5-Fluorouracil and its active metabolite FdUMP cause DNA damage in human SW620 colon adenocarcinoma cell line

Anticancer Potential, Phenolic Profile, and Antioxidant Properties of Synsepalum dulcificum (Miracle Berry) in Colorectal Tumor Cell Lines

Polyphenols, recognized for their antioxidant capacity, have shown potential in improving the response treatment of various diseases, including cancer. In this context, polyphenols have the ability to induce cytotoxicity in tumor cells, making them possible complementary agents to current treatments. The present study aims to evaluate the effect of the aqueous extract of Synsepalum dulcificum, using the commercial product DMB®, on the proliferation of colorectal tumor cells. An aqueous extract of DMB® was obtained, and 12 compounds were identified through high-performance liquid chromatography (HPLC), with protocatechuic acid, gallic acid, and catechin being the most prominent. Regarding cytotoxicity, the extracts reduced cell viability in the DLD-1, HT29, SW480, and SW620 cell lines, with IC50 values of 7, 11, 13, and 15 mg/mL, respectively. The combination of oxaliplatin with the DMB® extract reduced the resistant population by up to 50% in the DLD-1 and SW620 cell lines, affecting the G2/M and S phases of the cell cycle, respectively. Additionally, treatment with the DMB® extract induced an increase in the expression of BCL2, CASP3, and CASP9, suggesting a mechanism of action associated with apoptosis. The aqueous extract of Synsepalum dulcificum (DMB®) exhibited cytotoxicity in colorectal cancer cells, enhancing the effect of oxaliplatin and activating apoptotic pathways, suggesting its potential as an adjuvant in anticancer therapies.

Gender effects of nanoplastics and emerging contaminants mixtures in Mytilus galloprovincialis

The reproduction of mussels occurs within the water column, and if gametogenesis is successful, gametes are exposed to the surrounding contaminants. Nanoplastics and other emerging contaminants have been gaining vast attention; however, their effects on the reproductive tissues of mussels with sex differentiation are scarce. Here, the effects of polystyrene nanoparticles (50 nm; 10 µg/L), the cytotoxic drug 5-fluorouracil (10 ng/L), and a mixture of the two were evaluated in the gonads of Mytilus galloprovincialis after a 21-day exposure for a multi-biomarker assessment, and after 28 days for the accumulation of nanoplastics. The effects on the activity of superoxide dismutase, catalase, glutathione-S-transferase, and lipid peroxidation were evaluated. Moreover, synergistic and antagonistic interactions in the mixture were calculated. A weight of evidence model was also used to elaborate on the hazardous level of biomarker results relative to polystyrene nanoparticles alone and in the mixture. The accumulation of nanoplastics appeared gender and time-specific, with females mostly compromised. According to the data set, a synergistic interaction between the cytotoxic drug and the nanoplastics makes the combination far more dangerous than individual stressors. The Weight Of Evidence model also confirms that females are more compromised at chronic exposure times than males. This study shows that the uptake, fate, and impact of emerging contaminants of concern can be significantly influenced by sex.

DNA base oxidation in relation to TNM stages and chemotherapy treatment in colorectal cancer patients 2-9 months post-surgery

Accumulation of DNA damage is a critical feature of genomic instability, which is a hallmark of various cancers. The enzyme-modified comet assay is a recognized method to detect specific DNA lesions at the level of individual cells. In this cross-sectional investigation, we explore possible links between clinicopathological and treatment related factors, nutritional status, physical activity and function, and DNA damage in a cohort of colorectal cancer (CRC) patients with non-metastatic disease. Levels of DNA damage in peripheral mononuclear blood cells (PBMCs) assessed 2-9 months post-surgery, were compared across tumour stage (localized (stage I-II) vs. regional (stage III) disease), localization (colon vs. rectosigmoid/rectum cancer), and adjuvant chemotherapy usage, with the last dosage administrated 2-191 days prior to sampling. Associations between DNA damage and indicators of nutritional status, physical activity and function were also explored. In PBMCs, DNA base oxidation was higher in patients diagnosed with regional compared with localized tumours (P = 0.03), but no difference was seen for DNA strand breaks (P > 0.05). Number of days since last chemotherapy dosage was negatively associated with DNA base oxidation (P < 0.01), and patients recently receiving chemotherapy (<15 days before blood collection) had higher levels of DNA base oxidation than those not receiving chemotherapy (P = 0.03). In the chemotherapy group, higher fat mass (in kg and %) as well as lower physical activity were associated with greater DNA base oxidation (P < 0.05). In conclusion, DNA base oxidation measured with the enzyme-modified comet assay varies according to tumour and lifestyle related factors in CRC patients treated for non-metastatic disease.

Caffeine enhances chemosensitivity to irinotecan in the treatment of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most common types of cancer. This disease arises from gene mutations and epigenetic alterations that transform colonic epithelial cells into colon adenocarcinoma cells, which display a unique gene expression pattern compared to normal cells. Specifically, CRC cells exhibit significantly higher expression levels of genes involved in DNA repair or replication, which is attributed to the accumulation of DNA breakage resulting from rapid cell cycle progression.

PURPOSE

This study aimed to investigate the in vivo effects of caffeine on CRC cells and evaluate its impact on the sensitivity of these cells to irinotecan, a topoisomerase I inhibitor widely used for CRC treatment.

METHODS

Two CRC cell lines, HCT116 and HT29, were treated with irinotecan and caffeine. Western blot analysis assessed protein expression levels in caffeine/irinotecan-treated CRC cells. Immunofluorescence staining determined protein localization, measured DNA breaks, and explored the effects of DNA damage reagents during cell cycle progression and flow cytometry analysis was used to measure cell viability. Fiber assays investigated DNA synthesis in DNA-damaged cells during S-phase, while the comet assay assessed DNA fragmentation caused by DNA breaks.

RESULTS

Our findings demonstrated that the combination of irinotecan and caffeine exhibits a synergistic effect in suppressing CRC cell proliferation and inducing cell death. Compared to treatment with only irinotecan or caffeine, the combined irinotecan and caffeine treatment was more effective in inducing DNA lesions by displacing RAD51 from DNA break sites and inhibiting DNA repair progression, leading to cell cycle arrest. This combination also resulted in more severe effects, including DNA fragmentation and mitotic catastrophe.

CONCLUSION

Caffeine could enhance the effectiveness of an existing drug for CRC treatment despite having little impact on the cell survival rate of CRC cells. Our findings suggest that the beneficial adjuvant effects of caffeine may not only be applicable to CRC but also to various other types of cancers at different stages of development.

Ecotoxicity of emerging contaminants in the reproductive organ of marine mussels Mytilus galloprovincialis

Contaminants of emerging concern (CECs) present a new threat to the marine environment, and it is vital to understand the interactions and possible toxicity of CEC mixtures once they reach the ocean. CECs-such as metal nanoparticles, nanoplastics, and pharmaceuticals-are groups of contaminants some of which have been individually evaluated, though their interactions as mixtures are still not fully understood. To ensure a healthy and prosperous future generation, successful reproduction is key: however, if hindered, population dynamics may be at danger leading to a negative impact on biodiversity. This study aimed to understand the effects of silver (20 nm nAg, 10 μg/L), polystyrene nanoparticles (50 nm nPS, 10 μg/L), and 5-fluorouracil (5FU, 10 ng/L) individually and as a mixture (10 μg/L of nPS + 10 μg/L of nAg +10 ng/L of 5FU) in the gonads of Mytilus galloprovincialis. A multibiomarker approach, namely the antioxidant defence system (ADS; superoxide dismutase, catalase, glutathione peroxidases, glutathione - S - transferases activities), and oxidative damage (OD; lipid peroxidation) were analysed in the gonads of mussels. All exposure treatments after 3 days led to an increase of enzymatic activity, followed by an inhibition after 14 and 21 days. Thus, ADS was overwhelmed due to the generation of ROS, resulting in OD, except for nPS exposed mussels. The OD in Mix exposed mussels increased exponentially by 57-fold. When CEC mixtures interact, they are potentially more hazardous than their individual components, posing a major threat to marine species. To understand synergistic and antagonistic interactions, a model was applied, and antagonistic interactions were observed in evaluated biomarkers at all time-points, apart from a synergistic interaction at day 3 relative to LPO. Results indicate that the effects observed in Mix-exposed mussel gonads are mainly due to the interaction of nAg and 5FU but not nPS.

Review of 5-FU resistance mechanisms in colorectal cancer: clinical significance of attenuated on-target effects

The emergence of chemoresistant disease during chemotherapy with 5-Fluorouracil-based (5-FU-based) regimens is an important factor in the mortality of metastatic CRC (mCRC). The causes of 5-FU resistance are multi-factorial, and besides DNA mismatch repair deficiency (MMR-D), there are no widely accepted criteria for determining which CRC patients are not likely to be responsive to 5-FU-based therapy. Thus, there is a need to systematically understand the mechanistic basis for 5-FU treatment failure and an urgent need to develop new approaches for circumventing the major causes of 5-FU resistance. In this manuscript, we review mechanisms of 5-FU resistance with an emphasis on: (1) altered anabolic metabolism limiting the formation of the primary active metabolite Fluorodeoxyuridylate (5-Fluoro-2'-deoxyuridine-5'-O-monophosphate; FdUMP); (2) elevated expression or activity of the primary enzymatic target thymidylate synthase (TS); and (3) dysregulated programmed cell death as important causes of 5-FU resistance. Importantly, these causes of 5-FU resistance can potentially be overcome through the use of next-generation fluoropyrimidine (FP) polymers (e.g., CF10) that display reduced dependence on anabolic metabolism and more potent TS inhibitory activity.

Assessing the effects of the cytostatic drug 5-Fluorouracil alone and in a mixture of emerging contaminants on the mussel Mytilus galloprovincialis

The assessment of contaminants of emerging concern, alone and in mixtures, and their effects on marine biota requires attention. 5-Fluorouracil is a cytostatic category 3 anti-cancer medication (IARC) that is used to treat a variety of cancers, including colon, pancreatic, and breast cancer. In the presence of other pollutants, this pharmaceutical can interact and form mixtures of contaminants, such as adhering to plastics and interaction with metal nanoparticles. This study aimed to comprehend the effects of 5-Fluorouracil (5FU; 10 ng/L) and a mixture of emerging contaminants (Mix): silver nanoparticles (nAg; 20 nm; 10 μg/L), polystyrene nanoparticles (nPS; 50 nm; 10 μg/L) and 5FU (10 ng/L), in an in vivo (21 days) exposure of the mussel Mytilus galloprovincialis. A multibiomarker approach namely genotoxicity, the antioxidant defence system (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), glutathione - S - transferases (GST) activities), and oxidative damage (LPO) was used to assess the effects in gills and digestive gland of mussels. Both treatments cause genotoxicity in mussel's haemolymph, and antagonism between contaminants was observed in the Mix. Genotoxicity observed confirms 5FU's mode of action (MoA) by DNA damage. The antioxidant defence system of mussels exposed to 5FU kicked in and counter balanced ROS generated during the exposure, though the same was not seen in Mix-exposed mussels. Mussels were able to withstand the effects of the single compound but not the effects of the Mix. For oxidative stress and damage, the interactions of the components of the mixture have a synergistic effect.

In Vivo and In Vitro Enhanced Tumoricidal Effects of Metformin, Active Vitamin D3, and 5-Fluorouracil Triple Therapy against Colon Cancer by Modulating the PI3K/Akt/PTEN/mTOR Network

Chemoresistance to 5-fluorouracil (5-FU) is common during colorectal cancer (CRC) treatment. This study measured the chemotherapeutic effects of 5-FU, active vitamin D3 (VD3), and/or metformin single/dual/triple regimens as complementary/alternative therapies. Ninety male mice were divided into: negative and positive (PC) controls, and 5-FU, VD3, Met, 5-FU/VD3, 5-FU/Met, VD3/Met, and 5-FU/VD3/Met groups. Treatments lasted four weeks following CRC induction by azoxymethane. Similar regimens were also applied in the SW480 and SW620 CRC cell lines. The PC mice had abundant tumours, markedly elevated proliferation markers (survivin/CCND1) and PI3K/Akt/mTOR, and reduced p21/PTEN/cytochrome C/caspase-3 and apoptosis. All therapies reduced tumour numbers, with 5-FU/VD3/Met being the most efficacious regimen. All protocols decreased cell proliferation markers, inhibited PI3K/Akt/mTOR molecules, and increased proapoptotic molecules with an apoptosis index, and 5-FU/VD3/Met revealed the strongest effects. In vitro, all therapies equally induced G1 phase arrest in SW480 cells, whereas metformin-alone showed maximal SW620 cell numbers in the G0/G1 phase. 5-FU/Met co-therapy also showed the highest apoptotic SW480 cell numbers (13%), whilst 5-FU/VD3/Met disclosed the lowest viable SW620 cell percentages (81%). Moreover, 5-FU/VD3/Met revealed maximal inhibitions of cell cycle inducers (CCND1/CCND3), cell survival (BCL2), and the PI3K/Akt/mTOR molecules alongside the highest expression of cell cycle inhibitors (p21/p27), proapoptotic markers (BAX/cytochrome C/caspase-3), and PTEN in both cell lines. In conclusion, metformin monotherapy was superior to VD3, whereas the 5-FU/Met protocol showed better anticancer effects relative to the other dual therapies. However, the 5-FU/VD3/Met approach displayed the best in vivo and in vitro tumoricidal effects related to cell cycle arrest and apoptosis, justifiably by enhanced modulations of the PI3K/PTEN/Akt/mTOR pathway.

Enhanced in vitro tumoricidal effects of 5-Fluorouracil, thymoquinone, and active vitamin D3 triple therapy against colon cancer cells by attenuating the PI3K/AKT/mTOR pathway

AIMS

This study measured the effects of 5-Fluorouracil (5-FU), calcitriol (VD₃), and/or thymoquinone (TQ) single/dual/triple therapies on cell cycle progression, apoptosis, inhibition of the PI3K/AKT/mTOR pathway, and oxidative stress against colorectal cancer (CRC).

MAIN METHODS

The HT29, SW480 and SW620 cell lines were treated with 5-FU (50 μM), VD₃ (25 μM), and TQ (75 μM), alone or combined for 12 h, prior to cell cycle/apoptosis analyses.

KEY FINDINGS

TQ monotherapy had greater anticancer effects to active VD₃ or 5-FU, revealing higher expression of p21/p27/PTEN/BAX/Cyto-C/Casp-3 and increased levels of total glutathione, with inhibitions in CCND1/CCND3/BCL-2 and PI3K/AKT/mTOR molecules, alongside higher rates of apoptosis in HT29, SW480 and SW620 cells (P < 0.005 for all markers). Additionally, all combination protocols revealed enhanced modulations of the PI3K/PTEN/Akt/mTOR pathway, higher expression of p21/p27/PTEN/BAX/Cyto-C/Casp-3, and better anti-oxidant effects, than the monotherapies. Although TQ/5-FU and TQ/VD₃ co-therapies were better relative to the VD₃/5-FU regimen, the best tumoricidal effects were observed with triple therapy in the HT29 and SW480 cell lines, possibly by boosted attenuations of the PI3K/AKT/mTOR oncogenic pathway. In contrast, TQ single treatment was more effective than the triple therapy regimen in metastatic SW620 cells, suggesting that this protocol would be more useful therapeutically in late-stage CRC.

SIGNIFICANCE

In conclusion, this study is the first to demonstrated enhanced anti-tumorigenic effects for VD₃, TQ, and 5-FU triple therapy against CRC cells and could represent the best strategy for treating early stages of malignancy, whereas TQ monotherapy could be a better approach for treating metastatic forms of the disease.

SMAD7 and SMAD4 expression in colorectal cancer progression and therapy response

Inhibitory SMAD7 and common mediator SMAD4 play crucial roles in SMAD-dependent TGF-β signaling that is often disrupted in colorectal cancer (CRC). This study aimed to profile the expression of SMAD7 and SMAD4 in primary and metastatic CRC and to evaluate their significance in disease progression and therapy response. The expression of SMAD7 and SMAD4 genes was analyzed by quantitative real-time PCR in tissues from 35 primary and metastatic CRC patients and in vitro in 7 human cell lines originating from colon tissue. Expression levels of SMAD7 and SMAD4, as well as their ratio, were determined and their association with tumor characteristics and response to therapy were evaluated. SMAD4 level was significantly lower in tumors compared to non-tumor tissues in both primary (p = 0.001) and metastatic (p = 0.001) CRC patients, while tumor expression of SMAD7 was significantly lower from non-tumor tissue only in metastatic patients (p = 0.017). SMAD7/SMAD4 ratio was elevated in CRC primary tumor tissues and cell lines compared to corresponding non-tumor tissues and cell line, respectively (p = 0.003). SMAD7 expression was significantly elevated in primary tumor tissues obtained from responders to neoadjuvant chemoradiotherapy (nCRT) compared to non-responders (p = 0.014). Alterations of expression and ratio of SMAD7 and SMAD4 in CRC cell lines, primary rectal cancer, and liver metastasis emphasize the importance of these genes in different stages of disease progression. Differential expression of SMAD7 in responders versus non-responders to nCRT should be further investigated for its potential predictive value.

Occurrence and ecotoxicity of cytostatic drugs 5-fluorouracil and methotrexate in the freshwater unionid Elliptio complanata

Municipal effluents continuously release cytostatic drugs with unknown consequences in aquatic organisms. The purpose of the study was to examine the sublethal toxicity of 2 commonly-found cytostatic drugs 5-fluouracile (5-FLU) and methotrexate (MTX) to endemic Elliptio complanata freshwater mussels. The mussels were exposed of each drugs at 0, 4, 20 and 100 μg/L for 96 h t 15 °C. After the exposure period, glutathione S-transferase (GST) and dehydrofolate reductase (DHFR) activities, DNA damage and lipid peroxidation (LPO) were determined. The drugs were detected in mussel tissues with no evidence of accumulation with either drugs. The drug 5-FLU gave a larger spectrum of effects than MTX such as increased DHFR, decreased LPO and DNA strand breaks (repair activity) suggesting that the mussels were metabolically hindered and reduced DNA repair activity. The drug MTX only increased DHFR activity in the gonad. Hence, the data suggest that these drugs are biologically active in freshwater mussels and based on the reported maximum levels of these drugs in municipal effluents, the observed effects are likely in sessile freshwater mussel species downstream urban sources of pollution.

Preferential uptake of antibody targeted calcium phosphosilicate nanoparticles by metastatic triple negative breast cancer cells in co-cultures of human metastatic breast cancer cells plus bone osteoblasts

Calcium phosphosilicate nanoparticles (CPSNPs) are bioresorbable nanoparticles that can be bioconjugated with targeting molecules and encapsulate active agents and deliver them to tumor cells without causing damage to adjacent healthy tissue. Data obtained in this study demonstrated that an anti-CD71 antibody on CPSNPs targets these nanoparticles and enhances their internalization by triple negative breast cancer cells in-vitro. Caspase 3,7 activation, DNA damage, and fluorescent microscopy confirmed the apoptotic breast cancer response caused by targeted anti-CD71-CPSNPs encapsulated with gemcitabine monophosphate, the active metabolite of the chemotherapeutic gemcitabine used to treat cancers including breast and ovarian. Targeted anti-CD71-CPSNPs encapsulated with the fluorophore, Rhodamine WT, were preferentially internalized by breast cancer cells in co-cultures with osteoblasts. While osteoblasts partially internalized anti-CD71-GemMP-CPSNPs, their cell growth was not affected. These results suggest that CPSNPs may be used as imaging tools and selective drug delivery systems for breast cancer that has metastasized to bone.

Synthesis of bioactive polyaniline-b-polyacrylic acid copolymer nanofibrils as an effective antibacterial and anticancer agent in cancer therapy, especially for HT29 treatment

In this work, a new highly water-soluble copolymer of polyacrylic acid with polyaniline is introduced. Acrylic acid was polymerized via the Reversible Addition Fragmentation Chain Transfer method (RAFT) in the presence of an initiator and the obtained polyacrylic acid was copolymerized with aniline at room temperature. As the main achievements of this work, the resulting block copolymer with nanosized structure revealed favorable solubility in polar solvents, as well as excellent antibacterial and anticancer activities. Therefore, it is an appropriate candidate for medical applications such as wound healing and cancer therapy, especially in HT29 treatment.

Gliclazide Prevents 5-FU-Induced Oral Mucositis by Reducing Oxidative Stress, Inflammation, and P-Selectin Adhesion Molecules

Oral mucositis (OM) is one of the main side effects of the head and neck cancer treatment, particularly radiotherapy and/or chemotherapy. OM is characterized by ulcers, erythema, dysphagia, xerostomia, and increased susceptibility to opportunistic infections. In the perspective of finding pharmacological therapies to prevent inflammation and ulceration of OM, the investigation of the pleiotropic effect of commercial drugs is needed, among them gliclazide, an antidiabetic drug. This study aimed to evaluate the effect of gliclazide in an experimental OM model induced by 5-fluorouracil. Male hamsters were pre-treated with oral gliclazide (1, 5, or 10 mg/kg) for 10 days. Cheek pouch samples were subjected to histopathological and immunohistochemical analysis (COX₂, iNOS, MMP-2, NFκB P65, GPx) and imunofluorescence (P-selectin). IL-1β and TNF-α levels, Myeloperoxidase activity (MPO) and malondialdehyde (MDA) levels were investigated by ultraviolet-visible spectroscopy analysis. NFκB NLS P50 protein levels were analyzed by western blotting. The group treated with gliclazide at a dose of 10 mg/kg showed presence of erythema, no evidence of erosion, and absence of mucosal ulceration with a score of 1 (1–2) (p < 0.01). Histopathological data for the group treated with gliclazide 10 mg/kg showed re-epithelialization, discrete mononuclear inflammatory infiltrate and absence of hemorrhage, edema, ulcers and abscesses with a score of 1 (1–1) (p < 0.01). Treatment with gliclazide 10 mg/kg reduced MPO activity (p < 0.001), MDA levels (p < 0.001) and NFκB NLS P50 (p < 0.05) protein levels, resulting in low immunostaining to Cox-2, iNOS (p < 0.05), NFκB P65 (p < 0.05), and negative immunoreaction to MMP-2 (p < 0.001). However, it appeared that for Gpx1, the staining was restored in the GLI 10-FUT group compared with 5FUT/saline (p < 0.05). Immunofluorescence revealed decreased levels of P-selectin (p < 0.001) after treatment with gliclazide 10 mg/kg (p < 0.05). In summary, gliclazide accelerated mucosal recovery and reduced oxidative stress and inflammation in the 5-FU-induced OM in hamsters.

Hyperglycemia Promotes Chemoresistance Through the Reduction of the Mitochondrial DNA Damage, the Bax/Bcl-2 and Bax/Bcl-XL Ratio, and the Cells in Sub-G1 Phase Due to Antitumoral Drugs Induced-Cytotoxicity in Human Colon Adenocarcinoma Cells

Diabetes and cancer are common, chronic, and potentially fatal diseases that frequently co-exist. Observational studies clearly indicate that the risk of several types of cancer is increased in diabetic patients and a number of cancer types have shown a higher mortality rate in patients with hyperglycemic associated pathologies. This scenario could be due, at least in part, to a lower efficacy of the cancer treatments which needs to be better investigated. Here, we evaluated the effects of a prolonged exposure to high glucose (HG) to the response to chemotherapy on human colon adenocarcinoma HT29 and LOVO cell lines. We observed that hyperglycemia protected against the decreased cell viability and cytotoxicity and preserved from the mitochondrial DNA lesions induced by doxorubicin (DOX) and 5-fluorouracil (5-FU) treatments by lowering ROS production. In HT29 cells the amount of intracellular DOX and its nuclear localization were not modified by HG incubation in terms of Pgp, BCRP, MRP1, 5 and 8 activity and gene expression. On the contrary, in LOVO cells, the amount of intracellular DOX was significantly decreased after a bolus of DOX in HG condition and the expression and activity of MPR1 was increased, suggesting that HG promotes drug chemoresistance in both HT29 and LOVO cells, but in a different way. In both cell types, HG condition prevented the susceptibility to apoptosis by decreasing the ratio Bax/Bcl-2 and Bax/Bcl-XL and diminished the level of cytosolic cytochrome c and the cleavage of full length of PARP induced by DOX and 5-FU. Finally, hyperglycemia reduced cell death by decreasing the cell percentage in sub-G1 peak induced by DOX (via a cell cycle arrest in the G2/M phase) and 5-FU (via a cell cycle arrest in the S phase) in HT29 and LOVO cells. Taken together, our data showed that a prolonged exposure to HG protects human colon adenocarcinoma cells from the cytotoxic effects of two widely used chemotherapeutic drugs, impairing the effectiveness of the chemotherapy itself.

Frondoside A Enhances the Anti-Cancer Effects of Oxaliplatin and 5-Fluorouracil on Colon Cancer Cells

Over recent years, we have demonstrated that Frondoside A, a triterpenoid glycoside isolated from an Atlantic sea cucumber, has potent in vitro and in vivo anti-cancer effects against human pancreatic, breast, and lung cancer. We have also demonstrated that Frondoside A is able to potentiate and/or synergize the anti-cancer effects of major classical cytotoxic agents, namely, gemcitabine, paclitaxel, and cisplatin, in the treatment of pancreatic, breast, and lung cancer, respectively. This study evaluates the impact of Frondoside A alone and in combination with the standard cytotoxic drugs oxaliplatin and 5-fluorouracil (5-FU) in the treatment of colon cancer using three human colon cancer cell lines, namely, HT-29, HCT-116, and HCT8/S11. We demonstrate that Frondoside A, oxaliplatin, and 5-FU cause a concentration- and time-dependent reduction in the number of HT-29 colon cancer cells. A concentration of 2.5 &micro;M of Frondoside A led to almost 100% inhibition of cell numbers at 72 h. A similar effect was only observed with a much higher concentration (100 &micro;M) of oxaliplatin or 5-FU. The reduction in cell numbers by Frondoside A, oxaliplatin, and 5-FU was also confirmed in two other colon cancer cell lines, namely, HCT8/S11 and HCT-116, treated for 48 h. The combinations of low concentrations of these drugs for 48 h in vitro clearly demonstrated that Frondoside A enhances the inhibition of cell numbers induced by oxaliplatin or 5-FU. Similarly, such a combination also efficiently inhibited colony growth in vitro. Interestingly, we found that the inhibition of ERK1/2 phosphorylation was significantly enhanced when Frondoside A was used in combination treatments. Moreover, we show that Frondoside A and 5-FU, when used alone, induce a concentration-dependent induction of apoptosis and that their pro-apoptotic effect is dramatically enhanced when used in combination. We further demonstrate that apoptosis induction upon the treatment of colon cancer cells was at least in part a result of the inhibition of phosphorylation of the survival kinase AKT, leading to caspase-3 activation, poly (ADP-ribose) polymerase (PARP) inactivation, and consequently DNA damage, as suggested by the increase in the level of &gamma;H2AX. In light of these findings, we strongly suggest that Frondoside A may have a role in colon cancer therapy when used in combination with the standard cytotoxic drugs oxaliplatin and 5-FU.

Downregulation of ubiquitin-specific peptidase 39 suppresses the proliferation and induces the apoptosis of human colorectal cancer cells

Ubiquitin-specific peptidase 39 (USP39) has been reported to participate in the mitotic spindle checkpoint and the process of cytokinesis. and has been identified as a therapeutic target for various types of cancer. However, the effect of USP39 in colorectal cancer (CRC) has not been investigated. To explore the functional role of USP39 in CRC cell growth, lentivirus-mediated RNA interference was applied to inhibit USP39 expression in SW1116 and HCT116 cells. The relative USP39 mRNA and protein expression levels were significantly reduced in the USP39 knockdown cells, as verified by reverse transcription-quantitative polymerase chain reaction and western blot analysis. USP39 knockdown significantly reduced the proliferation and colony formation abilities of CRC cells, and induced apoptosis and cell cycle arrest in the G₂/M phases, as determined by an MTT assay, a colony formation assay and flow cytometry analysis. Furthermore, western blot analysis demonstrated that USP39 knockdown may have induced apoptosis through the upregulation of p53, p-p53, PARP and caspase-3 expression in SW1116 cells. In conclusion, USP39 may be a novel biological marker for targeted therapy against CRC, and requires further investigation.

GOLPH3 expression promotes the resistance of HT29 cells to 5‑fluorouracil by activating multiple signaling pathways

The novel proto‑oncogene Golgi phosphoprotein (GOLPH)3 is overexpressed in a variety of tumor tissues and is associated with poor prognosis. The authors previously demonstrated that GOLPH3 gene is overexpressed in colorectal cancer tissues and promotes the proliferation of colonic cancer cells by activating the phosphatidylinositol‑3‑kinase/protein kinase B/the mammalian target of rapamycin and Wnt/β‑catenin signaling pathways. However, to the best of the authors' knowledge, if and how the GOLPH3 gene is involved in inducing resistance to colonic cancer chemotherapy has not been reported. In the present study, the association between the overexpression of the GOLPH3 gene and resistance of HT29 colonic cancer cells to 5‑fluorouracil (5‑FU) was investigated. Following confirmation of the effective silencing of the GOLPH3 gene, proliferation and apoptosis of colonic cancer cells were detected by MTT assay, colony formation assay and flow cytometry, and then the mechanism of GOLPH3‑induced resistance to 5‑FU chemotherapy in colonic cancer cells was investigated by western blotting. The results demonstrated that the expression of phosphorylated (p)‑glycoprotein and GOLPH3 was increased in HT29 cells following treatment with 5‑FU, which resulted in the development of drug resistance. Silencing GOLPH3 increased the sensitivity of HT29 cells to 5‑FU, reduced their tumorigenicity and partly reversed their resistance to 5‑FU. The expression of p‑extracellular signal‑regulated kinase (pERK)1/2 and β‑catenin was decreased, which indicated that its mechanism was associated with the activation of the mitogen‑activated protein kinase/ERK and Wnt/β‑catenin signaling pathways. Therefore, GOLPH3 may be a potential, novel target for reversing chemotherapy resistance in colon cancer.

Effective encapsulation and biological activity of phosphorylated chemotherapeutics in calcium phosphosilicate nanoparticles for the treatment of pancreatic cancer

Drug resistant cancers like pancreatic ductal adenocarcinoma (PDAC) are difficult to treat, and nanoparticle drug delivery systems can overcome some of the limitations of conventional systemic chemotherapy. In this study, we demonstrate that FdUMP and dFdCMP, the bioactive, phosphorylated metabolites of the chemotherapy drugs 5-FU and gemcitabine, can be encapsulated into calcium phosphosilicate nanoparticles (CPSNPs). The non-phosphorylated drug analogs were not well encapsulated by CPSNPs, suggesting the phosphate modification is essential for effective encapsulation. In vitro proliferation assays, cell cycle analyses and/or thymidylate synthase inhibition assays verified that CPSNP-encapsulated phospho-drugs retained biological activity. Analysis of orthotopic tumors from mice treated systemically with tumor-targeted FdUMP-CPSNPs confirmed the in vivo up take of these particles by PDAC tumor cells and release of active drug cargos intracellularly. These findings demonstrate a novel methodology to efficiently encapsulate chemotherapeutic agents into the CPSNPs and to effectively deliver them to pancreatic tumor cells.

Aptamer-Drug Conjugates of Active Metabolites of Nucleoside Analogs and Cytotoxic Agents Inhibit Pancreatic Tumor Cell Growth

Aptamer-drug conjugates (ApDCs) have the potential to improve the therapeutic index of traditional chemotherapeutic agents due to their ability to deliver cytotoxic drugs specifically to cancer cells while sparing normal cells. This study reports on the conjugation of cytotoxic drugs to an aptamer previously described by our group, the pancreatic cancer RNA aptamer P19. To this end, P19 was incorporated with gemcitabine and 5-fluorouracil (5-FU), or conjugated to monomethyl auristatin E (MMAE) and derivative of maytansine 1 (DM1). The ApDCs P19-dFdCMP and P19-5FdUMP were shown to induce the phosphorylation of histone H2AX on Ser139 (γ-H2AX) and significantly inhibited cell proliferation by 51%-53% in PANC-1 and by 54%-34% in the gemcitabine-resistant pancreatic cancer cell line AsPC-1 (p ≤ 0.0001). P19-MMAE and P19-DM1 caused mitotic G2/M phase arrest and inhibited cell proliferation by up to 56% in a dose-dependent manner when compared to the control group (p ≤ 0.001). In addition, the cytotoxicity of P19-MMAE and P19-DM1 in normal cells and the control human breast cancer cell line MCF7 was minimal. These results suggest that this approach may be useful in decreasing cytotoxic side effects in non-tumoral tissue.

Three Combined Treatments, a Novel HDAC Inhibitor OBP-801/YM753, 5-Fluorouracil, and Paclitaxel, Induce G₂ Phase Arrest Through the p38 Pathway in Human Ovarian Cancer Cells

Ovarian cancer is the most lethal disease among gynecological malignancies. More effective therapy is required to counter high recurrence rates and chemotherapy resistance. We investigated the efficacy and molecular mechanisms of three combined treatments (TCTs)—a novel histone deacetylase (HDAC) inhibitor OBP-801/YM753, 5-fluorouracil (5-FU), and paclitaxel (PTX)—in human ovarian cancer SKOV-3 and OVCAR-3 cells. The inhibition of cell growth was stronger with TCTs than with each single agent and with two combined treatments. The TCTs significantly induce G₂ phase arrest in both cell lines. We then analyzed the molecular mechanisms and found that the TCTs increased the phosphorylation of p38 (Thr180/Tyr182), decreased the expression of CDC25C, and increased the phosphorylation of CDC2 (Tyr15), an inactive form of CDC2. To examine the responsibilities of the p38 pathway for G₂ phase arrest induced by the TCTs, we employed the p38 inhibitor SB203580. SB203580 inhibited G₂ phase arrest, suppression of CDC25C, and phosphorylation of CDC2 (Tyr15) induced by the TCTs. These results suggest that the TCTs can induce G₂ phase arrest through activation of the p38 signaling pathway. We therefore believe that this combination is promising as a novel therapeutic strategy against ovarian cancer.

Evaluation of a Novel Approach for Reducing Emissions of Pharmaceuticals to the Environment

Increased interest over the levels of pharmaceuticals detected in the environment has led to the need for new approaches to manage their emissions. Inappropriate disposal of unused and waste medicines and release from manufacturing plants are believed to be important pathways for pharmaceuticals entering the environment. In situ treatment technologies, which can be used on-site in pharmacies, hospitals, clinics, and at manufacturing plants, might provide a solution. In this study we explored the use of Pyropure, a microscale combined pyrolysis and gasification in situ treatment system for destroying pharmaceutical wastes. This involved selecting 17 pharmaceuticals, including 14 of the most thermally stable compounds currently in use and three of high environmental concern to determine the technology's success in waste destruction. Treatment simulation studies were done on three different waste types and liquid, solid, and gaseous emissions from the process were analyzed for parent pharmaceutical and known active transformation products. Gaseous emissions were also analyzed for NOx, particulates, dioxins, furans, and metals. Results suggest that Pyropure is an effective treatment process for pharmaceutical wastes: over 99 % of each study pharmaceutical was destroyed by the system without known active transformation products being formed during the treatment process. Emissions of the other gaseous air pollutants were within acceptable levels. Future uptake of the system, or similar in situ treatment approaches, by clinics, pharmacists, and manufacturers could help to reduce the levels of pharmaceuticals in the environment and reduce the economic and environmental costs of current waste management practices.

Application of Mouse Embryonic Stem Cell Test to Detect Gender-Specific Effect of Chemicals: A Supplementary Tool for Embryotoxicity Prediction

Gender effect is an inherent property of chemicals, characterized by variations caused by the chemical-biology interaction. It has widely existed, but the shortage of an appropriate model restricts the study on gender-specific effect. The embryonic stem cell test (EST) has been utilized as an alternative test for developmental toxicity. Despite its numerous improvements, mouse embryonic stem cells with an XX karyotype have not been used in the EST, which restricts the ability of the EST to identify gender-specific effects during high-throughput-screening (HTS) of chemicals to date. To address this, the embryonic stem cell (ESC) SP3 line with an XX karyotype was used to establish a "female" model as a complement to EST. Here, we proposed a "double-objects in unison" (DOU)-EST, which consisted of male ESC and female ESC; a seven-day EST protocol was utilized, and the gender-specific effect of chemicals was determined and discriminated; the replacement of myosin heavy chain (MHC) with myosin light chain (MLC) provided a suitable molecular biomarker in the DOU-EST. New linear discriminant functions were given in the purpose of distinguishing chemicals into three classes, namely, no gender-specific effect, male-susceptive, and female-susceptive. For 15 chemicals in the training set, the concordances of prediction result as no gender effect, male susceptive, and female susceptive were 86.67%, 86.67%, and 93.33%, respectively, the sensitivities were 66.67%, 83.33%, and 83.33%, respectively, and the specificities were 91.67%, 88.89%, and 100%, respectively; the total accuracy of DOU-EST was 86.67%. For three chemicals in the test set, one was incorrectively predicted. The possible reason for misclassification may due to the absence of hormone environment in vitro. Leave-one-out cross-validation (LOOCV) indicated a mean error rate of 18.34%. Taken together, these data suggested a good performance of the proposed DOU-EST. Emerging chemicals with undiscovered gender-specific effects are anticipated to be screened with the DOU-EST.

Knockdown of Myosin 6 inhibits proliferation of oral squamous cell carcinoma cells

BACKGROUND

Oral squamous cell carcinoma (OSCC) accounts for 95% of all oral cancer with higher mortality and morbidity rates worldwide. However, the potential molecular mechanism of OSCC remains largely unclear. Myosin VI (MYO6) is a unique actin motor and reported to be overexpressed in several cancers. This study aims to examine the functional relationship between OSCC and MYO6.

METHODS

The mRNA expression of MYO6 was firstly investigated by analyzing data derived from Oncomine database. On the basis of the results, the expression of MYO6 was knocked down using lentivirus-delivered RNA interference in human OSCC cell line CAL27, as confirmed by qPCR and Western blot analysis. Stable MYO6 knockdown cells were employed to determine the effects of MYO6-silencing on cell growth by MTT, colony formation and cell cycle distribution and apoptosis by flow cytometry assay. Moreover, the expressions of cell apoptotic proteins were examined by Western blot analysis.

RESULTS

We first observed MYO6 was overexpressed in tongue squamous cell carcinoma TSCC belongs to OSCC, compared with normal tissues. For cellular analysis, shRNA sequences against MYO6 could efficiently reduce its expression in CAL27 cells. Knockdown of MYO6 significantly decreased cell proliferation, caused cell cycle arrest at G2/M phase, and promoted cell apoptosis. Moreover, cell apoptosis-associated proteins, caspase-3 and PARP, were obviously upregulated in CAL27 after MYO6-silencing.

CONCLUSION

MYO6 could play an essential role in the growth of OSCC cells via regulation of cell cycle progression and apoptosis.

Exploring Different Strategies for Efficient Delivery of Colorectal Cancer Therapy

Colorectal cancer (CRC) is the third most common cancer and the fourth leading cause of cancer death in the world. Currently available chemotherapy of CRC usually delivers the drug to both normal as well as cancerous tissues, thus leading to numerous undesirable effects. Much emphasis is being laid on the development of effective drug delivery systems for achieving selective delivery of the active moiety at the anticipated site of action with minimized unwanted side effects. Researchers have employed various techniques (dependent on pH, time, pressure and/or bacteria) for targeting drugs directly to the colonic region. On the other hand, systemic drug delivery strategies to specific molecular targets (such as FGFR, EGFR, CD44, EpCAM, CA IX, PPARγ and COX-2) overexpressed by cancerous cells have also been shown to be effective. This review aims to put forth an overview of drug delivery technologies that have been, and may be developed, for the treatment of CRC.

Jianpi Huayu Decoction Inhibits Proliferation in Human Colorectal Cancer Cells (SW480) by Inducing G0/G1-Phase Cell Cycle Arrest and Apoptosis

Jianpi Huayu Decoction (JHD), a Chinese medicine formula, is a typical prescription against multiple tumors in the clinical treatment, which can raise quality of life and decrease complications. The aim of this study is to assess the efficacy of JHD against human colorectal carcinoma cells (SW480) and explore its mechanism. MTT assay showed that JHD decreased the cellular viability of SW480 cells in dose-dependent and time-dependent manner. Flow cytometry analysis revealed that JHD induced G0/G1-phase cell cycle arrest in SW480 cells and had a strong apoptosis-inducing effect on SW480 cells. Meanwhile it enhanced the expression of p27, cleaved PARP, cleaved caspase-3, and Bax and decreased the levels of PARP, caspase-3, Bcl-2, CDK2, CDK4, CDK6, cyclin D1, cyclin D2, cyclin D3, and cyclin E1, which was evidenced by RT-qPCR and Western blot analysis. In conclusion, these results indicated that JHD inhibited proliferation in SW480 cells by inducing G0/G1-phase cell cycle arrest and apoptosis, providing a practicaltherapeutic strategy against colorectal cancer.

Eco-genotoxicity of six anticancer drugs using comet assay in daphnids

The eco-genotoxicity of six anti-neoplastic drugs, 5-fluorouracil, capecitabine, cisplatin, doxorubicin, etoposide, and imatinib, belonging to five classes of anatomical therapeutic classification (ATC), was studied applying the in vivo comet assay on cells from whole organisms of Daphnia magna and Ceriodaphnia dubia. For the first time, this test was performed in C. dubia. In addition, to have a wider genotoxic/mutagenic profile of the anticancer drugs selected, SOS chromotest and Salmonella mutagenicity assay were performed. The comet results showed that all drugs induced DNA damage, in both Cladocerans, with environmental concern; indeed Doxorubicin induced DNA damage in the order of tens of ng L(-1) in both crustaceans, as well as 5-flurouracil in C. dubia and cisplatin in D. magna. In the SOS Chromotest all drugs, except imatinib, were able to activate the repair system in Escherichia coli PQ37 while in the Salmonella mutagenicity assay, doxorubicin was the only drug able to cause direct and indirect frameshift and base-pair substitution mutations. Comet assay was the most sensitive tool of genotoxic exposure assessment, able to detect in vivo the adverse effects at concentration lower than those evaluated in vitro by bacterial assays.

Intravenous administration of retroviral replicating vector, Toca 511, demonstrates therapeutic efficacy in orthotopic immune-competent mouse glioma model

Toca 511 (vocimagene amiretrorepvec), a nonlytic, amphotropic retroviral replicating vector (RRV), encodes and delivers a functionally optimized yeast cytosine deaminase (CD) gene to tumors. In orthotopic glioma models treated with Toca 511 and 5-fluorocytosine (5-FC) the CD enzyme within infected cells converts 5-FC to 5-fluorouracil (5-FU), resulting in tumor killing. Toca 511, delivered locally either by intratumoral injection or by injection into the resection bed, in combination with subsequent oral extended-release 5-FC (Toca FC), is under clinical investigation in patients with recurrent high-grade glioma (HGG). If feasible, intravenous administration of vectors is less invasive, can easily be repeated if desired, and may be applicable to other tumor types. Here, we present preclinical data that support the development of an intravenous administration protocol. First we show that intravenous administration of Toca 511 in a preclinical model did not lead to widespread or uncontrolled replication of the RVV. No, or low, viral DNA was found in the blood and most of the tissues examined 180 days after Toca 511 administration. We also show that RRV administered intravenously leads to efficient infection and spread of the vector carrying the green fluorescent protein (GFP)-encoding gene (Toca GFP) through tumors in both immune-competent and immune-compromised animal models. However, initial vector localization within the tumor appeared to depend on the mode of administration. Long-term survival was observed in immune-competent mice when Toca 511 was administered intravenously or intracranially in combination with 5-FC treatment, and this combination was well tolerated in the preclinical models. Enhanced survival could also be achieved in animals with preexisting immune response to vector, supporting the potential for repeated administration. On the basis of these and other supporting data, a clinical trial investigating intravenous administration of Toca 511 in patients with recurrent HGG is currently open and enrolling.

Herbal medicine Guan Chang Fu Fang enhances 5-fluorouracil cytotoxicity and affects drug-associated genes in human colorectal carcinoma cells

Guan Chang Fu Fang (GCFF) is a natural compound, which is extracted from three medicinal plants, Agrimonia pilosa Ledeb., Patrinia scabiosaefolia and Solanum nigrum L. GCFF has demonstrated clinical efficacy in the treatment of colon cancer. At present, 5-fluorouracil (5-FU) is the primary active chemotherapeutic agent used for treating colon cancer. Using median-effect and apoptosis analyses, fluorescence microscopy and western blotting, the present study analyzed the association between GCFF and 5-FU in the human colon adenocarcinoma LoVo cell line. The effect of GCFF on the expression of chemotherapeutic agent-associated genes was also investigated. The results of the synergistic analysis revealed that GCFF exhibited a significant effect upon 5-FU-associated cytotoxicity within the LoVo cell line. This effect was observed over a broad dose-inhibition range (5–95%), but was particularly significant in the lower concentrations. The flow cytometry results revealed that low doses of GCFF or 5-FU induced S-phase arrest, as did a low-dose combination of the two drugs. After 48 h, GCFF significantly suppressed the expression levels of the chemotherapeutic agent resistance-associated genes within the colon cancer cells. The western blot analysis revealed that the combined effects of 5-FU and GCFF were due to a regulation of the B-cell lymphoma-2 family of proteins. The findings of the present study suggested that GCFF, when combined with 5-FU, has the potential to be a novel, chemotherapeutic compound for the treatment of colon cancer.

The impact of in vivo and in vitro exposure to base analogue 5-FU on the level of DNA damage in haemocytes of freshwater mussels Unio pictorum and Unio tumidus

The impact of in vivo and in vitro exposure to anticancer drug 5-Fluorouracil (5-FU) on the level of DNA damage was evaluated using comet assay on haemocytes of freshwater mussels Unio pictorum and Unio tumidus. For the in vivo experiment, the groups of 5 mussels per concentration were exposed for 72 h to 5-FU (0.04, 0.4, 4, 40 and 100 μM) with 0.4 μM being the lowest concentration to induce significant DNA damage. For the in vitro experiment, the primary cultures of haemocytes were treated with 0.04, 0.4, 4 and 40 μM 5-FU for 22 h and the treatment with CdCl2 was used as a positive control. In contrast to in vivo exposure, 5-FU did not induce significant increase of DNA damage in vitro, possibly because of the absence of haemocytes proliferation in primary cultures.

Effects of 5-fluorouracil in nuclear and cellular morphology, proliferation, cell cycle, apoptosis, cytoskeletal and caveolar distribution in primary cultures of smooth muscle cells

Colon cancer is one of the most prevalent types of cancer in the world and is one of the leading causes of cancer death. The anti-metabolite 5- fluorouracil (5-FU) is widely used in the treatment of patients with colon cancer and other cancer types. 5-FU-based chemotherapy has been shown to be very efficient in the improvement of overall survival of the patients and for the eradication of the disease. Unfortunately, common side effects of 5-FU include severe alterations in the motility of the gastrointestinal tissues. Nevertheless, the molecular and cellular effects of 5-FU in smooth muscle cells are poorly understood. Primary smooth muscle cell cultures are an important tool for studies of the biological consequences of 5-FU at the cellular level. The avian gizzard is one of the most robust organs of smooth muscle cells. Here we studied the molecular and cellular effects of the chemotherapic drug 5-FU in a primary culture of chick gizzard smooth muscle cells. We found that treatment of smooth muscle cells with 5-FU inhibits cell proliferation by the arrest of cells in the G1 phase of cell cycle and induce apoptosis. 5-FU induced a decrease in the percentage of histone H3-positive cells. Treatment of cells with 5-FU induced changes in cellular and nuclear morphology, a decrease in the number of stress fibers and a major decrease in the number of caveolin-3 positive cells. Our results suggest that the disorganization of the actin cytoskeleton and the reduction of caveolin-3 expression could explain the alterations in contractility observed in patients treated with 5-FU. These findings might have an impact in the understanding of the cellular effects of 5-FU in smooth muscle tissues and might help the improvement of new therapeutic protocols for the treatment of colon cancer.

ATP-dependent chromatin remodeling and histone acetyltransferases in 5-FU cytotoxicity in Saccharomyces cerevisiae

Chromatin is thought to modulate access of repair proteins to DNA lesions, and may be altered by chromatin remodelers to facilitate repair. We investigated the participation of chromatin remodelers and DNA repair in 5-fluorouracil (5-FU) cytotoxicity in Saccharomyces cerevisiae. 5-FU is an antineoplastic drug commonly used in clinical settings. Among the several strains tested, only those with deficiencies in ATP-dependent chromatin remodeling (CR) and some histone acetyltransferases (HAT) exhibited sensitivity to 5-FU. CR and HAT double-mutants exhibited increased resistance to 5-FU in comparison to the wild-type mutant, but were still arrested in G2/M, as were the sensitive strains. The participation of Htz1p in 5-FU toxicity was also evaluated in single- and double-mutants of CR and HAT; the most significant effect was on cell cycle distribution. 5-FU lesions are repaired by different DNA repair machineries, including homologous recombination (HR) and post-replication repair (PRR). We investigated the role of CR and HAT in these DNA repair pathways. Deficiencies in Nhp10 and CR combined with deficiencies in HR or PRR increased 5-FU sensitivity; however, combined deficiencies of HAT, HR, and PRR did not. CRs are directly recruited to DNA damage and lead to chromatin relaxation, which facilitates access of HR and PRR proteins to 5-FU lesions. Combined deficiencies in HAT with defects in HR and PRR did not potentiate 5-FU cytotoxicity, possibly because they function in a common pathway.

5-Fluorouracil signaling through a calcium-calmodulin-dependent pathway is required for p53 activation and apoptosis in colon carcinoma cells

5-Fluorouracil (5-FU) is an anti-metabolite that is in clinical use for treatment of several cancers. In cells, it is converted into three distinct fluoro-based nucleotide analogs, which interfere with DNA synthesis and repair, leading to genome impairment and, eventually, apoptotic cell death. Current knowledge states that in certain cell types, 5-FU-induced stress is signaling through a p53-dependent induction of tumor necrosis factor-receptor oligomerization required for death-inducing signaling complex formation and caspase-8 activation. Here we establish a role of calcium (Ca(2+)) as a messenger for p53 activation in response to 5-FU. Using a combination of pharmacological and genetic approaches, we show that treatment of colon carcinoma cells stimulates entry of extracellular Ca(2+) through long lasting-type plasma membrane channels, which further directs posttranslational phosphorylation of at least three p53 serine residues (S15, S33 and S37) by means of calmodulin (CaM) activity. Obstructing this pathway by the Ca(2+)-chelator BAPTA (1,2-bis(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid) or by inhibitors of CaM efficiently reduces 5-FU-induced caspase activities and subsequent cell death. Moreover, ectopic expression of p53 S15A in HCT116 p53(-/-) cells confirmed the importance of a Ca(2+)-CaM-p53 axis in 5-FU-induced extrinsic apoptosis. The fact that a widely used therapeutic drug, such as 5-FU, is operating via this pathway could provide new therapeutic intervention points, or specify new combinatorial treatment regimes.

Genotoxicity testing of combined treatment with cisplatin, bleomycin, and 5-fluorouracil in somatic cells of Drosophila melanogaster

The simultaneous treatment with the cross-linking agent cisplatin, the radiomimetic antitumoral drug bleomycin, and the anti-metabolite drug 5-fluorouracil has been used as a regimen to treat patients with squamous cell carcinoma of the head and neck. Considering that these drugs interact directly with DNA, one of the important late-occurring complications from treatment of primary malignancies is the therapy-related secondary cancers as a result of the genotoxic activity of the drugs on normal cells. In this sense, the genotoxicity of this combination was evaluated using the wing somatic mutation and recombination test in Drosophila melanogaster. The mutant spots observed in marker-heterozygous and balancer-heterozygous flies were compared in order to quantitatively and qualitatively estimate the genotoxic effect of these drugs. Cisplatin (0.003 and 0.006mM), bleomycin (0.005 and 0.01mM), and both combinations preferentially induced recombinational events, while mutation is the major event regarding the genetic toxicity of 5-fluorouracil (0.025 and 0.05mM). The combination of these drugs produced synergistic and antagonistic genotoxic effects, depending on the concentrations used, which could impose a higher risk of secondary effects associated with their genotoxic effects, emphasizing the importance of long-term monitoring in patients being treated with these drugs.

Regulation of chemoresistance via alternative messenger RNA splicing

The acquisition of resistance to chemotherapy is a significant problem in the treatment of cancer, greatly increasing patient morbidity and mortality. Tumors are often sensitive to chemotherapy upon initial treatment, but repeated treatments can select for those cells that were able to survive initial therapy and have acquired cellular mechanisms to enhance their resistance to subsequent chemotherapy treatment. Many cellular mechanisms of drug resistance have been identified, most of which result from changes in gene and protein expression. While changes at the transcriptional level have been duly noted, it is primarily the post-transcriptional processing of pre-mRNA into mature mRNA that regulates the composition of the proteome and it is the proteome that actually regulates the cell's response to chemotherapeutic insult, inducing cell survival or death. During pre-mRNA processing, intronic non-protein-coding sequences are removed and protein-coding exons are spliced to form a continuous template for protein translation. Alternative splicing involves the differential inclusion or exclusion of exonic sequences into the mature transcript, generating different mRNA templates for protein production. This regulatory mechanism enables the potential to produce many different protein isoforms from the same gene. In this review I will explain the mechanism of alternative pre-mRNA splicing and look at some specific examples of how splicing factors, splicing factor kinases and alternative splicing of specific pre-mRNAs from genes have been shown to contribute to acquisition of the drug resistant phenotype.

Checkpoint signaling, base excision repair, and PARP promote survival of colon cancer cells treated with 5-fluorodeoxyuridine but not 5-fluorouracil

The fluoropyrimidines 5-fluorouracil (5-FU) and FdUrd (5-fluorodeoxyuridine; floxuridine) are the backbone of chemotherapy regimens for colon cancer and other tumors. Despite their widespread use, it remains unclear how these agents kill tumor cells. Here, we have analyzed the checkpoint and DNA repair pathways that affect colon tumor responses to 5-FU and FdUrd. These studies demonstrate that both FdUrd and 5-FU activate the ATR and ATM checkpoint signaling pathways, indicating that they cause genotoxic damage. Notably, however, depletion of ATM or ATR does not sensitize colon cancer cells to 5-FU, whereas these checkpoint pathways promote the survival of cells treated with FdUrd, suggesting that FdUrd exerts cytotoxicity by disrupting DNA replication and/or inducing DNA damage, whereas 5-FU does not. We also found that disabling the base excision (BER) repair pathway by depleting XRCC1 or APE1 sensitized colon cancer cells to FdUrd but not 5-FU. Consistent with a role for the BER pathway, we show that small molecule poly(ADP-ribose) polymerase 1/2 (PARP) inhibitors, AZD2281 and ABT-888, remarkably sensitized both mismatch repair (MMR)-proficient and -deficient colon cancer cell lines to FdUrd but not to 5-FU. Taken together, these studies demonstrate that the roles of genotoxin-induced checkpoint signaling and DNA repair differ significantly for these agents and also suggest a novel approach to colon cancer therapy in which FdUrd is combined with a small molecule PARP inhibitor.

Poly(ADP-Ribose) polymerase inhibition synergizes with 5-fluorodeoxyuridine but not 5-fluorouracil in ovarian cancer cells

5-Fluorouracil (5-FU) and 5-fluorodeoxyuridine (FdUrd, floxuridine) have activity in multiple tumors, and both agents undergo intracellular processing to active metabolites that disrupt RNA and DNA metabolism. These agents cause imbalances in deoxynucleotide triphosphate levels and the accumulation of uracil and 5-FU in the genome, events that activate the ATR- and ATM-dependent checkpoint signaling pathways and the base excision repair (BER) pathway. Here, we assessed which DNA damage response and repair processes influence 5-FU and FdUrd toxicity in ovarian cancer cells. These studies revealed that disabling the ATM, ATR, or BER pathways using small inhibitory RNAs did not affect 5-FU cytotoxicity. In stark contrast, ATR and a functional BER pathway protected FdUrd-treated cells. Consistent with a role for the BER pathway, the poly(ADP-ribose) polymerase (PARP) inhibitors ABT-888 (veliparib) and AZD2281 (olaparib) markedly synergized with FdUrd but not with 5-FU in ovarian cancer cell lines. Furthermore, ABT-888 synergized with FdUrd far more effectively than other agents commonly used to treat ovarian cancer. These findings underscore differences in the cytotoxic mechanisms of 5-FU and FdUrd and suggest that combining FdUrd and PARP inhibitors may be an innovative therapeutic strategy for ovarian tumors.

The herb medicine formula "chong lou fu fang" increases the cytotoxicity of chemotherapeutic agents and down-regulates the expression of chemotherapeutic agent resistance-related genes in human gastric cancer cells in vitro

The herb medicine formula “Chong Lou Fu Fang” (CLFF) has efficacy in inhibiting the proliferation of human gastric cancer in vitro and in vivo. To explore the potentially useful combination of CLFF with chemotherapeutic agents commonly used in gastric cancer therapy, we assess the interaction between CLFF and these chemotherapeutic agents in both SGC-7901 cell lines and BGC-823 cell lines using a median effect analysis and apoptosis analysis, and we also investigate the influence of CLFF on chemotherapeutic agent-associated gene expression. The synergistic analysis indicated that CLFF had a synergistic effect on the cytotoxicity of 5-fluorouracil (5-FU) in a relative broad dose inhibition range (20–95% fraction affected in SGC-7901cell lines and 5–65% fraction affected in BGC-823 cell lines), while the synergistic interaction between CLFF and oxaliplatin or docetaxel only existed in a low dose inhibition range (≤50% fraction affected in both cell lines). Combination of CLFF and chemotherapeutic agents could also induce apoptosis in a synergistic manner. After 24 h, CLFF alone or CLFF combination with chemotherapeutic agents could significantly suppress the levels of expression of chemotherapeutic agent resistance related genes in gastric cancer cells. Our findings indicate that there are useful synergistic interactions between CLFF and chemotherapeutic agents in gastric cancer cells, and the possible mechanisms might be partially due to the down-regulation of chemotherapeutic agent resistance related genes and the synergistic apoptotic effect.

Development of a High-Content Screening Method for Chemicals Modulating DNA Damage Response

The cellular response to DNA damage is emerging as a promising target for cancer therapy. In the present study, the authors exploited the relationship between the level of the phosphorylated form of histone H2AX (γH2AX) and the extent of DNA damage and developed a quantitative, cell-based, high-content screening system for measuring the DNA damage response (DDR). In this system, the authors quantified the level of γH2AX by measuring DNA damage–induced γH2AX nuclear foci using an automated cell imager. They found that the total area of γH2AX foci per cell exhibited a good correlation with the concentration of DNA damage–inducing agents, including etoposide. The effects of 2 well-known inhibitors of DNA damage could be quantified using this system, suggesting the suitability of the γH2AX-foci quantification method for large-scale screening applications. This was confirmed by using this method to screen a chemical library; the resulting “hits” included compounds that inhibited early signaling events in DDR, as well those that inhibited subsequent DNA damage repair processes. Overall, this γH2AX foci-measuring system may be an effective screening method for identifying DNA damage response inhibitors that could eventually be used to develop novel anticancer drugs.