ABSTRACT
Liver cancer is one of the leading causes of cancer death worldwide. A very high incidence of new liver cancer cases is diagnosed every year, and metastasis has been found to correlate to poor prognoses in humans. Better treatments for liver cancer are thus clearly needed. Sinigrin is one of the major ingredients present in Brassica nigra, which has been used in combination with other herbs for treatment of various diseases. The anti-proliferative activities of sinigrin were studied in a model of carcinogen-induced hepatotoxicity in rats. Rats were orally administered with sinigrin on a daily basis for three months before sacrifice. Sinigrin was found to significantly inhibit the proliferation of liver tumor cells; the number of surface tumors in the rat liver was dramatically reduced. Sinigrin induced apoptosis of liver cancer cells through up-regulation of p53 and down-regulation of Bcl-2 family members and caspases. Our findings indicated that the liver functions were gradually restored after treatment with sinigrin and that the agent did not cause liver toxicity. Cell cycle analysis indicated that sinigrin caused cell cycle arrest in G0/G1 phase. The results suggest that sinigrin exerts important anti-proliferative activities in carcinogen-induced hepatocarcinogenesis in rats, and highlight the potential of sinigrin as an anti-cancer agent for liver cancer.
Subject(s)
Antineoplastic Agents/pharmacology , Carcinogens/toxicity , Glucosinolates/pharmacology , Liver Neoplasms/pathology , Liver/drug effects , Animals , Cell Line, Tumor , Cell Proliferation/drug effects , G1 Phase Cell Cycle Checkpoints/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Humans , Liver/metabolism , Liver/pathology , Liver Neoplasms/chemically induced , Liver Neoplasms/genetics , Male , Proto-Oncogene Proteins c-mdm2/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Rats, Sprague-Dawley , Resting Phase, Cell Cycle/drug effects , Tumor Suppressor Protein p53/genetics , Xenograft Model Antitumor AssaysABSTRACT
Newer treatments of advanced human cancer are based on combination of cancer drugs that have different mechanism of actions yet the combination strategy may potentiate the anti-cancer effects and cytotoxicity. Recent studies suggest that cancer growth can be inhibited more effectively by combination of phytochemicals that affect different pathways. The apoptotic activity can be modulated by intrinsic and extrinsic molecules. The combination of anti-tumor phytochemicals can be more effective in modulating different signaling pathways associated with tumor cell growth which is the common target for anti-tumor action. Combinations of cytotoxic anti-tumor agents and inhibitors from phytochemicals are believed to act together producing inhibitory mechanisms on cancer growth. This combination strategy shows promise on cancer therapy. However, the combination of phytochemicals in cancer therapy needs to be further investigated to develop a better treatment strategy. Recent patents on anti-tumor phytochemicals are reviewed in this article.
Subject(s)
Antineoplastic Agents, Phytogenic/therapeutic use , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Chemotherapy, Adjuvant/methods , Neoplasms/drug therapy , Plants/chemistry , Antineoplastic Agents, Phytogenic/administration & dosage , Biological Products , Humans , Patents as TopicABSTRACT
Alkaline exonuclease and single-strand DNA (ssDNA) annealing proteins (SSAPs) are key components of DNA recombination and repair systems within many prokaryotes, bacteriophages and virus-like genetic elements. The recently sequenced ß-proteobacterium Laribacter hongkongensis (strain HLHK9) encodes putative homologs of alkaline exonuclease (LHK-Exo) and SSAP (LHK-Bet) proteins on its 3.17 Mb genome. Here, we report the biophysical, biochemical and structural characterization of recombinant LHK-Exo protein. LHK-Exo digests linear double-stranded DNA molecules from their 5'-termini in a highly processive manner. Exonuclease activities are optimum at pH 8.2 and essentially require Mg(2+) or Mn(2+) ions. 5'-phosphorylated DNA substrates are preferred over dephosphorylated ones. The crystal structure of LHK-Exo was resolved to 1.9 Å, revealing a 'doughnut-shaped' toroidal trimeric arrangement with a central tapered channel, analogous to that of λ-exonuclease (Exo) from bacteriophage-λ. Active sites containing two bound Mg(2+) ions on each of the three monomers were located in clefts exposed to this central channel. Crystal structures of LHK-Exo in complex with dAMP and ssDNA were determined to elucidate the structural basis for substrate recognition and binding. Through structure-guided mutational analysis, we discuss the roles played by various active site residues. A conserved two metal ion catalytic mechanism is proposed for this class of alkaline exonucleases.
