism, is the methyl donor of essential cellular methyltransferase reactions. Using 3-(4,5-dimethylthiazol-2-yl)-2,5-dephenyl tetrazolium bromide (MTT) assay, we found that combination treatment of SAM and 5-fluorouracil (5-FU) specifically protected the anticancer effect of 5-FU, whereas the combination of SAM and cisplatin had no effect. This result was confirmed by FACS analysis. The combination treatment of SAM and 5-FU significantly decreased the dead cell population, while the G1 cell population was slightly increased, suggesting that protection of SAM is not associated with the cell cycle arrest of DNA-damaging drugs. We also analyzed which cellular methylation-related proteins were involved in the protective effect. Results showed the expression of DNA methyltransferases (DNMTs) was decreased with 5-FU alone but was increased with the combination treatment of SAM and 5-FU, suggesting that SAM protects the anticancer effect of 5-FU by regulating the expression of DNMTs. Taken together, the results indicated that SAM specifically modulates the anti-cancer effect of the DNA damage agent 5-FU and this may be modulated by aberrant DNA methylation.

Correlation between thymidylate synthase gene polymorphisms and efficacy of pemetrexed in advanced non-small cell lung cancer

One of the target genes of pemetrexed (PEM), thymidylate synthase (TS), has been shown to have a close association with its efficacy. TS gene polymorphisms have been shown to be associated with the efficacy of antifolate treatment in enteron tumors. The purpose of this study was to investigate the clinical significance of TS gene polymorphisms in patients with advanced NSCLC receiving PEM-based treatment. The variable nucleoid tandem repeat in the 5′-UTR region was amplified and detected using fluorescently labeled multiplex short tandem repeat polymerase chain reaction. The polymorphism in the 3′-UTR region of the TS gene was detected using the Taqman probe. Efficacy of PEM was assessed according to the Response Evaluation Criteria in Solid Tumors, version 1.1. None of the genotypes were associated with gender, smoking status and age. Disease control rate (DCR), objective response rate (ORR) and progression-free survival (PFS) were similar between patients harboring 2R and 3R alleles (PFS, p=0.518; DCR, p=0.631; ORR, p=0.541), as well as those with a 6-bp insertion and 6-bp deletion (PFS, p=0.776; DCR, p=0.626; ORR, p=0.330). To study the combined effect of TS polymorphisms, the study population was divided into three groups: 2R&6 del, 2R&6 ins and 3R&6 del. No significant differences were observed among the different groups according to DCR (p=0.517), ORR (p=0.611) and PFS (p=0.938). In conclusion, polymorphisms of the TS gene do not appear to be a prognostic marker for advanced NSCLC patients receiving PEM-based treatment.

Thymidylate synthase mRNA levels in plasma and tumor as potential predictive biomarkers for raltitrexed sensitivity in gastric cancer

Different chemotherapeutic agents currently available are effective only in certain subsets of patients. Predictive biomarkers will be helpful in choosing those agents and can improve the clinical efficiency by a more personalized chemotherapeutic approach. Raltitrexed is a novel water-soluble quinazoline folate analogue and can improve the efficiency of gastric cancer treatment, but its predictive biomarker remains unclear. The aim of our study was to investigate the role of plasma and tumor thymidylate synthase (TS) mRNA levels as predictive biomarkers for raltitrexed in gastric cancer. In total, 125 freshly removed gastric tumor specimens and corresponding blood samples before surgery were collected. Raltitrexed sensitivity was determined by histoculture drug response assay procedures. TS mRNA levels in tumor and plasma were determined by quantitative reverse transcription polymerase chain reaction. Plasma TS mRNA level in cancer patients was significantly higher than in healthy subjects (p = 0.009) and was significantly correlated with TS mRNA level in tumor tissues (r = 0.665, p < 0.001). Tumor and plasma TS mRNA expression levels were significantly lower in raltitrexed-sensitive group than in resistant group (p = 0.007 and 0.013, respectively). The sensitivity and accuracy of raltitrexed sensitivity prediction based on plasma TS mRNA levels were 82 and 60%, respectively, whereas the prediction based on tumor TS mRNA reached 70% sensitivity and 68% accuracy. These results indicate that TS mRNA level in plasma can mirror tumor TS mRNA level, and both of them can be used to predict raltitrexed sensitivity in gastric cancer.

Upregulated p53 expression activates apoptotic pathways in wild-type p53-bearing mesothelioma and enhances cytotoxicity of cisplatin and pemetrexed

The majority of malignant mesothelioma possesses the wild-type p53 gene with a homologous deletion of the INK4A/ARF locus containing the p14(ARF) and the p16(INK4A) genes. We examined whether forced expression of p53 inhibited growth of mesothelioma cells and produced anti-tumor effects by a combination of cisplatin (CDDP) or pemetrexed (PEM), the first-line drugs for mesothelioma treatments. Transduction of mesothelioma cells with adenoviruses bearing the p53 gene (Ad-p53) induced phosphorylation of p53, upregulated Mdm2 and p21 expression levels and decreased phosphorylation of pRb. The transduction generated cleavage of caspase-8 and -3, but not caspase-9. Cell cycle analysis showed increased G0/G1- or G2/M-phase populations and subsequently sub-G1 fractions, depending on cell types and Ad-p53 doses. Transduction with Ad-p53 suppressed viability of mesothelioma cells and augmented the growth inhibition by CDDP or PEM mostly in a synergistic manner. Intrapleural injection of Ad-p53 and systemic administration of CDDP produced anti-tumor effects in an orthotopic animal model. These data collectively suggest that Ad-p53 is a possible agent for mesothelioma in combination with the first-line chemotherapeutics.

Pemetrexed induces both intrinsic and extrinsic apoptosis through ataxia telangiectasia mutated/p53-dependent and -independent signaling pathways

Pemetrexed, a new-generation antifolate, has demonstrated promising single-agent activity in front- and second-line treatments of non-small cell lung cancer. However, the molecular mechanism of pemetrexed-mediated antitumor activity remains unclear. The current study shows that pemetrexed induced DNA damage and caspase-2, -3, -8, and -9 activation in A549 cells and that treatment with caspase inhibitors significantly abolished cell death, suggesting a caspase-dependent apoptotic mechanism. The molecular events of pemetrexed-mediated apoptosis was associated with the activation of ataxia telangiectasia mutated (ATM)/p53-dependent and -independent signaling pathways, which promoted intrinsic and extrinsic apoptosis by upregulating Bax, PUMA, Fas, DR4, and DR5 and activating the caspase signaling cascade. Supplementation with dTTP allowed normal S-phase progression and rescued apoptotic death in response to pemetrexed. Overall, our findings reveal that the decrease of thymidylate synthase and the increase of Bax, PUMA, Fas, DR4, and DR5 genes may serve as biomarkers for predicting responsiveness to pemetrexed.

TS gene polymorphisms are not good markers of response to 5-FU therapy in stage III colon cancer patients

AIM

Although the predictive and prognostic value of thymidylate synthase (TS) expression and gene polymorphism in colon cancer has been widely studied, the results are inconclusive probably because of methodological differences. With this study, we aimed to elucidate the role of TS gene polymorphisms genotyping in therapy response in stage III colon carcinoma patients treated with 5-FU adjuvant chemotherapy.

PATIENTS AND METHODS

251 patients diagnosed with stage III colon carcinoma treated with surgery followed by 5-FU based adjuvant therapy were selected. The variable number of tandem repeats (VNTR) and the single nucleotide polymorphism (SNP) in the 5'untranslated region of the TS gene were genotyped.

RESULTS

There was a positive association between tumor T stage and the VNTR genotypes (p = 0.05). In both univariate and multivariate survival analysis no effects of the studied polymorphisms on survival were found. However, there was an association between both polymorphisms and age. Among patients younger than 60 years, the patients homozygous for 2R seemed to have a better overall survival, whereas among the patients older than 67 this longer survival was seen by the carriers of other genotypes.

CONCLUSION

We conclude that the TS VNTR and SNP do not predict response to 5-FU therapy in patients with stage III colon carcinoma. However, age appears to modify the effects of TS polymorphisms on survival.

Thymidylate synthase and excision repair cross-complementing group-1 as predictors of responsiveness in mesothelioma patients treated with pemetrexed/carboplatin

PURPOSE

The pemetrexed/platinum agent combination represents the standard of care in first-line treatment for malignant pleural mesothelioma (MPM). However, there are no established indicators of responsiveness that can be used to optimize the treatment. This retrospective study aimed to assess the role of excision repair cross-complementing group-1 (ERCC1) and thymidylate synthase (TS) in tumors, and correlate expression levels and polymorphisms of these key determinants of drug activity with the outcome of MPM patients treated with carboplatin/pemetrexed in first-line setting.

EXPERIMENTAL DESIGN

Analysis of TS and ERCC1 polymorphisms, mRNA and protein expression was done by PCR and immunohistochemistry [with the H-score (histologic score)] in tumor specimens from 126 MPM patients, including 99 carboplatin-/pemetrexed-treated patients.

RESULTS

A significant correlation between low TS protein expression and disease control (DC) to carboplatin/pemetrexed therapy (P = 0.027), longer progression-free survival (PFS; P = 0.017), and longer overall survival (OS; P = 0.022) was found when patients were categorized according to median H-score. However, patients with the higher tertile of TS mRNA expression correlated with higher risk of developing progressive disease (P = 0.022), shorter PFS (P < 0.001), and shorter OS (P < 0.001). At multivariate analysis, the higher tertile of TS mRNA level and TS H-score confirmed their independent prognostic role for DC, PFS, and OS. No significant associations were found among ERCC1 protein expression, TS and ERCC1 polymorphisms, and clinical outcome.

CONCLUSIONS

In our series of carboplatin-/pemetrexed-treated MPM patients, low TS protein and mRNA levels were significantly associated to DC, improved PFS, and OS. Prospective trials for the validation of the prognostic/predictive role of TS in MPM patients treated with pemetrexed-based regimens are warranted.

Thymidylate synthase (TS) gene expression in primary lung cancer patients: a large-scale study in Japanese population

BACKGROUND

Previous small-sized studies showed lower thymidylate synthase (TS) expression in adenocarcinoma of the lung, which may explain higher antitumor activity of TS-inhibiting agents such as pemetrexed.

PATIENTS AND METHODS

To quantitatively measure TS gene expression in a large-scale Japanese population (n = 2621) with primary lung cancer, laser-captured microdissected sections were cut from primary tumors, surrounding normal lung tissues and involved nodes.

RESULTS

TS gene expression level in primary tumor was significantly higher than that in normal lung tissue (mean TS/β-actin, 3.4 and 1.0, respectively; P < 0.01), and TS gene expression level was further higher in involved node (mean TS/β-actin, 7.7; P < 0.01). Analyses of TS gene expression levels in primary tumor according to histologic cell type revealed that small-cell carcinoma showed highest TS expression (mean TS/β-actin, 13.8) and that squamous cell carcinoma showed higher TS expression as compared with adenocarcinoma (mean TS/β-actin, 4.3 and 2.3, respectively; P < 0.01); TS gene expression was significantly increased along with a decrease in the grade of tumor cell differentiation. There was no significant difference in TS gene expression according to any other patient characteristics including tumor progression.

CONCLUSION

Lower TS expression in adenocarcinoma of the lung was confirmed in a large-scale study.

In vitro study on the schedule-dependency of the interaction between pemetrexed, gemcitabine and irradiation in non-small cell lung cancer and head and neck cancer cells

Background

Based on their different mechanisms of action, non-overlapping side effects and radiosensitising potential, combining the antimetabolites pemetrexed (multitargeted antifolate, MTA) and gemcitabine (2',2'-difluorodeoxycytidine, dFdC) with irradiation (RT) seems promising. This in vitro study, for the first time, presents the triple combination of MTA, dFdC and irradiation using various treatment schedules.

Methods

The cytotoxicity, radiosensitising potential and cell cycle effect of MTA were investigated in A549 (NSCLC) and CAL-27 (SCCHN) cells. Using simultaneous or sequential exposure schedules, the cytotoxicity and radiosensitising effect of 24 h MTA combined with 1 h or 24 h dFdC were analysed.

Results

Including a time interval between MTA exposure and irradiation seemed favourable to MTA immediately preceding or following radiotherapy. MTA induced a significant S phase accumulation that persisted for more than 8 h after drug removal. Among different MTA/dFdC combinations tested, the highest synergistic interaction was produced by 24 h MTA followed by 1 h dFdC. Combined with irradiation, this schedule showed a clear radiosensitising effect.

Conclusions

Results from our in vitro model suggest that the sequence 24 h MTA → 1 h dFdC → RT is the most rational design and would, after confirmation in an in vivo setting, possibly provide the greatest benefit in the clinic.

Differential activation of cell death and autophagy results in an increased cytotoxic potential for trifluorothymidine compared to 5-fluorouracil in colon cancer cells

Trifluorothymidine (TFT) is part of the oral drug formulation TAS-102. Both 5-fluorouracil (5-FU) and TFT can inhibit thymidylate synthase and be incorporated into DNA. TFT shows only moderate cross-resistance to 5-FU. Therefore, we examined whether mechanistic differences in cell death could underlie their different modes of action in colorectal cancer cell lines (WiDR, Lovo92 and Colo320). Drug cytotoxicity was determined by SRB- and clonogenic assays, cell death by flow cytometry (PI and annexin V), caspase cleavage by Western blotting and activity assays and in vivo activity in the hollow fiber assay. The IC(50) values of TFT were 1-6 fold lower than for 5-FU, and clonogenic survival was less than 0.9% at 3 muM TFT, while 2-20% of the cells still survived after 20 muM 5-FU. In general, TFT was a more potent inducer of apoptosis than 5-FU, although the contribution of caspases varied between the used cell lines and necrosis-like cell death was detected. Accordingly, both drugs induced caspase (Z-VAD) independent cell death and lysosomal cathepsin B was involved. Activation of autophagy recovery mechanisms was only triggered by 5-FU, but not by TFT as determined by LC3B expression and cleavage. Inhibition of autophagy by 3-MA in 5-FU exposed cells reduced cell survival. Also, in vivo TFT (as TAS-102) caused more cell death than a 5-FU formulation. We conclude that TFT and 5-FU induce cell death via both caspase-dependent and independent mechanisms. The TFT was more potent than 5-FU, because it induces higher levels of cell death and does not elicit an autophagic survival response in the cancer cell lines. This provides a strong molecular basis for further application of TFT in cancer therapy.

Thymidylate Synthase But Not Excision Repair Cross-Complementation Group 1 Tumor Expression Predicts Outcome in Patients With Malignant Pleural Mesothelioma Treated With Pemetrexed-Based Chemotherapy

Purpose

The relationship between thymidylate synthase (TS) expression and outcome in patients with malignant pleural mesothelioma (MPM) treated with pemetrexed (P) was retrospectively evaluated.

Patients and Methods

Sixty histologically confirmed patients with MPM previously treated with P and platinum (45 of 60) or as single agent (15 of 60) were retrospectively considered. Eighty-one control patients with MPM not P-treated were also evaluated. TS and excision repair cross-complementation group 1 (ERCC1) gene expression levels were evaluated by real-time polymerase chain reaction and by immunohistochemistry using the H-score.

Results

Median TS H-score value was 90 (range, 5 to 240). A significant correlation between low TS protein expression and longer time to progression (TTP; 17.9 v 7.9 months; hazard ratio [HR], 2.05, 95% CI, 1.19 to 3.77; P = .02) or overall survival (OS; 30 v 16.7 months; HR, 2.38; 95% CI, 1.15 to 4.91; P = .019) was found when patients were divided according to median H-score. Conversely, TS mRNA levels were not significantly correlated with outcome. In platinum-treated patients (n = 45), no correlation was found with survival according to ERCC1 median H-score, but patients in the lower tertile had a significantly shorter survival (HR, 3.06; 95% CI, 1.08 to 8.69; P = .035). In control MPMs, TS had no prognostic role. At multivariate analysis, TS protein levels were the only independent prognostic factor for both TTP (HR, 2.71; 95% CI, 1.13 to 6.49; P = .02) and OS (HR, 6.91; 95% CI, 1.90 to 25.07; P = .003).

Conclusion

In patients with MPM treated with P-based chemotherapy, low TS protein levels are predictive of improved TTP and OS. The role of TS assessment is worth of prospective validation in future studies on MPM.

Drug development in advanced colorectal cancer: challenges and opportunities

Despite recent advances in treatment options, advanced colorectal cancer (ACC) remains a leading cause of cancer death worldwide, and new therapies are needed to improve the grim prognosis of this disease. Drug development in ACC faces the challenges of a constrained pipeline, a paucity of patients enrolled in clinical trials, and an outdated "one drug fits all" model of clinical research. This article discusses potential innovations in clinical trial design--including enrichment strategies, novel patient populations, and the use of randomization in the phase 2 setting--to optimize the testing of new therapies. It concludes with a selection of promising agents and pathways under investigation in ACC.

XIII International Charles Heidelberger Symposium and 50 Years of Fluoropyrimidines in Cancer Therapy Held on september 6 to 8, 2007 at New York University Cancer Institute, Smilow Conference Center

This conference opened with Franco Muggia, host and principal organizer, thanking Joseph Landolph, co-Chair of the International Scientific Organizing Committee and its members (Franco Muggia, co-Chair, Max Costa, Steven Burakoff, Howard Hochster, Eliezer Huberman, John Bertram, Peter Danenberg, and Richard Moran); the members of the Local Organizing Committee (Drs. Costa, Guttenplan, Geacintov, and Hochster); and the Charles and Patricia Heidelberger Foundation for Cancer Research for developing the scientific program and for working to help him create this special symposium honoring the late Charles Heidelberger, former president of the American Association for Cancer Research, member of the National Academy of Sciences, and extraordinary scientist in the fields of carcinogenesis and cancer chemotherapy. It was most appropriate to commemorate the 50th anniversary of the patent obtained by him for 5-fluorouracil (5FU), a drug that came to symbolize the promise chemotherapy of nonhematologic malignancies. After this compound was shown to be helpful in the treatment of colorectal and breast cancers, Dr. Heidelberger proceeded to develop other fluoropyrimidines and to inspire Ph.D. students and postdoctoral fellows to investigate their mechanisms of action and to develop assays applicable to clinical specimens (what we now refer to as translational science). Steven Burakoff, director of the NYU Cancer Institute (2000 to 2008), followed with welcoming remarks. Dr. Burakoff pointed to his personal fortuitous connection to the Symposium: The famous immunologist, Michael Heidelberger, Charles' father, who was known as the Father of Immunochemistry, trained Elvin Kabat while at Columbia, who trained Baruch Benacerraf, who moved from NYU to Harvard and subsequently became Burakoff's mentor. The renowned NYU Division of Immunology carries the name Michael Heidelberger because he spent more than 30 years in the Department of Pathology at the NYU School of Medicine after retiring from Columbia University.

Heat shock protein 90 inhibition abrogates hepatocellular cancer growth through cdc2-mediated G2/M cell cycle arrest and apoptosis

PURPOSE

17-(demethoxy), 17-allylamino geldanamycin (17-AAG) suppresses growth in some cancers by inhibiting Heat shock protein 90 (Hsp90). We examined the effects of 17-AAG-mediated Hsp90 inhibition on human hepatocellular carcinoma (HCC) growth in vitro and in vivo.

METHODS

Human HCC cell lines, Hep3B and HuH7, were exposed to 17-AAG and cell viabilities and apoptosis were determined. Cell cycle profiles were analyzed and the G(2)/M cell cycle checkpoint proteins cdc2 and cyclin B1 were examined. Studies were performed to determine whether 17-AAG-mediated cdc2 decrease was due to altered gene expression, transcription, or protein degradation. The effects of 17-AAG on Hep3B and HuH7 xenograft growth in athymic nude mice were also examined.

RESULTS

Hep3B and HuH7 treated with 17-AAG versus untreated controls showed decreased cell viability and increased apoptosis. Cells treated with 17-AAG also showed an increased fraction in G(2)/M phase and an associated decrease in cdc2 through protein degradation rather than through other mechanisms. Hsp90 inhibition by 17-AAG also decreased HCC xenograft growth in association with decreased cdc2 expression.

CONCLUSIONS

17-AAG-mediated inhibition of Hsp90 abrogates human HCC cell growth in vitro and in vivo through cdc2 decrease, which in turn induces G(2)/M cell cycle arrest and apoptosis. Hsp90 is a mediator of HCC growth and survival and its inhibition may serve as a potential treatment.

Effects of small interfering RNA targeting thymidylate synthase on survival of ACC3 cells from salivary adenoid cystic carcinoma

Background

Thymidylate synthase (TS) is an important target for chemotherapeutic treatment of cancer and high expression of TS has been associated with poor prognosis or refractory disease in several cancers including colorectal and head and neck cancer. Although TS is known to regulate cell cycles and transcription factors, its potency as a therapeutic target has not been fully explored in adenoid cystic carcinoma (ACC).

Methods

An ACC cell line (ACC3) was transfected with siRNA targeting the TS gene and inhibition of cell growth and induction of apoptosis-associated molecules were evaluated in vitro. In addition, the in vivo effect of TS siRNA on tumor progression was assessed using a xenograft model.

Results

Our results demonstrated that ACC3 cells showed significantly higher TS expression than non-cancer cell lines and the induction of TS siRNA led to inhibition of cell proliferation. The effect was associated with an increase in p53, p21, and active caspase-3 and S-phase accumulation. We also found up-regulation of spermidine/spermine N1-acetyltransferase (SSAT), a polyamine metabolic enzyme. Furthermore, treatment with TS siRNA delivered by atelocollagen showed a significant cytostatic effect through the induction of apoptosis in a xenograft model.

Conclusion

TS may be an important therapeutic target and siRNA targeting TS may be of potential therapeutic value in ACC.

Oxaliplatin activity in selected and unselected human ovarian and colorectal cancer cell lines

Oxaliplatin is used for treatment of colon cancer in combination with 5-fluorouracil or irinotecan. Oxaliplatin has similar, but also different resistant mechanisms as cisplatin. We studied the activity of oxaliplatin in ovarian and colon cancer cells with different resistance patterns to cisplatin. The 40-fold cisplatin-resistant cell line ADDP was only 7.5-fold resistant to oxaliplatin. The gemcitabine-resistant AG6000 cell line, 9-fold resistant to cisplatin, was not cross-resistant. LoVo-175X2, with mutant p53 showed no resistance compared to the empty vector control. However, LoVo-Li, with inactive p53, was 3.6-fold resistant corresponding to decreased accumulation and Pt adducts. Accumulation and DNA adducts formation showed no significant correlation with oxaliplatin sensitivity. Cell cycle distribution after exposure to oxaliplatin showed arrest in G2/M (A2780) or in S-phase (LoVo-92) for wt-p53 cells. ADDP and LoVo-Li showed G1 arrest followed by S-phase arrest and no changes in distribution, respectively. The cell cycle related proteins Cyclins A and B1 and (p)CDC25C were marginally affected by oxaliplatin. Expression of hCTR1 was decreased in ADDP, LoVo-Li and AG6000, OCT1 decreased in ADDP and AG6000 and OCT3 in LoVo-175X2, compared to the parental cell lines. In ADDP and LoVo-175X2 ATP7A and B were decreased but were increased in AG6000. From this study it can be concluded that changes in cell cycle distribution were cell line dependent and not related to changes in expression of Cyclin A or B1. Oxaliplatin accumulation was related to hCTR1 and, at low concentration, ATP7A to DNA adducts formation while the retention was related to hCTR1, OCT2 and ATP7B.

Functional inactivity and mutations of p53 differentially affect sensitivity to 5-fluorouracil and antifolate inhibitors of thymidylate synthase (TS) by altering TS levels in colorectal cancer cells

The role of p53 in altering TS expression and chemosensitivity was studied in colorectal cancer cells with wildtype, mutated, or functionally inactive p53. Cytotoxicity of TS inhibitors was studied by MTT, while PCR, Western blot, and activity assays assessed whether p53 status influenced TS expression. Lovo-175X2 cells showed increased resistance to TS inhibitors and significantly greater than wildtype expression and activity of TS. In contrast, Lovo-273X17 and Lovo-li were more sensitive to TS inhibitors and had reduced TS expression, due either to reduced TS mRNA or altered regulation of TS activity. Thus, functional inactivity and mutations of p53 differentially affect TS, potentially influencing response to TS inhibitor-based treatment.

Trifluorothymidine induces cell death independently of p53

Trifluorothymidine (TFT), a potent anticancer agent, inhibits thymidylate synthase (TS) and is incorporated into the DNA, both events resulting in cell death. Cell death induction related to DNA damage often involves activation of p53. We determined the role of p53 in TFT cytotoxicity and cell death induction, using, respectively, the sulforhodamine B-assay and FACS analysis, in a panel of cell lines with either wild type, inactive, or mutated p53. Neither TFT cytotoxicity nor cell death induction changed with TFT exposure in cell lines with wt, inactive or mutated p53.

CONCLUSION

sensitivity to TFT is not dependent on the expression of wt p53.

Colorectal carcinomas with microsatellite instability display increased thymidylate synthase gene expression levels

BACKGROUND

This study investigated whether patients with colorectal cancer (CRC) who have tumors with high microsatellite instability (MSI; MSI-H) had an altered expression of the folate and methyl-group metabolism. The gene expression levels of thymidylate synthase (TS), reduced folate carrier (RFC-1), folylpolyglutamate synthase (FPGS), and methylenetetrahydrofolate reductase (MTHFR) in mucosa and tumor were compared with patients with MSS. Furthermore, the influence of TS polymorphisms on TS gene expression levels and MSI-H was studied.

PATIENTS AND METHODS

The microsatellite status (MSI-H, low instability [MSI-L], or stable [MSS]) and TS polymorphisms were analyzed in genomic DNA from 181 patients with CRC. Gene expression levels of TS, RFC-1, FPGS, and MTHFR in mucosa and tumors were quantified and the difference in TS expression between tumor and mucosa was designated DeltaTS.

RESULTS

Significantly higher gene expression levels of TS (P < .0001) were detected in patients with CRC with MSI-H compared with MSS/MSI-L tumors. Gene expression of TS and FPGS were significantly higher in right-sided MSI-H tumors compared with right-sided MSS/MSI-L tumors (P < .0001, P = .041, respectively). A significant correlation between DeltaTS and the number of unstable markers was found (P < .0001). An inverse association between age and TS expression was found in MSI tumors (r = -0.57; P = .0004) and also in right-sided tumors (r = -0.25, P = .011) regardless of MSI status. No relation was detected between MSI status and the TS polymorphisms or between the TS polymorphisms and TS expression.

CONCLUSION

This study has revealed, for the first time, that age and the frequency of unstable MSI markers were factors that were linked to the variability in TS gene expression in tumors.