Upregulation of Fas/Fas ligand-mediated apoptosis by gossypol in an immortalized human alveolar lung cancer cell line

Bacterial endotoxin lipopolysaccharides regulate gene expression in human colon cancer cells

OBJECTIVE

Lipopolysaccharide (LPS) is a major cell wall component of gram-negative bacteria. Colon bacteria contribute to LPS which promotes colon cancer metastasis. The objective of this study was to survey the effect of LPS on cell viability and gene expression of 55 molecular targets in human colon cancer cells.

RESULTS

LPS did not affect the viability of COLO 225 cells under the culture conditions but affected the expression of a number of genes important in inflammatory responses and cancer development. LPS increased TTP family, GLUT family and DGAT1 mRNA levels but decreased DGAT2a and DGAT2b expression in the human colon cancer cells. LPS also increased COX2, CXCL1, ELK1, ICAM1, TNFSF10 and ZFAND5 but decreased BCL2L1, CYP19A1 and E2F1 mRNA levels in the colon cancer cells. These data suggest that LPS has profound effects on gene expression in human colon cancer cells.

Identification of Bcl2 as a Stably Expressed qPCR Reference Gene for Human Colon Cancer Cells Treated with Cottonseed-Derived Gossypol and Bioactive Extracts and Bacteria-Derived Lipopolysaccharides

Cottonseed contains many bioactive molecules including plant polyphenols. Cottonseed value might be increased by providing high-value bioactive polyphenols for improving nutrition and health. However, there was a lack of molecular evidence for cottonseed bioactivity in mammalian cells. One widely used method for evaluating the bioactivity of natural products is quantitative real-time-PCR (qPCR). The selection of stably expressed internal reference genes is a crucial task of qPCR assay for data analysis. The rationale for reference gene selection is that a lower standard deviation of the cycle of threshold (Cq) among the treatments indicates a more stable expression of the gene. The objective of this study was to select reference genes in human colon cancer cells (COLO 205) treated with cottonseed-derived gossypol and bioactive extracts along with bacterial endotoxin lipopolysaccharides (LPS). SYBR Green qPCR was used to analyze the mRNA levels of a wide range of biomarkers involved in glucose transport, lipid biosynthesis, inflammatory response, and cancer development. qPCR data (10,560 Cq values) were generated from 55 genes analyzed from 64 treatments with triplicate per treatment for each gene. The data showed that B-cell lymphoma 2 (Bcl2) mRNA was the most stable among the 55 mRNAs analyzed in the human colon cancer cells. Glyceraldehyde 3 phosphate dehydrogenase (Gapdh) and ribosome protein L32 (Rpl32) mRNAs were not good qPCR references for the colon cancer cells. These observations were consistent regardless of the treatment comparison between gossypol and LPS, glanded and glandless seed extracts, seed coat and kernel extracts, or treatment for 8 and 24 h. These results suggest that Bcl2 is a preferable reference gene for qPCR assays in human colon cancer cells treated with cottonseed-derived gossypol and bioactive extracts as well as LPS. The extensive qPCR results firmly support the conclusion that the Bcl2 gene is stably expressed at the mRNA level in the human colon cancer cells regardless of the treatment, suggesting that Bcl2 gene expression is not regulated at the mRNA level but at the post-transcriptional level. These results should facilitate studies designated to evaluate bioactivity on gene expression regulation by cottonseed molecules and other natural and synthetic molecules for nutrition and health uses.

The anti-ovarian carcinoma activity of L-amino acid oxidase from Crotalus adamanteus venom in vivo and in vitro

Snake venom L-Amino-acid oxidase (svLAAO) has become a critical research target in molecular biology and medical science since its widespread presence and diverse biological roles, including antitumor application. Our research confirmed that Crotalus adamanteus (C. adamanteus) venom LAAO exhibited potential anti-ovarian cancer activity both in vivo and in vitro. C. adamanteus venom LAAO significantly reduced viability of ovarian cancer cells and caused morphological changes that preceded cell death. The results of molecular biology experiments showed that C. adamanteus venom LAAO caused expression changes of genes related to apoptotic pathways either intrinsically or extrinsically in ovarian cancer cells. Animal experiments and histological analysis also proved that C. adamanteus venom LAAO could effectively inhibit the tissue damage caused by ovarian cancer, and animals treated with C. adamanteus venom LAAO showed higher survival time. Catalase blocked the major apoptosis induction of C. adamanteus venom LAAO on ovarian cancer cells, suggesting that the cytotoxicity of C. adamanteus venom LAAO on ovarian cancer cells was mainly mediated by H₂O₂. These results infer that C. adamanteus venom LAAO will have some advantages in new drug research and antitumor drug development in future.

Cottonseed extracts regulate gene expression in human colon cancer cells

Cotton plant provides economically important fiber and cottonseed, but cottonseed contributes 20% of the crop value. Cottonseed value could be increased by providing high value bioactive compounds and polyphenolic extracts aimed at improving nutrition and preventing diseases because plant polyphenol extracts have been used as medicinal remedy for various diseases. The objective of this study was to investigate the effects of cottonseed extracts on cell viability and gene expression in human colon cancer cells. COLO 225 cells were treated with ethanol extracts from glanded and glandless cottonseed followed by MTT and qPCR assays. Cottonseed extracts showed minor effects on cell viability. qPCR assay analyzed 55 mRNAs involved in several pathways including DGAT, GLUT, TTP, IL, gossypol-regulated and TTP-mediated pathways. Using BCL2 mRNA as the internal reference, qPCR analysis showed minor effects of ethanol extracts from glanded seed coat and kernel and glandless seed coat on mRNA levels in the cells. However, glandless seed kernel extract significantly reduced mRNA levels of many genes involved in glucose transport, lipid biosynthesis and inflammation. The inhibitory effects of glandless kernel extract on gene expression may provide a useful opportunity for improving nutrition and healthcare associated with colon cancer. This in turn may provide the potential of increasing cottonseed value by using ethanol extract as a nutrition/health intervention agent.

Physicochemical features, functional characteristics, and health benefits of cottonseed oil: a review

Vegetable oils have their specific physicochemical properties due to which they are playing vital role in human nutritional diet for health benefits. Cottonseed oil is obtained from various species of cotton seeds that are famous to be grown mainly for their fiber quality. The most prominently used specie is Gossypium hirsutum. It is obvious that the seeds of different variety of cotton vary as grown in diverse agroclimatic conditions with respect to oil, fats and protein contents. Cottonseed oil is routinely used for cooking and food manufacturing products. Cottonseed oil obtained after proper extraction/processing steps from crude state to refined oil in a variety of ways. Cotton crop is considered for their dual-use purpose, for fiber quality and oil production to promote health benefits in the world. Keeping in view the above facts, this review clearly demonstrated an overview about physicochemical and functional properties of cottonseed oil to promote health benefits associated with the use of this oil. The overall characteristics and all concerned health benefits of CSO will further improve their usefulness is a compact way. We have summarized a brief multi-dimensional features of CSO in all aspects up to the best of our knowledge for the end researchers who can further research in the respective aspect.

Gossypol decreased cell viability and down-regulated the expression of a number of genes in human colon cancer cells

Plant polyphenol gossypol has anticancer activities. This may increase cottonseed value by using gossypol as a health intervention agent. It is necessary to understand its molecular mechanisms before human consumption. The aim was to uncover the effects of gossypol on cell viability and gene expression in cancer cells. In this study, human colon cancer cells (COLO 225) were treated with gossypol. MTT assay showed significant inhibitory effect under high concentration and longtime treatment. We analyzed the expression of 55 genes at the mRNA level in the cells; many of them are regulated by gossypol or ZFP36/TTP in cancer cells. BCL2 mRNA was the most stable among the 55 mRNAs analyzed in human colon cancer cells. GAPDH and RPL32 mRNAs were not good qPCR references for the colon cancer cells. Gossypol decreased the mRNA levels of DGAT, GLUT, TTP, IL families and a number of previously reported genes. In particular, gossypol suppressed the expression of genes coding for CLAUDIN1, ELK1, FAS, GAPDH, IL2, IL8 and ZFAND5 mRNAs, but enhanced the expression of the gene coding for GLUT3 mRNA. The results showed that gossypol inhibited cell survival with decreased expression of a number of genes in the colon cancer cells.

Anti-inflammatory Effects of Gossypol on Human Lymphocytic Jurkat Cells via Regulation of MAPK Signaling and Cell Cycle

Gossypol, a natural polyphenolic compound extracted from cottonseed oil, has been reported to possess pharmacological properties via modulation cell cycle and immune signaling pathway. However, whether gossypol has anti-inflammatory effects against phytohemagglutinin (PHA)-induced cytokine secretion in T lymphocytes through similar mechanism remains unclear. Using the T lymphocytes Jurkat cell line, we found that PHA exposure caused dramatic increase in interleukin-2 (IL-2) mRNA expression as well as IL-2 secretion. All of these PHA-stimulated reactions were attenuated in a dose-dependent manner by being pretreated with gossypol. However, gossypol did not show any in vitro cytotoxic effect at doses of 5-20 μM. As a possible mechanism underlying gossypol action, such as pronounced suppression IL-2 release, robust decreased PHA-induced phosphorylation of p38 and c-Jun N-terminal kinase expressions was found with gossypol pretreatment, but not significant phosphorylation of extracellular signal-regulated kinase expression. Furthermore, gossypol could suppress the Jurkat cells' growth, which was associated with increased percentage of G1/S phase and decreased fraction of G2 phase in flow cytometry test. We conclude that gossypol exerts anti-inflammatory effects probably through partial attenuation of mitogen-activated protein kinase (phosphorylated JNK and p38) signaling and cell cycle arrest in Jurkat cells.

Effect of the BH3 Mimetic Polyphenol (-)-Gossypol (AT-101) on the in vitro and in vivo Growth of Malignant Mesothelioma

Malignant mesothelioma (MM) is a primary tumor arising from mesothelial cells. The survival of MM patients following traditional chemotherapy is poor, thus innovative treatments for MM are needed. (-)-gossypol (AT-101) is a BH3 mimetic compound which possesses anti-tumoral activity by targeting multiple signaling transduction pathways. Several clinical trials employing AT-101 have been performed and some of them are still ongoing. Accordingly, we investigated the in vitro effects of AT-101 on cell proliferation, cell cycle regulation, pro-survival signaling pathways, apoptosis and autophagy of human (MM-B1, H-Meso-1, and MM-F1) and mouse (#40a) MM cell lines. In addition, we explored the in vivo anti-tumor activities of AT-101 in a mouse model, in which the transplantation of MM cells induces ascites in the peritoneal space. AT-101 inhibited in vitro MM cells survival in a dose- and time-dependent manner and triggered autophagy, but the process was then blocked and was coincident with apoptosis activation. To confirm the effect of AT-101 in inducing the apoptosis of MM cells, MM cells were simultaneously treated with AT-101 and with the caspase inhibitor, Z-VAD-FMK. Z-VAD-FMK was able to significantly reduce the number of cells in the subG1 phase compared to the treatment with AT-101 alone. This result corroborates the induction of cell death by apoptosis following treatment with AT-101. Indeed, Western blotting results showed that AT-101 increases Bax/Bcl-2 ratio, modulates p53 expression, activates caspase 9 and the cleavage of PARP-1. In addition, the treatment with AT-101 was able to: (a) decrease the ErbB2 protein expression; (b) increase the EGFR protein expression; (c) affect the phosphorylation of ERK1/2, p38 and AKT; (d) stimulate JNK1/2 and c-jun phosphorylation. Our in vivo results showed that the intraperitoneal administration of AT-101 increased the median survival of C57BL/6 mice intraperitoneally transplanted with #40a cells and reduced the risk of developing tumors. Our findings may have important implications for the design of MM therapies by employing AT-101 as an anticancer agent in combination with standard therapies.

β-Bourbonene attenuates proliferation and induces apoptosis of prostate cancer cells

Sesquiterpenes have antitumor, anti-inflammation, and anti-fungal effects. β-bourbonene is a kind of sesquiterpene, but its pharmacological effect has not been studied. The present study was conducted in order to investigate the potential anticancer effects of β-bourbonene on human prostate cancer PC-3M cells. PC-3M cells were incubated with 0, 25, 50, 100 µg/ml of β-bourbonene. Cell Counting Kit-8 (CCK-8) detection showed that compared with the control group, β-bourbonene inhibited the growth of PC-3M cells in a dose-dependent manner. G0/G1 phase arrest was observed by β-bourbonene by using flow cytometry. TUNEL staining and Annexin V/PI dual-staining method revealed that apoptosis was found in cells with β-bourbonene treatment, and the quantity of apoptotic cells was increased with the elevation in concentration. The mRNA and protein expression levels of Fas and FasL in the drug-treatment group were significantly elevated. Furthermore, the western blot assay also indicated that with an increase in the concentration of β-bourbonene, the protein expression of Bax in the drug-treatment group was significantly elevated, while a decrease was identified in the protein expression of Bcl-2. Taken together, β-bourbonene can inhibit the proliferation and simultaneously, induce apoptosis and G0/G1 arrest of prostate cancer PC-3M cells, which may be realized by upregulation of mRNA expression of Fas and FasL, increase of Bax protein expression and decrease of Bcl-2 protein expression.

Long non-coding RNA (lncRNA) MAGI2-AS3 inhibits breast cancer cell growth by targeting the Fas/FasL signalling pathway

Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts shown to play important roles in tumourigenesis and tumour progression. Our study aimed to examine expression of the lncRNA MAGI2-AS3 in breast cancer and to explore its function in cancer cell growth. First, MAGI2-AS3 expression levels in clinical samples and cell lines were determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The functional significance of MAGI2-AS3 in cancer cell proliferation and apoptosis was then examined in vitro. Our results showed MAGI2-AS3 to be down-regulated in breast cancer tissues compared to normal adjacent tissues. Moreover, MAGI2-AS3 markedly inhibited breast cancer cell growth and increased expression of Fas and Fas ligand (FasL). In conclusion, our data suggest that MAGI2-AS3 expression is decreased in breast cancer and that MAGI2-AS3 plays an important role as a tumour suppressor by targeting Fas and FasL signalling. These results provide new insight into novel clinical treatments for breast cancer.

AT-101 acts as anti-proliferative and hormone suppressive agent in mouse pituitary corticotroph tumor cells

PURPOSE

Gossypol, a naturally occurring compound in cottonseeds, has anticancer effects against several tumor cell lines. It has been extensively studied in clinical trials and is well tolerated with a favorable safety profile. AT-101, a derivative of R (-)-gossypol, binds to Bcl-2 family proteins and induces apoptosis in vitro. Although transsphenoidal surgical excision of the pituitary corticotroph adenoma is the gold standard of care, it is not successful all the time. Medical therapy for Cushing's disease still remains a challenge for the clinicians. We aimed to investigate the cytotoxic and apoptotic effects of AT-101 in mouse pituitary corticotroph tumor AtT20 cells.

METHODS

Cytotoxic effect of AT-101 was assessed by XTT cell viability assay. Apoptosis was shown by measuring DNA fragmentation and Caspase-3/7 activity. Changes in mRNA expressions of apoptosis-related genes were investigated by qPCR array after treatment with AT-101. ACTH was measured by ACTH-EIA Kit.

RESULTS

AT-101 induced cytotoxicity and apoptosis in AtT20 cells. mRNA levels of pro-apoptotic genes such as TNFR-SF-10B, Bid, PYCARD, Caspase-8, Caspase-3, and Caspase-7 were induced by 2.0-, 1.5-, 1.7-, 1.5-, 1.6-, and 2-fold, respectively, in AtT20 cells by AT-101 treatment. Moreover, some of the anti-apoptotic genes such as BCL2L10, NAIP1, and PAK-7 were reduced by 2.1-, 2.3-, 4.0-fold, respectively, in AtT20 cells. AT-101 also decreased ACTH secretion significantly.

CONCLUSION

AT-101 induces apoptosis in mouse pituitary corticotroph tumor cells.

Effect of fraxetin on proliferation and apoptosis in breast cancer cells

The aim of the present study was to examine the effect of fraxetin on proliferation and apoptosis in the MCF-7 breast cancer cell line. Cell proliferation was measused using an MTT assay and 4′,6-diamidino-2-phenylindole (DAPI) staining was used to determine shrinkage and condensation. RT-PCR was used to examine the expression of factor-associated suicide (Fas) and Fas ligand (FasL) mRNA, and western blot analysis was used to examine Bax and Bcl-2 protein. MTT showed that the proliferation of MCF-7 cells was significantly inhibited by fraxetin in a dose-dependent manner. Fraxetin also induced significant morphological changes of MCF-7 cells, suggestive of apoptosis, whereas DAPI staining showed that fraxetin caused cell shrinkage and chromatin condensation. RT-PCR showed that the expression of Fas and FasL mRNA was upregulated by fraxetin and the western blot analysis revealed that Bax was upregulated and Bcl-2 was downregulated. In conclusion, fraxetin can inhibit the proliferation of MCF-7 cells, induce apoptosis, upregulate Fas, FasL and Bax, and downregulate Bcl-2 to induce apoptosis. These results support the potential therapeutic role for fraxetin in breast cancer.

The effects of hyperoside on apoptosis and the expression of Fas/FasL and survivin in SW579 human thyroid squamous cell carcinoma cell line

This study investigated the effects of hyperoside on apoptosis of human thyroid squamous cell carcinoma cells (SW579) and measured changes in the expression of known apoptosis regulatory players Fas/FasL and survivin. SW579 cells were treated with increasing concentrations of hyperoside. The cell proliferation inhibition rate was measured by MTT assay. Morphological changes in cells were observed by microscopy. Cell apoptosis was detected by flow cytometry using AV-PI double staining. The normalized expression levels of Fas and FasL mRNAs were detected by reverse transcription quantitative PCR (RT-qPCR), and the expression of the survivin protein was detected by western blotting. Our results showed that hyperoside significantly inhibited the activity of SW579 cells; obvious morphological changes were observed and apoptosis was induced in a dose-dependent manner. Hyperoside was shown to upregulate the expression of Fas and FasL mRNAs and downregulate the expression of the survivin protein. The results suggested that hyperoside can induce the apoptosis of the SW579 human thyroid squamous cell carcinoma cell line, and partially by upregulating the expression of Fas and FasL mRNAs and downregulating the expression of survivin protein in the process of apoptosis. Further studies on the use of hyperoside against cancer cells are required.

(±)-Gossypol induces apoptosis and autophagy in head and neck carcinoma cell lines and inhibits the growth of transplanted salivary gland cancer cells in BALB/c mice

Racemic Gossypol [(±)-GOS], composed of both (-)-GOS and (+)-GOS, is a small BH3-mimetic polyphenol derived from cotton seeds. (±)-GOS has been employed and well tolerated by cancer patients. Head and neck carcinoma (HNC) represents one of the most fatal cancers worldwide, and a significant proportion of HNC expresses high levels of antiapoptotic Bcl-2 proteins. In this study, we demonstrate that (±)-GOS inhibits cell proliferation and induces apoptosis and autophagy of human pharynx, tongue, and salivary gland cancer cell lines and of mouse salivary gland cancer cells (SALTO). (±)-GOS was able to: (a) decrease the ErbB2 protein expression; (b) inhibit the phosphorylation of ERK1/2 and AKT; (c) stimulate p38 and JNK1/2 protein phosphorylation. (±)-GOS administration was safe in BALB/c mice and it reduced the growth of transplanted SALTO cells in vivo and prolonged mice median survival. Our results suggest the potential role of (±)-GOS as an antitumor agent in HNC patients.

Tetrazolium violet induced apoptosis and cell cycle arrest in human lung cancer a549 cells

Tetrazolium violet is a tetrazolium salt and has been proposed as an antitumor agent. In this study, we reported for the first time that tetrazolium violet not only inhibited human lung cancer A549 cell proliferation but also induced apoptosis and blocked cell cycle progression in the G1 phase. The results showed that tetrazolium violet significantly decreased the viability of A549 cells at 5-15 μM. Tetrazolium violet -induced apoptosis in A549 cells was confirmed by H33258 staining assay. In A549, tetrazolium violet blocked the progression of the cell cycle at G1 phase by inducing p53 expression and further up-regulating p21/WAF1 expression. In addition, an enhancement in Fas/APO-1 and its two forms of ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), as well as caspase, were responsible for the apoptotic effect induced by tetrazolium violet. The conclusion of this study is that tetrazolium violet induced p53 expression which caused cell cycle arrest and apoptosis. These findings suggest that tetrazolium violet has strong potential for development as an agent for treatment lung cancer.

Bcl-2 antagonists: a proof of concept for CLL therapy

Defective apoptosis is a fundamental hallmark feature of CLL biology and is a major target of cancer therapy development. High levels of Bcl-2 family anti-apoptotic proteins are considered primarily responsible for inhibiting apoptosis in CLL cells. While several approaches were considered to selectively inhibit Bcl-2 family anti-apoptotic proteins, the discovery that gossypol binds and antagonizes anti-apoptotic effect of Bcl-2 family proteins was a major breakthrough in identifying specific Bcl-2 antagonists. The concept of mimicking BH3 domain emphasized the importance of Bcl-2 family-targeted therapy that can modulate the function of anti-apoptotic proteins. Although parent compound gossypol did not sustain in the clinic, its structural modifications led to the development of additional analogues that demonstrated improved efficacy and reduced toxicity in preclinical and clinical investigations. Proof of concept of this hypothesis was demonstrated by structure based BH3 mimetic ABT-737 that has shown greater cytotoxicity towards CLL cells both in pre-clinical models and clinical trials. Its oral compound ABT-263 has demonstrated the substantial susceptibility of chronic lymphocytic leukemia cells through Bcl-2 inhibition. Collectively, results of a Phase I Study of Navitoclax (ABT-263) in patients with relapsed or refractory disease warrants Bcl-2 as a valid therapeutic target in CLL. Importantly, molecules that mimic pro-apoptotic BH3 domains represent a direct approach to overcoming the protective effects of anti-apoptotic proteins such as Mcl-1, Bcl-2 and Bcl-XL.

Combination therapy with gossypol reveals synergism against gemcitabine resistance in cancer cells with high BCL-2 expression

Although gemcitabine is highly active in several cancer types, intrinsic and acquired drug resistance remains a major challenge. Overexpression of Bcl-2 has been associated with gemcitabine resistance. The aim of this study is to determine whether gossypol can overcome gemcitabine resistance in cell lines with high level of Bcl-2 expression in combination drug therapy. Our study demonstrated that in 10 cell lines derived from different cancers, high Bcl-2 baseline expression was observed in cell lines that were resistant to gemcitabine (GEM-R). Furthermore, synergistic effect of combination therapy was observed in gemcitabine-resistant (GEM-R) cell lines with high Bcl-2 expression, but not in a gemcitabine-sensitive (GEM-S) cell lines regardless of Bcl-2 expression. Gossypol treatment resulted in the decrease of anti-apoptotic genes such as Bcl-2 and Bcl-xl and an upregulation of the pro-apoptotic gene, Noxa. Furthermore, the addition of gossypol to gemcitabine resulted in lower expressions of anti-apoptotic genes compared to gemcitabine alone. Gene expression profiling in GEM-R and GEM-S cell lines suggest that anti-apoptotic genes such as pAkt and PI3KR2 may play important role in gemcitabine resistance, while pro-apoptotic Bcl-2 related genes (Bad, Caspase-6 and Calpain-1) may regulate synergistic interaction in combination therapy.

The role of COX-2/PGE2 in gossypol-induced apoptosis of colorectal carcinoma cells

Our previous study showed that gossypol (GOS) exhibits potent cytotoxic effects via apoptosis induction against human colorectal carcinoma cells; however, the role of cyclooxygenase (COX)-2/prostaglandin (PG)E(2) on GOS-induced apoptosis is still unknown. In the present study, 12-O-tetradecanoylphorbol-13-acetate (TPA) addition significantly inhibited GOS-induced apoptosis in human colorectal carcinoma HT-29 cells in accordance with inducing COX-2 protein/PGE(2) production. TPA inhibition of GOS-induced apoptosis was blocked by adding protein kinase (PK)C inhibitors including staurosporine (ST), GF109203X (GF), and H7, characterized by the occurrence of cleaved caspase 3 proteins and a decrease in COX-2 protein/PGE(2) production in HT-29 cells. The addition of COX activity inhibitors, including NS398 (NS), aspirin (AS), diclofenac (DI), and indomethacin (IN), suppressed TPA protection of GOS-induced apoptosis with decreased PGE(2) production in HT-29 cells. Application of PGE(2), but not it analogs PGD(2), PGJ(2), or PGF(2α), protected HT-29 cells from GOS-induced DNA ladders, and the E-prostanoid (EP(1)) receptor agonist, 17PT-PGE(2), mimicked the protection induced by PGE(2), whereas the selective EP(2) receptor agonist, butaprostol (BUT), the EP(3) receptor agonist, sulprostol (SUL), and the EP(4) receptor agonist, PGE(1) alcohol (PGE(1)), showed no significant effects on GOS-induced apoptosis in HT-29 cells. PGE(2) 's protection against GOS-induced apoptosis was reversed by adding the selective EP(1) receptor antagonist, SC-19220. Furthermore, GOS had an effective apoptotic effect on COLO205 colorectal carcinoma cells which expressed undetectable level of endogenous COX-2 protein than HT-29 cells, and the decreased COX-2 protein level via COX-2 siRNA or addition of COX-2 activity inhibitor NS significantly elevated GOS-induced cell death in HT-29 cells. COLO205-T cells were established through sustained TPA incubation of COLO205 cells, and COLO205-T cells showed a lower sensitivity to GOS-induced cell death with increased COX-2 (not Bcl-2 and Mcl-1) protein than parental COLO-205 cells. A decrease in COX-2 protein expression in COLO205-T cells by COX-2 siRNA transfection or enhanced GOS-induced cell death according to MTT assay and DNA integrity assay. The notion of COX-2/PGE(2) activation against GOS-induced apoptosis in colon carcinoma cells was demonstrated, and the combination of GOS and COX-2 inhibitors to treat colon carcinoma possesses clinical potential worthy of further investigation.

ApoG2 induces cell cycle arrest of nasopharyngeal carcinoma cells by suppressing the c-Myc signaling pathway

BACKGROUND

apogossypolone (ApoG2) is a novel derivate of gossypol. We previously have reported that ApoG2 is a promising compound that kills nasopharyngeal carcinoma (NPC) cells by inhibiting the antiapoptotic function of Bcl-2 proteins. However, some researchers demonstrate that the antiproliferative effect of gossypol on breast cancer cells is mediated by induction of cell cycle arrest. So this study was aimed to investigate the effect of ApoG2 on cell cycle proliferation in NPC cells.

RESULTS

We found that ApoG2 significantly suppressed the expression of c-Myc in NPC cells and induced arrest at the DNA synthesis (S) phase in a large percentage of NPC cells. Immunoblot analysis showed that expression of c-Myc protein was significantly downregulated by ApoG2 and that the expression of c-Myc's downstream molecules cyclin D1 and cyclin E were inhibited whereas p21 was induced. To further identify the cause-effect relationship between the suppression of c-Myc signaling pathway and induction of cell cycle arrest, the expression of c-Myc was interfered by siRNA. The results of cell cycle analysis showed that the downregulation of c-Myc signaling pathway by siRNA interference could cause a significant arrest of NPC cell at S phase of the cell cycle. In CNE-2 xenografts, ApoG2 significantly downregulated the expression of c-Myc and suppressed tumor growth in vivo.

CONCLUSION

Our findings indicated that ApoG2 could potently disturb the proliferation of NPC cells by suppressing c-Myc signaling pathway. This data suggested that the inhibitory effect of ApoG2 on NPC cell cycle proliferation might contribute to its use in anticancer therapy.

Gossypol--a polyphenolic compound from cotton plant

Gossypol (C(30)H(30)O(8)) is a polyphenolic compound derived from the cotton plant (genus Gossypium, family Malvaceae). The presence of six phenolic hydroxyl groups and two aldehydic groups makes gossypol chemically reactive. Gossypol can undergo Schiff base formation, ozonolysis, oxidation, and methylation to form gossypol derivatives. Gossypol and its derivatives have been the target of much research due to their multifaceted biological activities including antifertility, antivirus, anticancer, antioxidant, antitrypanosomal, antimicrobial, and antimalarial activities. Because of restricted rotation of the internaphthyl bond, gossypol is a chiral compound, which has two atropisomers (i.e., (+)- and (-)-gossypol) that exhibit different levels of biological activities. This chapter covers the physiochemical properties, analyses, biological properties, and agricultural and clinical implications of gossypol.

Gossypol, a BH3 mimetic, induces apoptosis in chronic lymphocytic leukemia cells

Gossypol, a cottonseed extract derivative, acts as a BH3-mimetic, binding to the BH3 pocket of antiapoptotic proteins and displacing pro-death partners to induce apoptosis. However, knowledge on the molecular underpinnings of its downstream effects is limited. Since chronic lymphocytic leukemia (CLL) cells express high levels of antiapoptotic proteins that act as a survival mechanism for these replicationally quiescent lymphocytes, we investigated whether gossypol induces apoptosis in these cells and what mechanism underlies gossypol-mediated cytotoxicity. Gossypol induced cell death in a concentration- and time-dependent manner; 24-hour incubation with 30 microM gossypol resulted in 50% cell death (median; range, 10%-80%; n = 47) that was not abrogated by pan-specific caspase inhibitor. Starting at 4 hours, the mitochondrial outer membrane was significantly permeabilized (median, 77%; range, 54%-93%; n = 15). Mitochondrial outer membrane permeabiliztaion (MOMP) was concurrent with increased production of reactive oxygen species (ROS); however, antioxidants did not abrogate gossypol-induced cell death. Mitochondrial membrane permeabilization was also associated with loss of intracellular adenosine triphosphate (ATP), activation of BAX, and release of cytochrome c and apoptosis-inducing factor (AIF), which was translocated to the nucleus. Blocking AIF translocation resulted in a decreased apoptosis, suggesting that AIF contributes to gossypol-mediated cytotoxicity in CLL lymphocytes.

(-)Gossypol and its combination with imatinib induce apoptosis in human chronic myeloid leukemic cells

Chronic myeloid leukemia (CML) is characterized by the presence of chimeric protein BCR-ABL associated with high tyrosine kinase (TK) activity, which leads to cell tumorogenicity, resistance to apoptosis, and differentiation. Gossypol is a natural polyphenolic compound isolated from cottonseed and has antiproliferative activity in a variety of cancer cell lines. (-)Gossypol is proved the potent component. Here we examined the growth inhibitory effect of (-)gossypol and its combination with imatinib in K562 cells. (-)Gossypol inhibited cell growth, promoted apoptosis, induced DeltaPsim loss, and cytochrome C release. Furthermore, (-)gossypol had a synergistic inhibitory effect on growth in K562 cells when combined with imatinib. Enhanced apoptosis, cytochrome C release, and caspase 3 cleavage as well as noticeable decrease of Mcl-1 and Bcl-XL were observed in K562 cells treated with both (-)gossypol and imatinib. These results suggest that (-)gossypol induced apoptosis in K562 cells through a mitochondria pathway and that the combination of imatinib and (-)gossypol might be an effective treatment for CML.

Resistance to Fas-mediated apoptosis in malignant tumours is rescued by KN-93 and cisplatin via downregulation of c-FLIP expression and phosphorylation

1. The purpose of the present study was to investigate the molecular mechanisms that control tumour cell resistance and to search for molecules that could overcome Fas ligand (FasL) or CH-11 resistance in certain tumours, including glioma and melanoma. 2. Twelve tumour cell lines were examined for their sensitivity to CH-11-induced apoptosis and then two of each of the CH-11-sensitive and -resistant tumour cell lines were analysed for Fas-mediated death-inducing signalling complex (DISC). The calmodulin kinase II (CaMKII) inhibitor KN-93 and the chemotherapeutic drug cisplatin were used to treat resistant cells; the effects of these two drugs on CH-11-resistant tumour cells were investigated. 3. In CH-11-sensitive tumour cells, apoptosis-initiating caspase 8 and caspase 10 were recruited to the DISC, where they became activated through autocatalytic cleavage, leading to apoptosis through cleavage of downstream substrates, such as caspase 3 and DNA fragmentation factor 45. 4. In CH-11-resistant cells, cellular Fas-associated death domain-like interleukin-1b-converting enzyme inhibitory protein (c-FLIP) proteins were recruited to the DISC, resulting in inhibition of caspase 8 and caspase 10 cleavage. The c-protein expression and phosphorylation of FLIP and CaMKII protein and enzyme activity were upregulated in resistant cells. Treatment of resistant cells with 100 micromol/L KN-93 and 10 microg/mL cisplatin downregulated c-FLIP expression, inhibited c-FLIP phosphorylation and rescued CH-11 sensitivity. 5. In conclusion, KN-93 and cisplatin inhibit c-FLIP protein expression and phosphorylation restores CH-11-induced apoptosis in tumour cells. tHe present study provides evidence for the use of a new combination therapeutic strategy in the treatment of malignant tumours.

Streptococcal pyrogenic exotoxin B-induced apoptosis in A549 cells is mediated through alpha(v)beta(3) integrin and Fas

Our previous work suggested that streptococcal pyrogenic exotoxin (SPE) B-induced apoptosis is mediated through a receptor-like mechanism. In this study, we have identified alpha(v)beta(3) and Fas as the SPE B receptors for this function. The SPE B fragment without the RGD motif and G308S, a SPE B mutant with the RSD motif, induced less apoptosis than did native SPE B, suggesting that the RGD motif is critical for SPE B-induced apoptosis. Fluorescein isothiocyanate-SPE B binding assays and immunoprecipitation analysis showed that SPE B specifically interacted with alpha(v)beta(3). Anti-alpha(v)beta(3) antibody partially inhibited SPE B-induced apoptosis but had no effect on G308S-induced apoptosis. In addition, Fas binding to SPE B was verified in an affinity column and an immunoprecipitation analysis. Anti-Fas antibody inhibited SPE B- and G308S-induced apoptosis in a dose-dependent manner, suggesting that Fas-mediated SPE B-induced apoptosis also occurs RGD independently. Both anti-alpha(v)beta(3) and anti-Fas antibodies synergistically inhibited SPE B-induced apoptosis. The apoptotic cascades were activated by SPE B and G308S, with a little delay by the latter. After SPE B binding, the cell surface level of alpha(v)beta(3), but not of Fas, was decreased. The decreased alpha(v)beta(3) level was restored by treatment with the proteasome inhibitor MG132, suggesting a SPE B-mediated endocytosis of integrin alpha(v)beta(3) via the ubiquitin-proteasome system. Taken together, our results demonstrate that SPE B-induced apoptosis is mediated through alpha(v)beta(3) integrin and Fas in a synergistic manner.

Gossypol reduction of tumor growth through ROS-dependent mitochondria pathway in human colorectal carcinoma cells

Among 13 different cell lines, gossypol (GOS) showed the most potent cytotoxic effect against human colorectal carcinoma cells including HT29, COLO205, COLO320HSR and COLO320DM cells according to an MTT assay. The cytotoxic effect of GOS was mediated by its induction of apoptosis as characterized by the occurrence of DNA ladders, apoptotic bodies and chromosome condensation in both COLO205 and HT29 cells. Activation of caspase 3, 6, 8 and 9, but not caspase 1, accompanied by the appearance of cleaved fragments of PARP (85 kDa), and caspase 3 (p17/p15), was identified in GOS-treated cells. Decreases in Bcl-xL and phosphorylated Bad proteins were found in GOS-treated cells. GOS induction of ROS production was detected by in vitro plasmid digestion, and an increase in the intracellular peroxide level was observed in GOS-treated COLO205 cells by the DCHF-DA assay. Antioxidants including N-acetyl-L-cysteine (NAC), catalase (CAT), tempol (TEM) and melatonin (MEL), but not allopurinol (ALL), pyrrolidine dithiocarbamate (PDTC) or diphenylene iodonium (DPI), significantly inhibited GOS-induced Reactive oxygen species (ROS) production through blocking the occurrence of apoptosis. GOS induced mitochondrial dysfunction characterized by a loss of the mitochondria membrane potential via DiOC6 staining, and the release of cytochrome c (Cyt c) and apoptosis-inducing factor (AIF) from mitochondria to the cytoplasm was observed. Removing mitochondria by ethidium bromide (EtBr) treatment significantly reduced the apoptotic effect of GOS in COLO205 cells. Furthermore, an intraperitoneal injection of GOS or gossypol acetic acid (GAA) significantly reduced the growth of colorectal carcinoma induced by a subcutaneous injection of COLO205 cells in nude mice. Results of the present study provide the first evidences demonstrating the in vitro and in vivo antitumor effects of GOS via an ROS-dependent mitochondrial apoptosis in colorectal carcinoma.

Radiosensitization of tumour cell lines by the polyphenol Gossypol results from depressed double-strand break repair and not from enhanced apoptosis

PURPOSE

New drugs are needed to increase the efficiency of radiotherapy in order to improve the therapeutic outcome of tumour patients. In this respect, the polyphenol Gossypol might be of interest, because of its effect on apoptosis and DNA repair, which is either mediated directly or indirectly via the inositol phosphate metabolism. It was investigated, whether these effects result in enhanced radiosensitivity of tumour cells.

MATERIAL AND METHODS

Tumour cell lines investigated: A549, FaDu, H1299, MCF7 and Du145. Cell cycle distribution was determined by FACS analysis, apoptosis was measured by DAPI staining and caspase3/7 activity. Double-strand breaks (DSB) were investigated via gammaH2AX-foci and cell survival by colony formation assay. The level of inositol phosphates was determined by HPLC, protein expression by Western blot.

RESULTS

In A549 cells, Gossypol at concentrations 1microM strongly affects proliferation with only a modest arrest in the G1-phase, but with no increase in the fraction of apoptotic cells or the number of additional DSB. Additional DSB were only seen in FaDu cells, where Gossypol (2microM) was extremely toxic with a plating efficiency <0.002. When combined with irradiation, incubation with Gossypol (1-2microM) was found to result in an enhanced radiosensitivity with, however, a substantial variation. While there was a strong radiosensitization for FaDu and Du145 cells, there was an intermediate response for A549 cells, but almost no effect for H1299 and MCF7 cells. This sensitization was not caused from an elevated rate of apoptosis, but primarily resulted from reduced DSB repair capacity. The reduction in DSB repair could be ascribed neither to changes in the level of repair proteins relevant for non-homologous end-joining (Ku70, Ku80, DNA-PKcs) nor to changes in the level of higher phosphorylated inositols, whereby the latter were even found to be enhanced by Gossypol.

CONCLUSIONS

For some tumour cell lines treatment with low concentrations of Gossypol can be used to inhibit DSB repair capacity and with that to increase the cellular radiosensitivity.

Differential growth inhibition and induction of apoptosis by gossypol between HCT116 and HCT116/Bax(-/-) colorectal cancer cells

1. Bax is a very important pro-apoptosis molecule. HCT116/Bax(-/-) cells do not express the pro-apoptosis Bcl-2 family member, Bax. In the present study, the anticancer effects of gossypol on HCT116 and HCT116/Bax(-/-) cells were compared in terms of inhibition of cell growth, inhibition of colony formation and induction of apoptosis. 2. Following treatment with concentrations more than 20 micromol/L gossypol, only slight differences (not significant) were seen between HCT116 and HCT116/Bax(-/-) cells in terms of the inhibition of cell growth and induction of apoptosis. No difference was seen in the inhibition of colony formation. Gossypol had no effect at concentrations < 2 micromol/L. The only effective concentration of gossypol to result in differences between HCT116 and HCT116/Bax(-/-) cells was 5 micromol/L. However, even at this concentration, Bax deficiency did not result in complete abolition of gossypol-induced growth inhibition or apoptosis. Exposure of cells to 5 micromol/L gossypol for 24 h did not cause any significant difference in the activation of caspase 2 between HCT116 and HCT116/Bax(-/-) cells; however, activation of caspase 3, 8 and 9 was significantly elevated in HCT116 cells, with the effect on caspase 3 activation being the greatest, compared with HCT116/Bax(-/-) cells. 3. These findings suggest that the contribution of Bax to gossypol-induced growth inhibition and apoptosis is dose dependent and that gossypol-induced apoptosis requires activation of caspase 3, 8, and 9.

Gossypol induces apoptosis in human PC-3 prostate cancer cells by modulating caspase-dependent and caspase-independent cell death pathways

The rate of gossypol-induced apoptosis does not correlate very well with the same dose of gossypol-induced cell growth inhibition, indicating an anti-proliferative effect of gossypol. Using a co-immunoprecipitation assay, it was observed that the level of Bcl-X(L) protein bound to Bax was clearly lower than that of Bcl-2 protein at 5 micro M of gossypol treatment, and the level of Bim protein bound to Bcl-X(L) was lowered at 20 micro M of gossypol treatment for 24 h, implicating that gossypol inhibits the heterodimerization of Bcl-X(L) with Bax and Bim. Gossypol-induced apoptosis is partly suppressed by as low as 0.5 micro M, but not abolished by as high as 50 micro M of a broad range caspase inhibitor, Z-VAD-FMK, suggesting that gossypol-induced apoptosis is both caspase-dependent and -independent. Furthermore, the release of apoptosis inducing factor (AIF), which triggers caspase-independent apoptosis, from mitochondria to cytosol was observed in PC-3 cells exposed to gossypol treatment. In conclusion, gossypol inhibits the proliferation and induces apoptosis in PC-3 cells. Gossypol-induced apoptosis is, at least, through inhibiting the heterodimerization of Bcl-X(L)/Bcl-2 with pro-apoptosis molecules, followed by a caspase-dependent and -independent process which involves the release of AIF from the mitochondria to cytosol.

Safrole oxide induces apoptosis by activating caspase-3, -8, and -9 in A549 human lung cancer cells

Previously we found that 3,4-(methylenedioxy)-1-(2',3'-epoxypropyl)-benzene (safrole oxide) induced a typical apoptosis in A549 human lung cancer cells. In this study, we further investigated which caspases were activated by safrole oxide during the apoptosis. The data showed that the activity of caspase-3, -8, and -9 was significantly enhanced by the compound, which suggested that safrole oxide might be used as a caspase promoter to initiate lung cancer cell apoptosis.

Five loci, SLT1 to SLT5, controlling the susceptibility to spontaneously occurring lung cancer in mice

A series of linkage studies was previously conducted to identify quantitative trait loci associated with chemically induced lung tumors. However, little is known of genetic susceptibility to spontaneously occurring lung tumorigenesis (SLT) in mice. In this study, we did a whole-genome linkage disequilibrium analysis for susceptibility to SLT in mice using approximately 135,900 single-nucleotide polymorphisms (SNPs) from the Roche and Genomic Institute of the Novartis Research Foundation SNP databases. A common set of 13 mouse strains was used, including 10 resistant strains (129X1/SvJ, AKR/J, C3H/HeJ, C57BL/6J, DBA/2J, NZB/BlnJ, CAST/EiJ, SPRET/EiJ, SM/J, and LP/J) and 3 susceptible strains (A/J, BALB/cJ, and NZW/LaCJ). Fisher exact test was used to assess the association between individual SNPs and susceptibility to SLT. Five regions, SLT1 to SLT5, were mapped on chromosomes 6, 7, 8, 19, and X, respectively. SLT1 to SLT5 showed a significant association with SLT under the empirical threshold (P < or = 0.004) derived from permutation tests. SNP versus SNP association tests indicated that these SLT regions were unlikely to be caused by population substructure. Thus, SLT1 to SLT5 seem to be novel loci controlling the susceptibility to spontaneously occurring lung cancer in mice. Our results provide, for the first time, an insight into the genetic control of spontaneously occurring lung tumorigenesis.

Investigations on gossypol: past and present developments

Gossypol has received significant attention as a result of its potential therapeutic application as a male antifertility agent. Furthermore, recent research examining the biological activity of gossypol has revealed a number of other promising lines of enquiry. These have focused on the antitumour, antiviral and antioxidant actions of the compound in various disease states. This article provides an overview of the studies on the biological activity of gossypol, with particular attention paid to the mechanisms of its activity and its prospect as a medicinal product.