Thymidylate synthase as a determinant of pemetrexed sensitivity in non-small cell lung cancer. Br J Cancer. 2011;104:1594-1601. [PMID: 21487406 PMCID: PMC3101907 DOI: 10.1038/bjc.2011.129]

Novel mass spectrometry-based assay for thymidylate synthase activity

Thymidylate synthase (TS) is an enzyme responsible for the conversion of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP), with the co-substrate 5,10-methylenetetrahydrofolate (5,10-CH2-THF) as the methyl donor. TS is the only enzyme capable of de novo biosynthesis of dTMP in humans, a nucleotide crucial for DNA synthesis and therefore cell proliferation and survival. As such, TS is a major drug target in chemotherapy by compounds such as 5-fluorouracil. Due to the clinical and physiological importance of TS, the ability to accurately assay its activity is crucial. Several assays have been developed for this purpose, relying on spectrophotometry or radioisotope labeling methods. In this study, we have developed a liquid chromatography - mass spectrometry-based method for assessing TS activity by direct and specific measurement of the reaction product, dTMP. The assay was tested on mouse liver homogenates. We noted that excessive 5,10-CH2-THF concentration (400 µM) led to substrate inhibition and therefore 200 µM was used. The activity assayed at 1 µM dUMP was linear with protein content and time (up to 60 min) and was 0.56 ± 0.12 pmol/mg protein/min, in line with previously reported values. Additionally, by using a high mass resolution Orbitrap instrument side reactions were monitored, revealing major changes in folate pools and nucleotide metabolism. These findings highlight the value of the developed TS assay for routine TS activity monitoring in complex matrixes such as clinical material.

Predictive Impact of Diffuse Positivity for TTF-1 Expression in Patients Treated With Platinum-Doublet Chemotherapy Plus Immune Checkpoint Inhibitors for Advanced Nonsquamous NSCLC

Introduction

Pervious studies reported the association of TTF-1 expression with the efficacy of platinum-doublet chemotherapy in combination with immune checkpoint inhibitors in advanced nonsquamous NSCLC. Nevertheless, the predictive value of extent of TTF-1 expression (diffuse or focal TTF-1 positivity) remains unclear.

Methods

The present study retrospectively reviewed 74 patients with TTF-1-positive recurrent or advanced nonsquamous NSCLC receiving first-line chemoimmunotherapy in a single institution in Japan. TTF-1 expression score in pretreatment tumor specimens was evaluated using immunohistochemistry, and the impact of chemoimmunotherapy response was analyzed.

Results

In the total cohort, ≥50% of the tumor cells were TTF-1 positive (i.e., diffusely TTF-1 positive) in specimens of 61 patients (82.4%), whereas 10% to 49% of the tumor cells were TTF-1 positive (i.e., focally TTF-1 positive) in specimens of the remaining 13 patients (17.6%). In multivariate analysis, the median progression-free survival and overall survival (OS) were significantly longer in patients with diffusely TTF-1-positive tumors than in those with focally TTF-1-positive tumors (14.2 versus 9.2 mo, p = 0.01 and 30.2 versus 17.3 mo, p = 0.01, respectively). Moreover, the median OS was significantly longer in patients receiving chemoimmunotherapy including pemetrexed than in those receiving chemoimmunotherapy not including pemetrexed among the patients with diffusely TTF-1-positive tumors (not attained versus 23.2 mo, p < 0.01).

Conclusions

The positive extent of diffuse TTF-1 expression associated with patient outcome was an independent predictive factor for better progression-free survival and OS in patients with advanced nonsquamous NSCLC receiving chemoimmunotherapy.

Association of Antifolate Response Signature Status and Clinical Activity of Pemetrexed-Platinum Chemotherapy in Non-Small Cell Lung Cancer: The Piedmont Study

PURPOSE

The Piedmont study is a prospectively designed retrospective evaluation of a new 48-gene antifolate response signature (AF-PRS) in patients with locally advanced/metastatic nonsquamous (NS) non-small cell lung cancer (NSCLC) treated with pemetrexed-containing platinum doublet chemotherapy (PMX-PDC). The study tested the hypothesis that AF-PRS identifies patients with NS-NSCLC who have a higher likelihood of responding positively to PMX-PDC. The goal was to gather clinical evidence supporting AF-PRS as a potential diagnostic test.

EXPERIMENTAL DESIGN

Residual pretreatment FFPE tumor samples and clinical data were analyzed from 105 patients treated with first-line (1L) PMX-PDC. Ninety-five patients had sufficient RNA sequencing (RNA-seq) data quality and clinical annotation for inclusion in the analysis. Associations between AF-PRS status and associate genes and outcome measures including progression-free survival (PFS) and clinical response were evaluated.

RESULTS

Overall, 53% of patients were AF-PRS(+), which was associated with extended PFS, but not overall survival, versus AF-PRS(-) (16.6 months vs. 6.6 months; P = 0.025). In patients who were stage I to III patients at the time of treatment, PFS was further extended in AF-PRS(+) versus AF-PRS(-) (36.2 months vs. 9.3 months; P = 0.03). Complete response (CR) to therapy was noted in 14 of 95 patients. AF-PRS(+) preferentially selected a majority (79%) of CRs, which were evenly split between patients stage I to III (six of seven) and stage IV (five of seven) at the time of treatment.

CONCLUSIONS

AF-PRS identified a significant population of patients with extended PFS and/or clinical response following PMX-PDC treatment. AF-PRS may be a useful diagnostic test for patients indicated for systemic chemotherapy, especially when determining the optimal PDC regimen for locally advanced disease.

TYMS promotes genomic instability and tumor progression in Ink4a/Arf null background

We previously showed that elevated TYMS exhibits oncogenic properties and promotes tumorigenesis after a long latency, suggesting cooperation with sequential somatic mutations. Here we report the cooperation of ectopic expression of human TYMS with loss of Ink4a/Arf, one of the most commonly mutated somatic events in human cancer. Using an hTS/Ink4a/Arf -/- genetically engineered mouse model we showed that deregulated TYMS expression in Ink4a/Arf null background accelerates tumorigenesis and metastasis. In addition, tumors from TYMS-expressing mice were associated with a phenotype of genomic instability including enhanced double strand DNA damage, aneuploidy and loss of G1/S checkpoint. Downregulation of TYMS in vitro decreased cell proliferation and sensitized tumor cells to antimetabolite chemotherapy. In addition, depletion of TYMS in vivo by TYMS shRNA reduced tumor incidence, delayed tumor progression and prolonged survival in hTS/Ink4a/Arf -/- mice. Our data shows that activation of TYMS in Ink4a/Arf null background enhances uncontrolled cell proliferation and tumor growth, supporting the development of new agents and strategies targeting TYMS to delay tumorigenesis and prolong survival.

First-Line Treatment of Driver-Negative Non-Small Cell Lung Cancer

Immunotherapy-based regimens are an established standard of care for the first-line treatment of driver-negative (EGFR/ALK/ROS WT) advanced non-small cell lung cancer. With multiple immune-based regimens approved in the first-line setting, clinicians are faced in practice with a variety of treatment choices. This article summarizes the most up-to-date trial data on treatments for driver-negative advanced non-small cell lung cancer, including immunotherapy monotherapy, chemoimmunotherapy, and combination immunotherapy, providing a framework for clinicians based on PD-L1 and smoking status. A multibiomarker assay that may best predict immunotherapy response remains an active area of research.

Activity of pemetrexed in pre-clinical chordoma models and humans

Chordomas are rare slow growing tumors, arising from embryonic remnants of notochord with a close predilection for the axial skeleton. Recurrence is common and no effective standard medical therapy exists. Thymidylate synthase (TS), an intracellular enzyme, is a key rate-limiting enzyme of DNA biosynthesis and repair which is primarily active in proliferating and metabolically active cells. Eighty-four percent of chordoma samples had loss of TS expression which may predict response to anti-folates. Pemetrexed suppresses tumor growth by inhibiting enzymes involved in folate metabolism, resulting in decreased availability of thymidine which is necessary for DNA synthesis. Pemetrexed inhibited growth in a preclinical mouse xenograft model of human chordoma. We report three cases of metastatic chordoma that had been heavily treated previously with a variety of standard therapies with poor response. In two cases, pemetrexed was added and objective responses were observed on imaging with one patient on continuous treatment for > 2 years with continued shrinkage. One case demonstrated tumor growth after treatment with pemetrexed. The two cases which had a favorable response had a loss of TS expression, whereas the one case with progressive disease had TS present. These results demonstrate the activity of pemetrexed in recurrent chordoma and warrant a prospective clinical trial which is ongoing (NCT03955042).

Exonuclease 1 genetic variant is associated with clinical outcomes of pemetrexed chemotherapy in lung adenocarcinoma

Pemetrexed is an anti-folate agent which is one of the most frequently used chemotherapy agents for non-squamous non-small cell lung cancer (NSCLC) patients. However, clinical response to pemetrexed chemotherapy and survival outcome of patients varies significantly. We evaluated whether the genetic variants in miRNA target sites may affect the treatment outcome of pemetrexed chemotherapy in lung adenocarcinoma patients. One hundred SNPs in miRNA binding regions in cancer-related genes were obtained from the crosslinking, ligation, and sequencing of hybrids (CLASH) and CancerGenes database, and the associations with the response to pemetrexed chemotherapy and survival outcomes were investigated in 314 lung adenocarcinoma patients. Two polymorphisms, EXO1 rs1047840G>A and CAMKK2 rs1653586G>T, were significantly associated with worse chemotherapy response (adjusted odds ratio [aOR] = 0.41, 95% CI = 0.24-0.68, P = 0.001, under dominant model; and aOR = 0.33, 95% CI = 0.16-0.67, P = 0.002, under dominant model, respectively) and worse OS (adjusted hazard ratio [aHR] = 1.34, 95% CI = 1.01-1.77, P = 0.04, under dominant model; and aHR = 1.50, 95% CI = 1.06-2.13, P = 0.02, under dominant model, respectively) in multivariate analyses. Significantly increased luciferase activity was noted in EXO1 rs1047840 A allele compared to G allele. In conclusion, two SNPs in miRNA binding sites, especially EXO1 rs1047840G>A, were associated with the chemotherapy response and survival outcome in lung adenocarcinoma patients treated with pemetrexed.

miR-145-5p Targets Sp1 in Non-Small Cell Lung Cancer Cells and Links to BMI1 Induced Pemetrexed Resistance and Epithelial-Mesenchymal Transition

Pemetrexed is a folic acid inhibitor used as a second-line chemotherapeutic agent for the treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC), which accounts for 85% of lung cancers. However, prolonged treatment with pemetrexed may cause cancer cells to develop resistance. In this study, we found increased expressions of BMI1 (B Lymphoma Mo-MLV insertion region 1 homolog) and Sp1 and a decreased expression of miR-145-5p was found in pemetrexed-resistant A400 cells than in A549 cells. Direct Sp1 targeting activity of miR-145-5p was demonstrated by a luciferase based Sp1 3'-UTR reporter. Changed expression of miR-145-5p in A400 or A549 cells by transfection of miR-145-5p mimic or inhibitor affected the sensitivity of the cells to pemetrexed. On the other hand, the overexpression of Sp1 in A549 cells caused the decreased sensitivity to pemetrexed, induced cell migratory capability, and epithelial-mesenchymal transition (EMT) related transcription factors such as Snail Family Transcriptional Repressor 1 and Zinc Finger E-Box Binding Homeobox 1. In addition, the overexpression of BMI1 in the A549 cells resulted in an increase in Sp1 and a decrease in miR-145-5p accompanied by the elevations of cell proliferation and EMT transcription factors, which could be reduced by the overexpression of miR-145-5p or by treatment with the Sp1 inhibitor of mithramycin A. In conclusion, the results of this study suggest that the downregulation of miR-145-5p by BMI1 overexpression could lead to the enhanced expression of Sp1 to induce the EMT process in pemetrexed-resistant NSCLC cells. These results suggest that increasing miR-145-5p expression by delivering RNA drugs may serve as a sensitizing agent for pemetrexed-resistant NSCLC patients.

Towards establishment of a plant-based model to assess the novel anti-cancerous lead molecule(s): An in silico, in vivo and in vitro assessment of some potential anti-cancerous drugs on Lathyrus sativus L

The drug development process is one of the important aspects of medical biology. The classical lead identification strategy in the way of drug development based on animal cell is time-consuming, expensive and involving ethical issues. The following study aims to develop a novel plant-based screening of drugs. Study shows the efficacy of certain anti-cancerous drugs (Pemetrexed, 5-Fluorouracil, Methotrexate, Topotecan and Etoposide) on a plant-based (Lathyrus sativus L.) system. Two important characteristics of cancer cells were observed in the colchicine-treated polyploid cell and the callus, where the chromosome numbers were unusual and the division of cells were uncontrolled respectively. With increasing concentration, the drugs significantly reduced the mitotic index, ploidy level and callus growth. Increasing Pemetrexed concentration decreased the plant DHFR activity. A decrease in total RNA content was observed in 5-FU and Methotrexate with increasing concentrations of the drugs. Etoposide and Topotecan inhibited plant topoisomerase II and topoisomerase I activities, which was justified through plasmid nicking and comet assay, respectively. Molecular and biochemical study revealed similar results to the animal system. The in silico study had been done, and the structural similarity of drug binding domains of L. sativus and human beings had also been established. The binding site of the selected drugs to the domains of plant target proteins was also determined. Experimental results are significant in terms of the efficacy of known anti-cancerous drugs on the plant-based system. The proposed assay system is a cost-effective, convenient and less time-consuming process for primary screening of anti-cancerous lead molecules.

Regulation of thymidylate synthase: an approach to overcome 5-FU resistance in colorectal cancer

Thymidylate synthase is the rate-limiting enzyme required for DNA synthesis and overexpression of this enzyme causes resistance to cancer cells. Long treatments with 5-FU cause resistance to Thymidylate synthase targeting drugs. We have also compiled different mechanisms of drug resistance including autophagy and apoptosis, drug detoxification and ABC transporters, drug efflux, signaling pathways (AKT/PI3K, RAS-MAPK, WNT/β catenin, mTOR, NFKB, and Notch1 and FOXM1) and different genes associated with resistance in colorectal cancer. We can overcome 5-FU resistance in cancer cells by regulating thymidylate synthase by natural products (Coptidis rhizoma), HDAC inhibitors, mTOR inhibitors, Folate antagonists, and several other drugs which have been used in combination with TS inhibitors. This review is a compilation of different approaches reported for the regulation of thymidylate synthase to overcome resistance in colorectal cancer cells.

Isolation and characterization of two homolog phages infecting Pseudomonas aeruginosa

Bacteriophages (phages) are capable of infecting specific bacteria, and therefore can be used as a biological control agent to control bacteria-induced animal, plant, and human diseases. In this study, two homolog phages (named PPAY and PPAT) that infect Pseudomonas aeruginosa PAO1 were isolated and characterized. The results of the phage plaque assay showed that PPAT plaques were transparent dots, while the PPAY plaques were translucent dots with a halo. Transmission electron microscopy results showed that PPAT (65 nm) and PPAY (60 nm) strains are similar in size and have an icosahedral head and a short tail. Therefore, these belong to the short-tailed phage family Podoviridae. One-step growth curves revealed the latent period of 20 min and burst time of 30 min for PPAT and PPAY. The burst size of PPAT (953 PFUs/infected cell) was higher than that of PPAY (457 PFUs/infected cell). Also, the adsorption rate constant of PPAT (5.97 × 10⁻⁷ ml/min) was higher than that of PPAY (1.32 × 10⁻⁷ ml/min) at 5 min. Whole-genome sequencing of phages was carried out using the Illumina HiSeq platform. The genomes of PPAT and PPAY have 54,888 and 50,154 bp, respectively. Only 17 of the 352 predicted ORFs of PPAT could be matched to homologous genes of known function. Likewise, among the 351 predicted ORFs of PPAY, only 18 ORFs could be matched to genes of established functions. Homology and evolutionary analysis indicated that PPAT and PPAY are closely related to PA11. The presence of tail fiber proteins in PPAY but not in PPAT may have contributed to the halo effect of its plaque spots. In all, PPAT and PPAY, newly discovered P. aeruginosa phages, showed growth inhibitory effects on bacteria and can be used for research and clinical purposes.

Micro-RNA-215 and -375 regulate thymidylate synthase protein expression in pleural mesothelioma and mediate epithelial to mesenchymal transition

The standard front-line treatment for pleural mesothelioma (PM) is pemetrexed-based chemotherapy, whose major target is thymidylate synthase (TS). In several cancer models, miR-215 and miR-375 have been shown to target TS, while information on these miRNAs in PM are still limited although suggest their role in epithelial to mesenchymal transition. Seventy-one consecutive PM tissues (4 biphasic, 7 sarcomatoid, and 60 epithelioid types) and 16 commercial and patient-derived PM cell lines were screened for TS, miR-215, and miR-375 expression. REN and 570B cells were selected for miR-215 and miR-375 transient transfections to test TS modulation. ZEB1 protein expression in tumor samples was also tested. Moreover, genetic profile was investigated by means of BAP1 and p53 immunohistochemistry. Expression of both miR-215 and miR-375 was significantly higher in epithelioid histotype. Furthermore, inverse correlation between TS protein and both miR-215 and miR-375 expression was found. Efficiently transfected REN and 570B cell lines overexpressing miR-215 and miR-375 showed decreased TS protein levels. Epithelioid PM with a mesenchymal component highlighted by reticulin stain showed significantly higher TS and ZEB1 protein and lower miRNA expression. A better survival was recorded for BAP1 lost/TS low cases. Our data indicate that miR-215 and miR-375 are involved in TS regulation as well as in epithelial-to-mesenchymal transition in PM.

Real-World Management and Outcomes of Crizotinib-Treated ROS1-Rearranged NSCLC: A Retrospective Canadian Cohort

The use, safety and effectiveness of crizotinib as part of the management of ROS1-rearranged NSCLC patients in a real-world Canadian clinical cohort was the focus of this retrospective review. Twenty-one ROS1-rearranged patients with advanced/metastatic disease receiving crizotinib between 2014-2020 were identified; crizotinib demonstrated tolerability and effectiveness in this population where outcomes were similar to those described in other crizotinib-treated real-world cohorts, but lower than those of the PROFILE 1001 clinical trial population. Systemic anti-cancer therapy prior to crizotinib initiation occurred in half of the study cohort, with platin-pemetrexed and immune checkpoint inhibitors being most common. Platin-pemetrexed showed good effectiveness in this cohort, but despite high prevalence of upregulated PD-L1 expression, immune checkpoint inhibitors showed poor effectiveness in his cohort. Among all systemic therapies received, crizotinib showed the most effective disease control, although longer intervals between diagnosis and crizotinib initiation were more common among those showing a lack of clinical response to crizotinib, and patients with brain metastases at the time of crizotinib initiation also showed increased diagnosis to crizotinib initiation intervals and decreased clinical response to crizotinib. This study reveals crizotinib has clinical benefit, but timely identification of ROS1-rearrangements and initiation targeted therapies appears important to maximize outcome in this population.

Utility of TMPRSS4 as a Prognostic Biomarker and Potential Therapeutic Target in Patients with Gastric Cancer

BACKGROUND

Transmembrane serine protease 4 (TMPRSS4) belongs to the family of type II transmembrane serine proteases that are known to be upregulated in many malignant tumors. However, there is a paucity of studies documenting the clinical impact and biological effects of TMPRSS4 on gastric cancer (GC) patients who underwent surgery.

METHODS

Tissues samples were obtained from 105 patients with GC who underwent gastrectomy followed by adjuvant chemotherapy, excluding those at stage I. The expression of TMPRSS4 was examined through immunohistochemical analysis. The association between TMPRSS4 expression and clinico-pathological features as well as prognosis was assessed. Moreover, the effects of TMPRSS4 expression on cell migration and sensitivity to 5-FU were investigated.

RESULTS

The expression rate of TMPRSS4 was 56.3% (59/105) in GC cases. The expression of TMPRSS4 was positively correlated with the depth of tumor (T) and venous (V) invasion. The 5-year overall survival (OS) and recurrence-free survival (RFS) rates of the TMPRSS4-positive group was significantly lower than that of the TMPRSS4-negative group (p=0.0001 and p=0.005, respectively). Especially, there was significant differences in OS and RFS of patients with stage III cancer between the two groups (p=0.0064 and 0.012, respectively). Multivariate analysis demonstrated that TMPRSS4 expression and the stage of cancer were crucial prognostic factors for RFS. TMPRSS4-silenced GC cells exhibited increased sensitivity to 5-FU when compared with the non-specific control siRNA-transfected cells.

CONCLUSION

TMPRSS4 can be considered as a potential prognostic biomarker, especially for stage III, and a promising therapeutic target for GC.

Plasma Endoglin is Associated with Favorable Outcome for Pemetrexed-Based Therapy in Advanced Non-Small Cell Lung Cancer

Purpose

Pemetrexed-based chemotherapy (Pem-C) is the first-line chemotherapy for advanced non-squamous non-small cell lung cancer (NSCLC). However, limited tumor-associated proteins in blood are available to predict pemetrexed response and/or survival.

Patients and Methods

Plasma samples from three responders and three nonresponders with stage IIIB–IV NSCLC were collected prior to Pem-C and analyzed using Proteome Profiler^TM Human XL Oncology Array to detect 84 oncology-related proteins. The plasma concentrations of cathepsin S, endoglin (ENG), and matrix metalloproteinases 3 and 9 in 71 patients with advanced NSCLC treated with Pem-C were further measured using enzyme-linked immunosorbent assay based on the remarkable differences in the four proteins between responders and nonresponders in the array results.

Results

Pem-C responders had significantly higher ENG levels but not the other three markers than nonresponders (mean ENG level: 27.1 ± 7.4 vs 22.3 ± 6.9, p < 0.01). High ENG concentration was correlated with improved progression-free survival (hazard ratio [HR]: 0.52, 95% confidence interval [CI]: 0.31–0.86, p < 0.01) and overall survival (HR: 0.55, 95% CI: 0.32–0.94, p < 0.05) in patients treated with Pem-C, and the ENG level was an independent factor in our cohort (HR: 0.54, 95% CI: 0.33–0.89, p < 0.05). ENG concentration in Pem-C responders also significantly increased at the time of best response (p < 0.05).

Conclusion

Cumulatively, this study reveals that ENG is correlated with Pem-C responsiveness in patients, which indicates the potential use of plasma ENG levels as a non-invasive biomarker for pemetrexed-based treatment in patients with non-squamous NSCLC.

Methionine synthase is essential for cancer cell proliferation in physiological folate environments

Folate metabolism can be an effective target for cancer treatment. However, standard cell culture conditions utilize folic acid, a non-physiological folate source for most tissues. We find that the enzyme that couples folate and methionine metabolic cycles, methionine synthase, is required for cancer cell proliferation and tumour growth when 5-methyl tetrahydrofolate (THF), the major folate found in circulation, is the extracellular folate source. In such physiological conditions, methionine synthase incorporates 5-methyl THF into the folate cycle to maintain intracellular levels of the folates needed for nucleotide production. 5-methyl THF can sustain intracellular folate metabolism in the absence of folic acid. Therefore, cells exposed to 5-methyl THF are more resistant to methotrexate, an antifolate drug that specifically blocks folic acid incorporation into the folate cycle. Together, these data argue that the environmental folate source has a profound effect on folate metabolism, determining how both folate cycle enzymes and antifolate drugs impact proliferation.

Upregulation of Thymidylate Synthase Induces Pemetrexed Resistance in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an invasive malignancy that develops in the pleural cavity, and antifolates are used as chemotherapeutics for treating. The majority of antifolates, including pemetrexed (PMX), inhibit enzymes involved in purine and pyrimidine synthesis. MPM patients frequently develop drug resistance in clinical practice, however the associated drug-resistance mechanism is not well understood. This study was aimed to elucidate the mechanism underlying resistance to PMX in MPM cell lines. We found that among the differentially expressed genes associated with drug resistance (determined by RNA sequencing), TYMS expression was higher in the established resistant cell lines than in the parental cell lines. Knocking down TYMS expression significantly reduced drug resistance in the resistant cell lines. Conversely, TYMS overexpression significantly increased drug resistance in the parental cells. Metabolomics analysis revealed that the levels of dTMP were higher in the resistant cell lines than in the parental cell lines; however, resistant cells showed no changes in dTTP levels after PMX treatment. We found that the nucleic acid-biosynthetic pathway is important for predicting the efficacy of PMX in MPM cells. The results of chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-qPCR) assays suggested that H3K27 acetylation in the 5′-UTR of TYMS may promote its expression in drug-resistant cells. Our findings indicate that the intracellular levels of dTMP are potential biomarkers for the effective treatment of patients with MPM and suggest the importance of regulatory mechanisms of TYMS expression in the disease.

One carbon metabolism in human lung cancer

Background

Lung cancer remains the major cause of cancer related death worldwide. The discovery of targeted therapies against activating mutations in genes like EGFR considerably improved the prognosis for a subgroup of patients but still leaves a large part without a targeted therapy. One carbon metabolism (1CM) has been investigated in several cancer entities and its increased activity has been linked to higher tumor aggressiveness and reduced prognosis. In spite of 1CM enzymes role and correlation to cancer cells progression, comprehensive analysis for the diagnostic and functional role of the complete 1CM enzymes in lung cancer has not been conducted so far.

Methods

We investigated the prognostic and functional relevance of five major 1CM factors (MTHFD2, PGDH3, SHMT2, MTHFD1 and TYMS) in the three major subclasses of lung cancer [pulmonary adenocarcinoma (AC), squamous cell lung cancer (SQCLC) and small cell lung cancer (SCLC)]. We analyzed 1CM enzymes expression and clinicopathological correlation in patient derived tissue samples of 103 AC, 183 SQCLC and 37 SCLC patients by immunohistochemistry. Furthermore, the effect of 1CM enzymes expression on lung cancer cell proliferation and the response to chemotherapy was investigated in 15 representative AC, SQCLC and SCLC cell lines.

Results

Expression of MTHFD2 and PGDH3 was significantly correlated to a worse overall survival only in AC patients. Cell proliferation assays resolved that all 1CM enzymes have a significant impact on cell growth in AC cell lines and are partially involved in cell proliferation in SQCLC and SCLC cell lines. In addition, expression of MTHFD2 correlated significantly with an increased pemetrexed chemoresistance.

Conclusions

Expression of MTHFD2 significantly reduces the prognosis of AC patients. Furthermore, MTHFD2 expression is crucial for survival of AC cell lines and its expression correlates with resistance against Pemetrexed. As MTHFD2 is almost not expressed in healthy adult tissue, we therefore suggest that the inhibition of MTHFD2 might be a potential therapeutic strategy to surround pemetrexed resistance in AC.

Super-enhancers: a new frontier for epigenetic modifiers in cancer chemoresistance

Although new developments of surgery, chemotherapy, radiotherapy, and immunotherapy treatments for cancer have improved patient survival, the emergence of chemoresistance in cancer has significant impacts on treatment effects. The development of chemoresistance involves several polygenic, progressive mechanisms at the molecular and cellular levels, as well as both genetic and epigenetic heterogeneities. Chemotherapeutics induce epigenetic reprogramming in cancer cells, converting a transient transcriptional state into a stably resistant one. Super-enhancers (SEs) are central to the maintenance of identity of cancer cells and promote SE-driven-oncogenic transcriptions to which cancer cells become highly addicted. This dependence on SE-driven transcription to maintain chemoresistance offers an Achilles' heel for chemoresistance. Indeed, the inhibition of SE components dampens oncogenic transcription and inhibits tumor growth to ultimately achieve combined sensitization and reverse the effects of drug resistance. No reviews have been published on SE-related mechanisms in the cancer chemoresistance. In this review, we investigated the structure, function, and regulation of chemoresistance-related SEs and their contributions to the chemotherapy via regulation of the formation of cancer stem cells, cellular plasticity, the microenvironment, genes associated with chemoresistance, noncoding RNAs, and tumor immunity. The discovery of these mechanisms may aid in the development of new drugs to improve the sensitivity and specificity of cancer cells to chemotherapy drugs.

Anti-Tumor Effects of a Penetratin Peptide Targeting Transcription of E2F-1, 2 and 3a Is Enhanced When Used in Combination with Pemetrexed or Cisplatin

Simple Summary

The E2F family of transcription factors are essential for cell proliferation, differentiation, and DNA repair. They are commonly overexpressed or dysregulated in cancer as a consequence of inactivation or mutations in the retinoblastoma protein. Therefore, one or more of the activating E2Fs (E2F-1, 2, and 3a) have been recognized as antitumor targets. The combination of a peptide targeting transcription of E2F-1, 2, and 3a, with cisplatin, and especially with pemetrexed, showed enhanced antitumor activity in-vitro and in-vivo and has promise for the treatment of patients with various tumors, and in particular, lung adenocarcinoma.

Abstract

Background: We tested the antitumor effects of a modified E2F peptide substituting D-Arg for L-Arg, conjugated to penetratin (PEP) against solid tumor cell lines and the CCRF-leukemia cell line, alone and in combination with pemetrexed or with cisplatin. For in-vivo studies, the peptide was encapsulated in PEGylated liposomes (PL-PEP) to increase half-life and stability. Methods: Prostate cancer (DU145 and PC3), breast cancer (MCF7, MDA-MB-468, and 4T1), lymphoma (CCRF-CEM), and non-small cell lung cancer (NSCLC) cell lines (H2009, H441, H1975, and H2228) were treated with D-Arg PEP in combination with cisplatin or pemetrexed. Western blot analysis was performed on the NSCLC for E2F-1, pRb, thymidylate synthase, and thymidine kinase. The H2009 cell line was selected for an in-vivo study. Results: When the PEP was combined with cisplatin and tested against solid tumor cell lines and the CCRF-CEM leukemia cell line, there was a modest synergistic effect. A marked synergistic effect was seen when the combination of pemetrexed and the PEP was tested against the adenocarcinoma lung cancer cell lines. The addition of the PEP to pemetrexed enhanced the antitumor effects of pemetrexed in a xenograft of the H2009 in mice. Conclusions: The D-Arg PEP in combination with cisplatin caused synergistic cell kill against prostate, breast, lung cancers, and the CCRF-CEM cell line. Marked synergy resulted when the D-Arg PEP was used in combination with pemetrexed against the lung adenocarcinoma cell lines. A xenograft study using the PL-PEP in combination with pemetrexed showed enhanced anti-tumor effects compared to each drug alone.

Detecting TYMS Tandem Repeat Polymorphism by the PSSD Method Based on Next-generation Sequencing

Background:

Thymidylate Synthase (TS) is an important target for folic acid inhibitors such as pemetrexed, which has considerable effects on the first-line treatment, second-line treatment and maintenance therapy for patients with late-stage Non-Small Cell Lung Cancer (NSCLC). Therefore, detecting mutations in the TYMS gene encoding TS is critical in clinical applications. With the development of Next-Generation Sequencing (NGS) technology, the accuracy of TYMS mutation detection is getting higher and higher. However, traditional methods suffer from false positives and false-negatives caused by factors like limited sequencing read length and sequencing errors.

Objective:

A method was needed to overcome the short sequencing read length and sequencing errors of NGS to make the detection of TYMS more accurate.

Methods:

In this study, we developed a novel method based on "Paired Seed Sequence Distance” (PSSD) to detect the Variable Number of Tandem Repeat (VNTR) mutation for TYMS.

Results:

With the 121 samples validated by sanger, the consistency rate of PSSD method was 85.95% (104/121), higher than the strict matching method (78.51% (95/121)). The consistency rate of the two methods was 89.26% (108/121). We also found that the PSSD method was significantly better than the strict matching method, especially in the 4R typing.

Conclusion:

Our method not only improves the detection rate and accuracy of TYMS VNTR mutations but also avoids problems caused by sequencing errors and limited sequencing length. This method provides a new solution for similar polymorphism analyses and other sequencing analyses.

Capsaicin Acts Through Reducing P38 MAPK-Dependent Thymidylate Synthase Expression to Enhance 5-Fluorouracil-Induced Cytotoxicity in Human Lung Cancer Cells

Capsaicin, an ingredient of green and red bell peppers, shows anticancer activity in several malignant cell lines. Thymidylate synthase (TS) is a well-validated anticancer drug target in non-small cell lung cancer (NSCLC) cells. However, whether capsaicin and 5-fluorouracil (5-FU) induce synergistic cytotoxicity in NSCLC cells by regulating TS expression is unclear. This study investigated the cytotoxicity of capsaicin and 5-FU co-treatment on two hoursuman lung adenocarcinoma cell lines, H520 and H1703, and the underlying mechanisms. Capsaicin decreased TS expression in a p38 mitogen-activated protein kinase (MAPK) inactivation–dependent manner in H520 and H1703 cells. Enhancement of p38 MAPK activity by transfection with constitutive active mitogen-activated protein kinase kinase six vectors increased TS expression and cell survival. In addition, capsaicin and 5-FU co-treatment enhanced synergistic cytotoxicity and inhibited cell growth associated with TS downregulation and p38 MAPK inactivation in H520 and H1703 cells. Capsaicin and 5-FU co-treatment did not affect the cellular content of capsaicin. These results show that capsaicin may be combined with 5-FU to treat NSCLC.

A Novel Prognostic Model of Early-Stage Lung Adenocarcinoma Integrating Methylation and Immune Biomarkers

Lung adenocarcinoma (LUAD) is caused by multiple biological factors. Therefore, it will be more meaningful to study the prognosis from the perspective of omics integration. Given the significance of epigenetic modification and immunity in tumorigenesis and development, we tried to combine aberrant methylation and tumor infiltration CD8 T cell-related genes to build a prognostic model, to explore the key biomarkers of early-stage LUAD. On the basis of RNA-seq and methylation microarray data downloaded from The Cancer Genome Atlas (TCGA), differentially expressed genes and aberrant methylated genes were calculated with "DEseq2" and "ChAMP" packages, respectively. A Chi-square test was performed to obtain methylation driver genes. Weighted correlation network analysis (WGCNA) was utilized to mine cancer biomarkers related to CD8 T cells. With the consequences of univariate Cox proportional hazards analysis and least absolute shrinkage and selection operator (LASSO) COX regression analysis, the prognostic index based on 17 methylation driver genes (ZNF677, FAM83A, TRIM58, CLDN6, NKD1, NFE2L3, FKBP5, ITGA5, ASCL2, SLC24A4, WNT3A, TMEM171, PTPRH, ITPKB, ITGA2, SLC6A17, and CCDC81) and four CD8 T cell-related genes (SPDL1, E2F7, TK1, and TYMS) was successfully established, which could make valuable predictions for the survival risk of patients with early-stage LUAD.

Reprogramming of Nucleotide Metabolism Mediates Synergy between Epigenetic Therapy and MAP Kinase Inhibition

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare but often lethal cancer that is diagnosed at a median age of 24 years. Optimal management of patients is not well defined, and current treatment remains challenging, necessitating the discovery of novel therapeutic approaches. The identification of SMARCA4-inactivating mutations invariably characterizing this type of cancer provided insights facilitating diagnostic and therapeutic measures against this disease. We show here that the BET inhibitor OTX015 acts in synergy with the MEK inhibitor cobimetinib to repress the proliferation of SCCOHT in vivo Notably, this synergy is also observed in some SMARCA4-expressing ovarian adenocarcinoma models intrinsically resistant to BETi. Mass spectrometry, coupled with knockdown of newly found targets such as thymidylate synthase, revealed that the repression of a panel of proteins involved in nucleotide synthesis underlies this synergy both in vitro and in vivo, resulting in reduced pools of nucleotide metabolites and subsequent cell-cycle arrest. Overall, our data indicate that dual treatment with BETi and MEKi represents a rational combination therapy against SCCOHT and potentially additional ovarian cancer subtypes.

The Promising Effects of Astaxanthin on Lung Diseases

Astaxanthin (ASX) is a naturally occurring xanthophyll carotenoid. Both in vitro and in vivo studies have shown that it is a potent antioxidant with anti-inflammatory properties. Lung cancer is the leading cause of cancer death worldwide, whereas other lung diseases such as chronic obstructive pulmonary disease, emphysema, and asthma are of high prevalence. In the past decade, mounting evidence has suggested a protective role for ASX against lung diseases. This article reviews the potential role of ASX in protecting against lung diseases, including lung cancer. It also summarizes the underlying molecular mechanisms by which ASX protects against pulmonary diseases, including regulating the nuclear factor erythroid 2-related factor/heme oxygenase-1 pathway, NF-κB signaling, mitogen-activated protein kinase signaling, Janus kinase-signal transducers and activators of transcription-3 signaling, the phosphoinositide 3-kinase/Akt pathway, and modulating immune response. Several future directions are proposed in this review. However, most in vitro and in vivo studies have used ASX at concentrations that are not achievable by humans. Also, no clinical trials have been conducted and/or reported. Thus, preclinical studies with ASX treatment within physiological concentrations as well as human studies are required to examine the health benefits of ASX with respect to lung diseases.

mRNA expression in low grade serous ovarian cancer: Results of a nanoString assay in a diverse population

OBJECTIVE

Mutations in the MAP kinase pathway (KRAS, NRAS, BRAF) are common in low grade serous ovarian carcinoma (LGSOC). The effect of these and other mutations on RNA transcription in this disease is poorly understood. Our objective was to describe patterns of somatic mutations and gene transcription in a racially diverse population with LGSOC.

METHODS

Utilizing an institutional tumor registry, patients with LGSOC were identified and charts were reviewed. RNA was extracted from available tumor tissue. Commercial tumor profiling results were analyzed with PanCancer pathway nanoString mRNA expression data. Along with nanoString n-Solver software, Chi-squared, Fishers Exact, and Cox proportional hazards models were used for statistical analysis, with significance set at p < 0.05.

RESULTS

39 patients were identified-20% Black, 43% Hispanic, and 36% non-Hispanic White. 18 patients had commercial somatic DNA test results, and 23 had available tumor tissue for RNA extraction and nanoString analysis. The most common somatic alterations identified was KRAS (11 patients, 61%), followed by ERCC1 and TUBB3 (9 each, 50%). KRAS mutations were less common in smokers (14.3% vs 90.9%, p = 0.002). RNA expression analysis demonstrated a greater than two-fold decrease in expression of HRAS in tumors from older patients (p = 0.04), and a greater than two-fold decrease in the expression of HRAS in recurrent tumors (p = 0.007). No significant differences were seen in somatic testing results, RNA expression analysis, or progression free survival between different racial and ethnic cohorts.

CONCLUSIONS

Somatic deficiencies in ERCC1, TUBB3, and KRAS are common in LGSOC in a population of minority patients. HRAS demonstrates decreased expression in tumors from older patients and recurrent tumors.

Thymidylate synthase drives the phenotypes of epithelial-to-mesenchymal transition in non-small cell lung cancer

Background

Epithelial-to-mesenchymal transition (EMT) enhances motility, stemness, chemoresistance and metastasis. Little is known about how various pathways coordinate to elicit EMT’s different functional aspects in non-small cell lung cancer (NSCLC). Thymidylate synthase (TS) has been previously correlated with EMT transcription factor ZEB1 in NSCLC and imparts resistance against anti-folate chemotherapy. In this study, we establish a functional correlation between TS, EMT, chemotherapy and metastasis and propose a network for TS mediated EMT.

Methods

Published datasets were analysed to evaluate the significance of TS in NSCLC fitness and prognosis. Promoter reporter assay was used to sort NSCLC cell lines in TS^HIGH and TS^LOW. Metastasis was assayed in a syngeneic mouse model.

Results

TS levels were prognostic and predicted chemotherapy response. Cell lines with higher TS promoter activity were more mesenchymal-like. RNA-seq identified EMT as one of the most differentially regulated pathways in connection to TS expression. EMT transcription factors HOXC6 and HMGA2 were identified as upstream regulator of TS, and AXL, SPARC and FOSL1 as downstream effectors. TS knock-down reduced the metastatic colonisation in vivo.

Conclusion

These results establish TS as a theranostic NSCLC marker integrating survival, chemo-resistance and EMT, and identifies a regulatory network that could be targeted in EMT-driven NSCLC.

Radiation-Related Deregulation of TUBB3 and BRCA1/2 and Risk of Secondary Lung Cancer in Women With Breast Cancer

INTRODUCTION

Breast cancer survivors are at increased risk of developing unrelated primary cancers, particularly lung cancer. Evidence indicates that sex hormones as well as a deregulation of DNA-repair pathways may contribute to lung cancer onset. We investigated whether the hormone status and expression of markers involved in DNA repair (BRCA1/2, ERCC1, and P53R2), synthesis (TS and RRM1), and cell division (TUBB3) might be linked to lung cancer risk.

PATIENTS AND METHODS

Thirty-seven breast cancer survivors with unrelated lung cancer and 84 control subjects comprising women with breast cancer (42/84) or lung cancer (42/84) were enrolled. Immunohistochemistry on tumor tissue was performed. Geometric mean ratio was used to assess the association of marker levels with patient groups.

RESULTS

Estrogen receptor was expressed in approximately 90% of the breast cancer group but was negative in the majority of the lung cancer group, a result similar to the lung cancer control group. Likewise, ER isoform β was weakly expressed in the lung cancer group. Protein analysis of breast cancer versus control had a significantly lower expression of BRCA1, P53R2, and TUBB3. Likewise, a BRCA1 reduction was observed in the lung cancer group concomitant with a BRCA2 increase. Furthermore, BRCA2 and TUBB3 increased in ipsilateral lung cancer in women who had previously received radiotherapy for breast cancer.

CONCLUSION

The decrease of DNA-repair proteins in breast cancer could make these women more susceptible to therapy-related cancer. The increase of BRCA2 and TUBB3 in lung cancer from patients who previously received radiotherapy for breast cancer might reflect a tissue response to exposure to ionizing radiation.

Phase II Study of Arginine Deprivation Therapy With Pegargiminase in Patients With Relapsed Sensitive or Refractory Small-cell Lung Cancer

BACKGROUND

Pre-clinical studies indicated that arginine-deprivation therapy using pegylated arginine deiminase (pegargiminase, ADI-PEG 20) may be effective in patients with argininosuccinate synthetase 1 (ASS1)-deficient small-cell lung cancer (SCLC).

PATIENTS AND METHODS

Patients were enrolled into either a 'sensitive' disease cohort (≥ 90 days response to first-line chemotherapy) or a 'refractory' disease cohort (progression while on chemotherapy or < 90 days afterwards or ≥ third-line treatment). Patients received weekly intramuscular pegargiminase, 320 IU/m² (36.8 mg/m²), until unacceptable toxicity or disease progression. The primary endpoint was tumor response assessed by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 with secondary endpoints including tolerability, pharmacodynamics, and immunogenicity.

RESULTS

Between January 2011 and January 2014, 22 patients were enrolled: 9 in the sensitive disease cohort and 13 in the refractory disease cohort. At a pre-planned interim analysis, the best overall response observed was stable disease in 2 patients in each cohort (18.2%). Owing to the lack of response and slow accrual in the sensitive disease cohort, the study was terminated early. Pegargiminase treatment was well-tolerated with no unexpected adverse events or discontinuations.

CONCLUSION

Although pegargiminase monotherapy in SCLC failed to meet its primary endpoint of RECIST-confirmed responses, more recent molecular stratification, including MYC status, may provide new opportunities moving forward.

BMI1-Mediated Pemetrexed Resistance in Non-Small Cell Lung Cancer Cells Is Associated with Increased SP1 Activation and Cancer Stemness

Lung cancer is the leading cause of cancer death worldwide and the therapeutic strategies include surgery, chemotherapy and radiation therapy. Non-small cell lung cancers (NSCLCs) account for around 85% of cases of lung cancers. Pemetrexed is an antifolate agent that is currently used as the second line chemotherapy drug in the treatment of advanced NSCLC patients with a response rate of 20–40%. The search for any combination therapy to improve the efficacy of pemetrexed is required. The existence of cancer stem cells (CSCs) is considered as the main reason for drug resistance of cancers. In this study, we first found that pemetrexed-resistant NSCLC cells derived from A549 cells displayed higher CSC activity in comparison to the parental cells. The expression of CSC related proteins, such as BMI1 or CD44, and the epithelial–mesenchymal transition (EMT) signature was elevated in pemetrexed-resistant NSCLC cells. We next discovered that the overexpression of BMI1 in A549 cells caused the pemetrexed resistance and inhibition of BMI1 by a small molecule inhibitor, PTC-209, or transducing of BMI1-specific shRNAs suppressed cell growth and the expression of thymidylate synthase (TS) in pemetrexed-resistant A549 cells. We further identified that BMI1 positively regulated SP1 expression and treatment of mithramycin A, a SP1 inhibitor, inhibited cell proliferation, as well as TS expression, of pemetrexed-resistant A549 cells. Furthermore, overexpression of BMI1 in A549 cells also caused the activation of EMT in and the enhancement of CSC activity. Finally, we demonstrated that pretreatment of PTC-209 in mice bearing pemetrexed-resistant A549 tumors sensitized them to pemetrexed treatment and the expression of Ki-67, BMI1, and SP1 expression in tumor tissues was observed to be reduced. In conclusion, BMI1 expression level mediates pemetrexed sensitivity of NSCLC cells and the inhibition of BMI1 will be an effective strategy in NSCLC patients when pemetrexed resistance has developed.

Understanding the Mechanisms by Which Epigenetic Modifiers Avert Therapy Resistance in Cancer

The development of resistance to anti-cancer therapeutics remains one of the core issues preventing the improvement of survival rates in cancer. Therapy resistance can arise in a multitude of ways, including the accumulation of epigenetic alterations in cancer cells. By remodeling DNA methylation patterns or modifying histone proteins during oncogenesis, cancer cells reorient their epigenomic landscapes in order to aggressively resist anti-cancer therapy. To combat these chemoresistant effects, epigenetic modifiers such as DNA hypomethylating agents, histone deacetylase inhibitors, histone demethylase inhibitors, along with others have been used. While these modifiers have achieved moderate success when used either alone or in combination with one another, the most positive outcomes were achieved when they were used in conjunction with conventional anti-cancer therapies. Epigenome modifying drugs have succeeded in sensitizing cancer cells to anti-cancer therapy via a variety of mechanisms: disrupting pro-survival/anti-apoptotic signaling, restoring cell cycle control and preventing DNA damage repair, suppressing immune system evasion, regulating altered metabolism, disengaging pro-survival microenvironmental interactions and increasing protein expression for targeted therapies. In this review, we explore different mechanisms by which epigenetic modifiers induce sensitivity to anti-cancer therapies and encourage the further identification of the specific genes involved with sensitization to facilitate development of clinical trials.

CD133 inhibition via autophagic degradation in pemetrexed-resistant lung cancer cells by GMI, a fungal immunomodulatory protein from Ganoderma microsporum

Background

Adaptive drug resistance is an unfavourable prognostic factor in cancer therapy. Pemetrexed-resistant lung cancer cells possess high-metastatic ability via ERK–ZEB1 pathway-activated epithelial–mesenchymal transition. GMI is a fungal immunomodulatory protein that suppresses the survival of several cancer cells.

Methods

Cell viability was analysed by MTT, clonogenic, tumour spheroid, and cancer stem cell sphere assays. Western blot assay was performed to detect the protein expression. Chemical inhibitors and ATG5 shRNA were used to inhibit autophagy. Tumour growth was investigated using xenograft mouse model.

Results

GMI decreased the viability with short- and long-term effects and induced autophagy but not apoptosis in A549/A400 cells. GMI downregulated the expression levels of CD133, CD44, NANOG and OCT4. GMI induces the protein degradation of CD133 via autophagy. CD133 silencing decreased the survival and proliferation of A549/A400 cells. GMI suppressed the growth and CD133 expression of A549/A400 xenograft tumour.

Conclusions

This study is the first to reveal the novel function of GMI in eliciting cytotoxic effect and inhibiting CD133 expression in pemetrexed-resistant lung cancer cells via autophagy. Our finding provides evidence that CD133 is a potential target for cancer therapy.

The deubiquitinating enzyme UCHL1 promotes resistance to pemetrexed in non-small cell lung cancer by upregulating thymidylate synthase

Rationale: Resistance to pemetrexed (PEM)-based chemotherapy is a major cause of progression in non-small cell lung cancer (NSCLC) patients. The deubiquitinating enzyme UCHL1 was recently found to play important roles in chemoresistance and tumor progression. However, the potential roles and mechanisms of UCHL1 in PEM resistance remain unclear.

Methods: Bioinformatics analyses and immunohistochemistry were used to evaluate UCHL1 expression in NSCLC specimens. Kaplan-Meier analysis with the log-rank test was used for survival analyses. We established PEM-resistant NSCLC cell lines by exposing them to step-wise increases in PEM concentrations, and in vitro and in vivo assays were used to explore the roles and mechanisms of UCHL1 in PEM resistance using the NSCLC cells.

Results: In chemoresistant tumors from NSCLC patients, UCHL1 was highly expressed and elevated UCHL1 expression was strongly associated with poor outcomes. Furthermore, UCHL1 expression was significantly upregulated in PEM-resistant NSCLC cells, while genetic silencing or inhibiting UCHL1 suppressed resistance to PEM and other drugs in NSCLC cells. Mechanistically, UCHL1 promoted PEM resistance in NSCLC by upregulating the expression of thymidylate synthase (TS), based on reduced TS expression after UCHL1 inhibition and re-emergence of PEM resistance upon TS restoration. Furthermore, UCHL1 upregulated TS expression, which mitigated PEM-induced DNA damage and cell cycle arrest in NSCLC cells, and also conferred resistance to PEM and other drugs.

Conclusions: It appears that UCHL1 promotes PEM resistance by upregulating TS in NSCLC cells, which mitigated DNA damage and cell cycle arrest. Thus, UCHL1 may be a therapeutic target for overcoming PEM resistance in NSCLC patients.

Dysregulated Pyrimidine Biosynthesis Contributes to 5-FU Resistance in SCLC Patient-Derived Organoids but Response to a Novel Polymeric Fluoropyrimidine, CF10

Chemo-immunotherapy is central to the treatment of small cell lung cancer (SCLC). Despite modest progress made with the addition of immunotherapy, current cytotoxic regimens display minimal survival benefit and new treatments are needed. Thymidylate synthase (TS) is a well-validated anti-cancer drug target, but conventional TS inhibitors display limited clinical efficacy in refractory or recurrent SCLC. We performed RNA-Seq analysis to identify gene expression changes in SCLC biopsy samples to provide mechanistic insight into the potential utility of targeting pyrimidine biosynthesis to treat SCLC. We identified systematic dysregulation of pyrimidine biosynthesis, including elevated TYMS expression that likely contributes to the lack of efficacy for current TS inhibitors in SCLC. We also identified E2F1-3 upregulation in SCLC as a potential driver of TYMS expression that may contribute to tumor aggressiveness. To test if TS inhibition could be a viable strategy for SCLC treatment, we developed patient-derived organoids (PDOs) from human SCLC biopsy samples and used these to evaluate both conventional fluoropyrimidine drugs (e.g., 5-fluorouracil), platinum-based drugs, and CF10, a novel fluoropyrimidine polymer with enhanced TS inhibition activity. PDOs were relatively resistant to 5-FU and while moderately sensitive to the front-line agent cisplatin, were relatively more sensitive to CF10. Our studies demonstrate dysregulated pyrimidine biosynthesis contributes to drug resistance in SCLC and indicate that a novel approach to target these pathways may improve outcomes.

A novel intraperitoneal therapy for gastric cancer with DFP-10825, a unique RNAi therapeutic targeting thymidylate synthase, in a peritoneally disseminated xenograft model

Purpose

In advanced gastric cancer, peritoneal dissemination is a life‐threatening mode of metastasis. Since the treatment options with conventional chemotherapy remain limited, any novel therapeutic strategy that could control such metastasis would improve the outcome of treatment. We recently developed a unique RNA interference therapeutic regimen (DFP‐10825) consisting of short hairpin RNA against thymidylate synthase (TS shRNA) and cationic liposomes. The treatment with DFP‐10825 has shown remarkable antitumor activity in peritoneally disseminated human ovarian cancer–bearing mice via intraperitoneal administration. In this study, we expanded DFP‐10825 to the treatment of peritoneally disseminated gastric cancer.

Methods

DFP‐10825 was administered intraperitoneally into mice with intraperitoneally implanted human gastric cancer cells (MKN45 or NCI‐N87). Antitumor activity and host survival benefits were monitored. Intraperitoneal distribution of fluorescence‐labeled DFP‐10825 was monitored in this MKN45 peritoneally disseminated mouse model.

Results

Intraperitoneal injection of DFP‐10825 suppressed tumor growth in two peritoneally disseminated cancer models (MKN45 and NCI‐N87) and increased the survival time of the MKN45 model without severe side effects. Throughout the treatment regimen, no significant body weight loss was associated with the administration of DFP‐10825. Interestingly, after intraperitoneal injection, fluorescence‐labeled DFP‐10825 retained for more than 72 hours in the peritoneal cavity and selectively accumulated in disseminated tumors.

Conclusions

Intraperitoneal injection of DFP‐10825 demonstrated effective antitumor activity without systemic severe adverse effects via the selective delivery of RNAi molecules into disseminated tumors in the peritoneal cavity. Our current study indicates that DFP‐10825 could become an alternative option to improve the outcomes of patients with peritoneally disseminated gastric cancer.

Building a Bridge between Chemotherapy and Immunotherapy in Malignant Pleural Mesothelioma: Investigating the Effect of Chemotherapy on Immune Checkpoint Expression

In light of the promising results of immune checkpoint blockade (ICPB) in malignant pleural mesothelioma (MPM), we investigated the effect of different chemotherapeutic agents on the expression of immune checkpoints (ICPs) in order to rationally design a good treatment schedule for their combination with ICP blocking antibodies. Cisplatin, oxaliplatin and pemetrexed are interesting chemotherapeutic agents to combine with immunotherapy given their immunomodulatory capacities. We looked into cisplatin and pemetrexed because their combination is used as first-line treatment of MPM. Additionally, the effect of the immunogenic chemotherapeutic agent, oxaliplatin, was also studied. Three different MPM cell lines were used for representation of both epithelioid and sarcomatoid subtypes. The desired inhibitory concentrations of the chemotherapeutic agents were determined with the SRB-assay. Allogeneic co-cultures of MPM cells with healthy donor peripheral blood mononuclear cells (PBMC) were set up to assess the effect of these chemotherapeutic agents on the expression of ICPs (PD-1, LAG-3, TIM-3) and their ligands (PD-L1, PD-L2, galectin-9). Cisplatin might be a promising treatment to combine with ICP blocking antibodies since our MPM cell lines were most susceptible to this stand-alone treatment. We found that the expression of ICPs and their ligands on both MPM cells and PBMC was mostly downregulated or unaltered when treated with chemotherapeutic agents, though no clear trend could be determined.

Successful long-term treatment of non-small cell lung cancer positive for RET rearrangement with pemetrexed

The discovery of RET rearrangement in non–small cell lung cancer (NSCLC) has prompted development of molecularly targeted therapy for such tumors, with several clinical trials being under way to evaluate the therapeutic effects of multitargeted tyrosine kinase inhibitors. The sensitivity of RET fusion–positive NSCLC to cytotoxic chemotherapy has remained unclear, however. We here report a case of NSCLC positive for the CCDC6-RET fusion gene that benefited from treatment with pemetrexed over a period of 30 months, suggesting that thymidylate synthase–targeted drugs such as pemetrexed may show efficacy for NSCLC harboring RET fusions.

Third generation EGFR inhibitor osimertinib combined with pemetrexed or cisplatin exerts long-lasting anti-tumor effect in EGFR-mutated pre-clinical models of NSCLC

BACKGROUND

The third generation Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitor (TKI) osimertinib has been initially approved for T790M positive Non-Small Cell Lung Cancer (NSCLC) and more recently for first-line treatment of EGFR-mutant T790M negative NSCLC patients. Similarly to previous generation TKIs, despite the high response rate, disease progression eventually occurs and current clinical research is focused on novel strategies to delay the emergence of osimertinib resistance. In this study we investigated the combination of osimertinib with pemetrexed or cisplatin in EGFR-mutated NSCLC cell lines and xenografts.

METHODS

Tumor growth was evaluated in a PC9T790M xenograft model and tissue composition was morphometrically determined. PC9, PC9T790M and HCC827 cell lines were employed to test the efficacy of osimertinib and chemotherapy combination in vitro. Cell viability and cell death were evaluated by MTT assay and fluorescence microscopy. Protein expression and gene status were analysed by Western blotting, fluorescence in situ hybridization analysis, next-generation sequencing and digital droplet PCR.

RESULTS

In xenograft models, osimertinib significantly inhibited tumor growth, however, as expected, in 50% of mice drug-resistance developed. A combination of osimertinib with pemetrexed or cisplatin prevented or at least delayed the onset of resistance. Interestingly, such combinations increased the fraction of fibrotic tissue and exerted a long-lasting activity after stopping therapy. In vitro studies demonstrated the stronger efficacy of the combination over the single treatments in inhibiting cell proliferation and inducing cell death in PC9T790M cells as well as in T790M negative PC9 and HCC827 cell lines, suggesting the potential role of this strategy also as first-line treatment. Finally, we demonstrated that osimertinib resistant clones, either derived from resistant tumors or generated in vitro, were less sensitive to pemetrexed prompting to use a chemotherapy regimen non-containing pemetrexed in patients after progression to osimertinib treatment.

CONCLUSIONS

Our results identify a combination between osimertinib and pemetrexed or cisplatin potentially useful in the treatment of EGFR-mutated NSCLC patients, which might delay the appearance of osimertinib resistance with long-lasting effects.

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.

Prediction of response to pemetrexed in non-small-cell lung cancer with immunohistochemical phenotyping based on gene expression profiles

Background

Palliative pemetrexed-based chemotherapy remains a standard of care treatment for the majority of patients with advanced non-squamous non-small-cell lung cancer (NSCLC). Currently, no predictive markers for pemetrexed treatment are available.

Methods

Resected tumour samples from pemetrexed-naïve NSCLC patients were collected. Gene expression profiling with respect to predicted sensitivity to pemetrexed classified predicted responders (60%) and non-responders (40%) based on differentially expressed genes encoding for pemetrexed target enzymes. Genes showing a strong correlation with these target genes were selected for measurement of corresponding protein expressions by immunohistochemical (IHC) staining. A semi-quantitative IHC scoring method was applied to construct a prediction model for response to pemetrexed. A retrospective cohort of patients with advanced NSCLC treated with first-line pemetrexed-based chemotherapy was used for external validation.

Results

From ninety-one patients resected tumour samples were collected. The majority of patients had early or locally advanced NSCLC (96.3%). Gene expression profiling revealed five markers, which mRNA levels strongly correlated to pemetrexed target genes mRNA levels: TPX2, CPA3, EZH2, MCM2 and TOP2A. Of 63 (69%) patients IHC staining scores of these markers were obtained, which significantly differed between predicted non-responders and responders (P < 0.05). The optimized prediction model included EZH2 (OR = 0.56, 95% CI 0.35–0.90) and TPX2 (OR = 0.55, 95% CI 0.30–1.01). The model had a sensitivity of 86.8%, specificity of 63.6% and showed a good ability to distinct between responders and non-responders (C-index 0.86).

In the external study population (N = 23) the majority of patients had metastatic NSCLC (95.7%). Partial response (PR) was established in 26.1%. The sensitivity decreased drastically to 33.3%, with a specificity of 82.4% and a C-index of 0.73.

Conclusions

Using external validation this prediction model with IHC staining of target enzyme correlated markers showed a good discrimination, but lacked sensitivity. The role of IHC markers as response predictors for pemetrexed in clinical practice remains questionable.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5645-x) contains supplementary material, which is available to authorized users.

Thymidylate synthase maintains the de-differentiated state of triple negative breast cancers

Cancer cells frequently boost nucleotide metabolism (NM) to support their increased proliferation, but the consequences of elevated NM on tumor de-differentiation are mostly unexplored. Here, we identified a role for thymidylate synthase (TS), a NM enzyme and established drug target, in cancer cell de-differentiation and investigated its clinical significance in breast cancer (BC). In vitro, TS knockdown increased the population of CD24⁺ differentiated cells, and attenuated migration and sphere-formation. RNA-seq profiling indicated repression of epithelial-to-mesenchymal transition (EMT) signature genes upon TS knockdown, and TS-deficient cells showed an increased ability to invade and metastasize in vivo, consistent with the occurrence of a partial EMT phenotype. Mechanistically, TS enzymatic activity was found essential for maintenance of the EMT/stem-like state by fueling a dihydropyrimidine dehydrogenase-dependent pyrimidine catabolism. In patient tissues, TS levels were found significantly higher in poorly differentiated and in triple negative BC, and strongly correlated with worse prognosis. The present study provides the rationale to study in-depth the role of NM at the crossroads of proliferation and differentiation, and depicts new avenues for the design of novel drug combinations for the treatment of BC.

FGF2-FGFR1 pathway activation together with thymidylate synthase upregulation is induced in pemetrexed-resistant lung cancer cells

Pemetrexed (MTA) is a folate antimetabolite used for treating non-small cell lung cancer. To elucidate the mechanisms of pemetrexed resistance in lung cancer, we established pemetrexed-resistant sublines in PC9 (mutant EGFR) and H1993 (wild-type EGFR) lung adenocarcinoma cell lines (PC9-MTA, H1993-MTA). Gene expression profile comparison by microarray analyses revealed enhanced fibroblast growth factor 2 (FGF2) and FGF receptor 1 (FGFR1) expression, confirmed by Western blotting, enzyme-linked immunosorbent assay, and reverse transcription-polymerase chain reaction. ERK phosphorylation was increased in PC9-MTA but decreased in H1993-MTA along with decreased downstream signaling molecule phosphorylation. Cellular morphological change from epithelial to spindle-shape together with increased mesenchymal marker protein expression was observed in H1993-MTA. SiRNA-mediated FGF2 knockdown partially restored pemetrexed sensitivity in both lines, whereas anti-FGFR1 inhibitor PD173074 restored pemetrexed sensitivity in PC9-MTA. FGF2 or FGFR1 inhibition decreased pERK levels in PC9-MTA but increased pEGFR levels together with downstream signaling molecule activation and reversed epithelial-mesenchymal transition marker protein expression in H1993-MTA. Although thymidylate synthase strongly facilitates the development of pemetrexed resistance, our results reveal involvement of the FGF2-FGFR1 pathway in pemetrexed resistance in lung cancer cells and suggest that cellular function alterations induced by FGF2-FGFR1 pathway activation depend on the innate feature of cancer cells.

Immunohistochemistry Biomarkers Predict Survival in Stage II/III Gastric Cancer Patients: From a Prospective Clinical Trial

Purpose

Identification of biomarkers to predict recurrence risk is essential to improve adjuvant treatment strategies in stage II/III gastric cancer patients. This study evaluated biomarkers for predicting survival after surgical resection.

Materials and Methods

This post-hoc analysis evaluated patients from the CLASSIC trial who underwent D2 gastrectomywith orwithout adjuvant chemotherapy (capecitabine plus oxaliplatin) at the Yonsei Cancer Center. Tumor expressions of thymidylate synthase (TS), excision repair cross-complementation group 1 (ERCC1), and programmed death-ligand 1 (PD-L1) were evaluated by immunohistochemical (IHC) staining to determine their predictive values.

Results

Among 139 patients, IHC analysis revealed high tumor expression of TS (n=22, 15.8%), ERCC1 (n=23, 16.5%), and PD-L1 (n=42, 30.2%) in the subset of patients. Among all patients, high TS expression tended to predict poor disease-free survival (DFS; hazard ratio [HR], 1.80; p=0.053), whereas PD-L1 positivity was associated with favorable DFS (HR, 0.33; p=0.001) and overall survival (OS; HR, 0.38; p=0.009) in multivariate Cox analysis. In the subgroup analysis, poor DFS was independently predicted by high TS expression (HR, 2.51; p=0.022) in the adjuvant chemotherapy subgroup (n=66). High PD-L1 expression was associated with favorable DFS (HR, 0.25; p=0.011) and OS (HR, 0.22; p=0.015) only in the surgery-alone subgroup (n=73). The prognostic impact of high ERCC1 expression was not significant in the multivariate Cox analysis.

Conclusion

This study shows that high TS expression is a predictive factor for worse outcomes on capecitabine plus oxaliplatin adjuvant chemotherapy, whereas PD-L1 expression is a favorable prognostic factor in locally advanced gastric cancer patients.

Modeling and antitumor studies of a modified L-penetratin peptide targeting E2F in lung cancer and prostate cancer

E2F1-3a overexpression due to amplification or to mutation or loss of the retinoblastoma gene, induces genes involved in DNA synthesis and leads to abnormal cellular proliferation, tumor growth, and invasion. Therefore, inhibiting the overexpression of one or more of these activating E2Fs is a recognized target in cancer therapeutics. In previous studies we identified by phage display, a novel 7-mer peptide (PEP) that bound tightly to an immobilized consensus E2F1 promoter sequence, and when conjugated to penetratin to increase its uptake into cells, was cytotoxic to several malignant cell lines and human prostate and small cell lung cancer xenografts. Based on molecular simulation studies that showed that the D-Arg penetratin peptide (D-Arg PEP) secondary structure is more stable than the L-Arg PEP, the L-Arg in the peptide was substituted with D-Arg. In vitro studies confirmed that it was more stable than the L- form and was more cytotoxic as compared to the L-Arg PEP when tested against the human castrate resistant cell line, DU145 and the human lung cancer H196 cell line. When encapsulated in PEGylated liposomes, the D-Arg-PEP potently inhibited growth of the DU145 xenograft in mice. Our findings validate D- Arg PEP, an inhibitor of E2F1and 3a transcription, as an improved second generation drug candidate for targeted molecular therapy of cancers with elevated levels of activated E2F(s).

Absence of thyroid transcription factor-1 expression is associated with poor survival in patients with advanced pulmonary adenocarcinoma treated with pemetrexed-based chemotherapy

INTRODUCTION

Adenocarcinoma is the commonest histologic subtype of lung cancer and is often identified by immunohistochemical staining for thyroid transcription factor-1 (TTF-1). However, up to 20% of lung adenocarcinomas do not express TTF-1, and there is uncertainty regarding the significance of this. We aimed to evaluate the prognostic effect of TTF-1 expression status on survival in patients treated with pemetrexed-based chemotherapy for advanced adenocarcinoma of the lung.

METHODS

This retrospective study included patients treated with pemetrexed-based chemotherapy for stage IIIB/IV lung adenocarcinoma, who had known TTF-1 expression status. Clinical and demographic data were obtained from medical records. Overall survival (OS) was estimated using the Kaplan-Meier method, and differences in survival between groups assessed using the Cox proportional hazards model.

RESULTS

Forty-four patients were identified with documented TTF-1 expression: 35 with TTF-1-positive and 9 with TTF-1-negative disease. Patients in the TTF-1-negative group had poorer performance scores than those in the TTF-1-positive group (ECOG 2: 67 vs 20%, p = 0.008), and received less chemotherapy (median cycles 2 vs 4, p = 0.009), and were fewer in treatment with doublet regimens (22 vs 69%, p = 0.013). OS was significantly shorter in the TTF-1-negative group than in the TTF-1-positive group (2.4 vs 11.5 months, HR 8.38, p < 0.0001).

CONCLUSIONS

In this group of patients treated with pemetrexed-based chemotherapy for advanced pulmonary adenocarcinoma, absence of TTF-1 expression was associated with an aggressive tumor phenotype, poorer performance status, and poor survival. This subgroup of patients should be recognized as having a distinct clinical course, with limited benefit from standard chemotherapy.

Dexamethasone alleviates pemetrexed-induced senescence in Non-Small-Cell Lung Cancer

Pemetrexed (PEM) is a novel and multi-targeted antifolate used as an antineoplastic agent for non-small cell lung cancer (NSCLC) and pleural mesothelioma. Although glucocorticoid was often used with PEM to reduce toxicity during the chemotherapy, it is not clear yet whether glucocorticoid co-administration could affect PEM efficacy in NSCLC. Here we established NSCLC cell lines and examined the effects of dexamethasone (DEX) on PEM sensitivity in vitro and in xenograft models. DEX co-administration reduced chemotherapy sensitivity to PEM in xenograft models. DEX co-administration promoted cell growth and weakened senescence growth arrest, such as altered secretions of proinflammatory and mitogenic cytokines, reminiscent of a senescence associate secretory phenotype (SASP). CSCs in DEX co-administration group were subsequently found to be less sensitive towards PEM treatment as measured by cell proliferation and generation of tumor spheres in the presence of PEM. Survival molecule B-cell lymphoma-2 (Bcl-2) may involve in this process and blockage of Bcl-2 could reverse altered senescence and CSCs abilities, thus alleviated PEM insensitivity. As such, DEX might suppress the antitumor activity of PEM through altered SASP level that had induced traits similar to CSCs.

Novel drug-resistance mechanisms of pemetrexed-treated non-small cell lung cancer

Pemetrexed (PEM) improves the overall survival of patients with advanced non-small cell lung cancer (NSCLC) when administered as maintenance therapy. However, PEM resistance often appears during the therapy. Although thymidylate synthase is known to be responsible for PEM resistance, no other mechanisms have been investigated in detail. In this study, we explored new drug resistance mechanisms of PEM-treated NSCLC using two combinations of parental and PEM-resistant NSCLC cell lines from PC-9 and A549. PEM increased the apoptosis cells in parental PC-9 and the senescent cells in parental A549. However, such changes were not observed in the respective PEM-resistant cell lines. Quantitative RT-PCR analysis revealed that, besides an increased gene expression of thymidylate synthase in PEM-resistant PC-9 cells, the solute carrier family 19 member1 (SLC19A1) gene expression was markedly decreased in PEM-resistant A549 cells. The siRNA-mediated knockdown of SLC19A1 endowed the parental cell lines with PEM resistance. Conversely, PEM-resistant PC-9 cells carrying an epidermal growth factor receptor (EGFR) mutation acquired resistance to a tyrosine kinase inhibitor erlotinib. Although erlotinib can inhibit the phosphorylation of EGFR and Erk, it is unable to suppress the phosphorylation of Akt in PEM-resistant PC-9 cells. Additionally, PEM-resistant PC-9 cells were less sensitive to the PI3K inhibitor LY294002 than parental PC-9 cells. These results indicate that SLC19A1 negatively regulates PEM resistance in NSCLC, and that EGFR-tyrosine-kinase-inhibitor resistance was acquired with PEM resistance through Akt activation in NSCLC harboring EGFR mutations.

Efficacy of Pemetrexed-based Chemotherapy in Comparison to Non-Pemetrexed-based Chemotherapy in Advanced, ALK+ Non-Small Cell Lung Cancer

PURPOSE

Previous retrospective studies suggest that anaplastic lymphoma kinase (ALK) mutation-positive (ALK+) non-small cell lung cancer (NSCLC) patients are sensitive to pemetrexed. To determine its efficacy, we retrospectively evaluated clinical outcomes of pemetrexed-based chemotherapy in patients with ALK+ NSCLC.

MATERIALS AND METHODS

We identified 126 patients with advanced, ALK+ NSCLC who received first-line cytotoxic chemotherapy. We compared response, progression-free survival (PFS), and overall survival (OS) rates according to chemotherapy regimens. Furthermore, we evaluated intracranial time to tumor progression (TTP) and proportion of ALK+ cells as prognostic factors.

RESULTS

Forty-eight patients received pemetrexed-based chemotherapy, while 78 received other regimens as first-line treatment. The pemetrexed-based chemotherapy group showed superior overall response (44.7% vs. 14.3%, p<0.001) and disease control (85.1% vs. 62.3%, p=0.008) rates. The pemetrexed-based chemotherapy group also exhibited longer PFS (6.6 months vs. 3.8 months, p<0.001); OS rates were not significantly different. The lack of exposure to second-generation ALK inhibitors and intracranial metastasis on initial diagnosis were independent negative prognostic factors of OS. Intracranial TTP was similar between the treatment groups (32.7 months vs. 35.7 months, p=0.733). Patients who harbored a greater number of ALK+ tumor cells (≥70%) showed prolonged OS on univariate analysis (not reached vs. 44.8 months, p=0.041), but not on multivariate analysis (hazard ratio: 0.19, 95% confidence interval: 0.03-1.42; p=0.106).

CONCLUSION

Pemetrexed-based regimens may prolong PFS in patients with ALK+ NSCLC as a first-line treatment, but are not associated with prolonged OS. Exposure to second-generation ALK inhibitors may improve OS rates in patients with ALK+ NSCLC.

Dasatinib modulates sensitivity to pemetrexed in malignant pleural mesothelioma cell lines

Background

Thymidylate synthase (TS), one of the key enzymes for thymidine synthesis, is a target of pemetrexed (PEM), a key agent for the systemic therapy of malignant pleural mesothelioma (MPM) and its overexpression has been correlated to PEM-resistance. In MPM, experimental data report activation of the c-SRC tyrosine kinase suggesting it as a potential target to be further investigated.

Results

MPM cell lines showed different sensitivity, being MSTO the most and REN the least sensitive to PEM. REN cells showed high levels of both TS and SRC: dasatinib inhibited SRC activation and suppressed TS protein expression, starting from 100 nM dose, blocking the PEM-induced up regulation of TS protein levels. Dasatinib treatment impaired cells migration, and both sequential and co-administration with PEM significantly increased apoptosis. Dasatinib pretreatment improved sensitivity to PEM, downregulated TS promoter activity and, in association with PEM, modulated the downstream PI3K-Akt-mTOR signaling.

Cell lines and Methods

In three MPM cell lines (MPP89, REN and MSTO), the effects of c-SRC inhibition, in correlation with TS expression and PEM sensitivity, were evaluated. PEM and dasatinib, a SRC inhibitor, were administered as single agents, in combination or sequentially. Cell viability, apoptosis and migration, as well as TS expression and SRC activation have been assessed.

Conclusions

These data indicate that dasatinib sensitizes mesothelioma cells to PEM through TS down-regulation.