The role of signal transduction in cancer treatment and drug resistance

Bioinformatics and In silico approaches to identify novel biomarkers and key pathways for cancers that are linked to the progression of female infertility: A comprehensive approach for drug discovery

Despite modern treatment, infertility remains one of the most common gynecologic diseases causing severe health effects worldwide. The clinical and epidemiological data have shown that several cancerous risk factors are strongly linked to Female Infertility (FI) development, but the exact causes remain unknown. Understanding how these risk factors affect FI-affected cell pathways might pave the door for the discovery of critical signaling pathways and hub proteins that may be targeted for therapeutic intervention. To deal with this, we have used a bioinformatics pipeline to build a transcriptome study of FI with four carcinogenic risk factors: Endometrial Cancer (EC), Ovarian Cancer (OC), Cervical Cancer (CC), and Thyroid Cancer (TC). We identified FI sharing 97, 211, 87 and 33 differentially expressed genes (DEGs) with EC, OC, CC, and TC, respectively. We have built gene-disease association networks from the identified genes based on the multilayer network and neighbour-based benchmarking. Identified TNF signalling pathways, ovarian infertility genes, cholesterol metabolic process, and cellular response to cytokine stimulus were significant molecular and GO pathways, both of which improved our understanding the fundamental molecular mechanisms of cancers associated with FI progression. For therapeutic intervention, we have targeted the two most significant hub proteins VEGFA and PIK3R1, out of ten proteins based on Maximal Clique Centrality (MCC) value of cytoscape and literature analysis for molecular docking with 27 phytoestrogenic compounds. Among them, sesamin, galangin and coumestrol showed the highest binding affinity for VEGFA and PIK3R1 proteins together with favourable ADMET properties. We recommended that our identified pathway, hub proteins and phytocompounds may be served as new targets and therapeutic interventions for accurate diagnosis and treatment of multiple diseases.

The Combination of Omega-3 Stearidonic Acid and Docetaxel Enhances Cell Death over Docetaxel Alone in Human Prostate Cancer Cells

Background: Docetaxel (DOC), or Taxotere, is an anthracycline antibiotic used to treat multiple types of cancer. It is a first-line chemotherapy treatment for patients with metastasized, hormone-resistant prostate cancer (PCa) or for patients with high-risk, localized PCa that could benefit from early chemotherapy treatment. Previously, we showed that stearidonic acid (SDA), an omega-3 fatty acid, enhances the cytotoxicity of doxorubicin (DOX) in human PCa cells. This observation suggests that PCa therapies using SDA and chemotherapeutic drugs in combination offer attractive possibilities for developing treatments that ameliorate toxic side effects of some commonly used chemotherapy drugs.

Objectives: We used androgen-resistant PC3 and DU 145 cells derived from human prostate cancer to quantify the effects of combined SDA and DOC on proliferation/viability and on the production of pro-apoptotic caspases 9 and 3. We also compared the effects of SDA with those of BAY, a pharmacological inhibitor of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB), in androgen-sensitive LNCaP cells. Finally, we qualitatively and quantitatively assessed the drug combination on androgen receptor (AR) and peroxisome proliferator-activated receptor gamma (PPARγ) expression in LNCaP and PC3 cells, respectively.

Methods: The half maximal inhibitory concentration (IC50) and combination indices of SDA and DOC in PC3 and DU 145 cells were determined using the MTT cell viability assay. To quantify the effects of SDA and BAY on NF-ĸB activity, we used luciferase reporter assays in LNCaP cells that were stably transduced with lentiviral vectors carrying NF-ĸB response element sequence upstream of the luciferase gene sequence. AR and PPARγ expression were assessed by western blotting and immunocytochemistry. We considered caspase 9 and 3 cleavage to be apoptosis markers and determined the drug combination effect on the extent of that cleavage by western blot analysis.

Results: The cytotoxic effects of DOC were synergistically enhanced by SDA when the two were added to DU145 and PC3 cell cultures. Combination index (CI) analyses based on the Chou-Talalay method and mass action law showed synergistic interaction with CI <1. SDA suppressed TNFα-induced NF-κB activity similarly to BAY. The SDA/DOC combination down regulated testosterone (T)-induced AR and troglitazone-induced PPARγ protein expression when compared to using the drugs singly. Similarly, the SDA/DOC combination induced caspase 9 and 3 production and cleavage suggesting apoptosis induction. Like our DOX studies, this work provides proof-of-concept for using SDA and DOC in combination to reduce the dose, and therefore the toxicity, of DOC and possibly increasing the survival benefit in DOC clinical translation studies.

Diallyl sulfide, diallyl disulfide and diallyl trisulfide affect drug resistant gene expression in colo 205 human colon cancer cells in vitro and in vivo

To elevate chemo-resistance of human cancer cells is a major obstacle in the treatment and management of malignant cancers. Diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS) are presented in the Alliaceae family particularly in garlic. Although DAS, DADS and DATS have been shown to exhibit anticancer activities, there is little information on effects of these compounds on drug resistant genes in human colon cancer cells in vitro and in vivo. Herein, we are the first to show that DAS, DADS and DATS at 25 μM for 24-h and 48-h incubations promoted expression of drug resistant genes in colo 205 human colon cancer cells. In vitro experiments indicated that DATS promoted gene expression of multidrug resistant 1 (Mdr1) (p<0.05), and DAS and DADS promoted MRP3 gene expression and DATS alone stimulated gene expression of multidrug resistance-associated protein-1 (MRP1) (p<0.05) in colo 205 cells. In vivo studies demonstrated that DADS and DATS induced Mdr1 and MRP1 gene expression (p<0.05). DADS promoted MRP3 gene expression (p<0.05) as well as DADS and DATS increased MRP4 and MRP6 gene expression (p<0.05) in the colo 205 xenograft mice. Based on our in vitro and in vivo results, diallyl polysulfides (DAS, DADS and DATS) affected the gene expression of the multidrug resistance in colo 205 human colon cancer cells in vitro and in vivo.

Inhibition of the met receptor tyrosine kinase signaling enhances the chemosensitivity of glioma cell lines to CDDP through activation of p38 MAPK pathway

The Met receptor tyrosine kinase is known to be overexpressed in many solid tumors and plays a crucial role in tumor invasive growth and metastasis. In this study, we showed that hepatocyte growth factor-induced Met activation as well as Met-dependent downstream signaling of AKT and p44/42 mitogen-activated protein kinase (MAPK) could be efficiently blocked by TAT-coupled carboxyl-terminal tail peptide of Met receptor (TCTP), and inactivation of Met signaling significantly enhanced the sensitivity of T98G and U251 glioma cells to cis-diaminedichloroplatinum (CDDP, cisplatin). However, neither phosphoinositide 3-kinase/AKT inhibitor LY294002 nor p44/42 MAPK inhibitor PD98059 alone or combined could imitate the effect of TCTP on chemosensitivity enhancement of T98G cells to CDDP, indicating that Met-dependent inactivation of AKT and p44/42 MAPK signaling was not the main cause for the increased chemosensitivity to CDDP. Further studies revealed that TCTP significantly activated p38 MAPK in T98G and U251 cell lines. Activation of p38 MAPK by sorbitol pretreatment resembled the sensitization effects, whereas inhibition of p38 MAPK activation by its inhibitor SB202190 counteracted the sensitization effects induced by TCTP. Therefore, p38 MAPK activation was one of the major causes for the increased chemosensitivity to CDDP induced by Met inactivation. Taken together, the study indicated that Met receptor played an important role in regulating cell response to chemotherapy and suggested that inhibition of Met signaling could be used in combination with other chemotherapeutic regimens in treatment of tumor patients.

Chemosensitization of tumor cells: inactivation of nuclear factor-kappa B associated with chemosensitivity in melanoma cells after combination treatment with E2F-1 and doxorubicin

Combination chemotherapy has been shown to be more effective than single-agent therapy for many types of cancer, but both are known to induce drug resistance in cancer cells. Two major culprits in the development of this drug resistance are nuclear factor-kappaB (NF-kappaB) and the multidrug resistance (MDR) gene. For this reason, chemogene therapy is emerging as a viable alternative to conventional chemotherapy combinations. We have shown that transduction of the E2F-1 gene in melanoma cells markedly increases cell sensitivity to doxorubicin, thereby producing a synergistic effect on melanoma cell apoptosis. Our microarray results show that the NF-kappaB pathway and related genes undergo significant changes after the combined treatment of E2F-1 and doxorubicin. In fact, inactivation of NF-kappaB is associated with melanoma cell apoptosis induced by E2F-1 and doxorubicin, providing a link between the NF-kappaB signaling pathway and the chemosensitivity of melanoma cells after this treatment.

Alternative signaling pathways: when, where and why?

Alternative cell signal transduction pathways have been demonstrated in some experimental systems. The importance of their existence has not been completely appreciated. In this review we present the cases of alternative pathways resulted from a survey of the available experimental data. The alternative pathways could show different relationships, i.e., synergistic, redundant, additive, opposite and competitive effects. They could have distinct time courses and cell, organ, sex or species specification. Further, they could happen during physiological or pathological situations, and display differentiated sensitivity. These case studies together imply that alternative signal pathways could be involved in the regulation of cell functions at the pathway level. In-depth understanding of the importance of the alternative pathways will rely on building and exploration of mathematical models.

Inactivation of nuclear factor kappaB by soy isoflavone genistein contributes to increased apoptosis induced by chemotherapeutic agents in human cancer cells

Cancer chemotherapeutic strategies commonly require multiple agents. However, use of multiple agents contributes to added toxicity resulting in poor treatment outcome. Thus, combination chemotherapy must be optimized to increase tumor response and at the same time lower its toxicity. Chemotherapeutic agents are known to induce nuclear factor kappaB (NF-kappaB) activity in tumor cells, resulting in lower cell killing and drug resistance. In contrast, genistein has been shown to inhibit the activity of NF-kappaB and the growth of various cancer cells without causing systemic toxicity. We therefore investigated whether the inactivation of NF-kappaB by genistein before treatment of various cancer cells with chemotherapeutic agents could lead to better tumor cell killing as tested by in vitro studies using gene transfections and also by animal studies. PC-3 (prostate), MDA-MB-231 (breast), H460 (lung), and BxPC-3 (pancreas) cancer cells were pretreated with 15 to 30 micromol/L genistein for 24 hours and then exposed to low doses of chemotherapeutic agents for an additional 48 to 72 hours. We found that 15 to 30 micromol/L genistein combined with 100 to 500 nmol/L cisplatin, 0.5 to 2 nmol/L docetaxel, or 50 ng/mL doxorubicin resulted in significantly greater inhibition of cell growth and induction of apoptosis compared with either agent alone. Moreover, we found that the NF-kappaB activity was significantly increased within 2 hours of cisplatin and docetaxel treatment and that the NF-kappaB inducing activity of these agents was completely abrogated in cells pretreated with genistein. These results were also supported, for the first time, by animal experiments, p65 cDNA transfection and p65 small interfering RNA studies, which clearly showed that a specific target (NF-kappaB) was affected in vivo. Collectively, our results clearly suggest that genistein pretreatment inactivates NF-kappaB and may contribute to increased growth inhibition and apoptosis induced by cisplatin, docetaxel, and doxorubicin in prostate, breast, lung, and pancreatic cancer cells. Theses results warrant carefully designed clinical studies investigating the combination of soy isoflavones and commonly used chemotherapeutic agents for the treatment of human cancers.

Circumventing Multidrug Resistance in Cancer by β-Galactoside Binding Protein, an Antiproliferative Cytokine

We report here that beta-galactoside binding protein (betaGBP), an antiproliferative cytokine which can program cancer cells to undergo apoptosis, exhibits equal therapeutic efficacy against cancer cells that display diverse mechanisms of drug resistance and against their parental cells. The mechanisms of drug resistance in the cancer cells that we have examined include overexpression of P-glycoprotein, increased efficiency of DNA repair, and altered expression and mutation in the topoisomerase I and II enzymes. We also report that betaGBP exerted its effect by arresting the cells in S phase prior to the activation of programmed cell death. The uniquely similar profile of response to betaGBP by these drug-resistant cells and their parental cells extends the therapeutic potential of this cytokine in the treatment of cancers and offers a promising alternative to patients whose tumors are refractory to the currently available cadre of chemotherapeutic agents.

Exposure of melanoma cells to dacarbazine results in enhanced tumor growth and metastasis in vivo

PURPOSE

In recent years, the incidence of cutaneous melanoma has increased more than that of any other cancer. Dacarbazine is considered the gold standard for treatment, having a response rate of 15% to 20%, but most responses are not sustained. Previously, we have shown that short exposure of primary cutaneous melanoma cells to dacarbazine resulted in the upregulation of interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The purpose of the present study was to determine how long-term exposure of melanoma cells to dacarbazine would affect their tumorigenic and metastatic potential in vivo.

MATERIALS AND METHODS

The primary cutaneous melanoma cell lines SB2 and MeWo were repeatedly exposed in vitro to increasing concentrations of dacarbazine, and dacarbazine-resistant cell lines SB2-D and MeWo-D were selected and examined for their ability to grow and metastasize in nude mice.

RESULTS

The dacarbazine-resistant cell lines SB2-D and MeWo-D exhibited increased tumor growth and metastatic behavior in vivo. This increase could be explained by the activation of RAF, MEK, and ERK, which led to the upregulation of IL-8 and VEGF. More IL-8, VEGF, matrix metalloproteinase-2 (MMP-2), and microvessel density (CD-31) were found in tumors produced by SB2-D and MeWo-D in vivo than in those produced by their parental counterparts. No mutations were observed in BRAF.

CONCLUSION

Our results have significant clinical implications. Treatment of melanoma patients with dacarbazine could select for a more aggressive melanoma phenotype. We propose that combination treatment with anti-VEGF/IL-8 or MEK inhibitors may potentiate the therapeutic effects of dacarbazine.

Carvedilol: a new candidate for reversal of MDR1/P-glycoprotein-mediated multidrug resistance

In 1983, carvedilol [1-[carbazolyl-(4)-oxy]-3-[(2-methoxyphenoxyethyl)amino]-2-propanol] was designed and developed as a beta-adrenoceptor antagonist with vasodilating activity for efficacious and safe treatment of hypertension and coronary artery disease. Carvedilol belongs to the 'third generation' of beta-adrenoceptor antagonists and shows selectivity for the beta1- rather than beta2-adrenoceptor. Carvedilol is also an alpha1-blocking agents, with around 2- to 3-fold more selectivity for beta1- than alpha1-adrenoceptors. This degree of alpha1-blockade is responsible for the moderate vasodilator properties of carvedilol, being different from other beta-adrenoceptor antagonists. In addition, carvedilol is a potent antioxidant, with a 10-fold greater activity than vitamin E. Some carvedilol metabolites found in human plasma also exhibit antioxidative activity approximately 50- to 100-fold greater than carvedilol and other antioxidants. These unique properties of carvedilol, i.e. adrenergic (beta1, beta2 and alpha1) blockade and antioxidative activity, may be important in preventing progressive deterioration of left ventricular dysfunction and chronic heart failure. Recently, carvedilol has been demonstrated to reverse multidrug resistance (MDR) to anticancer drugs in tumor cells in vitro and its reversal effects were comparable with verapamil, which has been used in the first clinical trial for the reversal of MDR. This review introduces the reversal activity and usefulness against MDR, as well as an overview of the pharmacological and pharmacokinetic properties, of carvedilol.

Dissecting the molecular mechanisms of human cancer: Translating laboratory advances into clinical practice

There are multiple molecular mechanisms involved in human cancers with many genes involved, complex interactions and a variety of ways to examine them. Some events are already emerging as clinically important; others will turn out to be bystanders. By focussing on key genes, such as p53, the clinical implications of genetic changes and the pathways they link into are becoming apparent. Using the complex methodologies now available allied to disciplines such as mathematics we are improving our understanding of malignancy. This is beginning to impact on the management of patients with cancer; meanwhile, a good surgical operation performed timeously is still the best chance a patient has of a cure for most types of solid cancers.

Doxorubicin and vinorelbine act independently via p53 expression and p38 activation respectively in breast cancer cell lines

In the treatment of breast cancer, combination chemotherapy is used to overcome drug resistance. Combining doxorubicin and vinorelbine in the treatment of patients with metastatic breast cancer has shown high response rates; even single-agent vinorelbine in patients previously exposed to anthracyclines results in significant remission. Alterations in protein kinase-mediated signal transduction and p53 mutations may play a role in drug resistance with cross-talk between signal transduction and p53 pathways. The aim of this study was to establish the effects of doxorubicin and vinorelbine, as single agents, in combination, and as sequential treatments, on signal transduction and p53 in the breast cancer cell lines MCF-7 and MDA-MB-468. In both cell lines, increased p38 activity was demonstrated following vinorelbine but not doxorubicin treatment, whether vinorelbine was given prior to or simultaneously with doxorubicin. Mitogen-activated protein kinase (MAPK) activity and p53 expression remained unchanged following vinorelbine treatment. Doxorubicin treatment resulted in increased p53 expression, without changes in MAPK or p38 activity. These findings suggest that the effect of doxorubicin and vinorelbine used in combination may be achieved at least in part through distinct mechanisms. This additivism, where doxorubicin acts via p53 expression and vinorelbine through p38 activation, may contribute to the high clinical response rate when the two drugs are used together in the treatment of breast cancer.