Effects of combining Taxol and cyclooxygenase inhibitors on the angiogenesis and apoptosis in human ovarian cancer xenografts

Synergistic effects of green tea extract and paclitaxel in the induction of mitochondrial apoptosis in ovarian cancer cell lines

BACKGROUND

Green tea is a natural compound with anti-neoplastic properties. Paclitaxel (PTX) is a natural anti-tumor medication used to manage patients with advanced ovarian cancer. This manuscript evaluated the cytotoxic effects of green tea extract combined with PTX drug in two human ovarian cancer cell lines (p53-negative cell line, SKOV-3; and mutant type p53 cell line, OVCAR-3) and underlying mechanisms.

METHODS

The human ovarian cancer cell lines were treated with green tea extract, PTX, and green tea plus PTX for 24 h, and cell viability was assessed using the MTT method. Flow cytometric analyses were carried out to detect apoptosis. For the apoptotic process, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting analysis were applied to study pAkt, Bax, Bcl-2, Cytochrome C (Cyt-C), cleaved-caspase-3, and cleaved-caspase-9 levels after drug treatments.

RESULTS

Our results pointed out that various green tea (25 and 50 µg/ml) concentrations combined with PTX (20 and 40 µg/ml) synergistically inhibited cell viability of cancer cells more than green tea or PTX alone after 24 h of treatment. Also, green tea and PTX combination induced apoptosis in ovarian cancer cells by blocking the phosphorylation of Akt and the expression of Bcl-2 while inducing Bax, Cyt-C, cleaved-caspase 3, and cleaved-caspase 9.

CONCLUSION

Our results showed that the combination of green tea and PTX could be more potent than the individual drug to induce cytotoxicity and apoptosis in ovarian cancer cells.

The Role of Eicosanoids in Gynecological Malignancies

Eicosanoids, bio-active lipid molecules, evoke a multitude of biological effects that directly affect cancer cells and indirectly affect tumor microenvironment. An emerging role has been shown for eicosanoids in the pathogenesis of gynecological malignancies which include cancers of the vulva, vagina, cervix, uterine, and ovary. Eicosanoid biosynthesis pathways start at the metabolism of phospholipids by phospholipase A2 then proceeding to one of three pathways: the cyclooxygenase (COX), lipoxygenase (LOX), or P450 epoxygenase pathways. The most studied eicosanoid pathways include COX and LOX; however, more evidence is appearing to support further study of the P450 epoxygenase pathway in gynecologic cancers. In this review, we present the current knowledge of the role of COX, LOX and P450 pathways in the pathogenesis of gynecologic malignancies. Vulvar and vaginal cancer, the rarest subtypes, there is association of COX-2 expression with poor disease specific survival in vulvar cancer and, in vaginal cancer, COX-2 expression has been found to play a role in mucosal inflammation leading to disease susceptibility and transmission. Cervical cancer is associated with COX-2 levels 7.4 times higher than in healthy tissues. Additionally, HPV elevates COX-2 levels through the EGFR pathway and HIV promotes elevated COX-2 levels in cervical tissue as well as increases PGE2 levels eliciting inflammation and progression of cancer. Evidence supports significant roles for both the LOX and COX pathways in uterine cancer. In endometrial cancer, there is increased expression of 5-LOX which is associated with adverse outcomes. Prostanoids in the COX pathway PGE2 and PGF2α have been shown to play a significant role in uterine cancer including alteration of proliferation, adhesion, migration, invasion, angiogenesis, and the inflammatory microenvironment. The most studied gynecological malignancy in regard to the potential role of eicosanoids in tumorigenesis is ovarian cancer in which all three pathways have shown to be associated or play a role in ovarian tumorigenesis directly on the tumor cell or through modulation of the tumor microenvironment. By identifying the gaps in knowledge, additional pathways and targets could be identified in order to obtain a better understanding of eicosanoid signaling in gynecological malignancies and identify potential new therapeutic approaches.

Expression levels of ARHI and Beclin1 in thyroid cancer and their relationship with clinical pathology and prognosis

Expression levels of autophagy-related genes ARHI and Beclin1 in thyroid cancer and their relationship with clinical pathology and prognosis were investigated. The expression levels of ARHI and Beclin1 proteins in 80 cases of thyroid cancer and adjacent tissues were detected by western blot analysis. According to the expression levels of ARHI and Beclin1, low- and high-expression groups were determined and the relationship of the expression levels with the pathological parameters and prognosis in thyroid cancer was compared between the two groups. The correlation between the ARHI and Beclin1 protein expression level was analyzed by Pearsons correlation analysis. The levels of ARHI and Beclin1 proteins in thyroid cancer tissues were significantly lower than those in adjacent tissues (P<0.05). There was a significant difference in the expression levels of ARHI and Beclin1 in terms of pathological stage and differentiation degree of cancer tissues (P<0.001); however, there was no significant difference in the expression levels of ARHI and Beclin1 for different types of cancer tissues (P>0 05). There was a positive correlation between the expression levels of Beclin1 and ARHI (r=0.5187, P<0.001). The 3-year survival rates of patients with low-expression level of ARHI and Beclin1 proteins were significantly lower than those of patients with high expression (P<0.05). In conclusion, the expression levels of Beclin1 and ARHI were low in thyroid cancer, and were significantly associated with the pathological stage, differentiation degree and prognosis in thyroid cancer. Beclin1 and ARHI can be used as predictors for the development and prognosis of thyroid cancer.

Antiangiogenic Effects of Coumarins against Cancer: From Chemistry to Medicine

Angiogenesis, the process of formation and recruitment of new blood vessels from pre-existing vessels, plays an important role in the development of cancer. Therefore, the use of antiangiogenic agents is one of the most critical strategies for the treatment of cancer. In addition, the complexity of cancer pathogenicity raises the need for multi-targeting agents. Coumarins are multi-targeting natural agents belonging to the class of benzopyrones. Coumarins have several biological and pharmacological effects, including antimicrobial, antioxidant, anti-inflammation, anticoagulant, anxiolytic, analgesic, and anticancer properties. Several reports have shown that the anticancer effect of coumarins and their derivatives are mediated through targeting angiogenesis by modulating the functions of vascular endothelial growth factor as well as vascular endothelial growth factor receptor 2, which are involved in cancer pathogenesis. In the present review, we focus on the antiangiogenic effects of coumarins and related structure-activity relationships with particular emphasis on cancer.

Cyclooxygenase-1 (COX-1) and COX-1 Inhibitors in Cancer: A Review of Oncology and Medicinal Chemistry Literature

Prostaglandins and thromboxane are lipid signaling molecules deriving from arachidonic acid by the action of the cyclooxygenase isoenzymes COX-1 and COX-2. The role of cyclooxygenases (particularly COX-2) and prostaglandins (particularly PGE₂) in cancer-related inflammation has been extensively investigated. In contrast, COX-1 has received less attention, although its expression increases in several human cancers and a pathogenetic role emerges from experimental models. COX-1 and COX-2 isoforms seem to operate in a coordinate manner in cancer pathophysiology, especially in the tumorigenesis process. However, in some cases, exemplified by the serous ovarian carcinoma, COX-1 plays a pivotal role, suggesting that other histopathological and molecular subtypes of cancer disease could share this feature. Importantly, the analysis of functional implications of COX-1-signaling, as well as of pharmacological action of COX-1-selective inhibitors, should not be restricted to the COX pathway and to the effects of prostaglandins already known for their ability of affecting the tumor phenotype. A knowledge-based choice of the most appropriate tumor cell models, and a major effort in investigating the COX-1 issue in the more general context of arachidonic acid metabolic network by using the systems biology approaches, should be strongly encouraged.

A low carbohydrate, high protein diet combined with celecoxib markedly reduces metastasis

We recently demonstrated that both murine and human carcinomas grow significantly slower in mice on low carbohydrate (CHO), high protein diets than on isocaloric Western diets and that a further reduction in tumor growth rates occur when the low CHO diets are combined with the cyclooxygenase-2 inhibitor, celecoxib. Following upon these studies, we asked herein what effect low CHO, high protein diets, with or without celecoxib, might have on tumor metastasis. In the highly metastatic 4T1 mouse mammary tumor model, a 15% CHO, high protein diet supplemented with celecoxib (1 g/kg chow) markedly reduced lung metastases. Moreover, in longer-term studies using male Transgenic Adenocarcinoma of the Mouse Prostate mice, which are predisposed to metastatic prostate cancer, the 15% CHO diet, with and without celecoxib (0.3 g/kg chow), gave the lowest incidence of metastases, but a more moderate 25% CHO diet containing celecoxib led to the best survival. Metabolic studies with 4T1 tumors suggested that the low CHO, high protein diets may be forcing tumors to become dependent on amino acid catabolism for survival/growth. Taken together, our results suggest that a combination of a low CHO, high protein diet with celecoxib substantially reduces metastasis.

Celecoxib decreases growth and angiogenesis and promotes apoptosis in a tumor cell line resistant to chemotherapy

BACKGROUND

During the last few years it has been shown in several laboratories that Celecoxib (Cx), a non-steroidal anti-inflammatory agent (NSAID) normally used for pain and arthritis, mediates antitumor and antiangiogenic effects. However, the effects of this drug on a tumor cell line resistant to chemotherapeutical drugs used in cancer have not been described.

RESULTS

Cx reduces angiogenesis in the chick embryonic chorioallantoic membrane assay (CAM), inhibits the growth and microvascular density of the murine TA3-MTXR tumor, reduces microvascular density of tumor metastases, promotes apoptosis and reduces vascular endothelial growth factor (VEGF) production and cell proliferation in the tumor.

CONCLUSION

The antiangiogenic and antitumor Cx effects correlate with its activity on other tumor cell lines, suggesting that Prostaglandins (PGs) and VEGF production are involved. These results open the possibility of using Celecoxib combined with other experimental therapies, ideally aiming to get synergic effects.

Selective cyclooxygenase inhibitors increase paclitaxel sensitivity in taxane-resistant ovarian cancer by suppressing P-glycoprotein expression

Objective

The purpose of this study was to investigate whether selective cyclooxygenase (COX) inhibitors promote paclitaxel-induced apoptosis in taxane-resistant ovarian cancer cells by suppressing MDR1/P-glycoprotein (P-gp) expression.

Methods

Taxane-resistant ovarian cancer cells were cultured with paclitaxel alone or combined with a selective COX inhibitors. The expression patterns of MDR1/P-gp and the ability of COX inhibitors to inhibit growth of taxane-resistant ovarian cancer cells were measured. The efficacy of prostaglandin E₂ (PGE₂) supplementation was measured to evaluate the mechanisms involved in suppressing MDR1 gene expression.

Results

P-gp was upregulated in taxane-resistant ovarian cancer cells compared to paired paclitaxel-sensitive ovarian cancer cells. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that selective COX inhibitors significantly enhanced the cytotoxic effects of paclitaxel in taxane-resistant ovarian cancer cells via a prostaglandin-independent mechanism. These increased apoptotic effects were further verified by measuring an increased percentage of cells in sub-G1 stage using flow cytometry. Selective COX inhibitors suppressed MDR1 and P-gp expression. Moreover, combined treatment with paclitaxel and selective COX inhibitors increased poly (ADP-ribose) polymerase (PARP) cleavage in taxane-resistant ovarian cancer cells.

Conclusion

Selective COX inhibitors significantly promote paclitaxel-induced cell death in taxane-resistant ovarian cancer cells in a prostaglandin-independent manner. COX inhibitors could be potent therapeutic tools to promote paclitaxel sensitization of taxane-resistant ovarian cancers by suppressing MDR1/P-gp, which is responsible for the efflux of chemotherapeutic agents.