Cytotoxic and Proapoptotic Effects of Resveratrol in In Vitro Studies on Selected Types of Gastrointestinal Cancers.

Cancer diseases are currently one of the greatest health challenges in clinical medicine worldwide. Classic methods of treatment often lead to numerous side effects, including the development of multidrug resistance. For this reason, increasing hope is being placed on compounds of natural origin, mainly due to their pleiotropic effect on different types of cells, protective effect on normal cells and toxic effect on cancerous ones. The most studied group are the polyphenolic compounds, which include resveratrol. The effectiveness of polyphenols in the treatment and prevention of many diseases, including cancer of various origins, has become the basis of many scientific studies. The anticancer effect of resveratrol has been demonstrated at all stages of the carcinogenesis process. Additionally, whether administered by itself or in combination with cytostatics, it may play a significant role in the process of reversing multidrug resistance. A review of the effects of resveratrol in in vitro conditions proves that it has a stronger or weaker antiproliferative and proapoptotic effect on the cells of certain neoplasms of the gastrointestinal tract. Despite the differences in the effect of this compound on different types of cancer, a similar tendency can be observed especially regarding the correlation between the concentration of the compound and the incubation time on the one hand and the antitumour effect on the other hand. The information included in this review may prove helpful in planning in vivo and clinical studies in the future.

Effect of Resveratrol Treatment on Human Pancreatic Cancer Cells through Alterations of Bcl-2 Family Members.

Pancreatic cancers are among of the most lethal types of neoplasms, and are mostly detected at an advanced stage. Conventional treatment methods such as chemotherapy or radiotherapy often do not bring the desired therapeutic effects. For this reason, natural compounds are increasingly being used as adjuvants in cancer therapy. Polyphenolic compounds, including resveratrol, are of particular interest. The aim of this study is to analyze the antiproliferative and pro-apoptotic mechanisms of resveratrol on human pancreatic cells. The study was carried out on three human pancreatic cancer cell lines: EPP85-181P, EPP85-181RNOV (mitoxantrone-resistant cells) and AsPC-1, as well as the normal pancreatic cell line H6c7. The cytotoxicity of resveratrol in the tested cell lines was assessed by the colorimetric method (MTT) and the flow cytometry method. Three selected concentrations of the compound (25, 50 and 100 µM) were tested in the experiments during a 48-h incubation. TUNEL and Comet assays, flow cytometry, immunocytochemistry, confocal microscopy, real-time PCR and Western Blot analyses were used to evaluate the pleiotropic effect of resveratrol. The results indicate that resveratrol is likely to be anticarcinogenic by inhibiting human pancreatic cancer cell proliferation. In addition, it affects the levels of Bcl-2 pro- and anti-apoptotic proteins. However, it should be emphasized that the activity of resveratrol was specific for each of the tested cell lines, and the most statistically significant changes were observed in the mitoxantrone-resistant cells.

Synthesis, Immunosuppressive Properties, and Mechanism of Action of a New Isoxazole Derivative.

This work describes the synthesis of a new series of isoxazole derivatives, their immunosuppressive properties, and the mechanism of action of a representative compound. A new series of N'-substituted derivatives of 5-amino-N,3-dimethyl-1,2-oxazole-4-carbohydrazide (MM1⁻MM10) was synthesized in reaction of 5-amino-N,3-dimethyl-1,2-oxazole-4-carbohydrazide with relevant carbonyl compounds. The isoxazole derivatives were tested in several in vitro models using human cells. The compounds inhibited phytohemagglutinin A (PHA)-induced proliferation of peripheral blood mononuclear cells (PBMCs) to various degrees. The toxicity of the compounds with regard to a reference A549 cell line was also differential. 5-amino-N'-(2,4-dihydroxyphenyl)methylidene-N,3-dimethyl-1,2-oxazole-4-carbohydrazide (MM3) compound was selected for further investigation because of its lack of toxicity and because it had the strongest antiproliferative activity. The compound was shown to inhibit lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF α) production in human whole blood cell cultures. In the model of Jurkat cells, MM3 elicited strong increases in the expression of caspases, Fas, and NF-κB1, indicating that a proapoptotic action may account for its immunosuppressive action in the studied models.

Anticancer properties of ester derivatives of betulin in human metastatic melanoma cells (Me-45).

BACKGROUND: Betulinic acid and betulin are triterpenes that have anticancer properties in various types of cancer. Unfortunately, the bioavailability and the bio-distribution of betulinic acid and its metabolic precursor, betulin are very low because of poor solubility in aqueous buffers. METHODS: In this study, we examined the anticancer properties of the ester derivatives of betulin compared to their precursors in a malignant melanoma cell line. We assessed five amino acid esters of betulin. The compounds contained four basic amino acids-natural lysine (l-Lys-OH) and three of its derivatives (l-Dap-OH, l-Dab-OH, and l-Orn-OH)-and alanine (l-Ala-OH) as a negative control (amino acid without an amine group in the side chain). The derivatives were more soluble than their precursors (betulin and betulinic acid) in water. The betulin esters were tested in the malignant melanoma cell line Me-45. To evaluate the cytotoxicity, MTT test was performed after 24, 48 and 72 h of incubation with the test compounds at a concentration range of 0.75-100 µM. For analysis of the apoptotic activity, TUNEL assay was performed. Additionally, expression of caspase-3 and PARP-1 was investigated immunocytochemically. RESULTS: The highest biological activity was observed with the lysine ester. The results showed that the highest cytotoxicity and the highest number of positively stained nuclei in metastatic melanoma Me-45 cells were obtained after 72 h of incubation with betulin derivatives containing lysine and ornithine. CONCLUSIONS: The betulin ester derivatives showed enhanced antitumor activity compared to their non-modified precursors. Esters of betulin can be more potent anticancer agents than their precursor as a consequence of the rapid bioavailability and increased concentration in cancer cells.

DHMEQ enhances the cytotoxic effect of cisplatin and carboplatin in ovarian cancer cell lines.

Ovarian cancer (OvCa) is one of the most lethal gynaecological malignancies. It is diagnosed mostly in advanced stages. Due to a lack of appropriate early detection markers and non-ambiguous symptoms, the five-year survival rate is significantly reduced. Despite a primary good response to platinum-based therapy, approximately 70% of patients will develop a chemoresistance phenotype. The activation of the NF-κB signalling pathway plays a crucial role in this process. It is responsible for increasing cell viability, cell cycle progression and induces growth and migration of neoplastic cells. A few independent studies have yet suggested a high correlation between activation of NF-κB and poor outcome in OvCa patients. Thus, developing inhibitors of the NF-κB pathway has become a new target of cancer therapies. One of the promising compounds is DHMEQ (dehydroxymethylepoxyquinomicin). Our preliminary studies indicated that DHMEQ combined with cisplatin (CDDP) or carboplatin (CBP) enhanced apoptosis in the A2780 cell line and caused cell cycle arrest in the G2/M phase in the SKOV3 cell line, but not in the normal cell line MRC-5 pd19. Moreover, the combination of those agents caused decreased motility of cells, especially with the CBP. However, the invasion of cells was not changed significantly. The analysis of drug interactions using CompuSyn software has revealed that observed effect of the doses used in the study was antagonistic, but the DRI guidelines and in vitro observation of biological response indicate that a combination of DHMEQ with CDDP or CBP could be a novel proposal in ovarian cancer treatment.

Quercetin as a potential modulator of P-glycoprotein expression and function in cells of human pancreatic carcinoma line resistant to daunorubicin.

P-glycoprotein (P-gp) is one of the ABC transporters responsible for the resistance of several tumours to successful chemotherapy. Numerous agents are capable of interfering with the P-gp-mediated export of drugs but unfortunately most of them produce serious side effects. Some plant polyphenols, including the flavonol quercetin (Q), manifest anti-neoplastic activity mainly due to their influence on cell cycle control and apoptosis. Reports are also available which show that Q may intensify action of cytostatic drugs and suppress the multidrug resistance (MDR) phenomenon. The study aimed at determination if Q sensitizes cells resistant to daunorubicin (DB) through its effect on P-gp expression and action. The experiments were conducted on two cell lines of human pancreatic carcinoma, resistant to DB EPP85-181RDB and sensitive EPP85-181P as a comparison. Cells of both lines were exposed to selected concentrations of Q and DB, and then membranous expression of P-gp and its transport function were examined. The influence on expression of gene for P-gp (ABCB1) was also investigated. Results of the studies confirmed that Q affects expression and function of P-gp in a concentration-dependent manner. Moreover it decreased expression of ABCB1. Thus, Q may be considered as a potential modulator of P-gp.

A New Betulin Derivative Stimulates the Synthesis of Collagen in Human Fibroblasts Stronger than its Precursor.

BACKGROUND/AIM: The exploration of substances that stimulate collagen synthesis and retard the aging process of the skin is an active field of current research. The natural environment and plants used in traditional medicine have been a source of such substances. The aim of this study was to compare the stimulatory effect of betulin (BE), betulinic acid (BA) and the new derivative - betulin ester with diaminobutyl acid (BE-Dab-NH2) on collagen synthesis in human normal fibroblasts. MATERIALS AND METHODS: Primary fibroblast cultures were obtained from the gums of a healthy patient. The effect of the above-mentioned compounds was assessed by Sircol collagen assay, immunocytochemistry, and proliferation test. RESULTS: Fibroblasts cultured in the presence of BE-Dab-NH2 produced 6.85 times more collagen than control cells, 7.85 times more than those cultured in the presence of BA and 6.31 times more than those cultured in the presence of BE. An intense immunocytochemical reaction for collagen type I and III was found in fibroblasts cultured in the presence of BE-Dab-NH2 Conclusion: BE-Dab-NH2 stimulates significantly more collagen synthesis in normal human fibroblasts than its precursor.

Expression of genes and proteins of multidrug resistance in gastric cancer cells treated with resveratrol.

Multidrug resistance (MDR) is a notable problem in the use of chemotherapy. Therefore, studies aimed at identifying substances capable of overcoming resistance of cancer cells are required. Examples of these compounds are polyphenols, including resveratrol, that exert a range of various biological activities. The aim of the present study was to demonstrate the effect of 3,5,4'-trihydroxy-trans-stilbene (resveratrol) on the expression of ATP binding cassette subfamily B member 1, Annexin A1 (ANXA1) and thioredoxin (TXN) genes, and the proteins encoded by these genes, which are associated with MDR. The experiments were performed in human gastric cancer cell lines EPG85-257RDB (RDB) and EPG85-257RNOV (RNOV), which are resistant to daunorubicin and mitoxantrone, respectively, in addition to EPG85-257P (control), which is sensitive to cytostatic drugs. Cells were treated with 30 or 50 µM resveratrol for 72 h and changes in the expression levels of the genes were analysed with the use of a reverse transcription-quantitative polymerase chain reaction. The cellular levels of P-glycoprotein (P-gp), ANXA1 and TXN were evaluated using immunofluorescence and western blot analysis. Resveratrol in both concentrations has been shown to have a statistically significant influence on expression of the mentioned genes, compared with untreated cells. In RDB cells, resveratrol reduced the expression level of all analyzed genes, compared with untreated cells. Similar results at the protein level were obtained for P-gp and TXN. In turn, in the RNOV cell line, resveratrol reduced TXN expression at mRNA and protein levels, compared with untreated cells. The results of the present study indicate that resveratrol may reduce the resistance of cancer cells by affecting the expression of a number of the genes and proteins associated with MDR.

Classical and atypical resistance of cancer cells as a target for resveratrol.

The phenomenon of cancer cell resistance to chemotherapeutics is the main cause of insensitivity to anticancer therapy. Thus, the current challenge remains searching for substances sensitising the activity of cytostatic drugs. In this respect, resveratrol is a very promising therapeutic agent. It has pleiotropic effect on cancer cells, which can play a key role in numerous resistance mechanisms, both classical and atypical. The purpose of the present study was to assess the effect of resveratrol on the inhibition of human pancreatic cancer cell proliferation and on the level of cytostatic resistance-associated proteins. The study was performed on human pancreatic cancer cell lines EPP85-181P (control), EPP85-181RDB (daunorubicin resistance) and EPP85-181PRNOV (mitoxantrone resistance). The effect of resveratrol on the viability and proliferation of the studied cell lines was evaluated by SRB assay, whereas cell cycle arrest and cytostatic accumulation by FACS. Western blot analysis was used to determine the level of P-glycoprotein, topoisomerase II α and ß and immunofluorescence technique to visualise the proteins in the cells. Resveratrol inhibited proliferation of all studied cell lines. Phase-specific cell cycle arrest depended on the type of cancer cells. Resveratrol decreased the level and activity of P-gp in EPP85-181RDB cells. In EPP85-181PRNOV cells, expression of both TopoII isoforms increased in a statistically significant manner. The results of in vitro studies support the possibility of potential use of resveratrol in breaking cancer cell resistance to chemotherapeutic drugs.

Expression of metallothionein 3 in ductal breast cancer.

Metallothionein 3 (MT-3) has the ability to regulate the growth of nerve cells, but the significance of MT-3 expression outside the central nervous system and its participation in carcinogenesis have not yet been clarified. The aim of our study was to investigate the expression of MT-3 in ductal breast cancer and to determine its relationship with well-defined clinicopathological factors in this type of tumor. The study was conducted on 134 cases of invasive ductal breast carcinoma (IDC), 42 samples of non-malignant breast tissue (NMBT), and 26 cases of mastopathy. Moreover, selected breast cancer cell lines (MCF-7, SKBR-3, MDA-MB-231, BO2) and normal human breast epithelial cells (hTERT-HME1) were used. The expression of MT-3 was examined on the protein level using immunohistochemistry and on the mRNA level using real-time PCR. It was shown that the MT-3 protein in cells of IDC and mastopathy appeared in the cytoplasm as well as in the cell nuclei. Both the cytoplasmic and nuclear expression of MT-3 was significantly lower in IDC than in the mastopathies (p<0.0001 and p<0.001). However, no significant correlation was demonstrated between the level of MT-3 protein and the studied clinicopathological factors. The mRNA expression of MT-3 in IDC was also lower than in non­malignant breast tissue (p<0.0001). Furthermore, in the cases of IDC with lymph node metastasis, the level of MT-3 mRNA was significantly lower than in the cases without metastasis (p=0.0199). The expression of MT-3 mRNA in breast cancer cell lines was significantly lower than in the normal human breast epithelial cell line (p<0.001). These results suggest that MT-3 may play a role in the malignant transformation of breast epithelial cells and in tumor progression.

The new esters derivatives of betulin and betulinic acid in epidermoid squamous carcinoma treatment - In vitro studies.

BACKGROUND: Betulinic acid and betulin are triterpenes with documented cytotoxic properties toward various cell lines. Unfortunately both betulinic acid and its metabolic precursor, betulin, are very poorly soluble in aqueous buffers, thus their bioavailability and bio-distribution are insufficient in terms of medical applications. OBJECTIVE: To investigate the specific anticancer role of the newly synthesized betulin derivatives in human epidermoid carcinoma cells. METHODS: In the present study we synthesized five amino acid esters of betulin. For the synthesis we selected alanine (Boc-l-Ala-OH, negative control) and four basic amino acids - natural lysine (Boc-l-Lys(Boc)-OH) and three its unnatural derivatives (Boc-l-Dap(Boc)-OH, Boc-l-Dab(Boc)-OH, and Boc-l-Orn(Boc)-OH). Boc-protected amino acids were most convenient for the synthesis. All new esters have one (betulin-l-Ala-NH2) or two free amino groups which significantly increase their solubility in water and facilitate their transport through the cell membrane. It is worth noting that the biological activity of new esters of betulin is positive correlated with the length of the side chain of l-amino acid. The highest biological activity displayed compound containing lysine side chain (Lys, -CH2-CH2-CH2-CH2-NH2). Considering the biological activity, other derivatives can be set in the following series: Orn (-CH2-CH2-CH2-NH2)>Dab (-CH2-CH2-NH2)>Dap (-CH2-NH2)>Ala (CH3)>betulin. New betulin esters were tested in normal human keratinocytes (HaCaT) and human epidermoid carcinoma cells (A431). To assess cytotoxicity, MTT test was performed after 24, 48 and 72h of incubation with the test compounds at a concentration range of 0.75-100µM. In case of apoptotic activity, a TUNEL method and comet assay were performed. Additionally expression of caspase-3 and PARP1 was evaluated immunocytochemically. RESULTS: The highest cytotoxicity in cells induced skin cancer new compounds, particularly compound containing a lysine side chain (IC50=7µM) and ornithine (IC50=10µM). The highest number of apoptotic cells was observed in case incubation with compound containing Orn, Dab and Dap side chain. CONCLUSIONS: The new betulin ester derivatives display enhanced antitumor activity compared to their non-modified precursors. It is worth emphasizing their specific toxicity against epidermoid carcinoma cells.

Induction of apoptosis by EGCG in selected tumour cell lines in vitro.

One of the best recognised polyphenols of plant origin, epigallocatechin-3-gallate (EGCG) is contained mainly in green tea and in grapes. Studies performed in vivo and in vitro have demonstrated high probability of anti-neoplastic potential of the compound, due to its capacity to induce programmed cell death. The present studies were aimed at evaluation of apoptosis induction in cells of three selected tumour cell lines, subjected to action of various concentrations of EGCG. The experiment was performed on cultures of HEp-2 laryngeal carcinoma cells, LoVo colon carcinoma cells, HeLa cervical carcinoma cells and on normal myoepithelial cell line, HS. EGCG was found to induce apoptosis in cells of the examined neoplastic lines in a dose-related manner. Moreover, effect of EGCG on normal cells of HS line was found to be much less pronounced as compared to effects exerted on sensitive neoplastic cells.

The effects of quercetin vs cisplatin on proliferation and the apoptotic process in A549 and SW1271 cell lines in in vitro conditions.

Experience over several years has indicated that chemotherapy, even if widely used, does not always remain effective in the therapy of lung tumours and, in addition, is linked to serious side effects. In parallel, some plant polyphenols are known to exert a proapoptotic action on tumour cells while, in contrast, representing anti-cancerogenic anti-oxidants in living organisms. Our studies were aimed at comparing the effects of a polyphenol, quercetin, and cisplatin on cells of various types of lung cancer in in vitro conditions. In these studies we also attempted to define the relationship between the dose and the duration of the activity of the compounds. Cisplatin alone was found to induce only a small reaction in the cells, while in combination with quercetin its anti-proliferative and pro-apoptotic effects were amplified, depending upon the type of tumour, the dose and the duration of the drug's action.

In vitro effect of quercetin on human gastric carcinoma: targeting cancer cells death and MDR.

The benefits of plant polyphenols as chemotherapeutic agents are of great interest due to their possible anti-cancerogenic activities. Results available up to now suggest that flavonoid quercetin induces lethal effect in many types of tumours and may sensitize resistant cells to drugs. The aim of our study was to examine the effect of quercetin on human gastric carcinoma cells and to determine mode of its action. Parental EPG85-257P cell line and its daunorubicin-resistant variant EPG85-257RDB were used as cell models. Our data revealed that quercetin exerted antiproliferative impact on studied cells (with IC(50) value of 12 µM after 72 h), mainly through induction of apoptosis. In sensitive cells cytostatic drug and flavonoid had synergistic effects, in EPG85-257RDB cells quercetin acted as a chemosensitizer. Its impact on resistance mechanism involved decrease of P-glycoprotein expression, inhibition of drug transport and downregulation of ABCB1 gene expression. The results demonstrate that quercetin may be considered as a prospective drug to overcome classical resistance in gastric cancer cells.

Antiproliferative and pro-apoptotic effects of quercetin on human pancreatic carcinoma cell lines EPP85-181P and EPP85-181RDB.

Polyphenols are present in several edible plants and for many years induce high interest mainly due to their antioxidative and anti-inflammatory influence. At present, numerous studies are conducted on antineoplastic effects of the compounds. One of most effective biopolyphenols involves the flavonol quercetin. Our studies aimed at evaluation of antiproliferative and pro-apoptotic effects of quercetin alone and in combinations with daunorubicin on cells of human pancreatic carcinoma lines. The experiments were conducted on two cell lines, sensitive to daunorubicin EPP85-181P line, and its resistant variant EPP85-181RDB. Effect of studied substances on cell proliferation was detected using sulphorhodamine B (SRB) protein staining method. Apoptotic damage was estimated using comet and TUNEL techniques. Our data demonstrated that quercetin exerted cytotoxic action on cells of the both neoplastic cell lines in concentration-dependent manner. In the case of EPP85-181RDB cell line, quercetin seemed to sensitize resistant cells to daunorubicin. In parallel, the effect of both substances on the sensitive cell line was synergistic. Results of the studies confirmed that quercetin may probably break resistance of neoplastic cells to chemotherapy. On the other side, studied flavonol augmented action of cytostatic drug in case of sensitive tumour cells what suggest, that it might allow to decrease dosage of cytostatic drugs and reduce negative side effects of the treatment.