RAD001 shows activity against gastric cancer cells and overcomes 5-FU resistance by downregulating thymidylate synthase

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.

circEXOC6B interacting with RRAGB, an mTORC1 activator, inhibits the progression of colorectal cancer by antagonizing the HIF1A-RRAGB-mTORC1 positive feedback loop

Background

In recent years, an increasing number of studies have indicated that circular RNA plays crucial roles in regulating tumor development and chemoresistance. Using two high-throughput RNA sequence datasets, we previously found that circEXOC6B was downregulated in colon cancer. However, its role and mechanism in colorectal cancer (CRC) remained unknown.

Methods

Real-time quantitative PCR was used to examine the expression of circEXOC6B in CRC tissues. In vivo and in vitro functional experiments were performed to determine the suppressor role of circEXOC6B in CRC progression. RNA pull-down, mass spectrometry, RNA-binding protein immunoprecipitation, co-immunoprecipitation, fluorescence in situ hybridization, and immunofluorescence were applied to investigate the possible mechanisms connecting circEXOC6B to CRC growth and 5-fluorouracil-induced apoptosis. Chromatin immunoprecipitation, dual-luciferase assay, western blot, and immunohistochemistry were used to explore the mechanisms underlying the HIF1A regulation of RRAGB transcription.

Results

circEXOC6B was downregulated in CRC tissues, and its lower expression was associated with poor prognosis of patients. Functional experiments showed that circEXOC6B inhibited growth and increased the 5-fluorouracil-induced apoptosis of CRC cells in vitro and in vivo. Mechanistically, circEXOC6B inhibited the heterodimer formation of RRAGB by binding to it, thereby suppressing the mTORC1 pathway and HIF1A level. In addition, HIF1A upregulated the transcription of RRAGB by binding to its promoter region. Altogether, the results demonstrated that a HIF1A-RRAGB-mTORC1 positive feedback loop drives tumor progression in CRC, which could be interrupted by circEXOC6B.

Conclusions

circEXOC6B inhibits the progression of CRC and enhances the chemosensitivity of CRC cells to 5-fluorouracil by antagonizing the HIF1A-RRAGB-mTORC1 positive feedback loop. circEXOC6B is a possible therapeutic target for CRC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01600-1.

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.

Disruption of mitochondrial homeostasis with artemisinin unravels anti-angiogenesis effects via auto-paracrine mechanisms

Rationale: Tumor angiogenesis promotes tumor development, progression, growth, and metastasis. Metronomic chemotherapy involves the frequent administration of low-dose chemotherapeutic agents to block angiogenic activity and reduce side effects.

Methods: MDA-MB-231 cells were treated with various concentrations of artemisinin (ART) and vinorelbine (NVB) and the cytotoxic effects of ART/NVB were determined using the CCK-8 assay. Mitochondrial reactive oxygen species (ROS) levels, mitochondrial membrane potential (∆Ψm) and mass were assessed using MitoSOX, TMRE and MitoTracker green staining. Western blot analysis was used to quantify the expression of autophagy-related proteins. Herein, by using bioinformatics analysis and experimental verification, we identified CREB as a master in MDA-MB-231 cells.

Results: We found that artemisinin (ART), which exhibits anti-angiogenic and anti-cancer effects via mitochondrial regulation, synergized with vinorelbine (NVB) to inhibit MDA-MB-231 cell proliferation. ART and NVB cooperated to regulate mitochondrial biogenesis. CREB acted as a crucial regulator of PGC1α and VEGF, which played critical roles in NVB-dependent growth factor depletion. Moreover, CREB suppression significantly reversed mitochondrial dysfunction following ART/NVB co-treatment. In addition, combination treatment with ART and NVB significantly suppressed tumor growth in a nude mouse xenograft model, with downregulated CREB and PGC1α expression levels observed in tumor biopsies, in agreement with our in vitro and ex vivo data.

Conclusions: These findings support the hypothesis that ART affects cancer and endothelial cells by targeting the auto-paracrine effects of VEGF to suppress mitochondrial biogenesis, angiogenesis, and migration between cancer cells and endothelial cells.

An acellular tissue matrix-based drug carriers with dual chemo-agents for colon cancer growth suppression

BACKGROUND/AIMS

Relapse, metastasis, and chemo-resistance are the main factors responsible for the failure of surgical treatment of malignant tumors, and typically are the main obstacles to effective cancer treatment. Although significant advances have been made in the field of cancer chemotherapy, many patients still receive inadequate treatment due to the severe adverse effects of these drugs, resulting in an inability to reach therapeutic concentrations at the tumor site with systemic chemotherapy. Thus, a biological patch loaded with chemotherapeutic drugs could be an ideal strategy for the treatment of cancer at the tumor site.

METHODS

We developed an acellular matrix using the submucosa of porcine jejunum, then loaded this matrix with different amounts of 5-fluorouracil (5-FU) and rapamycin nanoparticles. Cell proliferation and apoptosis were analyzed by flow cytometry and related markers were evaluated using real-time PCR and western blotting. The patches were evaluated in vitro to characterize their release kinetics and therapeutic feasibility. We then analyzed the therapeutic efficacy and systemic toxicity of these patches in vivo by using them in a mouse model of colon cancer.

RESULTS

The patches delivered 5-FU and rapamycin in a controlled manner for more than 8 weeks, arrested the cell cycle of LoVo cells and sw480 cells at G2/M phase, and induced apoptosis in vitro. The patches also suppressed the growth of xenografted tumors in vivo with lower adverse effects than typically observed with systemic administration of these drugs.

CONCLUSION

We demonstrated that patches loaded with 5-FU-RAPA-PLA-NP significantly inhibited the growth of colon cancer in vitro and in vivo. These results demonstrated the feasibility of the use of a multi-effect biological patch for cancer treatment.

Thymidine phosphorylase: the unforeseen driver in colorectal cancer treatment?

5-Fluorouracil- and leucovorin-based chemotherapy regimens are the backbone of colorectal cancer treatment. The addition of oxaliplatin, irinotecan and monoclonal antibodies to this backbone has largely improved clinical outcomes, but has also led to new questions, with conflicting data frequently reported in studies. Thymidine phosphorylase (TP) is a nucleoside-metabolizing enzyme involved in 5-fluorouracil pharmacokinetics, as well as inflammatory responses, neoangiogenesis and apoptosis. TP expression is regulated by hypoxia, inflammatory cytokines and antitumoral agents. We hypothesize that TP could be the unforeseen driver in the conflicting data observed with different regimens commonly used in colorectal cancer treatment. Greater comprehension of the role of this enzyme in tumor progression and pyrimidine metabolism may lead to more accurate, patient-tailored therapy.

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.

Targeting the Phosphatidylinositol-3-kinase Pathway in Gastric Cancer: Can Omics Improve Outcomes?

Phosphatidylinositol-3-kinase (PI3K) pathway signaling is an established oncogenic signal transduction pathway implicated in multiple malignancies. Therapeutic targeting of PI3K pathway components has improved outcomes in chronic lymphocytic leukemia, kidney cancer, breast cancer, and neuroendocrine tumors. Gastric cancers harbor some of the highest rates of oncogenic alterations in PI3K but attempts to translate this genomic observation have met with limited clinical success and novel approaches are needed. In the following review we discuss PI3K signaling, previous preclinical and clinical investigations in gastric cancer, and discuss future strategies aimed at overcoming resistance and improving efficacy. Identification and refinement of molecular tumor subtypes, development of predictive biomarkers along, and rational drug combination strategies are key to capitalizing on the therapeutic potential of PI3K pathway directed therapies in gastric cancers.

To Excavate Biomarkers Predictive of the Response for Capecitabine plus RAD001 through Nanostring-Based Multigene Assay in Advanced Gastric Cancer Patients

Comprehensive characterization of individual patients' tumour is important to realize personalized medicine. Here, we investigate to identify subsets that benefit from capecitabine plus RAD001 in advanced gastric cancer (GC) patients by comprehensive high-throughput genomic analysis (nCounter assay). Archival tumour tissue blocks, if possible, were collected at phase II trial of capecitabine plus RAD001 in 47 refractory GC patients (at clinicaltrials.gov NCT#01099527). A total of 42 formalin-fixed, paraffin-embedded (FFPE) tumour samples were available for nanostring based-multigene Assay. An nCounter assay of 519 kinase panels has been used. We performed correlation analyses between expression levels of kinase genes and response for capecitabine plus RAD001. Among 42 patients with An nCounter assay of 519 kinase panels, 4 patients achieved confirmed partial response and 15 patients revealed stable disease, resulting in an overall response rate (ORR) of 9.5%. No difference in ORR was observed in terms of gender, performance status, primary tumour site, gastric resection, histologic subtype, Lauren classification, No. of metastatic site and No. of chemotherapy. In subgroups with response for capecitabine plus RAD001, there is significant overexpression of 6 genes among 519 kinase gene such as EPHA2 (P = 0.0025), PIM1 (P = 0.0031), KSR1 (P = 0.0033), and EIF2AK4 (P = 0.0046) that are related to the activation of mTOR signalling. This study is first report that investigated to identify biomarkers predictive of the response for RAD001 containing treatment in refractory GC patients, by comprehensive high-throughput genomic analysis (nCounter assay).

Reduced BCL2 and CCND1 mRNA expression in human cervical cancer HeLa cells treated with a combination of everolimus and paclitaxel

Aim of the study

Cervical cancer is the second most common malignancy in women worldwide. Everolimus displays direct effects on growth and proliferation of cancer cells via inhibition of mammalian target of rapamycin (mTOR) protein, which is known to be associated with drug resistance. In this study, we aimed to investigate the effects of everolimus, gemcitabine, and paclitaxel in terms of cell viability and mRNA expression levels of GRP78, CCND1, CASP2, and BCL2 genes.

Material and methods

HeLa cells were treated with different doses of everolimus, gemcitabine, and paclitaxel. Cell viability was assessed using MTT assay, and obtained dose response curves were used for the calculations of inhibitory concentration (IC) values. At the end of the treatment times with selected doses, RNA isolation and cDNA synthesis were performed. Finally, GRP78, CCND1, CASP2, and BCL2 genes mRNA expression levels were analysed using quantitative PCR.

Results

The IC50 value of everolimus was 0.9 µM for 24-hour treatment. Moreover, the IC50 value of gemcitabine and paclitaxel was found to be around 18.1 µM and 7.08 µM, respectively. Everolimus, gemcitabine, and paclitaxel treatments alone did not change the GRP78, CCND1, BCL2 and CASP2 mRNA expression levels significantly. However, combined treatment of everolimus and paclitaxel significantly reduced BCL2 and CCND1 mRNA expression (p < 0.05). In contrast, this combination did not change GRP78 and CASP2 mRNA expression levels (p > 0.05).

Conclusions

Down-regulation of CCND1 and BCL2 expression may be an important mechanism by which everolimus increases the therapeutic window of paclitaxel in cervical cancers.

B7-H3 increases thymidylate synthase expression via the PI3k-Akt pathway

B7-H3, a member of the B7 family, has been reported to be highly expressed in colorectal cancer and is associated with poor prognosis and overall survival. In this study, we found that overexpression of B7-H3 protected SW80 and HCT8 cells from 5-fluorouracil (5-FU) using CCK-8 assays by inducing resistance to 5-FU chemotherapy. Further investigation has revealed elevated expression of thymidylate synthase (TS) and upregulation of the PI3-kinase (PI3K)/Akt pathway in B7-H3 overexpressing cells. The effects of B7-H3 on activation of the PI3K/Akt pathway and elevation of TS expression could be blocked by LY294002, a specific inhibitor of the PI3K signaling pathway. These results implied that B7-H3 can induce colorectal cancer cell resistance to 5-FU by increasing TS expression and PI3K/Akt/TS signaling and plays an important role during these processes. This study provides more proof concerning the non-immunology effect of B7 molecules, a reminder that both co-stimulatory or inhibitory effects and non-immunology effects should be devoted equal attention.

The preclinical evaluation of the dual mTORC1/2 inhibitor INK-128 as a potential anti-colorectal cancer agent

The colorectal cancer is the leading contributor of cancer-related mortality. Mammalian target of rapamycin (mTOR), existing in 2 complexes (mTORC1/2), is frequently dysregulated and constitutively activated in colorectal cancers. It represents an important drug target. Here we found that INK-128, the novel ATP-competitive kinase inhibitor of mTOR, blocked both mTORC1 and mTORC2 activation in colorectal cancer cells (both primary and transformed cells). The immunoprecipitation results showed that the assembly of mTORC1 (mTOR-Raptor association) and mTORC2 (mTOR-Rictor-Sin1 association) was also disrupted by INK-128. INK-128 inhibited colorectal cancer cell growth and survival, and induced both apoptotic and non-apoptotic cancer cell death. Further, INK-128 showed no effect on Erk/MAPK activation, while MEK/Erk inhibition by MEK-162 enhanced INK-128-induced cytotoxicity in colorectal cancer cells. Meanwhile, INK-128 downregulated Fascin1 (FSCN1)/E-Cadherin expressions and inhibited HT-29 cell in vitro migration. In vivo, daily INK-128 oral administration inhibited HT-29 xenograft growth in mice, which was further enhanced by MEK-162 administration. Finally, we found that INK-128 sensitized 5-fluorouracil-(5-FU)-mediated anti-HT-29 activity in vivo and in vitro. Thus, our preclinical studies strongly suggest that INK-128 might be investigated for colorectal cancer treatment in clinical trials.

Inside the biochemical pathways of thymidylate synthase perturbed by anticancer drugs: Novel strategies to overcome cancer chemoresistance

Our current understanding of the mechanisms of action of antitumor agents and the precise mechanisms underlying drug resistance is that these two processes are directly linked. Moreover, it is often possible to delineate chemoresistance mechanisms based on the specific mechanism of action of a given anticancer drug. A more holistic approach to the chemoresistance problem suggests that entire metabolic pathways, rather than single enzyme targets may better explain and educate us about the complexity of the cellular responses upon cytotoxic drug administration. Drugs, which target thymidylate synthase and folate-dependent enzymes, represent an important therapeutic arm in the treatment of various human malignancies. However, prolonged patient treatment often provokes drug resistance phenomena that render the chemotherapeutic treatment highly ineffective. Hence, strategies to overcome drug resistance are primarily designed to achieve either enhanced intracellular drug accumulation, to avoid the upregulation of folate-dependent enzymes, and to circumvent the impairment of DNA repair enzymes which are also responsible for cross-resistance to various anticancer drugs. The current clinical practice based on drug combination therapeutic regimens represents the most effective approach to counteract drug resistance. In the current paper, we review the molecular aspects of the activity of TS-targeting drugs and describe how such mechanisms are related to the emergence of clinical drug resistance. We also discuss the current possibilities to overcome drug resistance by using a molecular mechanistic approach based on medicinal chemistry methods focusing on rational structural modifications of novel antitumor agents. This paper also focuses on the importance of the modulation of metabolic pathways upon drug administration, their analysis and the assessment of their putative roles in the networks involved using a meta-analysis approach. The present review describes the main pathways that are modulated by TS-targeting anticancer drugs starting from the description of the normal functioning of the folate metabolic pathway, through the protein modulation occurring upon drug delivery to cultured tumor cells as well as cancer patients, finally describing how the pathways are modulated by drug resistance development. The data collected are then analyzed using network/netwire connecting methods in order to provide a wider view of the pathways involved and of the importance of such information in identifying additional proteins that could serve as novel druggable targets for efficacious cancer therapy.

Advancing pharmacological treatment options for advanced gastric cancer

INTRODUCTION

Gastric cancer is the third most common cause of cancer-related deaths worldwide. Improvement of conventional chemotherapy has been modest in the past decades.

AREAS COVERED

We review recent important studies of metastatic or recurrent gastric cancer. For human epidermal growth factor receptors 2 (HER2) negative cancer, standard treatments are combinations of fluoropyrimidine and platinum with or without epirubicin or docetaxel in first-line therapy. Controversy exists regarding the use of triplet chemotherapies due to their toxicity. For HER2 positive cancer, standard treatments are combinations of fluoropyrimidine and cisplatin with trastuzumab. As second- or third-line treatment, taxanes or irinotecan prolonged survival compared with best supportive care alone, but the extension of overall survival was only 1 - 2 months. A recent study demonstrated that ramucirumab plus paclitaxel improved survival as a second-line therapy.

EXPERT OPINION

Most trials have failed to demonstrate a benefit of targeted agents. It is important to identify predictive biomarkers to enrich an appropriate patient population for targeted agents such as HER2 status for trastuzumab.

Gossypol sensitizes the antitumor activity of 5-FU through down-regulation of thymidylate synthase in human colon carcinoma cells

PURPOSE

5-Fluorouracil (5-FU) is the basic chemotherapeutic agent used to treat colon cancer. However, the sensitivity of colon cancer cells to 5-FU is limited. Gossypol is a polyphenolic extract of cottonseeds. The purpose of this study was to investigate the activities and related mechanism of gossypol alone or in combination with 5-FU against human colon carcinoma cells.

METHODS

The IC50 of gossypol or/and 5-FU in vitro was tested by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and the drug interaction was analyzed using the CalcuSyn method. Cell apoptosis was determined using presidium iodide staining and flow cytometric analysis. Western blotting was used to determine the expression of proteins. Transient transfection method was used to silence protein.

RESULTS

The IC₅₀ at 48 h of gossypol in colon cancer cells was 26.11 ± 1.04 μmol/L in HT-29 cells, 14.11 ± 1.08 μmol/L in HCT116 cells, and 21.83 ± 1.05 μmol/L in RKO cells. When gossypol was combined with 5-FU, a synergistic cytotoxic effect was observed in HT-29 cells, HCT116 cells, and RKO cells compared with treatment with gossypol or 5-FU alone. The Western blotting results indicated that gossypol down-regulated thymidylate synthase (TS) rather than thymidine phosphorylase protein expression. Furthermore, the mTOR/p70S6K1 signaling pathway was inhibited in gossypol-treated colon cancer cells, and consequently, cyclin D1 expression was decreased, suggesting an additional mechanism of the observed antiproliferative synergistic interactions. All the observation was confirmed by silencing TS and inactivating the mTOR/p70S6K1 signaling pathway by rapamycin, both of which increased the chemo-sensitizing efficacy of 5-FU.

CONCLUSIONS

These findings suggest that gossypol-mediated down-regulation of TS, cyclin D1, and the mTOR/p70S6K1 signaling pathways enhances the anti-tumor effect of 5-FU. Ultimately, our data exposed a new action for gossypol as an enhancer of 5-FU-induced cell growth suppression.

Rapamycin downregulates thymidylate synthase and potentiates the activity of pemetrexed in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) accounts for 80-85% of lung cancer cases, and almost half of newly diagnosed patients have metastatic disease. Pemetrexed is a widely used drug for NSCLC and inhibits several folate-dependent enzymes including thymidylate synthase (TS). Increased expression of TS confers resistance to pemetrexed in vitro and predicts poor response to pemetrexed. Rapamycin is an mTOR inhibitor and suppresses cap-dependent synthesis of specific mRNA species. Here, we show that the combination of rapamycin and pemetrexed synergistically inhibits proliferation of NSCLC cells. Although pemetrexed as a single agent induced TS, pretreatment with rapamycin suppressed pemetrexed-induced TS expression. In vivo, the combination of rapamycin and pemetrexed inhibited growth of NSCLC xenografts, which correlated with decreased mTOR activity and suppression of pemetrexed-induced TS expression. The ability of rapamycin to enhance the efficacy of pemetrexed and prevent TS expression has implications for the design of Phase I and/or Phase II NSCLC clinical trials with mTOR inhibitors in combination with pemetrexed.

Glutaminolysis and carcinogenesis of oral squamous cell carcinoma

Glutaminolysis is a crucial factor for tumor metabolism in the carcinogenesis of several tumors but has not been clarified for oral squamous cell carcinoma (OSCC) yet. Expression of glutaminolysis-related solute carrier family 1, member 5 (SLC1A5)/neutral amino acid transporter (ASCT2), glutaminase (GLS), and glutamate dehydrogenase (GLDH) was analyzed in normal oral mucosa (n = 5), oral precursor lesions (simple hyperplasia, n = 11; squamous intraepithelial neoplasia, SIN I-III, n = 35), and OSCC specimen (n = 42) by immunohistochemistry. SLC1A5/ASCT2 and GLS were significantly overexpressed in the carcinogenesis of OSCC compared with normal tissue, while GLDH was weakly detected. Compared with SIN I-III SLC1A5/ASCT2 and GLS expression were significantly increased in OSCC. GLDH expression did not significantly differ from SIN I-III compared with OSCC. This study shows the first evidence of glutaminolysis-related SLC1A5/ASCT2, GLS, and GLDH expression in OSCC. The very weak GLDH expression indicates that glutamine metabolism is rather related to nucleotide or protein/hexosamine biosynthesis or to the function as an antioxidant (glutathione) than to energy production or generation of lactate through entering the tricarboxylic acid cycle. Overcoming glutaminolysis by targeting c-Myc oncogene (e.g. by natural compounds) and thereby cross-activation of mammalian target of rapamycin complex 1 or SLC1A5/ASCT2, GLS inhibitors may be a useful strategy to sensitize cancer cells to common OSCC cancer therapies.

Phase II multicentered study of low-dose everolimus plus cisplatin and weekly 24-hour infusion of high-dose 5-fluorouracil and leucovorin as first-line treatment for patients with advanced gastric cancer

OBJECTIVE

This phase II trial investigates the efficacy and safety of low-dose everolimus in combination with cisplatin-fluorouracil chemotherapy in patients with advanced gastric cancer.

METHODS

Eligible patients with chemotherapy-naïve advanced gastric cancer received low-dose everolimus (10 mg p.o. on days 1, 8 and 15) plus cisplatin and a weekly 24-hour infusion of high-dose 5-fluorouracil and leucovorin (HDFL) chemotherapy (cisplatin 35 mg/m(2) intravenous infusion for 24 h on days 1 and 8, 5-fluorouracil 2,000 mg/m(2) and leucovorin 300 mg/m(2) intravenous infusion for 24 h on days 1, 8 and 15) every 28 days. The primary endpoint was objective response rate (ORR) according to the Response Evaluation Criteria in Solid Tumors version 1.0.

RESULTS

Forty patients (19 men; 21 women; median age, 54.1 years; range, 33.7-73.3 years) received a median of 6 (range, 1-30; 95% CI, 4.9-8.0) cycles of study treatment. The ORR was 52.5% (21 confirmed partial response). The median progression-free survival and overall survival were 6.9 (95% CI, 4.9-8.4) and 10.5 (95% CI, 8.6-12.3) months, respectively. Most adverse events were mild.

CONCLUSION

Adding low-dose everolimus to cisplatin-HDFL chemotherapy failed to increase the ORR as in a preplanned statistical assumption but may prolong progression-free survival in treatment-naïve advanced gastric cancer patients.

ERCC1 and TS expression and prognosis in colon cancer after postoperative adjuvant chemotherapy

AIM: To explore the relationship between excision repair cross-complementing group 1 (ERCC1) expression, thymidylate synthase (TS) expression and the prognosis in colon cancer after postoperative adjuvant chemotherapy.

METHODS: Seventy-six patients who were diagnosed with colon cancer for the first time were enrolled in our study. All the patients received radical operation, were pathologically diagnosed with stage Ⅱ or Ⅲ disease, accepted FOLFOX4 (L-OHP+5-Fu+CF) chemotherapy and were followed at least 3 years. Immunohistochemistry was used to detect ERCC1 and TS expression levels in colon cancer. The relationship between the expression of ERCC1 and TS and postoperative survival was analyzed retrospectively.

RESULTS: The positive expression rates of ERCC1 and TS in colon cancer were 36.8% and 43.4%, respectively. There were a negative correlation between the positive expression of ERCC1 and TS and tumor differentiation (P = 0.019 and 0.024). The median survival time was significantly longer in patients with negative ERCC1 expression than in those with positive expression (P < 0.05), and in patients with negative TS expression than in those with positive expression (P < 0.05). Cox multivariate regression analysis revealed that patients with positive ERCC1 and TS expression did not benefit from chemotherapy (HR = 3.50, 95%CI: 1.59-7.73, P = 0.002; HR = 0.52, 95%CI: 0.35-0.87, P = 0.010).

CONCLUSION: ERCC1 and TS may be biomarkers for predicting the prognosis of colon cancer patients receiving chemotherapy.

Everolimus for previously treated advanced gastric cancer: results of the randomized, double-blind, phase III GRANITE-1 study

PURPOSE

The oral mammalian target of rapamycin inhibitor everolimus demonstrated promising efficacy in a phase II study of pretreated advanced gastric cancer. This international, double-blind, phase III study compared everolimus efficacy and safety with that of best supportive care (BSC) in previously treated advanced gastric cancer.

PATIENTS AND METHODS

Patients with advanced gastric cancer that progressed after one or two lines of systemic chemotherapy were randomly assigned to everolimus 10 mg/d (assignment schedule: 2:1) or matching placebo, both given with BSC. Randomization was stratified by previous chemotherapy lines (one v two) and region (Asia v rest of the world [ROW]). Treatment continued until disease progression or intolerable toxicity. Primary end point was overall survival (OS). Secondary end points included progression-free survival (PFS), overall response rate, and safety.

RESULTS

Six hundred fifty-six patients (median age, 62.0 years; 73.6% male) were enrolled. Median OS was 5.4 months with everolimus and 4.3 months with placebo (hazard ratio, 0.90; 95% CI, 0.75 to 1.08; P = .124). Median PFS was 1.7 months and 1.4 months in the everolimus and placebo arms, respectively (hazard ratio, 0.66; 95% CI, 0.56 to 0.78). Common grade 3/4 adverse events included anemia, decreased appetite, and fatigue. The safety profile was similar in patients enrolled in Asia versus ROW.

CONCLUSION

Compared with BSC, everolimus did not significantly improve overall survival for advanced gastric cancer that progressed after one or two lines of previous systemic chemotherapy. The safety profile observed for everolimus was consistent with that observed for everolimus in other cancers.

Phase II trial of capecitabine and everolimus (RAD001) combination in refractory gastric cancer patients

BACKGROUND

The aim of this study was to assess the efficacy and safety of combination regimen of capecitabine plus everolimus in patients with refractory gastric cancer who have failed to at least two cytotoxic regimens.

METHODS

Patients received capecitabine 650 mg/m(2) twice daily (D1-14) and everolimus 5 mg twice daily (D1-21) every 3 weeks until disease progression or unacceptable toxicity. The primary endpoint of the study was overall response (partial or complete response) and the secondary endpoints were progression-free survival (time between registration and disease progression or death) and overall survival. Pharmacokinetic analysis was also performed. Patients who have failed to at least two cytotoxic regimens were enrolled.

RESULTS

Between March 2010 and June 2012, 47 patients were enrolled. 33 patients (70.2%) had received more than three previous regimens prior to enrolment. Among 43 evaluable patients for treatment response, 5 patients achieved confirmed partial response and 18 patients showed stable disease, resulting in an overall response rate (ORR) of 10.6% (95% C.I.: 1.8-19.4%) and disease control rate of 48.9% (95% C.I.:34.6-63.2%). At a median follow-up of 106 weeks (range, 21-141 weeks), the median progression-free survival and overall survival were 11.0 weeks (95% C.I.: 5.7-16.3 weeks) and 21.0 weeks (95% C.I.: 14.3-27.7 weeks), respectively. Grade 3 nausea, diarrhea and stomatitis occurred in two, three and three patients, respectively. Elevated liver enzyme was observed in 21 patients and no patient had pulmonary fibrosis.

CONCLUSIONS

The combination of capecitabine 650 mg/m(2) twice daily and everolimus 5 mg twice daily was found to be effective in a small subset of GC patients who were heavily pre-treated.

Clinical significance of TS and BRCA1 protein overexpression in gastric cancer

AIM: To investigate the correlation between thymidylate synthase (TS) and breast cancer susceptibility gene-1 (BRCA1) expression and clinicopathological characteristics of gastric cancer.

METHODS: Two hundred and forty-six surgical specimens of gastric cancer collected from patients with complete clinical data who were treated at Fuzhou General Hospital of Nanjing Military Command between January 2011 and January 2012 were used in this study. The protein expression of TS and BRCA1 in these specimens was examined by immunohistochemistry. The correlation between TS and BRCA1 protein expression and clinicopathological characteristics of gastric cancer was analyzed.

RESULTS: The rates of TS and BRCA1 overexpression in gastric cancer were 39.02% (96/246) and 55.69% (137/246), respectively. There was no relationship between TS overexpression and sex, age, tumor site, histotype, differentiation, distant metastasis, depth of invasion, TNM stage and lymph node metastasis (all P > 0.05). BRCA1 protein overexpression was associated with depth of invasion (P < 0.01) and TNM stage (P < 0.05), but not with sex, age, tumor site, differentiation, lymph node metastasis or distant metastasis (all P > 0.05). The co-expression rate of TS and BRCA1 in gastric cancer was 26.02% (64/246). The overexpression of TS was negatively correlated with that of BRCA1 (P < 0.01, r = 0.2472).

CONCLUSION: There exists TS and BRCA1 overexpression in gastric cancer. The overexpression of BRCA1was associated with TNM stage and depth of invasion, which implies that BRCA1 overexpression may be related to invasion of gastric cancer. Detection of BRCA1 protein overexpression may be used to assess the malignant biological behavior and prognosis of gastric cancer and help choose chemotherapy drugs.

TS gene polymorphisms in gastric cancer and colorectal cancer

Gastric cancer and colorectal cancer are the most common gastrointestinal tumors worldwide. The development, metastasis and recurrence of gastric cancer and colorectal cancer are complex and are affected and regulated by many factors. These factors have important significance in guiding treatment and predicting prognosis. Recent studies have shown that thymidylic acid synthase (TS) is closely related with the occurrence, chemotherapy and prognosis of gastric cancer and colorectal cancer; however, there is still some controversy over this view. This review discusses the relationship between TS gene polymorphisms and gastric cancer and colorectal cancer.

Novel MEK inhibitor trametinib and other retinoblastoma gene (RB)-reactivating agents enhance efficacy of 5-fluorouracil on human colon cancer cells

Chemotherapy for colorectal cancer has become more complicated and diversified with the appearance of molecular-targeting agents. 5-Fluorouracil (5-FU) has been a mainstay of chemotherapy for colorectal cancer, but it is still unknown whether the combining of 5-FU with novel molecular-targeting agents is effective. Thymidylate synthase (TS) is a direct target of 5-FU, and the low TS level has been generally supposed to sensitize 5-FU's efficacy. We therefore hypothesized that RB-reactivating agents could enhance the efficacy of 5-FU, because the RB-reactivating agents could suppress the function of transcription factor E2F of TS gene promoter. We used three RB-reactivating agents, trametinib/GSK1120212 (MEK inhibitor), fenofibrate (PPARα agonist), and LY294002 (PI3K inhibitor), with 5-FU against human colon cancer HT-29 and HCT15 cells. Trametinib induced p15 and p27 expression and reduced cyclin D1 levels in HT-29 cells. Fenofibrate also dephosphorlated ERK1/2 and reduced cyclin D1 levels in HT-29 cells. LY294002 induced p27 expression in HCT15 cells. All three agents caused dephosphorylation of RB protein and G1-phase arrest with a reduction of TS expression. As a consequence, the combination of 5-FU with each of the agents resulted in a significant decrease of colony numbers in HT-29 or HCT15 cells. These results suggest "RB-reactivation therapy" using molecular-targeting agents to be a new strategy for 5-FU-based chemotherapy. In particular, we strongly expect trametinib, which was discovered in Japan and was recently submitted to FDA for approval, to be used together with established regimens for colorectal cancer.

The novel mTOR inhibitor CCI-779 (temsirolimus) induces antiproliferative effects through inhibition of mTOR in Bel-7402 liver cancer cells

BACKGROUND

Liver cancer is one of the most frequent cancers in the world. Targeted therapy of cancer with specific inhibitors is developing and has shown promising antitumor efficacy. CCI-779 (temsirolimus), a specific inhibitor of mTOR (mammalian target of rapamycin), can block the mTOR signaling pathway. Here, we systematically examined the expression of mTOR and its downstream targets in liver cancer cells and normal liver cells, then investigated inhibitory effects of CCI-779 on mTOR signaling pathway and its role in regulating liver cancer cell growth.

METHODS

The expression of mTOR and its downstream targets in Bel-7402 liver cancer cells and HL-7702 normal liver cells were examined by western blot. The mTOR specific inhibitor (CCI-779) was used to treat Bel-7402 cells to identify its effects on Bel-7402 cell growth and activity of mTOR signaling pathway in vitro. Cell viability tests were performed after the treatment of CCI-779. Western blot was applied to assess the changes of mTOR pathway and flow cytometry was used to analyze cell cycle of Bel-7402 cells after the treatment of CCI-779.

RESULTS

mTOR, p70S6K, S6, and 4EBP1 were overexpressed in Bel-7402 cells compared with HL-7702 cells. Bel-7402 cells were sensitive to CCI-779. The survival rate of the cells treated with CCI-779 over 0.312 μM was significantly different compared with that of control (P < 0.05). CCI-779 inhibited the phosphorylation of mTOR (Ser2448), p70S6K (Thr389), S6 (Ser240/244), and 4EBP1 (Thr37/46) in different grades and the expressions of p70S6K, S6, and 4EBP1. As a result, CCI-779 induced a dose-dependent decrease in cell proliferation, G1/S arrest and damage of cell shape.

CONCLUSIONS

Taken together, these data showed that CCI-779 can inhibit mTOR signaling and proliferation in Bel-7402 liver cancer cells in vitro. It offers a therapeutic intervention through inhibition of mTOR as a potential strategy for liver cancer.

Molecular targeted therapies in advanced gastric cancer: does tumor histology matter?

It is increasingly recognized that gastric cancer is a heterogeneous disease which may be divided into subgroups based on histological, anatomical, epidemiological and molecular classifications. Distinct molecular drivers and tumor biology, and thus different treatment targets and predictive biomarkers, may be implicated in each subtype. However, there is little evidence in the literature regarding the correlation among these different classifications, and particularly the molecular aberrations present in each subtype. In this review, we approach advanced gastric cancer (AGC) by presenting aberrant molecular pathways and their potential therapeutic targets in gastric cancer according to histological and anatomical classification, dividing gastric cancer into proximal nondiffuse, distal nondiffuse and diffuse disease. Several pathways are involved predominantly, although not exclusively, in different subtypes. This may help to explain the disappointing results of many published AGC trials in which study populations were heterogeneous regardless of clinicopathological characteristics of the primary tumor. Histological and anatomical classification may provide insights into tumor biology and facilitate selection of an enriched patient population for targeted agents in future studies and in the clinic. However, some molecular pathways implicated in gastric cancer have not been studied in correlation with histological or anatomical subtypes. Further studies are necessary to confirm the suggestion that such classification may predict tumor biology and facilitate selection of an enriched patient population for targeted agents in future studies and in the clinic.

Pharmacologic synergy between dual phosphoinositide-3-kinase and mammalian target of rapamycin inhibition and 5-fluorouracil in PIK3CA mutant gastric cancer cells

Phosphoinositide-3-kinase (PI3K) and mammalian target of rapamycin (mTOR) inhibitors are an emerging class of anti-cancer agents. Here, we tested the hypothesis that the dual PI3K/mTOR inhibitor, PI103, could synergize with the chemotherapeutic agent, 5-fluorouracil (5-FU) by inhibiting E2F1, thymidylate synthase (TS) and enhancing DNA damage. Drug combination effects were assessed in gastric cancer cells using the median-effect equation. The specific effects of inhibition of E2F1 and PIK3CA were examined by siRNA, and mTOR by rapamycin exposure. Protein expression and apoptosis pre- and post-treatment was measured using standard methods. PI103 and 5-FU was synergistic in 3/5 gastric cancer cell lines tested. Synergy was associated with PI3KCA mutation, reduced TS and E2F1 protein levels, increased H2AX phosphorylation and apoptosis. E2F1 siRNA enhanced sensitivity to 5-FU only in cells displaying synergy. Excess thymidine exposure converted synergism to antagonism in all cells. Inhibition of PI3K and mTOR alone enhanced 5-FU cytotoxicity in only 2/3 cell lines that displayed synergy each. In AGS cells, PI3K inhibition alone enhanced 5-FU sensitivity as much as dual PI3K/mTOR inhibition. In HGC27 cells, dual inhibition increased 5-FU sensitivity more than single PI3K or mTOR inhibition. Combined PI103 and 5-FU treatment reduced in vivo tumor growth more than treatment with single agents. PI3K/mTOR inhibitors can enhance 5-FU cytotoxicity in vitro and in vivo, especially in PIK3CA mutant tumor cells. Dual, rather than single, PI3K/mTOR inhibitors may combine better with 5-FU due to cellular heterogeneity in sensitivity to PI3K and mTOR inhibition.

Targeted therapies for gastric cancer: current status

Gastric cancer represents one of the most common cancers internationally. Unfortunately the majority of patients still present at an advanced stage, and despite advances in diagnostic and treatment strategies, outcomes still remain poor with high mortality rates despite a decline in incidence. Whilst the utility of classical chemotherapy agents has been explored thoroughly (and continues to be investigated, alone or in various combinations), advances have been slow and the efficacy of these agents has reached a plateau. As such, the focus of recent study has shifted toward developing a greater understanding of the molecular biology of carcinogenesis and the cancer cell phenotype, and, in turn, the development of rationally designed drugs that target molecular aberrancies in signal transduction pathways specific to gastric cancer. These targets include circulating growth and angiogenic factors, cell surface receptors, and other molecules that comprise downstream intracellular signalling pathways, including receptor tyrosine kinases. Therapeutic advances in this area significantly lag behind other solid organ malignancies such as breast and colorectal cancer. This article reviews the role of targeted therapies in gastric cancer, including rationale and mechanism of action, current and emerging data, as single-agent therapy or in combination regimens. A recently published randomized phaseIII trial supporting the use of trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2)/neu monoclonal antibody, in a selected population of patients is discussed. Therapies that have been evaluated in phase II trials are also reviewed, as well as promising new therapies currently being investigated in preclinical or phase I studies. There is optimism that targeted therapies, whether as single-agent therapy or in combination with traditional therapies, including chemotherapy, radiotherapy and surgery, may yet have an impact on improvement of the overall prognosis of gastric cancer.

NVP-BKM120, a novel PI3K inhibitor, shows synergism with a STAT3 inhibitor in human gastric cancer cells harboring KRAS mutations

Aberrations of Phosphoinositide 3-kinase (PI3K)/AKT signaling are frequently observed in many types of cancer, promoting its emergence as a promising target for cancer treatment. PI3K can become activated by various pathways, one of which includes RAS. RAS can not only directly activate the PI3K/AKT pathway via binding to p110 of PI3K, but also regulates mTOR via ERK or RSK independently of the PI3K/AKT pathway. Thus, actively mutated RAS can constitutively activate PI3K signaling. Additionally, in RAS tumorigenic transformation, signal transducer and activator of transcription 3 (STAT3) has been known also to be required. In this study, we examined the efficacy of NVP-BKM120, a pan-class I PI3K inhibitor in human gastric cancer cells and hypothesized that the combined inhibition of PI3K and STAT3 would be synergistic in KRAS mutant gastric cancer cells. NVP-BKM120 demonstrated anti-proliferative activity in 11 human gastric cancer cell lines by decreasing mTOR downstream signaling. But NVP-BKM120 treatment increased p-AKT by subsequent abrogation of feedback inhibition by stabilizing insulin receptor substrate-1. In KRAS mutant gastric cancer cells, either p-ERK or p-STAT3 was also increased upon treatment of NVP-BKM120. The synergistic efficacy study demonstrated that dual PI3K and STAT3 blockade showed a synergism in cells harboring mutated KRAS by inducing apoptosis. The synergistic effect was not seen in KRAS wild-type cells. Together, these findings suggest for the first time that the dual inhibition of PI3K and STAT3 signaling may be an effective therapeutic strategy for KRAS mutant gastric cancer patients.

mTOR as a therapeutic target in patients with gastric cancer

The poor long-term outcomes associated with current chemotherapy treatment of patients with advanced gastric cancer suggest a need for novel targeted agents that may confer a better survival benefit. Evidence of mammalian target of rapamycin (mTOR) activation has been demonstrated in patient-derived gastric cancer cells and tumors. This review explores the relevance of the mTOR pathway to gastric cancer pathogenesis and its potential as a therapeutic target in patients with gastric cancer as well as presenting the first available clinical data on mTOR inhibitors in this disease setting. Preclinical data suggest that suppression of the mTOR pathway inhibited the proliferation of gastric cancer cells and delayed tumor progression in in vitro and animal models. In the clinical setting, the mTOR inhibitor everolimus has been active and well tolerated in phase I/II studies of patients with chemotherapy-refractory metastatic gastric cancer. Based on these promising results, everolimus currently is being investigated as a monotherapy or in combination with chemotherapeutic agents in ongoing phase II/III clinical studies.

Phase I and pharmacokinetic study of capecitabine and the oral mTOR inhibitor everolimus in patients with advanced solid malignancies

Background Everolimus is an oral mTOR-inhibitor. Preclinical data show synergistic effects of mTOR inhibition in combination with 5-fluorouracil-based anticancer therapy. The combination of everolimus with capecitabine seems therefore an attractive new, orally available, treatment regimen. Patients and methods Safety, preliminary efficacy and pharmacokinetics of everolimus in combination with capecitabine were investigated in patients with advanced solid malignancies. Patients were treated with fixed dose everolimus 10 mg/day continuously, plus capecitabine bid for 14 days in three-weekly cycles. Dose escalation of capecitabine proceeded according to the standard 3 × 3 phase I design in four predefined dose levels (500–1,000 mg/m² bid). Results In total, 18 patients were enrolled. Median (range) treatment duration with everolimus was 70 days (21–414). Capecitabine 1,000 mg/m² bid combined with 10 mg/day everolimus was declared the maximum tolerated dose, at which level one patient developed dose-limiting toxicity (stomatitis grade 3). Drug-related adverse events were mostly grade ≤2 and included mainly fatigue (56%), stomatitis (50%), and hand-foot syndrome (33%). Partial response was documented in three patients, and four had stable disease. There was no pharmacokinetic interaction between everolimus and capecitabine. Conclusion Everolimus 10 mg/day continuously combined with capecitabine 1,000 mg/m² bid for 14 days every 3 weeks is a patient-convenient, safe and tolerable oral treatment regimen. This is the first study to demonstrate feasibility of this combination at doses with proven single agent efficacy in a number of tumors. Prolonged clinical benefit was observed in an encouraging 39% of patients with advanced solid malignancies.