Dihydrotanshinone-I and Adenocarcinoma

15,16-Dihydrotanshinone I (DHTS) is a component of the traditional Chinese medicinal plant Salvia miltiorrhiza Bunge. In this study, DHTS at as low as 2.5 μg/ml concentration significantly inhibited proliferation of human benign (SW480) and malignant (SW620) colorectal cancer cells, as shown by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-diphenytetrazoliumromide (MTT) and flow cytometric analysis. Activating transcription factor (ATF)-3, a basic leucine zipper-type transcription factor, was found to be predominantly up-regulated in DHTS-treated SW480 and SW620 cells. The up-regulation of ATF3 was blocked by a c-JUN N-terminal kinase (JNK) or p38 inhibitor. Overexpression of ATF3 resulted in a significant augmentation of DHTS-induced apoptosis of SW480 cells, but resistance to DHTS-induced apoptosis of SW620 cells. These results suggest that DHTS has a strong therapeutic or preventive potential against cancer. In addition, ATF3 has a dual role in DHTS-induced apoptosis, depending on the degree of malignancy of colorectal cancer.

Topics: Activating Transcription Factor 3; Adenocarcinoma; Apoptosis; Cell Line, Tumor; Cell Proliferation; Cell Survival; Colorectal Neoplasms; Drug Screening Assays, Antitumor; Furans; Humans; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; Neoplasm Metastasis; Phenanthrenes; Phosphorylation; Quinones

Chemotherapeutic drugs are usually designed to induce cancer cell death via cell cycle arrest and/or apoptosis pathways. In this study, we used the chemical drug 15,16-dihydrotanshinone I (DHTS) to inhibit breast cancer cell proliferation and tumor growth, and investigate the underlying molecular mechanisms. Human breast cancer cell lines MCF-7 and MDA-MB-231 were both used in this study, and DHTS was found to significantly decrease cell proliferation by a dose-dependent manner in both cells. Flow cytometry indicated that DHTS induced G1 phase arrest in synchronous MCF-7 and MDA-MB-231 cells. When analyzing the expression of cell cycle-related proteins, we found that DHTS reduced cyclin D1, cyclin D3, cyclin E, and CDK4 expression, and increased CDK inhibitor p27 expression in a dose-dependent manner. In addition, DHTS inhibited the kinase activities of CDK2 and CDK4 by an immunocomplex kinase assay. In addition, DHTS also induced apoptosis in both cells through mainly mitochondrial apoptosis pathways. We found that DHTS decreased the anti-apoptotic protein Bcl-xL level and increased the loss of mitochondria membrane potential and the amount of cytochrome c released. Moreover, DHTS activated caspase-9, caspase-3, and caspase-7 and caused cell apoptosis. The fact that DHTS-induced apoptosis could be blocked by pretreating cells with pan-caspase inhibitor confirmed that it is mediated through activation of the caspase-3-dependent pathway. In a nude mice xenograft experiment, DHTS significantly inhibited the tumor growth of MDA-MB-231 cells. Taken together, these results suggest that DHTS can inhibit human breast cancer cell proliferation and tumor growth, and might have potential chemotherapeutic applications.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Apoptosis; bcl-X Protein; Breast Neoplasms; Caspase 9; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase Inhibitor p27; Cytochromes c; Furans; G1 Phase; Humans; Male; Mammary Neoplasms, Experimental; Membrane Potential, Mitochondrial; Mice; Mice, Inbred BALB C; Mice, Nude; Molecular Structure; Phenanthrenes; Quinones; Xenograft Model Antitumor Assays