Phytochemicals in Cancer Prevention and Therapy

Despite advances in modern medicine, cancer is still the major cause of mortality in both developing and developed countries. Search for safer and more effective chemoprevention and treatment strategy is a need for the improvement of patient care in the field. Prevention may be more effective and less costly because cancer is largely a preventable disease which could be attributed to a greater extent to lifestyle. Dietary phytochemicals have been used for the treatment of cancer throughout history due to their safety, low toxicity, and general availability. Population based studies suggest that a reduced risk of cancer is associated with high consumption of vegetables and fruits. Promising phytochemicals not only disrupt aberrant signaling pathways leading to cancer but also synergize with chemotherapy and radiotherapy. Thus, the cancer chemoprevention and therapeutic potential of naturally occurring phytochemicals are of great interest. In this special issue we have collected many interesting original research articles and reviews that provide solid evidence to support the application of phytochemicals or dietary agents in prevention and treatment of cancer

Plumbagin inhibits invasion and migration of breast and gastric cancer cells by downregulating the expression of chemokine receptor CXCR4

<p>Abstract</p> <p>Background</p> <p>Increasing evidence indicates that the interaction between the CXC chemokine receptor-4 (CXCR4) and its ligand CXCL12 is critical in the process of metastasis that accounts for more than 90% of cancer-related deaths. Thus, novel agents that can downregulate the CXCR4/CXCL12 axis have therapeutic potential in inhibiting cancer metastasis.</p> <p>Methods</p> <p>In this report, we investigated the potential of an agent, plumbagin (5-hydroxy-2-methyl-1, 4-naphthoquinone), for its ability to modulate CXCR4 expression and function in various tumor cells using Western blot analysis, DNA binding assay, transient transfection, real time PCR analysis, chromatin immunoprecipitation, and cellular migration and invasion assays.</p> <p>Results</p> <p>We found that plumbagin downregulated the expression of CXCR4 in breast cancer cells irrespective of their HER2 status. The decrease in CXCR4 expression induced by plumbagin was not cell type-specific as the inhibition also occurred in gastric, lung, renal, oral, and hepatocellular tumor cell lines. Neither proteasome inhibition nor lysosomal stabilization had any effect on plumbagin-induced decrease in CXCR4 expression. Detailed study of the underlying molecular mechanism(s) revealed that the regulation of the downregulation of CXCR4 was at the transcriptional level, as indicated by downregulation of mRNA expression, inhibition of NF-κB activation, and suppression of chromatin immunoprecipitation activity. In addition, using a virtual, predictive, functional proteomics-based tumor pathway platform, we tested the hypothesis that NF-κB inhibition by plumbagin causes the decrease in CXCR4 and other metastatic genes. Suppression of CXCR4 expression by plumbagin was found to correlate with the inhibition of CXCL12-induced migration and invasion of both breast and gastric cancer cells.</p> <p>Conclusions</p> <p>Overall, our results indicate, for the first time, that plumbagin is a novel blocker of CXCR4 expression and thus has the potential to suppress metastasis of cancer.</p

Emodin Suppresses Migration and Invasion through the Modulation of CXCR4 Expression in an Orthotopic Model of Human Hepatocellular Carcinoma

10.1371/journal.pone.0057015PLoS ONE83

p21cip1/waf1 Coordinates Autophagy, Proliferation and Apoptosis in Response to Metabolic Stress

Cancer cells possess metabolic properties that are different from benign cells. These unique characteristics have become attractive targets that are being actively investigated for cancer therapy. p21cip1/waf1, also known as Cyclin-Dependent Kinase inhibitor 1A, is encoded by the CDKN1A gene. It is a major p53 target gene involved in cell cycle progression that has been extensively evaluated. To date, p21 has been reported to regulate various cell functions, both dependent and independent of p53. Besides regulating the cell cycle, p21 also modulates apoptosis, induces senescence, and maintains cellular quiescence in response to various stimuli. p21 transcription is induced in response to stresses, including those from oxidative and chemotherapeutic treatment. A recent study has shown that in response to metabolic stresses such as nutrient and energy depletion, p21 expression is induced to regulate various cell functions. Despite the biological significance, the mechanism of p21 regulation in cancer adaptation to metabolic stress is underexplored and thus represents an exciting field. This review focuses on the recent development of p21 regulation in response to metabolic stress and its impact in inducing cell cycle arrest and death in cancer cells

γ-Tocotrienol is a novel inhibitor of constitutive and inducible STAT3 signalling pathway in human hepatocellular carcinoma: potential role as an antiproliferative, pro-apoptotic and chemosensitizing agent

10.1111/j.1476-5381.2010.01187.xBritish Journal of Pharmacology1632283-298BJPC

First evidence that γ-tocotrienol inhibits the growth of human gastric cancer and chemosensitizes it to capecitabine in a xenograft mouse model through the modulation of NF-κB pathway

10.1158/1078-0432.CCR-11-2470Clinical Cancer Research1882220-2229CCRE

Emodin suppresses migration and invasion of HepG2 cells.

<p>A, Wound-healing assay was performed for evaluating the inhibitory effect of emodin on HepG2 cell migration. Confluent monolayers of HepG2 cells were scarred, and repair was monitored microscopically after 12 h of pre-treatment with emodin (50 µM) before being exposed to 100ng/mL CXCL12 for 24 h. Width of wound was measured at time zero and 24 h of incubation with and without emodin in the absence or presence of CXCL12. The representative photographs showed the same area at time zero and after 24 h of incubation. B, HepG2 (2×10⁵ cells) were seeded in the top-chamber of the Matrigel. After pre-incubation with or without emodin (50 µM) for 12 h, transwell chambers were then placed into the wells of a 24-well plate, in which we had added either the basal medium only or basal medium containing 100 ng/mL CXCL12 for 24 h. After incubation, they were assessed for cell invasion as described in Materials and Methods. Columns represent percentage of invaded cells; bars, S.E. *indicates p value <0.05. Representative results of two independent experiments are shown.</p