ABSTRACT
BACKGROUND: Novel therapeutic agents that selectively induce tumor cell death are urgently needed in the clinical management of cancers. Such agents would constitute effective adjuvant approaches to traditional chemotherapy regimens. Organosulfur compounds (OSCs), such as diallyl disulfide, have demonstrated anti-proliferative effects on cancer cells. We have previously shown that synthesized relatives of dysoxysulfone, a natural OSC derived from the Fijian medicinal plant, Dysoxylum richi, possess tumor-specific antiproliferative effects and are thus promising lead candidates. METHODS: Because our structure-activity analyses showed that regions flanking the disulfide bond mediated specificity, we synthesized 18 novel OSCs by structural modification of the most promising dysoxysulfone derivatives. These compounds were tested for anti-proliferative and apoptotic activity in both normal and leukemic cells. RESULTS: Six OSCs exhibited tumor-specific killing, having no effect on normal bone marrow, and are thus candidates for future toxicity studies. We then employed mRNA expression profiling to characterize the mechanisms by which different OSCs induce apoptosis. Using Gene Ontology analysis we show that each OSC altered a unique set of pathways, and that these differences could be partially rationalized from a transcription factor binding site analysis. For example, five compounds altered genes with a large enrichment of p53 binding sites in their promoter regions (p < 0.0001). CONCLUSIONS: Taken together, these data establish OSCs derivatized from dysoxysulfone as a novel group of compounds for development as anti-cancer agents.
Subject(s)
Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Disulfides/pharmacology , Leukemia/pathology , Sulfones/pharmacology , Antineoplastic Agents/chemical synthesis , Binding Sites , Cell Cycle/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Disulfides/chemical synthesis , Dose-Response Relationship, Drug , Gene Expression Profiling , Gene Expression Regulation, Leukemic/drug effects , Humans , Leukemia/genetics , Molecular Structure , Myeloid Progenitor Cells/drug effects , Promoter Regions, Genetic/drug effects , RNA, Messenger/metabolism , Structure-Activity Relationship , Sulfones/chemical synthesisABSTRACT
The purpose of this work is to develop agents for cancer differentiation therapy. We showed that five antiproliferative quinoline compounds in the National Cancer Institute database stimulated cell differentiation at growth inhibitory concentrations (3-14 microM) in MCF-7 human breast tumor cells in vitro. The differentiation-inducing quinolines caused lipid droplet accumulation, a phenotypic marker of differentiation, loss of Ki67 antigen expression, a cell cycle marker indicative of exit into G0, and reduced protein levels of the G1--S transcription factor, E2F1. The antimalarial quinolines, chloroquine, hydroxychloroquine and quinidine had similar effects in MCF-7 cells, but were 3-10 times less potent than the NSC compounds. NSC3852 and NSC86371 inhibited histone deacetylase (HDAC) activity in vitro and caused DNA damage and apoptosis in MCF-7 cells, consistent with their differentiation and antiproliferative activities. However, the HDAC assay results showed that for other compounds, direct HDAC enzyme inhibition was not required for differentiation activity. E2F1 protein was suppressed by all differentiation quinolines, but not by non-differentiating analogs, quinoline and primaquine. At equivalent antiproliferative concentrations, NSC69603 caused the greatest decrease in E2F1 protein (90%) followed by antimalarials quinidine and hydroxychloroquine. NSC69603 did not cause DNA damage. The other NSC compounds caused DNA damage and apoptosis and reduced E2F1 levels. The physicochemical properties of NSC3852, NSC69603, NSC86371, and NSC305819 predicted they are drug candidates suitable for development as experimental breast tumor cell differentiation agents. We conclude DNA damage and reductions in E2F1 protein are mechanistically important to the differentiation and antiproliferative activities of these quinoline drug candidates.
Subject(s)
Antineoplastic Agents/pharmacology , Cell Differentiation/drug effects , Quinolines/pharmacology , Breast Neoplasms/pathology , Cell Cycle Proteins/metabolism , Cell Death/drug effects , Cell Death/physiology , Cell Differentiation/physiology , Cell Proliferation/drug effects , DNA-Binding Proteins/metabolism , E2F Transcription Factors , E2F1 Transcription Factor , HeLa Cells , Histone Deacetylases/metabolism , Humans , Transcription Factors/metabolism , Tumor Cells, CulturedABSTRACT
Quinidine regulates growth and differentiation in human breast tumor cells, but the immortalized mammary epithelial MCF-10A cell line is insensitive to quinidine. We found that a morphologically similar differentiation response was evoked by quinidine and c-myc antisense oligonucleotides in MCF-7 cells and this prompted us to investigate the actions of quinidine on c-myc gene expression. Myc protein levels were suppressed in human breast tumor cell lines, but not in MCF-10A cells, an observation that supports the hypothesis that suppression of c-myc gene expression is involved in the preferential growth and differentiation response of breast tumor cells to quinidine. Quinidine reduced c-myc mRNA levels in MCF-7 cells. Acute induction of c-myc mRNA by estradiol, as well as the c-myc response to sub-cultivation in fresh serum and H-ras driven elevations in c-myc mRNA were depressed by 50-60% in the presence of quinidine. Quinidine decreased c-myc promoter activity in MCF-7 cells in a transient reporter gene assay and a 168 bp region of human c-myc promoter (-100 to +68 with respect to the P1 promoter) was sufficient to confer responsiveness to quinidine. Quinidine is a potential lead compound for developing pharmacological agents to regulate Myc. In addition, the study of quinidine-regulated events is a promising approach to unravel differentiation control pathways that become disrupted in breast cancer.
